feat(local-mcp): gate cloud import and relay (#3495)

Author: richardsolomou

packages/shared/src/flags.ts

@@ -19,3 +19,5 @@ export const TASKS_PREWARM_SANDBOX_FLAG = "tasks-prewarm-sandbox";
 export const GLM_MODEL_FLAG = "posthog-code-glm-model";
 /** Spoken narration (agent speaks via the `speak` tool). Gated for a staged rollout. */
 export const SPOKEN_NARRATION_FLAG = "posthog-code-spoken-narration";
+// Gates importing and relaying local MCP servers into cloud task runs.
+export const LOCAL_MCP_IMPORT_FLAG = "posthog-code-local-mcp-import";

packages/ui/src/features/local-mcp/useLocalMcpCloudServers.test.tsx

@@ -0,0 +1,80 @@
+import type { LocalMcpCloudClassification } from "@posthog/core/local-mcp/localMcpImport";
+import { QueryClient, QueryClientProvider } from "@tanstack/react-query";
+import { renderHook, waitFor } from "@testing-library/react";
+import type { ReactNode } from "react";
+import { beforeEach, describe, expect, it, vi } from "vitest";
+
+const mocks = vi.hoisted(() => ({
+  flagEnabled: false,
+  getCloudAvailability: vi.fn(),
+}));
+
+vi.mock("@posthog/di/react", () => ({
+  useServiceOptional: () => ({
+    getCloudAvailability: mocks.getCloudAvailability,
+  }),
+}));
+
+vi.mock("../feature-flags/useFeatureFlag", () => ({
+  useFeatureFlag: () => mocks.flagEnabled,
+}));
+
+import { useLocalMcpCloudServers } from "./useLocalMcpCloudServers";
+
+function wrapper({ children }: { children: ReactNode }) {
+  const queryClient = new QueryClient({
+    defaultOptions: { queries: { retry: false } },
+  });
+  return (
+    <QueryClientProvider client={queryClient}>{children}</QueryClientProvider>
+  );
+}
+
+const server: LocalMcpCloudClassification = {
+  name: "internal-tools",
+  availability: "requires_desktop",
+  reason: "stdio_transport",
+};
+
+describe("useLocalMcpCloudServers", () => {
+  beforeEach(() => {
+    mocks.flagEnabled = false;
+    mocks.getCloudAvailability.mockReset();
+    mocks.getCloudAvailability.mockResolvedValue([server]);
+  });
+
+  it("does not inspect local MCP servers while the feature flag is disabled", () => {
+    const { result } = renderHook(() => useLocalMcpCloudServers(true), {
+      wrapper,
+    });
+
+    expect(result.current).toEqual({ servers: [], isLoading: false });
+    expect(mocks.getCloudAvailability).not.toHaveBeenCalled();
+  });
+
+  it("returns local MCP servers while the feature flag is enabled", async () => {
+    mocks.flagEnabled = true;
+
+    const { result } = renderHook(() => useLocalMcpCloudServers(true), {
+      wrapper,
+    });
+
+    await waitFor(() =>
+      expect(result.current).toEqual({ servers: [server], isLoading: false }),
+    );
+  });
+
+  it("hides cached local MCP servers when the feature flag is disabled", async () => {
+    mocks.flagEnabled = true;
+    const { result, rerender } = renderHook(
+      () => useLocalMcpCloudServers(true),
+      { wrapper },
+    );
+    await waitFor(() => expect(result.current.servers).toEqual([server]));
+
+    mocks.flagEnabled = false;
+    rerender();
+
+    expect(result.current).toEqual({ servers: [], isLoading: false });
+  });
+});

packages/ui/src/features/local-mcp/useLocalMcpCloudServers.ts

@@ -4,7 +4,9 @@ import type {
   LocalMcpImportService,
 } from "@posthog/core/local-mcp/localMcpImport";
 import { useServiceOptional } from "@posthog/di/react";
+import { LOCAL_MCP_IMPORT_FLAG } from "@posthog/shared";
 import { useQuery } from "@tanstack/react-query";
+import { useFeatureFlag } from "../feature-flags/useFeatureFlag";
 
 // Stable identity so consumers' memo deps don't churn while data is absent.
 const NO_SERVERS: LocalMcpCloudClassification[] = [];
@@ -19,21 +21,26 @@ export interface LocalMcpCloudServersResult {
 /**
  * The user's local (~/.claude.json) MCP servers classified by cloud
  * availability. Empty on hosts without a local workspace (web/mobile — the
- * service is only bound on desktop).
+ * service is only bound on desktop) and while the feature flag is off.
  */
 export function useLocalMcpCloudServers(
   enabled: boolean,
 ): LocalMcpCloudServersResult {
   const service = useServiceOptional<LocalMcpImportService>(
     LOCAL_MCP_IMPORT_SERVICE,
   );
+  const flagEnabled = useFeatureFlag(LOCAL_MCP_IMPORT_FLAG);
+  const queryEnabled = enabled && flagEnabled && !!service;
 
   const query = useQuery({
     queryKey: ["local-mcp-cloud-availability"],
     queryFn: () => (service ? service.getCloudAvailability() : NO_SERVERS),
-    enabled: enabled && !!service,
+    enabled: queryEnabled,
     staleTime: 30_000,
   });
 
-  return { servers: query.data ?? NO_SERVERS, isLoading: query.isLoading };
+  return {
+    servers: queryEnabled ? (query.data ?? NO_SERVERS) : NO_SERVERS,
+    isLoading: queryEnabled && query.isLoading,
+  };
 }