fix(server): snapshot queued agent updates

Capture each live agent payload before it enters the per-agent queue so shared nested state cannot change while an earlier storage read is pending.

packages/server/src/server/session.ts

@@ -901,7 +901,7 @@ export class Session {
     });
     this.agentUpdates = createAgentUpdatesService({
       emit: (message) => this.emit(message),
-      buildAgentPayload: (agent) => this.buildAgentPayload(agent),
+      enrichAgentPayload: (payload) => this.enrichAgentPayload(payload),
       buildStoredAgentPayload: (record) => this.buildStoredAgentPayload(record),
       isProviderVisibleToClient: (provider) => this.isProviderVisibleToClient(provider),
       buildProjectPlacementForWorkspaceId: (workspaceId) =>
@@ -1667,14 +1667,17 @@ export class Session {
     };
   }
 
-  private async buildAgentPayload(agent: ManagedAgent): Promise<AgentSnapshotPayload> {
-    const payload = toAgentPayload(agent);
-    const storedRecord = await this.agentStorage.get(agent.id);
+  private async enrichAgentPayload(payload: AgentSnapshotPayload): Promise<AgentSnapshotPayload> {
+    const storedRecord = await this.agentStorage.get(payload.id);
     payload.title = storedRecord?.title ?? null;
     payload.archivedAt = storedRecord?.archivedAt ?? null;
     return payload;
   }
 
+  private buildAgentPayload(agent: ManagedAgent): Promise<AgentSnapshotPayload> {
+    return this.enrichAgentPayload(toAgentPayload(agent));
+  }
+
   private buildStoredAgentPayload(
     record: StoredAgentRecord,
     registeredProviderIds = new Set(this.providerSnapshotManager.listRegisteredProviderIds()),

packages/server/src/server/session.workspaces.test.ts

@@ -757,15 +757,14 @@ test("agent updates preserve queued live transitions across stored metadata read
     lifecycle: "idle",
     updatedAt: "2026-07-31T10:00:02.000Z",
   }) as unknown as ManagedAgent;
-  const stored = {
-    ...makeStoredAgent({
-      id: "agent-coherent",
-      cwd: REPO_CWD,
-      updatedAt: "2026-07-31T10:00:03.000Z",
-    }),
-    title: "Stored title",
-    archivedAt: "2026-07-31T10:00:04.000Z",
-  };
+  running.config.model = "running-model";
+  idle.config = running.config;
+  const stored = makeStoredAgent({
+    id: "agent-coherent",
+    cwd: REPO_CWD,
+    updatedAt: "2026-07-31T10:00:03.000Z",
+  });
+  stored.title = "Stored title";
   const storageReadStarted = deferred<void>();
   const firstStorageRead = deferred<StoredAgentRecord | null>();
   const emittedAgentUpdates: Extract<
@@ -808,12 +807,14 @@ test("agent updates preserve queued live transitions across stored metadata read
       createdAt: "2026-07-31T10:00:00.000Z",
       updatedAt: "2026-07-31T10:00:00.000Z",
     });
-  activateAgentUpdatesSubscription(session, "sub-coherent", { includeArchived: true });
+  activateAgentUpdatesSubscription(session, "sub-coherent");
   if (!forwardAgentEvent) throw new Error("Agent event listener was not installed");
 
   forwardAgentEvent({ type: "agent_state", agent: running });
   await storageReadStarted.promise;
+  idle.config.model = "idle-model";
   forwardAgentEvent({ type: "agent_state", agent: idle });
+  idle.config.model = "mutated-after-queue";
   firstStorageRead.resolve(stored);
   await twoUpdatesEmitted.promise;
 
@@ -827,8 +828,8 @@ test("agent updates preserve queued live transitions across stored metadata read
           startedAt: "2026-07-31T10:00:00.500Z",
         },
         updatedAt: "2026-07-31T10:00:01.000Z",
+        model: "running-model",
         title: "Stored title",
-        archivedAt: "2026-07-31T10:00:04.000Z",
       }),
     }),
     expect.objectContaining({
@@ -837,8 +838,8 @@ test("agent updates preserve queued live transitions across stored metadata read
         status: "idle",
         activeTurn: null,
         updatedAt: "2026-07-31T10:00:02.000Z",
+        model: "idle-model",
         title: "Stored title",
-        archivedAt: "2026-07-31T10:00:04.000Z",
       }),
     }),
   ]);

packages/server/src/server/session/agent-updates/agent-updates-service.test.ts

@@ -102,7 +102,7 @@ function buildHarness() {
 
   const service = createAgentUpdatesService({
     emit: (message) => emitted.push(message),
-    buildAgentPayload: async (agent) => {
+    enrichAgentPayload: async (payload) => {
       const queuedPayload = queuedPayloadBuilds.shift();
       if (queuedPayload) {
         return queuedPayload;
@@ -110,11 +110,11 @@ function buildHarness() {
       if (buildAgentPayloadError) {
         throw buildAgentPayloadError;
       }
-      const payload = payloadById.get(agent.id);
-      if (!payload) {
-        throw new Error(`no payload registered for ${agent.id}`);
+      const registeredPayload = payloadById.get(payload.id);
+      if (!registeredPayload) {
+        throw new Error(`no payload registered for ${payload.id}`);
       }
-      return payload;
+      return registeredPayload;
     },
     buildStoredAgentPayload: (record) => {
       const payload = payloadById.get(record.id);
@@ -167,7 +167,26 @@ function buildHarness() {
         );
     },
     managed(id: string): ManagedAgent {
-      return { id } as unknown as ManagedAgent;
+      const payload = payloadById.get(id) ?? makeAgentPayload({ id });
+      return {
+        ...payload,
+        lifecycle: payload.status,
+        config: {
+          provider: payload.provider,
+          cwd: payload.cwd,
+        },
+        createdAt: new Date(payload.createdAt),
+        updatedAt: new Date(payload.updatedAt),
+        lastUserMessageAt: null,
+        pendingPermissions: new Map(),
+        attention: {
+          requiresAttention: payload.requiresAttention ?? false,
+          attentionReason: null,
+          attentionTimestamp: new Date(payload.updatedAt),
+        },
+        activeTurnId: null,
+        activeTurnStartedAt: null,
+      } as unknown as ManagedAgent;
     },
     stored(id: string): StoredAgentRecord {
       return { id } as unknown as StoredAgentRecord;

packages/server/src/server/session/agent-updates/agent-updates-service.ts

@@ -7,7 +7,7 @@ import type {
 } from "../../messages.js";
 import type { ManagedAgent } from "../../agent/agent-manager.js";
 import type { StoredAgentRecord } from "../../agent/agent-storage.js";
-import { resolveEffectiveThinkingOptionId } from "../../agent/agent-projections.js";
+import { resolveEffectiveThinkingOptionId, toAgentPayload } from "../../agent/agent-projections.js";
 
 type AgentUpdatePayload = Extract<SessionOutboundMessage, { type: "agent_update" }>["payload"];
 type AgentUpdatesFilter = NonNullable<
@@ -52,7 +52,7 @@ export interface AgentUpdatesService {
 
 export interface AgentUpdatesServiceDeps {
   emit(message: SessionOutboundMessage): void;
-  buildAgentPayload(agent: ManagedAgent): Promise<AgentSnapshotPayload>;
+  enrichAgentPayload(payload: AgentSnapshotPayload): Promise<AgentSnapshotPayload>;
   buildStoredAgentPayload(record: StoredAgentRecord): AgentSnapshotPayload;
   isProviderVisibleToClient(provider: string): boolean;
   buildProjectPlacementForWorkspaceId(workspaceId: string): Promise<ProjectPlacementPayload | null>;
@@ -258,10 +258,10 @@ export function createAgentUpdatesService(deps: AgentUpdatesServiceDeps): AgentU
     return payload;
   }
 
-  async function emitLiveAgentUpdate(agent: ManagedAgent): Promise<void> {
+  async function emitLiveAgentUpdate(payload: AgentSnapshotPayload): Promise<void> {
     try {
       const sub = subscription;
-      const payload = await deps.buildAgentPayload(agent);
+      payload = await deps.enrichAgentPayload(payload);
       if (sub) {
         const project = payload.workspaceId
           ? await deps.buildProjectPlacementForWorkspaceId(payload.workspaceId)
@@ -319,7 +319,8 @@ export function createAgentUpdatesService(deps: AgentUpdatesServiceDeps): AgentU
   }
 
   function forwardLiveAgent(agent: ManagedAgent): Promise<void> {
-    return enqueueAgentUpdate(agent.id, () => emitLiveAgentUpdate(agent));
+    const payload = toAgentPayload(agent);
+    return enqueueAgentUpdate(payload.id, () => emitLiveAgentUpdate(payload));
   }
 
   function removeAgent(agentId: string): Promise<void> {