fix(extensions): ignore stale MCP search responses

src/renderer/hooks/useExtensionsTabState.ts

@@ -58,6 +58,7 @@ export function useExtensionsTabState() {
 
   // ── Debounced MCP search ──
   const searchTimerRef = useRef<ReturnType<typeof setTimeout> | null>(null);
+  const mcpSearchRequestSeqRef = useRef(0);
 
   // Cleanup timer on unmount
   useEffect(() => {
@@ -65,6 +66,7 @@ export function useExtensionsTabState() {
       if (searchTimerRef.current) {
         clearTimeout(searchTimerRef.current);
       }
+      mcpSearchRequestSeqRef.current += 1;
     };
   }, []);
 
@@ -82,6 +84,7 @@ export function useExtensionsTabState() {
 
   const mcpSearch = useCallback((query: string) => {
     setMcpSearchQuery(query);
+    const requestId = ++mcpSearchRequestSeqRef.current;
 
     if (searchTimerRef.current) {
       clearTimeout(searchTimerRef.current);
@@ -98,17 +101,25 @@ export function useExtensionsTabState() {
 
     searchTimerRef.current = setTimeout(() => {
       if (!api.mcpRegistry) {
-        setMcpSearchLoading(false);
+        if (mcpSearchRequestSeqRef.current === requestId) {
+          setMcpSearchLoading(false);
+        }
         return;
       }
 
       void api.mcpRegistry.search(query).then(
         (result: McpSearchResult) => {
+          if (mcpSearchRequestSeqRef.current !== requestId) {
+            return;
+          }
           setMcpSearchResults(result.servers);
           setMcpSearchWarnings(result.warnings);
           setMcpSearchLoading(false);
         },
         () => {
+          if (mcpSearchRequestSeqRef.current !== requestId) {
+            return;
+          }
           setMcpSearchLoading(false);
           setMcpSearchWarnings(['Search failed']);
         }

test/renderer/hooks/useExtensionsTabState.test.ts

@@ -1,16 +1,21 @@
 import React, { act } from 'react';
 import { createRoot } from 'react-dom/client';
-import { afterEach, describe, expect, it, vi } from 'vitest';
+import { afterEach, beforeEach, describe, expect, it, vi } from 'vitest';
 
 import { useExtensionsTabState } from '../../../src/renderer/hooks/useExtensionsTabState';
 
+import type { McpCatalogItem } from '@shared/types/extensions';
+
 type ExtensionsTabState = ReturnType<typeof useExtensionsTabState>;
 
 let capturedState: ExtensionsTabState | null = null;
+const mcpSearchMock = vi.fn();
 
 vi.mock('@renderer/api', () => ({
   api: {
-    mcpRegistry: null,
+    mcpRegistry: {
+      search: (...args: unknown[]) => mcpSearchMock(...args),
+    },
   },
 }));
 
@@ -19,10 +24,39 @@ function Harness(): null {
   return null;
 }
 
+function createDeferred<T>() {
+  let resolve!: (value: T) => void;
+  let reject!: (reason?: unknown) => void;
+  const promise = new Promise<T>((res, rej) => {
+    resolve = res;
+    reject = rej;
+  });
+  return { promise, resolve, reject };
+}
+
+function makeMcpServer(id: string): McpCatalogItem {
+  return {
+    id,
+    name: id,
+    description: `${id} description`,
+    source: 'official',
+    installSpec: null,
+    envVars: [],
+    tools: [],
+    requiresAuth: false,
+  };
+}
+
 describe('useExtensionsTabState', () => {
+  beforeEach(() => {
+    mcpSearchMock.mockReset();
+    mcpSearchMock.mockResolvedValue({ servers: [], warnings: [] });
+  });
+
   afterEach(() => {
     capturedState = null;
     document.body.innerHTML = '';
+    vi.useRealTimers();
   });
 
   it('clears selected plugin when leaving the plugins sub-tab', async () => {
@@ -119,4 +153,97 @@ describe('useExtensionsTabState', () => {
       await Promise.resolve();
     });
   });
+
+  it('ignores stale MCP search responses that resolve out of order', async () => {
+    vi.stubGlobal('IS_REACT_ACT_ENVIRONMENT', true);
+    vi.useFakeTimers();
+    const first = createDeferred<{ servers: McpCatalogItem[]; warnings: string[] }>();
+    const second = createDeferred<{ servers: McpCatalogItem[]; warnings: string[] }>();
+
+    mcpSearchMock
+      .mockReturnValueOnce(first.promise)
+      .mockReturnValueOnce(second.promise);
+
+    const host = document.createElement('div');
+    document.body.appendChild(host);
+    const root = createRoot(host);
+
+    await act(async () => {
+      root.render(React.createElement(Harness));
+      await Promise.resolve();
+    });
+
+    await act(async () => {
+      capturedState?.mcpSearch('first');
+      await vi.advanceTimersByTimeAsync(300);
+    });
+
+    await act(async () => {
+      capturedState?.mcpSearch('second');
+      await vi.advanceTimersByTimeAsync(300);
+    });
+
+    await act(async () => {
+      second.resolve({ servers: [makeMcpServer('second-result')], warnings: ['new warning'] });
+      await Promise.resolve();
+    });
+    expect(capturedState?.mcpSearchResults.map((server) => server.id)).toEqual(['second-result']);
+    expect(capturedState?.mcpSearchWarnings).toEqual(['new warning']);
+
+    await act(async () => {
+      first.resolve({ servers: [makeMcpServer('first-result')], warnings: ['old warning'] });
+      await Promise.resolve();
+    });
+    expect(capturedState?.mcpSearchResults.map((server) => server.id)).toEqual(['second-result']);
+    expect(capturedState?.mcpSearchWarnings).toEqual(['new warning']);
+
+    await act(async () => {
+      root.unmount();
+      await Promise.resolve();
+    });
+  });
+
+  it('drops in-flight MCP search results after clearing the query', async () => {
+    vi.stubGlobal('IS_REACT_ACT_ENVIRONMENT', true);
+    vi.useFakeTimers();
+    const pending = createDeferred<{ servers: McpCatalogItem[]; warnings: string[] }>();
+    mcpSearchMock.mockReturnValueOnce(pending.promise);
+
+    const host = document.createElement('div');
+    document.body.appendChild(host);
+    const root = createRoot(host);
+
+    await act(async () => {
+      root.render(React.createElement(Harness));
+      await Promise.resolve();
+    });
+
+    await act(async () => {
+      capturedState?.mcpSearch('context7');
+      await vi.advanceTimersByTimeAsync(300);
+    });
+    expect(capturedState?.mcpSearchLoading).toBe(true);
+
+    await act(async () => {
+      capturedState?.mcpSearch('');
+      await Promise.resolve();
+    });
+    expect(capturedState?.mcpSearchQuery).toBe('');
+    expect(capturedState?.mcpSearchResults).toEqual([]);
+    expect(capturedState?.mcpSearchWarnings).toEqual([]);
+    expect(capturedState?.mcpSearchLoading).toBe(false);
+
+    await act(async () => {
+      pending.resolve({ servers: [makeMcpServer('stale-result')], warnings: ['stale warning'] });
+      await Promise.resolve();
+    });
+    expect(capturedState?.mcpSearchResults).toEqual([]);
+    expect(capturedState?.mcpSearchWarnings).toEqual([]);
+    expect(capturedState?.mcpSearchLoading).toBe(false);
+
+    await act(async () => {
+      root.unmount();
+      await Promise.resolve();
+    });
+  });
 });