fix: make browser session starts recoverable

apps/extension/src/session-manager/__tests__/agent-window.test.ts

@@ -23,7 +23,7 @@ describe("chromeAgentWindowApi.ensureActiveTab", () => {
     query.mockResolvedValue([{ id: 7, active: false }]);
     update.mockResolvedValue({});
 
-    await chromeAgentWindowApi.ensureActiveTab(100, AGENT_WINDOW_HOME);
+    await chromeAgentWindowApi.ensureActiveTab(100, AGENT_WINDOW_HOME, new Set([7]));
 
     expect(query).toHaveBeenCalledWith({ windowId: 100 });
     expect(update).toHaveBeenCalledWith(7, { active: true });
@@ -34,7 +34,7 @@ describe("chromeAgentWindowApi.ensureActiveTab", () => {
     query.mockResolvedValue([]);
     create.mockResolvedValue({ id: 8 });
 
-    await chromeAgentWindowApi.ensureActiveTab(100, AGENT_WINDOW_HOME);
+    await chromeAgentWindowApi.ensureActiveTab(100, AGENT_WINDOW_HOME, new Set());
 
     expect(create).toHaveBeenCalledWith({
       windowId: 100,
@@ -43,6 +43,15 @@ describe("chromeAgentWindowApi.ensureActiveTab", () => {
     });
     expect(update).not.toHaveBeenCalled();
   });
+
+  it("creates its own home tab instead of adopting a tab opened by the user", async () => {
+    query.mockResolvedValue([{ id: 99, active: true }]);
+    create.mockResolvedValue({ id: 8 });
+    const home = await chromeAgentWindowApi.ensureActiveTab(100, AGENT_WINDOW_HOME, new Set([7]));
+    expect(home).toBe(8);
+    expect(update).not.toHaveBeenCalled();
+    expect(create).toHaveBeenCalledWith({ windowId: 100, url: AGENT_WINDOW_HOME, active: true });
+  });
 });
 
 describe("chromeAgentWindowApi.create", () => {
@@ -60,6 +69,14 @@ describe("chromeAgentWindowApi.create", () => {
     vi.unstubAllGlobals();
   });
 
+  it("returns initial tab identities from the creation result", async () => {
+    create.mockResolvedValue({ id: 100, tabs: [{ id: 7 }, { id: 8 }] });
+    expect(await chromeAgentWindowApi.create(AGENT_WINDOW_HOME)).toEqual({
+      windowId: 100,
+      initialTabIds: [7, 8],
+    });
+  });
+
   it("focuses Agent Windows by default", async () => {
     await chromeAgentWindowApi.create(AGENT_WINDOW_HOME);
 

apps/extension/src/session-manager/__tests__/disconnect-cleanup.test.ts

@@ -8,7 +8,7 @@ describe("disconnect session cleanup", () => {
     let nextWindowId = 100;
     const manager = new SessionManager({
       agentWindow: {
-        create: vi.fn(async () => nextWindowId++),
+        create: vi.fn(async () => ({ windowId: nextWindowId++, initialTabIds: [] })),
         ensureActiveTab: vi.fn(async () => 1),
         remove,
       },
@@ -40,7 +40,7 @@ describe("disconnect session cleanup", () => {
     });
     const manager = new SessionManager({
       agentWindow: {
-        create: vi.fn(async () => 100),
+        create: vi.fn(async () => ({ windowId: 100, initialTabIds: [] })),
         ensureActiveTab: vi.fn(async () => 1),
         remove: vi.fn(() => removeGate),
       },

apps/extension/src/session-manager/__tests__/event-handler.test.ts

@@ -48,7 +48,7 @@ describe("attachSessionEventHandler", () => {
     };
     const manager = new SessionManager({
       agentWindow: {
-        create: vi.fn(async () => 4242),
+        create: vi.fn(async () => ({ windowId: 4242, initialTabIds: [] })),
         remove: vi.fn(path === "window" ? emitAndFlush : async () => {}),
         ensureActiveTab: vi.fn(async () => 1),
       },
@@ -74,7 +74,7 @@ describe("attachSessionEventHandler", () => {
     const events = fakeWindowEvents();
     const manager = new SessionManager({
       agentWindow: {
-        create: vi.fn(async () => 4242),
+        create: vi.fn(async () => ({ windowId: 4242, initialTabIds: [] })),
         remove: vi.fn(async () => {
           throw new Error("close failed");
         }),
@@ -100,7 +100,7 @@ describe("attachSessionEventHandler", () => {
   it("drops the local session and emits session.window_closed when the agent window closes", async () => {
     const manager = new SessionManager({
       agentWindow: {
-        create: vi.fn(async () => 4242),
+        create: vi.fn(async () => ({ windowId: 4242, initialTabIds: [] })),
         remove: vi.fn(async () => {}),
         ensureActiveTab: vi.fn(async () => 1),
       },
@@ -134,7 +134,7 @@ describe("attachSessionEventHandler", () => {
   it("reports borrowed tabs as return failures when the Agent Window was already closed", async () => {
     const manager = new SessionManager({
       agentWindow: {
-        create: vi.fn(async () => 4242),
+        create: vi.fn(async () => ({ windowId: 4242, initialTabIds: [] })),
         remove: vi.fn(async () => {}),
         ensureActiveTab: vi.fn(async () => 1),
       },
@@ -175,7 +175,7 @@ describe("attachSessionEventHandler", () => {
   it("ignores non-agent windows", async () => {
     const manager = new SessionManager({
       agentWindow: {
-        create: vi.fn(async () => 1),
+        create: vi.fn(async () => ({ windowId: 1, initialTabIds: [] })),
         remove: vi.fn(),
         ensureActiveTab: vi.fn(async () => 1),
       },
@@ -191,7 +191,7 @@ describe("attachSessionEventHandler", () => {
   it("dispose() removes the listener", () => {
     const manager = new SessionManager({
       agentWindow: {
-        create: vi.fn(async () => 1),
+        create: vi.fn(async () => ({ windowId: 1, initialTabIds: [] })),
         remove: vi.fn(),
         ensureActiveTab: vi.fn(async () => 1),
       },

apps/extension/src/session-manager/__tests__/manager.test.ts

@@ -1,5 +1,9 @@
 import { describe, expect, it, vi } from "vitest";
-import type { AgentWindowApi, AgentWindowCreateOptions } from "../agent-window";
+import type {
+  AgentWindowApi,
+  AgentWindowCreateOptions,
+  AgentWindowCreation,
+} from "../agent-window";
 import { isAgentControlledTab, SessionManager } from "../manager";
 
 function fakeAgentWindow(): AgentWindowApi & {
@@ -10,7 +14,7 @@ function fakeAgentWindow(): AgentWindowApi & {
   let nextId = 100;
   const createMock = vi.fn(async (_url: string, _opts?: AgentWindowCreateOptions) => {
     const id = nextId++;
-    return id;
+    return { windowId: id, initialTabIds: [] };
   });
   const removeMock = vi.fn(async (_id: number) => {});
   const ensureActiveTabMock = vi.fn(async (_windowId: number, _url: string) => 0);
@@ -32,7 +36,7 @@ describe("SessionManager", () => {
     expect(aw.createMock).toHaveBeenCalledOnce();
     expect(aw.createMock).toHaveBeenCalledWith("about:blank", {});
     expect(aw.ensureActiveTabMock).toHaveBeenCalledOnce();
-    expect(aw.ensureActiveTabMock).toHaveBeenCalledWith(100, "about:blank");
+    expect(aw.ensureActiveTabMock).toHaveBeenCalledWith(100, "about:blank", expect.any(Set));
     expect(ctx.sessionId).toBe("aa11");
     expect(ctx.agentWindowId).toBe(100);
     expect(ctx.createdAtMs).toBe(1700000000000);
@@ -77,10 +81,10 @@ describe("SessionManager", () => {
 
   it("removes a newly created Agent Window when startup is aborted", async () => {
     const aw = fakeAgentWindow();
-    let resolveCreate: (windowId: number) => void = () => {};
+    let resolveCreate: (result: AgentWindowCreation) => void = () => {};
     aw.createMock.mockImplementationOnce(
       () =>
-        new Promise<number>((resolve) => {
+        new Promise<AgentWindowCreation>((resolve) => {
           resolveCreate = resolve;
         }),
     );
@@ -89,7 +93,7 @@ describe("SessionManager", () => {
     const pending = sm.start("aa11", { signal: controller.signal });
 
     controller.abort();
-    resolveCreate(777);
+    resolveCreate({ windowId: 777, initialTabIds: [7] });
 
     await expect(pending).rejects.toMatchObject({ name: "AbortError" });
     expect(aw.removeMock).toHaveBeenCalledWith(777);
@@ -107,7 +111,7 @@ describe("SessionManager", () => {
     expect(sm.has("aa11")).toBe(false);
   });
 
-  it("surfaces the orphan Agent Window id when startup cleanup fails", async () => {
+  it("retains a failed startup window so stop can retry cleanup", async () => {
     const aw = fakeAgentWindow();
     aw.ensureActiveTabMock.mockRejectedValueOnce(new Error("tab setup failed"));
     aw.removeMock.mockRejectedValueOnce(new Error("window removal denied"));
@@ -118,7 +122,12 @@ describe("SessionManager", () => {
       windowId: 100,
       message: expect.stringMatching(/cleanup of Agent Window 100 failed.*window removal denied/),
     });
+    expect(sm.has("aa11")).toBe(true);
+    expect(sm.findByWindowId(100)?.sessionId).toBe("aa11");
+    await sm.stop("aa11");
+    expect(aw.removeMock).toHaveBeenCalledTimes(2);
     expect(sm.has("aa11")).toBe(false);
+    expect(sm.findByWindowId(100)).toBeNull();
   });
 
   it("stop() closes the Agent Window and forgets the session", async () => {

apps/extension/src/session-manager/agent-window.ts

@@ -8,7 +8,7 @@
  */
 
 export interface AgentWindowApi {
-  create(url: string, opts?: AgentWindowCreateOptions): Promise<number>;
+  create(url: string, opts?: AgentWindowCreateOptions): Promise<AgentWindowCreation>;
   remove(windowId: number): Promise<void>;
   /**
    * Guarantee the Agent Window has an active, CDP-navigable tab.
@@ -18,7 +18,13 @@ export interface AgentWindowApi {
    * Resolves with the id of the activated (or newly created) tab, so callers
    * can track the session's home tab without re-querying Chrome.
    */
-  ensureActiveTab(windowId: number, url: string): Promise<number>;
+  ensureActiveTab(windowId: number, url: string, ownedTabIds: ReadonlySet<number>): Promise<number>;
+}
+
+/** Resource identities captured from the creation result, before initialization. */
+export interface AgentWindowCreation {
+  windowId: number;
+  initialTabIds: number[];
 }
 
 /** Creation hints for a new Agent Window. */
@@ -33,7 +39,7 @@ export interface AgentWindowCreateOptions {
 export const AGENT_WINDOW_HOME = "about:blank";
 
 export const chromeAgentWindowApi: AgentWindowApi = {
-  async create(url: string, opts: AgentWindowCreateOptions = {}): Promise<number> {
+  async create(url: string, opts: AgentWindowCreateOptions = {}): Promise<AgentWindowCreation> {
     const win = await chrome.windows.create({
       type: "normal",
       focused: opts.focused ?? true,
@@ -43,7 +49,12 @@ export const chromeAgentWindowApi: AgentWindowApi = {
     if (typeof win?.id !== "number") {
       throw new Error("[bh] chrome.windows.create returned no window id");
     }
-    return win.id;
+    return {
+      windowId: win.id,
+      initialTabIds: (win.tabs ?? []).flatMap((tab) =>
+        typeof tab.id === "number" ? [tab.id] : [],
+      ),
+    };
   },
   async remove(windowId: number): Promise<void> {
     // Callers decide whether a missing/failed removal is benign. In
@@ -52,9 +63,15 @@ export const chromeAgentWindowApi: AgentWindowApi = {
     // cancellation success while the Agent Window remains open.
     await chrome.windows.remove(windowId);
   },
-  async ensureActiveTab(windowId: number, url: string): Promise<number> {
+  async ensureActiveTab(
+    windowId: number,
+    url: string,
+    ownedTabIds: ReadonlySet<number>,
+  ): Promise<number> {
     const tabs = await chrome.tabs.query({ windowId });
-    const first = tabs.find((t) => typeof t.id === "number");
+    // A user may have opened a tab while window initialization was pending.
+    // Reuse only a tab whose identity came from our creation result.
+    const first = tabs.find((t) => t.id !== undefined && ownedTabIds.has(t.id));
     if (first?.id !== undefined) {
       if (!first.active) {
         await chrome.tabs.update(first.id, { active: true });

apps/extension/src/session-manager/manager.ts

@@ -226,11 +226,19 @@ export class SessionManager {
     throwIfSessionStartAborted(opts.signal);
 
     let windowId: number | null = null;
+    const agentCreatedTabs = new Set<number>();
     try {
       const { signal: _signal, ...createOptions } = opts;
-      windowId = await this.agentWindow.create(AGENT_WINDOW_HOME, createOptions);
+      const created = await this.agentWindow.create(AGENT_WINDOW_HOME, createOptions);
+      windowId = created.windowId;
+      for (const tabId of created.initialTabIds) agentCreatedTabs.add(tabId);
       throwIfSessionStartAborted(opts.signal);
-      const homeTabId = await this.agentWindow.ensureActiveTab(windowId, AGENT_WINDOW_HOME);
+      const homeTabId = await this.agentWindow.ensureActiveTab(
+        windowId,
+        AGENT_WINDOW_HOME,
+        agentCreatedTabs,
+      );
+      agentCreatedTabs.add(homeTabId);
       throwIfSessionStartAborted(opts.signal);
 
       const ctx: SessionContext = {
@@ -239,10 +247,10 @@ export class SessionManager {
         agentWindowId: windowId,
         refStore: new RefStore(),
         borrowedTabs: new Map(),
-        // The home tab is the session's first explicit claim. Every other
-        // tab remains free until `tab_create` or `tab_borrow` identifies it
-        // by its concrete Chrome tab id.
-        agentCreatedTabs: new Set([homeTabId]),
+        // Capture ownership at creation, before initialization can fail.
+        // Later tabs remain free until `tab_create` or `tab_borrow` identifies
+        // them by their concrete Chrome tab id.
+        agentCreatedTabs,
         createdAtMs: this.now(),
       };
       this.sessions.set(sessionId, ctx);
@@ -253,6 +261,19 @@ export class SessionManager {
         try {
           await this.agentWindow.remove(windowId);
         } catch (cleanupError) {
+          // The daemon may retry stop after a failed startup rollback. Retain
+          // the exact window handle until closure is confirmed.
+          const pending: SessionContext = {
+            ...(this.remote() ? { remote: true } : {}),
+            sessionId,
+            agentWindowId: windowId,
+            refStore: new RefStore(),
+            borrowedTabs: new Map(),
+            agentCreatedTabs,
+            createdAtMs: this.now(),
+          };
+          this.sessions.set(sessionId, pending);
+          this.windowIndex.set(windowId, sessionId);
           throw new SessionStartCleanupError(windowId, startupError, cleanupError);
         }
       }

apps/extension/src/tools/__tests__/background-execution.browser.test.ts

@@ -133,7 +133,7 @@ describe.skipIf(!process.env.BSK_BACKGROUND_CHROME)(
               );
               const manager = new SessionManager({
                 agentWindow: {
-                  create: async () => 100,
+                  create: async () => ({ windowId: 100, initialTabIds: [] }),
                   remove: async () => {},
                   ensureActiveTab: async () => 1,
                 },

apps/extension/src/tools/__tests__/background-execution.test.ts

@@ -6,7 +6,7 @@ import { prepareBackgroundExecution } from "../background-execution";
 async function fixture() {
   const manager = new SessionManager({
     agentWindow: {
-      create: async () => 100,
+      create: async () => ({ windowId: 100, initialTabIds: [] }),
       remove: async () => {},
       ensureActiveTab: async () => 1,
     },

apps/extension/src/tools/__tests__/background-screenshot.browser.test.ts

@@ -128,7 +128,7 @@ describe.skipIf(!process.env.BSK_BACKGROUND_CHROME)(
               );
             const manager = new SessionManager({
               agentWindow: {
-                create: async () => 100,
+                create: async () => ({ windowId: 100, initialTabIds: [] }),
                 remove: async () => {},
                 ensureActiveTab: async () => 1,
               },

apps/extension/src/tools/__tests__/click.browser.test.ts

@@ -81,7 +81,7 @@ describe.skipIf(!process.env.BSK_CLICK_CHROME)("real browser click readiness", (
           const foreground = await page(false);
           const manager = new SessionManager({
             agentWindow: {
-              create: async () => 100,
+              create: async () => ({ windowId: 100, initialTabIds: [] }),
               remove: async () => {},
               ensureActiveTab: async () => 4,
             },

apps/extension/src/tools/__tests__/console.test.ts

@@ -10,7 +10,7 @@ function fakeAgentWindow(ids: number[]) {
     create: vi.fn(async () => {
       const id = ids[i++];
       if (id === undefined) throw new Error("ran out of fake ids");
-      return id;
+      return { windowId: id, initialTabIds: [] };
     }),
     remove: vi.fn(async () => {}),
     ensureActiveTab: vi.fn(async () => 1),