fix(mcp): release optional providers when transport startup fails

Close the browser scenario owner alongside session, Android and servers when transport startup throws. Preserve cleanup failures in the existing diagnostics.

Reviewed-PR: #3230
Co-authored-by: qorvr <330186599+qorvr@users.noreply.github.com>

src/main/transport.ts

@@ -115,12 +115,17 @@ export const startMcpTransport = async (
       },
     );
   } catch (cause: unknown) {
-    const [binaryCleanup, androidCleanup, serverCleanup] =
-      await Promise.allSettled([
-        session.close(),
-        closeAndroid(),
-        closeServers(),
-      ]);
+    const [
+      binaryCleanup,
+      androidCleanup,
+      serverCleanup,
+      optionalProviderCleanup,
+    ] = await Promise.allSettled([
+      session.close(),
+      closeAndroid(),
+      closeServers(),
+      closeOptionalProviders(),
+    ]);
     serverLogger.error(
       {
         error: cause instanceof Error ? cause.message : String(cause),
@@ -136,7 +141,12 @@ export const startMcpTransport = async (
       );
       dependencies.writeStderr(`${cleanupError.message}\n`);
     }
-    for (const cleanup of [binaryCleanup, androidCleanup, serverCleanup]) {
+    for (const cleanup of [
+      binaryCleanup,
+      androidCleanup,
+      serverCleanup,
+      optionalProviderCleanup,
+    ]) {
       if (cleanup.status === "rejected") {
         const reason =
           cleanup.reason instanceof Error

tests/boundary/process/browserScenarioProbeLifecycle.test.ts

@@ -59,3 +59,44 @@ it("keeps the shared browser scenario provider open when the SDK discards its di
     await session.close();
   }
 });
+
+it("closes optional providers when MCP server startup throws", async () => {
+  const session = createTestBinarySession(() => {
+    throw new Error("Unexpected deep provider");
+  });
+  const close = vi.fn(async () => undefined);
+  const browserScenarioCapture: BrowserScenarioCapturePort = {
+    identity: () => ({
+      id: "fake-browser",
+      name: "Fake browser",
+      version: "1",
+    }),
+    captureScenario: async () => {
+      throw new Error("Unexpected scenario capture");
+    },
+    close,
+  };
+  const runtime: RuntimeDependencies = {
+    env: {},
+    serve: () => {
+      throw new Error("Server startup failed");
+    },
+    writeStderr: () => undefined,
+    setExitCode: () => undefined,
+    registerShutdown: () => () => undefined,
+  };
+  try {
+    const transport = await startMcpTransport(runtime, session, {
+      logger: silentLogger,
+      serverLogger: silentLogger,
+      environment: runtime.env,
+      delivery: new ToolResultDelivery(STDIO_DEFAULT_MAX_BUFFER_SIZE),
+      loadOptionalProviders: async () => ({ browserScenarioCapture }),
+    });
+
+    expect(transport).toEqual({ ok: false });
+    expect(close).toHaveBeenCalledTimes(1);
+  } finally {
+    await session.close();
+  }
+});