fix(acp): resolve agent mode disconnect and improve mode awareness (#26332)

packages/cli/src/acp/acpRpcDispatcher.ts

@@ -33,6 +33,10 @@ export class GeminiAgent {
     this.sessionManager = new AcpSessionManager(settings, argv, connection);
   }
 
+  dispose(): void {
+    this.sessionManager.dispose();
+  }
+
   async initialize(
     args: acp.InitializeRequest,
   ): Promise<acp.InitializeResponse> {

packages/cli/src/acp/acpSession.test.ts

@@ -564,4 +564,26 @@ describe('Session', () => {
 
     expect(result.stopReason).toBe('max_turn_requests');
   });
+
+  it('should send sessionUpdate when approval mode changes', async () => {
+    const { coreEvents, CoreEvent, ApprovalMode } = await import(
+      '@google/gemini-cli-core'
+    );
+
+    coreEvents.emit(CoreEvent.ApprovalModeChanged, {
+      sessionId: 'session-1',
+      mode: ApprovalMode.PLAN,
+    });
+
+    expect(mockConnection.sessionUpdate).toHaveBeenCalledWith({
+      sessionId: 'session-1',
+      update: {
+        sessionUpdate: 'agent_message_chunk',
+        content: {
+          type: 'text',
+          text: `[MODE_UPDATE] ${ApprovalMode.PLAN}`,
+        },
+      },
+    });
+  });
 });

packages/cli/src/acp/acpSession.ts

@@ -8,6 +8,9 @@ import {
   type ApprovalMode,
   type ConversationRecord,
   CoreToolCallStatus,
+  coreEvents,
+  CoreEvent,
+  type ApprovalModeChangedPayload,
   logToolCall,
   convertToFunctionResponse,
   ToolConfirmationOutcome,
@@ -69,7 +72,31 @@ export class Session {
     private readonly context: AgentLoopContext,
     private readonly connection: acp.AgentSideConnection,
     private readonly settings: LoadedSettings,
-  ) {}
+  ) {
+    coreEvents.on(
+      CoreEvent.ApprovalModeChanged,
+      this.handleApprovalModeChanged,
+    );
+  }
+
+  private handleApprovalModeChanged = (payload: ApprovalModeChangedPayload) => {
+    if (payload.sessionId === this.id) {
+      void this.sendUpdate({
+        sessionUpdate: 'agent_message_chunk',
+        content: {
+          type: 'text',
+          text: `[MODE_UPDATE] ${payload.mode}`,
+        },
+      });
+    }
+  };
+
+  dispose(): void {
+    coreEvents.off(
+      CoreEvent.ApprovalModeChanged,
+      this.handleApprovalModeChanged,
+    );
+  }
 
   async cancelPendingPrompt(): Promise<void> {
     if (!this.pendingPrompt) {

packages/cli/src/acp/acpSessionManager.ts

@@ -48,6 +48,13 @@ export class AcpSessionManager {
     return this.sessions.get(sessionId);
   }
 
+  dispose(): void {
+    for (const session of this.sessions.values()) {
+      session.dispose();
+    }
+    this.sessions.clear();
+  }
+
   async newSession(
     { cwd, mcpServers }: acp.NewSessionRequest,
     authDetails: AuthDetails,
@@ -183,6 +190,12 @@ export class AcpSessionManager {
       this.connection,
       this.settings,
     );
+
+    const existingSession = this.sessions.get(sessionId);
+    if (existingSession) {
+      existingSession.dispose();
+    }
+
     this.sessions.set(sessionId, session);
 
     // Stream history back to client