Allow prompt queueing during MCP initialization (#17395)

packages/cli/src/ui/AppContainer.tsx

@@ -106,6 +106,7 @@ import { registerCleanup, runExitCleanup } from '../utils/cleanup.js';
 import { RELAUNCH_EXIT_CODE } from '../utils/processUtils.js';
 import type { SessionInfo } from '../utils/sessionUtils.js';
 import { useMessageQueue } from './hooks/useMessageQueue.js';
+import { useMcpStatus } from './hooks/useMcpStatus.js';
 import { useApprovalModeIndicator } from './hooks/useApprovalModeIndicator.js';
 import { useSessionStats } from './contexts/SessionContext.js';
 import { useGitBranchName } from './hooks/useGitBranchName.js';
@@ -131,6 +132,7 @@ import {
   QUEUE_ERROR_DISPLAY_DURATION_MS,
 } from './constants.js';
 import { LoginWithGoogleRestartDialog } from './auth/LoginWithGoogleRestartDialog.js';
+import { isSlashCommand } from './utils/commandUtils.js';
 
 function isToolExecuting(pendingHistoryItems: HistoryItemWithoutId[]) {
   return pendingHistoryItems.some((item) => {
@@ -910,6 +912,8 @@ Logging in with Google... Restarting Gemini CLI to continue.
     isActive: !embeddedShellFocused,
   });
 
+  const { isMcpReady } = useMcpStatus(config);
+
   const {
     messageQueue,
     addMessage,
@@ -920,6 +924,7 @@ Logging in with Google... Restarting Gemini CLI to continue.
     isConfigInitialized,
     streamingState,
     submitQuery,
+    isMcpReady,
   });
 
   cancelHandlerRef.current = useCallback(
@@ -961,10 +966,31 @@ Logging in with Google... Restarting Gemini CLI to continue.
 
   const handleFinalSubmit = useCallback(
     (submittedValue: string) => {
-      addMessage(submittedValue);
+      const isSlash = isSlashCommand(submittedValue.trim());
+      const isIdle = streamingState === StreamingState.Idle;
+
+      if (isSlash || (isIdle && isMcpReady)) {
+        void submitQuery(submittedValue);
+      } else {
+        // Check messageQueue.length === 0 to only notify on the first queued item
+        if (isIdle && !isMcpReady && messageQueue.length === 0) {
+          coreEvents.emitFeedback(
+            'info',
+            'Waiting for MCP servers to initialize... Slash commands are still available and prompts will be queued.',
+          );
+        }
+        addMessage(submittedValue);
+      }
       addInput(submittedValue); // Track input for up-arrow history
     },
-    [addMessage, addInput],
+    [
+      addMessage,
+      addInput,
+      submitQuery,
+      isMcpReady,
+      streamingState,
+      messageQueue.length,
+    ],
   );
 
   const handleClearScreen = useCallback(() => {

packages/cli/src/ui/hooks/useGeminiStream.test.tsx

@@ -1962,73 +1962,6 @@ describe('useGeminiStream', () => {
     });
   });
 
-  describe('MCP Discovery State', () => {
-    it('should block non-slash command queries when discovery is in progress and servers exist', async () => {
-      const mockMcpClientManager = {
-        getDiscoveryState: vi
-          .fn()
-          .mockReturnValue(MCPDiscoveryState.IN_PROGRESS),
-        getMcpServerCount: vi.fn().mockReturnValue(1),
-      };
-      mockConfig.getMcpClientManager = () => mockMcpClientManager as any;
-
-      const { result } = renderTestHook();
-
-      await act(async () => {
-        await result.current.submitQuery('test query');
-      });
-
-      expect(coreEvents.emitFeedback).toHaveBeenCalledWith(
-        'info',
-        'Waiting for MCP servers to initialize... Slash commands are still available.',
-      );
-      expect(mockSendMessageStream).not.toHaveBeenCalled();
-    });
-
-    it('should NOT block queries when discovery is NOT_STARTED but there are no servers', async () => {
-      const mockMcpClientManager = {
-        getDiscoveryState: vi
-          .fn()
-          .mockReturnValue(MCPDiscoveryState.NOT_STARTED),
-        getMcpServerCount: vi.fn().mockReturnValue(0),
-      };
-      mockConfig.getMcpClientManager = () => mockMcpClientManager as any;
-
-      const { result } = renderTestHook();
-
-      await act(async () => {
-        await result.current.submitQuery('test query');
-      });
-
-      expect(coreEvents.emitFeedback).not.toHaveBeenCalledWith(
-        'info',
-        'Waiting for MCP servers to initialize... Slash commands are still available.',
-      );
-      expect(mockSendMessageStream).toHaveBeenCalled();
-    });
-
-    it('should NOT block slash commands even when discovery is in progress', async () => {
-      const mockMcpClientManager = {
-        getDiscoveryState: vi
-          .fn()
-          .mockReturnValue(MCPDiscoveryState.IN_PROGRESS),
-        getMcpServerCount: vi.fn().mockReturnValue(1),
-      };
-      mockConfig.getMcpClientManager = () => mockMcpClientManager as any;
-
-      const { result } = renderTestHook();
-
-      await act(async () => {
-        await result.current.submitQuery('/help');
-      });
-
-      expect(coreEvents.emitFeedback).not.toHaveBeenCalledWith(
-        'info',
-        'Waiting for MCP servers to initialize... Slash commands are still available.',
-      );
-    });
-  });
-
   describe('handleFinishedEvent', () => {
     it('should add info message for MAX_TOKENS finish reason', async () => {
       // Setup mock to return a stream with MAX_TOKENS finish reason
@@ -3270,68 +3203,4 @@ describe('useGeminiStream', () => {
       });
     });
   });
-
-  describe('MCP Server Initialization', () => {
-    it('should allow slash commands to run while MCP servers are initializing', async () => {
-      const mockMcpClientManager = {
-        getDiscoveryState: vi
-          .fn()
-          .mockReturnValue(MCPDiscoveryState.IN_PROGRESS),
-        getMcpServerCount: vi.fn().mockReturnValue(1),
-      };
-      mockConfig.getMcpClientManager = () => mockMcpClientManager as any;
-
-      const { result } = renderTestHook();
-
-      await act(async () => {
-        await result.current.submitQuery('/help');
-      });
-
-      // Slash command should be handled, and no Gemini call should be made.
-      expect(mockHandleSlashCommand).toHaveBeenCalledWith('/help');
-      expect(coreEvents.emitFeedback).not.toHaveBeenCalled();
-    });
-
-    it('should block normal prompts and provide feedback while MCP servers are initializing', async () => {
-      const mockMcpClientManager = {
-        getDiscoveryState: vi
-          .fn()
-          .mockReturnValue(MCPDiscoveryState.IN_PROGRESS),
-        getMcpServerCount: vi.fn().mockReturnValue(1),
-      };
-      mockConfig.getMcpClientManager = () => mockMcpClientManager as any;
-      const { result } = renderTestHook();
-
-      await act(async () => {
-        await result.current.submitQuery('a normal prompt');
-      });
-
-      // No slash command, no Gemini call, but feedback should be emitted.
-      expect(mockHandleSlashCommand).not.toHaveBeenCalled();
-      expect(mockSendMessageStream).not.toHaveBeenCalled();
-      expect(coreEvents.emitFeedback).toHaveBeenCalledWith(
-        'info',
-        'Waiting for MCP servers to initialize... Slash commands are still available.',
-      );
-    });
-
-    it('should allow normal prompts to run when MCP servers are finished initializing', async () => {
-      const mockMcpClientManager = {
-        getDiscoveryState: vi.fn().mockReturnValue(MCPDiscoveryState.COMPLETED),
-        getMcpServerCount: vi.fn().mockReturnValue(1),
-      };
-      mockConfig.getMcpClientManager = () => mockMcpClientManager as any;
-
-      const { result } = renderTestHook();
-
-      await act(async () => {
-        await result.current.submitQuery('a normal prompt');
-      });
-
-      // Prompt should be sent to Gemini.
-      expect(mockHandleSlashCommand).not.toHaveBeenCalled();
-      expect(mockSendMessageStream).toHaveBeenCalled();
-      expect(coreEvents.emitFeedback).not.toHaveBeenCalled();
-    });
-  });
 });

packages/cli/src/ui/hooks/useGeminiStream.ts

@@ -31,7 +31,6 @@ import {
   ValidationRequiredError,
   coreEvents,
   CoreEvent,
-  MCPDiscoveryState,
 } from '@google/gemini-cli-core';
 import type {
   Config,
@@ -991,25 +990,6 @@ export const useGeminiStream = (
         async ({ metadata: spanMetadata }) => {
           spanMetadata.input = query;
 
-          const discoveryState = config
-            .getMcpClientManager()
-            ?.getDiscoveryState();
-          const mcpServerCount =
-            config.getMcpClientManager()?.getMcpServerCount() ?? 0;
-          if (
-            !options?.isContinuation &&
-            typeof query === 'string' &&
-            !isSlashCommand(query.trim()) &&
-            mcpServerCount > 0 &&
-            discoveryState !== MCPDiscoveryState.COMPLETED
-          ) {
-            coreEvents.emitFeedback(
-              'info',
-              'Waiting for MCP servers to initialize... Slash commands are still available.',
-            );
-            return;
-          }
-
           const queryId = `${Date.now()}-${Math.random()}`;
           activeQueryIdRef.current = queryId;
           if (

packages/cli/src/ui/hooks/useMcpStatus.test.tsx

@@ -0,0 +1,97 @@
+/**
+ * @license
+ * Copyright 2025 Google LLC
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+import { describe, it, expect, vi, beforeEach, type Mock } from 'vitest';
+import { act } from 'react';
+import { render } from '../../test-utils/render.js';
+import { useMcpStatus } from './useMcpStatus.js';
+import {
+  MCPDiscoveryState,
+  type Config,
+  CoreEvent,
+  coreEvents,
+} from '@google/gemini-cli-core';
+
+describe('useMcpStatus', () => {
+  let mockConfig: Config;
+  let mockMcpClientManager: {
+    getDiscoveryState: Mock<() => MCPDiscoveryState>;
+    getMcpServerCount: Mock<() => number>;
+  };
+
+  beforeEach(() => {
+    mockMcpClientManager = {
+      getDiscoveryState: vi.fn().mockReturnValue(MCPDiscoveryState.NOT_STARTED),
+      getMcpServerCount: vi.fn().mockReturnValue(0),
+    };
+
+    mockConfig = {
+      getMcpClientManager: vi.fn().mockReturnValue(mockMcpClientManager),
+    } as unknown as Config;
+  });
+
+  const renderMcpStatusHook = (config: Config) => {
+    let hookResult: ReturnType<typeof useMcpStatus>;
+    function TestComponent({ config }: { config: Config }) {
+      hookResult = useMcpStatus(config);
+      return null;
+    }
+    render(<TestComponent config={config} />);
+    return {
+      result: {
+        get current() {
+          return hookResult;
+        },
+      },
+    };
+  };
+
+  it('should initialize with correct values (no servers)', () => {
+    const { result } = renderMcpStatusHook(mockConfig);
+
+    expect(result.current.discoveryState).toBe(MCPDiscoveryState.NOT_STARTED);
+    expect(result.current.mcpServerCount).toBe(0);
+    expect(result.current.isMcpReady).toBe(true);
+  });
+
+  it('should initialize with correct values (with servers, not started)', () => {
+    mockMcpClientManager.getMcpServerCount.mockReturnValue(1);
+    const { result } = renderMcpStatusHook(mockConfig);
+
+    expect(result.current.isMcpReady).toBe(false);
+  });
+
+  it('should not be ready while in progress', () => {
+    mockMcpClientManager.getDiscoveryState.mockReturnValue(
+      MCPDiscoveryState.IN_PROGRESS,
+    );
+    mockMcpClientManager.getMcpServerCount.mockReturnValue(1);
+    const { result } = renderMcpStatusHook(mockConfig);
+
+    expect(result.current.isMcpReady).toBe(false);
+  });
+
+  it('should update state when McpClientUpdate is emitted', () => {
+    mockMcpClientManager.getMcpServerCount.mockReturnValue(1);
+    mockMcpClientManager.getDiscoveryState.mockReturnValue(
+      MCPDiscoveryState.IN_PROGRESS,
+    );
+    const { result } = renderMcpStatusHook(mockConfig);
+
+    expect(result.current.isMcpReady).toBe(false);
+
+    mockMcpClientManager.getDiscoveryState.mockReturnValue(
+      MCPDiscoveryState.COMPLETED,
+    );
+
+    act(() => {
+      coreEvents.emit(CoreEvent.McpClientUpdate, new Map());
+    });
+
+    expect(result.current.discoveryState).toBe(MCPDiscoveryState.COMPLETED);
+    expect(result.current.isMcpReady).toBe(true);
+  });
+});

packages/cli/src/ui/hooks/useMcpStatus.ts

@@ -0,0 +1,51 @@
+/**
+ * @license
+ * Copyright 2025 Google LLC
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+import { useEffect, useState } from 'react';
+import {
+  type Config,
+  coreEvents,
+  MCPDiscoveryState,
+  CoreEvent,
+} from '@google/gemini-cli-core';
+
+export function useMcpStatus(config: Config) {
+  const [discoveryState, setDiscoveryState] = useState<MCPDiscoveryState>(
+    () =>
+      config.getMcpClientManager()?.getDiscoveryState() ??
+      MCPDiscoveryState.NOT_STARTED,
+  );
+
+  const [mcpServerCount, setMcpServerCount] = useState<number>(
+    () => config.getMcpClientManager()?.getMcpServerCount() ?? 0,
+  );
+
+  useEffect(() => {
+    const onChange = () => {
+      const manager = config.getMcpClientManager();
+      if (manager) {
+        setDiscoveryState(manager.getDiscoveryState());
+        setMcpServerCount(manager.getMcpServerCount());
+      }
+    };
+
+    coreEvents.on(CoreEvent.McpClientUpdate, onChange);
+    return () => {
+      coreEvents.off(CoreEvent.McpClientUpdate, onChange);
+    };
+  }, [config]);
+
+  // We are ready if discovery has completed, OR if it hasn't even started and there are no servers.
+  const isMcpReady =
+    discoveryState === MCPDiscoveryState.COMPLETED ||
+    (discoveryState === MCPDiscoveryState.NOT_STARTED && mcpServerCount === 0);
+
+  return {
+    discoveryState,
+    mcpServerCount,
+    isMcpReady,
+  };
+}

packages/cli/src/ui/hooks/useMessageQueue.test.tsx

@@ -28,6 +28,7 @@ describe('useMessageQueue', () => {
     isConfigInitialized: boolean;
     streamingState: StreamingState;
     submitQuery: (query: string) => void;
+    isMcpReady: boolean;
   }) => {
     let hookResult: ReturnType<typeof useMessageQueue>;
     function TestComponent(props: typeof initialProps) {
@@ -51,6 +52,7 @@ describe('useMessageQueue', () => {
       isConfigInitialized: true,
       streamingState: StreamingState.Idle,
       submitQuery: mockSubmitQuery,
+      isMcpReady: true,
     });
 
     expect(result.current.messageQueue).toEqual([]);
@@ -62,6 +64,7 @@ describe('useMessageQueue', () => {
       isConfigInitialized: true,
       streamingState: StreamingState.Responding,
       submitQuery: mockSubmitQuery,
+      isMcpReady: true,
     });
 
     act(() => {
@@ -80,6 +83,7 @@ describe('useMessageQueue', () => {
       isConfigInitialized: true,
       streamingState: StreamingState.Responding,
       submitQuery: mockSubmitQuery,
+      isMcpReady: true,
     });
 
     act(() => {
@@ -100,6 +104,7 @@ describe('useMessageQueue', () => {
       isConfigInitialized: true,
       streamingState: StreamingState.Responding,
       submitQuery: mockSubmitQuery,
+      isMcpReady: true,
     });
 
     act(() => {
@@ -120,6 +125,7 @@ describe('useMessageQueue', () => {
       isConfigInitialized: true,
       streamingState: StreamingState.Responding,
       submitQuery: mockSubmitQuery,
+      isMcpReady: true,
     });
 
     act(() => {
@@ -133,11 +139,12 @@ describe('useMessageQueue', () => {
     );
   });
 
-  it('should auto-submit queued messages when transitioning to Idle', async () => {
+  it('should auto-submit queued messages when transitioning to Idle and MCP is ready', async () => {
     const { result, rerender } = renderMessageQueueHook({
       isConfigInitialized: true,
       streamingState: StreamingState.Responding,
       submitQuery: mockSubmitQuery,
+      isMcpReady: true,
     });
 
     // Add some messages
@@ -157,11 +164,37 @@ describe('useMessageQueue', () => {
     });
   });
 
+  it('should wait for MCP readiness before auto-submitting', async () => {
+    const { result, rerender } = renderMessageQueueHook({
+      isConfigInitialized: true,
+      streamingState: StreamingState.Idle,
+      submitQuery: mockSubmitQuery,
+      isMcpReady: false,
+    });
+
+    // Add some messages while Idle but MCP not ready
+    act(() => {
+      result.current.addMessage('Delayed message');
+    });
+
+    expect(result.current.messageQueue).toEqual(['Delayed message']);
+    expect(mockSubmitQuery).not.toHaveBeenCalled();
+
+    // Transition MCP to ready
+    rerender({ isMcpReady: true });
+
+    await waitFor(() => {
+      expect(mockSubmitQuery).toHaveBeenCalledWith('Delayed message');
+      expect(result.current.messageQueue).toEqual([]);
+    });
+  });
+
   it('should not auto-submit when queue is empty', () => {
     const { rerender } = renderMessageQueueHook({
       isConfigInitialized: true,
       streamingState: StreamingState.Responding,
       submitQuery: mockSubmitQuery,
+      isMcpReady: true,
     });
 
     // Transition to Idle with empty queue
@@ -175,6 +208,7 @@ describe('useMessageQueue', () => {
       isConfigInitialized: true,
       streamingState: StreamingState.Responding,
       submitQuery: mockSubmitQuery,
+      isMcpReady: true,
     });
 
     // Add messages
@@ -194,6 +228,7 @@ describe('useMessageQueue', () => {
       isConfigInitialized: true,
       streamingState: StreamingState.Idle,
       submitQuery: mockSubmitQuery,
+      isMcpReady: true,
     });
 
     // Start responding
@@ -235,6 +270,7 @@ describe('useMessageQueue', () => {
         isConfigInitialized: true,
         streamingState: StreamingState.Responding,
         submitQuery: mockSubmitQuery,
+        isMcpReady: true,
       });
 
       // Add multiple messages
@@ -265,6 +301,7 @@ describe('useMessageQueue', () => {
         isConfigInitialized: true,
         streamingState: StreamingState.Responding,
         submitQuery: mockSubmitQuery,
+        isMcpReady: true,
       });
 
       let poppedMessages: string | undefined = 'not-undefined';
@@ -281,6 +318,7 @@ describe('useMessageQueue', () => {
         isConfigInitialized: true,
         streamingState: StreamingState.Responding,
         submitQuery: mockSubmitQuery,
+        isMcpReady: false,
       });
 
       act(() => {
@@ -301,6 +339,7 @@ describe('useMessageQueue', () => {
         isConfigInitialized: true,
         streamingState: StreamingState.Responding,
         submitQuery: mockSubmitQuery,
+        isMcpReady: false,
       });
 
       act(() => {
@@ -330,6 +369,7 @@ describe('useMessageQueue', () => {
         isConfigInitialized: true,
         streamingState: StreamingState.Responding,
         submitQuery: mockSubmitQuery,
+        isMcpReady: false,
       });
 
       // Add messages

packages/cli/src/ui/hooks/useMessageQueue.ts

@@ -11,6 +11,7 @@ export interface UseMessageQueueOptions {
   isConfigInitialized: boolean;
   streamingState: StreamingState;
   submitQuery: (query: string) => void;
+  isMcpReady: boolean;
 }
 
 export interface UseMessageQueueReturn {
@@ -30,6 +31,7 @@ export function useMessageQueue({
   isConfigInitialized,
   streamingState,
   submitQuery,
+  isMcpReady,
 }: UseMessageQueueOptions): UseMessageQueueReturn {
   const [messageQueue, setMessageQueue] = useState<string[]>([]);
 
@@ -67,6 +69,7 @@ export function useMessageQueue({
     if (
       isConfigInitialized &&
       streamingState === StreamingState.Idle &&
+      isMcpReady &&
       messageQueue.length > 0
     ) {
       // Combine all messages with double newlines for clarity
@@ -75,7 +78,13 @@ export function useMessageQueue({
       setMessageQueue([]);
       submitQuery(combinedMessage);
     }
-  }, [isConfigInitialized, streamingState, messageQueue, submitQuery]);
+  }, [
+    isConfigInitialized,
+    streamingState,
+    isMcpReady,
+    messageQueue,
+    submitQuery,
+  ]);
 
   return {
     messageQueue,

packages/core/src/tools/mcp-client-manager.ts

@@ -279,6 +279,7 @@ export class McpClientManager {
         if (currentPromise === this.discoveryPromise) {
           this.discoveryPromise = undefined;
           this.discoveryState = MCPDiscoveryState.COMPLETED;
+          this.eventEmitter?.emit('mcp-client-update', this.clients);
         }
       })
       .catch(() => {}); // Prevents unhandled rejection from the .finally branch
@@ -307,6 +308,12 @@ export class McpClientManager {
       this.cliConfig.getMcpServerCommand(),
     );
 
+    if (Object.keys(servers).length === 0) {
+      this.discoveryState = MCPDiscoveryState.COMPLETED;
+      this.eventEmitter?.emit('mcp-client-update', this.clients);
+      return;
+    }
+
     // Set state synchronously before any await yields control
     if (!this.discoveryPromise) {
       this.discoveryState = MCPDiscoveryState.IN_PROGRESS;