refactor(proposal): replace UpdateShamirParameters with parameterless TriggerRekey

protobufs/operator/governance.proto

@@ -2,6 +2,8 @@ syntax = "proto3";
 
 package arbiter.operator.governance;
 
+import "google/protobuf/empty.proto";
+
 message Request {
   oneof payload {
     CreateProposalRequest create = 1;
@@ -13,13 +15,13 @@ message Request {
 message CreateProposalRequest {
   oneof kind {
     ApproveSdkClientPayload         approve_sdk_client          = 1;
-    GrantWalletAccessPayload        grant_wallet_access         = 3;
-    ReplaceOperatorPayload          replace_operator            = 5;
-    UpdateShamirParametersPayload   update_shamir_parameters    = 6;
-    ApprovePersistentGrantPayload   approve_persistent_grant    = 7;
-    ApproveOneOffTransactionPayload approve_one_off_transaction = 8;
+    GrantWalletAccessPayload        grant_wallet_access         = 2;
+    ReplaceOperatorPayload          replace_operator            = 3;
+    google.protobuf.Empty           trigger_rekey               = 4;
+    ApprovePersistentGrantPayload   approve_persistent_grant    = 5;
+    ApproveOneOffTransactionPayload approve_one_off_transaction = 6;
   }
-  optional uint32 ttl_secs = 2;
+  optional uint32 ttl_secs = 7;
 }
 
 message ReplaceOperatorPayload {
@@ -27,10 +29,6 @@ message ReplaceOperatorPayload {
   bytes new_pubkey      = 2;
 }
 
-message UpdateShamirParametersPayload {
-  uint32 new_n = 1;
-}
-
 message ApproveSdkClientPayload {
   int32 client_id = 1;
 }

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

@@ -42,9 +42,7 @@ pub enum ProposalKind {
         old_operator_id: i32,
         new_pubkey: Vec<u8>,
     },
-    UpdateShamirParameters {
-        new_n: u8,
-    },
+    TriggerRekey,
     ApprovePersistentGrant {
         payload_bytes: Vec<u8>,
     },
@@ -77,7 +75,7 @@ impl ProposalKind {
                 buf.extend_from_slice(new_pubkey);
                 buf
             }
-            Self::UpdateShamirParameters { new_n } => vec![*new_n],
+            Self::TriggerRekey => vec![],
             Self::ApprovePersistentGrant { payload_bytes }
             | Self::ApproveOneOffTransaction { payload_bytes } => payload_bytes.clone(),
         }
@@ -88,7 +86,7 @@ impl ProposalKind {
     pub fn requires_full_quorum(kind: &str) -> bool {
         matches!(
             kind.parse::<ProposalKindTag>(),
-            Ok(ProposalKindTag::ReplaceOperator | ProposalKindTag::UpdateShamirParameters)
+            Ok(ProposalKindTag::ReplaceOperator | ProposalKindTag::TriggerRekey)
         )
     }
 
@@ -131,12 +129,7 @@ impl ProposalKind {
                     new_pubkey,
                 })
             }
-            ProposalKindTag::UpdateShamirParameters => {
-                let &[new_n] = payload else {
-                    return Err("invalid payload for update_shamir_parameters".to_owned());
-                };
-                Ok(Self::UpdateShamirParameters { new_n })
-            }
+            ProposalKindTag::TriggerRekey => Ok(Self::TriggerRekey),
             ProposalKindTag::ApprovePersistentGrant => Ok(Self::ApprovePersistentGrant {
                 payload_bytes: payload.to_vec(),
             }),
@@ -696,9 +689,7 @@ impl ProposalManager {
                 self.execute_replace_operator(old_operator_id, new_pubkey)
                     .await
             }
-            ProposalKind::UpdateShamirParameters { new_n } => {
-                self.execute_update_shamir_parameters(new_n).await
-            }
+            ProposalKind::TriggerRekey => self.execute_trigger_rekey().await,
             ProposalKind::ApprovePersistentGrant { payload_bytes } => {
                 self.execute_approve_persistent_grant(payload_bytes).await
             }
@@ -764,7 +755,7 @@ impl ProposalManager {
     }
 
     /// Triggers a Shamir re-key with the current operator set (§3.3).
-    async fn execute_update_shamir_parameters(&self, _new_n: u8) -> Result<(), Error> {
+    async fn execute_trigger_rekey(&self) -> Result<(), Error> {
         self.vault_coordinator
             .ask(StartRekey {})
             .await

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

@@ -62,7 +62,7 @@ enum CoordinatorState {
         ordinary_passphrases: HashMap<i32, Vec<u8>>,
         recovery_passphrases: HashMap<i32, Vec<u8>>,
     },
-    /// Shamir re-key after `replace_operator` or `update_shamir_parameters` is approved (§3.3).
+    /// Shamir re-key after `replace_operator` or `trigger_rekey` is approved (§3.3).
     /// Collects new passphrases from all current operators, then generates a fresh seal key,
     /// re-splits it, and re-encrypts the vault root key.
     Rekeying {
@@ -297,7 +297,7 @@ async fn finalize_unseal(
 }
 
 /// §3.3: Generate a fresh seal key, split across current operators, re-encrypt the vault root key.
-/// Called after `replace_operator` or `update_shamir_parameters` is approved and all contributors submit.
+/// Called after `replace_operator` or `trigger_rekey` is approved and all contributors submit.
 async fn finalize_rekey(
     db: db::DatabasePool,
     vault: ActorRef<Vault>,

server/crates/arbiter-server/src/grpc/operator/governance.rs

@@ -56,14 +56,7 @@ async fn handle_create(
             old_operator_id: p.old_operator_id,
             new_pubkey: p.new_pubkey,
         },
-        Some(ProtoKind::UpdateShamirParameters(p)) => ProposalKind::UpdateShamirParameters {
-            #[expect(
-                clippy::cast_possible_truncation,
-                clippy::as_conversions,
-                reason = "new_n is always a small operator count"
-            )]
-            new_n: p.new_n as u8,
-        },
+        Some(ProtoKind::TriggerRekey(())) => ProposalKind::TriggerRekey,
         Some(ProtoKind::ApprovePersistentGrant(p)) => {
             use prost::Message as _;
             ProposalKind::ApprovePersistentGrant {

server/crates/arbiter-server/tests/governance.rs

@@ -827,7 +827,7 @@ async fn replace_operator_updates_pubkey_and_starts_rekey() {
 }
 
 #[tokio::test]
-async fn update_shamir_parameters_reaches_quorum() {
+async fn trigger_rekey_reaches_quorum() {
     let db = db::create_test_pool().await;
     let actors = GlobalActors::spawn(db.clone()).await.unwrap();
     actors
@@ -842,7 +842,7 @@ async fn update_shamir_parameters_reaches_quorum() {
     let proposal_id = actors
         .proposal_manager
         .ask(CreateProposal {
-            kind: ProposalKind::UpdateShamirParameters { new_n: 5 },
+            kind: ProposalKind::TriggerRekey,
             initiator_id: op_id,
             ttl_secs: None,
         })