docs: add recovery operators and multi-operator details

Reviewed-on: #45

.claude/memory/feedback_widget_decomposition.md

@@ -0,0 +1,11 @@
+---
+name: Widget decomposition and provider subscriptions
+description: Prefer splitting screens into multiple focused files/widgets; each widget subscribes to its own relevant providers
+type: feedback
+---
+
+Split screens into multiple smaller widgets across multiple files. Each widget should subscribe only to the providers it needs (`ref.watch` at lowest possible level), rather than having one large screen widget that watches everything and passes data down as parameters.
+
+**Why:** Reduces unnecessary rebuilds; improves readability; each file has one clear responsibility.
+
+**How to apply:** When building a new screen, identify which sub-widgets need their own provider subscriptions and extract them into separate files (e.g., `widgets/grant_card.dart` watches enrichment providers itself, rather than the screen doing it and passing resolved strings down).

.gitignore

@@ -1 +1,6 @@
-target/
+target/
+scripts/__pycache__/
+.DS_Store
+.cargo/config.toml
+.vscode/
+docs/

.vscode/settings.json

@@ -1,3 +0,0 @@
-{
-    "git.enabled": false
-}

.woodpecker/server-lint.yaml

@@ -22,4 +22,4 @@ steps:
       - apt-get update && apt-get install -y pkg-config
       - mise install rust 
       - mise install protoc
-      - mise exec rust -- cargo clippy --all-targets --all-features -- -D warnings
+      - mise exec rust -- cargo clippy --all -- -D warnings

.woodpecker/server-test.yaml

@@ -24,4 +24,4 @@ steps:
       - mise install rust 
       - mise install protoc
       - mise install cargo:cargo-nextest
-      - mise exec cargo:cargo-nextest -- cargo nextest run --no-fail-fast
+      - mise exec cargo:cargo-nextest -- cargo nextest run --no-fail-fast --all-features

.woodpecker/useragent-analyze.yaml

@@ -0,0 +1,18 @@
+when:
+  - event: pull_request
+    path:
+      include: ['.woodpecker/useragent-*.yaml', 'useragent/**']
+  - event: push
+    branch: main
+    path:
+      include: ['.woodpecker/useragent-*.yaml', 'useragent/**']
+
+steps:
+  - name: analyze
+    image: jdxcode/mise:latest
+    commands:
+      - mise install flutter 
+      - mise install protoc
+      # Reruns codegen to catch protocol drift
+      - mise codegen 
+      - cd useragent/ && flutter analyze

AGENTS.md

@@ -0,0 +1,128 @@
+# AGENTS.md
+
+This file provides guidance to Codex (Codex.ai/code) when working with code in this repository.
+
+## Project Overview
+
+Arbiter is a **permissioned signing service** for cryptocurrency wallets. It consists of:
+- **`server/`** — Rust gRPC daemon that holds encrypted keys and enforces policies
+- **`useragent/`** — Flutter desktop app (macOS/Windows) with a Rust backend via Rinf
+- **`protobufs/`** — Protocol Buffer definitions shared between server and client
+
+The vault never exposes key material; it only produces signatures when requests satisfy configured policies.
+
+## Toolchain Setup
+
+Tools are managed via [mise](https://mise.jdx.dev/). Install all required tools:
+```sh
+mise install
+```
+
+Key versions: Rust 1.93.0 (with clippy), Flutter 3.38.9-stable, protoc 29.6, diesel_cli 2.3.6 (sqlite).
+
+## Server (Rust workspace at `server/`)
+
+### Crates
+
+| Crate | Purpose |
+|---|---|
+| `arbiter-proto` | Generated gRPC stubs + protobuf types; compiled from `protobufs/*.proto` via `tonic-prost-build` |
+| `arbiter-server` | Main daemon — actors, DB, EVM policy engine, gRPC service implementation |
+| `arbiter-useragent` | Rust client library for the user agent side of the gRPC protocol |
+| `arbiter-client` | Rust client library for SDK clients |
+
+### Common Commands
+
+```sh
+cd server
+
+# Build
+cargo build
+
+# Run the server daemon
+cargo run -p arbiter-server
+
+# Run all tests (preferred over cargo test)
+cargo nextest run
+
+# Run a single test
+cargo nextest run <test_name>
+
+# Lint
+cargo clippy
+
+# Security audit
+cargo audit
+
+# Check unused dependencies
+cargo shear
+
+# Run snapshot tests and update snapshots
+cargo insta review
+```
+
+### Architecture
+
+The server is actor-based using the **kameo** crate. All long-lived state lives in `GlobalActors`:
+
+- **`Bootstrapper`** — Manages the one-time bootstrap token written to `~/.arbiter/bootstrap_token` on first run.
+- **`KeyHolder`** — Holds the encrypted root key and manages the Sealed/Unsealed vault state machine. On unseal, decrypts the root key into a `memsafe` hardened memory cell.
+- **`FlowCoordinator`** — Coordinates cross-connection flow between user agents and SDK clients.
+- **`EvmActor`** — Handles EVM transaction policy enforcement and signing.
+
+Per-connection actors live under `actors/user_agent/` and `actors/client/`, each with `auth` (challenge-response authentication) and `session` (post-auth operations) sub-modules.
+
+**Database:** SQLite via `diesel-async` + `bb8` connection pool. Schema managed by embedded Diesel migrations in `crates/arbiter-server/migrations/`. DB file lives at `~/.arbiter/arbiter.sqlite`. Tests use a temp-file DB via `db::create_test_pool()`.
+
+**Cryptography:**
+- Authentication: ed25519 (challenge-response, nonce-tracked per peer)
+- Encryption at rest: XChaCha20-Poly1305 (versioned via `scheme` field for transparent migration on unseal)
+- Password KDF: Argon2
+- Unseal transport: X25519 ephemeral key exchange
+- TLS: self-signed certificate (aws-lc-rs backend), fingerprint distributed via `ArbiterUrl`
+
+**Protocol:** gRPC with Protocol Buffers. The `ArbiterUrl` type encodes host, port, CA cert, and bootstrap token into a single shareable string (printed to console on first run).
+
+### Proto Regeneration
+
+When `.proto` files in `protobufs/` change, rebuild to regenerate:
+```sh
+cd server && cargo build -p arbiter-proto
+```
+
+### Database Migrations
+
+```sh
+# Create a new migration
+diesel migration generate <name> --migration-dir crates/arbiter-server/migrations
+
+# Run migrations manually (server also runs them on startup)
+diesel migration run --migration-dir crates/arbiter-server/migrations
+```
+
+## User Agent (Flutter + Rinf at `useragent/`)
+
+The Flutter app uses [Rinf](https://rinf.cunarist.org) to call Rust code. The Rust logic lives in `useragent/native/hub/` as a separate crate that uses `arbiter-useragent` for the gRPC client.
+
+Communication between Dart and Rust uses typed **signals** defined in `useragent/native/hub/src/signals/`. After modifying signal structs, regenerate Dart bindings:
+
+```sh
+cd useragent && rinf gen
+```
+
+### Common Commands
+
+```sh
+cd useragent
+
+# Run the app (macOS or Windows)
+flutter run
+
+# Regenerate Rust↔Dart signal bindings
+rinf gen
+
+# Analyze Dart code
+flutter analyze
+```
+
+The Rinf Rust entry point is `useragent/native/hub/src/lib.rs`. It spawns actors defined in `useragent/native/hub/src/actors/` which handle Dart↔server communication via signals.

ARCHITECTURE.md

@@ -11,6 +11,7 @@ Arbiter distinguishes two kinds of peers:
 
 - **User Agent** — A client application used by the owner to manage the vault (create wallets, approve SDK clients, configure policies).
 - **SDK Client** — A consumer of signing capabilities, typically an automation tool. In the future, this could include a browser-based wallet.
+- **Recovery Operator** — A dormant recovery participant with narrowly scoped authority used only for custody recovery and operator replacement.
 
 ---
 
@@ -42,7 +43,149 @@ There is no bootstrap mechanism for SDK clients. They must be explicitly approve
 
 ---
 
-## 3. Server Identity
+## 3. Multi-Operator Governance
+
+When more than one User Agent is registered, the vault is treated as having multiple operators. In that mode, sensitive actions are governed by voting rather than by a single operator decision.
+
+### 3.1 Voting Rules
+
+Voting is based on the total number of registered operators:
+
+- **1 operator:** no vote is needed; the single operator decides directly.
+- **2 operators:** full consensus is required; both operators must approve.
+- **3 or more operators:** quorum is `floor(N / 2) + 1`.
+
+For a decision to count, the operator's approval or rejection must be signed by that operator's associated key. Unsigned votes, or votes that fail signature verification, are ignored.
+
+Examples:
+
+- **3 operators:** 2 approvals required
+- **4 operators:** 3 approvals required
+
+### 3.2 Actions Requiring a Vote
+
+In multi-operator mode, a successful vote is required for:
+
+- approving new SDK clients
+- granting an SDK client visibility to a wallet
+- approving a one-off transaction
+- approving creation of a persistent grant
+- approving operator replacement
+- approving server updates
+- updating Shamir secret-sharing parameters
+
+### 3.3 Special Rule for Key Rotation
+
+Key rotation always requires full quorum, regardless of the normal voting threshold.
+
+This is stricter than ordinary governance actions because rotating the root key requires every operator to participate in coordinated share refresh/update steps. The root key itself is not redistributed directly, but each operator's share material must be changed consistently.
+
+### 3.4 Root Key Custody
+
+When the vault has multiple operators, the vault root key is protected using Shamir secret sharing.
+
+The vault root key is encrypted in a way that requires reconstruction from user-held shares rather than from a single shared password.
+
+For ordinary operators, the Shamir threshold matches the ordinary governance quorum. For example:
+
+- **2 operators:** `2-of-2`
+- **3 operators:** `2-of-3`
+- **4 operators:** `3-of-4`
+
+In practice, the Shamir share set also includes Recovery Operator shares. This means the effective Shamir parameters are computed over the combined share pool while keeping the same threshold. For example:
+
+- **3 ordinary operators + 2 recovery shares:** `2-of-5`
+
+This ensures that the normal custody threshold follows the ordinary operator quorum, while still allowing dormant recovery shares to exist for break-glass recovery flows.
+
+### 3.5 Recovery Operators
+
+Recovery Operators are a separate peer type from ordinary vault operators.
+
+Their role is intentionally narrow. They can only:
+
+- participate in unsealing the vault
+- vote for operator replacement
+
+Recovery Operators do not participate in routine governance such as approving SDK clients, granting wallet visibility, approving transactions, creating grants, approving server updates, or changing Shamir parameters.
+
+### 3.6 Sleeping and Waking Recovery Operators
+
+By default, Recovery Operators are **sleeping** and do not participate in any active flow.
+
+Any ordinary operator may request that Recovery Operators **wake up**.
+
+Any ordinary operator may also cancel a pending wake-up request.
+
+This creates a dispute window before recovery powers become active. The default wake-up delay is **14 days**.
+
+Recovery Operators are therefore part of the break-glass recovery path rather than the normal operating quorum.
+
+The high-level recovery flow is:
+
+```mermaid
+sequenceDiagram
+    autonumber
+    actor Op as Ordinary Operator
+    participant Server
+    actor Other as Other Operator
+    actor Rec as Recovery Operator
+
+    Op->>Server: Request recovery wake-up
+    Server-->>Op: Wake-up pending
+    Note over Server: Default dispute window: 14 days
+
+    alt Wake-up cancelled during dispute window
+        Other->>Server: Cancel wake-up
+        Server-->>Op: Recovery cancelled
+        Server-->>Rec: Stay sleeping
+    else No cancellation for 14 days
+        Server-->>Rec: Wake up
+        Rec->>Server: Join recovery flow
+        critical Recovery authority
+            Rec->>Server: Participate in unseal
+            Rec->>Server: Vote on operator replacement
+        end
+        Server-->>Op: Recovery mode active
+    end
+```
+
+### 3.7 Committee Formation
+
+There are two ways to form a multi-operator committee:
+
+- convert an existing single-operator vault by adding new operators
+- bootstrap an unbootstrapped vault directly into multi-operator mode
+
+In both cases, committee formation is a coordinated process. Arbiter does not allow multi-operator custody to emerge implicitly from unrelated registrations.
+
+### 3.8 Bootstrapping an Unbootstrapped Vault into Multi-Operator Mode
+
+When an unbootstrapped vault is initialized as a multi-operator vault, the setup proceeds as follows:
+
+1. An operator connects to the unbootstrapped vault using a User Agent and the bootstrap token.
+2. During bootstrap setup, that operator declares:
+   - the total number of ordinary operators
+   - the total number of Recovery Operators
+3. The vault enters **multi-bootstrap mode**.
+4. While in multi-bootstrap mode:
+   - every ordinary operator must connect with a User Agent using the bootstrap token
+   - every Recovery Operator must also connect using the bootstrap token
+   - each participant is registered individually
+   - each participant's share is created and protected with that participant's credentials
+5. The vault is considered fully bootstrapped only after all declared operator and recovery-share registrations have completed successfully.
+
+This means the operator and recovery set is fixed at bootstrap completion time, based on the counts declared when multi-bootstrap mode was entered.
+
+### 3.9 Special Bootstrap Constraint for Two-Operator Vaults
+
+If a vault is declared with exactly **2 ordinary operators**, Arbiter requires at least **1 Recovery Operator** to be configured during bootstrap.
+
+This prevents the worst-case custody failure in which a `2-of-2` operator set becomes permanently unrecoverable after loss of a single operator.
+
+---
+
+## 4. Server Identity
 
 The server proves its identity using TLS with a self-signed certificate. The TLS private key is generated on first run and is long-term; no rotation mechanism exists yet due to the complexity of multi-peer coordination.
 
@@ -55,9 +198,9 @@ Peers verify the server by its **public key fingerprint**:
 
 ---
 
-## 4. Key Management
+## 5. Key Management
 
-### 4.1 Key Hierarchy
+### 5.1 Key Hierarchy
 
 There are three layers of keys:
 
@@ -72,19 +215,19 @@ This layered design enables:
 - **Password rotation** without re-encrypting every wallet key (only the root key is re-encrypted).
 - **Root key rotation** without requiring the user to change their password.
 
-### 4.2 Encryption at Rest
+### 5.2 Encryption at Rest
 
 The database stores everything in encrypted form using symmetric AEAD. The encryption scheme is versioned to support transparent migration — when the vault unseals, Arbiter automatically re-encrypts any entries that are behind the current scheme version. See [IMPLEMENTATION.md](IMPLEMENTATION.md) for the specific scheme and versioning mechanism.
 
 ---
 
-## 5. Vault Lifecycle
+## 6. Vault Lifecycle
 
-### 5.1 Sealed State
+### 6.1 Sealed State
 
 On boot, the root key is encrypted and the server cannot perform any signing operations. This state is called **Sealed**.
 
-### 5.2 Unseal Flow
+### 6.2 Unseal Flow
 
 To transition to the **Unsealed** state, a User Agent must provide the password:
 
@@ -95,7 +238,7 @@ To transition to the **Unsealed** state, a User Agent must provide the password:
    - **Success:** The root key is decrypted and placed into a hardened memory cell. The server transitions to `Unsealed`. Any entries pending encryption scheme migration are re-encrypted.
    - **Failure:** The server returns an error indicating the password is incorrect.
 
-### 5.3 Memory Protection
+### 6.3 Memory Protection
 
 Once unsealed, the root key must be protected in memory against:
 
@@ -107,9 +250,9 @@ See [IMPLEMENTATION.md](IMPLEMENTATION.md) for the current and planned memory pr
 
 ---
 
-## 6. Permission Engine
+## 7. Permission Engine
 
-### 6.1 Fundamental Rules
+### 7.1 Fundamental Rules
 
 - SDK clients have **no access by default**.
 - Access is granted **explicitly** by a User Agent.
@@ -119,11 +262,45 @@ Each blockchain requires its own policy system due to differences in static tran
 
 Arbiter is also responsible for ensuring that **transaction nonces are never reused**.
 
-### 6.2 EVM Policies
+### 7.2 EVM Policies
 
 Every EVM grant is scoped to a specific **wallet** and **chain ID**.
 
-#### 6.2.1 Transaction Sub-Grants
+#### 7.2.0 Transaction Signing Sequence
+
+The high-level interaction order is:
+
+```mermaid
+sequenceDiagram
+    autonumber
+    actor SDK as SDK Client
+    participant Server
+    participant UA as User Agent
+
+    SDK->>Server: SignTransactionRequest
+    Server->>Server: Resolve wallet and wallet visibility
+    alt Visibility approval required
+        Server->>UA: Ask for wallet visibility approval
+        UA-->>Server: Vote result
+    end
+    Server->>Server: Evaluate transaction
+    Server->>Server: Load grant and limits context
+    alt Grant approval required
+        Server->>UA: Ask for execution / grant approval
+        UA-->>Server: Vote result
+        opt Create persistent grant
+            Server->>Server: Create and store grant
+        end
+        Server->>Server: Retry evaluation
+    end
+    critical Final authorization path
+        Server->>Server: Check limits and record execution
+        Server-->>Server: Signature or evaluation error
+    end
+    Server-->>SDK: Signature or error
+```
+
+#### 7.2.1 Transaction Sub-Grants
 
 Arbiter maintains an ever-expanding database of known contracts and their ABIs. Based on contract knowledge, transaction requests fall into three categories:
 
@@ -147,9 +324,9 @@ Available restrictions:
 
 These transactions have no `calldata` and therefore cannot interact with contracts. They can be subject to the same volume and rate restrictions as above.
 
-#### 6.2.2 Global Limits
+#### 7.2.2 Global Limits
 
 In addition to sub-grant-specific restrictions, the following limits can be applied across all grant types:
 
 - **Gas limit** — Maximum gas per transaction.
-- **Time-window restrictions** — e.g., signing allowed only 08:00–20:00 on Mondays and Thursdays.
+- **Time-window restrictions** — e.g., signing allowed only 08:00–20:00 on Mondays and Thursdays.

CLAUDE.md

@@ -0,0 +1,128 @@
+# CLAUDE.md
+
+This file provides guidance to Claude Code (claude.ai/code) when working with code in this repository.
+
+## Project Overview
+
+Arbiter is a **permissioned signing service** for cryptocurrency wallets. It consists of:
+- **`server/`** — Rust gRPC daemon that holds encrypted keys and enforces policies
+- **`useragent/`** — Flutter desktop app (macOS/Windows) with a Rust backend via Rinf
+- **`protobufs/`** — Protocol Buffer definitions shared between server and client
+
+The vault never exposes key material; it only produces signatures when requests satisfy configured policies.
+
+## Toolchain Setup
+
+Tools are managed via [mise](https://mise.jdx.dev/). Install all required tools:
+```sh
+mise install
+```
+
+Key versions: Rust 1.93.0 (with clippy), Flutter 3.38.9-stable, protoc 29.6, diesel_cli 2.3.6 (sqlite).
+
+## Server (Rust workspace at `server/`)
+
+### Crates
+
+| Crate | Purpose |
+|---|---|
+| `arbiter-proto` | Generated gRPC stubs + protobuf types; compiled from `protobufs/*.proto` via `tonic-prost-build` |
+| `arbiter-server` | Main daemon — actors, DB, EVM policy engine, gRPC service implementation |
+| `arbiter-useragent` | Rust client library for the user agent side of the gRPC protocol |
+| `arbiter-client` | Rust client library for SDK clients |
+
+### Common Commands
+
+```sh
+cd server
+
+# Build
+cargo build
+
+# Run the server daemon
+cargo run -p arbiter-server
+
+# Run all tests (preferred over cargo test)
+cargo nextest run
+
+# Run a single test
+cargo nextest run <test_name>
+
+# Lint
+cargo clippy
+
+# Security audit
+cargo audit
+
+# Check unused dependencies
+cargo shear
+
+# Run snapshot tests and update snapshots
+cargo insta review
+```
+
+### Architecture
+
+The server is actor-based using the **kameo** crate. All long-lived state lives in `GlobalActors`:
+
+- **`Bootstrapper`** — Manages the one-time bootstrap token written to `~/.arbiter/bootstrap_token` on first run.
+- **`KeyHolder`** — Holds the encrypted root key and manages the Sealed/Unsealed vault state machine. On unseal, decrypts the root key into a `memsafe` hardened memory cell.
+- **`FlowCoordinator`** — Coordinates cross-connection flow between user agents and SDK clients.
+- **`EvmActor`** — Handles EVM transaction policy enforcement and signing.
+
+Per-connection actors live under `actors/user_agent/` and `actors/client/`, each with `auth` (challenge-response authentication) and `session` (post-auth operations) sub-modules.
+
+**Database:** SQLite via `diesel-async` + `bb8` connection pool. Schema managed by embedded Diesel migrations in `crates/arbiter-server/migrations/`. DB file lives at `~/.arbiter/arbiter.sqlite`. Tests use a temp-file DB via `db::create_test_pool()`.
+
+**Cryptography:**
+- Authentication: ed25519 (challenge-response, nonce-tracked per peer)
+- Encryption at rest: XChaCha20-Poly1305 (versioned via `scheme` field for transparent migration on unseal)
+- Password KDF: Argon2
+- Unseal transport: X25519 ephemeral key exchange
+- TLS: self-signed certificate (aws-lc-rs backend), fingerprint distributed via `ArbiterUrl`
+
+**Protocol:** gRPC with Protocol Buffers. The `ArbiterUrl` type encodes host, port, CA cert, and bootstrap token into a single shareable string (printed to console on first run).
+
+### Proto Regeneration
+
+When `.proto` files in `protobufs/` change, rebuild to regenerate:
+```sh
+cd server && cargo build -p arbiter-proto
+```
+
+### Database Migrations
+
+```sh
+# Create a new migration
+diesel migration generate <name> --migration-dir crates/arbiter-server/migrations
+
+# Run migrations manually (server also runs them on startup)
+diesel migration run --migration-dir crates/arbiter-server/migrations
+```
+
+## User Agent (Flutter + Rinf at `useragent/`)
+
+The Flutter app uses [Rinf](https://rinf.cunarist.org) to call Rust code. The Rust logic lives in `useragent/native/hub/` as a separate crate that uses `arbiter-useragent` for the gRPC client.
+
+Communication between Dart and Rust uses typed **signals** defined in `useragent/native/hub/src/signals/`. After modifying signal structs, regenerate Dart bindings:
+
+```sh
+cd useragent && rinf gen
+```
+
+### Common Commands
+
+```sh
+cd useragent
+
+# Run the app (macOS or Windows)
+flutter run
+
+# Regenerate Rust↔Dart signal bindings
+rinf gen
+
+# Analyze Dart code
+flutter analyze
+```
+
+The Rinf Rust entry point is `useragent/native/hub/src/lib.rs`. It spawns actors defined in `useragent/native/hub/src/actors/` which handle Dart↔server communication via signals.

IMPLEMENTATION.md

@@ -4,10 +4,81 @@ This document covers concrete technology choices and dependencies. For the archi
 
 ---
 
+## Client Connection Flow
+
+### Authentication Result Semantics
+
+Authentication no longer uses an implicit success-only response shape. Both `client` and `user-agent` return explicit auth status enums over the wire.
+
+- **Client:** `AuthResult` may return `SUCCESS`, `INVALID_KEY`, `INVALID_SIGNATURE`, `APPROVAL_DENIED`, `NO_USER_AGENTS_ONLINE`, or `INTERNAL`
+- **User-agent:** `AuthResult` may return `SUCCESS`, `INVALID_KEY`, `INVALID_SIGNATURE`, `BOOTSTRAP_REQUIRED`, `TOKEN_INVALID`, or `INTERNAL`
+
+This makes transport-level failures and actor/domain-level auth failures distinct:
+
+- **Transport/protocol failures** are surfaced as stream/status errors
+- **Authentication failures** are surfaced as successful protocol responses carrying an explicit auth status
+
+Clients are expected to handle these status codes directly and present the concrete failure reason to the user.
+
+### New Client Approval
+
+When a client whose public key is not yet in the database connects, all connected user agents are asked to approve the connection. The first agent to respond determines the outcome; remaining requests are cancelled via a watch channel.
+
+```mermaid
+flowchart TD
+    A([Client connects]) --> B[Receive AuthChallengeRequest]
+    B --> C{pubkey in DB?}
+
+    C -- yes --> D[Read nonce\nIncrement nonce in DB]
+    D --> G
+
+    C -- no --> E[Ask all UserAgents:\nClientConnectionRequest]
+    E --> F{First response}
+    F -- denied --> Z([Reject connection])
+    F -- approved --> F2[Cancel remaining\nUserAgent requests]
+    F2 --> F3[INSERT client\nnonce = 1]
+    F3 --> G[Send AuthChallenge\nwith nonce]
+
+    G --> H[Receive AuthChallengeSolution]
+    H --> I{Signature valid?}
+    I -- no --> Z
+    I -- yes --> J([Session started])
+```
+
+### Known Issue: Concurrent Registration Race (TOCTOU)
+
+Two connections presenting the same previously-unknown public key can race through the approval flow simultaneously:
+
+1. Both check the DB → neither is registered.
+2. Both request approval from user agents → both receive approval.
+3. Both `INSERT` the client record → the second insert silently overwrites the first, resetting the nonce.
+
+This means the first connection's nonce is invalidated by the second, causing its challenge verification to fail. A fix requires either serialising new-client registration (e.g. an in-memory lock keyed on pubkey) or replacing the separate check + insert with an `INSERT OR IGNORE` / upsert guarded by a unique constraint on `public_key`.
+
+### Nonce Semantics
+
+The `program_client.nonce` column stores the **next usable nonce** — i.e. it is always one ahead of the nonce last issued in a challenge.
+
+- **New client:** inserted with `nonce = 1`; the first challenge is issued with `nonce = 0`.
+- **Existing client:** the current DB value is read and used as the challenge nonce, then immediately incremented within the same exclusive transaction, preventing replay.
+
+---
+
 ## Cryptography
 
 ### Authentication
-- **Signature scheme:** ed25519
+- **Client protocol:** ed25519
+
+### User-Agent Authentication
+
+User-agent authentication supports multiple signature schemes because platform-provided "hardware-bound" keys do not expose a uniform algorithm across operating systems and hardware.
+
+- **Supported schemes:** RSA, Ed25519, ECDSA (secp256k1)
+- **Why:** the user agent authenticates with keys backed by platform facilities, and those facilities differ by platform
+- **Apple Silicon Secure Enclave / Secure Element:** ECDSA-only in practice
+- **Windows Hello / TPM 2.0:** currently RSA-backed in our integration
+
+This is why the user-agent auth protocol carries an explicit `KeyType`, while the SDK client protocol remains fixed to ed25519.
 
 ### Encryption at Rest
 - **Scheme:** Symmetric AEAD — currently **XChaCha20-Poly1305**
@@ -22,14 +93,147 @@ This document covers concrete technology choices and dependencies. For the archi
 ## Communication
 
 - **Protocol:** gRPC with Protocol Buffers
+- **Request/response matching:** multiplexed over a single bidirectional stream using per-connection request IDs
 - **Server identity distribution:** `ServerInfo` protobuf struct containing the TLS public key fingerprint
 - **Future consideration:** grpc-web lacks bidirectional stream support, so a browser-based wallet may require protojson over WebSocket
 
+### Request Multiplexing
+
+Both `client` and `user-agent` connections support multiple in-flight requests over one gRPC bidi stream.
+
+- Every request carries a monotonically increasing request ID
+- Every normal response echoes the request ID it corresponds to
+- Out-of-band server messages omit the response ID entirely
+- The server rejects already-seen request IDs at the transport adapter boundary before business logic sees the message
+
+This keeps request correlation entirely in transport/client connection code while leaving actor and domain handlers unaware of request IDs.
+
+---
+
+## EVM Policy Engine
+
+### Overview
+
+The EVM engine classifies incoming transactions, enforces grant constraints, and records executions. It is the sole path through which a wallet key is used for signing.
+
+The central abstraction is the `Policy` trait. Each implementation handles one semantic transaction category and owns its own database tables for grant storage and transaction logging.
+
+### Transaction Evaluation Flow
+
+`Engine::evaluate_transaction` runs the following steps in order:
+
+1. **Classify** — Each registered policy's `analyze(context)` inspects the transaction fields (`chain`, `to`, `value`, `calldata`). The first one returning `Some(meaning)` wins. If none match, the transaction is rejected as `UnsupportedTransactionType`.
+2. **Find grant** — `Policy::try_find_grant` queries for a non-revoked grant covering this wallet, client, chain, and target address.
+3. **Check shared constraints** — `check_shared_constraints` runs in the engine before any policy-specific logic. It enforces the validity window, gas fee caps, and transaction count rate limit (see below).
+4. **Evaluate** — `Policy::evaluate` checks the decoded meaning against the grant's policy-specific constraints and returns any violations.
+5. **Record** — If `RunKind::Execution` and there are no violations, the engine writes to `evm_transaction_log` and calls `Policy::record_transaction` for any policy-specific logging (e.g., token transfer volume).
+
+The detailed branch structure is shown below:
+
+```mermaid
+flowchart TD
+    A[SDK Client sends sign transaction request] --> B[Server resolves wallet]
+    B --> C{Wallet exists?}
+
+    C -- No --> Z1[Return wallet not found error]
+    C -- Yes --> D[Check SDK client wallet visibility]
+
+    D --> E{Wallet visible to SDK client?}
+    E -- No --> F[Start wallet visibility voting flow]
+    F --> G{Vote approved?}
+    G -- No --> Z2[Return wallet access denied error]
+    G -- Yes --> H[Persist wallet visibility]
+    E -- Yes --> I[Classify transaction meaning]
+    H --> I
+
+    I --> J{Meaning supported?}
+    J -- No --> Z3[Return unsupported transaction error]
+    J -- Yes --> K[Find matching grant]
+
+    K --> L{Grant exists?}
+    L -- Yes --> M[Check grant limits]
+    L -- No --> N[Start execution or grant voting flow]
+
+    N --> O{User-agent decision}
+    O -- Reject --> Z4[Return no matching grant error]
+    O -- Allow once --> M
+    O -- Create grant --> P[Create grant with user-selected limits]
+    P --> Q[Persist grant]
+    Q --> M
+
+    M --> R{Limits exceeded?}
+    R -- Yes --> Z5[Return evaluation error]
+    R -- No --> S[Record transaction in logs]
+    S --> T[Produce signature]
+    T --> U[Return signature to SDK client]
+
+    note1[Limit checks include volume, count, and gas constraints.]
+    note2[Grant lookup depends on classified meaning, such as ether transfer or token transfer.]
+
+    K -. uses .-> note2
+    M -. checks .-> note1
+```
+
+### Policy Trait
+
+| Method | Purpose |
+|---|---|
+| `analyze` | Pure — classifies a transaction into a typed `Meaning`, or `None` if this policy doesn't apply |
+| `evaluate` | Checks the `Meaning` against a `Grant`; returns a list of `EvalViolation`s |
+| `create_grant` | Inserts policy-specific rows; returns the specific grant ID |
+| `try_find_grant` | Finds a matching non-revoked grant for the given `EvalContext` |
+| `find_all_grants` | Returns all non-revoked grants (used for listing) |
+| `record_transaction` | Persists policy-specific data after execution |
+
+`analyze` and `evaluate` are intentionally separate: classification is pure and cheap, while evaluation may involve DB queries (e.g., fetching past transfer volume).
+
+### Registered Policies
+
+**EtherTransfer** — plain ETH transfers (empty calldata)
+
+- Grant requires: allowlist of recipient addresses + one volumetric rate limit (max ETH over a time window)
+- Violations: recipient not in allowlist, cumulative ETH volume exceeded
+
+**TokenTransfer** — ERC-20 `transfer(address,uint256)` calls
+
+- Recognised by ABI-decoding the `transfer(address,uint256)` selector against a static registry of known token contracts (`arbiter_tokens_registry`)
+- Grant requires: token contract address, optional recipient restriction, zero or more volumetric rate limits
+- Violations: recipient mismatch, any volumetric limit exceeded
+
+### Grant Model
+
+Every grant has two layers:
+
+- **Shared (`evm_basic_grant`)** — wallet, chain, validity period, gas fee caps, transaction count rate limit. One row per grant regardless of type.
+- **Specific** — policy-owned tables (`evm_ether_transfer_grant`, `evm_token_transfer_grant`) holding type-specific configuration.
+
+`find_all_grants` uses a `#[diesel::auto_type]` base join between the specific and shared tables, then batch-loads related rows (targets, volume limits) in two additional queries to avoid N+1.
+
+The engine exposes `list_all_grants` which collects across all policy types into `Vec<Grant<SpecificGrant>>` via a blanket `From<Grant<S>> for Grant<SpecificGrant>` conversion.
+
+### Shared Constraints (enforced by the engine)
+
+These are checked centrally in `check_shared_constraints` before policy evaluation:
+
+| Constraint | Fields | Behaviour |
+|---|---|---|
+| Validity window | `valid_from`, `valid_until` | Emits `InvalidTime` if current time is outside the range |
+| Gas fee cap | `max_gas_fee_per_gas`, `max_priority_fee_per_gas` | Emits `GasLimitExceeded` if either cap is breached |
+| Tx count rate limit | `rate_limit` (`count` + `window`) | Counts rows in `evm_transaction_log` within the window; emits `RateLimitExceeded` if at or above the limit |
+
+---
+
+### Known Limitations
+
+- **Only EIP-1559 transactions are supported.** Legacy and EIP-2930 types are rejected outright.
+- **No opaque-calldata (unknown contract) grant type.** The architecture describes a category for unrecognised contracts, but no policy implements it yet. Any transaction that is not a plain ETH transfer or a known ERC-20 transfer is unconditionally rejected.
+- **Token registry is static.** Tokens are recognised only if they appear in the hard-coded `arbiter_tokens_registry` crate. There is no mechanism to register additional contracts at runtime.
+
 ---
 
 ## Memory Protection
 
 The unsealed root key must be held in a hardened memory cell resistant to dumps, page swaps, and hibernation.
 
-- **Current:** Using the `memsafe` crate as an interim solution
-- **Planned:** Custom implementation based on `mlock` (Unix) and `VirtualProtect` (Windows)
+- **Current:** A dedicated memory-protection abstraction is in place, with `memsafe` used behind that abstraction today
+- **Planned:** Additional backends can be introduced behind the same abstraction, including a custom implementation based on `mlock` (Unix) and `VirtualProtect` (Windows)

app/.dart_tool/extension_discovery/README.md

@@ -0,0 +1,31 @@
+Extension Discovery Cache
+=========================
+
+This folder is used by `package:extension_discovery` to cache lists of
+packages that contains extensions for other packages.
+
+DO NOT USE THIS FOLDER
+----------------------
+
+ * Do not read (or rely) the contents of this folder.
+ * Do write to this folder.
+
+If you're interested in the lists of extensions stored in this folder use the
+API offered by package `extension_discovery` to get this information.
+
+If this package doesn't work for your use-case, then don't try to read the
+contents of this folder. It may change, and will not remain stable.
+
+Use package `extension_discovery`
+---------------------------------
+
+If you want to access information from this folder.
+
+Feel free to delete this folder
+-------------------------------
+
+Files in this folder act as a cache, and the cache is discarded if the files
+are older than the modification time of `.dart_tool/package_config.json`.
+
+Hence, it should never be necessary to clear this cache manually, if you find a
+need to do please file a bug.

app/.dart_tool/extension_discovery/vs_code.json

@@ -0,0 +1 @@
+{"version":2,"entries":[{"package":"app","rootUri":"../","packageUri":"lib/"}]}

mise.lock

@@ -1,10 +1,44 @@
+# @generated - this file is auto-generated by `mise lock` https://mise.jdx.dev/dev-tools/mise-lock.html
+
+[[tools.ast-grep]]
+version = "0.42.0"
+backend = "aqua:ast-grep/ast-grep"
+
+[tools.ast-grep."platforms.linux-arm64"]
+checksum = "sha256:5c830eae8456569e2f7212434ed9c238f58dca412d76045418ed6d394a755836"
+url = "https://github.com/ast-grep/ast-grep/releases/download/0.42.0/app-aarch64-unknown-linux-gnu.zip"
+
+[tools.ast-grep."platforms.linux-arm64-musl"]
+checksum = "sha256:5c830eae8456569e2f7212434ed9c238f58dca412d76045418ed6d394a755836"
+url = "https://github.com/ast-grep/ast-grep/releases/download/0.42.0/app-aarch64-unknown-linux-gnu.zip"
+
+[tools.ast-grep."platforms.linux-x64"]
+checksum = "sha256:e825a05603f0bcc4cd9076c4cc8c9abd6d008b7cd07d9aa3cc323ba4b8606651"
+url = "https://github.com/ast-grep/ast-grep/releases/download/0.42.0/app-x86_64-unknown-linux-gnu.zip"
+
+[tools.ast-grep."platforms.linux-x64-musl"]
+checksum = "sha256:e825a05603f0bcc4cd9076c4cc8c9abd6d008b7cd07d9aa3cc323ba4b8606651"
+url = "https://github.com/ast-grep/ast-grep/releases/download/0.42.0/app-x86_64-unknown-linux-gnu.zip"
+
+[tools.ast-grep."platforms.macos-arm64"]
+checksum = "sha256:fc300d5293b1c770a5aece03a8a193b92e71e87cec726c28096990691a582620"
+url = "https://github.com/ast-grep/ast-grep/releases/download/0.42.0/app-aarch64-apple-darwin.zip"
+
+[tools.ast-grep."platforms.macos-x64"]
+checksum = "sha256:979ffe611327056f4730a1ae71b0209b3b830f58b22c6ed194cda34f55400db2"
+url = "https://github.com/ast-grep/ast-grep/releases/download/0.42.0/app-x86_64-apple-darwin.zip"
+
+[tools.ast-grep."platforms.windows-x64"]
+checksum = "sha256:55836fa1b2c65dc7d61615a4d9368622a0d2371a76d28b9a165e5a3ab6ae32a4"
+url = "https://github.com/ast-grep/ast-grep/releases/download/0.42.0/app-x86_64-pc-windows-msvc.zip"
+
 [[tools."cargo:cargo-audit"]]
 version = "0.22.1"
 backend = "cargo:cargo-audit"
 
-[[tools."cargo:cargo-features"]]
-version = "1.0.0"
-backend = "cargo:cargo-features"
+[[tools."cargo:cargo-edit"]]
+version = "0.13.9"
+backend = "cargo:cargo-edit"
 
 [[tools."cargo:cargo-features-manager"]]
 version = "0.11.1"
@@ -19,21 +53,13 @@ version = "0.9.126"
 backend = "cargo:cargo-nextest"
 
 [[tools."cargo:cargo-shear"]]
-version = "1.9.1"
+version = "1.11.2"
 backend = "cargo:cargo-shear"
 
 [[tools."cargo:cargo-vet"]]
 version = "0.10.2"
 backend = "cargo:cargo-vet"
 
-[[tools."cargo:diesel-cli"]]
-version = "2.3.6"
-backend = "cargo:diesel-cli"
-
-[tools."cargo:diesel-cli".options]
-default-features = "false"
-features = "sqlite,sqlite-bundled"
-
 [[tools."cargo:diesel_cli"]]
 version = "2.3.6"
 backend = "cargo:diesel_cli"
@@ -49,11 +75,66 @@ backend = "asdf:flutter"
 [[tools.protoc]]
 version = "29.6"
 backend = "aqua:protocolbuffers/protobuf/protoc"
-"platforms.linux-arm64" = { checksum = "sha256:2594ff4fcae8cb57310d394d0961b236190ad9c5efbfdf1f597ea471d424fe79", url = "https://github.com/protocolbuffers/protobuf/releases/download/v29.6/protoc-29.6-linux-aarch_64.zip"}
-"platforms.linux-x64" = { checksum = "sha256:48785a926e73ffa3f68e2f22b14e7b849620c7a1d36809ac9249a5495e280323", url = "https://github.com/protocolbuffers/protobuf/releases/download/v29.6/protoc-29.6-linux-x86_64.zip"}
-"platforms.macos-arm64" = { checksum = "sha256:b9576b5fa1a1ef3fe13a8c91d9d8204b46545759bea5ae155cd6ba2ea4cdaeed", url = "https://github.com/protocolbuffers/protobuf/releases/download/v29.6/protoc-29.6-osx-aarch_64.zip"}
-"platforms.macos-x64" = { checksum = "sha256:312f04713946921cc0187ef34df80241ddca1bab6f564c636885fd2cc90d3f88", url = "https://github.com/protocolbuffers/protobuf/releases/download/v29.6/protoc-29.6-osx-x86_64.zip"}
-"platforms.windows-x64" = { checksum = "sha256:1ebd7c87baffb9f1c47169b640872bf5fb1e4408079c691af527be9561d8f6f7", url = "https://github.com/protocolbuffers/protobuf/releases/download/v29.6/protoc-29.6-win64.zip"}
+
+[tools.protoc."platforms.linux-arm64"]
+checksum = "sha256:2594ff4fcae8cb57310d394d0961b236190ad9c5efbfdf1f597ea471d424fe79"
+url = "https://github.com/protocolbuffers/protobuf/releases/download/v29.6/protoc-29.6-linux-aarch_64.zip"
+
+[tools.protoc."platforms.linux-arm64-musl"]
+checksum = "sha256:2594ff4fcae8cb57310d394d0961b236190ad9c5efbfdf1f597ea471d424fe79"
+url = "https://github.com/protocolbuffers/protobuf/releases/download/v29.6/protoc-29.6-linux-aarch_64.zip"
+
+[tools.protoc."platforms.linux-x64"]
+checksum = "sha256:48785a926e73ffa3f68e2f22b14e7b849620c7a1d36809ac9249a5495e280323"
+url = "https://github.com/protocolbuffers/protobuf/releases/download/v29.6/protoc-29.6-linux-x86_64.zip"
+
+[tools.protoc."platforms.linux-x64-musl"]
+checksum = "sha256:48785a926e73ffa3f68e2f22b14e7b849620c7a1d36809ac9249a5495e280323"
+url = "https://github.com/protocolbuffers/protobuf/releases/download/v29.6/protoc-29.6-linux-x86_64.zip"
+
+[tools.protoc."platforms.macos-arm64"]
+checksum = "sha256:b9576b5fa1a1ef3fe13a8c91d9d8204b46545759bea5ae155cd6ba2ea4cdaeed"
+url = "https://github.com/protocolbuffers/protobuf/releases/download/v29.6/protoc-29.6-osx-aarch_64.zip"
+
+[tools.protoc."platforms.macos-x64"]
+checksum = "sha256:312f04713946921cc0187ef34df80241ddca1bab6f564c636885fd2cc90d3f88"
+url = "https://github.com/protocolbuffers/protobuf/releases/download/v29.6/protoc-29.6-osx-x86_64.zip"
+
+[tools.protoc."platforms.windows-x64"]
+checksum = "sha256:1ebd7c87baffb9f1c47169b640872bf5fb1e4408079c691af527be9561d8f6f7"
+url = "https://github.com/protocolbuffers/protobuf/releases/download/v29.6/protoc-29.6-win64.zip"
+
+[[tools.python]]
+version = "3.14.3"
+backend = "core:python"
+
+[tools.python."platforms.linux-arm64"]
+checksum = "sha256:53700338695e402a1a1fe22be4a41fbdacc70e22bb308a48eca8ed67cb7992be"
+url = "https://github.com/astral-sh/python-build-standalone/releases/download/20260324/cpython-3.14.3+20260324-aarch64-unknown-linux-gnu-install_only_stripped.tar.gz"
+
+[tools.python."platforms.linux-arm64-musl"]
+checksum = "sha256:53700338695e402a1a1fe22be4a41fbdacc70e22bb308a48eca8ed67cb7992be"
+url = "https://github.com/astral-sh/python-build-standalone/releases/download/20260324/cpython-3.14.3+20260324-aarch64-unknown-linux-gnu-install_only_stripped.tar.gz"
+
+[tools.python."platforms.linux-x64"]
+checksum = "sha256:d7a9f970914bb4c88756fe3bdcc186d4feb90e9500e54f1db47dae4dc9687e39"
+url = "https://github.com/astral-sh/python-build-standalone/releases/download/20260324/cpython-3.14.3+20260324-x86_64-unknown-linux-gnu-install_only_stripped.tar.gz"
+
+[tools.python."platforms.linux-x64-musl"]
+checksum = "sha256:d7a9f970914bb4c88756fe3bdcc186d4feb90e9500e54f1db47dae4dc9687e39"
+url = "https://github.com/astral-sh/python-build-standalone/releases/download/20260324/cpython-3.14.3+20260324-x86_64-unknown-linux-gnu-install_only_stripped.tar.gz"
+
+[tools.python."platforms.macos-arm64"]
+checksum = "sha256:c43aecde4a663aebff99b9b83da0efec506479f1c3f98331442f33d2c43501f9"
+url = "https://github.com/astral-sh/python-build-standalone/releases/download/20260324/cpython-3.14.3+20260324-aarch64-apple-darwin-install_only_stripped.tar.gz"
+
+[tools.python."platforms.macos-x64"]
+checksum = "sha256:9ab41dbc2f100a2a45d1833b9c11165f51051c558b5213eda9a9731d5948a0c0"
+url = "https://github.com/astral-sh/python-build-standalone/releases/download/20260324/cpython-3.14.3+20260324-x86_64-apple-darwin-install_only_stripped.tar.gz"
+
+[tools.python."platforms.windows-x64"]
+checksum = "sha256:bbe19034b35b0267176a7442575ae7dc6343480fd4d35598cb7700173d431e09"
+url = "https://github.com/astral-sh/python-build-standalone/releases/download/20260324/cpython-3.14.3+20260324-x86_64-pc-windows-msvc-install_only_stripped.tar.gz"
 
 [[tools.rust]]
 version = "1.93.0"

mise.toml

@@ -9,3 +9,14 @@ protoc = "29.6"
 "cargo:cargo-nextest" = "0.9.126"
 "cargo:cargo-shear" = "latest"
 "cargo:cargo-insta" = "1.46.3"
+python = "3.14.3"
+ast-grep = "0.42.0"
+"cargo:cargo-edit" = "0.13.9"
+
+[tasks.codegen]
+sources = ['protobufs/*.proto', 'protobufs/**/*.proto']
+outputs = ['useragent/lib/proto/**']
+run = '''
+dart pub global activate protoc_plugin && \
+protoc --dart_out=grpc:useragent/lib/proto --proto_path=protobufs/ $(find protobufs -name '*.proto' | sort)
+'''

protobufs/arbiter.proto

@@ -2,7 +2,6 @@ syntax = "proto3";
 
 package arbiter;
 
-import "auth.proto";
 import "client.proto";
 import "user_agent.proto";
 
@@ -12,6 +11,6 @@ message ServerInfo {
 }
 
 service ArbiterService {
-  rpc Client(stream ClientRequest) returns (stream ClientResponse);
-  rpc UserAgent(stream UserAgentRequest) returns (stream UserAgentResponse);
+  rpc Client(stream arbiter.client.ClientRequest) returns (stream arbiter.client.ClientResponse);
+  rpc UserAgent(stream arbiter.user_agent.UserAgentRequest) returns (stream arbiter.user_agent.UserAgentResponse);
 }

protobufs/auth.proto

@@ -1,35 +0,0 @@
-syntax = "proto3";
-
-package arbiter.auth;
-
-import "google/protobuf/timestamp.proto";
-
-message AuthChallengeRequest {
-  bytes pubkey = 1;
-  optional string bootstrap_token = 2;
-}
-
-message AuthChallenge {
-  bytes pubkey = 1;
-  int32 nonce = 2;
-}
-
-message AuthChallengeSolution {
-  bytes signature = 1;
-}
-
-message AuthOk {}
-
-message ClientMessage {
-  oneof payload {
-    AuthChallengeRequest auth_challenge_request = 1;
-    AuthChallengeSolution auth_challenge_solution = 2;
-  }
-}
-
-message ServerMessage {
-  oneof payload {
-    AuthChallenge auth_challenge = 1;
-    AuthOk auth_ok = 2;
-  }
-}

protobufs/client.proto

@@ -1,17 +1,25 @@
 syntax = "proto3";
 
-package arbiter;
+package arbiter.client;
 
-import "auth.proto";
+import "client/auth.proto";
+import "client/evm.proto";
+import "client/vault.proto";
 
 message ClientRequest {
+  int32 request_id = 4;
   oneof payload {
-    arbiter.auth.ClientMessage auth_message = 1;
+    auth.Request auth = 1;
+    vault.Request vault = 2;
+    evm.Request evm = 3;
   }
 }
 
 message ClientResponse {
+  optional int32 request_id = 7;
   oneof payload {
-    arbiter.auth.ServerMessage auth_message = 1;
+    auth.Response auth = 1;
+    vault.Response vault = 2;
+    evm.Response evm = 3;
   }
 }

protobufs/client/auth.proto

@@ -0,0 +1,43 @@
+syntax = "proto3";
+
+package arbiter.client.auth;
+
+import "shared/client.proto";
+
+message AuthChallengeRequest {
+  bytes pubkey = 1;
+  arbiter.shared.ClientInfo client_info = 2;
+}
+
+message AuthChallenge {
+  bytes pubkey = 1;
+  int32 nonce = 2;
+}
+
+message AuthChallengeSolution {
+  bytes signature = 1;
+}
+
+enum AuthResult {
+  AUTH_RESULT_UNSPECIFIED = 0;
+  AUTH_RESULT_SUCCESS = 1;
+  AUTH_RESULT_INVALID_KEY = 2;
+  AUTH_RESULT_INVALID_SIGNATURE = 3;
+  AUTH_RESULT_APPROVAL_DENIED = 4;
+  AUTH_RESULT_NO_USER_AGENTS_ONLINE = 5;
+  AUTH_RESULT_INTERNAL = 6;
+}
+
+message Request {
+  oneof payload {
+    AuthChallengeRequest challenge_request = 1;
+    AuthChallengeSolution challenge_solution = 2;
+  }
+}
+
+message Response {
+  oneof payload {
+    AuthChallenge challenge = 1;
+    AuthResult result = 2;
+  }
+}

protobufs/client/evm.proto

@@ -0,0 +1,19 @@
+syntax = "proto3";
+
+package arbiter.client.evm;
+
+import "evm.proto";
+
+message Request {
+  oneof payload {
+    arbiter.evm.EvmSignTransactionRequest sign_transaction = 1;
+    arbiter.evm.EvmAnalyzeTransactionRequest analyze_transaction = 2;
+  }
+}
+
+message Response {
+  oneof payload {
+    arbiter.evm.EvmSignTransactionResponse sign_transaction = 1;
+    arbiter.evm.EvmAnalyzeTransactionResponse analyze_transaction = 2;
+  }
+}

protobufs/client/vault.proto

@@ -0,0 +1,18 @@
+syntax = "proto3";
+
+package arbiter.client.vault;
+
+import "google/protobuf/empty.proto";
+import "shared/vault.proto";
+
+message Request {
+  oneof payload {
+    google.protobuf.Empty query_state = 1;
+  }
+}
+
+message Response {
+  oneof payload {
+    arbiter.shared.VaultState state = 1;
+  }
+}

protobufs/evm.proto

@@ -0,0 +1,153 @@
+syntax = "proto3";
+
+package arbiter.evm;
+
+import "google/protobuf/empty.proto";
+import "google/protobuf/timestamp.proto";
+import "shared/evm.proto";
+
+enum EvmError {
+  EVM_ERROR_UNSPECIFIED = 0;
+  EVM_ERROR_VAULT_SEALED = 1;
+  EVM_ERROR_INTERNAL = 2;
+}
+
+message WalletEntry {
+  int32 id = 1;
+  bytes address = 2; // 20-byte Ethereum address
+}
+
+message WalletList {
+  repeated WalletEntry wallets = 1;
+}
+
+message WalletCreateResponse {
+  oneof result {
+    WalletEntry wallet = 1;
+    EvmError error = 2;
+  }
+}
+
+message WalletListResponse {
+  oneof result {
+    WalletList wallets = 1;
+    EvmError error = 2;
+  }
+}
+
+// --- Grant types ---
+
+message TransactionRateLimit {
+  uint32 count = 1;
+  int64 window_secs = 2;
+}
+
+message VolumeRateLimit {
+  bytes max_volume = 1; // U256 as big-endian bytes
+  int64 window_secs = 2;
+}
+
+message SharedSettings {
+  int32 wallet_access_id = 1;
+  uint64 chain_id = 2;
+  optional google.protobuf.Timestamp valid_from = 3;
+  optional google.protobuf.Timestamp valid_until = 4;
+  optional bytes max_gas_fee_per_gas = 5; // U256 as big-endian bytes
+  optional bytes max_priority_fee_per_gas = 6; // U256 as big-endian bytes
+  optional TransactionRateLimit rate_limit = 7;
+}
+
+message EtherTransferSettings {
+  repeated bytes targets = 1; // list of 20-byte Ethereum addresses
+  VolumeRateLimit limit = 2;
+}
+
+message TokenTransferSettings {
+  bytes token_contract = 1; // 20-byte Ethereum address
+  optional bytes target = 2; // 20-byte Ethereum address; absent means any recipient allowed
+  repeated VolumeRateLimit volume_limits = 3;
+}
+
+message SpecificGrant {
+  oneof grant {
+    EtherTransferSettings ether_transfer = 1;
+    TokenTransferSettings token_transfer = 2;
+  }
+}
+
+// --- UserAgent grant management ---
+message EvmGrantCreateRequest {
+  SharedSettings shared = 1;
+  SpecificGrant specific = 2;
+}
+
+message EvmGrantCreateResponse {
+  oneof result {
+    int32 grant_id = 1;
+    EvmError error = 2;
+  }
+}
+
+message EvmGrantDeleteRequest {
+  int32 grant_id = 1;
+}
+
+message EvmGrantDeleteResponse {
+  oneof result {
+    google.protobuf.Empty ok = 1;
+    EvmError error = 2;
+  }
+}
+
+// Basic grant info returned in grant listings
+message GrantEntry {
+  int32 id = 1;
+  int32 wallet_access_id = 2;
+  SharedSettings shared = 3;
+  SpecificGrant specific = 4;
+}
+
+message EvmGrantListRequest {
+  optional int32 wallet_access_id = 1;
+}
+
+message EvmGrantListResponse {
+  oneof result {
+    EvmGrantList grants = 1;
+    EvmError error = 2;
+  }
+}
+
+message EvmGrantList {
+  repeated GrantEntry grants = 1;
+}
+
+// --- Client transaction operations ---
+
+message EvmSignTransactionRequest {
+  bytes wallet_address = 1; // 20-byte Ethereum address
+  bytes rlp_transaction = 2; // RLP-encoded EIP-1559 transaction (unsigned)
+}
+
+// oneof because signing and evaluation happen atomically — a signing failure
+// is always either an eval error or an internal error, never a partial success
+message EvmSignTransactionResponse {
+  oneof result {
+    bytes signature = 1; // 65-byte signature: r[32] || s[32] || v[1]
+    arbiter.shared.evm.TransactionEvalError eval_error = 2;
+    EvmError error = 3;
+  }
+}
+
+message EvmAnalyzeTransactionRequest {
+  bytes wallet_address = 1; // 20-byte Ethereum address
+  bytes rlp_transaction = 2; // RLP-encoded EIP-1559 transaction
+}
+
+message EvmAnalyzeTransactionResponse {
+  oneof result {
+    arbiter.shared.evm.SpecificMeaning meaning = 1;
+    arbiter.shared.evm.TransactionEvalError eval_error = 2;
+    EvmError error = 3;
+  }
+}

protobufs/shared/client.proto

@@ -0,0 +1,9 @@
+syntax = "proto3";
+
+package arbiter.shared;
+
+message ClientInfo {
+  string name = 1;
+  optional string description = 2;
+  optional string version = 3;
+}

protobufs/shared/evm.proto

@@ -0,0 +1,68 @@
+syntax = "proto3";
+
+package arbiter.shared.evm;
+
+import "google/protobuf/empty.proto";
+
+message EtherTransferMeaning {
+  bytes to = 1; // 20-byte Ethereum address
+  bytes value = 2; // U256 as big-endian bytes
+}
+
+message TokenInfo {
+  string symbol = 1;
+  bytes address = 2; // 20-byte Ethereum address
+  uint64 chain_id = 3;
+}
+
+// Mirror of token_transfers::Meaning
+message TokenTransferMeaning {
+  TokenInfo token = 1;
+  bytes to = 2; // 20-byte Ethereum address
+  bytes value = 3; // U256 as big-endian bytes
+}
+
+// Mirror of policies::SpecificMeaning
+message SpecificMeaning {
+  oneof meaning {
+    EtherTransferMeaning ether_transfer = 1;
+    TokenTransferMeaning token_transfer = 2;
+  }
+}
+
+message GasLimitExceededViolation {
+  optional bytes max_gas_fee_per_gas = 1; // U256 as big-endian bytes
+  optional bytes max_priority_fee_per_gas = 2; // U256 as big-endian bytes
+}
+
+message EvalViolation {
+  oneof kind {
+    bytes invalid_target = 1; // 20-byte Ethereum address
+    GasLimitExceededViolation gas_limit_exceeded = 2;
+    google.protobuf.Empty rate_limit_exceeded = 3;
+    google.protobuf.Empty volumetric_limit_exceeded = 4;
+    google.protobuf.Empty invalid_time = 5;
+    google.protobuf.Empty invalid_transaction_type = 6;
+  }
+}
+
+// Transaction was classified but no grant covers it
+message NoMatchingGrantError {
+  SpecificMeaning meaning = 1;
+}
+
+// Transaction was classified and a grant was found, but constraints were violated
+message PolicyViolationsError {
+  SpecificMeaning meaning = 1;
+  repeated EvalViolation violations = 2;
+}
+
+// top-level error returned when transaction evaluation fails
+message TransactionEvalError {
+  oneof kind {
+    google.protobuf.Empty contract_creation_not_supported = 1;
+    google.protobuf.Empty unsupported_transaction_type = 2;
+    NoMatchingGrantError no_matching_grant = 3;
+    PolicyViolationsError policy_violations = 4;
+  }
+}

protobufs/shared/vault.proto

@@ -0,0 +1,11 @@
+syntax = "proto3";
+
+package arbiter.shared;
+
+enum VaultState {
+  VAULT_STATE_UNSPECIFIED = 0;
+  VAULT_STATE_UNBOOTSTRAPPED = 1;
+  VAULT_STATE_SEALED = 2;
+  VAULT_STATE_UNSEALED = 3;
+  VAULT_STATE_ERROR = 4;
+}

protobufs/user_agent.proto

@@ -1,51 +1,28 @@
 syntax = "proto3";
 
-package arbiter;
+package arbiter.user_agent;
 
-import "auth.proto";
-import "google/protobuf/empty.proto";
-
-message UnsealStart {
-  bytes client_pubkey = 1;
-}
-
-message UnsealStartResponse {
-  bytes server_pubkey = 1;
-}
-message UnsealEncryptedKey {
-  bytes nonce = 1;
-  bytes ciphertext = 2;
-  bytes associated_data = 3;
-}
-
-enum UnsealResult {
-  UNSEAL_RESULT_UNSPECIFIED = 0;
-  UNSEAL_RESULT_SUCCESS = 1;
-  UNSEAL_RESULT_INVALID_KEY = 2;
-  UNSEAL_RESULT_UNBOOTSTRAPPED = 3;
-}
-
-enum VaultState {
-  VAULT_STATE_UNSPECIFIED = 0;
-  VAULT_STATE_UNBOOTSTRAPPED = 1;
-  VAULT_STATE_SEALED = 2;
-  VAULT_STATE_UNSEALED = 3;
-  VAULT_STATE_ERROR = 4;
-}
+import "user_agent/auth.proto";
+import "user_agent/evm.proto";
+import "user_agent/sdk_client.proto";
+import "user_agent/vault/vault.proto";
 
 message UserAgentRequest {
+  int32 id = 16;
   oneof payload {
-    arbiter.auth.ClientMessage auth_message = 1;
-    UnsealStart unseal_start = 2;
-    UnsealEncryptedKey unseal_encrypted_key = 3;
-    google.protobuf.Empty query_vault_state = 4;
+    auth.Request auth = 1;
+    vault.Request vault = 2;
+    evm.Request evm = 3;
+    sdk_client.Request sdk_client = 4;
   }
 }
+
 message UserAgentResponse {
+  optional int32 id = 16;
   oneof payload {
-    arbiter.auth.ServerMessage auth_message = 1;
-    UnsealStartResponse unseal_start_response = 2;
-    UnsealResult unseal_result = 3;
-    VaultState vault_state = 4;
+    auth.Response auth = 1;
+    vault.Response vault = 2;
+    evm.Response evm = 3;
+    sdk_client.Response sdk_client = 4;
   }
 }

protobufs/user_agent/auth.proto

@@ -0,0 +1,48 @@
+syntax = "proto3";
+
+package arbiter.user_agent.auth;
+
+enum KeyType {
+  KEY_TYPE_UNSPECIFIED = 0;
+  KEY_TYPE_ED25519 = 1;
+  KEY_TYPE_ECDSA_SECP256K1 = 2;
+  KEY_TYPE_RSA = 3;
+}
+
+message AuthChallengeRequest {
+  bytes pubkey = 1;
+  optional string bootstrap_token = 2;
+  KeyType key_type = 3;
+}
+
+message AuthChallenge {
+  int32 nonce = 1;
+}
+
+message AuthChallengeSolution {
+  bytes signature = 1;
+}
+
+enum AuthResult {
+  AUTH_RESULT_UNSPECIFIED = 0;
+  AUTH_RESULT_SUCCESS = 1;
+  AUTH_RESULT_INVALID_KEY = 2;
+  AUTH_RESULT_INVALID_SIGNATURE = 3;
+  AUTH_RESULT_BOOTSTRAP_REQUIRED = 4;
+  AUTH_RESULT_TOKEN_INVALID = 5;
+  AUTH_RESULT_INTERNAL = 6;
+}
+
+message Request {
+  oneof payload {
+    AuthChallengeRequest challenge_request = 1;
+    AuthChallengeSolution challenge_solution = 2;
+  }
+}
+
+message Response {
+  oneof payload {
+    AuthChallenge challenge = 1;
+    AuthResult result = 2;
+  }
+}

protobufs/user_agent/evm.proto

@@ -0,0 +1,33 @@
+syntax = "proto3";
+
+package arbiter.user_agent.evm;
+
+import "evm.proto";
+import "google/protobuf/empty.proto";
+
+message SignTransactionRequest {
+  int32 client_id = 1;
+  arbiter.evm.EvmSignTransactionRequest request = 2;
+}
+
+message Request {
+  oneof payload {
+    google.protobuf.Empty wallet_create = 1;
+    google.protobuf.Empty wallet_list = 2;
+    arbiter.evm.EvmGrantCreateRequest grant_create = 3;
+    arbiter.evm.EvmGrantDeleteRequest grant_delete = 4;
+    arbiter.evm.EvmGrantListRequest grant_list = 5;
+    SignTransactionRequest sign_transaction = 6;
+  }
+}
+
+message Response {
+  oneof payload {
+    arbiter.evm.WalletCreateResponse wallet_create = 1;
+    arbiter.evm.WalletListResponse wallet_list = 2;
+    arbiter.evm.EvmGrantCreateResponse grant_create = 3;
+    arbiter.evm.EvmGrantDeleteResponse grant_delete = 4;
+    arbiter.evm.EvmGrantListResponse grant_list = 5;
+    arbiter.evm.EvmSignTransactionResponse sign_transaction = 6;
+  }
+}

protobufs/user_agent/sdk_client.proto

@@ -0,0 +1,100 @@
+syntax = "proto3";
+
+package arbiter.user_agent.sdk_client;
+
+import "shared/client.proto";
+import "google/protobuf/empty.proto";
+
+enum Error {
+  ERROR_UNSPECIFIED = 0;
+  ERROR_ALREADY_EXISTS = 1;
+  ERROR_NOT_FOUND = 2;
+  ERROR_HAS_RELATED_DATA = 3; // hard-delete blocked by FK (client has grants or transaction logs)
+  ERROR_INTERNAL = 4;
+}
+
+message RevokeRequest {
+  int32 client_id = 1;
+}
+
+message Entry {
+  int32 id = 1;
+  bytes pubkey = 2;
+  arbiter.shared.ClientInfo info = 3;
+  int32 created_at = 4;
+}
+
+message List {
+  repeated Entry clients = 1;
+}
+
+message RevokeResponse {
+  oneof result {
+    google.protobuf.Empty ok = 1;
+    Error error = 2;
+  }
+}
+
+message ListResponse {
+  oneof result {
+    List clients = 1;
+    Error error = 2;
+  }
+}
+
+message ConnectionRequest {
+  bytes pubkey = 1;
+  arbiter.shared.ClientInfo info = 2;
+}
+
+message ConnectionResponse {
+  bool approved = 1;
+  bytes pubkey = 2;
+}
+
+message ConnectionCancel {
+  bytes pubkey = 1;
+}
+
+message WalletAccess {
+  int32 wallet_id = 1;
+  int32 sdk_client_id = 2;
+}
+
+message WalletAccessEntry {
+  int32 id = 1;
+  WalletAccess access = 2;
+}
+
+message GrantWalletAccess {
+  repeated WalletAccess accesses = 1;
+}
+
+message RevokeWalletAccess {
+  repeated int32 accesses = 1;
+}
+
+message ListWalletAccessResponse {
+  repeated WalletAccessEntry accesses = 1;
+}
+
+message Request {
+  oneof payload {
+    ConnectionResponse connection_response = 1;
+    RevokeRequest revoke = 2;
+    google.protobuf.Empty list = 3;
+    GrantWalletAccess grant_wallet_access = 4;
+    RevokeWalletAccess revoke_wallet_access = 5;
+    google.protobuf.Empty list_wallet_access = 6;
+  }
+}
+
+message Response {
+  oneof payload {
+    ConnectionRequest connection_request = 1;
+    ConnectionCancel connection_cancel = 2;
+    RevokeResponse revoke = 3;
+    ListResponse list = 4;
+    ListWalletAccessResponse list_wallet_access = 5;
+  }
+}

protobufs/user_agent/vault/bootstrap.proto

@@ -0,0 +1,24 @@
+syntax = "proto3";
+
+package arbiter.user_agent.vault.bootstrap;
+
+message BootstrapEncryptedKey {
+  bytes nonce = 1;
+  bytes ciphertext = 2;
+  bytes associated_data = 3;
+}
+
+enum BootstrapResult {
+  BOOTSTRAP_RESULT_UNSPECIFIED = 0;
+  BOOTSTRAP_RESULT_SUCCESS = 1;
+  BOOTSTRAP_RESULT_ALREADY_BOOTSTRAPPED = 2;
+  BOOTSTRAP_RESULT_INVALID_KEY = 3;
+}
+
+message Request {
+  BootstrapEncryptedKey encrypted_key = 2;
+}
+
+message Response {
+  BootstrapResult result = 1;
+}

protobufs/user_agent/vault/unseal.proto

@@ -0,0 +1,37 @@
+syntax = "proto3";
+
+package arbiter.user_agent.vault.unseal;
+
+message UnsealStart {
+  bytes client_pubkey = 1;
+}
+
+message UnsealStartResponse {
+  bytes server_pubkey = 1;
+}
+message UnsealEncryptedKey {
+  bytes nonce = 1;
+  bytes ciphertext = 2;
+  bytes associated_data = 3;
+}
+
+enum UnsealResult {
+  UNSEAL_RESULT_UNSPECIFIED = 0;
+  UNSEAL_RESULT_SUCCESS = 1;
+  UNSEAL_RESULT_INVALID_KEY = 2;
+  UNSEAL_RESULT_UNBOOTSTRAPPED = 3;
+}
+
+message Request {
+  oneof payload {
+    UnsealStart start = 1;
+    UnsealEncryptedKey encrypted_key = 2;
+  }
+}
+
+message Response {
+  oneof payload {
+    UnsealStartResponse start = 1;
+    UnsealResult result = 2;
+  }
+}

protobufs/user_agent/vault/vault.proto

@@ -0,0 +1,24 @@
+syntax = "proto3";
+
+package arbiter.user_agent.vault;
+
+import "google/protobuf/empty.proto";
+import "shared/vault.proto";
+import "user_agent/vault/bootstrap.proto";
+import "user_agent/vault/unseal.proto";
+
+message Request {
+  oneof payload {
+    google.protobuf.Empty query_state = 1;
+    unseal.Request unseal = 2;
+    bootstrap.Request bootstrap = 3;
+  }
+}
+
+message Response {
+  oneof payload {
+    arbiter.shared.VaultState state = 1;
+    unseal.Response unseal = 2;
+    bootstrap.Response bootstrap = 3;
+  }
+}

scripts/gen_erc20_registry.py

@@ -0,0 +1,150 @@
+#!/usr/bin/env python3
+"""
+Fetch the Uniswap default token list and emit Rust `TokenInfo` statics.
+
+Usage:
+    python3 gen_erc20_registry.py                       # fetch from IPFS
+    python3 gen_erc20_registry.py tokens.json           # local file
+    python3 gen_erc20_registry.py tokens.json out.rs    # custom output file
+"""
+
+import json
+import re
+import sys
+import unicodedata
+import urllib.request
+
+UNISWAP_URL = "https://ipfs.io/ipns/tokens.uniswap.org"
+
+SOLANA_CHAIN_ID = 501000101
+IDENTIFIER_RE = re.compile(r"[^A-Za-z0-9]+")
+
+
+def load_tokens(source=None):
+    if source:
+        with open(source) as f:
+            return json.load(f)
+    req = urllib.request.Request(
+        UNISWAP_URL,
+        headers={"Accept": "application/json", "User-Agent": "gen_tokens/1.0"},
+    )
+    with urllib.request.urlopen(req, timeout=60) as resp:
+        return json.loads(resp.read())
+
+
+def escape(s: str) -> str:
+    return s.replace("\\", "\\\\").replace('"', '\\"')
+
+
+def to_screaming_case(name: str) -> str:
+    normalized = unicodedata.normalize("NFKD", name or "")
+    ascii_name = normalized.encode("ascii", "ignore").decode("ascii")
+    snake = IDENTIFIER_RE.sub("_", ascii_name).strip("_").upper()
+    if not snake:
+        snake = "TOKEN"
+    if snake[0].isdigit():
+        snake = f"TOKEN_{snake}"
+    return snake
+
+
+def static_name_for_token(token: dict, used_names: set[str]) -> str:
+    base = to_screaming_case(token.get("name", ""))
+    if base not in used_names:
+        used_names.add(base)
+        return base
+
+    address = token["address"]
+    suffix = f"{token['chainId']}_{address[2:].upper()[-8:]}"
+    candidate = f"{base}_{suffix}"
+
+    i = 2
+    while candidate in used_names:
+        candidate = f"{base}_{suffix}_{i}"
+        i += 1
+
+    used_names.add(candidate)
+    return candidate
+
+
+def main():
+    source = sys.argv[1] if len(sys.argv) > 1 else None
+    output = sys.argv[2] if len(sys.argv) > 2 else "generated_tokens.rs"
+    data = load_tokens(source)
+    tokens = data["tokens"]
+
+    # Deduplicate by (chainId, address)
+    seen = set()
+    unique = []
+    for t in tokens:
+        key = (t["chainId"], t["address"].lower())
+        if key not in seen:
+            seen.add(key)
+            unique.append(t)
+
+    unique.sort(key=lambda t: (t["chainId"], t.get("symbol", "").upper()))
+    evm_tokens = [t for t in unique if t["chainId"] != SOLANA_CHAIN_ID]
+
+    ver = data["version"]
+    lines = []
+    w = lines.append
+
+    w(
+        f"// Auto-generated from Uniswap token list v{ver['major']}.{ver['minor']}.{ver['patch']}"
+    )
+    w(f"// {len(evm_tokens)} tokens")
+    w("// DO NOT EDIT - regenerate with gen_erc20_registry.py")
+    w("")
+
+    used_static_names = set()
+    token_statics = []
+    for t in evm_tokens:
+        static_name = static_name_for_token(t, used_static_names)
+        token_statics.append((static_name, t))
+
+    for static_name, t in token_statics:
+        addr = t["address"]
+        name = escape(t.get("name", ""))
+        symbol = escape(t.get("symbol", ""))
+        decimals = t.get("decimals", 18)
+        logo = t.get("logoURI")
+        chain = t["chainId"]
+
+        logo_val = f'Some("{escape(logo)}")' if logo else "None"
+
+        w(f"pub static {static_name}: TokenInfo = TokenInfo {{")
+        w(f'    name: "{name}",')
+        w(f'    symbol: "{symbol}",')
+        w(f"    decimals: {decimals},")
+        w(f'    contract: address!("{addr}"),')
+        w(f"    chain: {chain},")
+        w(f"    logo_uri: {logo_val},")
+        w("};")
+        w("")
+
+    w("pub static TOKENS: &[&TokenInfo] = &[")
+    for static_name, _ in token_statics:
+        w(f"    &{static_name},")
+    w("];")
+    w("")
+    w("pub fn get_token(")
+    w("    chain_id: alloy::primitives::ChainId,")
+    w("    address: alloy::primitives::Address,")
+    w(") -> Option<&'static TokenInfo> {")
+    w("    match (chain_id, address) {")
+    for static_name, t in token_statics:
+        w(
+            f'        ({t["chainId"]}, addr) if addr == address!("{t["address"]}") => Some(&{static_name}),'
+        )
+    w("        _ => None,")
+    w("    }")
+    w("}")
+    w("")
+
+    with open(output, "w") as f:
+        f.write("\n".join(lines))
+
+    print(f"Wrote {len(token_statics)} tokens to {output}")
+
+
+if __name__ == "__main__":
+    main()

server/.cargo/audit.toml

@@ -0,0 +1,13 @@
+[advisories]
+# RUSTSEC-2023-0071: Marvin Attack timing side-channel in rsa crate.
+# No fixed version is available upstream.
+# RSA support is required for Windows Hello / KeyCredentialManager
+# (https://learn.microsoft.com/en-us/uwp/api/windows.security.credentials.keycredentialmanager.requestcreateasync),
+# which only issues RSA-2048 keys.
+# Mitigations in place:
+#   - Signing uses BlindedSigningKey (PSS+SHA-256), which applies blinding to
+#     protect the private key from timing recovery during signing.
+#   - RSA decryption is never performed; we only verify public-key signatures.
+#   - The attack requires local, high-resolution timing access against the
+#     signing process, which is not exposed in our threat model.
+ignore = ["RUSTSEC-2023-0071"]

server/Cargo.toml

@@ -1,34 +1,45 @@
 [workspace]
 members = [
-    "crates/arbiter-client",
-    "crates/arbiter-proto",
-    "crates/arbiter-server",
-    "crates/arbiter-useragent",
+    "crates/*",
 ]
 resolver = "3"
 
+[workspace.lints.clippy]
+disallowed-methods = "deny"
+
 
 [workspace.dependencies]
-tonic = { version = "0.14.3", features = ["deflate", "gzip", "tls-connect-info", "zstd"] }
+tonic = { version = "0.14.5", features = [
+    "deflate",
+    "gzip",
+    "tls-connect-info",
+    "zstd",
+] }
 tracing = "0.1.44"
-tokio = { version = "1.49.0", features = ["full"] }
+tokio = { version = "1.50.0", features = ["full"] }
 ed25519-dalek = { version = "3.0.0-pre.6", features = ["rand_core"] }
-chrono = { version = "0.4.43", features = ["serde"] }
+chrono = { version = "0.4.44", features = ["serde"] }
 rand = "0.10.0"
-rustls = "0.23.36"
+rustls = { version = "0.23.37", features = ["aws-lc-rs"] }
 smlang = "0.8.0"
-miette = { version = "7.6.0", features = ["fancy", "serde"] }
 thiserror = "2.0.18"
 async-trait = "0.1.89"
-futures = "0.3.31"
+futures = "0.3.32"
 tokio-stream = { version = "0.1.18", features = ["full"] }
 kameo = "0.19.2"
+prost-types = { version = "0.14.3", features = ["chrono"] }
 x25519-dalek = { version = "2.0.1", features = ["getrandom"] }
 rstest = "0.26.1"
 rustls-pki-types = "1.14.0"
+alloy = "1.7.3"
 rcgen = { version = "0.14.7", features = [
     "aws_lc_rs",
     "pem",
     "x509-parser",
     "zeroize",
 ], default-features = false }
+k256 = { version = "0.13.4", features = ["ecdsa", "pkcs8"] }
+rsa = { version = "0.9", features = ["sha2"] }
+sha2 = "0.10"
+spki = "0.7"
+miette = { version = "7.6.0", features = ["fancy", "serde"] }

server/clippy.toml

@@ -0,0 +1,9 @@
+disallowed-methods = [
+    # RSA decryption is forbidden: the rsa crate has RUSTSEC-2023-0071 (Marvin Attack).
+    # We only use RSA for Windows Hello (KeyCredentialManager) public-key verification — decryption
+    # is never required and must not be introduced.
+    { path = "rsa::RsaPrivateKey::decrypt", reason = "RSA decryption is forbidden (RUSTSEC-2023-0071 Marvin Attack). Only PSS signing/verification is permitted." },
+    { path = "rsa::RsaPrivateKey::decrypt_blinded", reason = "RSA decryption is forbidden (RUSTSEC-2023-0071 Marvin Attack). Only PSS signing/verification is permitted." },
+    { path = "rsa::traits::Decryptor::decrypt", reason = "RSA decryption is forbidden (RUSTSEC-2023-0071 Marvin Attack). This blocks decrypt() on rsa::{pkcs1v15,oaep}::DecryptingKey." },
+    { path = "rsa::traits::RandomizedDecryptor::decrypt_with_rng", reason = "RSA decryption is forbidden (RUSTSEC-2023-0071 Marvin Attack). This blocks decrypt_with_rng() on rsa::{pkcs1v15,oaep}::DecryptingKey." },
+]

server/crates/arbiter-client/Cargo.toml

@@ -5,4 +5,22 @@ edition = "2024"
 repository = "https://git.markettakers.org/MarketTakers/arbiter"
 license = "Apache-2.0"
 
+[lints]
+workspace = true
+
+[features]
+evm = ["dep:alloy"]
+
 [dependencies]
+arbiter-proto.path = "../arbiter-proto"
+alloy = { workspace = true, optional = true }
+tonic.workspace = true
+tonic.features = ["tls-aws-lc"]
+tokio.workspace = true
+tokio-stream.workspace = true
+ed25519-dalek.workspace = true
+thiserror.workspace = true
+http = "1.4.0"
+rustls-webpki = { version = "0.103.10", features = ["aws-lc-rs"] }
+async-trait.workspace = true
+rand.workspace = true

server/crates/arbiter-client/src/auth.rs

@@ -0,0 +1,149 @@
+use arbiter_proto::{
+    ClientMetadata, format_challenge,
+    proto::{
+        client::{
+            ClientRequest,
+            auth::{
+                self as proto_auth, AuthChallenge, AuthChallengeRequest, AuthChallengeSolution,
+                AuthResult, request::Payload as AuthRequestPayload,
+                response::Payload as AuthResponsePayload,
+            },
+            client_request::Payload as ClientRequestPayload,
+            client_response::Payload as ClientResponsePayload,
+        },
+        shared::ClientInfo as ProtoClientInfo,
+    },
+};
+use ed25519_dalek::Signer as _;
+
+use crate::{
+    storage::StorageError,
+    transport::{ClientTransport, next_request_id},
+};
+
+#[derive(Debug, thiserror::Error)]
+pub enum AuthError {
+    #[error("Auth challenge was not returned by server")]
+    MissingAuthChallenge,
+
+    #[error("Client approval denied by User Agent")]
+    ApprovalDenied,
+
+    #[error("No User Agents online to approve client")]
+    NoUserAgentsOnline,
+
+    #[error("Unexpected auth response payload")]
+    UnexpectedAuthResponse,
+
+    #[error("Signing key storage error")]
+    Storage(#[from] StorageError),
+}
+
+fn map_auth_result(code: i32) -> AuthError {
+    match AuthResult::try_from(code).unwrap_or(AuthResult::Unspecified) {
+        AuthResult::ApprovalDenied => AuthError::ApprovalDenied,
+        AuthResult::NoUserAgentsOnline => AuthError::NoUserAgentsOnline,
+        AuthResult::Unspecified
+        | AuthResult::Success
+        | AuthResult::InvalidKey
+        | AuthResult::InvalidSignature
+        | AuthResult::Internal => AuthError::UnexpectedAuthResponse,
+    }
+}
+
+async fn send_auth_challenge_request(
+    transport: &mut ClientTransport,
+    metadata: ClientMetadata,
+    key: &ed25519_dalek::SigningKey,
+) -> std::result::Result<(), AuthError> {
+    transport
+        .send(ClientRequest {
+            request_id: next_request_id(),
+            payload: Some(ClientRequestPayload::Auth(proto_auth::Request {
+                payload: Some(AuthRequestPayload::ChallengeRequest(AuthChallengeRequest {
+                    pubkey: key.verifying_key().to_bytes().to_vec(),
+                    client_info: Some(ProtoClientInfo {
+                        name: metadata.name,
+                        description: metadata.description,
+                        version: metadata.version,
+                    }),
+                })),
+            })),
+        })
+        .await
+        .map_err(|_| AuthError::UnexpectedAuthResponse)
+}
+
+async fn receive_auth_challenge(
+    transport: &mut ClientTransport,
+) -> std::result::Result<AuthChallenge, AuthError> {
+    let response = transport
+        .recv()
+        .await
+        .map_err(|_| AuthError::MissingAuthChallenge)?;
+
+    let payload = response.payload.ok_or(AuthError::MissingAuthChallenge)?;
+    match payload {
+        ClientResponsePayload::Auth(response) => match response.payload {
+            Some(AuthResponsePayload::Challenge(challenge)) => Ok(challenge),
+            Some(AuthResponsePayload::Result(result)) => Err(map_auth_result(result)),
+            None => Err(AuthError::MissingAuthChallenge),
+        },
+        _ => Err(AuthError::UnexpectedAuthResponse),
+    }
+}
+
+async fn send_auth_challenge_solution(
+    transport: &mut ClientTransport,
+    key: &ed25519_dalek::SigningKey,
+    challenge: AuthChallenge,
+) -> std::result::Result<(), AuthError> {
+    let challenge_payload = format_challenge(challenge.nonce, &challenge.pubkey);
+    let signature = key.sign(&challenge_payload).to_bytes().to_vec();
+
+    transport
+        .send(ClientRequest {
+            request_id: next_request_id(),
+            payload: Some(ClientRequestPayload::Auth(proto_auth::Request {
+                payload: Some(AuthRequestPayload::ChallengeSolution(
+                    AuthChallengeSolution { signature },
+                )),
+            })),
+        })
+        .await
+        .map_err(|_| AuthError::UnexpectedAuthResponse)
+}
+
+async fn receive_auth_confirmation(
+    transport: &mut ClientTransport,
+) -> std::result::Result<(), AuthError> {
+    let response = transport
+        .recv()
+        .await
+        .map_err(|_| AuthError::UnexpectedAuthResponse)?;
+
+    let payload = response.payload.ok_or(AuthError::UnexpectedAuthResponse)?;
+    match payload {
+        ClientResponsePayload::Auth(response) => match response.payload {
+            Some(AuthResponsePayload::Result(result))
+                if AuthResult::try_from(result).ok() == Some(AuthResult::Success) =>
+            {
+                Ok(())
+            }
+            Some(AuthResponsePayload::Result(result)) => Err(map_auth_result(result)),
+            _ => Err(AuthError::UnexpectedAuthResponse),
+        },
+        _ => Err(AuthError::UnexpectedAuthResponse),
+    }
+}
+
+pub(crate) async fn authenticate(
+    transport: &mut ClientTransport,
+    metadata: ClientMetadata,
+    key: &ed25519_dalek::SigningKey,
+) -> std::result::Result<(), AuthError> {
+    send_auth_challenge_request(transport, metadata, key).await?;
+    let challenge = receive_auth_challenge(transport).await?;
+    send_auth_challenge_solution(transport, key, challenge).await?;
+    receive_auth_confirmation(transport).await
+}

server/crates/arbiter-client/src/bin/test_connect.rs

@@ -0,0 +1,44 @@
+use std::io::{self, Write};
+
+use arbiter_client::ArbiterClient;
+use arbiter_proto::{ClientMetadata, url::ArbiterUrl};
+
+#[tokio::main]
+async fn main() {
+    println!("Testing connection to Arbiter server...");
+    print!("Enter ArbiterUrl: ");
+    let _ = io::stdout().flush();
+
+    let mut input = String::new();
+    if let Err(err) = io::stdin().read_line(&mut input) {
+        eprintln!("Failed to read input: {err}");
+        return;
+    }
+
+    let input = input.trim();
+    if input.is_empty() {
+        eprintln!("ArbiterUrl cannot be empty");
+        return;
+    }
+
+    let url = match ArbiterUrl::try_from(input) {
+        Ok(url) => url,
+        Err(err) => {
+            eprintln!("Invalid ArbiterUrl: {err}");
+            return;
+        }
+    };
+
+    println!("{:#?}", url);
+
+    let metadata = ClientMetadata {
+        name: "arbiter-client test_connect".to_string(),
+        description: Some("Manual connection smoke test".to_string()),
+        version: Some(env!("CARGO_PKG_VERSION").to_string()),
+    };
+
+    match ArbiterClient::connect(url, metadata).await {
+        Ok(_) => println!("Connected and authenticated successfully."),
+        Err(err) => eprintln!("Failed to connect: {:#?}", err),
+    }
+}

server/crates/arbiter-client/src/client.rs

@@ -0,0 +1,94 @@
+use arbiter_proto::{
+    ClientMetadata, proto::arbiter_service_client::ArbiterServiceClient, url::ArbiterUrl,
+};
+use std::sync::Arc;
+use tokio::sync::{Mutex, mpsc};
+use tokio_stream::wrappers::ReceiverStream;
+use tonic::transport::ClientTlsConfig;
+
+use crate::{
+    StorageError,
+    auth::{AuthError, authenticate},
+    storage::{FileSigningKeyStorage, SigningKeyStorage},
+    transport::{BUFFER_LENGTH, ClientTransport},
+};
+
+#[cfg(feature = "evm")]
+use crate::wallets::evm::ArbiterEvmWallet;
+
+#[derive(Debug, thiserror::Error)]
+pub enum Error {
+    #[error("gRPC error")]
+    Grpc(#[from] tonic::Status),
+
+    #[error("Could not establish connection")]
+    Connection(#[from] tonic::transport::Error),
+
+    #[error("Invalid server URI")]
+    InvalidUri(#[from] http::uri::InvalidUri),
+
+    #[error("Invalid CA certificate")]
+    InvalidCaCert(#[from] webpki::Error),
+
+    #[error("Authentication error")]
+    Authentication(#[from] AuthError),
+
+    #[error("Storage error")]
+    Storage(#[from] StorageError),
+}
+
+pub struct ArbiterClient {
+    #[allow(dead_code)]
+    transport: Arc<Mutex<ClientTransport>>,
+}
+
+impl ArbiterClient {
+    pub async fn connect(url: ArbiterUrl, metadata: ClientMetadata) -> Result<Self, Error> {
+        let storage = FileSigningKeyStorage::from_default_location()?;
+        Self::connect_with_storage(url, metadata, &storage).await
+    }
+
+    pub async fn connect_with_storage<S: SigningKeyStorage>(
+        url: ArbiterUrl,
+        metadata: ClientMetadata,
+        storage: &S,
+    ) -> Result<Self, Error> {
+        let key = storage.load_or_create()?;
+        Self::connect_with_key(url, metadata, key).await
+    }
+
+    pub async fn connect_with_key(
+        url: ArbiterUrl,
+        metadata: ClientMetadata,
+        key: ed25519_dalek::SigningKey,
+    ) -> Result<Self, Error> {
+        let anchor = webpki::anchor_from_trusted_cert(&url.ca_cert)?.to_owned();
+        let tls = ClientTlsConfig::new().trust_anchor(anchor);
+
+        let channel =
+            tonic::transport::Channel::from_shared(format!("https://{}:{}", url.host, url.port))?
+                .tls_config(tls)?
+                .connect()
+                .await?;
+
+        let mut client = ArbiterServiceClient::new(channel);
+        let (tx, rx) = mpsc::channel(BUFFER_LENGTH);
+        let response_stream = client.client(ReceiverStream::new(rx)).await?.into_inner();
+
+        let mut transport = ClientTransport {
+            sender: tx,
+            receiver: response_stream,
+        };
+
+        authenticate(&mut transport, metadata, &key).await?;
+
+        Ok(Self {
+            transport: Arc::new(Mutex::new(transport)),
+        })
+    }
+
+    #[cfg(feature = "evm")]
+    pub async fn evm_wallets(&self) -> Result<Vec<ArbiterEvmWallet>, Error> {
+        todo!("fetch EVM wallet list from server")
+    }
+}

server/crates/arbiter-client/src/lib.rs

@@ -1,14 +1,12 @@
-pub fn add(left: u64, right: u64) -> u64 {
-    left + right
-}
+mod auth;
+mod client;
+mod storage;
+mod transport;
+pub mod wallets;
 
-#[cfg(test)]
-mod tests {
-    use super::*;
+pub use auth::AuthError;
+pub use client::{ArbiterClient, Error};
+pub use storage::{FileSigningKeyStorage, SigningKeyStorage, StorageError};
 
-    #[test]
-    fn it_works() {
-        let result = add(2, 2);
-        assert_eq!(result, 4);
-    }
-}
+#[cfg(feature = "evm")]
+pub use wallets::evm::{ArbiterEvmSignTransactionError, ArbiterEvmWallet};

server/crates/arbiter-client/src/storage.rs

@@ -0,0 +1,132 @@
+use arbiter_proto::home_path;
+use std::path::{Path, PathBuf};
+
+#[derive(Debug, thiserror::Error)]
+pub enum StorageError {
+    #[error("I/O error")]
+    Io(#[from] std::io::Error),
+
+    #[error("Invalid signing key length in storage: expected {expected} bytes, got {actual} bytes")]
+    InvalidKeyLength { expected: usize, actual: usize },
+}
+
+pub trait SigningKeyStorage {
+    fn load_or_create(&self) -> std::result::Result<ed25519_dalek::SigningKey, StorageError>;
+}
+
+#[derive(Debug, Clone)]
+pub struct FileSigningKeyStorage {
+    path: PathBuf,
+}
+
+impl FileSigningKeyStorage {
+    pub const DEFAULT_FILE_NAME: &str = "sdk_client_ed25519.key";
+
+    pub fn new(path: impl Into<PathBuf>) -> Self {
+        Self { path: path.into() }
+    }
+
+    pub fn from_default_location() -> std::result::Result<Self, StorageError> {
+        Ok(Self::new(home_path()?.join(Self::DEFAULT_FILE_NAME)))
+    }
+
+    fn read_key(path: &Path) -> std::result::Result<ed25519_dalek::SigningKey, StorageError> {
+        let bytes = std::fs::read(path)?;
+        let raw: [u8; 32] =
+            bytes
+                .try_into()
+                .map_err(|v: Vec<u8>| StorageError::InvalidKeyLength {
+                    expected: 32,
+                    actual: v.len(),
+                })?;
+        Ok(ed25519_dalek::SigningKey::from_bytes(&raw))
+    }
+}
+
+impl SigningKeyStorage for FileSigningKeyStorage {
+    fn load_or_create(&self) -> std::result::Result<ed25519_dalek::SigningKey, StorageError> {
+        if let Some(parent) = self.path.parent() {
+            std::fs::create_dir_all(parent)?;
+        }
+
+        if self.path.exists() {
+            return Self::read_key(&self.path);
+        }
+
+        let key = ed25519_dalek::SigningKey::generate(&mut rand::rng());
+        let raw_key = key.to_bytes();
+
+        // Use create_new to prevent accidental overwrite if another process creates the key first.
+        match std::fs::OpenOptions::new()
+            .create_new(true)
+            .write(true)
+            .open(&self.path)
+        {
+            Ok(mut file) => {
+                use std::io::Write as _;
+                file.write_all(&raw_key)?;
+                Ok(key)
+            }
+            Err(err) if err.kind() == std::io::ErrorKind::AlreadyExists => {
+                Self::read_key(&self.path)
+            }
+            Err(err) => Err(StorageError::Io(err)),
+        }
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::{FileSigningKeyStorage, SigningKeyStorage, StorageError};
+
+    fn unique_temp_key_path() -> std::path::PathBuf {
+        let nanos = std::time::SystemTime::now()
+            .duration_since(std::time::UNIX_EPOCH)
+            .expect("clock should be after unix epoch")
+            .as_nanos();
+        std::env::temp_dir().join(format!(
+            "arbiter-client-key-{}-{}.bin",
+            std::process::id(),
+            nanos
+        ))
+    }
+
+    #[test]
+    fn file_storage_creates_and_reuses_key() {
+        let path = unique_temp_key_path();
+        let storage = FileSigningKeyStorage::new(path.clone());
+
+        let key_a = storage
+            .load_or_create()
+            .expect("first load_or_create should create key");
+        let key_b = storage
+            .load_or_create()
+            .expect("second load_or_create should read same key");
+
+        assert_eq!(key_a.to_bytes(), key_b.to_bytes());
+        assert!(path.exists());
+
+        std::fs::remove_file(path).expect("temp key file should be removable");
+    }
+
+    #[test]
+    fn file_storage_rejects_invalid_key_length() {
+        let path = unique_temp_key_path();
+        std::fs::write(&path, [42u8; 31]).expect("should write invalid key file");
+        let storage = FileSigningKeyStorage::new(path.clone());
+
+        let err = storage
+            .load_or_create()
+            .expect_err("storage should reject non-32-byte key file");
+
+        match err {
+            StorageError::InvalidKeyLength { expected, actual } => {
+                assert_eq!(expected, 32);
+                assert_eq!(actual, 31);
+            }
+            other => panic!("unexpected error: {other:?}"),
+        }
+
+        std::fs::remove_file(path).expect("temp key file should be removable");
+    }
+}

server/crates/arbiter-client/src/transport.rs

@@ -0,0 +1,44 @@
+use arbiter_proto::proto::client::{ClientRequest, ClientResponse};
+use std::sync::atomic::{AtomicI32, Ordering};
+use tokio::sync::mpsc;
+
+pub(crate) const BUFFER_LENGTH: usize = 16;
+static NEXT_REQUEST_ID: AtomicI32 = AtomicI32::new(1);
+
+pub(crate) fn next_request_id() -> i32 {
+    NEXT_REQUEST_ID.fetch_add(1, Ordering::Relaxed)
+}
+
+#[derive(Debug, thiserror::Error)]
+pub(crate) enum ClientSignError {
+    #[error("Transport channel closed")]
+    ChannelClosed,
+
+    #[error("Connection closed by server")]
+    ConnectionClosed,
+}
+
+pub(crate) struct ClientTransport {
+    pub(crate) sender: mpsc::Sender<ClientRequest>,
+    pub(crate) receiver: tonic::Streaming<ClientResponse>,
+}
+
+impl ClientTransport {
+    pub(crate) async fn send(
+        &mut self,
+        request: ClientRequest,
+    ) -> std::result::Result<(), ClientSignError> {
+        self.sender
+            .send(request)
+            .await
+            .map_err(|_| ClientSignError::ChannelClosed)
+    }
+
+    pub(crate) async fn recv(&mut self) -> std::result::Result<ClientResponse, ClientSignError> {
+        match self.receiver.message().await {
+            Ok(Some(resp)) => Ok(resp),
+            Ok(None) => Err(ClientSignError::ConnectionClosed),
+            Err(_) => Err(ClientSignError::ConnectionClosed),
+        }
+    }
+}

server/crates/arbiter-client/src/wallets/evm.rs

@@ -0,0 +1,192 @@
+use alloy::{
+    consensus::SignableTransaction,
+    network::TxSigner,
+    primitives::{Address, B256, ChainId, Signature},
+    signers::{Error, Result, Signer},
+};
+use async_trait::async_trait;
+use std::sync::Arc;
+use tokio::sync::Mutex;
+
+use arbiter_proto::proto::{
+    client::{
+        ClientRequest,
+        client_request::Payload as ClientRequestPayload,
+        client_response::Payload as ClientResponsePayload,
+        evm::{
+            self as proto_evm, request::Payload as EvmRequestPayload,
+            response::Payload as EvmResponsePayload,
+        },
+    },
+    evm::{
+        EvmSignTransactionRequest,
+        evm_sign_transaction_response::Result as EvmSignTransactionResult,
+    },
+    shared::evm::TransactionEvalError,
+};
+
+use crate::transport::{ClientTransport, next_request_id};
+
+/// A typed error payload returned by [`ArbiterEvmWallet`] transaction signing.
+///
+/// This is wrapped into `alloy::signers::Error::Other`, so consumers can downcast by [`TryFrom`] and
+/// interpret the concrete policy evaluation failure instead of parsing strings.
+#[derive(Debug, thiserror::Error)]
+#[non_exhaustive]
+pub enum ArbiterEvmSignTransactionError {
+    #[error("transaction rejected by policy: {0:?}")]
+    PolicyEval(TransactionEvalError),
+}
+
+impl<'a> TryFrom<&'a Error> for &'a ArbiterEvmSignTransactionError {
+    type Error = ();
+
+    fn try_from(value: &'a Error) -> Result<Self, Self::Error> {
+        if let Error::Other(inner) = value
+            && let Some(eval_error) = inner.downcast_ref()
+        {
+            Ok(eval_error)
+        } else {
+            Err(())
+        }
+    }
+}
+
+pub struct ArbiterEvmWallet {
+    transport: Arc<Mutex<ClientTransport>>,
+    address: Address,
+    chain_id: Option<ChainId>,
+}
+
+impl ArbiterEvmWallet {
+    pub(crate) fn new(transport: Arc<Mutex<ClientTransport>>, address: Address) -> Self {
+        Self {
+            transport,
+            address,
+            chain_id: None,
+        }
+    }
+
+    pub fn address(&self) -> Address {
+        self.address
+    }
+
+    pub fn with_chain_id(mut self, chain_id: ChainId) -> Self {
+        self.chain_id = Some(chain_id);
+        self
+    }
+
+    fn validate_chain_id(&self, tx: &mut dyn SignableTransaction<Signature>) -> Result<()> {
+        if let Some(chain_id) = self.chain_id
+            && !tx.set_chain_id_checked(chain_id)
+        {
+            return Err(Error::TransactionChainIdMismatch {
+                signer: chain_id,
+                tx: tx.chain_id().unwrap(),
+            });
+        }
+
+        Ok(())
+    }
+}
+
+#[async_trait]
+impl Signer for ArbiterEvmWallet {
+    async fn sign_hash(&self, _hash: &B256) -> Result<Signature> {
+        Err(Error::other(
+            "hash-only signing is not supported for ArbiterEvmWallet; use transaction signing",
+        ))
+    }
+
+    fn address(&self) -> Address {
+        self.address
+    }
+
+    fn chain_id(&self) -> Option<ChainId> {
+        self.chain_id
+    }
+
+    fn set_chain_id(&mut self, chain_id: Option<ChainId>) {
+        self.chain_id = chain_id;
+    }
+}
+
+#[async_trait]
+impl TxSigner<Signature> for ArbiterEvmWallet {
+    fn address(&self) -> Address {
+        self.address
+    }
+
+    async fn sign_transaction(
+        &self,
+        tx: &mut dyn SignableTransaction<Signature>,
+    ) -> Result<Signature> {
+        self.validate_chain_id(tx)?;
+
+        let mut transport = self.transport.lock().await;
+        let request_id = next_request_id();
+        let rlp_transaction = tx.encoded_for_signing();
+
+        transport
+            .send(ClientRequest {
+                request_id,
+                payload: Some(ClientRequestPayload::Evm(proto_evm::Request {
+                    payload: Some(EvmRequestPayload::SignTransaction(
+                        EvmSignTransactionRequest {
+                            wallet_address: self.address.to_vec(),
+                            rlp_transaction,
+                        },
+                    )),
+                })),
+            })
+            .await
+            .map_err(|_| Error::other("failed to send evm sign transaction request"))?;
+
+        let response = transport
+            .recv()
+            .await
+            .map_err(|_| Error::other("failed to receive evm sign transaction response"))?;
+
+        if response.request_id != Some(request_id) {
+            return Err(Error::other(
+                "received mismatched response id for evm sign transaction",
+            ));
+        }
+
+        let payload = response
+            .payload
+            .ok_or_else(|| Error::other("missing evm sign transaction response payload"))?;
+
+        let ClientResponsePayload::Evm(proto_evm::Response {
+            payload: Some(payload),
+        }) = payload
+        else {
+            return Err(Error::other(
+                "unexpected response payload for evm sign transaction request",
+            ));
+        };
+
+        let EvmResponsePayload::SignTransaction(response) = payload else {
+            return Err(Error::other(
+                "unexpected evm response payload for sign transaction request",
+            ));
+        };
+
+        let result = response
+            .result
+            .ok_or_else(|| Error::other("missing evm sign transaction result"))?;
+
+        match result {
+            EvmSignTransactionResult::Signature(signature) => {
+                Signature::try_from(signature.as_slice())
+                    .map_err(|_| Error::other("invalid signature returned by server"))
+            }
+            EvmSignTransactionResult::EvalError(eval_error) => Err(Error::other(
+                ArbiterEvmSignTransactionError::PolicyEval(eval_error),
+            )),
+            EvmSignTransactionResult::Error(code) => Err(Error::other(format!(
+                "server failed to sign transaction with error code {code}"
+            ))),
+        }
+    }
+}

server/crates/arbiter-client/src/wallets/mod.rs

@@ -0,0 +1,2 @@
+#[cfg(feature = "evm")]
+pub mod evm;

server/crates/arbiter-proto/Cargo.toml

@@ -9,7 +9,8 @@ license = "Apache-2.0"
 tonic.workspace = true
 tokio.workspace = true
 futures.workspace = true
-tonic-prost = "0.14.3"
+hex = "0.4.3"
+tonic-prost = "0.14.5"
 prost = "0.14.3"
 kameo.workspace = true
 url = "2.5.8"
@@ -17,11 +18,14 @@ miette.workspace = true
 thiserror.workspace = true
 rustls-pki-types.workspace = true
 base64 = "0.22.1"
+prost-types.workspace = true
 tracing.workspace = true
-
+async-trait.workspace = true
+tokio-stream.workspace = true
 
 [build-dependencies]
-tonic-prost-build = "0.14.3"
+tonic-prost-build = "0.14.5"
+protoc-bin-vendored = "3"
 
 [dev-dependencies]
 rstest.workspace = true
@@ -30,5 +34,3 @@ rcgen.workspace = true
 
 [package.metadata.cargo-shear]
 ignored = ["tonic-prost", "prost", "kameo"]
-
-

server/crates/arbiter-proto/build.rs

@@ -3,7 +3,6 @@ use tonic_prost_build::configure;
 static PROTOBUF_DIR: &str = "../../../protobufs";
 
 fn main() -> Result<(), Box<dyn std::error::Error>> {
-
     println!("cargo::rerun-if-changed={PROTOBUF_DIR}");
 
     configure()
@@ -11,11 +10,12 @@ fn main() -> Result<(), Box<dyn std::error::Error>> {
         .compile_protos(
             &[
                 format!("{}/arbiter.proto", PROTOBUF_DIR),
-                format!("{}/auth.proto", PROTOBUF_DIR),
+                format!("{}/user_agent.proto", PROTOBUF_DIR),
+                format!("{}/client.proto", PROTOBUF_DIR),
+                format!("{}/evm.proto", PROTOBUF_DIR),
             ],
             &[PROTOBUF_DIR.to_string()],
         )
-        
         .unwrap();
     Ok(())
 }

server/crates/arbiter-proto/src/lib.rs

@@ -3,14 +3,71 @@ pub mod url;
 
 use base64::{Engine, prelude::BASE64_STANDARD};
 
-use crate::proto::auth::AuthChallenge;
-
 pub mod proto {
     tonic::include_proto!("arbiter");
 
-    pub mod auth {
-        tonic::include_proto!("arbiter.auth");
+    pub mod shared {
+        tonic::include_proto!("arbiter.shared");
+
+        pub mod evm {
+            tonic::include_proto!("arbiter.shared.evm");
+        }
     }
+
+    pub mod user_agent {
+        tonic::include_proto!("arbiter.user_agent");
+
+        pub mod auth {
+            tonic::include_proto!("arbiter.user_agent.auth");
+        }
+
+        pub mod evm {
+            tonic::include_proto!("arbiter.user_agent.evm");
+        }
+
+        pub mod sdk_client {
+            tonic::include_proto!("arbiter.user_agent.sdk_client");
+        }
+
+        pub mod vault {
+            tonic::include_proto!("arbiter.user_agent.vault");
+
+            pub mod bootstrap {
+                tonic::include_proto!("arbiter.user_agent.vault.bootstrap");
+            }
+
+            pub mod unseal {
+                tonic::include_proto!("arbiter.user_agent.vault.unseal");
+            }
+        }
+    }
+
+    pub mod client {
+        tonic::include_proto!("arbiter.client");
+
+        pub mod auth {
+            tonic::include_proto!("arbiter.client.auth");
+        }
+
+        pub mod evm {
+            tonic::include_proto!("arbiter.client.evm");
+        }
+
+        pub mod vault {
+            tonic::include_proto!("arbiter.client.vault");
+        }
+    }
+
+    pub mod evm {
+        tonic::include_proto!("arbiter.evm");
+    }
+}
+
+#[derive(Debug, Clone, PartialEq, Eq)]
+pub struct ClientMetadata {
+    pub name: String,
+    pub description: Option<String>,
+    pub version: Option<String>,
 }
 
 pub static BOOTSTRAP_PATH: &str = "bootstrap_token";
@@ -28,7 +85,7 @@ pub fn home_path() -> Result<std::path::PathBuf, std::io::Error> {
     Ok(arbiter_home)
 }
 
-pub fn format_challenge(challenge: &AuthChallenge) -> Vec<u8> {
-    let concat_form = format!("{}:{}", challenge.nonce, BASE64_STANDARD.encode(&challenge.pubkey));
-    concat_form.into_bytes().to_vec()
+pub fn format_challenge(nonce: i32, pubkey: &[u8]) -> Vec<u8> {
+    let concat_form = format!("{}:{}", nonce, BASE64_STANDARD.encode(pubkey));
+    concat_form.into_bytes()
 }

server/crates/arbiter-proto/src/transport.rs

@@ -1,371 +1,163 @@
-//! Transport abstraction layer for bridging gRPC bidirectional streaming with kameo actors.
+//! Transport-facing abstractions shared by protocol/session code.
 //!
-//! This module provides a clean separation between the gRPC transport layer and business logic
-//! by modeling the connection as two linked kameo actors:
+//! This module defines a small set of transport traits that actors and other
+//! protocol code can depend on without knowing anything about the concrete
+//! transport underneath.
 //!
-//! - A **transport actor** ([`GrpcTransportActor`]) that owns the gRPC stream and channel,
-//!   forwarding inbound messages to the business actor and outbound messages to the client.
-//! - A **business logic actor** that receives inbound messages from the transport actor and
-//!   sends outbound messages back through the transport actor.
+//! The abstraction is split into:
+//! - [`Sender`] for outbound delivery
+//! - [`Receiver`] for inbound delivery
+//! - [`Bi`] as the combined duplex form (`Sender + Receiver`)
 //!
-//! The [`wire()`] function sets up bidirectional linking between the two actors, ensuring
-//! that if either actor dies, the other is notified and can shut down gracefully.
+//! This split lets code depend only on the half it actually needs. For
+//! example, some actor/session code only sends out-of-band messages, while
+//! auth/state-machine code may need full duplex access.
 //!
-//! # Terminology
+//! [`Bi`] remains intentionally minimal and transport-agnostic:
+//! - [`Receiver::recv`] yields inbound messages
+//! - [`Sender::send`] accepts outbound messages
 //!
-//! - **InboundMessage**: a message received by the transport actor from the channel/socket
-//!   and forwarded to the business actor.
-//! - **OutboundMessage**: a message produced by the business actor and sent to the transport
-//!   actor to be forwarded to the channel/socket.
+//! Transport-specific adapters, including protobuf or gRPC bridges, live in the
+//! crates that own those boundaries rather than in `arbiter-proto`.
 //!
-//! # Architecture
+//! [`Bi`] deliberately does not model request/response correlation. Some
+//! transports may carry multiplexed request/response traffic, some may emit
+//! out-of-band messages, and some may be one-message-at-a-time state machines.
+//! Correlation concerns such as request IDs, pending response maps, and
+//! out-of-band routing belong in the adapter or connection layer built on top
+//! of [`Bi`], not in this abstraction itself.
 //!
-//! ```text
-//! gRPC Stream ──InboundMessage──▶ GrpcTransportActor ──tell(InboundMessage)──▶ BusinessActor
-//!                                 ▲                                    │
-//!                                 └─tell(Result<OutboundMessage, _>)────┘
-//!                                 │
-//!                          mpsc::Sender ──▶ Client
-//! ```
+//! # Generic Ordering Rule
 //!
-//! # Example
+//! This module consistently uses `Inbound` first and `Outbound` second in
+//! generic parameter lists.
 //!
-//! ```rust,ignore
-//! let (tx, rx) = mpsc::channel(1000);
-//! let context = server_context.clone();
+//! For [`Receiver`], [`Sender`], and [`Bi`], this means:
+//! - `Receiver<Inbound>`
+//! - `Sender<Outbound>`
+//! - `Bi<Inbound, Outbound>`
 //!
-//! wire(
-//!     |transport_ref| MyBusinessActor::new(context, transport_ref),
-//!     |business_recipient, business_id| GrpcTransportActor {
-//!         sender: tx,
-//!         receiver: grpc_stream,
-//!         business_logic_actor: business_recipient,
-//!         business_logic_actor_id: business_id,
-//!     },
-//! ).await;
+//! Concretely, for [`Bi`]:
+//! - `recv() -> Option<Inbound>`
+//! - `send(Outbound)`
 //!
-//! Ok(Response::new(ReceiverStream::new(rx)))
-//! ```
+//! [`expect_message`] is a small helper for linear protocol steps: it reads one
+//! inbound message from a transport and extracts a typed value from it, failing
+//! if the channel closes or the message shape is not what the caller expected.
+//!
+//! [`DummyTransport`] is a no-op implementation useful for tests and local
+//! actor execution where no real stream exists.
+//!
+//! # Design Notes
+//!
+//! - [`Bi::send`] returns [`Error`] only for transport delivery failures, such
+//!   as a closed outbound channel.
+//! - [`Bi::recv`] returns `None` when the underlying transport closes.
+//! - Message translation is intentionally out of scope for this module.
 
-use futures::{Stream, StreamExt};
-use kameo::{
-    Actor,
-    actor::{ActorRef, PreparedActor, Recipient, Spawn, WeakActorRef},
-    mailbox::Signal,
-    prelude::Message,
-};
-use tokio::{
-    select,
-    sync::mpsc::{self, error::SendError},
-};
-use tonic::{Status, Streaming};
-use tracing::{debug, error};
+use std::marker::PhantomData;
 
-/// A bidirectional stream abstraction for sans-io testing.
-///
-/// Combines a [`Stream`] of incoming messages with the ability to [`send`](Bi::send)
-/// outgoing responses. This trait allows business logic to be tested without a real
-/// gRPC connection by swapping in an in-memory implementation.
-///
-/// # Type Parameters
-/// - `T`: `InboundMessage` received from the channel/socket (e.g., `UserAgentRequest`)
-/// - `U`: `OutboundMessage` sent to the channel/socket (e.g., `UserAgentResponse`)
-pub trait Bi<T, U>: Stream<Item = Result<T, Status>> + Send + Sync + 'static {
-    type Error;
-    fn send(
-        &mut self,
-        item: Result<U, Status>,
-    ) -> impl std::future::Future<Output = Result<(), Self::Error>> + Send;
+use async_trait::async_trait;
+
+/// Errors returned by transport adapters implementing [`Bi`].
+#[derive(thiserror::Error, Debug)]
+pub enum Error {
+    #[error("Transport channel is closed")]
+    ChannelClosed,
+    #[error("Unexpected message received")]
+    UnexpectedMessage,
 }
 
-/// Concrete [`Bi`] implementation backed by a tonic gRPC [`Streaming`] and an [`mpsc::Sender`].
-///
-/// This is the production implementation used in gRPC service handlers. The `request_stream`
-/// receives messages from the client, and `response_sender` sends responses back.
-pub struct BiStream<T, U> {
-    pub request_stream: Streaming<T>,
-    pub response_sender: mpsc::Sender<Result<U, Status>>,
-}
-
-impl<T, U> Stream for BiStream<T, U>
+/// Receives one message from `transport` and extracts a value from it using
+/// `extractor`. Returns [`Error::ChannelClosed`] if the transport closes and
+/// [`Error::UnexpectedMessage`] if `extractor` returns `None`.
+pub async fn expect_message<T, Inbound, Outbound, Target, F>(
+    transport: &mut T,
+    extractor: F,
+) -> Result<Target, Error>
 where
-    T: Send + 'static,
-    U: Send + 'static,
+    T: Bi<Inbound, Outbound> + ?Sized,
+    F: FnOnce(Inbound) -> Option<Target>,
 {
-    type Item = Result<T, Status>;
-
-    fn poll_next(
-        mut self: std::pin::Pin<&mut Self>,
-        cx: &mut std::task::Context<'_>,
-    ) -> std::task::Poll<Option<Self::Item>> {
-        self.request_stream.poll_next_unpin(cx)
-    }
+    let msg = transport.recv().await.ok_or(Error::ChannelClosed)?;
+    extractor(msg).ok_or(Error::UnexpectedMessage)
 }
 
-impl<T, U> Bi<T, U> for BiStream<T, U>
-where
-    T: Send + 'static,
-    U: Send + 'static,
-{
-    type Error = SendError<Result<U, Status>>;
-
-    async fn send(&mut self, item: Result<U, Status>) -> Result<(), Self::Error> {
-        self.response_sender.send(item).await
-    }
+#[async_trait]
+pub trait Sender<Outbound>: Send + Sync {
+    async fn send(&mut self, item: Outbound) -> Result<(), Error>;
 }
 
-/// Marker trait for transport actors that can receive outbound messages of type `T`.
-///
-/// Implement this on your transport actor to indicate it can handle outbound messages
-/// produced by the business actor. Requires the actor to implement [`Message<Result<T, E>>`]
-/// so business logic can forward responses via [`tell()`](ActorRef::tell).
-///
-/// # Example
-///
-/// ```rust,ignore
-/// #[derive(Actor)]
-/// struct MyTransportActor { /* ... */ }
-///
-/// impl Message<Result<MyResponse, MyError>> for MyTransportActor {
-///     type Reply = ();
-///     async fn handle(&mut self, msg: Result<MyResponse, MyError>, _ctx: &mut Context<Self, Self::Reply>) -> Self::Reply {
-///         // forward outbound message to channel/socket
-///     }
-/// }
-///
-/// impl TransportActor<MyResponse, MyError> for MyTransportActor {}
-/// ```
-pub trait TransportActor<Outbound: Send + 'static, DomainError: Send + 'static>:
-    Actor + Send + Message<Result<Outbound, DomainError>>
-{
+#[async_trait]
+pub trait Receiver<Inbound>: Send + Sync {
+    async fn recv(&mut self) -> Option<Inbound>;
 }
 
-/// A kameo actor that bridges a gRPC bidirectional stream with a business logic actor.
+/// Minimal bidirectional transport abstraction used by protocol code.
 ///
-/// This actor owns the gRPC [`Streaming`] receiver and an [`mpsc::Sender`] for responses.
-/// It multiplexes between its own mailbox (for outbound messages from the business actor)
-/// and the gRPC stream (for inbound client messages) using [`tokio::select!`].
+/// `Bi<Inbound, Outbound>` is the combined duplex form of [`Sender`] and
+/// [`Receiver`].
 ///
-/// # Message Flow
+/// It models a channel with:
+/// - inbound items of type `Inbound` read via [`Bi::recv`]
+/// - outbound items of type `Outbound` written via [`Bi::send`]
 ///
-/// - **Inbound**: Messages from the gRPC stream are forwarded to `business_logic_actor`
-///   via [`tell()`](Recipient::tell).
-/// - **Outbound**: The business actor sends `Result<Outbound, DomainError>` messages to this
-///   actor, which forwards them through the `sender` channel to the gRPC response stream.
-///
-/// # Lifecycle
-///
-/// - If the business logic actor dies (detected via actor linking), this actor stops,
-///   which closes the gRPC stream.
-/// - If the gRPC stream closes or errors, this actor stops, which (via linking) notifies
-///   the business actor.
-/// - Error responses (`Err(DomainError)`) are forwarded to the client and then the actor stops,
-///   closing the connection.
-///
-/// # Type Parameters
-/// - `Outbound`: `OutboundMessage` sent to the client (e.g., `UserAgentResponse`)
-/// - `Inbound`: `InboundMessage` received from the client (e.g., `UserAgentRequest`)
-/// - `E`: The domain error type, must implement `Into<tonic::Status>` for gRPC conversion
-pub struct GrpcTransportActor<Outbound, Inbound, DomainError>
-where
-    Outbound: Send + 'static,
-    Inbound: Send + 'static,
-    DomainError: Into<tonic::Status> + Send + 'static,
-{
-    sender: mpsc::Sender<Result<Outbound, tonic::Status>>,
-    receiver: tonic::Streaming<Inbound>,
-    business_logic_actor: Recipient<Inbound>,
-    _error: std::marker::PhantomData<DomainError>,
+/// It does not imply request/response sequencing, one-at-a-time exchange, or
+/// any built-in correlation mechanism between inbound and outbound items.
+pub trait Bi<Inbound, Outbound>: Sender<Outbound> + Receiver<Inbound> + Send + Sync {}
+
+pub trait SplittableBi<Inbound, Outbound>: Bi<Inbound, Outbound> {
+    type Sender: Sender<Outbound>;
+    type Receiver: Receiver<Inbound>;
+
+    fn split(self) -> (Self::Sender, Self::Receiver);
+    fn from_parts(sender: Self::Sender, receiver: Self::Receiver) -> Self;
 }
 
-impl<Outbound, Inbound, DomainError> GrpcTransportActor<Outbound, Inbound, DomainError>
-where
-    Outbound: Send + 'static,
-    Inbound: Send + 'static,
-    DomainError: Into<tonic::Status> + Send + 'static,
-{
-    pub fn new(
-        sender: mpsc::Sender<Result<Outbound, tonic::Status>>,
-        receiver: tonic::Streaming<Inbound>,
-        business_logic_actor: Recipient<Inbound>,
-    ) -> Self {
+/// No-op [`Bi`] transport for tests and manual actor usage.
+///
+/// `send` drops all items and succeeds. [`Bi::recv`] never resolves and therefore
+/// does not busy-wait or spuriously close the stream.
+pub struct DummyTransport<Inbound, Outbound> {
+    _marker: PhantomData<(Inbound, Outbound)>,
+}
+
+impl<Inbound, Outbound> Default for DummyTransport<Inbound, Outbound> {
+    fn default() -> Self {
         Self {
-            sender,
-            receiver,
-            business_logic_actor,
-            _error: std::marker::PhantomData,
+            _marker: PhantomData,
         }
     }
 }
 
-impl<Outbound, Inbound, E> Actor for GrpcTransportActor<Outbound, Inbound, E>
+#[async_trait]
+impl<Inbound, Outbound> Sender<Outbound> for DummyTransport<Inbound, Outbound>
 where
-    Outbound: Send + 'static,
-    Inbound: Send + 'static,
-    E: Into<tonic::Status> + Send + 'static,
+    Inbound: Send + Sync + 'static,
+    Outbound: Send + Sync + 'static,
 {
-    type Args = Self;
-
-    type Error = ();
-
-    async fn on_start(args: Self::Args, _: ActorRef<Self>) -> Result<Self, Self::Error> {
-        Ok(args)
-    }
-
-    fn on_link_died(
-        &mut self,
-        _: WeakActorRef<Self>,
-        id: kameo::prelude::ActorId,
-        _: kameo::prelude::ActorStopReason,
-    ) -> impl Future<
-        Output = Result<std::ops::ControlFlow<kameo::prelude::ActorStopReason>, Self::Error>,
-    > + Send {
-        async move {
-            if id == self.business_logic_actor.id() {
-                error!("Business logic actor died, stopping GrpcTransportActor");
-                Ok(std::ops::ControlFlow::Break(
-                    kameo::prelude::ActorStopReason::Normal,
-                ))
-            } else {
-                debug!(
-                    "Linked actor {} died, but it's not the business logic actor, ignoring",
-                    id
-                );
-                Ok(std::ops::ControlFlow::Continue(()))
-            }
-        }
-    }
-
-    async fn next(
-        &mut self,
-        _: WeakActorRef<Self>,
-        mailbox_rx: &mut kameo::prelude::MailboxReceiver<Self>,
-    ) -> Option<kameo::mailbox::Signal<Self>> {
-        select! {
-            msg = mailbox_rx.recv() => {
-                msg
-            }
-            recv_msg = self.receiver.next() => {
-                match recv_msg {
-                    Some(Ok(msg)) => {
-                        match self.business_logic_actor.tell(msg).await {
-                            Ok(_) => None,
-                            Err(e) => {
-                                // TODO: this would probably require better error handling - or resending if backpressure is the issue
-                                error!("Failed to send message to business logic actor: {}", e);
-                                Some(Signal::Stop)
-                            }
-                        }
-                    }
-                    Some(Err(e)) => {
-                        error!("Received error from stream: {}, stopping GrpcTransportActor", e);
-                        Some(Signal::Stop)
-                    }
-                    None => {
-                        error!("Receiver channel closed, stopping GrpcTransportActor");
-                        Some(Signal::Stop)
-                    }
-                }
-            }
-        }
+    async fn send(&mut self, _item: Outbound) -> Result<(), Error> {
+        Ok(())
     }
 }
 
-impl<Outbound, Inbound, E> Message<Result<Outbound, E>> for GrpcTransportActor<Outbound, Inbound, E>
+#[async_trait]
+impl<Inbound, Outbound> Receiver<Inbound> for DummyTransport<Inbound, Outbound>
 where
-    Outbound: Send + 'static,
-    Inbound: Send + 'static,
-    E: Into<tonic::Status> + Send + 'static,
+    Inbound: Send + Sync + 'static,
+    Outbound: Send + Sync + 'static,
 {
-    type Reply = ();
-
-    async fn handle(
-        &mut self,
-        msg: Result<Outbound, E>,
-        ctx: &mut kameo::prelude::Context<Self, Self::Reply>,
-    ) -> Self::Reply {
-        let is_err = msg.is_err();
-        let grpc_msg = msg.map_err(Into::into);
-        match self.sender.send(grpc_msg).await {
-            Ok(_) => {
-                if is_err {
-                    ctx.stop();
-                }
-            }
-            Err(e) => {
-                error!("Failed to send message: {}", e);
-                ctx.stop();
-            }
-        }
+    async fn recv(&mut self) -> Option<Inbound> {
+        std::future::pending::<()>().await;
+        None
     }
 }
 
-impl<Outbound, Inbound, E> TransportActor<Outbound, E> for GrpcTransportActor<Outbound, Inbound, E>
+impl<Inbound, Outbound> Bi<Inbound, Outbound> for DummyTransport<Inbound, Outbound>
 where
-    Outbound: Send + 'static,
-    Inbound: Send + 'static,
-    E: Into<tonic::Status> + Send + 'static,
+    Inbound: Send + Sync + 'static,
+    Outbound: Send + Sync + 'static,
 {
 }
 
-/// Wires together a transport actor and a business logic actor with bidirectional linking.
-///
-/// This function handles the chicken-and-egg problem of two actors that need references
-/// to each other at construction time. It uses kameo's [`PreparedActor`] to obtain
-/// [`ActorRef`]s before spawning, then links both actors so that if either dies,
-/// the other is notified via [`on_link_died`](Actor::on_link_died).
-///
-/// The business actor receives a type-erased [`Recipient<Result<Outbound, DomainError>>`] instead of an
-/// `ActorRef<Transport>`, keeping it decoupled from the concrete transport implementation.
-///
-/// # Type Parameters
-/// - `Transport`: The transport actor type (e.g., [`GrpcTransportActor`])
-/// - `Inbound`: `InboundMessage` received by the business actor from the transport
-/// - `Outbound`: `OutboundMessage` sent by the business actor back to the transport
-/// - `Business`: The business logic actor
-/// - `BusinessCtor`: Closure that receives a prepared business actor and transport recipient,
-///   spawns the business actor, and returns its [`ActorRef`]
-/// - `TransportCtor`: Closure that receives a prepared transport actor, a recipient for
-///   inbound messages, and the business actor id, then spawns the transport actor
-///
-/// # Returns
-/// A tuple of `(transport_ref, business_ref)` — actor references for both spawned actors.
-pub async fn wire<
-    Transport,
-    Inbound,
-    Outbound,
-    DomainError,
-    Business,
-    BusinessCtor,
-    TransportCtor,
->(
-    business_ctor: BusinessCtor,
-    transport_ctor: TransportCtor,
-) -> (ActorRef<Transport>, ActorRef<Business>)
-where
-    Transport: TransportActor<Outbound, DomainError>,
-    Inbound: Send + 'static,
-    Outbound: Send + 'static,
-    DomainError: Send + 'static,
-    Business: Actor + Message<Inbound> + Send + 'static,
-    BusinessCtor: FnOnce(PreparedActor<Business>, Recipient<Result<Outbound, DomainError>>),
-    TransportCtor:
-        FnOnce(PreparedActor<Transport>, Recipient<Inbound>),
-{
-    let prepared_business: PreparedActor<Business> = Spawn::prepare();
-    let prepared_transport: PreparedActor<Transport> = Spawn::prepare();
-
-    let business_ref = prepared_business.actor_ref().clone();
-    let transport_ref = prepared_transport.actor_ref().clone();
-
-    transport_ref.link(&business_ref).await;
-    business_ref.link(&transport_ref).await;
-
-    let recipient = transport_ref.clone().recipient();
-    business_ctor(prepared_business, recipient);
-    let business_recipient = business_ref.clone().recipient();
-    transport_ctor(prepared_transport, business_recipient);
-
-
-    (transport_ref, business_ref)
-}
+pub mod grpc;

server/crates/arbiter-proto/src/transport/grpc.rs

@@ -0,0 +1,106 @@
+use async_trait::async_trait;
+use futures::StreamExt;
+use tokio::sync::mpsc;
+use tokio_stream::wrappers::ReceiverStream;
+
+use super::{Bi, Receiver, Sender};
+
+pub struct GrpcSender<Outbound> {
+    tx: mpsc::Sender<Result<Outbound, tonic::Status>>,
+}
+
+#[async_trait]
+impl<Outbound> Sender<Result<Outbound, tonic::Status>> for GrpcSender<Outbound>
+where
+    Outbound: Send + Sync + 'static,
+{
+    async fn send(&mut self, item: Result<Outbound, tonic::Status>) -> Result<(), super::Error> {
+        self.tx
+            .send(item)
+            .await
+            .map_err(|_| super::Error::ChannelClosed)
+    }
+}
+
+pub struct GrpcReceiver<Inbound> {
+    rx: tonic::Streaming<Inbound>,
+}
+#[async_trait]
+impl<Inbound> Receiver<Result<Inbound, tonic::Status>> for GrpcReceiver<Inbound>
+where
+    Inbound: Send + Sync + 'static,
+{
+    async fn recv(&mut self) -> Option<Result<Inbound, tonic::Status>> {
+        self.rx.next().await
+    }
+}
+
+pub struct GrpcBi<Inbound, Outbound> {
+    sender: GrpcSender<Outbound>,
+    receiver: GrpcReceiver<Inbound>,
+}
+
+impl<Inbound, Outbound> GrpcBi<Inbound, Outbound>
+where
+    Inbound: Send + Sync + 'static,
+    Outbound: Send + Sync + 'static,
+{
+    pub fn from_bi_stream(
+        receiver: tonic::Streaming<Inbound>,
+    ) -> (Self, ReceiverStream<Result<Outbound, tonic::Status>>) {
+        let (tx, rx) = mpsc::channel(10);
+        let sender = GrpcSender { tx };
+        let receiver = GrpcReceiver { rx: receiver };
+        let bi = GrpcBi { sender, receiver };
+        (bi, ReceiverStream::new(rx))
+    }
+}
+
+#[async_trait]
+impl<Inbound, Outbound> Sender<Result<Outbound, tonic::Status>> for GrpcBi<Inbound, Outbound>
+where
+    Inbound: Send + Sync + 'static,
+    Outbound: Send + Sync + 'static,
+{
+    async fn send(&mut self, item: Result<Outbound, tonic::Status>) -> Result<(), super::Error> {
+        self.sender.send(item).await
+    }
+}
+
+#[async_trait]
+impl<Inbound, Outbound> Receiver<Result<Inbound, tonic::Status>> for GrpcBi<Inbound, Outbound>
+where
+    Inbound: Send + Sync + 'static,
+    Outbound: Send + Sync + 'static,
+{
+    async fn recv(&mut self) -> Option<Result<Inbound, tonic::Status>> {
+        self.receiver.recv().await
+    }
+}
+
+impl<Inbound, Outbound> Bi<Result<Inbound, tonic::Status>, Result<Outbound, tonic::Status>>
+    for GrpcBi<Inbound, Outbound>
+where
+    Inbound: Send + Sync + 'static,
+    Outbound: Send + Sync + 'static,
+{
+}
+
+impl<Inbound, Outbound>
+    super::SplittableBi<Result<Inbound, tonic::Status>, Result<Outbound, tonic::Status>>
+    for GrpcBi<Inbound, Outbound>
+where
+    Inbound: Send + Sync + 'static,
+    Outbound: Send + Sync + 'static,
+{
+    type Sender = GrpcSender<Outbound>;
+    type Receiver = GrpcReceiver<Inbound>;
+
+    fn split(self) -> (Self::Sender, Self::Receiver) {
+        (self.sender, self.receiver)
+    }
+
+    fn from_parts(sender: Self::Sender, receiver: Self::Receiver) -> Self {
+        GrpcBi { sender, receiver }
+    }
+}

server/crates/arbiter-proto/src/url.rs

@@ -7,6 +7,7 @@ const ARBITER_URL_SCHEME: &str = "arbiter";
 const CERT_QUERY_KEY: &str = "cert";
 const BOOTSTRAP_TOKEN_QUERY_KEY: &str = "bootstrap_token";
 
+#[derive(Debug, Clone)]
 pub struct ArbiterUrl {
     pub host: String,
     pub port: u16,
@@ -20,7 +21,7 @@ impl Display for ArbiterUrl {
             "{ARBITER_URL_SCHEME}://{}:{}?{CERT_QUERY_KEY}={}",
             self.host,
             self.port,
-            BASE64_URL_SAFE.encode(self.ca_cert.to_vec())
+            BASE64_URL_SAFE.encode(&self.ca_cert)
         );
         if let Some(token) = &self.bootstrap_token {
             base.push_str(&format!("&{BOOTSTRAP_TOKEN_QUERY_KEY}={}", token));

server/crates/arbiter-server/Cargo.toml

@@ -5,9 +5,12 @@ edition = "2024"
 repository = "https://git.markettakers.org/MarketTakers/arbiter"
 license = "Apache-2.0"
 
+[lints]
+workspace = true
+
 [dependencies]
-diesel = { version = "2.3.6", features = ["chrono", "returning_clauses_for_sqlite_3_35", "serde_json", "time", "uuid"] }
-diesel-async = { version = "0.7.4", features = [
+diesel = { version = "2.3.7", features = ["chrono", "returning_clauses_for_sqlite_3_35", "serde_json", "time", "uuid"] }
+diesel-async = { version = "0.8.0", features = [
     "bb8",
     "migrations",
     "sqlite",
@@ -22,8 +25,8 @@ tonic.features = ["tls-aws-lc"]
 tokio.workspace = true
 rustls.workspace = true
 smlang.workspace = true
-miette.workspace = true
 thiserror.workspace = true
+fatality = "0.1.1"
 diesel_migrations = { version = "2.3.1", features = ["sqlite"] }
 async-trait.workspace = true
 secrecy = "0.10.3"
@@ -40,8 +43,16 @@ x25519-dalek.workspace = true
 chacha20poly1305 = { version = "0.10.1", features = ["std"] }
 argon2 = { version = "0.5.3", features = ["zeroize"] }
 restructed = "0.2.2"
-strum = { version = "0.27.2", features = ["derive"] }
+strum = { version = "0.28.0", features = ["derive"] }
 pem = "3.0.6"
+k256.workspace = true
+rsa.workspace = true
+sha2.workspace = true
+spki.workspace = true
+alloy.workspace = true
+prost-types.workspace = true
+arbiter-tokens-registry.path = "../arbiter-tokens-registry"
+anyhow = "1.0.102"
 
 [dev-dependencies]
 insta = "1.46.3"

server/crates/arbiter-server/migrations/2026-02-14-171124-0000_init/up.sql

@@ -28,7 +28,7 @@ create table if not exists tls_history (
     id INTEGER not null PRIMARY KEY,
     cert text not null,
     cert_key text not null, -- PEM Encoded private key
-    ca_cert text not null, 
+    ca_cert text not null,
     ca_key text not null, -- PEM Encoded private key
     created_at integer not null default(unixepoch ('now'))
 ) STRICT;
@@ -40,20 +40,154 @@ create table if not exists arbiter_settings (
     tls_id integer references tls_history (id) on delete RESTRICT
 ) STRICT;
 
-insert into arbiter_settings (id) values (1) on conflict do nothing; -- ensure singleton row exists
+insert into arbiter_settings (id) values (1) on conflict do nothing;
+-- ensure singleton row exists
 
 create table if not exists useragent_client (
     id integer not null primary key,
     nonce integer not null default(1), -- used for auth challenge
     public_key blob not null,
+    key_type integer not null default(1), -- 1=Ed25519, 2=ECDSA(secp256k1)
     created_at integer not null default(unixepoch ('now')),
     updated_at integer not null default(unixepoch ('now'))
 ) STRICT;
+create unique index if not exists uniq_useragent_client_public_key on useragent_client (public_key, key_type);
+
+create table if not exists client_metadata (
+    id integer not null primary key,
+    name text not null, -- human-readable name for the client
+    description text, -- optional description for the client
+    version text, -- client version for tracking and debugging
+    created_at integer not null default(unixepoch ('now'))
+) STRICT;
+
+-- created to track history of changes
+create table if not exists client_metadata_history (
+    id integer not null primary key,
+    metadata_id integer not null references client_metadata (id) on delete cascade,
+    client_id integer not null references program_client (id) on delete cascade,
+    created_at integer not null default(unixepoch ('now'))
+) STRICT;
+
+create unique index if not exists uniq_metadata_binding_client on client_metadata_history (client_id);
 
 create table if not exists program_client (
     id integer not null primary key,
     nonce integer not null default(1), -- used for auth challenge
     public_key blob not null,
+    metadata_id integer not null references client_metadata (id) on delete cascade,
     created_at integer not null default(unixepoch ('now')),
     updated_at integer not null default(unixepoch ('now'))
-) STRICT;
+) STRICT;
+
+create unique index if not exists program_client_public_key_unique
+    on program_client (public_key);
+
+create unique index if not exists uniq_program_client_public_key on program_client (public_key);
+
+create table if not exists evm_wallet (
+    id integer not null primary key,
+    address blob not null, -- 20-byte Ethereum address
+    aead_encrypted_id integer not null references aead_encrypted (id) on delete RESTRICT,
+    created_at integer not null default(unixepoch ('now'))
+) STRICT;
+
+create unique index if not exists uniq_evm_wallet_address on evm_wallet (address);
+
+create unique index if not exists uniq_evm_wallet_aead on evm_wallet (aead_encrypted_id);
+
+create table if not exists evm_wallet_access (
+    id integer not null primary key,
+    wallet_id integer not null references evm_wallet (id) on delete cascade,
+    client_id integer not null references program_client (id) on delete cascade,
+    created_at integer not null default(unixepoch ('now'))
+) STRICT;
+
+create unique index if not exists uniq_wallet_access on evm_wallet_access (wallet_id, client_id);
+
+create table if not exists evm_ether_transfer_limit (
+    id integer not null primary key,
+    window_secs integer not null, -- window duration in seconds
+    max_volume blob not null -- big-endian 32-byte U256
+) STRICT;
+
+-- Shared grant properties: client scope, timeframe, fee caps, and rate limit
+create table if not exists evm_basic_grant (
+    id integer not null primary key,
+    wallet_access_id integer not null references evm_wallet_access (id) on delete restrict,
+    chain_id integer not null, -- EIP-155 chain ID
+    valid_from integer, -- unix timestamp (seconds), null = no lower bound
+    valid_until integer, -- unix timestamp (seconds), null = no upper bound
+    max_gas_fee_per_gas blob, -- big-endian 32-byte U256, null = unlimited
+    max_priority_fee_per_gas blob, -- big-endian 32-byte U256, null = unlimited
+    rate_limit_count integer, -- max transactions in window, null = unlimited
+    rate_limit_window_secs integer, -- window duration in seconds, null = unlimited
+    revoked_at integer, -- unix timestamp when revoked, null = still active
+    created_at integer not null default(unixepoch ('now'))
+) STRICT;
+
+-- Shared transaction log for all EVM grants, used for rate limit tracking and auditing
+create table if not exists evm_transaction_log (
+    id integer not null primary key,
+    wallet_access_id integer not null references evm_wallet_access (id) on delete restrict,
+    grant_id integer not null references evm_basic_grant (id) on delete restrict,
+    chain_id integer not null,
+    eth_value blob not null, -- always present on any EVM tx
+    signed_at integer not null default(unixepoch ('now'))
+) STRICT;
+
+create index if not exists idx_evm_basic_grant_access_chain on evm_basic_grant (wallet_access_id, chain_id);
+
+-- ===============================
+-- ERC20 token transfer grant
+-- ===============================
+create table if not exists evm_token_transfer_grant (
+    id integer not null primary key,
+    basic_grant_id integer not null unique references evm_basic_grant (id) on delete cascade,
+    token_contract blob not null, -- 20-byte ERC20 contract address
+    receiver blob -- 20-byte recipient address or null if every recipient allowed
+) STRICT;
+
+-- Per-window volume limits for token transfer grants
+create table if not exists evm_token_transfer_volume_limit (
+    id integer not null primary key,
+    grant_id integer not null references evm_token_transfer_grant (id) on delete cascade,
+    window_secs integer not null, -- window duration in seconds
+    max_volume blob not null -- big-endian 32-byte U256
+) STRICT;
+
+-- Log table for token transfer grant usage
+create table if not exists evm_token_transfer_log (
+    id integer not null primary key,
+    grant_id integer not null references evm_token_transfer_grant (id) on delete restrict,
+    log_id integer not null references evm_transaction_log (id) on delete restrict,
+    chain_id integer not null, -- EIP-155 chain ID
+    token_contract blob not null, -- 20-byte ERC20 contract address
+    recipient_address blob not null, -- 20-byte recipient address
+    value blob not null, -- big-endian 32-byte U256
+    created_at integer not null default(unixepoch ('now'))
+) STRICT;
+
+create index if not exists idx_token_transfer_log_grant on evm_token_transfer_log (grant_id);
+
+create index if not exists idx_token_transfer_log_log_id on evm_token_transfer_log (log_id);
+
+create index if not exists idx_token_transfer_log_chain on evm_token_transfer_log (chain_id);
+
+-- ===============================
+-- Ether transfer grant (uses base log)
+-- ===============================
+create table if not exists evm_ether_transfer_grant (
+    id integer not null primary key,
+    basic_grant_id integer not null unique references evm_basic_grant (id) on delete cascade,
+    limit_id integer not null references evm_ether_transfer_limit (id) on delete restrict
+) STRICT;
+
+-- Specific recipient addresses for an ether transfer grant
+create table if not exists evm_ether_transfer_grant_target (
+    id integer not null primary key,
+    grant_id integer not null references evm_ether_transfer_grant (id) on delete cascade,
+    address blob not null -- 20-byte recipient address
+) STRICT;
+
+create unique index if not exists uniq_ether_transfer_target on evm_ether_transfer_grant_target (grant_id, address);

server/crates/arbiter-server/src/actors/bootstrap.rs

@@ -2,13 +2,8 @@ use arbiter_proto::{BOOTSTRAP_PATH, home_path};
 use diesel::QueryDsl;
 use diesel_async::RunQueryDsl;
 use kameo::{Actor, messages};
-use miette::Diagnostic;
-use rand::{
-    RngExt,
-    distr::{Alphanumeric},
-    make_rng,
-    rngs::StdRng,
-};
+
+use rand::{RngExt, distr::Alphanumeric, make_rng, rngs::StdRng};
 use thiserror::Error;
 
 use crate::db::{self, DatabasePool, schema};
@@ -30,18 +25,15 @@ pub async fn generate_token() -> Result<String, std::io::Error> {
     Ok(token)
 }
 
-#[derive(Error, Debug, Diagnostic)]
+#[derive(Error, Debug)]
 pub enum Error {
     #[error("Database error: {0}")]
-    #[diagnostic(code(arbiter_server::bootstrap::database))]
     Database(#[from] db::PoolError),
 
     #[error("Database query error: {0}")]
-    #[diagnostic(code(arbiter_server::bootstrap::database_query))]
     Query(#[from] diesel::result::Error),
 
     #[error("I/O error: {0}")]
-    #[diagnostic(code(arbiter_server::bootstrap::io))]
     Io(#[from] std::io::Error),
 }
 
@@ -61,7 +53,6 @@ impl Bootstrapper {
 
         drop(conn);
 
-
         let token = if row_count == 0 {
             let token = generate_token().await?;
             Some(token)

server/crates/arbiter-server/src/actors/client.rs

@@ -1,12 +0,0 @@
-use arbiter_proto::{
-    proto::{ClientRequest, ClientResponse},
-    transport::Bi,
-};
-
-use crate::ServerContext;
-
-pub(crate) async fn handle_client(
-    _context: ServerContext,
-    _bistream: impl Bi<ClientRequest, ClientResponse>,
-) {
-}

server/crates/arbiter-server/src/actors/client/auth.rs

@@ -0,0 +1,329 @@
+use arbiter_proto::{
+    ClientMetadata, format_challenge,
+    transport::{Bi, expect_message},
+};
+use chrono::Utc;
+use diesel::{
+    ExpressionMethods as _, OptionalExtension as _, QueryDsl as _, SelectableHelper as _,
+    dsl::insert_into, update,
+};
+use diesel_async::RunQueryDsl as _;
+use ed25519_dalek::{Signature, VerifyingKey};
+use kameo::error::SendError;
+use tracing::error;
+
+use crate::{
+    actors::{
+        client::{ClientConnection, ClientProfile},
+        flow_coordinator::{self, RequestClientApproval},
+    },
+    db::{
+        self,
+        models::{ProgramClientMetadata, SqliteTimestamp},
+        schema::program_client,
+    },
+};
+
+#[derive(thiserror::Error, Debug, Clone, PartialEq, Eq)]
+pub enum Error {
+    #[error("Database pool unavailable")]
+    DatabasePoolUnavailable,
+    #[error("Database operation failed")]
+    DatabaseOperationFailed,
+    #[error("Invalid challenge solution")]
+    InvalidChallengeSolution,
+    #[error("Client approval request failed")]
+    ApproveError(#[from] ApproveError),
+    #[error("Transport error")]
+    Transport,
+}
+
+#[derive(thiserror::Error, Debug, Clone, PartialEq, Eq)]
+pub enum ApproveError {
+    #[error("Internal error")]
+    Internal,
+    #[error("Client connection denied by user agents")]
+    Denied,
+    #[error("Upstream error: {0}")]
+    Upstream(flow_coordinator::ApprovalError),
+}
+
+#[derive(Debug, Clone)]
+pub enum Inbound {
+    AuthChallengeRequest {
+        pubkey: VerifyingKey,
+        metadata: ClientMetadata,
+    },
+    AuthChallengeSolution {
+        signature: Signature,
+    },
+}
+
+#[derive(Debug, Clone)]
+pub enum Outbound {
+    AuthChallenge { pubkey: VerifyingKey, nonce: i32 },
+    AuthSuccess,
+}
+
+pub struct ClientInfo {
+    pub id: i32,
+    pub current_nonce: i32,
+}
+
+/// Atomically reads and increments the nonce for a known client.
+/// Returns `None` if the pubkey is not registered.
+async fn get_client_and_nonce(
+    db: &db::DatabasePool,
+    pubkey: &VerifyingKey,
+) -> Result<Option<ClientInfo>, Error> {
+    let pubkey_bytes = pubkey.as_bytes().to_vec();
+
+    let mut conn = db.get().await.map_err(|e| {
+        error!(error = ?e, "Database pool error");
+        Error::DatabasePoolUnavailable
+    })?;
+
+    conn.exclusive_transaction(|conn| {
+        Box::pin(async move {
+            let Some((client_id, current_nonce)) = program_client::table
+                .filter(program_client::public_key.eq(&pubkey_bytes))
+                .select((program_client::id, program_client::nonce))
+                .first::<(i32, i32)>(conn)
+                .await
+                .optional()?
+            else {
+                return Result::<_, diesel::result::Error>::Ok(None);
+            };
+
+            update(program_client::table)
+                .filter(program_client::public_key.eq(&pubkey_bytes))
+                .set(program_client::nonce.eq(current_nonce + 1))
+                .execute(conn)
+                .await?;
+
+            Ok(Some(ClientInfo {
+                id: client_id,
+                current_nonce,
+            }))
+        })
+    })
+    .await
+    .map_err(|e| {
+        error!(error = ?e, "Database error");
+        Error::DatabaseOperationFailed
+    })
+}
+
+async fn approve_new_client(
+    actors: &crate::actors::GlobalActors,
+    profile: ClientProfile,
+) -> Result<(), Error> {
+    let result = actors
+        .flow_coordinator
+        .ask(RequestClientApproval { client: profile })
+        .await;
+
+    match result {
+        Ok(true) => Ok(()),
+        Ok(false) => Err(Error::ApproveError(ApproveError::Denied)),
+        Err(SendError::HandlerError(e)) => {
+            error!(error = ?e, "Approval upstream error");
+            Err(Error::ApproveError(ApproveError::Upstream(e)))
+        }
+        Err(e) => {
+            error!(error = ?e, "Approval request to flow coordinator failed");
+            Err(Error::ApproveError(ApproveError::Internal))
+        }
+    }
+}
+
+async fn insert_client(
+    db: &db::DatabasePool,
+    pubkey: &VerifyingKey,
+    metadata: &ClientMetadata,
+) -> Result<i32, Error> {
+    use crate::db::schema::{client_metadata, program_client};
+    let mut conn = db.get().await.map_err(|e| {
+        error!(error = ?e, "Database pool error");
+        Error::DatabasePoolUnavailable
+    })?;
+
+    let metadata_id = insert_into(client_metadata::table)
+        .values((
+            client_metadata::name.eq(&metadata.name),
+            client_metadata::description.eq(&metadata.description),
+            client_metadata::version.eq(&metadata.version),
+        ))
+        .returning(client_metadata::id)
+        .get_result::<i32>(&mut conn)
+        .await
+        .map_err(|e| {
+            error!(error = ?e, "Failed to insert client metadata");
+            Error::DatabaseOperationFailed
+        })?;
+
+    let client_id = insert_into(program_client::table)
+        .values((
+            program_client::public_key.eq(pubkey.as_bytes().to_vec()),
+            program_client::metadata_id.eq(metadata_id),
+            program_client::nonce.eq(1), // pre-incremented; challenge uses 0
+        ))
+        .on_conflict_do_nothing()
+        .returning(program_client::id)
+        .get_result::<i32>(&mut conn)
+        .await
+        .map_err(|e| {
+            error!(error = ?e, "Failed to insert client metadata");
+            Error::DatabaseOperationFailed
+        })?;
+
+    Ok(client_id)
+}
+
+async fn sync_client_metadata(
+    db: &db::DatabasePool,
+    client_id: i32,
+    metadata: &ClientMetadata,
+) -> Result<(), Error> {
+    use crate::db::schema::{client_metadata, client_metadata_history};
+
+    let now = SqliteTimestamp(Utc::now());
+
+    let mut conn = db.get().await.map_err(|e| {
+        error!(error = ?e, "Database pool error");
+        Error::DatabasePoolUnavailable
+    })?;
+
+    conn.exclusive_transaction(|conn| {
+        let metadata = metadata.clone();
+        Box::pin(async move {
+            let (current_metadata_id, current): (i32, ProgramClientMetadata) =
+                program_client::table
+                    .find(client_id)
+                    .inner_join(client_metadata::table)
+                    .select((
+                        program_client::metadata_id,
+                        ProgramClientMetadata::as_select(),
+                    ))
+                    .first(conn)
+                    .await?;
+
+            let unchanged = current.name == metadata.name
+                && current.description == metadata.description
+                && current.version == metadata.version;
+            if unchanged {
+                return Ok(());
+            }
+
+            insert_into(client_metadata_history::table)
+                .values((
+                    client_metadata_history::metadata_id.eq(current_metadata_id),
+                    client_metadata_history::client_id.eq(client_id),
+                ))
+                .execute(conn)
+                .await?;
+
+            let metadata_id = insert_into(client_metadata::table)
+                .values((
+                    client_metadata::name.eq(&metadata.name),
+                    client_metadata::description.eq(&metadata.description),
+                    client_metadata::version.eq(&metadata.version),
+                ))
+                .returning(client_metadata::id)
+                .get_result::<i32>(conn)
+                .await?;
+
+            update(program_client::table.find(client_id))
+                .set((
+                    program_client::metadata_id.eq(metadata_id),
+                    program_client::updated_at.eq(now),
+                ))
+                .execute(conn)
+                .await?;
+
+            Ok::<(), diesel::result::Error>(())
+        })
+    })
+    .await
+    .map_err(|e| {
+        error!(error = ?e, "Database error");
+        Error::DatabaseOperationFailed
+    })
+}
+
+async fn challenge_client<T>(
+    transport: &mut T,
+    pubkey: VerifyingKey,
+    nonce: i32,
+) -> Result<(), Error>
+where
+    T: Bi<Inbound, Result<Outbound, Error>> + ?Sized,
+{
+    transport
+        .send(Ok(Outbound::AuthChallenge { pubkey, nonce }))
+        .await
+        .map_err(|e| {
+            error!(error = ?e, "Failed to send auth challenge");
+            Error::Transport
+        })?;
+
+    let signature = expect_message(transport, |req: Inbound| match req {
+        Inbound::AuthChallengeSolution { signature } => Some(signature),
+        _ => None,
+    })
+    .await
+    .map_err(|e| {
+        error!(error = ?e, "Failed to receive challenge solution");
+        Error::Transport
+    })?;
+
+    let formatted = format_challenge(nonce, pubkey.as_bytes());
+
+    pubkey.verify_strict(&formatted, &signature).map_err(|_| {
+        error!("Challenge solution verification failed");
+        Error::InvalidChallengeSolution
+    })?;
+
+    Ok(())
+}
+
+pub async fn authenticate<T>(props: &mut ClientConnection, transport: &mut T) -> Result<i32, Error>
+where
+    T: Bi<Inbound, Result<Outbound, Error>> + Send + ?Sized,
+{
+    let Some(Inbound::AuthChallengeRequest { pubkey, metadata }) = transport.recv().await else {
+        return Err(Error::Transport);
+    };
+
+    let info = match get_client_and_nonce(&props.db, &pubkey).await? {
+        Some(nonce) => nonce,
+        None => {
+            approve_new_client(
+                &props.actors,
+                ClientProfile {
+                    pubkey,
+                    metadata: metadata.clone(),
+                },
+            )
+            .await?;
+            let client_id = insert_client(&props.db, &pubkey, &metadata).await?;
+            ClientInfo {
+                id: client_id,
+                current_nonce: 0,
+            }
+        }
+    };
+
+    sync_client_metadata(&props.db, info.id, &metadata).await?;
+    challenge_client(transport, pubkey, info.current_nonce).await?;
+
+    transport
+        .send(Ok(Outbound::AuthSuccess))
+        .await
+        .map_err(|e| {
+            error!(error = ?e, "Failed to send auth success");
+            Error::Transport
+        })?;
+
+    Ok(info.id)
+}

server/crates/arbiter-server/src/actors/client/mod.rs

@@ -0,0 +1,44 @@
+use arbiter_proto::{ClientMetadata, transport::Bi};
+use kameo::actor::Spawn;
+use tracing::{error, info};
+
+use crate::{
+    actors::{GlobalActors, client::session::ClientSession},
+    db,
+};
+
+#[derive(Debug, Clone)]
+pub struct ClientProfile {
+    pub pubkey: ed25519_dalek::VerifyingKey,
+    pub metadata: ClientMetadata,
+}
+
+pub struct ClientConnection {
+    pub(crate) db: db::DatabasePool,
+    pub(crate) actors: GlobalActors,
+}
+
+impl ClientConnection {
+    pub fn new(db: db::DatabasePool, actors: GlobalActors) -> Self {
+        Self { db, actors }
+    }
+}
+
+pub mod auth;
+pub mod session;
+
+pub async fn connect_client<T>(mut props: ClientConnection, transport: &mut T)
+where
+    T: Bi<auth::Inbound, Result<auth::Outbound, auth::Error>> + Send + ?Sized,
+{
+    match auth::authenticate(&mut props, transport).await {
+        Ok(client_id) => {
+            ClientSession::spawn(ClientSession::new(props, client_id));
+            info!("Client authenticated, session started");
+        }
+        Err(err) => {
+            let _ = transport.send(Err(err.clone())).await;
+            error!(?err, "Authentication failed, closing connection");
+        }
+    }
+}

server/crates/arbiter-server/src/actors/client/session.rs

@@ -0,0 +1,119 @@
+use kameo::{Actor, messages};
+use tracing::error;
+
+use alloy::{consensus::TxEip1559, primitives::Address, signers::Signature};
+
+use crate::{
+    actors::{
+        GlobalActors,
+        client::ClientConnection,
+        evm::{ClientSignTransaction, SignTransactionError},
+        flow_coordinator::RegisterClient,
+        keyholder::KeyHolderState,
+    },
+    db,
+    evm::VetError,
+};
+
+pub struct ClientSession {
+    props: ClientConnection,
+    client_id: i32,
+}
+
+impl ClientSession {
+    pub(crate) fn new(props: ClientConnection, client_id: i32) -> Self {
+        Self { props, client_id }
+    }
+}
+
+#[messages]
+impl ClientSession {
+    #[message]
+    pub(crate) async fn handle_query_vault_state(&mut self) -> Result<KeyHolderState, Error> {
+        use crate::actors::keyholder::GetState;
+
+        let vault_state = match self.props.actors.key_holder.ask(GetState {}).await {
+            Ok(state) => state,
+            Err(err) => {
+                error!(?err, actor = "client", "keyholder.query.failed");
+                return Err(Error::Internal);
+            }
+        };
+
+        Ok(vault_state)
+    }
+
+    #[message]
+    pub(crate) async fn handle_sign_transaction(
+        &mut self,
+        wallet_address: Address,
+        transaction: TxEip1559,
+    ) -> Result<Signature, SignTransactionRpcError> {
+        match self
+            .props
+            .actors
+            .evm
+            .ask(ClientSignTransaction {
+                client_id: self.client_id,
+                wallet_address,
+                transaction,
+            })
+            .await
+        {
+            Ok(signature) => Ok(signature),
+            Err(kameo::error::SendError::HandlerError(SignTransactionError::Vet(vet_error))) => {
+                Err(SignTransactionRpcError::Vet(vet_error))
+            }
+            Err(err) => {
+                error!(?err, "Failed to sign EVM transaction in client session");
+                Err(SignTransactionRpcError::Internal)
+            }
+        }
+    }
+}
+
+impl Actor for ClientSession {
+    type Args = Self;
+
+    type Error = Error;
+
+    async fn on_start(
+        args: Self::Args,
+        this: kameo::prelude::ActorRef<Self>,
+    ) -> Result<Self, Self::Error> {
+        args.props
+            .actors
+            .flow_coordinator
+            .ask(RegisterClient { actor: this })
+            .await
+            .map_err(|_| Error::ConnectionRegistrationFailed)?;
+        Ok(args)
+    }
+}
+
+impl ClientSession {
+    pub fn new_test(db: db::DatabasePool, actors: GlobalActors) -> Self {
+        let props = ClientConnection::new(db, actors);
+        Self {
+            props,
+            client_id: 0,
+        }
+    }
+}
+
+#[derive(Debug, thiserror::Error)]
+pub enum Error {
+    #[error("Connection registration failed")]
+    ConnectionRegistrationFailed,
+    #[error("Internal error")]
+    Internal,
+}
+
+#[derive(Debug, thiserror::Error)]
+pub enum SignTransactionRpcError {
+    #[error("Policy evaluation failed")]
+    Vet(#[from] VetError),
+
+    #[error("Internal error")]
+    Internal,
+}

server/crates/arbiter-server/src/actors/evm/mod.rs

@@ -0,0 +1,256 @@
+use alloy::{consensus::TxEip1559, primitives::Address, signers::Signature};
+use diesel::{
+    ExpressionMethods, OptionalExtension as _, QueryDsl, SelectableHelper as _, dsl::insert_into,
+};
+use diesel_async::RunQueryDsl;
+use kameo::{Actor, actor::ActorRef, messages};
+use rand::{SeedableRng, rng, rngs::StdRng};
+
+use crate::{
+    actors::keyholder::{CreateNew, Decrypt, KeyHolder},
+    db::{
+        DatabaseError, DatabasePool,
+        models::{self, SqliteTimestamp},
+        schema,
+    },
+    evm::{
+        self, RunKind,
+        policies::{
+            FullGrant, Grant, SharedGrantSettings, SpecificGrant, SpecificMeaning,
+            ether_transfer::EtherTransfer, token_transfers::TokenTransfer,
+        },
+    },
+    safe_cell::{SafeCell, SafeCellHandle as _},
+};
+
+pub use crate::evm::safe_signer;
+
+#[derive(Debug, thiserror::Error)]
+pub enum SignTransactionError {
+    #[error("Wallet not found")]
+    WalletNotFound,
+
+    #[error("Database error: {0}")]
+    Database(#[from] DatabaseError),
+
+    #[error("Keyholder error: {0}")]
+    Keyholder(#[from] crate::actors::keyholder::Error),
+
+    #[error("Keyholder mailbox error")]
+    KeyholderSend,
+
+    #[error("Signing error: {0}")]
+    Signing(#[from] alloy::signers::Error),
+
+    #[error("Policy error: {0}")]
+    Vet(#[from] evm::VetError),
+}
+
+#[derive(Debug, thiserror::Error)]
+pub enum Error {
+    #[error("Keyholder error: {0}")]
+    Keyholder(#[from] crate::actors::keyholder::Error),
+
+    #[error("Keyholder mailbox error")]
+    KeyholderSend,
+
+    #[error("Database error: {0}")]
+    Database(#[from] DatabaseError),
+}
+
+#[derive(Actor)]
+pub struct EvmActor {
+    pub keyholder: ActorRef<KeyHolder>,
+    pub db: DatabasePool,
+    pub rng: StdRng,
+    pub engine: evm::Engine,
+}
+
+impl EvmActor {
+    pub fn new(keyholder: ActorRef<KeyHolder>, db: DatabasePool) -> Self {
+        // is it safe to seed rng from system once?
+        // todo: audit
+        let rng = StdRng::from_rng(&mut rng());
+        let engine = evm::Engine::new(db.clone());
+        Self {
+            keyholder,
+            db,
+            rng,
+            engine,
+        }
+    }
+}
+
+#[messages]
+impl EvmActor {
+    #[message]
+    pub async fn generate(&mut self) -> Result<(i32, Address), Error> {
+        let (mut key_cell, address) = safe_signer::generate(&mut self.rng);
+
+        let plaintext = key_cell.read_inline(|reader| SafeCell::new(reader.to_vec()));
+
+        let aead_id: i32 = self
+            .keyholder
+            .ask(CreateNew { plaintext })
+            .await
+            .map_err(|_| Error::KeyholderSend)?;
+
+        let mut conn = self.db.get().await.map_err(DatabaseError::from)?;
+        let wallet_id = insert_into(schema::evm_wallet::table)
+            .values(&models::NewEvmWallet {
+                address: address.as_slice().to_vec(),
+                aead_encrypted_id: aead_id,
+            })
+            .returning(schema::evm_wallet::id)
+            .get_result(&mut conn)
+            .await
+            .map_err(DatabaseError::from)?;
+
+        Ok((wallet_id, address))
+    }
+
+    #[message]
+    pub async fn list_wallets(&self) -> Result<Vec<(i32, Address)>, Error> {
+        let mut conn = self.db.get().await.map_err(DatabaseError::from)?;
+        let rows: Vec<models::EvmWallet> = schema::evm_wallet::table
+            .select(models::EvmWallet::as_select())
+            .load(&mut conn)
+            .await
+            .map_err(DatabaseError::from)?;
+
+        Ok(rows
+            .into_iter()
+            .map(|w| (w.id, Address::from_slice(&w.address)))
+            .collect())
+    }
+}
+
+#[messages]
+impl EvmActor {
+    #[message]
+    pub async fn useragent_create_grant(
+        &mut self,
+        basic: SharedGrantSettings,
+        grant: SpecificGrant,
+    ) -> Result<i32, DatabaseError> {
+        match grant {
+            SpecificGrant::EtherTransfer(settings) => {
+                self.engine
+                    .create_grant::<EtherTransfer>(FullGrant {
+                        basic,
+                        specific: settings,
+                    })
+                    .await
+            }
+            SpecificGrant::TokenTransfer(settings) => {
+                self.engine
+                    .create_grant::<TokenTransfer>(FullGrant {
+                        basic,
+                        specific: settings,
+                    })
+                    .await
+            }
+        }
+    }
+
+    #[message]
+    pub async fn useragent_delete_grant(&mut self, grant_id: i32) -> Result<(), Error> {
+        let mut conn = self.db.get().await.map_err(DatabaseError::from)?;
+        diesel::update(schema::evm_basic_grant::table)
+            .filter(schema::evm_basic_grant::id.eq(grant_id))
+            .set(schema::evm_basic_grant::revoked_at.eq(SqliteTimestamp::now()))
+            .execute(&mut conn)
+            .await
+            .map_err(DatabaseError::from)?;
+        Ok(())
+    }
+
+    #[message]
+    pub async fn useragent_list_grants(&mut self) -> Result<Vec<Grant<SpecificGrant>>, Error> {
+        Ok(self
+            .engine
+            .list_all_grants()
+            .await
+            .map_err(DatabaseError::from)?)
+    }
+
+    #[message]
+    pub async fn shared_analyze_transaction(
+        &mut self,
+        client_id: i32,
+        wallet_address: Address,
+        transaction: TxEip1559,
+    ) -> Result<SpecificMeaning, SignTransactionError> {
+        let mut conn = self.db.get().await.map_err(DatabaseError::from)?;
+        let wallet = schema::evm_wallet::table
+            .select(models::EvmWallet::as_select())
+            .filter(schema::evm_wallet::address.eq(wallet_address.as_slice()))
+            .first(&mut conn)
+            .await
+            .optional()
+            .map_err(DatabaseError::from)?
+            .ok_or(SignTransactionError::WalletNotFound)?;
+        let wallet_access = schema::evm_wallet_access::table
+            .select(models::EvmWalletAccess::as_select())
+            .filter(schema::evm_wallet_access::wallet_id.eq(wallet.id))
+            .filter(schema::evm_wallet_access::client_id.eq(client_id))
+            .first(&mut conn)
+            .await
+            .optional()
+            .map_err(DatabaseError::from)?
+            .ok_or(SignTransactionError::WalletNotFound)?;
+        drop(conn);
+
+        let meaning = self
+            .engine
+            .evaluate_transaction(wallet_access, transaction.clone(), RunKind::Execution)
+            .await?;
+
+        Ok(meaning)
+    }
+
+    #[message]
+    pub async fn client_sign_transaction(
+        &mut self,
+        client_id: i32,
+        wallet_address: Address,
+        mut transaction: TxEip1559,
+    ) -> Result<Signature, SignTransactionError> {
+        let mut conn = self.db.get().await.map_err(DatabaseError::from)?;
+        let wallet = schema::evm_wallet::table
+            .select(models::EvmWallet::as_select())
+            .filter(schema::evm_wallet::address.eq(wallet_address.as_slice()))
+            .first(&mut conn)
+            .await
+            .optional()
+            .map_err(DatabaseError::from)?
+            .ok_or(SignTransactionError::WalletNotFound)?;
+        let wallet_access = schema::evm_wallet_access::table
+            .select(models::EvmWalletAccess::as_select())
+            .filter(schema::evm_wallet_access::wallet_id.eq(wallet.id))
+            .filter(schema::evm_wallet_access::client_id.eq(client_id))
+            .first(&mut conn)
+            .await
+            .optional()
+            .map_err(DatabaseError::from)?
+            .ok_or(SignTransactionError::WalletNotFound)?;
+        drop(conn);
+
+        let raw_key: SafeCell<Vec<u8>> = self
+            .keyholder
+            .ask(Decrypt {
+                aead_id: wallet.aead_encrypted_id,
+            })
+            .await
+            .map_err(|_| SignTransactionError::KeyholderSend)?;
+
+        let signer = safe_signer::SafeSigner::from_cell(raw_key)?;
+
+        self.engine
+            .evaluate_transaction(wallet_access, transaction.clone(), RunKind::Execution)
+            .await?;
+
+        use alloy::network::TxSignerSync as _;
+        Ok(signer.sign_transaction_sync(&mut transaction)?)
+    }
+}

server/crates/arbiter-server/src/actors/flow_coordinator/client_connect_approval.rs

@@ -0,0 +1,105 @@
+use std::ops::ControlFlow;
+
+use kameo::{
+    Actor, messages,
+    prelude::{ActorId, ActorRef, ActorStopReason, Context, WeakActorRef},
+    reply::ReplySender,
+};
+
+use crate::actors::{
+    client::ClientProfile,
+    flow_coordinator::ApprovalError,
+    user_agent::{UserAgentSession, session::BeginNewClientApproval},
+};
+
+pub struct Args {
+    pub client: ClientProfile,
+    pub user_agents: Vec<ActorRef<UserAgentSession>>,
+    pub reply: ReplySender<Result<bool, ApprovalError>>,
+}
+
+pub struct ClientApprovalController {
+    /// Number of UAs that have not yet responded (approval or denial) or died.
+    pending: usize,
+    /// Number of approvals received so far.
+    approved: usize,
+    reply: Option<ReplySender<Result<bool, ApprovalError>>>,
+}
+
+impl ClientApprovalController {
+    fn send_reply(&mut self, result: Result<bool, ApprovalError>) {
+        if let Some(reply) = self.reply.take() {
+            reply.send(result);
+        }
+    }
+}
+
+impl Actor for ClientApprovalController {
+    type Args = Args;
+    type Error = ();
+
+    async fn on_start(
+        Args {
+            client,
+            mut user_agents,
+            reply,
+        }: Self::Args,
+        actor_ref: ActorRef<Self>,
+    ) -> Result<Self, Self::Error> {
+        let this = Self {
+            pending: user_agents.len(),
+            approved: 0,
+            reply: Some(reply),
+        };
+
+        for user_agent in user_agents.drain(..) {
+            actor_ref.link(&user_agent).await;
+            let _ = user_agent
+                .tell(BeginNewClientApproval {
+                    client: client.clone(),
+                    controller: actor_ref.clone(),
+                })
+                .await;
+        }
+
+        Ok(this)
+    }
+
+    async fn on_link_died(
+        &mut self,
+        _: WeakActorRef<Self>,
+        _: ActorId,
+        _: ActorStopReason,
+    ) -> Result<ControlFlow<ActorStopReason>, Self::Error> {
+        // A linked UA died before responding — counts as a non-approval.
+        self.pending = self.pending.saturating_sub(1);
+        if self.pending == 0 {
+            // At least one UA didn't approve: deny.
+            self.send_reply(Ok(false));
+            return Ok(ControlFlow::Break(ActorStopReason::Normal));
+        }
+        Ok(ControlFlow::Continue(()))
+    }
+}
+
+#[messages]
+impl ClientApprovalController {
+    #[message(ctx)]
+    pub async fn client_approval_answer(&mut self, approved: bool, ctx: &mut Context<Self, ()>) {
+        if !approved {
+            // Denial wins immediately regardless of other pending responses.
+            self.send_reply(Ok(false));
+            ctx.stop();
+            return;
+        }
+
+        self.approved += 1;
+        self.pending = self.pending.saturating_sub(1);
+
+        if self.pending == 0 {
+            // Every connected UA approved.
+            self.send_reply(Ok(true));
+            ctx.stop();
+        }
+    }
+}

server/crates/arbiter-server/src/actors/flow_coordinator/mod.rs

@@ -0,0 +1,118 @@
+use std::{collections::HashMap, ops::ControlFlow};
+
+use kameo::{
+    Actor,
+    actor::{ActorId, ActorRef, Spawn},
+    messages,
+    prelude::{ActorStopReason, Context, WeakActorRef},
+    reply::DelegatedReply,
+};
+use tracing::info;
+
+use crate::actors::{
+    client::{ClientProfile, session::ClientSession},
+    flow_coordinator::client_connect_approval::ClientApprovalController,
+    user_agent::session::UserAgentSession,
+};
+
+pub mod client_connect_approval;
+
+#[derive(Default)]
+pub struct FlowCoordinator {
+    pub user_agents: HashMap<ActorId, ActorRef<UserAgentSession>>,
+    pub clients: HashMap<ActorId, ActorRef<ClientSession>>,
+}
+
+impl Actor for FlowCoordinator {
+    type Args = Self;
+
+    type Error = ();
+
+    async fn on_start(args: Self::Args, _: ActorRef<Self>) -> Result<Self, Self::Error> {
+        Ok(args)
+    }
+
+    async fn on_link_died(
+        &mut self,
+        _: WeakActorRef<Self>,
+        id: ActorId,
+        _: ActorStopReason,
+    ) -> Result<ControlFlow<ActorStopReason>, Self::Error> {
+        if self.user_agents.remove(&id).is_some() {
+            info!(
+                ?id,
+                actor = "FlowCoordinator",
+                event = "useragent.disconnected"
+            );
+        } else if self.clients.remove(&id).is_some() {
+            info!(
+                ?id,
+                actor = "FlowCoordinator",
+                event = "client.disconnected"
+            );
+        } else {
+            info!(
+                ?id,
+                actor = "FlowCoordinator",
+                event = "unknown.actor.disconnected"
+            );
+        }
+        Ok(ControlFlow::Continue(()))
+    }
+}
+
+#[derive(Debug, thiserror::Error, Clone, PartialEq, Eq, Hash)]
+pub enum ApprovalError {
+    #[error("No user agents connected")]
+    NoUserAgentsConnected,
+}
+
+#[messages]
+impl FlowCoordinator {
+    #[message(ctx)]
+    pub async fn register_user_agent(
+        &mut self,
+        actor: ActorRef<UserAgentSession>,
+        ctx: &mut Context<Self, ()>,
+    ) {
+        info!(id = %actor.id(), actor = "FlowCoordinator", event = "useragent.connected");
+        ctx.actor_ref().link(&actor).await;
+        self.user_agents.insert(actor.id(), actor);
+    }
+
+    #[message(ctx)]
+    pub async fn register_client(
+        &mut self,
+        actor: ActorRef<ClientSession>,
+        ctx: &mut Context<Self, ()>,
+    ) {
+        info!(id = %actor.id(), actor = "FlowCoordinator", event = "client.connected");
+        ctx.actor_ref().link(&actor).await;
+        self.clients.insert(actor.id(), actor);
+    }
+
+    #[message(ctx)]
+    pub async fn request_client_approval(
+        &mut self,
+        client: ClientProfile,
+        ctx: &mut Context<Self, DelegatedReply<Result<bool, ApprovalError>>>,
+    ) -> DelegatedReply<Result<bool, ApprovalError>> {
+        let (reply, Some(reply_sender)) = ctx.reply_sender() else {
+            unreachable!("Expected `request_client_approval` to have callback channel");
+        };
+
+        let refs: Vec<_> = self.user_agents.values().cloned().collect();
+        if refs.is_empty() {
+            reply_sender.send(Err(ApprovalError::NoUserAgentsConnected));
+            return reply;
+        }
+
+        ClientApprovalController::spawn(client_connect_approval::Args {
+            client,
+            user_agents: refs,
+            reply: reply_sender,
+        });
+
+        reply
+    }
+}

server/crates/arbiter-server/src/actors/keyholder/encryption/v1.rs

@@ -5,12 +5,13 @@ use chacha20poly1305::{
     AeadInPlace, Key, KeyInit as _, XChaCha20Poly1305, XNonce,
     aead::{AeadMut, Error, Payload},
 };
-use memsafe::MemSafe;
 use rand::{
     Rng as _, SeedableRng,
     rngs::{StdRng, SysRng},
 };
 
+use crate::safe_cell::{SafeCell, SafeCellHandle as _};
+
 pub const ROOT_KEY_TAG: &[u8] = "arbiter/seal/v1".as_bytes();
 pub const TAG: &[u8] = "arbiter/private-key/v1".as_bytes();
 
@@ -47,40 +48,37 @@ impl<'a> TryFrom<&'a [u8]> for Nonce {
     }
 }
 
-pub struct KeyCell(pub MemSafe<Key>);
-impl From<MemSafe<Key>> for KeyCell {
-    fn from(value: MemSafe<Key>) -> Self {
+pub struct KeyCell(pub SafeCell<Key>);
+impl From<SafeCell<Key>> for KeyCell {
+    fn from(value: SafeCell<Key>) -> Self {
         Self(value)
     }
 }
-impl TryFrom<MemSafe<Vec<u8>>> for KeyCell {
+impl TryFrom<SafeCell<Vec<u8>>> for KeyCell {
     type Error = ();
 
-    fn try_from(mut value: MemSafe<Vec<u8>>) -> Result<Self, Self::Error> {
-        let value = value.read().unwrap();
+    fn try_from(mut value: SafeCell<Vec<u8>>) -> Result<Self, Self::Error> {
+        let value = value.read();
         if value.len() != size_of::<Key>() {
             return Err(());
         }
-        let mut cell = MemSafe::new(Key::default()).unwrap();
-        {
-            let mut cell_write = cell.write().unwrap();
-            let cell_slice: &mut [u8] = cell_write.as_mut();
-            cell_slice.copy_from_slice(&value);
-        }
+        let cell = SafeCell::new_inline(|cell_write: &mut Key| {
+            cell_write.copy_from_slice(&value);
+        });
         Ok(Self(cell))
     }
 }
 
 impl KeyCell {
     pub fn new_secure_random() -> Self {
-        let mut key = MemSafe::new(Key::default()).unwrap();
-        {
-            let mut key_buffer = key.write().unwrap();
-            let key_buffer: &mut [u8] = key_buffer.as_mut();
-
+        let key = SafeCell::new_inline(|key_buffer: &mut Key| {
+            #[allow(
+                clippy::unwrap_used,
+                reason = "Rng failure is unrecoverable and should panic"
+            )]
             let mut rng = StdRng::try_from_rng(&mut SysRng).unwrap();
             rng.fill_bytes(key_buffer);
-        }
+        });
 
         key.into()
     }
@@ -91,7 +89,7 @@ impl KeyCell {
         associated_data: &[u8],
         mut buffer: impl AsMut<Vec<u8>>,
     ) -> Result<(), Error> {
-        let key_reader = self.0.read().unwrap();
+        let key_reader = self.0.read();
         let key_ref = key_reader.deref();
         let cipher = XChaCha20Poly1305::new(key_ref);
         let nonce = XNonce::from_slice(nonce.0.as_ref());
@@ -102,13 +100,13 @@ impl KeyCell {
         &mut self,
         nonce: &Nonce,
         associated_data: &[u8],
-        buffer: &mut MemSafe<Vec<u8>>,
+        buffer: &mut SafeCell<Vec<u8>>,
     ) -> Result<(), Error> {
-        let key_reader = self.0.read().unwrap();
+        let key_reader = self.0.read();
         let key_ref = key_reader.deref();
         let cipher = XChaCha20Poly1305::new(key_ref);
         let nonce = XNonce::from_slice(nonce.0.as_ref());
-        let mut buffer = buffer.write().unwrap();
+        let mut buffer = buffer.write();
         let buffer: &mut Vec<u8> = buffer.as_mut();
         cipher.decrypt_in_place(nonce, associated_data, buffer)
     }
@@ -119,7 +117,7 @@ impl KeyCell {
         associated_data: &[u8],
         plaintext: impl AsRef<[u8]>,
     ) -> Result<Vec<u8>, Error> {
-        let key_reader = self.0.read().unwrap();
+        let key_reader = self.0.read();
         let key_ref = key_reader.deref();
         let mut cipher = XChaCha20Poly1305::new(key_ref);
         let nonce = XNonce::from_slice(nonce.0.as_ref());
@@ -139,6 +137,10 @@ pub type Salt = [u8; ArgonSalt::RECOMMENDED_LENGTH];
 
 pub fn generate_salt() -> Salt {
     let mut salt = Salt::default();
+    #[allow(
+        clippy::unwrap_used,
+        reason = "Rng failure is unrecoverable and should panic"
+    )]
     let mut rng = StdRng::try_from_rng(&mut SysRng).unwrap();
     rng.fill_bytes(&mut salt);
     salt
@@ -146,19 +148,23 @@ pub fn generate_salt() -> Salt {
 
 /// User password might be of different length, have not enough entropy, etc...
 /// Derive a fixed-length key from the password using Argon2id, which is designed for password hashing and key derivation.
-pub fn derive_seal_key(mut password: MemSafe<Vec<u8>>, salt: &Salt) -> KeyCell {
+pub fn derive_seal_key(mut password: SafeCell<Vec<u8>>, salt: &Salt) -> KeyCell {
+    #[allow(clippy::unwrap_used)]
     let params = argon2::Params::new(262_144, 3, 4, None).unwrap();
     let hasher = Argon2::new(Algorithm::Argon2id, argon2::Version::V0x13, params);
-    let mut key = MemSafe::new(Key::default()).unwrap();
-    {
-        let password_source = password.read().unwrap();
-        let mut key_buffer = key.write().unwrap();
+    let mut key = SafeCell::new(Key::default());
+    password.read_inline(|password_source| {
+        let mut key_buffer = key.write();
         let key_buffer: &mut [u8] = key_buffer.as_mut();
 
+        #[allow(
+            clippy::unwrap_used,
+            reason = "Better fail completely than return a weak key"
+        )]
         hasher
             .hash_password_into(password_source.deref(), salt, key_buffer)
             .unwrap();
-    }
+    });
 
     key.into()
 }
@@ -166,20 +172,20 @@ pub fn derive_seal_key(mut password: MemSafe<Vec<u8>>, salt: &Salt) -> KeyCell {
 #[cfg(test)]
 mod tests {
     use super::*;
-    use memsafe::MemSafe;
+    use crate::safe_cell::SafeCell;
 
     #[test]
     pub fn derive_seal_key_deterministic() {
         static PASSWORD: &[u8] = b"password";
-        let password = MemSafe::new(PASSWORD.to_vec()).unwrap();
-        let password2 = MemSafe::new(PASSWORD.to_vec()).unwrap();
+        let password = SafeCell::new(PASSWORD.to_vec());
+        let password2 = SafeCell::new(PASSWORD.to_vec());
         let salt = generate_salt();
 
         let mut key1 = derive_seal_key(password, &salt);
         let mut key2 = derive_seal_key(password2, &salt);
 
-        let key1_reader = key1.0.read().unwrap();
-        let key2_reader = key2.0.read().unwrap();
+        let key1_reader = key1.0.read();
+        let key2_reader = key2.0.read();
 
         assert_eq!(key1_reader.deref(), key2_reader.deref());
     }
@@ -187,11 +193,11 @@ mod tests {
     #[test]
     pub fn successful_derive() {
         static PASSWORD: &[u8] = b"password";
-        let password = MemSafe::new(PASSWORD.to_vec()).unwrap();
+        let password = SafeCell::new(PASSWORD.to_vec());
         let salt = generate_salt();
 
         let mut key = derive_seal_key(password, &salt);
-        let key_reader = key.0.read().unwrap();
+        let key_reader = key.0.read();
         let key_ref = key_reader.deref();
 
         assert_ne!(key_ref.as_slice(), &[0u8; 32][..]);
@@ -200,7 +206,7 @@ mod tests {
     #[test]
     pub fn encrypt_decrypt() {
         static PASSWORD: &[u8] = b"password";
-        let password = MemSafe::new(PASSWORD.to_vec()).unwrap();
+        let password = SafeCell::new(PASSWORD.to_vec());
         let salt = generate_salt();
 
         let mut key = derive_seal_key(password, &salt);
@@ -212,12 +218,12 @@ mod tests {
             .unwrap();
         assert_ne!(buffer, b"secret data");
 
-        let mut buffer = MemSafe::new(buffer).unwrap();
+        let mut buffer = SafeCell::new(buffer);
 
         key.decrypt_in_place(&nonce, associated_data, &mut buffer)
             .unwrap();
 
-        let buffer = buffer.read().unwrap();
+        let buffer = buffer.read();
         assert_eq!(*buffer, b"secret data");
     }
 

server/crates/arbiter-server/src/actors/keyholder/mod.rs

@@ -1,24 +1,28 @@
+use chrono::Utc;
 use diesel::{
     ExpressionMethods as _, OptionalExtension, QueryDsl, SelectableHelper,
     dsl::{insert_into, update},
 };
 use diesel_async::{AsyncConnection, RunQueryDsl};
 use kameo::{Actor, Reply, messages};
-use memsafe::MemSafe;
 use strum::{EnumDiscriminants, IntoDiscriminant};
 use tracing::{error, info};
 
-use crate::db::{
-    self,
-    models::{self, RootKeyHistory},
-    schema::{self},
+use crate::safe_cell::SafeCell;
+use crate::{
+    db::{
+        self,
+        models::{self, RootKeyHistory},
+        schema::{self},
+    },
+    safe_cell::SafeCellHandle as _,
 };
 use encryption::v1::{self, KeyCell, Nonce};
 
 pub mod encryption;
 
 #[derive(Default, EnumDiscriminants)]
-#[strum_discriminants(derive(Reply), vis(pub))]
+#[strum_discriminants(derive(Reply), vis(pub), name(KeyHolderState))]
 enum State {
     #[default]
     Unbootstrapped,
@@ -31,36 +35,28 @@ enum State {
     },
 }
 
-#[derive(Debug, thiserror::Error, miette::Diagnostic)]
+#[derive(Debug, thiserror::Error)]
 pub enum Error {
     #[error("Keyholder is already bootstrapped")]
-    #[diagnostic(code(arbiter::keyholder::already_bootstrapped))]
     AlreadyBootstrapped,
     #[error("Keyholder is not bootstrapped")]
-    #[diagnostic(code(arbiter::keyholder::not_bootstrapped))]
     NotBootstrapped,
     #[error("Invalid key provided")]
-    #[diagnostic(code(arbiter::keyholder::invalid_key))]
     InvalidKey,
 
     #[error("Requested aead entry not found")]
-    #[diagnostic(code(arbiter::keyholder::aead_not_found))]
     NotFound,
 
     #[error("Encryption error: {0}")]
-    #[diagnostic(code(arbiter::keyholder::encryption_error))]
     Encryption(#[from] chacha20poly1305::aead::Error),
 
     #[error("Database error: {0}")]
-    #[diagnostic(code(arbiter::keyholder::database_error))]
     DatabaseConnection(#[from] db::PoolError),
 
     #[error("Database transaction error: {0}")]
-    #[diagnostic(code(arbiter::keyholder::database_transaction_error))]
     DatabaseTransaction(#[from] diesel::result::Error),
 
     #[error("Broken database")]
-    #[diagnostic(code(arbiter::keyholder::broken_database))]
     BrokenDatabase,
 }
 
@@ -135,7 +131,7 @@ impl KeyHolder {
     }
 
     #[message]
-    pub async fn bootstrap(&mut self, seal_key_raw: MemSafe<Vec<u8>>) -> Result<(), Error> {
+    pub async fn bootstrap(&mut self, seal_key_raw: SafeCell<Vec<u8>>) -> Result<(), Error> {
         if !matches!(self.state, State::Unbootstrapped) {
             return Err(Error::AlreadyBootstrapped);
         }
@@ -147,16 +143,15 @@ impl KeyHolder {
         let root_key_nonce = v1::Nonce::default();
         let data_encryption_nonce = v1::Nonce::default();
 
-        let root_key_ciphertext: Vec<u8> = {
-            let root_key_reader = root_key.0.read().unwrap();
-            let root_key_reader = root_key_reader.as_slice();
+        let root_key_ciphertext: Vec<u8> = root_key.0.read_inline(|reader| {
+            let root_key_reader = reader.as_slice();
             seal_key
                 .encrypt(&root_key_nonce, v1::ROOT_KEY_TAG, root_key_reader)
                 .map_err(|err| {
                     error!(?err, "Fatal bootstrap error");
                     Error::Encryption(err)
-                })?
-        };
+                })
+        })?;
 
         let mut conn = self.db.get().await?;
 
@@ -198,7 +193,7 @@ impl KeyHolder {
     }
 
     #[message]
-    pub async fn try_unseal(&mut self, seal_key_raw: MemSafe<Vec<u8>>) -> Result<(), Error> {
+    pub async fn try_unseal(&mut self, seal_key_raw: SafeCell<Vec<u8>>) -> Result<(), Error> {
         let State::Sealed {
             root_key_history_id,
         } = &self.state
@@ -211,7 +206,6 @@ impl KeyHolder {
             let mut conn = self.db.get().await?;
             schema::root_key_history::table
                 .filter(schema::root_key_history::id.eq(*root_key_history_id))
-                .select(schema::root_key_history::data_encryption_nonce)
                 .select(RootKeyHistory::as_select())
                 .first(&mut conn)
                 .await?
@@ -224,7 +218,7 @@ impl KeyHolder {
         })?;
         let mut seal_key = v1::derive_seal_key(seal_key_raw, &salt);
 
-        let mut root_key = MemSafe::new(current_key.ciphertext.clone()).unwrap();
+        let mut root_key = SafeCell::new(current_key.ciphertext.clone());
 
         let nonce = v1::Nonce::try_from(current_key.root_key_encryption_nonce.as_slice()).map_err(
             |_| {
@@ -255,7 +249,7 @@ impl KeyHolder {
 
     // Decrypts the `aead_encrypted` entry with the given ID and returns the plaintext
     #[message]
-    pub async fn decrypt(&mut self, aead_id: i32) -> Result<MemSafe<Vec<u8>>, Error> {
+    pub async fn decrypt(&mut self, aead_id: i32) -> Result<SafeCell<Vec<u8>>, Error> {
         let State::Unsealed { root_key, .. } = &mut self.state else {
             return Err(Error::NotBootstrapped);
         };
@@ -278,14 +272,14 @@ impl KeyHolder {
             );
             Error::BrokenDatabase
         })?;
-        let mut output = MemSafe::new(row.ciphertext).unwrap();
+        let mut output = SafeCell::new(row.ciphertext);
         root_key.decrypt_in_place(&nonce, v1::TAG, &mut output)?;
         Ok(output)
     }
 
     // Creates new `aead_encrypted` entry in the database and returns it's ID
     #[message]
-    pub async fn create_new(&mut self, mut plaintext: MemSafe<Vec<u8>>) -> Result<i32, Error> {
+    pub async fn create_new(&mut self, mut plaintext: SafeCell<Vec<u8>>) -> Result<i32, Error> {
         let State::Unsealed {
             root_key,
             root_key_history_id,
@@ -298,7 +292,7 @@ impl KeyHolder {
         // Borrow checker note: &mut borrow a few lines above is disjoint from this field
         let nonce = Self::get_new_nonce(&self.db, *root_key_history_id).await?;
 
-        let mut ciphertext_buffer = plaintext.write().unwrap();
+        let mut ciphertext_buffer = plaintext.write();
         let ciphertext_buffer: &mut Vec<u8> = ciphertext_buffer.as_mut();
         root_key.encrypt_in_place(&nonce, v1::TAG, &mut *ciphertext_buffer)?;
 
@@ -312,7 +306,7 @@ impl KeyHolder {
                 current_nonce: nonce.to_vec(),
                 schema_version: 1,
                 associated_root_key_id: *root_key_history_id,
-                created_at: chrono::Utc::now().timestamp() as i32,
+                created_at: Utc::now().into(),
             })
             .returning(schema::aead_encrypted::id)
             .get_result(&mut conn)
@@ -322,7 +316,7 @@ impl KeyHolder {
     }
 
     #[message]
-    pub fn get_state(&self) -> StateDiscriminants {
+    pub fn get_state(&self) -> KeyHolderState {
         self.state.discriminant()
     }
 
@@ -345,17 +339,19 @@ impl KeyHolder {
 #[cfg(test)]
 mod tests {
     use diesel::SelectableHelper;
-    
-    use diesel_async::RunQueryDsl;
-    use memsafe::MemSafe;
 
-    use crate::db::{self};
+    use diesel_async::RunQueryDsl;
+
+    use crate::{
+        db::{self},
+        safe_cell::SafeCell,
+    };
 
     use super::*;
 
     async fn bootstrapped_actor(db: &db::DatabasePool) -> KeyHolder {
         let mut actor = KeyHolder::new(db.clone()).await.unwrap();
-        let seal_key = MemSafe::new(b"test-seal-key".to_vec()).unwrap();
+        let seal_key = SafeCell::new(b"test-seal-key".to_vec());
         actor.bootstrap(seal_key).await.unwrap();
         actor
     }
@@ -390,7 +386,7 @@ mod tests {
         assert_eq!(root_row.data_encryption_nonce, n2.to_vec());
 
         let id = actor
-            .create_new(MemSafe::new(b"post-interleave".to_vec()).unwrap())
+            .create_new(SafeCell::new(b"post-interleave".to_vec()))
             .await
             .unwrap();
         let row: models::AeadEncrypted = schema::aead_encrypted::table

server/crates/arbiter-server/src/actors/mod.rs

@@ -1,25 +1,27 @@
 use kameo::actor::{ActorRef, Spawn};
-use miette::Diagnostic;
 use thiserror::Error;
 
 use crate::{
-    actors::{bootstrap::Bootstrapper, keyholder::KeyHolder},
+    actors::{
+        bootstrap::Bootstrapper, evm::EvmActor, flow_coordinator::FlowCoordinator,
+        keyholder::KeyHolder,
+    },
     db,
 };
 
 pub mod bootstrap;
 pub mod client;
+mod evm;
+pub mod flow_coordinator;
 pub mod keyholder;
 pub mod user_agent;
 
-#[derive(Error, Debug, Diagnostic)]
+#[derive(Error, Debug)]
 pub enum SpawnError {
     #[error("Failed to spawn Bootstrapper actor")]
-    #[diagnostic(code(SpawnError::Bootstrapper))]
     Bootstrapper(#[from] bootstrap::Error),
 
     #[error("Failed to spawn KeyHolder actor")]
-    #[diagnostic(code(SpawnError::KeyHolder))]
     KeyHolder(#[from] keyholder::Error),
 }
 
@@ -28,13 +30,18 @@ pub enum SpawnError {
 pub struct GlobalActors {
     pub key_holder: ActorRef<KeyHolder>,
     pub bootstrapper: ActorRef<Bootstrapper>,
+    pub flow_coordinator: ActorRef<FlowCoordinator>,
+    pub evm: ActorRef<EvmActor>,
 }
 
 impl GlobalActors {
     pub async fn spawn(db: db::DatabasePool) -> Result<Self, SpawnError> {
+        let key_holder = KeyHolder::spawn(KeyHolder::new(db.clone()).await?);
         Ok(Self {
             bootstrapper: Bootstrapper::spawn(Bootstrapper::new(&db).await?),
-            key_holder: KeyHolder::spawn(KeyHolder::new(db.clone()).await?),
+            evm: EvmActor::spawn(EvmActor::new(key_holder.clone(), db)),
+            key_holder,
+            flow_coordinator: FlowCoordinator::spawn(FlowCoordinator::default()),
         })
     }
 }

server/crates/arbiter-server/src/actors/user_agent/auth.rs

@@ -0,0 +1,101 @@
+use arbiter_proto::transport::Bi;
+use tracing::error;
+
+use crate::actors::user_agent::{
+    AuthPublicKey, UserAgentConnection,
+    auth::state::{AuthContext, AuthStateMachine},
+};
+
+mod state;
+use state::*;
+
+#[derive(Debug, Clone)]
+pub enum Inbound {
+    AuthChallengeRequest {
+        pubkey: AuthPublicKey,
+        bootstrap_token: Option<String>,
+    },
+    AuthChallengeSolution {
+        signature: Vec<u8>,
+    },
+}
+
+#[derive(Debug)]
+pub enum Error {
+    UnregisteredPublicKey,
+    InvalidChallengeSolution,
+    InvalidBootstrapToken,
+    Internal { details: String },
+    Transport,
+}
+
+impl Error {
+    fn internal(details: impl Into<String>) -> Self {
+        Self::Internal {
+            details: details.into(),
+        }
+    }
+}
+
+#[derive(Debug, Clone)]
+pub enum Outbound {
+    AuthChallenge { nonce: i32 },
+    AuthSuccess,
+}
+
+fn parse_auth_event(payload: Inbound) -> AuthEvents {
+    match payload {
+        Inbound::AuthChallengeRequest {
+            pubkey,
+            bootstrap_token: None,
+        } => AuthEvents::AuthRequest(ChallengeRequest { pubkey }),
+        Inbound::AuthChallengeRequest {
+            pubkey,
+            bootstrap_token: Some(token),
+        } => AuthEvents::BootstrapAuthRequest(BootstrapAuthRequest { pubkey, token }),
+        Inbound::AuthChallengeSolution { signature } => {
+            AuthEvents::ReceivedSolution(ChallengeSolution {
+                solution: signature,
+            })
+        }
+    }
+}
+
+pub async fn authenticate<T>(
+    props: &mut UserAgentConnection,
+    transport: T,
+) -> Result<AuthPublicKey, Error>
+where
+    T: Bi<Inbound, Result<Outbound, Error>> + Send,
+{
+    let mut state = AuthStateMachine::new(AuthContext::new(props, transport));
+
+    loop {
+        // `state` holds a mutable reference to `props` so we can't access it directly here
+        let Some(payload) = state.context_mut().transport.recv().await else {
+            return Err(Error::Transport);
+        };
+
+        match state.process_event(parse_auth_event(payload)).await {
+            Ok(AuthStates::AuthOk(key)) => return Ok(key.clone()),
+            Err(AuthError::ActionFailed(err)) => {
+                error!(?err, "State machine action failed");
+                return Err(err);
+            }
+            Err(AuthError::GuardFailed(err)) => {
+                error!(?err, "State machine guard failed");
+                return Err(err);
+            }
+            Err(AuthError::InvalidEvent) => {
+                error!("Invalid event for current state");
+                return Err(Error::InvalidChallengeSolution);
+            }
+            Err(AuthError::TransitionsFailed) => {
+                error!("Invalid state transition");
+                return Err(Error::InvalidChallengeSolution);
+            }
+
+            _ => (),
+        }
+    }
+}

server/crates/arbiter-server/src/actors/user_agent/auth/state.rs

@@ -0,0 +1,225 @@
+use arbiter_proto::transport::Bi;
+use diesel::{ExpressionMethods as _, OptionalExtension as _, QueryDsl, update};
+use diesel_async::RunQueryDsl;
+use tracing::error;
+
+use super::Error;
+use crate::{
+    actors::{
+        bootstrap::ConsumeToken,
+        user_agent::{AuthPublicKey, UserAgentConnection, auth::Outbound},
+    },
+    db::schema,
+};
+
+pub struct ChallengeRequest {
+    pub pubkey: AuthPublicKey,
+}
+
+pub struct BootstrapAuthRequest {
+    pub pubkey: AuthPublicKey,
+    pub token: String,
+}
+
+pub struct ChallengeContext {
+    pub challenge_nonce: i32,
+    pub key: AuthPublicKey,
+}
+
+pub struct ChallengeSolution {
+    pub solution: Vec<u8>,
+}
+
+smlang::statemachine!(
+    name: Auth,
+    custom_error: true,
+    transitions: {
+        *Init + AuthRequest(ChallengeRequest) / async prepare_challenge = SentChallenge(ChallengeContext),
+        Init + BootstrapAuthRequest(BootstrapAuthRequest) / async verify_bootstrap_token = AuthOk(AuthPublicKey),
+        SentChallenge(ChallengeContext) + ReceivedSolution(ChallengeSolution) / async verify_solution = AuthOk(AuthPublicKey),
+    }
+);
+
+async fn create_nonce(db: &crate::db::DatabasePool, pubkey_bytes: &[u8]) -> Result<i32, Error> {
+    let mut db_conn = db.get().await.map_err(|e| {
+        error!(error = ?e, "Database pool error");
+        Error::internal("Database unavailable")
+    })?;
+    db_conn
+        .exclusive_transaction(|conn| {
+            Box::pin(async move {
+                let current_nonce = schema::useragent_client::table
+                    .filter(schema::useragent_client::public_key.eq(pubkey_bytes.to_vec()))
+                    .select(schema::useragent_client::nonce)
+                    .first::<i32>(conn)
+                    .await?;
+
+                update(schema::useragent_client::table)
+                    .filter(schema::useragent_client::public_key.eq(pubkey_bytes.to_vec()))
+                    .set(schema::useragent_client::nonce.eq(current_nonce + 1))
+                    .execute(conn)
+                    .await?;
+
+                Result::<_, diesel::result::Error>::Ok(current_nonce)
+            })
+        })
+        .await
+        .optional()
+        .map_err(|e| {
+            error!(error = ?e, "Database error");
+            Error::internal("Database operation failed")
+        })?
+        .ok_or_else(|| {
+            error!(?pubkey_bytes, "Public key not found in database");
+            Error::UnregisteredPublicKey
+        })
+}
+
+async fn register_key(db: &crate::db::DatabasePool, pubkey: &AuthPublicKey) -> Result<(), Error> {
+    let pubkey_bytes = pubkey.to_stored_bytes();
+    let key_type = pubkey.key_type();
+    let mut conn = db.get().await.map_err(|e| {
+        error!(error = ?e, "Database pool error");
+        Error::internal("Database unavailable")
+    })?;
+
+    diesel::insert_into(schema::useragent_client::table)
+        .values((
+            schema::useragent_client::public_key.eq(pubkey_bytes),
+            schema::useragent_client::nonce.eq(1),
+            schema::useragent_client::key_type.eq(key_type),
+        ))
+        .execute(&mut conn)
+        .await
+        .map_err(|e| {
+            error!(error = ?e, "Database error");
+            Error::internal("Database operation failed")
+        })?;
+
+    Ok(())
+}
+
+pub struct AuthContext<'a, T> {
+    pub(super) conn: &'a mut UserAgentConnection,
+    pub(super) transport: T,
+}
+
+impl<'a, T> AuthContext<'a, T> {
+    pub fn new(conn: &'a mut UserAgentConnection, transport: T) -> Self {
+        Self { conn, transport }
+    }
+}
+
+impl<T> AuthStateMachineContext for AuthContext<'_, T>
+where
+    T: Bi<super::Inbound, Result<super::Outbound, Error>> + Send,
+{
+    type Error = Error;
+
+    async fn prepare_challenge(
+        &mut self,
+        ChallengeRequest { pubkey }: ChallengeRequest,
+    ) -> Result<ChallengeContext, Self::Error> {
+        let stored_bytes = pubkey.to_stored_bytes();
+        let nonce = create_nonce(&self.conn.db, &stored_bytes).await?;
+
+        self.transport
+            .send(Ok(Outbound::AuthChallenge { nonce }))
+            .await
+            .map_err(|e| {
+                error!(?e, "Failed to send auth challenge");
+                Error::Transport
+            })?;
+
+        Ok(ChallengeContext {
+            challenge_nonce: nonce,
+            key: pubkey,
+        })
+    }
+
+    #[allow(missing_docs)]
+    #[allow(clippy::result_unit_err)]
+    async fn verify_bootstrap_token(
+        &mut self,
+        BootstrapAuthRequest { pubkey, token }: BootstrapAuthRequest,
+    ) -> Result<AuthPublicKey, Self::Error> {
+        let token_ok: bool = self
+            .conn
+            .actors
+            .bootstrapper
+            .ask(ConsumeToken {
+                token: token.clone(),
+            })
+            .await
+            .map_err(|e| {
+                error!(?e, "Failed to consume bootstrap token");
+                Error::internal("Failed to consume bootstrap token")
+            })?;
+
+        if !token_ok {
+            error!("Invalid bootstrap token provided");
+            return Err(Error::InvalidBootstrapToken);
+        }
+
+        register_key(&self.conn.db, &pubkey).await?;
+
+        self.transport
+            .send(Ok(Outbound::AuthSuccess))
+            .await
+            .map_err(|_| Error::Transport)?;
+
+        Ok(pubkey)
+    }
+
+    #[allow(missing_docs)]
+    #[allow(clippy::unused_unit)]
+    async fn verify_solution(
+        &mut self,
+        ChallengeContext {
+            challenge_nonce,
+            key,
+        }: &ChallengeContext,
+        ChallengeSolution { solution }: ChallengeSolution,
+    ) -> Result<AuthPublicKey, Self::Error> {
+        let formatted = arbiter_proto::format_challenge(*challenge_nonce, &key.to_stored_bytes());
+
+        let valid = match key {
+            AuthPublicKey::Ed25519(vk) => {
+                let sig = solution.as_slice().try_into().map_err(|_| {
+                    error!(?solution, "Invalid Ed25519 signature length");
+                    Error::InvalidChallengeSolution
+                })?;
+                vk.verify_strict(&formatted, &sig).is_ok()
+            }
+            AuthPublicKey::EcdsaSecp256k1(vk) => {
+                use k256::ecdsa::signature::Verifier as _;
+                let sig = k256::ecdsa::Signature::try_from(solution.as_slice()).map_err(|_| {
+                    error!(?solution, "Invalid ECDSA signature bytes");
+                    Error::InvalidChallengeSolution
+                })?;
+                vk.verify(&formatted, &sig).is_ok()
+            }
+            AuthPublicKey::Rsa(pk) => {
+                use rsa::signature::Verifier as _;
+                let verifying_key = rsa::pss::VerifyingKey::<sha2::Sha256>::new(pk.clone());
+                let sig = rsa::pss::Signature::try_from(solution.as_slice()).map_err(|_| {
+                    error!(?solution, "Invalid RSA signature bytes");
+                    Error::InvalidChallengeSolution
+                })?;
+                verifying_key.verify(&formatted, &sig).is_ok()
+            }
+        };
+
+        if !valid {
+            error!("Invalid challenge solution signature");
+            return Err(Error::InvalidChallengeSolution);
+        }
+
+        self.transport
+            .send(Ok(Outbound::AuthSuccess))
+            .await
+            .map_err(|_| Error::Transport)?;
+
+        Ok(key.clone())
+    }
+}

server/crates/arbiter-server/src/actors/user_agent/error.rs

@@ -1,57 +0,0 @@
-use tonic::Status;
-
-use crate::db;
-
-#[derive(Debug, thiserror::Error)]
-pub enum UserAgentError {
-    #[error("Missing payload in request")]
-    MissingPayload,
-
-    #[error("Invalid bootstrap token")]
-    InvalidBootstrapToken,
-
-    #[error("Public key not registered")]
-    PubkeyNotRegistered,
-
-    #[error("Invalid public key format")]
-    InvalidPubkey,
-
-    #[error("Invalid signature length")]
-    InvalidSignatureLength,
-
-    #[error("Invalid challenge solution")]
-    InvalidChallengeSolution,
-
-    #[error("Invalid state for operation")]
-    InvalidState,
-
-    #[error("Actor unavailable")]
-    ActorUnavailable,
-
-    #[error("Database error")]
-    Database(#[from] diesel::result::Error),
-
-    #[error("Database pool error")]
-    DatabasePool(#[from] db::PoolError),
-}
-
-impl From<UserAgentError> for Status {
-    fn from(err: UserAgentError) -> Self {
-        match err {
-            UserAgentError::MissingPayload
-            | UserAgentError::InvalidBootstrapToken
-            | UserAgentError::InvalidPubkey
-            | UserAgentError::InvalidSignatureLength => Status::invalid_argument(err.to_string()),
-
-            UserAgentError::PubkeyNotRegistered | UserAgentError::InvalidChallengeSolution => {
-                Status::unauthenticated(err.to_string())
-            }
-
-            UserAgentError::InvalidState => Status::failed_precondition(err.to_string()),
-
-            UserAgentError::ActorUnavailable
-            | UserAgentError::Database(_)
-            | UserAgentError::DatabasePool(_) => Status::internal(err.to_string()),
-        }
-    }
-}

server/crates/arbiter-server/src/actors/user_agent/mod.rs

@@ -1,401 +1,94 @@
-use std::{ops::DerefMut, sync::Mutex};
-
-use arbiter_proto::proto::{
-    UnsealEncryptedKey, UnsealResult, UnsealStart, UnsealStartResponse, UserAgentRequest,
-    UserAgentResponse,
-    auth::{
-        self, AuthChallengeRequest, AuthOk, ClientMessage as ClientAuthMessage,
-        ServerMessage as AuthServerMessage,
-        client_message::Payload as ClientAuthPayload,
-        server_message::Payload as ServerAuthPayload,
-    },
-    user_agent_request::Payload as UserAgentRequestPayload,
-    user_agent_response::Payload as UserAgentResponsePayload,
-};
-use chacha20poly1305::{AeadInPlace, XChaCha20Poly1305, XNonce, aead::KeyInit};
-use diesel::{ExpressionMethods as _, OptionalExtension as _, QueryDsl, dsl::update};
-use diesel_async::RunQueryDsl;
-use ed25519_dalek::VerifyingKey;
-use kameo::{Actor, actor::Recipient, error::SendError, messages, prelude::Message};
-use memsafe::MemSafe;
-use tracing::{error, info};
-use x25519_dalek::{EphemeralSecret, PublicKey};
-
 use crate::{
-    ServerContext,
-    actors::{
-        GlobalActors,
-        bootstrap::ConsumeToken,
-        keyholder::{self, TryUnseal},
-        user_agent::state::{
-            ChallengeContext, DummyContext, UnsealContext, UserAgentEvents, UserAgentStateMachine,
-            UserAgentStates,
-        },
-    },
-    db::{self, schema},
+    actors::{GlobalActors, client::ClientProfile},
+    db::{self, models::KeyType},
 };
 
-mod error;
-mod state;
-
-pub use error::UserAgentError;
-
-#[derive(Actor)]
-pub struct UserAgentActor {
-    db: db::DatabasePool,
-    actors: GlobalActors,
-    state: UserAgentStateMachine<DummyContext>,
-    transport: Recipient<Result<UserAgentResponse, UserAgentError>>,
+/// Abstraction over Ed25519 / ECDSA-secp256k1 / RSA public keys used during the auth handshake.
+#[derive(Clone, Debug)]
+pub enum AuthPublicKey {
+    Ed25519(ed25519_dalek::VerifyingKey),
+    /// Compressed SEC1 public key; signature bytes are raw 64-byte (r||s).
+    EcdsaSecp256k1(k256::ecdsa::VerifyingKey),
+    /// RSA-2048+ public key (Windows Hello / KeyCredentialManager); signature bytes are PSS+SHA-256.
+    Rsa(rsa::RsaPublicKey),
 }
 
-impl UserAgentActor {
-    pub(crate) fn new(
-        context: ServerContext,
-        transport: Recipient<Result<UserAgentResponse, UserAgentError>>,
-    ) -> Self {
-        Self {
-            db: context.db.clone(),
-            actors: context.actors.clone(),
-            state: UserAgentStateMachine::new(DummyContext),
-            transport,
-        }
-    }
-
-    pub fn new_manual(
-        db: db::DatabasePool,
-        actors: GlobalActors,
-        transport: Recipient<Result<UserAgentResponse, UserAgentError>>,
-    ) -> Self {
-        Self {
-            db,
-            actors,
-            state: UserAgentStateMachine::new(DummyContext),
-            transport,
-        }
-    }
-
-    async fn process_request(&mut self, req: UserAgentRequest) -> Output {
-        let msg = req.payload.ok_or_else(|| {
-            error!(actor = "useragent", "Received message with no payload");
-            UserAgentError::MissingPayload
-        })?;
-
-        match msg {
-            UserAgentRequestPayload::AuthMessage(ClientAuthMessage {
-                payload: Some(ClientAuthPayload::AuthChallengeRequest(req)),
-            }) => self.handle_auth_challenge_request(req).await,
-            UserAgentRequestPayload::AuthMessage(ClientAuthMessage {
-                payload: Some(ClientAuthPayload::AuthChallengeSolution(solution)),
-            }) => self.handle_auth_challenge_solution(solution).await,
-            UserAgentRequestPayload::UnsealStart(unseal_start) => {
-                self.handle_unseal_request(unseal_start).await
-            }
-            UserAgentRequestPayload::UnsealEncryptedKey(unseal_encrypted_key) => {
-                self.handle_unseal_encrypted_key(unseal_encrypted_key).await
-            }
-            _ => Err(UserAgentError::MissingPayload),
-        }
-    }
-
-    fn transition(&mut self, event: UserAgentEvents) -> Result<(), UserAgentError> {
-        self.state.process_event(event).map_err(|e| {
-            error!(?e, "State transition failed");
-            UserAgentError::InvalidState
-        })?;
-        Ok(())
-    }
-
-    async fn auth_with_bootstrap_token(
-        &mut self,
-        pubkey: ed25519_dalek::VerifyingKey,
-        token: String,
-    ) -> Output {
-        let token_ok: bool = self
-            .actors
-            .bootstrapper
-            .ask(ConsumeToken { token })
-            .await
-            .map_err(|e| {
-                error!(?pubkey, "Failed to consume bootstrap token: {e}");
-                UserAgentError::ActorUnavailable
-            })?;
-
-        if !token_ok {
-            error!(?pubkey, "Invalid bootstrap token provided");
-            return Err(UserAgentError::InvalidBootstrapToken);
-        }
-
-        {
-            let mut conn = self.db.get().await?;
-
-            diesel::insert_into(schema::useragent_client::table)
-                .values((
-                    schema::useragent_client::public_key.eq(pubkey.as_bytes().to_vec()),
-                    schema::useragent_client::nonce.eq(1),
-                ))
-                .execute(&mut conn)
-                .await?;
-        }
-
-        self.transition(UserAgentEvents::ReceivedBootstrapToken)?;
-
-        Ok(auth_response(ServerAuthPayload::AuthOk(AuthOk {})))
-    }
-
-    async fn auth_with_challenge(&mut self, pubkey: VerifyingKey, pubkey_bytes: Vec<u8>) -> Output {
-        let nonce: Option<i32> = {
-            let mut db_conn = self.db.get().await?;
-            db_conn
-                .exclusive_transaction(|conn| {
-                    Box::pin(async move {
-                        let current_nonce = schema::useragent_client::table
-                            .filter(
-                                schema::useragent_client::public_key.eq(pubkey.as_bytes().to_vec()),
-                            )
-                            .select(schema::useragent_client::nonce)
-                            .first::<i32>(conn)
-                            .await?;
-
-                        update(schema::useragent_client::table)
-                            .filter(
-                                schema::useragent_client::public_key.eq(pubkey.as_bytes().to_vec()),
-                            )
-                            .set(schema::useragent_client::nonce.eq(current_nonce + 1))
-                            .execute(conn)
-                            .await?;
-
-                        Result::<_, diesel::result::Error>::Ok(current_nonce)
-                    })
-                })
-                .await
-                .optional()?
-        };
-
-        let Some(nonce) = nonce else {
-            error!(?pubkey, "Public key not found in database");
-            return Err(UserAgentError::PubkeyNotRegistered);
-        };
-
-        let challenge = auth::AuthChallenge {
-            pubkey: pubkey_bytes,
-            nonce,
-        };
-
-        self.transition(UserAgentEvents::SentChallenge(ChallengeContext {
-            challenge: challenge.clone(),
-            key: pubkey,
-        }))?;
-
-        info!(
-            ?pubkey,
-            ?challenge,
-            "Sent authentication challenge to client"
-        );
-
-        Ok(auth_response(ServerAuthPayload::AuthChallenge(challenge)))
-    }
-
-    fn verify_challenge_solution(
-        &self,
-        solution: &auth::AuthChallengeSolution,
-    ) -> Result<(bool, &ChallengeContext), UserAgentError> {
-        let UserAgentStates::WaitingForChallengeSolution(challenge_context) = self.state.state()
-        else {
-            error!("Received challenge solution in invalid state");
-            return Err(UserAgentError::InvalidState);
-        };
-        let formatted_challenge = arbiter_proto::format_challenge(&challenge_context.challenge);
-
-        let signature = solution.signature.as_slice().try_into().map_err(|_| {
-            error!(?solution, "Invalid signature length");
-            UserAgentError::InvalidSignatureLength
-        })?;
-
-        let valid = challenge_context
-            .key
-            .verify_strict(&formatted_challenge, &signature)
-            .is_ok();
-
-        Ok((valid, challenge_context))
-    }
-}
-
-type Output = Result<UserAgentResponse, UserAgentError>;
-
-fn auth_response(payload: ServerAuthPayload) -> UserAgentResponse {
-    UserAgentResponse {
-        payload: Some(UserAgentResponsePayload::AuthMessage(AuthServerMessage {
-            payload: Some(payload),
-        })),
-    }
-}
-
-fn unseal_response(payload: UserAgentResponsePayload) -> UserAgentResponse {
-    UserAgentResponse {
-        payload: Some(payload),
-    }
-}
-
-#[messages]
-impl UserAgentActor {
-    #[message]
-    pub async fn handle_unseal_request(&mut self, req: UnsealStart) -> Output {
-        let secret = EphemeralSecret::random();
-        let public_key = PublicKey::from(&secret);
-
-        let client_pubkey_bytes: [u8; 32] = req
-            .client_pubkey
-            .try_into()
-            .map_err(|_| UserAgentError::InvalidPubkey)?;
-
-        let client_public_key = PublicKey::from(client_pubkey_bytes);
-
-        self.transition(UserAgentEvents::UnsealRequest(UnsealContext {
-            secret: Mutex::new(Some(secret)),
-            client_public_key,
-        }))?;
-
-        Ok(unseal_response(
-            UserAgentResponsePayload::UnsealStartResponse(UnsealStartResponse {
-                server_pubkey: public_key.as_bytes().to_vec(),
-            }),
-        ))
-    }
-
-    #[message]
-    pub async fn handle_unseal_encrypted_key(&mut self, req: UnsealEncryptedKey) -> Output {
-        let UserAgentStates::WaitingForUnsealKey(unseal_context) = self.state.state() else {
-            error!("Received unseal encrypted key in invalid state");
-            return Err(UserAgentError::InvalidState);
-        };
-        let ephemeral_secret = {
-            let mut secret_lock = unseal_context.secret.lock().unwrap();
-            let secret = secret_lock.take();
-            match secret {
-                Some(secret) => secret,
-                None => {
-                    drop(secret_lock);
-                    error!("Ephemeral secret already taken");
-                    self.transition(UserAgentEvents::ReceivedInvalidKey)?;
-                    return Ok(unseal_response(UserAgentResponsePayload::UnsealResult(
-                        UnsealResult::InvalidKey.into(),
-                    )));
-                }
-            }
-        };
-
-        let nonce = XNonce::from_slice(&req.nonce);
-
-        let shared_secret = ephemeral_secret.diffie_hellman(&unseal_context.client_public_key);
-        let cipher = XChaCha20Poly1305::new(shared_secret.as_bytes().into());
-
-        let mut seal_key_buffer = MemSafe::new(req.ciphertext.clone()).unwrap();
-
-        let decryption_result = {
-            let mut write_handle = seal_key_buffer.write().unwrap();
-            let write_handle = write_handle.deref_mut();
-            cipher.decrypt_in_place(nonce, &req.associated_data, write_handle)
-        };
-
-        match decryption_result {
-            Ok(_) => {
-                match self
-                    .actors
-                    .key_holder
-                    .ask(TryUnseal {
-                        seal_key_raw: seal_key_buffer,
-                    })
-                    .await
-                {
-                    Ok(_) => {
-                        info!("Successfully unsealed key with client-provided key");
-                        self.transition(UserAgentEvents::ReceivedValidKey)?;
-                        Ok(unseal_response(UserAgentResponsePayload::UnsealResult(
-                            UnsealResult::Success.into(),
-                        )))
-                    }
-                    Err(SendError::HandlerError(keyholder::Error::InvalidKey)) => {
-                        self.transition(UserAgentEvents::ReceivedInvalidKey)?;
-                        Ok(unseal_response(UserAgentResponsePayload::UnsealResult(
-                            UnsealResult::InvalidKey.into(),
-                        )))
-                    }
-                    Err(SendError::HandlerError(err)) => {
-                        error!(?err, "Keyholder failed to unseal key");
-                        self.transition(UserAgentEvents::ReceivedInvalidKey)?;
-                        Ok(unseal_response(UserAgentResponsePayload::UnsealResult(
-                            UnsealResult::InvalidKey.into(),
-                        )))
-                    }
-                    Err(err) => {
-                        error!(?err, "Failed to send unseal request to keyholder");
-                        self.transition(UserAgentEvents::ReceivedInvalidKey)?;
-                        Err(UserAgentError::ActorUnavailable)
-                    }
-                }
-            }
-            Err(err) => {
-                error!(?err, "Failed to decrypt unseal key");
-                self.transition(UserAgentEvents::ReceivedInvalidKey)?;
-                Ok(unseal_response(UserAgentResponsePayload::UnsealResult(
-                    UnsealResult::InvalidKey.into(),
-                )))
+impl AuthPublicKey {
+    /// Canonical bytes stored in DB and echoed back in the challenge.
+    /// Ed25519: raw 32 bytes. ECDSA: SEC1 compressed 33 bytes. RSA: DER-encoded SPKI.
+    pub fn to_stored_bytes(&self) -> Vec<u8> {
+        match self {
+            AuthPublicKey::Ed25519(k) => k.to_bytes().to_vec(),
+            // SEC1 compressed (33 bytes) is the natural compact format for secp256k1
+            AuthPublicKey::EcdsaSecp256k1(k) => k.to_encoded_point(true).as_bytes().to_vec(),
+            AuthPublicKey::Rsa(k) => {
+                use rsa::pkcs8::EncodePublicKey as _;
+                #[allow(clippy::expect_used)]
+                k.to_public_key_der()
+                    .expect("rsa SPKI encoding is infallible")
+                    .to_vec()
             }
         }
     }
 
-    #[message]
-    pub async fn handle_auth_challenge_request(&mut self, req: AuthChallengeRequest) -> Output {
-        let pubkey = req
-            .pubkey
-            .as_array()
-            .ok_or(UserAgentError::InvalidPubkey)?;
-        let pubkey = VerifyingKey::from_bytes(pubkey).map_err(|_err| {
-            error!(?pubkey, "Failed to convert to VerifyingKey");
-            UserAgentError::InvalidPubkey
-        })?;
-
-        self.transition(UserAgentEvents::AuthRequest)?;
-
-        match req.bootstrap_token {
-            Some(token) => self.auth_with_bootstrap_token(pubkey, token).await,
-            None => self.auth_with_challenge(pubkey, req.pubkey).await,
-        }
-    }
-
-    #[message]
-    pub async fn handle_auth_challenge_solution(
-        &mut self,
-        solution: auth::AuthChallengeSolution,
-    ) -> Output {
-        let (valid, challenge_context) = self.verify_challenge_solution(&solution)?;
-
-        if valid {
-            info!(
-                ?challenge_context,
-                "Client provided valid solution to authentication challenge"
-            );
-            self.transition(UserAgentEvents::ReceivedGoodSolution)?;
-            Ok(auth_response(ServerAuthPayload::AuthOk(AuthOk {})))
-        } else {
-            error!("Client provided invalid solution to authentication challenge");
-            self.transition(UserAgentEvents::ReceivedBadSolution)?;
-            Err(UserAgentError::InvalidChallengeSolution)
+    pub fn key_type(&self) -> KeyType {
+        match self {
+            AuthPublicKey::Ed25519(_) => KeyType::Ed25519,
+            AuthPublicKey::EcdsaSecp256k1(_) => KeyType::EcdsaSecp256k1,
+            AuthPublicKey::Rsa(_) => KeyType::Rsa,
         }
     }
 }
 
-impl Message<UserAgentRequest> for UserAgentActor {
-    type Reply = ();
+impl TryFrom<(KeyType, Vec<u8>)> for AuthPublicKey {
+    type Error = &'static str;
 
-    async fn handle(
-        &mut self,
-        msg: UserAgentRequest,
-        _ctx: &mut kameo::prelude::Context<Self, Self::Reply>,
-    ) -> Self::Reply {
-        let result = self.process_request(msg).await;
-        if let Err(e) = self.transport.tell(result).await {
-            error!(actor = "useragent", "Failed to send response to transport: {}", e);
+    fn try_from(value: (KeyType, Vec<u8>)) -> Result<Self, Self::Error> {
+        let (key_type, bytes) = value;
+        match key_type {
+            KeyType::Ed25519 => {
+                let bytes: [u8; 32] = bytes.try_into().map_err(|_| "invalid Ed25519 key length")?;
+                let key = ed25519_dalek::VerifyingKey::from_bytes(&bytes)
+                    .map_err(|_e| "invalid Ed25519 key")?;
+                Ok(AuthPublicKey::Ed25519(key))
+            }
+            KeyType::EcdsaSecp256k1 => {
+                let point =
+                    k256::EncodedPoint::from_bytes(&bytes).map_err(|_e| "invalid ECDSA key")?;
+                let key = k256::ecdsa::VerifyingKey::from_encoded_point(&point)
+                    .map_err(|_e| "invalid ECDSA key")?;
+                Ok(AuthPublicKey::EcdsaSecp256k1(key))
+            }
+            KeyType::Rsa => {
+                use rsa::pkcs8::DecodePublicKey as _;
+                let key = rsa::RsaPublicKey::from_public_key_der(&bytes)
+                    .map_err(|_e| "invalid RSA key")?;
+                Ok(AuthPublicKey::Rsa(key))
+            }
         }
     }
 }
+
+// Messages, sent by user agent to connection client without having a request
+#[derive(Debug)]
+pub enum OutOfBand {
+    ClientConnectionRequest { profile: ClientProfile },
+    ClientConnectionCancel { pubkey: ed25519_dalek::VerifyingKey },
+}
+
+pub struct UserAgentConnection {
+    pub(crate) db: db::DatabasePool,
+    pub(crate) actors: GlobalActors,
+}
+
+impl UserAgentConnection {
+    pub fn new(db: db::DatabasePool, actors: GlobalActors) -> Self {
+        Self { db, actors }
+    }
+}
+
+pub mod auth;
+pub mod session;
+
+pub use auth::authenticate;
+pub use session::UserAgentSession;

server/crates/arbiter-server/src/actors/user_agent/session.rs

@@ -0,0 +1,181 @@
+use std::{borrow::Cow, collections::HashMap};
+
+use arbiter_proto::transport::Sender;
+use async_trait::async_trait;
+use ed25519_dalek::VerifyingKey;
+use kameo::{Actor, actor::ActorRef, messages};
+use thiserror::Error;
+use tracing::error;
+
+use crate::actors::{
+    client::ClientProfile,
+    flow_coordinator::{RegisterUserAgent, client_connect_approval::ClientApprovalController},
+    user_agent::{OutOfBand, UserAgentConnection},
+};
+
+mod state;
+use state::{DummyContext, UserAgentEvents, UserAgentStateMachine};
+
+#[derive(Debug, Error)]
+pub enum Error {
+    #[error("State transition failed")]
+    State,
+
+    #[error("Internal error: {message}")]
+    Internal { message: Cow<'static, str> },
+}
+
+impl From<crate::db::PoolError> for Error {
+    fn from(err: crate::db::PoolError) -> Self {
+        error!(?err, "Database pool error");
+        Self::internal("Database pool error")
+    }
+}
+impl From<diesel::result::Error> for Error {
+    fn from(err: diesel::result::Error) -> Self {
+        error!(?err, "Database error");
+        Self::internal("Database error")
+    }
+}
+
+impl Error {
+    pub fn internal(message: impl Into<Cow<'static, str>>) -> Self {
+        Self::Internal {
+            message: message.into(),
+        }
+    }
+}
+
+pub struct PendingClientApproval {
+    controller: ActorRef<ClientApprovalController>,
+}
+
+pub struct UserAgentSession {
+    props: UserAgentConnection,
+    state: UserAgentStateMachine<DummyContext>,
+    sender: Box<dyn Sender<OutOfBand>>,
+
+    pending_client_approvals: HashMap<VerifyingKey, PendingClientApproval>,
+}
+
+pub mod connection;
+
+impl UserAgentSession {
+    pub(crate) fn new(props: UserAgentConnection, sender: Box<dyn Sender<OutOfBand>>) -> Self {
+        Self {
+            props,
+            state: UserAgentStateMachine::new(DummyContext),
+            sender,
+            pending_client_approvals: Default::default(),
+        }
+    }
+
+    pub fn new_test(db: crate::db::DatabasePool, actors: crate::actors::GlobalActors) -> Self {
+        struct DummySender;
+
+        #[async_trait]
+        impl Sender<OutOfBand> for DummySender {
+            async fn send(
+                &mut self,
+                _item: OutOfBand,
+            ) -> Result<(), arbiter_proto::transport::Error> {
+                Ok(())
+            }
+        }
+
+        Self::new(UserAgentConnection::new(db, actors), Box::new(DummySender))
+    }
+
+    fn transition(&mut self, event: UserAgentEvents) -> Result<(), Error> {
+        self.state.process_event(event).map_err(|e| {
+            error!(?e, "State transition failed");
+            Error::State
+        })?;
+        Ok(())
+    }
+}
+
+#[messages]
+impl UserAgentSession {
+    #[message]
+    pub async fn begin_new_client_approval(
+        &mut self,
+        client: ClientProfile,
+        controller: ActorRef<ClientApprovalController>,
+    ) {
+        if let Err(e) = self
+            .sender
+            .send(OutOfBand::ClientConnectionRequest {
+                profile: client.clone(),
+            })
+            .await
+        {
+            error!(
+                ?e,
+                actor = "user_agent",
+                event = "failed to announce new client connection"
+            );
+            return;
+        }
+
+        self.pending_client_approvals
+            .insert(client.pubkey, PendingClientApproval { controller });
+    }
+}
+
+impl Actor for UserAgentSession {
+    type Args = Self;
+
+    type Error = Error;
+
+    async fn on_start(
+        args: Self::Args,
+        this: kameo::prelude::ActorRef<Self>,
+    ) -> Result<Self, Self::Error> {
+        args.props
+            .actors
+            .flow_coordinator
+            .ask(RegisterUserAgent {
+                actor: this.clone(),
+            })
+            .await
+            .map_err(|err| {
+                error!(
+                    ?err,
+                    "Failed to register user agent connection with flow coordinator"
+                );
+                Error::internal("Failed to register user agent connection with flow coordinator")
+            })?;
+        Ok(args)
+    }
+
+    async fn on_link_died(
+        &mut self,
+        _: kameo::prelude::WeakActorRef<Self>,
+        id: kameo::prelude::ActorId,
+        _: kameo::prelude::ActorStopReason,
+    ) -> Result<std::ops::ControlFlow<kameo::prelude::ActorStopReason>, Self::Error> {
+        let cancelled_pubkey = self
+            .pending_client_approvals
+            .iter()
+            .find_map(|(k, v)| (v.controller.id() == id).then_some(*k));
+
+        if let Some(pubkey) = cancelled_pubkey {
+            self.pending_client_approvals.remove(&pubkey);
+
+            if let Err(e) = self
+                .sender
+                .send(OutOfBand::ClientConnectionCancel { pubkey })
+                .await
+            {
+                error!(
+                    ?e,
+                    actor = "user_agent",
+                    event = "failed to announce client connection cancellation"
+                );
+            }
+        }
+
+        Ok(std::ops::ControlFlow::Continue(()))
+    }
+}

server/crates/arbiter-server/src/actors/user_agent/session/connection.rs

@@ -0,0 +1,510 @@
+use std::sync::Mutex;
+
+use alloy::{consensus::TxEip1559, primitives::Address, signers::Signature};
+use chacha20poly1305::{AeadInPlace, XChaCha20Poly1305, XNonce, aead::KeyInit};
+use diesel::{ExpressionMethods as _, QueryDsl as _, SelectableHelper};
+use diesel_async::{AsyncConnection, RunQueryDsl};
+use kameo::error::SendError;
+use kameo::messages;
+use kameo::prelude::Context;
+use tracing::{error, info};
+use x25519_dalek::{EphemeralSecret, PublicKey};
+
+use crate::actors::flow_coordinator::client_connect_approval::ClientApprovalAnswer;
+use crate::actors::keyholder::KeyHolderState;
+use crate::actors::user_agent::session::Error;
+use crate::db::models::{
+    EvmWalletAccess, NewEvmWalletAccess, ProgramClient, ProgramClientMetadata,
+};
+use crate::evm::policies::{Grant, SpecificGrant};
+use crate::safe_cell::SafeCell;
+use crate::{
+    actors::{
+        evm::{
+            ClientSignTransaction, Generate, ListWallets, SignTransactionError as EvmSignError,
+            UseragentCreateGrant, UseragentDeleteGrant, UseragentListGrants,
+        },
+        keyholder::{self, Bootstrap, TryUnseal},
+        user_agent::session::{
+            UserAgentSession,
+            state::{UnsealContext, UserAgentEvents, UserAgentStates},
+        },
+    },
+    safe_cell::SafeCellHandle as _,
+};
+
+impl UserAgentSession {
+    fn take_unseal_secret(&mut self) -> Result<(EphemeralSecret, PublicKey), Error> {
+        let UserAgentStates::WaitingForUnsealKey(unseal_context) = self.state.state() else {
+            error!("Received encrypted key in invalid state");
+            return Err(Error::internal("Invalid state for unseal encrypted key"));
+        };
+
+        let ephemeral_secret = {
+            #[allow(
+                clippy::unwrap_used,
+                reason = "Mutex poison is unrecoverable and should panic"
+            )]
+            let mut secret_lock = unseal_context.secret.lock().unwrap();
+            let secret = secret_lock.take();
+            match secret {
+                Some(secret) => secret,
+                None => {
+                    drop(secret_lock);
+                    error!("Ephemeral secret already taken");
+                    return Err(Error::internal("Ephemeral secret already taken"));
+                }
+            }
+        };
+
+        Ok((ephemeral_secret, unseal_context.client_public_key))
+    }
+
+    fn decrypt_client_key_material(
+        ephemeral_secret: EphemeralSecret,
+        client_public_key: PublicKey,
+        nonce: &[u8],
+        ciphertext: &[u8],
+        associated_data: &[u8],
+    ) -> Result<SafeCell<Vec<u8>>, ()> {
+        let nonce = XNonce::from_slice(nonce);
+
+        let shared_secret = ephemeral_secret.diffie_hellman(&client_public_key);
+        let cipher = XChaCha20Poly1305::new(shared_secret.as_bytes().into());
+
+        let mut key_buffer = SafeCell::new(ciphertext.to_vec());
+
+        let decryption_result = key_buffer.write_inline(|write_handle| {
+            cipher.decrypt_in_place(nonce, associated_data, write_handle)
+        });
+
+        match decryption_result {
+            Ok(_) => Ok(key_buffer),
+            Err(err) => {
+                error!(?err, "Failed to decrypt encrypted key material");
+                Err(())
+            }
+        }
+    }
+}
+
+pub struct UnsealStartResponse {
+    pub server_pubkey: PublicKey,
+}
+
+#[derive(Debug, Error)]
+pub enum UnsealError {
+    #[error("Invalid key provided for unsealing")]
+    InvalidKey,
+    #[error("Internal error during unsealing process")]
+    General(#[from] super::Error),
+}
+
+#[derive(Debug, Error)]
+pub enum BootstrapError {
+    #[error("Invalid key provided for bootstrapping")]
+    InvalidKey,
+    #[error("Vault is already bootstrapped")]
+    AlreadyBootstrapped,
+
+    #[error("Internal error during bootstrapping process")]
+    General(#[from] super::Error),
+}
+
+#[derive(Debug, Error)]
+pub enum SignTransactionError {
+    #[error("Policy evaluation failed")]
+    Vet(#[from] crate::evm::VetError),
+
+    #[error("Internal signing error")]
+    Internal,
+}
+
+#[messages]
+impl UserAgentSession {
+    #[message]
+    pub async fn handle_unseal_request(
+        &mut self,
+        client_pubkey: x25519_dalek::PublicKey,
+    ) -> Result<UnsealStartResponse, Error> {
+        let secret = EphemeralSecret::random();
+        let public_key = PublicKey::from(&secret);
+
+        self.transition(UserAgentEvents::UnsealRequest(UnsealContext {
+            secret: Mutex::new(Some(secret)),
+            client_public_key: client_pubkey,
+        }))?;
+
+        Ok(UnsealStartResponse {
+            server_pubkey: public_key,
+        })
+    }
+
+    #[message]
+    pub async fn handle_unseal_encrypted_key(
+        &mut self,
+        nonce: Vec<u8>,
+        ciphertext: Vec<u8>,
+        associated_data: Vec<u8>,
+    ) -> Result<(), UnsealError> {
+        let (ephemeral_secret, client_public_key) = match self.take_unseal_secret() {
+            Ok(values) => values,
+            Err(Error::State) => {
+                self.transition(UserAgentEvents::ReceivedInvalidKey)?;
+                return Err(UnsealError::InvalidKey);
+            }
+            Err(_err) => {
+                return Err(Error::internal("Failed to take unseal secret").into());
+            }
+        };
+
+        let seal_key_buffer = match Self::decrypt_client_key_material(
+            ephemeral_secret,
+            client_public_key,
+            &nonce,
+            &ciphertext,
+            &associated_data,
+        ) {
+            Ok(buffer) => buffer,
+            Err(()) => {
+                self.transition(UserAgentEvents::ReceivedInvalidKey)?;
+                return Err(UnsealError::InvalidKey);
+            }
+        };
+
+        match self
+            .props
+            .actors
+            .key_holder
+            .ask(TryUnseal {
+                seal_key_raw: seal_key_buffer,
+            })
+            .await
+        {
+            Ok(_) => {
+                info!("Successfully unsealed key with client-provided key");
+                self.transition(UserAgentEvents::ReceivedValidKey)?;
+                Ok(())
+            }
+            Err(SendError::HandlerError(keyholder::Error::InvalidKey)) => {
+                self.transition(UserAgentEvents::ReceivedInvalidKey)?;
+                Err(UnsealError::InvalidKey)
+            }
+            Err(SendError::HandlerError(err)) => {
+                error!(?err, "Keyholder failed to unseal key");
+                self.transition(UserAgentEvents::ReceivedInvalidKey)?;
+                Err(UnsealError::InvalidKey)
+            }
+            Err(err) => {
+                error!(?err, "Failed to send unseal request to keyholder");
+                self.transition(UserAgentEvents::ReceivedInvalidKey)?;
+                Err(Error::internal("Vault actor error").into())
+            }
+        }
+    }
+
+    #[message]
+    pub(crate) async fn handle_bootstrap_encrypted_key(
+        &mut self,
+        nonce: Vec<u8>,
+        ciphertext: Vec<u8>,
+        associated_data: Vec<u8>,
+    ) -> Result<(), BootstrapError> {
+        let (ephemeral_secret, client_public_key) = match self.take_unseal_secret() {
+            Ok(values) => values,
+            Err(Error::State) => {
+                self.transition(UserAgentEvents::ReceivedInvalidKey)?;
+                return Err(BootstrapError::InvalidKey);
+            }
+            Err(err) => return Err(err.into()),
+        };
+
+        let seal_key_buffer = match Self::decrypt_client_key_material(
+            ephemeral_secret,
+            client_public_key,
+            &nonce,
+            &ciphertext,
+            &associated_data,
+        ) {
+            Ok(buffer) => buffer,
+            Err(()) => {
+                self.transition(UserAgentEvents::ReceivedInvalidKey)?;
+                return Err(BootstrapError::InvalidKey);
+            }
+        };
+
+        match self
+            .props
+            .actors
+            .key_holder
+            .ask(Bootstrap {
+                seal_key_raw: seal_key_buffer,
+            })
+            .await
+        {
+            Ok(_) => {
+                info!("Successfully bootstrapped vault with client-provided key");
+                self.transition(UserAgentEvents::ReceivedValidKey)?;
+                Ok(())
+            }
+            Err(SendError::HandlerError(keyholder::Error::AlreadyBootstrapped)) => {
+                self.transition(UserAgentEvents::ReceivedInvalidKey)?;
+                Err(BootstrapError::AlreadyBootstrapped)
+            }
+            Err(SendError::HandlerError(err)) => {
+                error!(?err, "Keyholder failed to bootstrap vault");
+                self.transition(UserAgentEvents::ReceivedInvalidKey)?;
+                Err(BootstrapError::InvalidKey)
+            }
+            Err(err) => {
+                error!(?err, "Failed to send bootstrap request to keyholder");
+                self.transition(UserAgentEvents::ReceivedInvalidKey)?;
+                Err(BootstrapError::General(Error::internal(
+                    "Vault actor error",
+                )))
+            }
+        }
+    }
+}
+
+#[messages]
+impl UserAgentSession {
+    #[message]
+    pub(crate) async fn handle_query_vault_state(&mut self) -> Result<KeyHolderState, Error> {
+        use crate::actors::keyholder::GetState;
+
+        let vault_state = match self.props.actors.key_holder.ask(GetState {}).await {
+            Ok(state) => state,
+            Err(err) => {
+                error!(?err, actor = "useragent", "keyholder.query.failed");
+                return Err(Error::internal("Vault is in broken state"));
+            }
+        };
+
+        Ok(vault_state)
+    }
+}
+
+#[messages]
+impl UserAgentSession {
+    #[message]
+    pub(crate) async fn handle_evm_wallet_create(&mut self) -> Result<(i32, Address), Error> {
+        match self.props.actors.evm.ask(Generate {}).await {
+            Ok(address) => Ok(address),
+            Err(SendError::HandlerError(err)) => Err(Error::internal(format!(
+                "EVM wallet generation failed: {err}"
+            ))),
+            Err(err) => {
+                error!(?err, "EVM actor unreachable during wallet create");
+                Err(Error::internal("EVM actor unreachable"))
+            }
+        }
+    }
+
+    #[message]
+    pub(crate) async fn handle_evm_wallet_list(&mut self) -> Result<Vec<(i32, Address)>, Error> {
+        match self.props.actors.evm.ask(ListWallets {}).await {
+            Ok(wallets) => Ok(wallets),
+            Err(err) => {
+                error!(?err, "EVM wallet list failed");
+                Err(Error::internal("Failed to list EVM wallets"))
+            }
+        }
+    }
+}
+
+#[messages]
+impl UserAgentSession {
+    #[message]
+    pub(crate) async fn handle_grant_list(&mut self) -> Result<Vec<Grant<SpecificGrant>>, Error> {
+        match self.props.actors.evm.ask(UseragentListGrants {}).await {
+            Ok(grants) => Ok(grants),
+            Err(err) => {
+                error!(?err, "EVM grant list failed");
+                Err(Error::internal("Failed to list EVM grants"))
+            }
+        }
+    }
+
+    #[message]
+    pub(crate) async fn handle_grant_create(
+        &mut self,
+        basic: crate::evm::policies::SharedGrantSettings,
+        grant: crate::evm::policies::SpecificGrant,
+    ) -> Result<i32, Error> {
+        match self
+            .props
+            .actors
+            .evm
+            .ask(UseragentCreateGrant { basic, grant })
+            .await
+        {
+            Ok(grant_id) => Ok(grant_id),
+            Err(err) => {
+                error!(?err, "EVM grant create failed");
+                Err(Error::internal("Failed to create EVM grant"))
+            }
+        }
+    }
+
+    #[message]
+    pub(crate) async fn handle_grant_delete(&mut self, grant_id: i32) -> Result<(), Error> {
+        match self
+            .props
+            .actors
+            .evm
+            .ask(UseragentDeleteGrant { grant_id })
+            .await
+        {
+            Ok(()) => Ok(()),
+            Err(err) => {
+                error!(?err, "EVM grant delete failed");
+                Err(Error::internal("Failed to delete EVM grant"))
+            }
+        }
+    }
+
+    #[message]
+    pub(crate) async fn handle_sign_transaction(
+        &mut self,
+        client_id: i32,
+        wallet_address: Address,
+        transaction: TxEip1559,
+    ) -> Result<Signature, SignTransactionError> {
+        match self
+            .props
+            .actors
+            .evm
+            .ask(ClientSignTransaction {
+                client_id,
+                wallet_address,
+                transaction,
+            })
+            .await
+        {
+            Ok(signature) => Ok(signature),
+            Err(SendError::HandlerError(EvmSignError::Vet(vet_error))) => {
+                Err(SignTransactionError::Vet(vet_error))
+            }
+            Err(err) => {
+                error!(?err, "EVM sign transaction failed in user-agent session");
+                Err(SignTransactionError::Internal)
+            }
+        }
+    }
+
+    #[message]
+    pub(crate) async fn handle_grant_evm_wallet_access(
+        &mut self,
+        entries: Vec<NewEvmWalletAccess>,
+    ) -> Result<(), Error> {
+        let mut conn = self.props.db.get().await?;
+        conn.transaction(|conn| {
+            Box::pin(async move {
+                use crate::db::schema::evm_wallet_access;
+
+                for entry in entries {
+                    diesel::insert_into(evm_wallet_access::table)
+                        .values(&entry)
+                        .on_conflict_do_nothing()
+                        .execute(conn)
+                        .await?;
+                }
+
+                Result::<_, Error>::Ok(())
+            })
+        })
+        .await?;
+        Ok(())
+    }
+
+    #[message]
+    pub(crate) async fn handle_revoke_evm_wallet_access(
+        &mut self,
+        entries: Vec<i32>,
+    ) -> Result<(), Error> {
+        let mut conn = self.props.db.get().await?;
+        conn.transaction(|conn| {
+            Box::pin(async move {
+                use crate::db::schema::evm_wallet_access;
+                for entry in entries {
+                    diesel::delete(evm_wallet_access::table)
+                        .filter(evm_wallet_access::wallet_id.eq(entry))
+                        .execute(conn)
+                        .await?;
+                }
+
+                Result::<_, Error>::Ok(())
+            })
+        })
+        .await?;
+        Ok(())
+    }
+
+    #[message]
+    pub(crate) async fn handle_list_wallet_access(
+        &mut self,
+    ) -> Result<Vec<EvmWalletAccess>, Error> {
+        let mut conn = self.props.db.get().await?;
+        use crate::db::schema::evm_wallet_access;
+        let access_entries = evm_wallet_access::table
+            .select(EvmWalletAccess::as_select())
+            .load::<_>(&mut conn)
+            .await?;
+        Ok(access_entries)
+    }
+}
+
+#[messages]
+impl UserAgentSession {
+    #[message(ctx)]
+    pub(crate) async fn handle_new_client_approve(
+        &mut self,
+        approved: bool,
+        pubkey: ed25519_dalek::VerifyingKey,
+        ctx: &mut Context<Self, Result<(), Error>>,
+    ) -> Result<(), Error> {
+        let pending_approval = match self.pending_client_approvals.remove(&pubkey) {
+            Some(approval) => approval,
+            None => {
+                error!("Received client connection response for unknown client");
+                return Err(Error::internal("Unknown client in connection response"));
+            }
+        };
+
+        pending_approval
+            .controller
+            .tell(ClientApprovalAnswer { approved })
+            .await
+            .map_err(|err| {
+                error!(
+                    ?err,
+                    "Failed to send client approval response to controller"
+                );
+                Error::internal("Failed to send client approval response to controller")
+            })?;
+
+        ctx.actor_ref().unlink(&pending_approval.controller).await;
+
+        Ok(())
+    }
+
+    #[message]
+    pub(crate) async fn handle_sdk_client_list(
+        &mut self,
+    ) -> Result<Vec<(ProgramClient, ProgramClientMetadata)>, Error> {
+        use crate::db::schema::{client_metadata, program_client};
+        let mut conn = self.props.db.get().await?;
+
+        let clients = program_client::table
+            .inner_join(client_metadata::table)
+            .select((
+                ProgramClient::as_select(),
+                ProgramClientMetadata::as_select(),
+            ))
+            .load::<(ProgramClient, ProgramClientMetadata)>(&mut conn)
+            .await?;
+
+        Ok(clients)
+    }
+}

server/crates/arbiter-server/src/actors/user_agent/session/state.rs

@@ -0,0 +1,27 @@
+use std::sync::Mutex;
+
+use x25519_dalek::{EphemeralSecret, PublicKey};
+
+pub struct UnsealContext {
+    pub client_public_key: PublicKey,
+    pub secret: Mutex<Option<EphemeralSecret>>,
+}
+
+smlang::statemachine!(
+    name: UserAgent,
+    custom_error: false,
+    transitions: {
+        *Idle + UnsealRequest(UnsealContext) / generate_temp_keypair = WaitingForUnsealKey(UnsealContext),
+        WaitingForUnsealKey(UnsealContext) + ReceivedValidKey = Unsealed,
+        WaitingForUnsealKey(UnsealContext) + ReceivedInvalidKey = Idle,
+    }
+);
+
+pub struct DummyContext;
+impl UserAgentStateMachineContext for DummyContext {
+    #[allow(missing_docs)]
+    #[allow(clippy::unused_unit)]
+    fn generate_temp_keypair(&mut self, event_data: UnsealContext) -> Result<UnsealContext, ()> {
+        Ok(event_data)
+    }
+}

server/crates/arbiter-server/src/actors/user_agent/state.rs

@@ -1,51 +0,0 @@
-use std::sync::Mutex;
-
-use arbiter_proto::proto::auth::AuthChallenge;
-use ed25519_dalek::VerifyingKey;
-use x25519_dalek::{EphemeralSecret, PublicKey};
-
-/// Context for state machine with validated key and sent challenge
-/// Challenge is then transformed to bytes using shared function and verified
-#[derive(Clone, Debug)]
-pub struct ChallengeContext {
-    pub challenge: AuthChallenge,
-    pub key: VerifyingKey,
-}
-
-pub struct UnsealContext {
-    pub client_public_key: PublicKey,
-    pub secret: Mutex<Option<EphemeralSecret>>,
-}
-
-smlang::statemachine!(
-    name: UserAgent,
-    custom_error: false,
-    transitions: {
-        *Init + AuthRequest =  ReceivedAuthRequest,
-        ReceivedAuthRequest + ReceivedBootstrapToken = Idle,
-
-        ReceivedAuthRequest + SentChallenge(ChallengeContext) / move_challenge = WaitingForChallengeSolution(ChallengeContext),
-
-        WaitingForChallengeSolution(ChallengeContext) + ReceivedGoodSolution = Idle,
-        WaitingForChallengeSolution(ChallengeContext) + ReceivedBadSolution = AuthError, // block further transitions, but connection should close anyway
-
-        Idle + UnsealRequest(UnsealContext) / generate_temp_keypair = WaitingForUnsealKey(UnsealContext),
-        WaitingForUnsealKey(UnsealContext) + ReceivedValidKey = Unsealed,
-        WaitingForUnsealKey(UnsealContext) + ReceivedInvalidKey = Idle,
-    }
-);
-
-pub struct DummyContext;
-impl UserAgentStateMachineContext for DummyContext {
-    #[allow(missing_docs)]
-    #[allow(clippy::unused_unit)]
-    fn generate_temp_keypair(&mut self, event_data: UnsealContext) -> Result<UnsealContext, ()> {
-        Ok(event_data)
-    }
-
-    #[allow(missing_docs)]
-    #[allow(clippy::unused_unit)]
-    fn move_challenge(&mut self, event_data: ChallengeContext) -> Result<ChallengeContext, ()> {
-        Ok(event_data)
-    }
-}

server/crates/arbiter-server/src/context/mod.rs

@@ -1,6 +1,5 @@
 use std::sync::Arc;
 
-use miette::Diagnostic;
 use thiserror::Error;
 
 use crate::{
@@ -11,30 +10,24 @@ use crate::{
 
 pub mod tls;
 
-#[derive(Error, Debug, Diagnostic)]
+#[derive(Error, Debug)]
 pub enum InitError {
     #[error("Database setup failed: {0}")]
-    #[diagnostic(code(arbiter_server::init::database_setup))]
     DatabaseSetup(#[from] db::DatabaseSetupError),
 
     #[error("Connection acquire failed: {0}")]
-    #[diagnostic(code(arbiter_server::init::database_pool))]
     DatabasePool(#[from] db::PoolError),
 
     #[error("Database query error: {0}")]
-    #[diagnostic(code(arbiter_server::init::database_query))]
     DatabaseQuery(#[from] diesel::result::Error),
 
     #[error("TLS initialization failed: {0}")]
-    #[diagnostic(code(arbiter_server::init::tls_init))]
     Tls(#[from] tls::InitError),
 
     #[error("Actor spawn failed: {0}")]
-    #[diagnostic(code(arbiter_server::init::actor_spawn))]
     ActorSpawn(#[from] crate::actors::SpawnError),
 
     #[error("I/O Error: {0}")]
-    #[diagnostic(code(arbiter_server::init::io))]
     Io(#[from] std::io::Error),
 }
 

server/crates/arbiter-server/src/context/tls.rs

@@ -1,14 +1,14 @@
-use std::string::FromUtf8Error;
+use std::{net::{IpAddr, Ipv4Addr}, string::FromUtf8Error};
 
 use diesel::{ExpressionMethods as _, QueryDsl, SelectableHelper as _};
 use diesel_async::{AsyncConnection, RunQueryDsl};
-use miette::Diagnostic;
+
 use pem::Pem;
 use rcgen::{
     BasicConstraints, Certificate, CertificateParams, CertifiedIssuer, DistinguishedName, DnType,
-    IsCa, Issuer, KeyPair, KeyUsagePurpose,
+    IsCa, Issuer, KeyPair, KeyUsagePurpose, SanType,
 };
-use rustls::pki_types::{pem::PemObject};
+use rustls::pki_types::pem::PemObject;
 use thiserror::Error;
 use tonic::transport::CertificateDer;
 
@@ -29,40 +29,31 @@ const ENCODE_CONFIG: pem::EncodeConfig = {
     pem::EncodeConfig::new().set_line_ending(line_ending)
 };
 
-#[derive(Error, Debug, Diagnostic)]
+#[derive(Error, Debug)]
 pub enum InitError {
     #[error("Key generation error during TLS initialization: {0}")]
-    #[diagnostic(code(arbiter_server::tls_init::key_generation))]
     KeyGeneration(#[from] rcgen::Error),
 
     #[error("Key invalid format: {0}")]
-    #[diagnostic(code(arbiter_server::tls_init::key_invalid_format))]
     KeyInvalidFormat(#[from] FromUtf8Error),
 
     #[error("Key deserialization error: {0}")]
-    #[diagnostic(code(arbiter_server::tls_init::key_deserialization))]
     KeyDeserializationError(rcgen::Error),
 
     #[error("Database error during TLS initialization: {0}")]
-    #[diagnostic(code(arbiter_server::tls_init::database_error))]
     DatabaseError(#[from] diesel::result::Error),
 
     #[error("Pem deserialization error during TLS initialization: {0}")]
-    #[diagnostic(code(arbiter_server::tls_init::pem_deserialization))]
     PemDeserializationError(#[from] rustls::pki_types::pem::Error),
 
     #[error("Database pool acquire error during TLS initialization: {0}")]
-    #[diagnostic(code(arbiter_server::tls_init::database_pool_acquire))]
     DatabasePoolAcquire(#[from] db::PoolError),
 }
 
 pub type PemCert = String;
 
 pub fn encode_cert_to_pem(cert: &CertificateDer) -> PemCert {
-    pem::encode_config(
-        &Pem::new("CERTIFICATE", cert.to_vec()),
-        ENCODE_CONFIG,
-    )
+    pem::encode_config(&Pem::new("CERTIFICATE", cert.to_vec()), ENCODE_CONFIG)
 }
 
 #[allow(unused)]
@@ -94,6 +85,10 @@ impl TlsCa {
 
         let cert_key_pem = certified_issuer.key().serialize_pem();
 
+        #[allow(
+            clippy::unwrap_used,
+            reason = "Broken cert couldn't bootstrap server anyway"
+        )]
         let issuer = Issuer::from_ca_cert_pem(
             &certified_issuer.pem(),
             KeyPair::from_pem(cert_key_pem.as_ref()).unwrap(),
@@ -113,6 +108,9 @@ impl TlsCa {
             KeyUsagePurpose::DigitalSignature,
             KeyUsagePurpose::KeyEncipherment,
         ];
+        params
+            .subject_alt_names
+            .push(SanType::IpAddress(Ipv4Addr::LOCALHOST.into()));
 
         let mut dn = DistinguishedName::new();
         dn.push(DnType::CommonName, "Arbiter Instance Leaf");

server/crates/arbiter-server/src/db/mod.rs

@@ -5,7 +5,7 @@ use diesel_async::{
     sync_connection_wrapper::SyncConnectionWrapper,
 };
 use diesel_migrations::{EmbeddedMigrations, MigrationHarness, embed_migrations};
-use miette::Diagnostic;
+
 use thiserror::Error;
 use tracing::info;
 
@@ -21,29 +21,32 @@ static DB_FILE: &str = "arbiter.sqlite";
 
 const MIGRATIONS: EmbeddedMigrations = embed_migrations!("migrations");
 
-#[derive(Error, Diagnostic, Debug)]
+#[derive(Error, Debug)]
 pub enum DatabaseSetupError {
     #[error("Failed to determine home directory")]
-    #[diagnostic(code(arbiter::db::home_dir))]
     HomeDir(std::io::Error),
 
     #[error(transparent)]
-    #[diagnostic(code(arbiter::db::connection))]
     Connection(diesel::ConnectionError),
 
     #[error(transparent)]
-    #[diagnostic(code(arbiter::db::concurrency))]
     ConcurrencySetup(diesel::result::Error),
 
     #[error(transparent)]
-    #[diagnostic(code(arbiter::db::migration))]
     Migration(Box<dyn std::error::Error + Send + Sync>),
 
     #[error(transparent)]
-    #[diagnostic(code(arbiter::db::pool))]
     Pool(#[from] PoolInitError),
 }
 
+#[derive(Error, Debug)]
+pub enum DatabaseError {
+    #[error("Database connection error")]
+    Pool(#[from] PoolError),
+    #[error("Database query error")]
+    Connection(#[from] diesel::result::Error),
+}
+
 #[tracing::instrument(level = "info")]
 fn database_path() -> Result<std::path::PathBuf, DatabaseSetupError> {
     let arbiter_home = arbiter_proto::home_path().map_err(DatabaseSetupError::HomeDir)?;
@@ -92,6 +95,7 @@ fn initialize_database(url: &str) -> Result<(), DatabaseSetupError> {
 #[tracing::instrument(level = "info")]
 pub async fn create_pool(url: Option<&str>) -> Result<DatabasePool, DatabaseSetupError> {
     let database_url = url.map(String::from).unwrap_or(
+        #[allow(clippy::expect_used)]
         database_path()?
             .to_str()
             .expect("database path is not valid UTF-8")
@@ -135,11 +139,13 @@ pub async fn create_test_pool() -> DatabasePool {
     let tempfile_name = Alphanumeric.sample_string(&mut rand::rng(), 16);
 
     let file = std::env::temp_dir().join(tempfile_name);
-    let url = format!(
-        "{}?mode=rwc",
-        file.to_str().expect("temp file path is not valid UTF-8")
-    );
+    #[allow(clippy::expect_used)]
+    let url = file
+        .to_str()
+        .expect("temp file path is not valid UTF-8")
+        .to_string();
 
+    #[allow(clippy::expect_used)]
     create_pool(Some(&url))
         .await
         .expect("Failed to create test database pool")

server/crates/arbiter-server/src/db/models.rs

@@ -1,14 +1,113 @@
 #![allow(unused)]
 #![allow(clippy::all)]
 
-use crate::db::schema::{self, aead_encrypted, arbiter_settings, root_key_history, tls_history};
+use crate::db::schema::{
+    self, aead_encrypted, arbiter_settings, evm_basic_grant, evm_ether_transfer_grant,
+    evm_ether_transfer_grant_target, evm_ether_transfer_limit, evm_token_transfer_grant,
+    evm_token_transfer_log, evm_token_transfer_volume_limit, evm_transaction_log, evm_wallet,
+    root_key_history, tls_history,
+};
+use chrono::{DateTime, Utc};
 use diesel::{prelude::*, sqlite::Sqlite};
 use restructed::Models;
 
 pub mod types {
     use chrono::{DateTime, Utc};
-    pub struct SqliteTimestamp(DateTime<Utc>);
+    use diesel::{
+        deserialize::{FromSql, FromSqlRow},
+        expression::AsExpression,
+        serialize::{IsNull, ToSql},
+        sql_types::Integer,
+        sqlite::{Sqlite, SqliteType},
+    };
+
+    #[derive(Debug, FromSqlRow, AsExpression, Clone)]
+    #[diesel(sql_type = Integer)]
+    #[repr(transparent)] // hint compiler to optimize the wrapper struct away
+    pub struct SqliteTimestamp(pub DateTime<Utc>);
+    impl SqliteTimestamp {
+        pub fn now() -> Self {
+            SqliteTimestamp(Utc::now())
+        }
+    }
+
+    impl From<chrono::DateTime<Utc>> for SqliteTimestamp {
+        fn from(dt: chrono::DateTime<Utc>) -> Self {
+            SqliteTimestamp(dt)
+        }
+    }
+    impl From<SqliteTimestamp> for chrono::DateTime<Utc> {
+        fn from(ts: SqliteTimestamp) -> Self {
+            ts.0
+        }
+    }
+
+    impl ToSql<Integer, Sqlite> for SqliteTimestamp {
+        fn to_sql<'b>(
+            &'b self,
+            out: &mut diesel::serialize::Output<'b, '_, Sqlite>,
+        ) -> diesel::serialize::Result {
+            let unix_timestamp = self.0.timestamp() as i32;
+            out.set_value(unix_timestamp);
+            Ok(IsNull::No)
+        }
+    }
+
+    impl FromSql<Integer, Sqlite> for SqliteTimestamp {
+        fn from_sql(
+            mut bytes: <Sqlite as diesel::backend::Backend>::RawValue<'_>,
+        ) -> diesel::deserialize::Result<Self> {
+            let Some(SqliteType::Long) = bytes.value_type() else {
+                return Err(format!(
+                    "Expected Integer type for SqliteTimestamp, got {:?}",
+                    bytes.value_type()
+                )
+                .into());
+            };
+
+            let unix_timestamp = bytes.read_long();
+            let datetime =
+                DateTime::from_timestamp(unix_timestamp, 0).ok_or("Timestamp is out of bounds")?;
+
+            Ok(SqliteTimestamp(datetime))
+        }
+    }
+
+    /// Key algorithm stored in the `useragent_client.key_type` column.
+    /// Values must stay stable — they are persisted in the database.
+    #[derive(Debug, Clone, Copy, PartialEq, Eq, FromSqlRow, AsExpression, strum::FromRepr)]
+    #[diesel(sql_type = Integer)]
+    #[repr(i32)]
+    pub enum KeyType {
+        Ed25519 = 1,
+        EcdsaSecp256k1 = 2,
+        Rsa = 3,
+    }
+
+    impl ToSql<Integer, Sqlite> for KeyType {
+        fn to_sql<'b>(
+            &'b self,
+            out: &mut diesel::serialize::Output<'b, '_, Sqlite>,
+        ) -> diesel::serialize::Result {
+            out.set_value(*self as i32);
+            Ok(IsNull::No)
+        }
+    }
+
+    impl FromSql<Integer, Sqlite> for KeyType {
+        fn from_sql(
+            mut bytes: <Sqlite as diesel::backend::Backend>::RawValue<'_>,
+        ) -> diesel::deserialize::Result<Self> {
+            let Some(SqliteType::Long) = bytes.value_type() else {
+                return Err("Expected Integer for KeyType".into());
+            };
+            let discriminant = bytes.read_long();
+            KeyType::from_repr(discriminant as i32)
+                .ok_or_else(|| format!("Unknown KeyType discriminant: {discriminant}").into())
+        }
+    }
 }
+pub use types::*;
 
 #[derive(Models, Queryable, Debug, Insertable, Selectable)]
 #[view(
@@ -25,7 +124,7 @@ pub struct AeadEncrypted {
     pub current_nonce: Vec<u8>,
     pub schema_version: i32,
     pub associated_root_key_id: i32, // references root_key_history.id
-    pub created_at: i32,
+    pub created_at: SqliteTimestamp,
 }
 
 #[derive(Models, Queryable, Debug, Insertable, Selectable)]
@@ -58,9 +157,9 @@ pub struct TlsHistory {
     pub id: i32,
     pub cert: String,
     pub cert_key: String, // PEM Encoded private key
-    pub ca_cert: String, // PEM Encoded certificate for cert signing
-    pub ca_key: String, // PEM Encoded public key for cert signing
-    pub created_at: i32,
+    pub ca_cert: String,  // PEM Encoded certificate for cert signing
+    pub ca_key: String,   // PEM Encoded public key for cert signing
+    pub created_at: SqliteTimestamp,
 }
 
 #[derive(Queryable, Debug, Insertable, Selectable)]
@@ -68,25 +167,212 @@ pub struct TlsHistory {
 pub struct ArbiterSettings {
     pub id: i32,
     pub root_key_id: Option<i32>, // references root_key_history.id
-    pub tls_id: Option<i32>, // references tls_history.id
+    pub tls_id: Option<i32>,      // references tls_history.id
 }
 
-#[derive(Queryable, Debug)]
+#[derive(Models, Queryable, Debug, Insertable, Selectable)]
+#[diesel(table_name = evm_wallet, check_for_backend(Sqlite))]
+#[view(
+    NewEvmWallet,
+    derive(Insertable),
+    omit(id, created_at),
+    attributes_with = "deriveless"
+)]
+pub struct EvmWallet {
+    pub id: i32,
+    pub address: Vec<u8>,
+    pub aead_encrypted_id: i32,
+    pub created_at: SqliteTimestamp,
+}
+
+#[derive(Models, Queryable, Debug, Insertable, Selectable, Clone)]
+#[diesel(table_name = schema::evm_wallet_access, check_for_backend(Sqlite))]
+#[view(
+    NewEvmWalletAccess,
+    derive(Insertable),
+    omit(id, created_at),
+    attributes_with = "deriveless"
+)]
+#[view(
+    CoreEvmWalletAccess,
+    derive(Insertable),
+    omit(created_at),
+    attributes_with = "deriveless"
+)]
+pub struct EvmWalletAccess {
+    pub id: i32,
+    pub wallet_id: i32,
+    pub client_id: i32,
+    pub created_at: SqliteTimestamp,
+}
+
+#[derive(Models, Queryable, Debug, Insertable, Selectable)]
+#[diesel(table_name = schema::client_metadata, check_for_backend(Sqlite))]
+pub struct ProgramClientMetadata {
+    pub id: i32,
+    pub name: String,
+    pub description: Option<String>,
+    pub version: Option<String>,
+    pub created_at: SqliteTimestamp,
+}
+
+#[derive(Models, Queryable, Debug, Insertable, Selectable)]
+#[diesel(table_name = schema::client_metadata_history, check_for_backend(Sqlite))]
+pub struct ProgramClientMetadataHistory {
+    pub id: i32,
+    pub metadata_id: i32,
+    pub client_id: i32,
+    pub created_at: SqliteTimestamp,
+}
+
+#[derive(Models, Queryable, Debug, Insertable, Selectable)]
 #[diesel(table_name = schema::program_client, check_for_backend(Sqlite))]
 pub struct ProgramClient {
     pub id: i32,
-    pub public_key: Vec<u8>,
     pub nonce: i32,
-    pub created_at: i32,
-    pub updated_at: i32,
+    pub public_key: Vec<u8>,
+    pub metadata_id: i32,
+    pub created_at: SqliteTimestamp,
+    pub updated_at: SqliteTimestamp,
 }
 
 #[derive(Queryable, Debug)]
 #[diesel(table_name = schema::useragent_client, check_for_backend(Sqlite))]
 pub struct UseragentClient {
     pub id: i32,
-    pub public_key: Vec<u8>,
     pub nonce: i32,
-    pub created_at: i32,
-    pub updated_at: i32,
+    pub public_key: Vec<u8>,
+    pub created_at: SqliteTimestamp,
+    pub updated_at: SqliteTimestamp,
+    pub key_type: KeyType,
+}
+
+#[derive(Models, Queryable, Debug, Insertable, Selectable)]
+#[diesel(table_name = evm_ether_transfer_limit, check_for_backend(Sqlite))]
+#[view(
+    NewEvmEtherTransferLimit,
+    derive(Insertable),
+    omit(id, created_at),
+    attributes_with = "deriveless"
+)]
+pub struct EvmEtherTransferLimit {
+    pub id: i32,
+    pub window_secs: i32,
+    pub max_volume: Vec<u8>,
+}
+
+#[derive(Models, Queryable, Debug, Insertable, Selectable)]
+#[diesel(table_name = evm_basic_grant, check_for_backend(Sqlite))]
+#[view(
+    NewEvmBasicGrant,
+    derive(Insertable),
+    omit(id, created_at),
+    attributes_with = "deriveless"
+)]
+pub struct EvmBasicGrant {
+    pub id: i32,
+    pub wallet_access_id: i32, // references evm_wallet_access.id
+    pub chain_id: i32,
+    pub valid_from: Option<SqliteTimestamp>,
+    pub valid_until: Option<SqliteTimestamp>,
+    pub max_gas_fee_per_gas: Option<Vec<u8>>,
+    pub max_priority_fee_per_gas: Option<Vec<u8>>,
+    pub rate_limit_count: Option<i32>,
+    pub rate_limit_window_secs: Option<i32>,
+    pub revoked_at: Option<SqliteTimestamp>,
+    pub created_at: SqliteTimestamp,
+}
+
+#[derive(Models, Queryable, Debug, Insertable, Selectable)]
+#[diesel(table_name = evm_transaction_log, check_for_backend(Sqlite))]
+#[view(
+    NewEvmTransactionLog,
+    derive(Insertable),
+    omit(id),
+    attributes_with = "deriveless"
+)]
+pub struct EvmTransactionLog {
+    pub id: i32,
+    pub grant_id: i32,
+    pub wallet_access_id: i32,
+    pub chain_id: i32,
+    pub eth_value: Vec<u8>,
+    pub signed_at: SqliteTimestamp,
+}
+
+#[derive(Models, Queryable, Debug, Insertable, Selectable)]
+#[diesel(table_name = evm_ether_transfer_grant, check_for_backend(Sqlite))]
+#[view(
+    NewEvmEtherTransferGrant,
+    derive(Insertable),
+    omit(id),
+    attributes_with = "deriveless"
+)]
+pub struct EvmEtherTransferGrant {
+    pub id: i32,
+    pub basic_grant_id: i32,
+    pub limit_id: i32, // references evm_ether_transfer_limit.id
+}
+
+#[derive(Models, Queryable, Debug, Insertable, Selectable)]
+#[diesel(table_name = evm_ether_transfer_grant_target, check_for_backend(Sqlite))]
+#[view(
+    NewEvmEtherTransferGrantTarget,
+    derive(Insertable),
+    omit(id),
+    attributes_with = "deriveless"
+)]
+pub struct EvmEtherTransferGrantTarget {
+    pub id: i32,
+    pub grant_id: i32,
+    pub address: Vec<u8>,
+}
+
+#[derive(Models, Queryable, Debug, Insertable, Selectable)]
+#[diesel(table_name = evm_token_transfer_grant, check_for_backend(Sqlite))]
+#[view(
+    NewEvmTokenTransferGrant,
+    derive(Insertable),
+    omit(id),
+    attributes_with = "deriveless"
+)]
+pub struct EvmTokenTransferGrant {
+    pub id: i32,
+    pub basic_grant_id: i32,
+    pub token_contract: Vec<u8>,
+    pub receiver: Option<Vec<u8>>,
+}
+
+#[derive(Models, Queryable, Debug, Insertable, Selectable)]
+#[diesel(table_name = evm_token_transfer_volume_limit, check_for_backend(Sqlite))]
+#[view(
+    NewEvmTokenTransferVolumeLimit,
+    derive(Insertable),
+    omit(id),
+    attributes_with = "deriveless"
+)]
+pub struct EvmTokenTransferVolumeLimit {
+    pub id: i32,
+    pub grant_id: i32,
+    pub window_secs: i32,
+    pub max_volume: Vec<u8>,
+}
+
+#[derive(Models, Queryable, Debug, Insertable, Selectable)]
+#[diesel(table_name = evm_token_transfer_log, check_for_backend(Sqlite))]
+#[view(
+    NewEvmTokenTransferLog,
+    derive(Insertable),
+    omit(id, created_at),
+    attributes_with = "deriveless"
+)]
+pub struct EvmTokenTransferLog {
+    pub id: i32,
+    pub grant_id: i32,
+    pub log_id: i32,
+    pub chain_id: i32,
+    pub token_contract: Vec<u8>,
+    pub recipient_address: Vec<u8>,
+    pub value: Vec<u8>,
+    pub created_at: SqliteTimestamp,
 }

server/crates/arbiter-server/src/db/schema.rs

@@ -20,11 +20,131 @@ diesel::table! {
     }
 }
 
+diesel::table! {
+    client_metadata (id) {
+        id -> Integer,
+        name -> Text,
+        description -> Nullable<Text>,
+        version -> Nullable<Text>,
+        created_at -> Integer,
+    }
+}
+
+diesel::table! {
+    client_metadata_history (id) {
+        id -> Integer,
+        metadata_id -> Integer,
+        client_id -> Integer,
+        created_at -> Integer,
+    }
+}
+
+diesel::table! {
+    evm_basic_grant (id) {
+        id -> Integer,
+        wallet_access_id -> Integer,
+        chain_id -> Integer,
+        valid_from -> Nullable<Integer>,
+        valid_until -> Nullable<Integer>,
+        max_gas_fee_per_gas -> Nullable<Binary>,
+        max_priority_fee_per_gas -> Nullable<Binary>,
+        rate_limit_count -> Nullable<Integer>,
+        rate_limit_window_secs -> Nullable<Integer>,
+        revoked_at -> Nullable<Integer>,
+        created_at -> Integer,
+    }
+}
+
+diesel::table! {
+    evm_ether_transfer_grant (id) {
+        id -> Integer,
+        basic_grant_id -> Integer,
+        limit_id -> Integer,
+    }
+}
+
+diesel::table! {
+    evm_ether_transfer_grant_target (id) {
+        id -> Integer,
+        grant_id -> Integer,
+        address -> Binary,
+    }
+}
+
+diesel::table! {
+    evm_ether_transfer_limit (id) {
+        id -> Integer,
+        window_secs -> Integer,
+        max_volume -> Binary,
+    }
+}
+
+diesel::table! {
+    evm_token_transfer_grant (id) {
+        id -> Integer,
+        basic_grant_id -> Integer,
+        token_contract -> Binary,
+        receiver -> Nullable<Binary>,
+    }
+}
+
+diesel::table! {
+    evm_token_transfer_log (id) {
+        id -> Integer,
+        grant_id -> Integer,
+        log_id -> Integer,
+        chain_id -> Integer,
+        token_contract -> Binary,
+        recipient_address -> Binary,
+        value -> Binary,
+        created_at -> Integer,
+    }
+}
+
+diesel::table! {
+    evm_token_transfer_volume_limit (id) {
+        id -> Integer,
+        grant_id -> Integer,
+        window_secs -> Integer,
+        max_volume -> Binary,
+    }
+}
+
+diesel::table! {
+    evm_transaction_log (id) {
+        id -> Integer,
+        wallet_access_id -> Integer,
+        grant_id -> Integer,
+        chain_id -> Integer,
+        eth_value -> Binary,
+        signed_at -> Integer,
+    }
+}
+
+diesel::table! {
+    evm_wallet (id) {
+        id -> Integer,
+        address -> Binary,
+        aead_encrypted_id -> Integer,
+        created_at -> Integer,
+    }
+}
+
+diesel::table! {
+    evm_wallet_access (id) {
+        id -> Integer,
+        wallet_id -> Integer,
+        client_id -> Integer,
+        created_at -> Integer,
+    }
+}
+
 diesel::table! {
     program_client (id) {
         id -> Integer,
         nonce -> Integer,
         public_key -> Binary,
+        metadata_id -> Integer,
         created_at -> Integer,
         updated_at -> Integer,
     }
@@ -58,6 +178,7 @@ diesel::table! {
         id -> Integer,
         nonce -> Integer,
         public_key -> Binary,
+        key_type -> Integer,
         created_at -> Integer,
         updated_at -> Integer,
     }
@@ -66,10 +187,38 @@ diesel::table! {
 diesel::joinable!(aead_encrypted -> root_key_history (associated_root_key_id));
 diesel::joinable!(arbiter_settings -> root_key_history (root_key_id));
 diesel::joinable!(arbiter_settings -> tls_history (tls_id));
+diesel::joinable!(client_metadata_history -> client_metadata (metadata_id));
+diesel::joinable!(client_metadata_history -> program_client (client_id));
+diesel::joinable!(evm_basic_grant -> evm_wallet_access (wallet_access_id));
+diesel::joinable!(evm_ether_transfer_grant -> evm_basic_grant (basic_grant_id));
+diesel::joinable!(evm_ether_transfer_grant -> evm_ether_transfer_limit (limit_id));
+diesel::joinable!(evm_ether_transfer_grant_target -> evm_ether_transfer_grant (grant_id));
+diesel::joinable!(evm_token_transfer_grant -> evm_basic_grant (basic_grant_id));
+diesel::joinable!(evm_token_transfer_log -> evm_token_transfer_grant (grant_id));
+diesel::joinable!(evm_token_transfer_log -> evm_transaction_log (log_id));
+diesel::joinable!(evm_token_transfer_volume_limit -> evm_token_transfer_grant (grant_id));
+diesel::joinable!(evm_transaction_log -> evm_basic_grant (grant_id));
+diesel::joinable!(evm_transaction_log -> evm_wallet_access (wallet_access_id));
+diesel::joinable!(evm_wallet -> aead_encrypted (aead_encrypted_id));
+diesel::joinable!(evm_wallet_access -> evm_wallet (wallet_id));
+diesel::joinable!(evm_wallet_access -> program_client (client_id));
+diesel::joinable!(program_client -> client_metadata (metadata_id));
 
 diesel::allow_tables_to_appear_in_same_query!(
     aead_encrypted,
     arbiter_settings,
+    client_metadata,
+    client_metadata_history,
+    evm_basic_grant,
+    evm_ether_transfer_grant,
+    evm_ether_transfer_grant_target,
+    evm_ether_transfer_limit,
+    evm_token_transfer_grant,
+    evm_token_transfer_log,
+    evm_token_transfer_volume_limit,
+    evm_transaction_log,
+    evm_wallet,
+    evm_wallet_access,
     program_client,
     root_key_history,
     tls_history,

server/crates/arbiter-server/src/evm/abi.rs

@@ -0,0 +1,84 @@
+use alloy::sol;
+
+sol! {
+    interface IERC20 {
+        event Transfer(address indexed from, address indexed to, uint256 value);
+        event Approval(address indexed owner, address indexed spender, uint256 value);
+
+        function totalSupply() external view returns (uint256);
+        function balanceOf(address account) external view returns (uint256);
+        function transfer(address to, uint256 value) external returns (bool);
+        function allowance(address owner, address spender) external view returns (uint256);
+        function approve(address spender, uint256 value) external returns (bool);
+        function transferFrom(address from, address to, uint256 value) external returns (bool);
+    }
+}
+
+sol! {
+    /// ERC-721: Non-Fungible Token Standard.
+    #[derive(Debug)]
+    interface IERC721 {
+        event Transfer(address indexed from, address indexed to, uint256 indexed tokenId);
+        event Approval(address indexed owner, address indexed approved, uint256 indexed tokenId);
+        event ApprovalForAll(address indexed owner, address indexed operator, bool approved);
+
+        function balanceOf(address owner) external view returns (uint256 balance);
+        function ownerOf(uint256 tokenId) external view returns (address owner);
+        function safeTransferFrom(address from, address to, uint256 tokenId) external;
+        function safeTransferFrom(address from, address to, uint256 tokenId, bytes calldata data) external;
+        function transferFrom(address from, address to, uint256 tokenId) external;
+        function approve(address to, uint256 tokenId) external;
+        function setApprovalForAll(address operator, bool approved) external;
+        function getApproved(uint256 tokenId) external view returns (address operator);
+        function isApprovedForAll(address owner, address operator) external view returns (bool);
+    }
+}
+
+sol! {
+    /// Wrapped Ether — the only functions beyond ERC-20 that matter.
+    #[derive(Debug)]
+    interface IWETH {
+        function deposit() external payable;
+        function withdraw(uint256 wad) external;
+    }
+}
+
+sol! {
+    /// Permit2 — Uniswap's canonical token approval manager.
+    /// Replaces per-contract ERC-20 approve() with a single approval hub.
+    #[derive(Debug)]
+    interface IPermit2 {
+        struct TokenPermissions {
+            address token;
+            uint256 amount;
+        }
+
+        struct PermitSingle {
+            TokenPermissions details;
+            address spender;
+            uint256 sigDeadline;
+        }
+
+        struct PermitBatch {
+            TokenPermissions[] details;
+            address spender;
+            uint256 sigDeadline;
+        }
+
+        struct AllowanceTransferDetails {
+            address from;
+            address to;
+            uint160 amount;
+            address token;
+        }
+
+        function approve(address token, address spender, uint160 amount, uint48 expiration) external;
+        function permit(address owner, PermitSingle calldata permitSingle, bytes calldata signature) external;
+        function permit(address owner, PermitBatch calldata permitBatch, bytes calldata signature) external;
+        function transferFrom(address from, address to, uint160 amount, address token) external;
+        function transferFrom(AllowanceTransferDetails[] calldata transferDetails) external;
+
+        function allowance(address user, address token, address spender)
+            external view returns (uint160 amount, uint48 expiration, uint48 nonce);
+    }
+}

server/crates/arbiter-server/src/evm/mod.rs

@@ -0,0 +1,299 @@
+pub mod abi;
+pub mod safe_signer;
+
+use alloy::{
+    consensus::TxEip1559,
+    primitives::{TxKind, U256},
+};
+use chrono::Utc;
+use diesel::{ExpressionMethods as _, QueryDsl as _, QueryResult, insert_into, sqlite::Sqlite};
+use diesel_async::{AsyncConnection, RunQueryDsl};
+
+use crate::{
+    db::{
+        self, DatabaseError,
+        models::{
+            EvmBasicGrant, EvmWalletAccess, NewEvmBasicGrant, NewEvmTransactionLog, SqliteTimestamp,
+        },
+        schema::{self, evm_transaction_log},
+    },
+    evm::policies::{
+        DatabaseID, EvalContext, EvalViolation, FullGrant, Grant, Policy, SharedGrantSettings,
+        SpecificGrant, SpecificMeaning, ether_transfer::EtherTransfer,
+        token_transfers::TokenTransfer,
+    },
+};
+
+pub mod policies;
+mod utils;
+
+/// Errors that can only occur once the transaction meaning is known (during policy evaluation)
+#[derive(Debug, thiserror::Error)]
+pub enum PolicyError {
+    #[error("Database error")]
+    Database(#[from] crate::db::DatabaseError),
+    #[error("Transaction violates policy: {0:?}")]
+    Violations(Vec<EvalViolation>),
+    #[error("No matching grant found")]
+    NoMatchingGrant,
+}
+
+#[derive(Debug, thiserror::Error)]
+pub enum VetError {
+    #[error("Contract creation transactions are not supported")]
+    ContractCreationNotSupported,
+    #[error("Engine can't classify this transaction")]
+    UnsupportedTransactionType,
+    #[error("Policy evaluation failed: {1}")]
+    Evaluated(SpecificMeaning, #[source] PolicyError),
+}
+
+#[derive(Debug, thiserror::Error)]
+pub enum AnalyzeError {
+    #[error("Engine doesn't support granting permissions for contract creation")]
+    ContractCreationNotSupported,
+
+    #[error("Unsupported transaction type")]
+    UnsupportedTransactionType,
+}
+
+/// Controls whether a transaction should be executed or only validated
+#[derive(Debug, Clone, Copy, PartialEq, Eq)]
+pub enum RunKind {
+    /// Validate and record the transaction
+    Execution,
+    /// Validate only, do not record
+    CheckOnly,
+}
+
+async fn check_shared_constraints(
+    context: &EvalContext,
+    shared: &SharedGrantSettings,
+    shared_grant_id: DatabaseID,
+    conn: &mut impl AsyncConnection<Backend = Sqlite>,
+) -> QueryResult<Vec<EvalViolation>> {
+    let mut violations = Vec::new();
+    let now = Utc::now();
+
+    // Validity window
+    if shared.valid_from.is_some_and(|t| now < t) || shared.valid_until.is_some_and(|t| now > t) {
+        violations.push(EvalViolation::InvalidTime);
+    }
+
+    // Gas fee caps
+    let fee_exceeded = shared
+        .max_gas_fee_per_gas
+        .is_some_and(|cap| U256::from(context.max_fee_per_gas) > cap);
+    let priority_exceeded = shared
+        .max_priority_fee_per_gas
+        .is_some_and(|cap| U256::from(context.max_priority_fee_per_gas) > cap);
+    if fee_exceeded || priority_exceeded {
+        violations.push(EvalViolation::GasLimitExceeded {
+            max_gas_fee_per_gas: shared.max_gas_fee_per_gas,
+            max_priority_fee_per_gas: shared.max_priority_fee_per_gas,
+        });
+    }
+
+    // Transaction count rate limit
+    if let Some(rate_limit) = &shared.rate_limit {
+        let window_start = SqliteTimestamp(now - rate_limit.window);
+        let count: i64 = evm_transaction_log::table
+            .filter(evm_transaction_log::grant_id.eq(shared_grant_id))
+            .filter(evm_transaction_log::signed_at.ge(window_start))
+            .count()
+            .get_result(conn)
+            .await?;
+
+        if count >= rate_limit.count as i64 {
+            violations.push(EvalViolation::RateLimitExceeded);
+        }
+    }
+
+    Ok(violations)
+}
+
+// Supporting only EIP-1559 transactions for now, but we can easily extend this to support legacy transactions if needed
+pub struct Engine {
+    db: db::DatabasePool,
+}
+
+impl Engine {
+    async fn vet_transaction<P: Policy>(
+        &self,
+        context: EvalContext,
+        meaning: &P::Meaning,
+        run_kind: RunKind,
+    ) -> Result<(), PolicyError> {
+        let mut conn = self.db.get().await.map_err(DatabaseError::from)?;
+
+        let grant = P::try_find_grant(&context, &mut conn)
+            .await
+            .map_err(DatabaseError::from)?
+            .ok_or(PolicyError::NoMatchingGrant)?;
+
+        let mut violations =
+            check_shared_constraints(&context, &grant.shared, grant.shared_grant_id, &mut conn)
+                .await
+                .map_err(DatabaseError::from)?;
+        violations.extend(
+            P::evaluate(&context, meaning, &grant, &mut conn)
+                .await
+                .map_err(DatabaseError::from)?,
+        );
+
+        if !violations.is_empty() {
+            return Err(PolicyError::Violations(violations));
+        } else if run_kind == RunKind::Execution {
+            conn.transaction(|conn| {
+                Box::pin(async move {
+                    let log_id: i32 = insert_into(evm_transaction_log::table)
+                        .values(&NewEvmTransactionLog {
+                            grant_id: grant.shared_grant_id,
+                            wallet_access_id: context.target.id,
+                            chain_id: context.chain as i32,
+                            eth_value: utils::u256_to_bytes(context.value).to_vec(),
+                            signed_at: Utc::now().into(),
+                        })
+                        .returning(evm_transaction_log::id)
+                        .get_result(conn)
+                        .await?;
+
+                    P::record_transaction(&context, meaning, log_id, &grant, conn).await?;
+
+                    QueryResult::Ok(())
+                })
+            })
+            .await
+            .map_err(DatabaseError::from)?;
+        }
+
+        Ok(())
+    }
+}
+
+impl Engine {
+    pub fn new(db: db::DatabasePool) -> Self {
+        Self { db }
+    }
+
+    pub async fn create_grant<P: Policy>(
+        &self,
+        full_grant: FullGrant<P::Settings>,
+    ) -> Result<i32, DatabaseError> {
+        let mut conn = self.db.get().await?;
+
+        let id = conn
+            .transaction(|conn| {
+                Box::pin(async move {
+                    use schema::evm_basic_grant;
+
+                    let basic_grant: EvmBasicGrant = insert_into(evm_basic_grant::table)
+                        .values(&NewEvmBasicGrant {
+                            chain_id: full_grant.basic.chain as i32,
+                            wallet_access_id: full_grant.basic.wallet_access_id,
+                            valid_from: full_grant.basic.valid_from.map(SqliteTimestamp),
+                            valid_until: full_grant.basic.valid_until.map(SqliteTimestamp),
+                            max_gas_fee_per_gas: full_grant
+                                .basic
+                                .max_gas_fee_per_gas
+                                .map(|fee| utils::u256_to_bytes(fee).to_vec()),
+                            max_priority_fee_per_gas: full_grant
+                                .basic
+                                .max_priority_fee_per_gas
+                                .map(|fee| utils::u256_to_bytes(fee).to_vec()),
+                            rate_limit_count: full_grant
+                                .basic
+                                .rate_limit
+                                .as_ref()
+                                .map(|rl| rl.count as i32),
+                            rate_limit_window_secs: full_grant
+                                .basic
+                                .rate_limit
+                                .as_ref()
+                                .map(|rl| rl.window.num_seconds() as i32),
+                            revoked_at: None,
+                        })
+                        .returning(evm_basic_grant::all_columns)
+                        .get_result(conn)
+                        .await?;
+
+                    P::create_grant(&basic_grant, &full_grant.specific, conn).await
+                })
+            })
+            .await?;
+
+        Ok(id)
+    }
+
+    pub async fn list_all_grants(&self) -> Result<Vec<Grant<SpecificGrant>>, DatabaseError> {
+        let mut conn = self.db.get().await?;
+
+        let mut grants: Vec<Grant<SpecificGrant>> = Vec::new();
+
+        grants.extend(
+            EtherTransfer::find_all_grants(&mut conn)
+                .await?
+                .into_iter()
+                .map(|g| Grant {
+                    id: g.id,
+                    shared_grant_id: g.shared_grant_id,
+                    shared: g.shared,
+                    settings: SpecificGrant::EtherTransfer(g.settings),
+                }),
+        );
+        grants.extend(
+            TokenTransfer::find_all_grants(&mut conn)
+                .await?
+                .into_iter()
+                .map(|g| Grant {
+                    id: g.id,
+                    shared_grant_id: g.shared_grant_id,
+                    shared: g.shared,
+                    settings: SpecificGrant::TokenTransfer(g.settings),
+                }),
+        );
+
+        Ok(grants)
+    }
+
+    pub async fn evaluate_transaction(
+        &self,
+        target: EvmWalletAccess,
+        transaction: TxEip1559,
+        run_kind: RunKind,
+    ) -> Result<SpecificMeaning, VetError> {
+        let TxKind::Call(to) = transaction.to else {
+            return Err(VetError::ContractCreationNotSupported);
+        };
+        let context = policies::EvalContext {
+            target,
+            chain: transaction.chain_id,
+            to,
+            value: transaction.value,
+            calldata: transaction.input.clone(),
+            max_fee_per_gas: transaction.max_fee_per_gas,
+            max_priority_fee_per_gas: transaction.max_priority_fee_per_gas,
+        };
+
+        if let Some(meaning) = EtherTransfer::analyze(&context) {
+            return match self
+                .vet_transaction::<EtherTransfer>(context, &meaning, run_kind)
+                .await
+            {
+                Ok(()) => Ok(meaning.into()),
+                Err(e) => Err(VetError::Evaluated(meaning.into(), e)),
+            };
+        }
+        if let Some(meaning) = TokenTransfer::analyze(&context) {
+            return match self
+                .vet_transaction::<TokenTransfer>(context, &meaning, run_kind)
+                .await
+            {
+                Ok(()) => Ok(meaning.into()),
+                Err(e) => Err(VetError::Evaluated(meaning.into(), e)),
+            };
+        }
+
+        Err(VetError::UnsupportedTransactionType)
+    }
+}

server/crates/arbiter-server/src/evm/policies.rs

@@ -0,0 +1,203 @@
+use std::fmt::Display;
+
+use alloy::primitives::{Address, Bytes, ChainId, U256};
+use chrono::{DateTime, Duration, Utc};
+use diesel::{
+    ExpressionMethods as _, QueryDsl, SelectableHelper, result::QueryResult, sqlite::Sqlite,
+};
+use diesel_async::{AsyncConnection, RunQueryDsl};
+
+use thiserror::Error;
+
+use crate::{
+    db::models::{self, EvmBasicGrant, EvmWalletAccess},
+    evm::utils,
+};
+
+pub mod ether_transfer;
+pub mod token_transfers;
+
+#[derive(Debug, Clone)]
+pub struct EvalContext {
+    // Which wallet is this transaction for and who requested it
+    pub target: EvmWalletAccess,
+
+    // The transaction data
+    pub chain: ChainId,
+    pub to: Address,
+    pub value: U256,
+    pub calldata: Bytes,
+
+    // Gas pricing (EIP-1559)
+    pub max_fee_per_gas: u128,
+    pub max_priority_fee_per_gas: u128,
+}
+
+#[derive(Debug, Error)]
+pub enum EvalViolation {
+    #[error("This grant doesn't allow transactions to the target address {target}")]
+    InvalidTarget { target: Address },
+
+    #[error("Gas limit exceeded for this grant")]
+    GasLimitExceeded {
+        max_gas_fee_per_gas: Option<U256>,
+        max_priority_fee_per_gas: Option<U256>,
+    },
+
+    #[error("Rate limit exceeded for this grant")]
+    RateLimitExceeded,
+
+    #[error("Transaction exceeds volumetric limits of the grant")]
+    VolumetricLimitExceeded,
+
+    #[error("Transaction is outside of the grant's validity period")]
+    InvalidTime,
+
+    #[error("Transaction type is not allowed by this grant")]
+    InvalidTransactionType,
+}
+
+pub type DatabaseID = i32;
+
+#[derive(Debug)]
+pub struct Grant<PolicySettings> {
+    pub id: DatabaseID,
+    pub shared_grant_id: DatabaseID, // ID of the basic grant for shared-logic checks like rate limits and validity periods
+    pub shared: SharedGrantSettings,
+    pub settings: PolicySettings,
+}
+
+pub trait Policy: Sized {
+    type Settings: Send + Sync + 'static + Into<SpecificGrant>;
+    type Meaning: Display + std::fmt::Debug + Send + Sync + 'static + Into<SpecificMeaning>;
+
+    fn analyze(context: &EvalContext) -> Option<Self::Meaning>;
+
+    // Evaluate whether a transaction with the given meaning complies with the provided grant, and return any violations if not
+    // Empty vector means transaction is compliant with the grant
+    fn evaluate(
+        context: &EvalContext,
+        meaning: &Self::Meaning,
+        grant: &Grant<Self::Settings>,
+        db: &mut impl AsyncConnection<Backend = Sqlite>,
+    ) -> impl Future<Output = QueryResult<Vec<EvalViolation>>> + Send;
+
+    // Create a new grant in the database based on the provided grant details, and return its ID
+    fn create_grant(
+        basic: &models::EvmBasicGrant,
+        grant: &Self::Settings,
+        conn: &mut impl AsyncConnection<Backend = Sqlite>,
+    ) -> impl std::future::Future<Output = QueryResult<DatabaseID>> + Send;
+
+    // Try to find an existing grant that matches the transaction context, and return its details if found
+    // Additionally, return ID of basic grant for shared-logic checks like rate limits and validity periods
+    fn try_find_grant(
+        context: &EvalContext,
+        conn: &mut impl AsyncConnection<Backend = Sqlite>,
+    ) -> impl Future<Output = QueryResult<Option<Grant<Self::Settings>>>> + Send;
+
+    // Return all non-revoked grants, eagerly loading policy-specific settings
+    fn find_all_grants(
+        conn: &mut impl AsyncConnection<Backend = Sqlite>,
+    ) -> impl Future<Output = QueryResult<Vec<Grant<Self::Settings>>>> + Send;
+
+    // Records, updates or deletes rate limits
+    // In other words, records grant-specific things after transaction is executed
+    fn record_transaction(
+        context: &EvalContext,
+        meaning: &Self::Meaning,
+        log_id: i32,
+        grant: &Grant<Self::Settings>,
+        conn: &mut impl AsyncConnection<Backend = Sqlite>,
+    ) -> impl Future<Output = QueryResult<()>> + Send;
+}
+
+pub enum ReceiverTarget {
+    Specific(Vec<Address>), // only allow transfers to these addresses
+    Any,                    // allow transfers to any address
+}
+
+// Classification of what transaction does
+#[derive(Debug)]
+pub enum SpecificMeaning {
+    EtherTransfer(ether_transfer::Meaning),
+    TokenTransfer(token_transfers::Meaning),
+}
+
+#[derive(Clone, Debug, PartialEq, Eq, Hash)]
+pub struct TransactionRateLimit {
+    pub count: u32,
+    pub window: Duration,
+}
+
+#[derive(Clone, Debug, PartialEq, Eq, Hash)]
+pub struct VolumeRateLimit {
+    pub max_volume: U256,
+    pub window: Duration,
+}
+
+#[derive(Clone, Debug, PartialEq, Eq, Hash)]
+pub struct SharedGrantSettings {
+    pub wallet_access_id: i32,
+    pub chain: ChainId,
+
+    pub valid_from: Option<DateTime<Utc>>,
+    pub valid_until: Option<DateTime<Utc>>,
+
+    pub max_gas_fee_per_gas: Option<U256>,
+    pub max_priority_fee_per_gas: Option<U256>,
+
+    pub rate_limit: Option<TransactionRateLimit>,
+}
+
+impl SharedGrantSettings {
+    fn try_from_model(model: EvmBasicGrant) -> QueryResult<Self> {
+        Ok(Self {
+            wallet_access_id: model.wallet_access_id,
+            chain: model.chain_id as u64, // safe because chain_id is stored as i32 but is guaranteed to be a valid ChainId by the API when creating grants
+            valid_from: model.valid_from.map(Into::into),
+            valid_until: model.valid_until.map(Into::into),
+            max_gas_fee_per_gas: model
+                .max_gas_fee_per_gas
+                .map(|b| utils::try_bytes_to_u256(&b))
+                .transpose()?,
+            max_priority_fee_per_gas: model
+                .max_priority_fee_per_gas
+                .map(|b| utils::try_bytes_to_u256(&b))
+                .transpose()?,
+            rate_limit: match (model.rate_limit_count, model.rate_limit_window_secs) {
+                (Some(count), Some(window_secs)) => Some(TransactionRateLimit {
+                    count: count as u32,
+                    window: Duration::seconds(window_secs as i64),
+                }),
+                _ => None,
+            },
+        })
+    }
+
+    pub async fn query_by_id(
+        conn: &mut impl AsyncConnection<Backend = Sqlite>,
+        id: i32,
+    ) -> diesel::result::QueryResult<Self> {
+        use crate::db::schema::evm_basic_grant;
+
+        let basic_grant: EvmBasicGrant = evm_basic_grant::table
+            .select(EvmBasicGrant::as_select())
+            .filter(evm_basic_grant::id.eq(id))
+            .first::<EvmBasicGrant>(conn)
+            .await?;
+
+        Self::try_from_model(basic_grant)
+    }
+}
+
+#[derive(Debug, Clone)]
+pub enum SpecificGrant {
+    EtherTransfer(ether_transfer::Settings),
+    TokenTransfer(token_transfers::Settings),
+}
+
+pub struct FullGrant<PolicyGrant> {
+    pub basic: SharedGrantSettings,
+    pub specific: PolicyGrant,
+}

server/crates/arbiter-server/src/evm/policies/ether_transfer/mod.rs

@@ -0,0 +1,348 @@
+use std::collections::HashMap;
+use std::fmt::Display;
+
+use alloy::primitives::{Address, U256};
+use chrono::{DateTime, Duration, Utc};
+use diesel::dsl::{auto_type, insert_into};
+use diesel::sqlite::Sqlite;
+use diesel::{ExpressionMethods, JoinOnDsl, prelude::*};
+use diesel_async::{AsyncConnection, RunQueryDsl};
+
+use crate::db::models::{
+    EvmBasicGrant, EvmEtherTransferGrant, EvmEtherTransferGrantTarget, EvmEtherTransferLimit,
+    NewEvmEtherTransferLimit, SqliteTimestamp,
+};
+use crate::db::schema::{evm_basic_grant, evm_ether_transfer_limit, evm_transaction_log};
+use crate::evm::policies::{
+    Grant, SharedGrantSettings, SpecificGrant, SpecificMeaning, VolumeRateLimit,
+};
+use crate::{
+    db::{
+        models::{self, NewEvmEtherTransferGrant, NewEvmEtherTransferGrantTarget},
+        schema::{evm_ether_transfer_grant, evm_ether_transfer_grant_target},
+    },
+    evm::{policies::Policy, utils},
+};
+
+#[auto_type]
+fn grant_join() -> _ {
+    evm_ether_transfer_grant::table.inner_join(
+        evm_basic_grant::table.on(evm_ether_transfer_grant::basic_grant_id.eq(evm_basic_grant::id)),
+    )
+}
+
+use super::{DatabaseID, EvalContext, EvalViolation};
+
+// Plain ether transfer
+#[derive(Clone, Debug, PartialEq, Eq, Hash)]
+pub struct Meaning {
+    pub(crate) to: Address,
+    pub(crate) value: U256,
+}
+impl Display for Meaning {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        write!(f, "Ether transfer of {} to {}", self.value, self.to)
+    }
+}
+impl From<Meaning> for SpecificMeaning {
+    fn from(val: Meaning) -> SpecificMeaning {
+        SpecificMeaning::EtherTransfer(val)
+    }
+}
+
+// A grant for ether transfers, which can be scoped to specific target addresses and volume limits
+#[derive(Debug, Clone)]
+pub struct Settings {
+    pub target: Vec<Address>,
+    pub limit: VolumeRateLimit,
+}
+
+impl From<Settings> for SpecificGrant {
+    fn from(val: Settings) -> SpecificGrant {
+        SpecificGrant::EtherTransfer(val)
+    }
+}
+
+async fn query_relevant_past_transaction(
+    grant_id: i32,
+    longest_window: Duration,
+    db: &mut impl AsyncConnection<Backend = Sqlite>,
+) -> QueryResult<Vec<(U256, DateTime<Utc>)>> {
+    let past_transactions: Vec<(Vec<u8>, SqliteTimestamp)> = evm_transaction_log::table
+        .filter(evm_transaction_log::grant_id.eq(grant_id))
+        .filter(
+            evm_transaction_log::signed_at.ge(SqliteTimestamp(chrono::Utc::now() - longest_window)),
+        )
+        .select((
+            evm_transaction_log::eth_value,
+            evm_transaction_log::signed_at,
+        ))
+        .load(db)
+        .await?;
+    let past_transaction: Vec<(U256, DateTime<Utc>)> = past_transactions
+        .into_iter()
+        .filter_map(|(value_bytes, timestamp)| {
+            let value = utils::bytes_to_u256(&value_bytes)?;
+            Some((value, timestamp.0))
+        })
+        .collect();
+    Ok(past_transaction)
+}
+
+async fn check_rate_limits(
+    grant: &Grant<Settings>,
+    current_transfer_value: U256,
+    db: &mut impl AsyncConnection<Backend = Sqlite>,
+) -> QueryResult<Vec<EvalViolation>> {
+    let mut violations = Vec::new();
+    let window = grant.settings.limit.window;
+
+    let past_transaction = query_relevant_past_transaction(grant.id, window, db).await?;
+
+    let window_start = chrono::Utc::now() - grant.settings.limit.window;
+    let prospective_cumulative_volume: U256 = past_transaction
+        .iter()
+        .filter(|(_, timestamp)| timestamp >= &window_start)
+        .fold(current_transfer_value, |acc, (value, _)| acc + *value);
+
+    if prospective_cumulative_volume > grant.settings.limit.max_volume {
+        violations.push(EvalViolation::VolumetricLimitExceeded);
+    }
+
+    Ok(violations)
+}
+
+pub struct EtherTransfer;
+impl Policy for EtherTransfer {
+    type Settings = Settings;
+
+    type Meaning = Meaning;
+
+    fn analyze(context: &EvalContext) -> Option<Self::Meaning> {
+        if !context.calldata.is_empty() {
+            return None;
+        }
+
+        Some(Meaning {
+            to: context.to,
+            value: context.value,
+        })
+    }
+
+    async fn evaluate(
+        _: &EvalContext,
+        meaning: &Self::Meaning,
+        grant: &Grant<Self::Settings>,
+        db: &mut impl AsyncConnection<Backend = Sqlite>,
+    ) -> QueryResult<Vec<EvalViolation>> {
+        let mut violations = Vec::new();
+
+        // Check if the target address is within the grant's allowed targets
+        if !grant.settings.target.contains(&meaning.to) {
+            violations.push(EvalViolation::InvalidTarget { target: meaning.to });
+        }
+
+        let rate_violations = check_rate_limits(grant, meaning.value, db).await?;
+        violations.extend(rate_violations);
+
+        Ok(violations)
+    }
+
+    async fn create_grant(
+        basic: &models::EvmBasicGrant,
+        grant: &Self::Settings,
+        conn: &mut impl AsyncConnection<Backend = Sqlite>,
+    ) -> diesel::result::QueryResult<DatabaseID> {
+        let limit_id: i32 = insert_into(evm_ether_transfer_limit::table)
+            .values(NewEvmEtherTransferLimit {
+                window_secs: grant.limit.window.num_seconds() as i32,
+                max_volume: utils::u256_to_bytes(grant.limit.max_volume).to_vec(),
+            })
+            .returning(evm_ether_transfer_limit::id)
+            .get_result(conn)
+            .await?;
+
+        let grant_id: i32 = insert_into(evm_ether_transfer_grant::table)
+            .values(&NewEvmEtherTransferGrant {
+                basic_grant_id: basic.id,
+                limit_id,
+            })
+            .returning(evm_ether_transfer_grant::id)
+            .get_result(conn)
+            .await?;
+
+        for target in &grant.target {
+            insert_into(evm_ether_transfer_grant_target::table)
+                .values(NewEvmEtherTransferGrantTarget {
+                    grant_id,
+                    address: target.to_vec(),
+                })
+                .execute(conn)
+                .await?;
+        }
+
+        Ok(grant_id)
+    }
+
+    async fn try_find_grant(
+        context: &EvalContext,
+        conn: &mut impl AsyncConnection<Backend = Sqlite>,
+    ) -> diesel::result::QueryResult<Option<Grant<Self::Settings>>> {
+        let target_bytes = context.to.to_vec();
+
+        // Find a grant where:
+        // 1. The basic grant's wallet_id and client_id match the context
+        // 2. Any of the grant's targets match the context's `to` address
+        let grant: Option<(EvmBasicGrant, EvmEtherTransferGrant)> = evm_ether_transfer_grant::table
+            .inner_join(evm_basic_grant::table)
+            .inner_join(evm_ether_transfer_grant_target::table)
+            .filter(
+                evm_basic_grant::wallet_access_id
+                    .eq(context.target.id)
+                    .and(evm_basic_grant::revoked_at.is_null())
+                    .and(evm_ether_transfer_grant_target::address.eq(&target_bytes)),
+            )
+            .select((
+                EvmBasicGrant::as_select(),
+                EvmEtherTransferGrant::as_select(),
+            ))
+            .first(conn)
+            .await
+            .optional()?;
+
+        let Some((basic_grant, grant)) = grant else {
+            return Ok(None);
+        };
+
+        let target_bytes: Vec<EvmEtherTransferGrantTarget> = evm_ether_transfer_grant_target::table
+            .select(EvmEtherTransferGrantTarget::as_select())
+            .filter(evm_ether_transfer_grant_target::grant_id.eq(grant.id))
+            .load(conn)
+            .await?;
+
+        let limit: EvmEtherTransferLimit = evm_ether_transfer_limit::table
+            .filter(evm_ether_transfer_limit::id.eq(grant.limit_id))
+            .select(EvmEtherTransferLimit::as_select())
+            .first::<EvmEtherTransferLimit>(conn)
+            .await?;
+
+        // Convert bytes back to Address
+        let targets: Vec<Address> = target_bytes
+            .into_iter()
+            .filter_map(|target| {
+                // TODO: Handle invalid addresses more gracefully
+                let arr: [u8; 20] = target.address.try_into().ok()?;
+                Some(Address::from(arr))
+            })
+            .collect();
+
+        let settings = Settings {
+            target: targets,
+            limit: VolumeRateLimit {
+                max_volume: utils::try_bytes_to_u256(&limit.max_volume)
+                    .map_err(|err| diesel::result::Error::DeserializationError(Box::new(err)))?,
+                window: chrono::Duration::seconds(limit.window_secs as i64),
+            },
+        };
+
+        Ok(Some(Grant {
+            id: grant.id,
+            shared_grant_id: grant.basic_grant_id,
+            shared: SharedGrantSettings::try_from_model(basic_grant)?,
+            settings,
+        }))
+    }
+
+    async fn record_transaction(
+        _context: &EvalContext,
+        _: &Self::Meaning,
+        _log_id: i32,
+        _grant: &Grant<Self::Settings>,
+        _conn: &mut impl AsyncConnection<Backend = Sqlite>,
+    ) -> diesel::result::QueryResult<()> {
+        // Basic log is sufficient
+
+        Ok(())
+    }
+
+    async fn find_all_grants(
+        conn: &mut impl AsyncConnection<Backend = Sqlite>,
+    ) -> QueryResult<Vec<Grant<Self::Settings>>> {
+        let grants: Vec<(EvmBasicGrant, EvmEtherTransferGrant)> = grant_join()
+            .filter(evm_basic_grant::revoked_at.is_null())
+            .select((
+                EvmBasicGrant::as_select(),
+                EvmEtherTransferGrant::as_select(),
+            ))
+            .load(conn)
+            .await?;
+
+        if grants.is_empty() {
+            return Ok(Vec::new());
+        }
+
+        let grant_ids: Vec<i32> = grants.iter().map(|(_, g)| g.id).collect();
+        let limit_ids: Vec<i32> = grants.iter().map(|(_, g)| g.limit_id).collect();
+
+        let all_targets: Vec<EvmEtherTransferGrantTarget> = evm_ether_transfer_grant_target::table
+            .filter(evm_ether_transfer_grant_target::grant_id.eq_any(&grant_ids))
+            .select(EvmEtherTransferGrantTarget::as_select())
+            .load(conn)
+            .await?;
+
+        let all_limits: Vec<EvmEtherTransferLimit> = evm_ether_transfer_limit::table
+            .filter(evm_ether_transfer_limit::id.eq_any(&limit_ids))
+            .select(EvmEtherTransferLimit::as_select())
+            .load(conn)
+            .await?;
+
+        let mut targets_by_grant: HashMap<i32, Vec<EvmEtherTransferGrantTarget>> = HashMap::new();
+        for target in all_targets {
+            targets_by_grant
+                .entry(target.grant_id)
+                .or_default()
+                .push(target);
+        }
+
+        let limits_by_id: HashMap<i32, EvmEtherTransferLimit> =
+            all_limits.into_iter().map(|l| (l.id, l)).collect();
+
+        grants
+            .into_iter()
+            .map(|(basic, specific)| {
+                let targets: Vec<Address> = targets_by_grant
+                    .get(&specific.id)
+                    .map(|v| v.as_slice())
+                    .unwrap_or_default()
+                    .iter()
+                    .filter_map(|t| {
+                        let arr: [u8; 20] = t.address.clone().try_into().ok()?;
+                        Some(Address::from(arr))
+                    })
+                    .collect();
+
+                let limit = limits_by_id
+                    .get(&specific.limit_id)
+                    .ok_or(diesel::result::Error::NotFound)?;
+
+                Ok(Grant {
+                    id: specific.id,
+                    shared_grant_id: specific.basic_grant_id,
+                    shared: SharedGrantSettings::try_from_model(basic)?,
+                    settings: Settings {
+                        target: targets,
+                        limit: VolumeRateLimit {
+                            max_volume: utils::try_bytes_to_u256(&limit.max_volume).map_err(
+                                |e| diesel::result::Error::DeserializationError(Box::new(e)),
+                            )?,
+                            window: Duration::seconds(limit.window_secs as i64),
+                        },
+                    },
+                })
+            })
+            .collect()
+    }
+}
+
+#[cfg(test)]
+mod tests;

server/crates/arbiter-server/src/evm/policies/ether_transfer/tests.rs

@@ -0,0 +1,386 @@
+use alloy::primitives::{Address, Bytes, U256, address};
+use chrono::{Duration, Utc};
+use diesel::{SelectableHelper, insert_into};
+use diesel_async::RunQueryDsl;
+
+use crate::db::{
+    self, DatabaseConnection,
+    models::{
+        EvmBasicGrant, EvmWalletAccess, NewEvmBasicGrant, NewEvmTransactionLog, SqliteTimestamp,
+    },
+    schema::{evm_basic_grant, evm_transaction_log},
+};
+use crate::evm::{
+    policies::{EvalContext, EvalViolation, Grant, Policy, SharedGrantSettings, VolumeRateLimit},
+    utils,
+};
+
+use super::{EtherTransfer, Settings};
+
+const WALLET_ACCESS_ID: i32 = 1;
+const CHAIN_ID: u64 = 1;
+
+const ALLOWED: Address = address!("1111111111111111111111111111111111111111");
+const OTHER: Address = address!("2222222222222222222222222222222222222222");
+
+fn ctx(to: Address, value: U256) -> EvalContext {
+    EvalContext {
+        target: EvmWalletAccess {
+            id: WALLET_ACCESS_ID,
+            wallet_id: 10,
+            client_id: 20,
+            created_at: SqliteTimestamp(Utc::now()),
+        },
+        chain: CHAIN_ID,
+        to,
+        value,
+        calldata: Bytes::new(),
+        max_fee_per_gas: 0,
+        max_priority_fee_per_gas: 0,
+    }
+}
+
+async fn insert_basic(conn: &mut DatabaseConnection, revoked: bool) -> EvmBasicGrant {
+    insert_into(evm_basic_grant::table)
+        .values(NewEvmBasicGrant {
+            wallet_access_id: WALLET_ACCESS_ID,
+            chain_id: CHAIN_ID as i32,
+            valid_from: None,
+            valid_until: None,
+            max_gas_fee_per_gas: None,
+            max_priority_fee_per_gas: None,
+            rate_limit_count: None,
+            rate_limit_window_secs: None,
+            revoked_at: revoked.then(|| SqliteTimestamp(Utc::now())),
+        })
+        .returning(EvmBasicGrant::as_select())
+        .get_result(conn)
+        .await
+        .unwrap()
+}
+
+fn make_settings(targets: Vec<Address>, max_volume: u64) -> Settings {
+    Settings {
+        target: targets,
+        limit: VolumeRateLimit {
+            max_volume: U256::from(max_volume),
+            window: Duration::hours(1),
+        },
+    }
+}
+
+fn shared() -> SharedGrantSettings {
+    SharedGrantSettings {
+        wallet_access_id: WALLET_ACCESS_ID,
+        chain: CHAIN_ID,
+        valid_from: None,
+        valid_until: None,
+        max_gas_fee_per_gas: None,
+        max_priority_fee_per_gas: None,
+        rate_limit: None,
+    }
+}
+
+// ── analyze ─────────────────────────────────────────────────────────────
+
+#[test]
+fn analyze_matches_empty_calldata() {
+    let m = EtherTransfer::analyze(&ctx(ALLOWED, U256::from(1_000u64))).unwrap();
+    assert_eq!(m.to, ALLOWED);
+    assert_eq!(m.value, U256::from(1_000u64));
+}
+
+#[test]
+fn analyze_rejects_nonempty_calldata() {
+    let context = EvalContext {
+        calldata: Bytes::from(vec![0xde, 0xad, 0xbe, 0xef]),
+        ..ctx(ALLOWED, U256::from(1u64))
+    };
+    assert!(EtherTransfer::analyze(&context).is_none());
+}
+
+// ── evaluate ────────────────────────────────────────────────────────────
+
+#[tokio::test]
+async fn evaluate_passes_for_allowed_target() {
+    let db = db::create_test_pool().await;
+    let mut conn = db.get().await.unwrap();
+
+    let grant = Grant {
+        id: 999,
+        shared_grant_id: 999,
+        shared: shared(),
+        settings: make_settings(vec![ALLOWED], 1_000_000),
+    };
+    let context = ctx(ALLOWED, U256::from(100u64));
+    let m = EtherTransfer::analyze(&context).unwrap();
+    let v = EtherTransfer::evaluate(&context, &m, &grant, &mut *conn)
+        .await
+        .unwrap();
+    assert!(v.is_empty());
+}
+
+#[tokio::test]
+async fn evaluate_rejects_disallowed_target() {
+    let db = db::create_test_pool().await;
+    let mut conn = db.get().await.unwrap();
+
+    let grant = Grant {
+        id: 999,
+        shared_grant_id: 999,
+        shared: shared(),
+        settings: make_settings(vec![ALLOWED], 1_000_000),
+    };
+    let context = ctx(OTHER, U256::from(100u64));
+    let m = EtherTransfer::analyze(&context).unwrap();
+    let v = EtherTransfer::evaluate(&context, &m, &grant, &mut *conn)
+        .await
+        .unwrap();
+    assert!(
+        v.iter()
+            .any(|e| matches!(e, EvalViolation::InvalidTarget { .. }))
+    );
+}
+
+#[tokio::test]
+async fn evaluate_passes_when_volume_within_limit() {
+    let db = db::create_test_pool().await;
+    let mut conn = db.get().await.unwrap();
+
+    let basic = insert_basic(&mut conn, false).await;
+    let settings = make_settings(vec![ALLOWED], 1_000);
+    let grant_id = EtherTransfer::create_grant(&basic, &settings, &mut *conn)
+        .await
+        .unwrap();
+
+    insert_into(evm_transaction_log::table)
+        .values(NewEvmTransactionLog {
+            grant_id,
+            wallet_access_id: WALLET_ACCESS_ID,
+            chain_id: CHAIN_ID as i32,
+            eth_value: utils::u256_to_bytes(U256::from(500u64)).to_vec(),
+            signed_at: SqliteTimestamp(Utc::now()),
+        })
+        .execute(&mut *conn)
+        .await
+        .unwrap();
+
+    let grant = Grant {
+        id: grant_id,
+        shared_grant_id: basic.id,
+        shared: shared(),
+        settings,
+    };
+    let context = ctx(ALLOWED, U256::from(100u64));
+    let m = EtherTransfer::analyze(&context).unwrap();
+    let v = EtherTransfer::evaluate(&context, &m, &grant, &mut *conn)
+        .await
+        .unwrap();
+    assert!(
+        !v.iter()
+            .any(|e| matches!(e, EvalViolation::VolumetricLimitExceeded))
+    );
+}
+
+#[tokio::test]
+async fn evaluate_rejects_volume_over_limit() {
+    let db = db::create_test_pool().await;
+    let mut conn = db.get().await.unwrap();
+
+    let basic = insert_basic(&mut conn, false).await;
+    let settings = make_settings(vec![ALLOWED], 1_000);
+    let grant_id = EtherTransfer::create_grant(&basic, &settings, &mut *conn)
+        .await
+        .unwrap();
+
+    insert_into(evm_transaction_log::table)
+        .values(NewEvmTransactionLog {
+            grant_id,
+            wallet_access_id: WALLET_ACCESS_ID,
+            chain_id: CHAIN_ID as i32,
+            eth_value: utils::u256_to_bytes(U256::from(1_000u64)).to_vec(),
+            signed_at: SqliteTimestamp(Utc::now()),
+        })
+        .execute(&mut *conn)
+        .await
+        .unwrap();
+
+    let grant = Grant {
+        id: grant_id,
+        shared_grant_id: basic.id,
+        shared: shared(),
+        settings,
+    };
+    let context = ctx(ALLOWED, U256::from(1u64));
+    let m = EtherTransfer::analyze(&context).unwrap();
+    let v = EtherTransfer::evaluate(&context, &m, &grant, &mut *conn)
+        .await
+        .unwrap();
+    assert!(
+        v.iter()
+            .any(|e| matches!(e, EvalViolation::VolumetricLimitExceeded))
+    );
+}
+
+#[tokio::test]
+async fn evaluate_passes_at_exactly_volume_limit() {
+    let db = db::create_test_pool().await;
+    let mut conn = db.get().await.unwrap();
+
+    let basic = insert_basic(&mut conn, false).await;
+    let settings = make_settings(vec![ALLOWED], 1_000);
+    let grant_id = EtherTransfer::create_grant(&basic, &settings, &mut *conn)
+        .await
+        .unwrap();
+
+    // Exactly at the limit including current transfer — check is `>`, so this should not violate
+    insert_into(evm_transaction_log::table)
+        .values(NewEvmTransactionLog {
+            grant_id,
+            wallet_access_id: WALLET_ACCESS_ID,
+            chain_id: CHAIN_ID as i32,
+            eth_value: utils::u256_to_bytes(U256::from(900u64)).to_vec(),
+            signed_at: SqliteTimestamp(Utc::now()),
+        })
+        .execute(&mut *conn)
+        .await
+        .unwrap();
+
+    let grant = Grant {
+        id: grant_id,
+        shared_grant_id: basic.id,
+        shared: shared(),
+        settings,
+    };
+    let context = ctx(ALLOWED, U256::from(100u64));
+    let m = EtherTransfer::analyze(&context).unwrap();
+    let v = EtherTransfer::evaluate(&context, &m, &grant, &mut *conn)
+        .await
+        .unwrap();
+    assert!(
+        !v.iter()
+            .any(|e| matches!(e, EvalViolation::VolumetricLimitExceeded))
+    );
+}
+
+// ── try_find_grant ───────────────────────────────────────────────────────
+
+#[tokio::test]
+async fn try_find_grant_roundtrip() {
+    let db = db::create_test_pool().await;
+    let mut conn = db.get().await.unwrap();
+
+    let basic = insert_basic(&mut conn, false).await;
+    let settings = make_settings(vec![ALLOWED], 1_000_000);
+    EtherTransfer::create_grant(&basic, &settings, &mut *conn)
+        .await
+        .unwrap();
+
+    let found = EtherTransfer::try_find_grant(&ctx(ALLOWED, U256::from(1u64)), &mut *conn)
+        .await
+        .unwrap();
+
+    assert!(found.is_some());
+    let g = found.unwrap();
+    assert_eq!(g.settings.target, vec![ALLOWED]);
+    assert_eq!(g.settings.limit.max_volume, U256::from(1_000_000u64));
+}
+
+#[tokio::test]
+async fn try_find_grant_revoked_returns_none() {
+    let db = db::create_test_pool().await;
+    let mut conn = db.get().await.unwrap();
+
+    let basic = insert_basic(&mut conn, true).await;
+    let settings = make_settings(vec![ALLOWED], 1_000_000);
+    EtherTransfer::create_grant(&basic, &settings, &mut *conn)
+        .await
+        .unwrap();
+
+    let found = EtherTransfer::try_find_grant(&ctx(ALLOWED, U256::from(1u64)), &mut *conn)
+        .await
+        .unwrap();
+    assert!(found.is_none());
+}
+
+#[tokio::test]
+async fn try_find_grant_wrong_target_returns_none() {
+    let db = db::create_test_pool().await;
+    let mut conn = db.get().await.unwrap();
+
+    let basic = insert_basic(&mut conn, false).await;
+    let settings = make_settings(vec![ALLOWED], 1_000_000);
+    EtherTransfer::create_grant(&basic, &settings, &mut *conn)
+        .await
+        .unwrap();
+
+    let found = EtherTransfer::try_find_grant(&ctx(OTHER, U256::from(1u64)), &mut *conn)
+        .await
+        .unwrap();
+    assert!(found.is_none());
+}
+
+// ── find_all_grants ──────────────────────────────────────────────────────
+
+#[tokio::test]
+async fn find_all_grants_empty_db() {
+    let db = db::create_test_pool().await;
+    let mut conn = db.get().await.unwrap();
+    let all = EtherTransfer::find_all_grants(&mut *conn).await.unwrap();
+    assert!(all.is_empty());
+}
+
+#[tokio::test]
+async fn find_all_grants_excludes_revoked() {
+    let db = db::create_test_pool().await;
+    let mut conn = db.get().await.unwrap();
+
+    let settings = make_settings(vec![ALLOWED], 1_000_000);
+    let active = insert_basic(&mut conn, false).await;
+    EtherTransfer::create_grant(&active, &settings, &mut *conn)
+        .await
+        .unwrap();
+    let revoked = insert_basic(&mut conn, true).await;
+    EtherTransfer::create_grant(&revoked, &settings, &mut *conn)
+        .await
+        .unwrap();
+
+    let all = EtherTransfer::find_all_grants(&mut *conn).await.unwrap();
+    assert_eq!(all.len(), 1);
+    assert_eq!(all[0].settings.target, vec![ALLOWED]);
+}
+
+#[tokio::test]
+async fn find_all_grants_multiple_targets() {
+    let db = db::create_test_pool().await;
+    let mut conn = db.get().await.unwrap();
+
+    let basic = insert_basic(&mut conn, false).await;
+    let settings = make_settings(vec![ALLOWED, OTHER], 1_000_000);
+    EtherTransfer::create_grant(&basic, &settings, &mut *conn)
+        .await
+        .unwrap();
+
+    let all = EtherTransfer::find_all_grants(&mut *conn).await.unwrap();
+    assert_eq!(all.len(), 1);
+    assert_eq!(all[0].settings.target.len(), 2);
+    assert_eq!(all[0].settings.limit.max_volume, U256::from(1_000_000u64));
+}
+
+#[tokio::test]
+async fn find_all_grants_multiple_grants() {
+    let db = db::create_test_pool().await;
+    let mut conn = db.get().await.unwrap();
+
+    let basic1 = insert_basic(&mut conn, false).await;
+    EtherTransfer::create_grant(&basic1, &make_settings(vec![ALLOWED], 500), &mut *conn)
+        .await
+        .unwrap();
+    let basic2 = insert_basic(&mut conn, false).await;
+    EtherTransfer::create_grant(&basic2, &make_settings(vec![OTHER], 1_000), &mut *conn)
+        .await
+        .unwrap();
+
+    let all = EtherTransfer::find_all_grants(&mut *conn).await.unwrap();
+    assert_eq!(all.len(), 2);
+}

server/crates/arbiter-server/src/evm/policies/token_transfers/mod.rs

@@ -0,0 +1,386 @@
+use std::collections::HashMap;
+
+use alloy::{
+    primitives::{Address, U256},
+    sol_types::SolCall,
+};
+use arbiter_tokens_registry::evm::nonfungible::{self, TokenInfo};
+use chrono::{DateTime, Duration, Utc};
+use diesel::dsl::{auto_type, insert_into};
+use diesel::sqlite::Sqlite;
+use diesel::{ExpressionMethods, prelude::*};
+use diesel_async::{AsyncConnection, RunQueryDsl};
+
+use crate::db::models::{
+    EvmBasicGrant, EvmTokenTransferGrant, EvmTokenTransferVolumeLimit, NewEvmTokenTransferGrant,
+    NewEvmTokenTransferLog, NewEvmTokenTransferVolumeLimit, SqliteTimestamp,
+};
+use crate::db::schema::{
+    evm_basic_grant, evm_token_transfer_grant, evm_token_transfer_log,
+    evm_token_transfer_volume_limit,
+};
+use crate::evm::{
+    abi::IERC20::transferCall,
+    policies::{
+        Grant, Policy, SharedGrantSettings, SpecificGrant, SpecificMeaning, VolumeRateLimit,
+    },
+    utils,
+};
+
+use super::{DatabaseID, EvalContext, EvalViolation};
+
+#[auto_type]
+fn grant_join() -> _ {
+    evm_token_transfer_grant::table.inner_join(
+        evm_basic_grant::table.on(evm_token_transfer_grant::basic_grant_id.eq(evm_basic_grant::id)),
+    )
+}
+
+#[derive(Clone, Debug, PartialEq, Eq, Hash)]
+pub struct Meaning {
+    pub(crate) token: &'static TokenInfo,
+    pub(crate) to: Address,
+    pub(crate) value: U256,
+}
+impl std::fmt::Display for Meaning {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        write!(
+            f,
+            "Transfer of {} {} to {}",
+            self.value, self.token.symbol, self.to
+        )
+    }
+}
+impl From<Meaning> for SpecificMeaning {
+    fn from(val: Meaning) -> SpecificMeaning {
+        SpecificMeaning::TokenTransfer(val)
+    }
+}
+
+// A grant for token transfers, which can be scoped to specific target addresses and volume limits
+#[derive(Debug, Clone)]
+pub struct Settings {
+    pub token_contract: Address,
+    pub target: Option<Address>,
+    pub volume_limits: Vec<VolumeRateLimit>,
+}
+impl From<Settings> for SpecificGrant {
+    fn from(val: Settings) -> SpecificGrant {
+        SpecificGrant::TokenTransfer(val)
+    }
+}
+
+async fn query_relevant_past_transfers(
+    grant_id: i32,
+    longest_window: Duration,
+    db: &mut impl AsyncConnection<Backend = Sqlite>,
+) -> QueryResult<Vec<(U256, DateTime<Utc>)>> {
+    let past_logs: Vec<(Vec<u8>, SqliteTimestamp)> = evm_token_transfer_log::table
+        .filter(evm_token_transfer_log::grant_id.eq(grant_id))
+        .filter(
+            evm_token_transfer_log::created_at
+                .ge(SqliteTimestamp(chrono::Utc::now() - longest_window)),
+        )
+        .select((
+            evm_token_transfer_log::value,
+            evm_token_transfer_log::created_at,
+        ))
+        .load(db)
+        .await?;
+
+    let past_transfers: Vec<(U256, DateTime<Utc>)> = past_logs
+        .into_iter()
+        .filter_map(|(value_bytes, timestamp)| {
+            let value = utils::bytes_to_u256(&value_bytes)?;
+            Some((value, timestamp.0))
+        })
+        .collect();
+
+    Ok(past_transfers)
+}
+
+async fn check_volume_rate_limits(
+    grant: &Grant<Settings>,
+    current_transfer_value: U256,
+    db: &mut impl AsyncConnection<Backend = Sqlite>,
+) -> QueryResult<Vec<EvalViolation>> {
+    let mut violations = Vec::new();
+
+    let Some(longest_window) = grant.settings.volume_limits.iter().map(|l| l.window).max() else {
+        return Ok(violations);
+    };
+
+    let past_transfers = query_relevant_past_transfers(grant.id, longest_window, db).await?;
+
+    for limit in &grant.settings.volume_limits {
+        let window_start = chrono::Utc::now() - limit.window;
+        let prospective_cumulative_volume: U256 = past_transfers
+            .iter()
+            .filter(|(_, timestamp)| timestamp >= &window_start)
+            .fold(current_transfer_value, |acc, (value, _)| acc + *value);
+
+        if prospective_cumulative_volume > limit.max_volume {
+            violations.push(EvalViolation::VolumetricLimitExceeded);
+            break;
+        }
+    }
+
+    Ok(violations)
+}
+
+pub struct TokenTransfer;
+impl Policy for TokenTransfer {
+    type Settings = Settings;
+    type Meaning = Meaning;
+
+    fn analyze(context: &EvalContext) -> Option<Self::Meaning> {
+        let token = nonfungible::get_token(context.chain, context.to)?;
+        let decoded = transferCall::abi_decode_raw_validate(&context.calldata).ok()?;
+
+        Some(Meaning {
+            token,
+            to: decoded.to,
+            value: decoded.value,
+        })
+    }
+
+    async fn evaluate(
+        context: &EvalContext,
+        meaning: &Self::Meaning,
+        grant: &Grant<Self::Settings>,
+        db: &mut impl AsyncConnection<Backend = Sqlite>,
+    ) -> QueryResult<Vec<EvalViolation>> {
+        let mut violations = Vec::new();
+
+        // erc20 transfer shouldn't carry eth value
+        if !context.value.is_zero() {
+            violations.push(EvalViolation::InvalidTransactionType);
+            return Ok(violations);
+        }
+
+        if let Some(allowed) = grant.settings.target
+            && allowed != meaning.to
+        {
+            violations.push(EvalViolation::InvalidTarget { target: meaning.to });
+        }
+
+        let rate_violations = check_volume_rate_limits(grant, meaning.value, db).await?;
+        violations.extend(rate_violations);
+
+        Ok(violations)
+    }
+
+    async fn create_grant(
+        basic: &EvmBasicGrant,
+        grant: &Self::Settings,
+        conn: &mut impl AsyncConnection<Backend = Sqlite>,
+    ) -> QueryResult<DatabaseID> {
+        // Store the specific receiver as bytes (None means any receiver is allowed)
+        let receiver: Option<Vec<u8>> = grant.target.map(|addr| addr.to_vec());
+
+        let grant_id: i32 = insert_into(evm_token_transfer_grant::table)
+            .values(NewEvmTokenTransferGrant {
+                basic_grant_id: basic.id,
+                token_contract: grant.token_contract.to_vec(),
+                receiver,
+            })
+            .returning(evm_token_transfer_grant::id)
+            .get_result(conn)
+            .await?;
+
+        for limit in &grant.volume_limits {
+            insert_into(evm_token_transfer_volume_limit::table)
+                .values(NewEvmTokenTransferVolumeLimit {
+                    grant_id,
+                    window_secs: limit.window.num_seconds() as i32,
+                    max_volume: utils::u256_to_bytes(limit.max_volume).to_vec(),
+                })
+                .execute(conn)
+                .await?;
+        }
+
+        Ok(grant_id)
+    }
+
+    async fn try_find_grant(
+        context: &EvalContext,
+        conn: &mut impl AsyncConnection<Backend = Sqlite>,
+    ) -> QueryResult<Option<Grant<Self::Settings>>> {
+        let token_contract_bytes = context.to.to_vec();
+
+        let grant: Option<(EvmBasicGrant, EvmTokenTransferGrant)> = grant_join()
+            .filter(evm_basic_grant::revoked_at.is_null())
+            .filter(evm_basic_grant::wallet_access_id.eq(context.target.id))
+            .filter(evm_token_transfer_grant::token_contract.eq(&token_contract_bytes))
+            .select((
+                EvmBasicGrant::as_select(),
+                EvmTokenTransferGrant::as_select(),
+            ))
+            .first(conn)
+            .await
+            .optional()?;
+
+        let Some((basic_grant, token_grant)) = grant else {
+            return Ok(None);
+        };
+
+        let volume_limits_db: Vec<EvmTokenTransferVolumeLimit> =
+            evm_token_transfer_volume_limit::table
+                .filter(evm_token_transfer_volume_limit::grant_id.eq(token_grant.id))
+                .select(EvmTokenTransferVolumeLimit::as_select())
+                .load(conn)
+                .await?;
+
+        let volume_limits: Vec<VolumeRateLimit> = volume_limits_db
+            .into_iter()
+            .map(|row| {
+                Ok(VolumeRateLimit {
+                    max_volume: utils::try_bytes_to_u256(&row.max_volume).map_err(|err| {
+                        diesel::result::Error::DeserializationError(Box::new(err))
+                    })?,
+                    window: Duration::seconds(row.window_secs as i64),
+                })
+            })
+            .collect::<QueryResult<Vec<_>>>()?;
+
+        let token_contract: [u8; 20] = token_grant.token_contract.try_into().map_err(|_| {
+            diesel::result::Error::DeserializationError(
+                "Invalid token contract address length".into(),
+            )
+        })?;
+
+        let target: Option<Address> = match token_grant.receiver {
+            None => None,
+            Some(bytes) => {
+                let arr: [u8; 20] = bytes.try_into().map_err(|_| {
+                    diesel::result::Error::DeserializationError(
+                        "Invalid receiver address length".into(),
+                    )
+                })?;
+                Some(Address::from(arr))
+            }
+        };
+
+        let settings = Settings {
+            token_contract: Address::from(token_contract),
+            target,
+            volume_limits,
+        };
+
+        Ok(Some(Grant {
+            id: token_grant.id,
+            shared_grant_id: token_grant.basic_grant_id,
+            shared: SharedGrantSettings::try_from_model(basic_grant)?,
+            settings,
+        }))
+    }
+
+    async fn record_transaction(
+        context: &EvalContext,
+        meaning: &Self::Meaning,
+        log_id: i32,
+        grant: &Grant<Self::Settings>,
+        conn: &mut impl AsyncConnection<Backend = Sqlite>,
+    ) -> QueryResult<()> {
+        insert_into(evm_token_transfer_log::table)
+            .values(NewEvmTokenTransferLog {
+                grant_id: grant.id,
+                log_id,
+                chain_id: context.chain as i32,
+                token_contract: context.to.to_vec(),
+                recipient_address: meaning.to.to_vec(),
+                value: utils::u256_to_bytes(meaning.value).to_vec(),
+            })
+            .execute(conn)
+            .await?;
+
+        Ok(())
+    }
+
+    async fn find_all_grants(
+        conn: &mut impl AsyncConnection<Backend = Sqlite>,
+    ) -> QueryResult<Vec<Grant<Self::Settings>>> {
+        let grants: Vec<(EvmBasicGrant, EvmTokenTransferGrant)> = grant_join()
+            .filter(evm_basic_grant::revoked_at.is_null())
+            .select((
+                EvmBasicGrant::as_select(),
+                EvmTokenTransferGrant::as_select(),
+            ))
+            .load(conn)
+            .await?;
+
+        if grants.is_empty() {
+            return Ok(Vec::new());
+        }
+
+        let grant_ids: Vec<i32> = grants.iter().map(|(_, g)| g.id).collect();
+
+        let all_volume_limits: Vec<EvmTokenTransferVolumeLimit> =
+            evm_token_transfer_volume_limit::table
+                .filter(evm_token_transfer_volume_limit::grant_id.eq_any(&grant_ids))
+                .select(EvmTokenTransferVolumeLimit::as_select())
+                .load(conn)
+                .await?;
+
+        let mut limits_by_grant: HashMap<i32, Vec<EvmTokenTransferVolumeLimit>> = HashMap::new();
+        for limit in all_volume_limits {
+            limits_by_grant
+                .entry(limit.grant_id)
+                .or_default()
+                .push(limit);
+        }
+
+        grants
+            .into_iter()
+            .map(|(basic, specific)| {
+                let volume_limits: Vec<VolumeRateLimit> = limits_by_grant
+                    .get(&specific.id)
+                    .map(|v| v.as_slice())
+                    .unwrap_or_default()
+                    .iter()
+                    .map(|row| {
+                        Ok(VolumeRateLimit {
+                            max_volume: utils::try_bytes_to_u256(&row.max_volume).map_err(|e| {
+                                diesel::result::Error::DeserializationError(Box::new(e))
+                            })?,
+                            window: Duration::seconds(row.window_secs as i64),
+                        })
+                    })
+                    .collect::<QueryResult<Vec<_>>>()?;
+
+                let token_contract: [u8; 20] =
+                    specific.token_contract.clone().try_into().map_err(|_| {
+                        diesel::result::Error::DeserializationError(
+                            "Invalid token contract address length".into(),
+                        )
+                    })?;
+
+                let target: Option<Address> = match &specific.receiver {
+                    None => None,
+                    Some(bytes) => {
+                        let arr: [u8; 20] = bytes.clone().try_into().map_err(|_| {
+                            diesel::result::Error::DeserializationError(
+                                "Invalid receiver address length".into(),
+                            )
+                        })?;
+                        Some(Address::from(arr))
+                    }
+                };
+
+                Ok(Grant {
+                    id: specific.id,
+                    shared_grant_id: specific.basic_grant_id,
+                    shared: SharedGrantSettings::try_from_model(basic)?,
+                    settings: Settings {
+                        token_contract: Address::from(token_contract),
+                        target,
+                        volume_limits,
+                    },
+                })
+            })
+            .collect()
+    }
+}
+
+#[cfg(test)]
+mod tests;

server/crates/arbiter-server/src/evm/policies/token_transfers/tests.rs

@@ -0,0 +1,464 @@
+use alloy::primitives::{Address, Bytes, U256, address};
+use alloy::sol_types::SolCall;
+use chrono::{Duration, Utc};
+use diesel::{SelectableHelper, insert_into};
+use diesel_async::RunQueryDsl;
+
+use crate::db::{
+    self, DatabaseConnection,
+    models::{EvmBasicGrant, EvmWalletAccess, NewEvmBasicGrant, SqliteTimestamp},
+    schema::evm_basic_grant,
+};
+use crate::evm::{
+    abi::IERC20::transferCall,
+    policies::{EvalContext, EvalViolation, Grant, Policy, SharedGrantSettings, VolumeRateLimit},
+    utils,
+};
+
+use super::{Settings, TokenTransfer};
+
+// DAI on Ethereum mainnet — present in the static token registry
+const CHAIN_ID: u64 = 1;
+const DAI: Address = address!("6B175474E89094C44Da98b954EedeAC495271d0F");
+
+const WALLET_ACCESS_ID: i32 = 1;
+
+const RECIPIENT: Address = address!("aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa");
+const OTHER: Address = address!("bbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbb");
+const UNKNOWN_TOKEN: Address = address!("cccccccccccccccccccccccccccccccccccccccc");
+
+/// Encode `transfer(to, value)` raw params (no 4-byte selector).
+/// `abi_decode_raw_validate` expects exactly this format.
+fn transfer_calldata(to: Address, value: U256) -> Bytes {
+    let mut raw = Vec::new();
+    transferCall { to, value }.abi_encode_raw(&mut raw);
+    Bytes::from(raw)
+}
+
+fn ctx(to: Address, calldata: Bytes) -> EvalContext {
+    EvalContext {
+        target: EvmWalletAccess {
+            id: WALLET_ACCESS_ID,
+            wallet_id: 10,
+            client_id: 20,
+            created_at: SqliteTimestamp(Utc::now()),
+        },
+        chain: CHAIN_ID,
+        to,
+        value: U256::ZERO,
+        calldata,
+        max_fee_per_gas: 0,
+        max_priority_fee_per_gas: 0,
+    }
+}
+
+async fn insert_basic(conn: &mut DatabaseConnection, revoked: bool) -> EvmBasicGrant {
+    insert_into(evm_basic_grant::table)
+        .values(NewEvmBasicGrant {
+            wallet_access_id: WALLET_ACCESS_ID,
+            chain_id: CHAIN_ID as i32,
+            valid_from: None,
+            valid_until: None,
+            max_gas_fee_per_gas: None,
+            max_priority_fee_per_gas: None,
+            rate_limit_count: None,
+            rate_limit_window_secs: None,
+            revoked_at: revoked.then(|| SqliteTimestamp(Utc::now())),
+        })
+        .returning(EvmBasicGrant::as_select())
+        .get_result(conn)
+        .await
+        .unwrap()
+}
+
+fn make_settings(target: Option<Address>, max_volume: Option<u64>) -> Settings {
+    Settings {
+        token_contract: DAI,
+        target,
+        volume_limits: max_volume
+            .map(|v| {
+                vec![VolumeRateLimit {
+                    max_volume: U256::from(v),
+                    window: Duration::hours(1),
+                }]
+            })
+            .unwrap_or_default(),
+    }
+}
+
+fn shared() -> SharedGrantSettings {
+    SharedGrantSettings {
+        wallet_access_id: WALLET_ACCESS_ID,
+        chain: CHAIN_ID,
+        valid_from: None,
+        valid_until: None,
+        max_gas_fee_per_gas: None,
+        max_priority_fee_per_gas: None,
+        rate_limit: None,
+    }
+}
+
+// ── analyze ─────────────────────────────────────────────────────────────
+
+#[test]
+fn analyze_known_token_valid_calldata() {
+    let calldata = transfer_calldata(RECIPIENT, U256::from(100u64));
+    let m = TokenTransfer::analyze(&ctx(DAI, calldata)).unwrap();
+    assert_eq!(m.to, RECIPIENT);
+    assert_eq!(m.value, U256::from(100u64));
+}
+
+#[test]
+fn analyze_unknown_token_returns_none() {
+    let calldata = transfer_calldata(RECIPIENT, U256::from(100u64));
+    assert!(TokenTransfer::analyze(&ctx(UNKNOWN_TOKEN, calldata)).is_none());
+}
+
+#[test]
+fn analyze_invalid_calldata_returns_none() {
+    let calldata = Bytes::from(vec![0xde, 0xad, 0xbe, 0xef]);
+    assert!(TokenTransfer::analyze(&ctx(DAI, calldata)).is_none());
+}
+
+#[test]
+fn analyze_empty_calldata_returns_none() {
+    assert!(TokenTransfer::analyze(&ctx(DAI, Bytes::new())).is_none());
+}
+
+// ── evaluate ────────────────────────────────────────────────────────────
+
+#[tokio::test]
+async fn evaluate_rejects_nonzero_eth_value() {
+    let db = db::create_test_pool().await;
+    let mut conn = db.get().await.unwrap();
+
+    let grant = Grant {
+        id: 999,
+        shared_grant_id: 999,
+        shared: shared(),
+        settings: make_settings(None, None),
+    };
+    let calldata = transfer_calldata(RECIPIENT, U256::from(100u64));
+    let mut context = ctx(DAI, calldata);
+    context.value = U256::from(1u64); // ETH attached to an ERC-20 call
+
+    let m = TokenTransfer::analyze(&EvalContext {
+        value: U256::ZERO,
+        ..context.clone()
+    })
+    .unwrap();
+    let v = TokenTransfer::evaluate(&context, &m, &grant, &mut *conn)
+        .await
+        .unwrap();
+    assert!(
+        v.iter()
+            .any(|e| matches!(e, EvalViolation::InvalidTransactionType))
+    );
+}
+
+#[tokio::test]
+async fn evaluate_passes_any_recipient_when_no_restriction() {
+    let db = db::create_test_pool().await;
+    let mut conn = db.get().await.unwrap();
+
+    let grant = Grant {
+        id: 999,
+        shared_grant_id: 999,
+        shared: shared(),
+        settings: make_settings(None, None),
+    };
+    let calldata = transfer_calldata(RECIPIENT, U256::from(100u64));
+    let context = ctx(DAI, calldata);
+    let m = TokenTransfer::analyze(&context).unwrap();
+    let v = TokenTransfer::evaluate(&context, &m, &grant, &mut *conn)
+        .await
+        .unwrap();
+    assert!(v.is_empty());
+}
+
+#[tokio::test]
+async fn evaluate_passes_matching_restricted_recipient() {
+    let db = db::create_test_pool().await;
+    let mut conn = db.get().await.unwrap();
+
+    let grant = Grant {
+        id: 999,
+        shared_grant_id: 999,
+        shared: shared(),
+        settings: make_settings(Some(RECIPIENT), None),
+    };
+    let calldata = transfer_calldata(RECIPIENT, U256::from(100u64));
+    let context = ctx(DAI, calldata);
+    let m = TokenTransfer::analyze(&context).unwrap();
+    let v = TokenTransfer::evaluate(&context, &m, &grant, &mut *conn)
+        .await
+        .unwrap();
+    assert!(v.is_empty());
+}
+
+#[tokio::test]
+async fn evaluate_rejects_wrong_restricted_recipient() {
+    let db = db::create_test_pool().await;
+    let mut conn = db.get().await.unwrap();
+
+    let grant = Grant {
+        id: 999,
+        shared_grant_id: 999,
+        shared: shared(),
+        settings: make_settings(Some(RECIPIENT), None),
+    };
+    let calldata = transfer_calldata(OTHER, U256::from(100u64));
+    let context = ctx(DAI, calldata);
+    let m = TokenTransfer::analyze(&context).unwrap();
+    let v = TokenTransfer::evaluate(&context, &m, &grant, &mut *conn)
+        .await
+        .unwrap();
+    assert!(
+        v.iter()
+            .any(|e| matches!(e, EvalViolation::InvalidTarget { .. }))
+    );
+}
+
+#[tokio::test]
+async fn evaluate_passes_volume_at_exact_limit() {
+    let db = db::create_test_pool().await;
+    let mut conn = db.get().await.unwrap();
+
+    let basic = insert_basic(&mut conn, false).await;
+    let settings = make_settings(None, Some(1_000));
+    let grant_id = TokenTransfer::create_grant(&basic, &settings, &mut *conn)
+        .await
+        .unwrap();
+
+    // Record a past transfer of 900, with current transfer 100 => exactly 1000 limit
+    use crate::db::{models::NewEvmTokenTransferLog, schema::evm_token_transfer_log};
+    insert_into(evm_token_transfer_log::table)
+        .values(NewEvmTokenTransferLog {
+            grant_id,
+            log_id: 0,
+            chain_id: CHAIN_ID as i32,
+            token_contract: DAI.to_vec(),
+            recipient_address: RECIPIENT.to_vec(),
+            value: utils::u256_to_bytes(U256::from(900u64)).to_vec(),
+        })
+        .execute(&mut *conn)
+        .await
+        .unwrap();
+
+    let grant = Grant {
+        id: grant_id,
+        shared_grant_id: basic.id,
+        shared: shared(),
+        settings,
+    };
+    let calldata = transfer_calldata(RECIPIENT, U256::from(100u64));
+    let context = ctx(DAI, calldata);
+    let m = TokenTransfer::analyze(&context).unwrap();
+    let v = TokenTransfer::evaluate(&context, &m, &grant, &mut *conn)
+        .await
+        .unwrap();
+    assert!(
+        !v.iter()
+            .any(|e| matches!(e, EvalViolation::VolumetricLimitExceeded))
+    );
+}
+
+#[tokio::test]
+async fn evaluate_rejects_volume_over_limit() {
+    let db = db::create_test_pool().await;
+    let mut conn = db.get().await.unwrap();
+
+    let basic = insert_basic(&mut conn, false).await;
+    let settings = make_settings(None, Some(1_000));
+    let grant_id = TokenTransfer::create_grant(&basic, &settings, &mut *conn)
+        .await
+        .unwrap();
+
+    use crate::db::{models::NewEvmTokenTransferLog, schema::evm_token_transfer_log};
+    insert_into(evm_token_transfer_log::table)
+        .values(NewEvmTokenTransferLog {
+            grant_id,
+            log_id: 0,
+            chain_id: CHAIN_ID as i32,
+            token_contract: DAI.to_vec(),
+            recipient_address: RECIPIENT.to_vec(),
+            value: utils::u256_to_bytes(U256::from(1_000u64)).to_vec(),
+        })
+        .execute(&mut *conn)
+        .await
+        .unwrap();
+
+    let grant = Grant {
+        id: grant_id,
+        shared_grant_id: basic.id,
+        shared: shared(),
+        settings,
+    };
+    let calldata = transfer_calldata(RECIPIENT, U256::from(1u64));
+    let context = ctx(DAI, calldata);
+    let m = TokenTransfer::analyze(&context).unwrap();
+    let v = TokenTransfer::evaluate(&context, &m, &grant, &mut *conn)
+        .await
+        .unwrap();
+    assert!(
+        v.iter()
+            .any(|e| matches!(e, EvalViolation::VolumetricLimitExceeded))
+    );
+}
+
+#[tokio::test]
+async fn evaluate_no_volume_limits_always_passes() {
+    let db = db::create_test_pool().await;
+    let mut conn = db.get().await.unwrap();
+
+    let grant = Grant {
+        id: 999,
+        shared_grant_id: 999,
+        shared: shared(),
+        settings: make_settings(None, None), // no volume limits
+    };
+    let calldata = transfer_calldata(RECIPIENT, U256::from(u64::MAX));
+    let context = ctx(DAI, calldata);
+    let m = TokenTransfer::analyze(&context).unwrap();
+    let v = TokenTransfer::evaluate(&context, &m, &grant, &mut *conn)
+        .await
+        .unwrap();
+    assert!(
+        !v.iter()
+            .any(|e| matches!(e, EvalViolation::VolumetricLimitExceeded))
+    );
+}
+
+// ── try_find_grant ───────────────────────────────────────────────────────
+
+#[tokio::test]
+async fn try_find_grant_roundtrip() {
+    let db = db::create_test_pool().await;
+    let mut conn = db.get().await.unwrap();
+
+    let basic = insert_basic(&mut conn, false).await;
+    let settings = make_settings(Some(RECIPIENT), Some(5_000));
+    TokenTransfer::create_grant(&basic, &settings, &mut *conn)
+        .await
+        .unwrap();
+
+    let calldata = transfer_calldata(RECIPIENT, U256::from(100u64));
+    let found = TokenTransfer::try_find_grant(&ctx(DAI, calldata), &mut *conn)
+        .await
+        .unwrap();
+
+    assert!(found.is_some());
+    let g = found.unwrap();
+    assert_eq!(g.settings.token_contract, DAI);
+    assert_eq!(g.settings.target, Some(RECIPIENT));
+    assert_eq!(g.settings.volume_limits.len(), 1);
+    assert_eq!(g.settings.volume_limits[0].max_volume, U256::from(5_000u64));
+}
+
+#[tokio::test]
+async fn try_find_grant_revoked_returns_none() {
+    let db = db::create_test_pool().await;
+    let mut conn = db.get().await.unwrap();
+
+    let basic = insert_basic(&mut conn, true).await;
+    let settings = make_settings(None, None);
+    TokenTransfer::create_grant(&basic, &settings, &mut *conn)
+        .await
+        .unwrap();
+
+    let calldata = transfer_calldata(RECIPIENT, U256::from(1u64));
+    let found = TokenTransfer::try_find_grant(&ctx(DAI, calldata), &mut *conn)
+        .await
+        .unwrap();
+    assert!(found.is_none());
+}
+
+#[tokio::test]
+async fn try_find_grant_unknown_token_returns_none() {
+    let db = db::create_test_pool().await;
+    let mut conn = db.get().await.unwrap();
+
+    let basic = insert_basic(&mut conn, false).await;
+    let settings = make_settings(None, None);
+    TokenTransfer::create_grant(&basic, &settings, &mut *conn)
+        .await
+        .unwrap();
+
+    // Query with a different token contract
+    let calldata = transfer_calldata(RECIPIENT, U256::from(1u64));
+    let found = TokenTransfer::try_find_grant(&ctx(UNKNOWN_TOKEN, calldata), &mut *conn)
+        .await
+        .unwrap();
+    assert!(found.is_none());
+}
+
+// ── find_all_grants ──────────────────────────────────────────────────────
+
+#[tokio::test]
+async fn find_all_grants_empty_db() {
+    let db = db::create_test_pool().await;
+    let mut conn = db.get().await.unwrap();
+    let all = TokenTransfer::find_all_grants(&mut *conn).await.unwrap();
+    assert!(all.is_empty());
+}
+
+#[tokio::test]
+async fn find_all_grants_excludes_revoked() {
+    let db = db::create_test_pool().await;
+    let mut conn = db.get().await.unwrap();
+
+    let settings = make_settings(None, Some(1_000));
+    let active = insert_basic(&mut conn, false).await;
+    TokenTransfer::create_grant(&active, &settings, &mut *conn)
+        .await
+        .unwrap();
+    let revoked = insert_basic(&mut conn, true).await;
+    TokenTransfer::create_grant(&revoked, &settings, &mut *conn)
+        .await
+        .unwrap();
+
+    let all = TokenTransfer::find_all_grants(&mut *conn).await.unwrap();
+    assert_eq!(all.len(), 1);
+}
+
+#[tokio::test]
+async fn find_all_grants_loads_volume_limits() {
+    let db = db::create_test_pool().await;
+    let mut conn = db.get().await.unwrap();
+
+    let basic = insert_basic(&mut conn, false).await;
+    let settings = make_settings(None, Some(9_999));
+    TokenTransfer::create_grant(&basic, &settings, &mut *conn)
+        .await
+        .unwrap();
+
+    let all = TokenTransfer::find_all_grants(&mut *conn).await.unwrap();
+    assert_eq!(all.len(), 1);
+    assert_eq!(all[0].settings.volume_limits.len(), 1);
+    assert_eq!(
+        all[0].settings.volume_limits[0].max_volume,
+        U256::from(9_999u64)
+    );
+}
+
+#[tokio::test]
+async fn find_all_grants_multiple_grants_batch_loaded() {
+    let db = db::create_test_pool().await;
+    let mut conn = db.get().await.unwrap();
+
+    let b1 = insert_basic(&mut conn, false).await;
+    TokenTransfer::create_grant(&b1, &make_settings(None, Some(1_000)), &mut *conn)
+        .await
+        .unwrap();
+    let b2 = insert_basic(&mut conn, false).await;
+    TokenTransfer::create_grant(
+        &b2,
+        &make_settings(Some(RECIPIENT), Some(2_000)),
+        &mut *conn,
+    )
+    .await
+    .unwrap();
+
+    let all = TokenTransfer::find_all_grants(&mut *conn).await.unwrap();
+    assert_eq!(all.len(), 2);
+}

server/crates/arbiter-server/src/evm/safe_signer.rs

@@ -0,0 +1,195 @@
+use std::sync::Mutex;
+
+use crate::safe_cell::{SafeCell, SafeCellHandle as _};
+use alloy::{
+    consensus::SignableTransaction,
+    network::{TxSigner, TxSignerSync},
+    primitives::{Address, B256, ChainId, Signature},
+    signers::{Error, Result, Signer, SignerSync, utils::secret_key_to_address},
+};
+use async_trait::async_trait;
+use k256::ecdsa::{self, RecoveryId, SigningKey, signature::hazmat::PrehashSigner};
+
+/// An Ethereum signer that stores its secp256k1 secret key inside a
+/// hardware-protected [`MemSafe`] cell.
+///
+/// The underlying memory page is kept non-readable/non-writable at rest.
+/// Access is temporarily elevated only for the duration of each signing
+/// operation, then immediately revoked.
+///
+/// Because [`MemSafe::read`] requires `&mut self` while the [`Signer`] trait
+/// requires `&self`, the cell is wrapped in a [`Mutex`].
+pub struct SafeSigner {
+    key: Mutex<SafeCell<SigningKey>>,
+    address: Address,
+    chain_id: Option<ChainId>,
+}
+
+impl std::fmt::Debug for SafeSigner {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        f.debug_struct("SafeSigner")
+            .field("address", &self.address)
+            .field("chain_id", &self.chain_id)
+            .finish()
+    }
+}
+
+/// Generates a secp256k1 secret key directly inside a [`MemSafe`] cell.
+///
+/// Random bytes are written in-place into protected memory, then validated
+/// as a legal scalar on the secp256k1 curve (the scalar must be in
+/// `[1, n)` where `n` is the curve order — roughly 1-in-2^128 chance of
+/// rejection, but we retry to be correct).
+///
+/// Returns the protected key bytes and the derived Ethereum address.
+pub fn generate(rng: &mut impl rand::Rng) -> (SafeCell<[u8; 32]>, Address) {
+    loop {
+        let mut cell = SafeCell::new_inline(|w: &mut [u8; 32]| {
+            rng.fill_bytes(w);
+        });
+
+        let reader = cell.read();
+        if let Ok(sk) = SigningKey::from_slice(reader.as_ref()) {
+            let address = secret_key_to_address(&sk);
+            drop(reader);
+            return (cell, address);
+        }
+    }
+}
+
+impl SafeSigner {
+    /// Reconstructs a `SafeSigner` from key material held in a [`MemSafe`] buffer.
+    ///
+    /// The key bytes are read from protected memory, parsed as a secp256k1
+    /// scalar, and immediately moved into a new [`MemSafe`] cell. The raw
+    /// bytes are never exposed outside this function.
+    pub fn from_cell(mut cell: SafeCell<Vec<u8>>) -> Result<Self> {
+        let reader = cell.read();
+        let sk = SigningKey::from_slice(reader.as_slice()).map_err(Error::other)?;
+        drop(reader);
+        Self::new(sk)
+    }
+
+    /// Creates a new `SafeSigner` by moving the signing key into a protected
+    /// memory region.
+    pub fn new(key: SigningKey) -> Result<Self> {
+        let address = secret_key_to_address(&key);
+        let cell = SafeCell::new(key);
+        Ok(Self {
+            key: Mutex::new(cell),
+            address,
+            chain_id: None,
+        })
+    }
+
+    fn sign_hash_inner(&self, hash: &B256) -> Result<Signature> {
+        #[allow(clippy::expect_used)]
+        let mut cell = self.key.lock().expect("SafeSigner mutex poisoned");
+        let reader = cell.read();
+        let sig: (ecdsa::Signature, RecoveryId) = reader.sign_prehash(hash.as_ref())?;
+        Ok(sig.into())
+    }
+
+    fn sign_tx_inner(&self, tx: &mut dyn SignableTransaction<Signature>) -> Result<Signature> {
+        if let Some(chain_id) = self.chain_id
+            && !tx.set_chain_id_checked(chain_id)
+        {
+            return Err(Error::TransactionChainIdMismatch {
+                signer: chain_id,
+                #[allow(clippy::expect_used)]
+                tx: tx.chain_id().expect("Chain ID is guaranteed to be set"),
+            });
+        }
+        self.sign_hash_inner(&tx.signature_hash())
+            .map_err(Error::other)
+    }
+}
+
+#[async_trait]
+impl Signer for SafeSigner {
+    #[inline]
+    async fn sign_hash(&self, hash: &B256) -> Result<Signature> {
+        self.sign_hash_inner(hash)
+    }
+
+    #[inline]
+    fn address(&self) -> Address {
+        self.address
+    }
+
+    #[inline]
+    fn chain_id(&self) -> Option<ChainId> {
+        self.chain_id
+    }
+
+    #[inline]
+    fn set_chain_id(&mut self, chain_id: Option<ChainId>) {
+        self.chain_id = chain_id;
+    }
+}
+
+impl SignerSync for SafeSigner {
+    #[inline]
+    fn sign_hash_sync(&self, hash: &B256) -> Result<Signature> {
+        self.sign_hash_inner(hash)
+    }
+
+    #[inline]
+    fn chain_id_sync(&self) -> Option<ChainId> {
+        self.chain_id
+    }
+}
+
+#[async_trait]
+impl TxSigner<Signature> for SafeSigner {
+    fn address(&self) -> Address {
+        self.address
+    }
+
+    async fn sign_transaction(
+        &self,
+        tx: &mut dyn SignableTransaction<Signature>,
+    ) -> Result<Signature> {
+        self.sign_tx_inner(tx)
+    }
+}
+
+impl TxSignerSync<Signature> for SafeSigner {
+    fn address(&self) -> Address {
+        self.address
+    }
+
+    fn sign_transaction_sync(
+        &self,
+        tx: &mut dyn SignableTransaction<Signature>,
+    ) -> Result<Signature> {
+        self.sign_tx_inner(tx)
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use alloy::signers::local::PrivateKeySigner;
+
+    #[test]
+    fn sign_and_recover() {
+        let pk = PrivateKeySigner::random();
+        let key = pk.into_credential();
+        let signer = SafeSigner::new(key).unwrap();
+        let message = b"hello arbiter";
+        let sig = signer.sign_message_sync(message).unwrap();
+        let recovered = sig.recover_address_from_msg(message).unwrap();
+        assert_eq!(recovered, Signer::address(&signer));
+    }
+
+    #[test]
+    fn chain_id_roundtrip() {
+        let pk = PrivateKeySigner::random();
+        let key = pk.into_credential();
+        let mut signer = SafeSigner::new(key).unwrap();
+        assert_eq!(Signer::chain_id(&signer), None);
+        signer.set_chain_id(Some(1337));
+        assert_eq!(Signer::chain_id(&signer), Some(1337));
+    }
+}

server/crates/arbiter-server/src/evm/utils.rs

@@ -0,0 +1,26 @@
+use alloy::primitives::U256;
+
+#[derive(thiserror::Error, Debug)]
+#[error("Expected {expected} bytes but got {actual} bytes")]
+pub struct LengthError {
+    pub expected: usize,
+    pub actual: usize,
+}
+
+pub fn u256_to_bytes(value: U256) -> [u8; 32] {
+    value.to_le_bytes()
+}
+pub fn bytes_to_u256(bytes: &[u8]) -> Option<U256> {
+    let bytes: [u8; 32] = bytes.try_into().ok()?;
+    Some(U256::from_le_bytes(bytes))
+}
+
+pub fn try_bytes_to_u256(bytes: &[u8]) -> diesel::result::QueryResult<U256> {
+    let bytes: [u8; 32] = bytes.try_into().map_err(|_| {
+        diesel::result::Error::DeserializationError(Box::new(LengthError {
+            expected: 32,
+            actual: bytes.len(),
+        }))
+    })?;
+    Ok(U256::from_le_bytes(bytes))
+}

server/crates/arbiter-server/src/grpc/client.rs

@@ -0,0 +1,116 @@
+use arbiter_proto::{
+    proto::client::{
+        ClientRequest, ClientResponse, client_request::Payload as ClientRequestPayload,
+        client_response::Payload as ClientResponsePayload,
+    },
+    transport::{Receiver, Sender, grpc::GrpcBi},
+};
+use kameo::actor::{ActorRef, Spawn as _};
+use tonic::Status;
+use tracing::{info, warn};
+
+use crate::{
+    actors::client::{ClientConnection, session::ClientSession},
+    grpc::request_tracker::RequestTracker,
+};
+
+mod auth;
+mod evm;
+mod inbound;
+mod outbound;
+mod vault;
+
+async fn dispatch_loop(
+    mut bi: GrpcBi<ClientRequest, ClientResponse>,
+    actor: ActorRef<ClientSession>,
+    mut request_tracker: RequestTracker,
+) {
+    loop {
+        let Some(message) = bi.recv().await else {
+            return;
+        };
+
+        let conn = match message {
+            Ok(conn) => conn,
+            Err(err) => {
+                warn!(error = ?err, "Failed to receive client request");
+                return;
+            }
+        };
+
+        let request_id = match request_tracker.request(conn.request_id) {
+            Ok(id) => id,
+            Err(err) => {
+                let _ = bi.send(Err(err)).await;
+                return;
+            }
+        };
+
+        let Some(payload) = conn.payload else {
+            let _ = bi
+                .send(Err(Status::invalid_argument(
+                    "Missing client request payload",
+                )))
+                .await;
+            return;
+        };
+
+        match dispatch_inner(&actor, payload).await {
+            Ok(response) => {
+                if bi
+                    .send(Ok(ClientResponse {
+                        request_id: Some(request_id),
+                        payload: Some(response),
+                    }))
+                    .await
+                    .is_err()
+                {
+                    return;
+                }
+            }
+            Err(status) => {
+                let _ = bi.send(Err(status)).await;
+                return;
+            }
+        }
+    }
+}
+
+async fn dispatch_inner(
+    actor: &ActorRef<ClientSession>,
+    payload: ClientRequestPayload,
+) -> Result<ClientResponsePayload, Status> {
+    match payload {
+        ClientRequestPayload::Vault(req) => vault::dispatch(actor, req).await,
+        ClientRequestPayload::Evm(req) => evm::dispatch(actor, req).await,
+        ClientRequestPayload::Auth(..) => {
+            warn!("Unsupported post-auth client auth request");
+            Err(Status::invalid_argument("Unsupported client request"))
+        }
+    }
+}
+
+pub async fn start(mut conn: ClientConnection, mut bi: GrpcBi<ClientRequest, ClientResponse>) {
+    let mut request_tracker = RequestTracker::default();
+
+    let client_id = match auth::start(&mut conn, &mut bi, &mut request_tracker).await {
+        Ok(id) => id,
+        Err(err) => {
+            let _ = bi
+                .send(Err(Status::unauthenticated(format!(
+                    "Authentication failed: {}",
+                    err
+                ))))
+                .await;
+            warn!(error = ?err, "Client authentication failed");
+            return;
+        }
+    };
+
+    let actor = ClientSession::spawn(ClientSession::new(conn, client_id));
+    let actor_for_cleanup = actor.clone();
+
+    info!("Client authenticated successfully");
+    dispatch_loop(bi, actor, request_tracker).await;
+    actor_for_cleanup.kill();
+}

server/crates/arbiter-server/src/grpc/client/auth.rs

@@ -0,0 +1,205 @@
+use arbiter_proto::{
+    ClientMetadata,
+    proto::{
+        client::{
+            ClientRequest, ClientResponse,
+            auth::{
+                self as proto_auth, AuthChallenge as ProtoAuthChallenge,
+                AuthChallengeRequest as ProtoAuthChallengeRequest,
+                AuthChallengeSolution as ProtoAuthChallengeSolution, AuthResult as ProtoAuthResult,
+                request::Payload as AuthRequestPayload, response::Payload as AuthResponsePayload,
+            },
+            client_request::Payload as ClientRequestPayload,
+            client_response::Payload as ClientResponsePayload,
+        },
+        shared::ClientInfo as ProtoClientInfo,
+    },
+    transport::{Bi, Error as TransportError, Receiver, Sender, grpc::GrpcBi},
+};
+use async_trait::async_trait;
+use tonic::Status;
+use tracing::warn;
+
+use crate::{
+    actors::client::{self, ClientConnection, auth},
+    grpc::request_tracker::RequestTracker,
+};
+
+pub struct AuthTransportAdapter<'a> {
+    bi: &'a mut GrpcBi<ClientRequest, ClientResponse>,
+    request_tracker: &'a mut RequestTracker,
+}
+
+impl<'a> AuthTransportAdapter<'a> {
+    pub fn new(
+        bi: &'a mut GrpcBi<ClientRequest, ClientResponse>,
+        request_tracker: &'a mut RequestTracker,
+    ) -> Self {
+        Self {
+            bi,
+            request_tracker,
+        }
+    }
+
+    fn response_to_proto(response: auth::Outbound) -> AuthResponsePayload {
+        match response {
+            auth::Outbound::AuthChallenge { pubkey, nonce } => {
+                AuthResponsePayload::Challenge(ProtoAuthChallenge {
+                    pubkey: pubkey.to_bytes().to_vec(),
+                    nonce,
+                })
+            }
+            auth::Outbound::AuthSuccess => {
+                AuthResponsePayload::Result(ProtoAuthResult::Success.into())
+            }
+        }
+    }
+
+    fn error_to_proto(error: auth::Error) -> AuthResponsePayload {
+        AuthResponsePayload::Result(
+            match error {
+                auth::Error::InvalidChallengeSolution => ProtoAuthResult::InvalidSignature,
+                auth::Error::ApproveError(auth::ApproveError::Denied) => {
+                    ProtoAuthResult::ApprovalDenied
+                }
+                auth::Error::ApproveError(auth::ApproveError::Upstream(
+                    crate::actors::flow_coordinator::ApprovalError::NoUserAgentsConnected,
+                )) => ProtoAuthResult::NoUserAgentsOnline,
+                auth::Error::ApproveError(auth::ApproveError::Internal)
+                | auth::Error::DatabasePoolUnavailable
+                | auth::Error::DatabaseOperationFailed
+                | auth::Error::Transport => ProtoAuthResult::Internal,
+            }
+            .into(),
+        )
+    }
+
+    async fn send_client_response(
+        &mut self,
+        payload: AuthResponsePayload,
+    ) -> Result<(), TransportError> {
+        self.bi
+            .send(Ok(ClientResponse {
+                request_id: Some(self.request_tracker.current_request_id()),
+                payload: Some(ClientResponsePayload::Auth(proto_auth::Response {
+                    payload: Some(payload),
+                })),
+            }))
+            .await
+    }
+
+    async fn send_auth_result(&mut self, result: ProtoAuthResult) -> Result<(), TransportError> {
+        self.send_client_response(AuthResponsePayload::Result(result.into()))
+            .await
+    }
+}
+
+#[async_trait]
+impl Sender<Result<auth::Outbound, auth::Error>> for AuthTransportAdapter<'_> {
+    async fn send(
+        &mut self,
+        item: Result<auth::Outbound, auth::Error>,
+    ) -> Result<(), TransportError> {
+        let payload = match item {
+            Ok(message) => AuthTransportAdapter::response_to_proto(message),
+            Err(err) => AuthTransportAdapter::error_to_proto(err),
+        };
+
+        self.send_client_response(payload).await
+    }
+}
+
+#[async_trait]
+impl Receiver<auth::Inbound> for AuthTransportAdapter<'_> {
+    async fn recv(&mut self) -> Option<auth::Inbound> {
+        let request = match self.bi.recv().await? {
+            Ok(request) => request,
+            Err(error) => {
+                warn!(error = ?error, "grpc client recv failed; closing stream");
+                return None;
+            }
+        };
+
+        match self.request_tracker.request(request.request_id) {
+            Ok(request_id) => request_id,
+            Err(error) => {
+                let _ = self.bi.send(Err(error)).await;
+                return None;
+            }
+        };
+        let payload = request.payload?;
+        let ClientRequestPayload::Auth(auth_request) = payload else {
+            let _ = self
+                .bi
+                .send(Err(Status::invalid_argument(
+                    "Unsupported client auth request",
+                )))
+                .await;
+            return None;
+        };
+        let Some(payload) = auth_request.payload else {
+            let _ = self
+                .bi
+                .send(Err(Status::invalid_argument(
+                    "Missing client auth request payload",
+                )))
+                .await;
+            return None;
+        };
+
+        match payload {
+            AuthRequestPayload::ChallengeRequest(ProtoAuthChallengeRequest {
+                pubkey,
+                client_info,
+            }) => {
+                let Some(client_info) = client_info else {
+                    let _ = self
+                        .bi
+                        .send(Err(Status::invalid_argument("Missing client info")))
+                        .await;
+                    return None;
+                };
+                let Ok(pubkey) = <[u8; 32]>::try_from(pubkey) else {
+                    let _ = self.send_auth_result(ProtoAuthResult::InvalidKey).await;
+                    return None;
+                };
+                let Ok(pubkey) = ed25519_dalek::VerifyingKey::from_bytes(&pubkey) else {
+                    let _ = self.send_auth_result(ProtoAuthResult::InvalidKey).await;
+                    return None;
+                };
+                Some(auth::Inbound::AuthChallengeRequest {
+                    pubkey,
+                    metadata: client_metadata_from_proto(client_info),
+                })
+            }
+            AuthRequestPayload::ChallengeSolution(ProtoAuthChallengeSolution { signature }) => {
+                let Ok(signature) = ed25519_dalek::Signature::try_from(signature.as_slice()) else {
+                    let _ = self
+                        .send_auth_result(ProtoAuthResult::InvalidSignature)
+                        .await;
+                    return None;
+                };
+                Some(auth::Inbound::AuthChallengeSolution { signature })
+            }
+        }
+    }
+}
+
+impl Bi<auth::Inbound, Result<auth::Outbound, auth::Error>> for AuthTransportAdapter<'_> {}
+
+fn client_metadata_from_proto(metadata: ProtoClientInfo) -> ClientMetadata {
+    ClientMetadata {
+        name: metadata.name,
+        description: metadata.description,
+        version: metadata.version,
+    }
+}
+
+pub async fn start(
+    conn: &mut ClientConnection,
+    bi: &mut GrpcBi<ClientRequest, ClientResponse>,
+    request_tracker: &mut RequestTracker,
+) -> Result<i32, auth::Error> {
+    let mut transport = AuthTransportAdapter::new(bi, request_tracker);
+    client::auth::authenticate(conn, &mut transport).await
+}

server/crates/arbiter-server/src/grpc/client/evm.rs

@@ -0,0 +1,87 @@
+use arbiter_proto::proto::{
+    client::{
+        client_response::Payload as ClientResponsePayload,
+        evm::{
+            self as proto_evm, request::Payload as EvmRequestPayload,
+            response::Payload as EvmResponsePayload,
+        },
+    },
+    evm::{
+        EvmError as ProtoEvmError, EvmSignTransactionResponse,
+        evm_sign_transaction_response::Result as EvmSignTransactionResult,
+    },
+};
+use kameo::actor::ActorRef;
+use tonic::Status;
+use tracing::warn;
+
+use crate::{
+    actors::client::session::{ClientSession, HandleSignTransaction, SignTransactionRpcError},
+    grpc::{
+        Convert, TryConvert,
+        common::inbound::{RawEvmAddress, RawEvmTransaction},
+    },
+};
+
+fn wrap_response(payload: EvmResponsePayload) -> ClientResponsePayload {
+    ClientResponsePayload::Evm(proto_evm::Response {
+        payload: Some(payload),
+    })
+}
+
+pub(super) async fn dispatch(
+    actor: &ActorRef<ClientSession>,
+    req: proto_evm::Request,
+) -> Result<ClientResponsePayload, Status> {
+    let Some(payload) = req.payload else {
+        return Err(Status::invalid_argument(
+            "Missing client EVM request payload",
+        ));
+    };
+
+    match payload {
+        EvmRequestPayload::SignTransaction(request) => {
+            let address = RawEvmAddress(request.wallet_address).try_convert()?;
+            let transaction = RawEvmTransaction(request.rlp_transaction).try_convert()?;
+
+            let response = match actor
+                .ask(HandleSignTransaction {
+                    wallet_address: address,
+                    transaction,
+                })
+                .await
+            {
+                Ok(signature) => EvmSignTransactionResponse {
+                    result: Some(EvmSignTransactionResult::Signature(
+                        signature.as_bytes().to_vec(),
+                    )),
+                },
+                Err(kameo::error::SendError::HandlerError(SignTransactionRpcError::Vet(
+                    vet_error,
+                ))) => EvmSignTransactionResponse {
+                    result: Some(vet_error.convert()),
+                },
+                Err(kameo::error::SendError::HandlerError(SignTransactionRpcError::Internal)) => {
+                    EvmSignTransactionResponse {
+                        result: Some(EvmSignTransactionResult::Error(
+                            ProtoEvmError::Internal.into(),
+                        )),
+                    }
+                }
+                Err(err) => {
+                    warn!(error = ?err, "Failed to sign EVM transaction");
+                    EvmSignTransactionResponse {
+                        result: Some(EvmSignTransactionResult::Error(
+                            ProtoEvmError::Internal.into(),
+                        )),
+                    }
+                }
+            };
+
+            Ok(wrap_response(EvmResponsePayload::SignTransaction(response)))
+        }
+        EvmRequestPayload::AnalyzeTransaction(_) => Err(Status::unimplemented(
+            "EVM transaction analysis is not yet implemented",
+        )),
+    }
+}

server/crates/arbiter-server/src/grpc/client/inbound.rs

@@ -0,0 +1 @@
+

server/crates/arbiter-server/src/grpc/client/outbound.rs

@@ -0,0 +1 @@
+

server/crates/arbiter-server/src/grpc/client/vault.rs

@@ -0,0 +1,47 @@
+use arbiter_proto::proto::{
+    client::{
+        client_response::Payload as ClientResponsePayload,
+        vault::{
+            self as proto_vault, request::Payload as VaultRequestPayload,
+            response::Payload as VaultResponsePayload,
+        },
+    },
+    shared::VaultState as ProtoVaultState,
+};
+use kameo::{actor::ActorRef, error::SendError};
+use tonic::Status;
+use tracing::warn;
+
+use crate::actors::{
+    client::session::{ClientSession, Error, HandleQueryVaultState},
+    keyholder::KeyHolderState,
+};
+
+pub(super) async fn dispatch(
+    actor: &ActorRef<ClientSession>,
+    req: proto_vault::Request,
+) -> Result<ClientResponsePayload, Status> {
+    let Some(payload) = req.payload else {
+        return Err(Status::invalid_argument(
+            "Missing client vault request payload",
+        ));
+    };
+
+    match payload {
+        VaultRequestPayload::QueryState(_) => {
+            let state = match actor.ask(HandleQueryVaultState {}).await {
+                Ok(KeyHolderState::Unbootstrapped) => ProtoVaultState::Unbootstrapped,
+                Ok(KeyHolderState::Sealed) => ProtoVaultState::Sealed,
+                Ok(KeyHolderState::Unsealed) => ProtoVaultState::Unsealed,
+                Err(SendError::HandlerError(Error::Internal)) => ProtoVaultState::Error,
+                Err(err) => {
+                    warn!(error = ?err, "Failed to query vault state");
+                    ProtoVaultState::Error
+                }
+            };
+            Ok(ClientResponsePayload::Vault(proto_vault::Response {
+                payload: Some(VaultResponsePayload::State(state.into())),
+            }))
+        }
+    }
+}

server/crates/arbiter-server/src/grpc/common.rs

@@ -0,0 +1,2 @@
+pub mod inbound;
+pub mod outbound;

server/crates/arbiter-server/src/grpc/common/inbound.rs

@@ -0,0 +1,35 @@
+use alloy::{consensus::TxEip1559, primitives::Address, rlp::Decodable as _};
+
+use crate::grpc::TryConvert;
+
+pub struct RawEvmAddress(pub Vec<u8>);
+impl TryConvert for RawEvmAddress {
+    type Output = Address;
+
+    type Error = tonic::Status;
+
+    fn try_convert(self) -> Result<Self::Output, Self::Error> {
+        let wallet_address = match <[u8; 20]>::try_from(self.0.as_slice()) {
+            Ok(address) => Address::from(address),
+            Err(_) => {
+                return Err(tonic::Status::invalid_argument(
+                    "Invalid EVM wallet address",
+                ));
+            }
+        };
+        Ok(wallet_address)
+    }
+}
+
+pub struct RawEvmTransaction(pub Vec<u8>);
+impl TryConvert for RawEvmTransaction {
+    type Output = TxEip1559;
+
+    type Error = tonic::Status;
+
+    fn try_convert(self) -> Result<Self::Output, Self::Error> {
+        let tx = TxEip1559::decode(&mut self.0.as_slice())
+            .map_err(|_| tonic::Status::invalid_argument("Invalid EVM transaction format"))?;
+        Ok(tx)
+    }
+}

server/crates/arbiter-server/src/grpc/common/outbound.rs

@@ -0,0 +1,119 @@
+use alloy::primitives::U256;
+use arbiter_proto::proto::{
+    evm::{
+        EvmError as ProtoEvmError,
+        evm_sign_transaction_response::Result as EvmSignTransactionResult,
+    },
+    shared::evm::{
+        EvalViolation as ProtoEvalViolation, GasLimitExceededViolation, NoMatchingGrantError,
+        PolicyViolationsError, SpecificMeaning as ProtoSpecificMeaning,
+        TokenInfo as ProtoTokenInfo, TransactionEvalError as ProtoTransactionEvalError,
+        eval_violation::Kind as ProtoEvalViolationKind,
+        specific_meaning::Meaning as ProtoSpecificMeaningKind,
+        transaction_eval_error::Kind as ProtoTransactionEvalErrorKind,
+    },
+};
+
+use crate::{
+    evm::{
+        PolicyError, VetError,
+        policies::{EvalViolation, SpecificMeaning},
+    },
+    grpc::Convert,
+};
+
+fn u256_to_proto_bytes(value: U256) -> Vec<u8> {
+    value.to_be_bytes::<32>().to_vec()
+}
+
+impl Convert for SpecificMeaning {
+    type Output = ProtoSpecificMeaning;
+
+    fn convert(self) -> Self::Output {
+        let kind = match self {
+            SpecificMeaning::EtherTransfer(meaning) => ProtoSpecificMeaningKind::EtherTransfer(
+                arbiter_proto::proto::shared::evm::EtherTransferMeaning {
+                    to: meaning.to.to_vec(),
+                    value: u256_to_proto_bytes(meaning.value),
+                },
+            ),
+            SpecificMeaning::TokenTransfer(meaning) => ProtoSpecificMeaningKind::TokenTransfer(
+                arbiter_proto::proto::shared::evm::TokenTransferMeaning {
+                    token: Some(ProtoTokenInfo {
+                        symbol: meaning.token.symbol.to_string(),
+                        address: meaning.token.contract.to_vec(),
+                        chain_id: meaning.token.chain,
+                    }),
+                    to: meaning.to.to_vec(),
+                    value: u256_to_proto_bytes(meaning.value),
+                },
+            ),
+        };
+
+        ProtoSpecificMeaning {
+            meaning: Some(kind),
+        }
+    }
+}
+
+impl Convert for EvalViolation {
+    type Output = ProtoEvalViolation;
+
+    fn convert(self) -> Self::Output {
+        let kind = match self {
+            EvalViolation::InvalidTarget { target } => {
+                ProtoEvalViolationKind::InvalidTarget(target.to_vec())
+            }
+            EvalViolation::GasLimitExceeded {
+                max_gas_fee_per_gas,
+                max_priority_fee_per_gas,
+            } => ProtoEvalViolationKind::GasLimitExceeded(GasLimitExceededViolation {
+                max_gas_fee_per_gas: max_gas_fee_per_gas.map(u256_to_proto_bytes),
+                max_priority_fee_per_gas: max_priority_fee_per_gas.map(u256_to_proto_bytes),
+            }),
+            EvalViolation::RateLimitExceeded => ProtoEvalViolationKind::RateLimitExceeded(()),
+            EvalViolation::VolumetricLimitExceeded => {
+                ProtoEvalViolationKind::VolumetricLimitExceeded(())
+            }
+            EvalViolation::InvalidTime => ProtoEvalViolationKind::InvalidTime(()),
+            EvalViolation::InvalidTransactionType => {
+                ProtoEvalViolationKind::InvalidTransactionType(())
+            }
+        };
+
+        ProtoEvalViolation { kind: Some(kind) }
+    }
+}
+
+impl Convert for VetError {
+    type Output = EvmSignTransactionResult;
+
+    fn convert(self) -> Self::Output {
+        let kind = match self {
+            VetError::ContractCreationNotSupported => {
+                ProtoTransactionEvalErrorKind::ContractCreationNotSupported(())
+            }
+            VetError::UnsupportedTransactionType => {
+                ProtoTransactionEvalErrorKind::UnsupportedTransactionType(())
+            }
+            VetError::Evaluated(meaning, policy_error) => match policy_error {
+                PolicyError::NoMatchingGrant => {
+                    ProtoTransactionEvalErrorKind::NoMatchingGrant(NoMatchingGrantError {
+                        meaning: Some(meaning.convert()),
+                    })
+                }
+                PolicyError::Violations(violations) => {
+                    ProtoTransactionEvalErrorKind::PolicyViolations(PolicyViolationsError {
+                        meaning: Some(meaning.convert()),
+                        violations: violations.into_iter().map(Convert::convert).collect(),
+                    })
+                }
+                PolicyError::Database(_) => {
+                    return EvmSignTransactionResult::Error(ProtoEvmError::Internal.into());
+                }
+            },
+        };
+
+        EvmSignTransactionResult::EvalError(ProtoTransactionEvalError { kind: Some(kind) }.into())
+    }
+}

server/crates/arbiter-server/src/grpc/mod.rs

@@ -0,0 +1,78 @@
+use arbiter_proto::{
+    proto::{
+        client::{ClientRequest, ClientResponse},
+        user_agent::{UserAgentRequest, UserAgentResponse},
+    },
+    transport::grpc::GrpcBi,
+};
+use tokio_stream::wrappers::ReceiverStream;
+use tonic::{Request, Response, Status, async_trait};
+use tracing::info;
+
+use crate::{
+    actors::{client::ClientConnection, user_agent::UserAgentConnection},
+    grpc::user_agent::start,
+};
+
+mod request_tracker;
+
+pub mod client;
+pub mod user_agent;
+
+mod common;
+
+pub trait Convert {
+    type Output;
+
+    fn convert(self) -> Self::Output;
+}
+
+pub trait TryConvert {
+    type Output;
+    type Error;
+
+    fn try_convert(self) -> Result<Self::Output, Self::Error>;
+}
+
+#[async_trait]
+impl arbiter_proto::proto::arbiter_service_server::ArbiterService for super::Server {
+    type UserAgentStream = ReceiverStream<Result<UserAgentResponse, Status>>;
+    type ClientStream = ReceiverStream<Result<ClientResponse, Status>>;
+
+    #[tracing::instrument(level = "debug", skip(self))]
+    async fn client(
+        &self,
+        request: Request<tonic::Streaming<ClientRequest>>,
+    ) -> Result<Response<Self::ClientStream>, Status> {
+        let req_stream = request.into_inner();
+        let (bi, rx) = GrpcBi::from_bi_stream(req_stream);
+        let props = ClientConnection::new(self.context.db.clone(), self.context.actors.clone());
+        tokio::spawn(client::start(props, bi));
+
+        info!(event = "connection established", "grpc.client");
+
+        Ok(Response::new(rx))
+    }
+
+    #[tracing::instrument(level = "debug", skip(self))]
+    async fn user_agent(
+        &self,
+        request: Request<tonic::Streaming<UserAgentRequest>>,
+    ) -> Result<Response<Self::UserAgentStream>, Status> {
+        let req_stream = request.into_inner();
+
+        let (bi, rx) = GrpcBi::from_bi_stream(req_stream);
+
+        tokio::spawn(start(
+            UserAgentConnection {
+                db: self.context.db.clone(),
+                actors: self.context.actors.clone(),
+            },
+            bi,
+        ));
+
+        info!(event = "connection established", "grpc.user_agent");
+
+        Ok(Response::new(rx))
+    }
+}

server/crates/arbiter-server/src/grpc/request_tracker.rs

@@ -0,0 +1,26 @@
+use tonic::Status;
+
+#[derive(Default)]
+pub struct RequestTracker {
+    next_request_id: i32,
+}
+
+impl RequestTracker {
+    pub fn request(&mut self, id: i32) -> Result<i32, Status> {
+        if id < self.next_request_id {
+            return Err(Status::invalid_argument("Duplicate request id"));
+        }
+
+        self.next_request_id = id
+            .checked_add(1)
+            .ok_or_else(|| Status::invalid_argument("Invalid request id"))?;
+
+        Ok(id)
+    }
+
+    // This is used to set the response id for auth responses, which need to match the request id of the auth challenge request.
+    // -1 offset is needed because request() increments the next_request_id after returning the current request id.
+    pub fn current_request_id(&self) -> i32 {
+        self.next_request_id - 1
+    }
+}

server/crates/arbiter-server/src/grpc/user_agent.rs

@@ -0,0 +1,143 @@
+use tokio::sync::mpsc;
+
+use arbiter_proto::{
+    proto::user_agent::{
+        UserAgentRequest, UserAgentResponse,
+        user_agent_request::Payload as UserAgentRequestPayload,
+        user_agent_response::Payload as UserAgentResponsePayload,
+    },
+    transport::{Error as TransportError, Receiver, Sender, grpc::GrpcBi},
+};
+use async_trait::async_trait;
+use kameo::actor::{ActorRef, Spawn as _};
+use tonic::Status;
+use tracing::{error, info, warn};
+
+use crate::{
+    actors::user_agent::{OutOfBand, UserAgentConnection, UserAgentSession},
+    grpc::request_tracker::RequestTracker,
+};
+mod auth;
+mod evm;
+mod inbound;
+mod outbound;
+mod sdk_client;
+mod vault;
+
+pub struct OutOfBandAdapter(mpsc::Sender<OutOfBand>);
+
+#[async_trait]
+impl Sender<OutOfBand> for OutOfBandAdapter {
+    async fn send(&mut self, item: OutOfBand) -> Result<(), TransportError> {
+        self.0.send(item).await.map_err(|e| {
+            warn!(error = ?e, "Failed to send out-of-band message");
+            TransportError::ChannelClosed
+        })
+    }
+}
+
+async fn dispatch_loop(
+    mut bi: GrpcBi<UserAgentRequest, UserAgentResponse>,
+    actor: ActorRef<UserAgentSession>,
+    mut receiver: mpsc::Receiver<OutOfBand>,
+    mut request_tracker: RequestTracker,
+) {
+    loop {
+        tokio::select! {
+            oob = receiver.recv() => {
+                let Some(oob) = oob else {
+                    warn!("Out-of-band message channel closed");
+                    return;
+                };
+
+                let payload = sdk_client::out_of_band_payload(oob);
+
+                if bi.send(Ok(UserAgentResponse { id: None, payload: Some(payload) })).await.is_err() {
+                    return;
+                }
+            }
+
+            message = bi.recv() => {
+                let Some(message) = message else { return; };
+
+                let conn = match message {
+                    Ok(conn) => conn,
+                    Err(err) => {
+                        warn!(error = ?err, "Failed to receive user agent request");
+                        return;
+                    }
+                };
+
+                let request_id = match request_tracker.request(conn.id) {
+                    Ok(id) => id,
+                    Err(err) => {
+                        let _ = bi.send(Err(err)).await;
+                        return;
+                    }
+                };
+
+                let Some(payload) = conn.payload else {
+                    let _ = bi.send(Err(Status::invalid_argument("Missing user-agent request payload"))).await;
+                    return;
+                };
+
+                match dispatch_inner(&actor, payload).await {
+                    Ok(Some(response)) => {
+                        if bi.send(Ok(UserAgentResponse {
+                            id: Some(request_id),
+                            payload: Some(response),
+                        })).await.is_err() {
+                            return;
+                        }
+                    }
+                    Ok(None) => {}
+                    Err(status) => {
+                        error!(?status, "Failed to process user agent request");
+                        let _ = bi.send(Err(status)).await;
+                        return;
+                    }
+                }
+            }
+        }
+    }
+}
+
+async fn dispatch_inner(
+    actor: &ActorRef<UserAgentSession>,
+    payload: UserAgentRequestPayload,
+) -> Result<Option<UserAgentResponsePayload>, Status> {
+    match payload {
+        UserAgentRequestPayload::Vault(req) => vault::dispatch(actor, req).await,
+        UserAgentRequestPayload::Evm(req) => evm::dispatch(actor, req).await,
+        UserAgentRequestPayload::SdkClient(req) => sdk_client::dispatch(actor, req).await,
+        UserAgentRequestPayload::Auth(..) => {
+            warn!("Unsupported post-auth user agent auth request");
+            Err(Status::invalid_argument("Unsupported user-agent request"))
+        }
+    }
+}
+
+pub async fn start(
+    mut conn: UserAgentConnection,
+    mut bi: GrpcBi<UserAgentRequest, UserAgentResponse>,
+) {
+    let mut request_tracker = RequestTracker::default();
+
+    let pubkey = match auth::start(&mut conn, &mut bi, &mut request_tracker).await {
+        Ok(pubkey) => pubkey,
+        Err(e) => {
+            warn!(error = ?e, "Authentication failed");
+            return;
+        }
+    };
+
+    let (oob_sender, oob_receiver) = mpsc::channel(16);
+    let oob_adapter = OutOfBandAdapter(oob_sender);
+
+    let actor = UserAgentSession::spawn(UserAgentSession::new(conn, Box::new(oob_adapter)));
+    let actor_for_cleanup = actor.clone();
+
+    info!(?pubkey, "User authenticated successfully");
+    dispatch_loop(bi, actor, oob_receiver, request_tracker).await;
+    actor_for_cleanup.kill();
+}