fix(browser): tighten WS3 status probes

# Conflicts:
#	extensions/browser/src/browser/chrome-mcp.test.ts
#	extensions/browser/src/browser/chrome-mcp.ts
#	extensions/browser/src/browser/routes/basic.ts

extensions/browser/src/browser/chrome-mcp.test.ts

@@ -98,6 +98,7 @@ function createFakeSession(): ChromeMcpSession {
 describe("chrome MCP page parsing", () => {
   beforeEach(async () => {
     await resetChromeMcpSessionsForTest();
+    vi.useRealTimers();
   });
 
   afterEach(() => {
@@ -474,7 +475,6 @@ describe("chrome MCP page parsing", () => {
     expect(factoryCalls).toBe(2);
     expect(tabs).toHaveLength(2);
   });
-
   it("reconnects and retries list_pages once when Chrome MCP reports a stale selected page", async () => {
     let factoryCalls = 0;
     const factory: ChromeMcpSessionFactory = async () => {
@@ -613,4 +613,34 @@ describe("chrome MCP page parsing", () => {
     expect(factoryCalls).toBe(2);
     expect(tabs).toHaveLength(2);
   });
+
+  it("honors timeoutMs for ephemeral availability probes", async () => {
+    vi.useFakeTimers();
+    const closeMock = vi.fn().mockResolvedValue(undefined);
+    const factory: ChromeMcpSessionFactory = async () =>
+      ({
+        client: {
+          callTool: vi.fn(),
+          listTools: vi.fn(),
+          close: closeMock,
+          connect: vi.fn(),
+        },
+        transport: {
+          pid: 123,
+        },
+        ready: new Promise<void>(() => {}),
+      }) as unknown as ChromeMcpSession;
+    setChromeMcpSessionFactoryForTest(factory);
+
+    const promise = ensureChromeMcpAvailable("chrome-live", undefined, {
+      ephemeral: true,
+      timeoutMs: 50,
+    });
+    const expectation = expect(promise).rejects.toThrow(/timed out after 50ms/i);
+
+    await vi.advanceTimersByTimeAsync(50);
+
+    await expectation;
+    expect(closeMock).toHaveBeenCalledTimes(1);
+  });
 });

extensions/browser/src/browser/chrome-mcp.ts

@@ -463,6 +463,37 @@ async function getExistingSession(
   }
 }
 
+async function waitForChromeMcpReady(
+  session: ChromeMcpSession,
+  profileName: string,
+  timeoutMs?: number,
+): Promise<void> {
+  if (!timeoutMs || timeoutMs <= 0) {
+    await session.ready;
+    return;
+  }
+
+  let timer: ReturnType<typeof setTimeout> | undefined;
+  try {
+    await Promise.race([
+      session.ready,
+      new Promise<never>((_, reject) => {
+        timer = setTimeout(() => {
+          reject(
+            new BrowserProfileUnavailableError(
+              `Chrome MCP existing-session attach for profile "${profileName}" timed out after ${timeoutMs}ms.`,
+            ),
+          );
+        }, timeoutMs);
+      }),
+    ]);
+  } finally {
+    if (timer) {
+      clearTimeout(timer);
+    }
+  }
+}
+
 async function createEphemeralSession(
   profileName: string,
   userDataDir?: string,

extensions/browser/src/browser/routes/basic.existing-session.test.ts

@@ -63,7 +63,7 @@ describe("basic browser routes", () => {
   it("maps existing-session status failures to JSON browser errors", async () => {
     const response = await callBasicRouteWithState({
       state: createExistingSessionProfileState({
-        isHttpReachable: async () => {
+        isTransportAvailable: async () => {
           throw new BrowserProfileUnavailableError("attach failed");
         },
       }),
@@ -109,4 +109,25 @@ describe("basic browser routes", () => {
       cdpReady: true,
     });
   });
+
+  it("probes Chrome MCP transport only once for status", async () => {
+    const isHttpReachable = vi.fn(async () => true);
+    const isTransportAvailable = vi.fn(async () => true);
+
+    const response = await callBasicRouteWithState({
+      state: createExistingSessionProfileState({
+        isHttpReachable,
+        isTransportAvailable,
+      }),
+    });
+
+    expect(response.statusCode).toBe(200);
+    expect(isTransportAvailable).toHaveBeenCalledTimes(1);
+    expect(isHttpReachable).not.toHaveBeenCalled();
+    expect(response.body).toMatchObject({
+      cdpHttp: true,
+      cdpReady: true,
+      running: true,
+    });
+  });
 });

extensions/browser/src/browser/server-context.existing-session.test.ts

@@ -105,7 +105,7 @@ describe("browser server-context existing-session profile", () => {
     expect(chromeMcp.ensureChromeMcpAvailable).toHaveBeenCalledWith(
       "chrome-live",
       "/tmp/brave-profile",
-      { ephemeral: true },
+      { ephemeral: true, timeoutMs: 300 },
     );
     expect(chromeMcp.listChromeMcpTabs).toHaveBeenCalledWith("chrome-live", "/tmp/brave-profile", {
       ephemeral: true,