diff --git a/apps/server/src/config.ts b/apps/server/src/config.ts
index 17ffd104..23d1016d 100644
--- a/apps/server/src/config.ts
+++ b/apps/server/src/config.ts
@@ -87,6 +87,11 @@ export const ConfigSchema = z.object({
   BROWSER_PROVIDER_URL: z.preprocess(emptyToUndef, z.string().url().optional()),
   /** 该服务的访问凭据(camofox CAMOFOX_ACCESS_KEY);只在进程内使用,不入库 */
   BROWSER_ACCESS_KEY: z.preprocess(emptyToUndef, z.string().min(1).optional()),
+  /**
+   * 浏览器会话保活间隔(毫秒,AG-4):桌面接管 / 人工接管 / 智能体正在用的会话每隔这么久做一次只读调用,
+   * 避免 camofox 空闲 5 分钟回收标签页;0 = 关闭。要比 camofox 的 TAB_INACTIVITY_MS 短。
+   */
+  BROWSER_KEEPALIVE_MS: z.preprocess(emptyToUndef, z.coerce.number().int().min(0).default(120_000)),
   /** false = 停用 camofox-env(容器可照常运行,界面标"浏览器不可用") */
   BROWSER_ENABLED: z.preprocess(
     emptyToUndef,
diff --git a/apps/server/src/modules/browser/__tests__/browser-keepalive.test.ts b/apps/server/src/modules/browser/__tests__/browser-keepalive.test.ts
new file mode 100644
index 00000000..61c92d4b
--- /dev/null
+++ b/apps/server/src/modules/browser/__tests__/browser-keepalive.test.ts
@@ -0,0 +1,183 @@
+import { afterAll, beforeAll, describe, expect, it } from "vitest";
+import { browserServiceFor } from "../index.ts";
+import { BrowserKeepalive } from "../keepalive.ts";
+import { type BrowserHarness, createBrowserHarness, type Loose, ORIGIN, pgAvailable } from "./harness.ts";
+
+// AG-4 浏览器会话保活(对 testkit mock camofox):桌面连接 / 人工接管 / 智能体会话正在用的会话定期做一次
+// GET /tabs/{id}/downloads(不带 includeData / consume);用完不再保活;保活时标签页已被回收 → BR-3 自愈重连。
+
+describe("BrowserKeepalive(登记与复查)", () => {
+  const fake = () => {
+    const calls: string[] = [];
+    const alive = new Set<string>(["s1", "s2"]);
+    return {
+      calls,
+      alive,
+      target: {
+        keepAlive: async (id: string) => {
+          calls.push(id);
+          return alive.has(id);
+        },
+      },
+    };
+  };
+
+  it("引用计数:同一会话多个桌面连接,全部断开才停;撤销可重复调用", async () => {
+    const f = fake();
+    const k = new BrowserKeepalive(f.target, { intervalMs: 60_000 });
+    const a = k.hold("s1", "desktop", "desktop");
+    const b = k.hold("s1", "desktop", "desktop");
+    await k.tick();
+    expect(f.calls).toEqual(["s1"]);
+    a();
+    a();
+    expect(k.sessions()).toEqual([{ sessionId: "s1", reasons: ["desktop"] }]);
+    b();
+    expect(k.sessions()).toEqual([]);
+    await k.tick();
+    expect(f.calls).toEqual(["s1"]);
+  });
+
+  it("复查不通过的登记撤销;会话已关闭(keepAlive 返回 false)整条撤销;ensure 不加引用计数", async () => {
+    const f = fake();
+    const k = new BrowserKeepalive(f.target, { intervalMs: 60_000 });
+    let running = true;
+    k.ensure("s1", "agent:r1", "agent", async () => running);
+    k.ensure("s1", "agent:r1", "agent", async () => running);
+    k.hold("s2", "desktop", "desktop");
+    await k.tick();
+    expect(f.calls.sort()).toEqual(["s1", "s2"]);
+    running = false;
+    f.alive.delete("s2");
+    await k.tick();
+    expect(f.calls).toHaveLength(3); // s1 复查不通过不再保活;s2 保活一次后发现已关闭
+    expect(k.sessions()).toEqual([]);
+  });
+
+  it("保活失败只记日志,下一轮继续;intervalMs = 0 时不登记", async () => {
+    const logs: string[] = [];
+    let fail = true;
+    const k = new BrowserKeepalive(
+      {
+        keepAlive: async () => {
+          if (fail) throw new Error("浏览器服务不可用");
+          return true;
+        },
+      },
+      { intervalMs: 60_000, log: (_l, msg, extra) => logs.push(`${msg} ${String(extra?.err)}`) },
+    );
+    k.hold("s1", "takeover", "takeover");
+    await k.tick();
+    expect(logs).toEqual(["浏览器会话保活失败 浏览器服务不可用"]);
+    fail = false;
+    await k.tick();
+    expect(k.sessions()).toHaveLength(1);
+    k.stop();
+
+    const off = new BrowserKeepalive(fake().target, { intervalMs: 0 });
+    off.hold("s1", "desktop", "desktop");
+    expect(off.sessions()).toEqual([]);
+  });
+});
+
+const up = await pgAvailable();
+
+describe.skipIf(!up)("AG-4 浏览器会话保活(mock camofox)", () => {
+  let h: BrowserHarness;
+  const svc = () => browserServiceFor(h.ctx)!;
+  const open = async (path: string) =>
+    (await h.req("/browser/sessions", { body: { siteId: h.siteId, accountId: h.accountId, url: `${ORIGIN}${path}` } }))
+      .body.data as Loose;
+  const pings = (tabId: string) =>
+    h.mock.callsTo(`/tabs/${encodeURIComponent(tabId)}/downloads`).filter((c) => c.method === "GET");
+  const view = async (id: string) => (await h.req(`/browser/sessions/${id}`)).body.data as Loose;
+
+  beforeAll(async () => {
+    h = await createBrowserHarness("ag4ka");
+    await h.grant("browser.navigate");
+  }, 120_000);
+  afterAll(async () => {
+    svc()?.keepalive.stop();
+    await h?.close();
+  });
+
+  it("人工接管期间保活:只读调用、不记自动化活动;交还后停止", async () => {
+    const s = await open("/torrents.php");
+    const before = (await view(s.id)).lastAutomationAt;
+    const acq = await h.req(`/browser/sessions/${s.id}/control/acquire`, { body: { reason: "核对" } });
+    expect(acq.status).toBe(200);
+    expect(svc().keepalive.sessions()).toEqual([{ sessionId: s.id, reasons: ["takeover"] }]);
+
+    await svc().keepalive.tick();
+    const p = pings(s.currentTabId);
+    expect(p).toHaveLength(1);
+    // 不带 includeData / consume:不读下载内容、不清下载记录
+    expect(p[0]!.query).toEqual({ userId: s.profileKey });
+    const v = await view(s.id);
+    expect(v.controller).toBe("human");
+    expect(v.lastAutomationAt).toBe(before);
+
+    await h.req(`/browser/sessions/${s.id}/control/release`, { body: { to: "automation", reason: "done" } });
+    expect(svc().keepalive.sessions()).toEqual([]);
+    await svc().keepalive.tick();
+    expect(pings(s.currentTabId)).toHaveLength(1);
+    await h.req(`/browser/sessions/${s.id}`, { method: "DELETE" });
+  });
+
+  it("桌面连接期间标签页被空闲回收 → 保活时按 BR-3 自愈重连回到原地址;断开后停止", async () => {
+    const s = await open("/details.php?id=42");
+    const release = svc().keepalive.hold(s.id, "desktop", "desktop");
+    // 上游空闲回收了标签页
+    h.mock.tabs.delete(s.currentTabId);
+    await svc().keepalive.tick();
+    const v = await view(s.id);
+    expect(v.currentTabId).not.toBe(s.currentTabId);
+    // 回到会话记录的地址(测试账号没有登录态,mock 站点跳登录页并带 returnto)
+    expect(decodeURIComponent(v.currentUrl)).toContain("/details.php?id=42");
+    expect(v.reconnect).toMatchObject({ status: "ok", trigger: "tab_gone" });
+    // 新标签页上重试了保活
+    expect(pings(v.currentTabId)).toHaveLength(1);
+
+    release();
+    expect(svc().keepalive.sessions()).toEqual([]);
+    await h.req(`/browser/sessions/${s.id}`, { method: "DELETE" });
+  });
+
+  it("智能体会话在用:运行中保活;会话结束后停止;浏览器会话关闭也停止", async () => {
+    const run = await h.db
+      .insertInto("agent_run")
+      .values({
+        trigger: "user",
+        goal: "看看种子列表",
+        status: "running",
+        mode: "execute",
+        scope: JSON.stringify({}),
+        budget: JSON.stringify({}),
+        created_by: "user:admin",
+      })
+      .returning("id")
+      .executeTakeFirstOrThrow();
+    const nav = (await h.registry.invoke(
+      "browser.navigate",
+      { siteId: h.siteId, url: `${ORIGIN}/torrents.php` },
+      { ...h.agentCtx(), agentRunId: run.id },
+    )) as Loose;
+    const sid = nav.sessionId as string;
+    expect(svc().keepalive.sessions()).toEqual([{ sessionId: sid, reasons: ["agent"] }]);
+    const tab = (await view(sid)).currentTabId as string;
+    await svc().keepalive.tick();
+    expect(pings(tab)).toHaveLength(1);
+
+    await h.db.updateTable("agent_run").set({ status: "succeeded" }).where("id", "=", run.id).execute();
+    await svc().keepalive.tick();
+    expect(pings(tab)).toHaveLength(1);
+    expect(svc().keepalive.sessions()).toEqual([]);
+
+    // 再用一次(新会话在跑)→ 登记;关闭浏览器会话 → 撤销
+    await h.db.updateTable("agent_run").set({ status: "running" }).where("id", "=", run.id).execute();
+    await h.registry.invoke("browser.snapshot", { sessionId: sid }, { ...h.agentCtx(), agentRunId: run.id });
+    expect(svc().keepalive.sessions()).toHaveLength(1);
+    await h.req(`/browser/sessions/${sid}`, { method: "DELETE" });
+    expect(svc().keepalive.sessions()).toEqual([]);
+  });
+});
diff --git a/apps/server/src/modules/browser/capabilities.ts b/apps/server/src/modules/browser/capabilities.ts
index d2aca8ac..30216b46 100644
--- a/apps/server/src/modules/browser/capabilities.ts
+++ b/apps/server/src/modules/browser/capabilities.ts
@@ -27,7 +27,12 @@ async function guard<T>(fn: () => Promise<T>): Promise<T> {
   }
 }
 
-const agent = (actorId: string): Actor => ({ kind: "automation", holder: actorId });
+/** 以自动化身份执行;智能体会话里调用时带上会话 ID(会话在跑期间保活这个浏览器会话,AG-4) */
+const agent = (ctx: HandlerContext): Actor => ({
+  kind: "automation",
+  holder: ctx.actorId,
+  ...(ctx.agentRunId ? { agentRunId: ctx.agentRunId } : {}),
+});
 
 /** 敏感截图(登录页 / 密码框)交给模型的授权:有效的 browser.sensitive_screenshot(或 *)持续授权 */
 export const SENSITIVE_SCREENSHOT_GRANT = "browser.sensitive_screenshot";
@@ -61,7 +66,7 @@ export function registerBrowserCapabilities(registry: CapabilityRegistry, svc: (
       const id = await resolveSession(input);
       const snap = await svc().run(
         id,
-        agent(ctx.actorId),
+        agent(ctx),
         (p, ref) => p.snapshot(ref, input.offset !== undefined ? { offset: input.offset } : {}),
         { write: false, patch: () => ({ needsSnapshot: false }), ...(input.tabId ? { tabId: input.tabId } : {}) },
       );
@@ -91,6 +96,7 @@ export function registerBrowserCapabilities(registry: CapabilityRegistry, svc: (
             url: input.url,
           }));
         if (!live) {
+          if (ctx.agentRunId) svc().holdForAgent(id, ctx.agentRunId);
           const v = await svc().view(id);
           const info = v.currentUrl ?? "";
           return {
@@ -107,7 +113,7 @@ export function registerBrowserCapabilities(registry: CapabilityRegistry, svc: (
       const sid = id;
       const nav = await svc().run(
         sid,
-        agent(ctx.actorId),
+        agent(ctx),
         async (p, ref, x) => {
           await svc().limited(x.site);
           // 标签页全被上游回收(重启 / 空闲超时,已对账为 lost):在同一会话(同一 profile)里开新标签页,不重放旧引用
@@ -143,7 +149,7 @@ export function registerBrowserCapabilities(registry: CapabilityRegistry, svc: (
       if (needTarget && !input.target) throw new BrowserServiceError("bad_request", `${input.action} 需要 target`);
       await s.run(
         input.sessionId,
-        agent(ctx.actorId),
+        agent(ctx),
         async (p, ref, x) => {
           switch (input.action) {
             case "click":
@@ -183,7 +189,7 @@ export function registerBrowserCapabilities(registry: CapabilityRegistry, svc: (
       const s = svc();
       const artifact = await s.run(
         input.sessionId,
-        agent(ctx.actorId),
+        agent(ctx),
         async (p, ref) => {
           if (input.target) await p.click(ref, input.target);
           return p.waitForDownload(ref, { timeoutMs: input.timeoutMs, maxBytes: 10 * 1024 * 1024 });
@@ -221,7 +227,7 @@ export function registerBrowserCapabilities(registry: CapabilityRegistry, svc: (
   registry.register(capabilitySpec("browser.screenshot"), (input, ctx) =>
     guard(async () => {
       const s = svc();
-      return s.capture(input.sessionId, agent(ctx.actorId), {
+      return s.capture(input.sessionId, agent(ctx), {
         ...(input.tabId ? { tabId: input.tabId } : {}),
         wantImage: wantImage(ctx),
         sensitiveAllowed: await sensitiveAllowed(s, input.allowSensitive),
@@ -238,7 +244,7 @@ export function registerBrowserCapabilities(registry: CapabilityRegistry, svc: (
     const s = svc();
     const page = point ? s.toPage(input.sessionId, point.x, point.y) : null;
     const at = page ? { x: page.pageX, y: page.pageY } : null;
-    const shot = await s.visionAct(input.sessionId, agent(ctx.actorId), (p, ref) => fn(p, ref, at), {
+    const shot = await s.visionAct(input.sessionId, agent(ctx), (p, ref) => fn(p, ref, at), {
       wantImage: wantImage(ctx),
       sensitiveAllowed: await sensitiveAllowed(s, input.allowSensitive),
     });
@@ -280,7 +286,7 @@ export function registerBrowserCapabilities(registry: CapabilityRegistry, svc: (
     guard(async () => {
       const s = svc();
       await new Promise((r) => setTimeout(r, input.ms));
-      const shot = await s.capture(input.sessionId, agent(ctx.actorId), {
+      const shot = await s.capture(input.sessionId, agent(ctx), {
         wantImage: wantImage(ctx),
         sensitiveAllowed: await sensitiveAllowed(s, input.allowSensitive),
       });
diff --git a/apps/server/src/modules/browser/keepalive.ts b/apps/server/src/modules/browser/keepalive.ts
new file mode 100644
index 00000000..80368f3c
--- /dev/null
+++ b/apps/server/src/modules/browser/keepalive.ts
@@ -0,0 +1,165 @@
+// AG-4 浏览器会话保活:camofox 的标签页空闲 TAB_INACTIVITY_MS(缺省 5 分钟)没有 API 调用就回收,
+// 会话空闲 SESSION_TIMEOUT_MS 回收,全部会话没了之后 BROWSER_IDLE_TIMEOUT_MS 退出浏览器。
+// 桌面模式里人的键鼠直接进 Selkies,不经 API;原站视图的截图轮询也不算标签页活动——接管期间页面会被关掉。
+// 这里在"有人 / 有智能体正在用"的会话上每隔 intervalMs 做一次最轻的只读调用(BrowserProvider.keepAlive),
+// 用完(桌面断开、交还 / 接管结束、智能体会话结束、会话关闭)就不再保活,照常由上游空闲回收。
+// 保活调用走 BrowserService.run:浏览器重启过 / 标签页已被回收时按 BR-3 自愈重连。
+// 保活登记只在进程内:api 进程登记桌面与接管,跑智能体的进程登记智能体会话,各自保活自己的。
+
+/** 缺省保活间隔:比上游 5 分钟空闲回收短一半还多 */
+export const BROWSER_KEEPALIVE_MS = 120_000;
+/** 智能体会话最后一次用这个浏览器会话之后,最多再保活多久(兜底:会话状态读不到时也会停) */
+export const AGENT_KEEPALIVE_MAX_IDLE_MS = 30 * 60_000;
+
+export type KeepaliveReason = "desktop" | "takeover" | "agent";
+
+interface Hold {
+  reason: KeepaliveReason;
+  /** 引用计数(同一桌面会话开了多个连接) */
+  refs: number;
+  /** 每次保活前复查;false = 不再需要 */
+  check?: () => Promise<boolean>;
+}
+
+export interface KeepaliveTarget {
+  /** 对会话做一次保活;会话已关闭返回 false */
+  keepAlive(sessionId: string): Promise<boolean>;
+}
+
+export interface KeepaliveOptions {
+  /** 0 = 关闭保活 */
+  intervalMs: number;
+  log?: (level: "info" | "warn", msg: string, extra?: Record<string, unknown>) => void;
+}
+
+export class BrowserKeepalive {
+  /** sessionId → (登记键 → 登记) */
+  private readonly holds = new Map<string, Map<string, Hold>>();
+  private timer: ReturnType<typeof setInterval> | undefined;
+  private ticking: Promise<void> | null = null;
+
+  constructor(
+    private readonly target: KeepaliveTarget,
+    private readonly opts: KeepaliveOptions,
+  ) {}
+
+  get enabled(): boolean {
+    return this.opts.intervalMs > 0;
+  }
+
+  /** 当前在保活的会话(测试 / 状态页用) */
+  sessions(): { sessionId: string; reasons: KeepaliveReason[] }[] {
+    return [...this.holds].map(([sessionId, m]) => ({
+      sessionId,
+      reasons: [...new Set([...m.values()].map((h) => h.reason))],
+    }));
+  }
+
+  /**
+   * 登记一个使用方;返回的函数撤销这一次登记(可重复调用)。同一 key 多次登记按引用计数。
+   * check 在每次保活前复查,返回 false 时整条登记撤销。
+   */
+  hold(sessionId: string, key: string, reason: KeepaliveReason, check?: () => Promise<boolean>): () => void {
+    if (!this.enabled) return () => {};
+    let m = this.holds.get(sessionId);
+    if (!m) {
+      m = new Map();
+      this.holds.set(sessionId, m);
+    }
+    const cur = m.get(key);
+    if (cur) {
+      cur.refs++;
+      if (check) cur.check = check;
+    } else m.set(key, { reason, refs: 1, ...(check ? { check } : {}) });
+    this.ensureTimer();
+    let released = false;
+    return () => {
+      if (released) return;
+      released = true;
+      const h = this.holds.get(sessionId)?.get(key);
+      if (!h) return;
+      if (--h.refs <= 0) this.unhold(sessionId, key);
+    };
+  }
+
+  /** 没登记过才登记(不加引用计数);已登记时只换复查函数。用于"最近在用"类登记(智能体会话每次调用都会续) */
+  ensure(sessionId: string, key: string, reason: KeepaliveReason, check?: () => Promise<boolean>): void {
+    const h = this.holds.get(sessionId)?.get(key);
+    if (h) {
+      if (check) h.check = check;
+      return;
+    }
+    this.hold(sessionId, key, reason, check);
+  }
+
+  /** 撤销某个 key 的登记(不管引用计数) */
+  unhold(sessionId: string, key: string): void {
+    const m = this.holds.get(sessionId);
+    if (!m) return;
+    m.delete(key);
+    if (!m.size) this.holds.delete(sessionId);
+    this.maybeStop();
+  }
+
+  /** 会话关闭:撤销全部登记 */
+  drop(sessionId: string): void {
+    if (this.holds.delete(sessionId)) this.maybeStop();
+  }
+
+  /** 一轮保活(定时器调用;测试直接调) */
+  tick(): Promise<void> {
+    if (this.ticking) return this.ticking;
+    this.ticking = this.runTick().finally(() => {
+      this.ticking = null;
+    });
+    return this.ticking;
+  }
+
+  stop(): void {
+    this.holds.clear();
+    this.maybeStop();
+  }
+
+  private async runTick(): Promise<void> {
+    for (const [sessionId, m] of [...this.holds]) {
+      for (const [key, h] of [...m]) {
+        if (!h.check) continue;
+        const ok = await h.check().catch(() => true);
+        if (!ok) m.delete(key);
+      }
+      if (!m.size) {
+        this.holds.delete(sessionId);
+        continue;
+      }
+      try {
+        const alive = await this.target.keepAlive(sessionId);
+        if (!alive) this.holds.delete(sessionId);
+      } catch (e) {
+        // 自愈重连也失败(浏览器服务不可用等):记日志,下一轮再试;会话本身的状态由 run() 写好(needsReconnect / reconnect.failed)
+        this.opts.log?.("warn", "浏览器会话保活失败", {
+          sessionId,
+          reasons: [...new Set([...m.values()].map((x) => x.reason))],
+          err: e instanceof Error ? e.message : String(e),
+        });
+      }
+    }
+    this.maybeStop();
+  }
+
+  private ensureTimer(): void {
+    if (this.timer !== undefined || !this.enabled) return;
+    this.timer = setInterval(() => void this.tick(), this.opts.intervalMs);
+    // 不拖住进程退出(测试、优雅停机)
+    try {
+      Deno.unrefTimer(this.timer as unknown as number);
+    } catch {
+      /* 非 Deno 运行时 */
+    }
+  }
+
+  private maybeStop(): void {
+    if (this.holds.size || this.timer === undefined) return;
+    clearInterval(this.timer);
+    this.timer = undefined;
+  }
+}
diff --git a/apps/server/src/modules/browser/service.ts b/apps/server/src/modules/browser/service.ts
index 8fdda9b3..bc5b6ac4 100644
--- a/apps/server/src/modules/browser/service.ts
+++ b/apps/server/src/modules/browser/service.ts
@@ -59,12 +59,18 @@ import {
 } from "../sources-identity/service/credentials.ts";
 import { registerBrowserIdentityReader } from "../sources-identity/service/user-agent.ts";
 import type { ServerContext } from "../types.ts";
+import { AGENT_KEEPALIVE_MAX_IDLE_MS, BROWSER_KEEPALIVE_MS, BrowserKeepalive } from "./keepalive.ts";
 
 // C1-E 浏览器服务层:BrowserProvider(camofox)之上的会话/标签/控制权持久化(数据库为准)、
 // 站点域名白名单 + 站点限流、凭证注入、接管状态机、下载产物暂存核验。
 // 适配器只是内存镜像:服务重启后按数据库恢复,旧元素引用一律失效。
 
-export type Actor = { kind: "automation" | "human"; holder: string };
+export type Actor = {
+  kind: "automation" | "human";
+  holder: string;
+  /** 智能体会话发起的动作(AG-4):会话还在跑期间保活这个浏览器会话 */
+  agentRunId?: string;
+};
 
 export interface BrowserModuleOptions {
   /** camofox 请求用的 fetch(测试指向 mock) */
@@ -79,6 +85,8 @@ export interface BrowserModuleOptions {
   evidenceDir?: string;
   /** 坐标动作之后等页面稳定再截图的毫秒数;缺省 400 */
   settleMs?: number;
+  /** 保活间隔(AG-4);缺省 BROWSER_KEEPALIVE_MS 配置(120 秒),0 = 关闭 */
+  keepaliveMs?: number;
   /** 测试替换 provider 实现 */
   providerFactory?: (row: BrowserProviderRow, deps: ProviderDeps) => BrowserProvider;
 }
@@ -194,12 +202,21 @@ export class BrowserService {
   private readonly providers = new Map<string, { sig: string; provider: BrowserProvider }>();
   private envSync: Promise<void> | undefined;
   readonly now: () => Date;
+  /** AG-4 保活:桌面 / 人工接管 / 智能体正在用的会话定期做一次只读调用 */
+  readonly keepalive: BrowserKeepalive;
 
   constructor(
     readonly ctx: ServerContext,
     readonly opts: BrowserModuleOptions = {},
   ) {
     this.now = opts.now ?? (() => new Date());
+    this.keepalive = new BrowserKeepalive(
+      { keepAlive: (id) => this.keepAlive(id) },
+      {
+        intervalMs: opts.keepaliveMs ?? ctx.config?.BROWSER_KEEPALIVE_MS ?? BROWSER_KEEPALIVE_MS,
+        log: (level, msg, extra) => ctx.logger[level]({ component: "browser", ...extra }, msg),
+      },
+    );
     // refresh-login 发现 Cookie 失效时从浏览器 profile 读回一次(sources-identity 经钩子调用,不直接依赖本模块)
     registerBrowserCookieReader(ctx, (siteId, accountId) => this.readProfileCookie(siteId, accountId));
     // 站点请求 UA 跟随浏览器固定身份(BR-4):sources-identity 经钩子取
@@ -1081,6 +1098,7 @@ export class BrowserService {
   }
 
   async close(id: string, reason = "closed"): Promise<void> {
+    this.keepalive.drop(id);
     const row = await this.sessionRow(id);
     if (row.controller === "closed") return;
     const prow = await this.ctx.db
@@ -1235,9 +1253,38 @@ export class BrowserService {
         .execute();
       return l;
     });
+    // 接管期间人的操作不经上游 API(桌面模式),由 app 保活;交还 / 租约过期 / 会话关闭后停
+    this.keepalive.ensure(id, "takeover", "takeover", () => this.humanHolding(id));
     return toLease(lease);
   }
 
+  /** 会话仍在人工接管中(租约有效) */
+  private async humanHolding(id: string): Promise<boolean> {
+    const row = await this.sessionRow(id).catch(() => null);
+    if (row?.controller !== "human") return false;
+    const lease = await this.activeLease(id);
+    return lease?.holder_kind === "human" && new Date(lease.expires_at).getTime() > this.now().getTime();
+  }
+
+  /**
+   * 保活一次(AG-4):对当前标签页做最轻的只读调用。不要求控制权、不记自动化活动;浏览器重启过 / 标签页已被回收时
+   * 按 BR-3 自愈重连(注入 Cookie、回到原地址)。会话已关闭返回 false;上游不支持保活时只做实例检查与对账。
+   */
+  async keepAlive(id: string): Promise<boolean> {
+    const row = await this.sessionRow(id).catch(() => null);
+    if (!row || row.controller === "closed") return false;
+    await this.run(
+      id,
+      { kind: "automation", holder: "system:keepalive" },
+      async (p, ref) => {
+        if (p.keepAlive) await p.keepAlive(ref);
+        else await p.reconcileTabs(id);
+      },
+      { write: false, persist: false, background: true },
+    );
+    return true;
+  }
+
   /** 交还:回到自动化(或留在等待处理);Agent 恢复前必须重新读取页面,不复用旧引用、不重放旧点击 */
   async release(
     id: string,
@@ -1248,6 +1295,7 @@ export class BrowserService {
     if (lease?.holder_kind !== "human" || (opts.leaseId && lease.id !== opts.leaseId))
       throw new BrowserServiceError("conflict", "没有可交还的人工接管");
     const at = this.now();
+    this.keepalive.unhold(id, "takeover");
     const { provider } = await this.loaded(row);
     provider.setController(id, opts.to);
     const rs = obj(row.recovery_state) as RecoveryState;
@@ -1296,7 +1344,14 @@ export class BrowserService {
       ref: TabRef,
       ctx: { row: BrowserSessionRow; site: SiteRow; budget: NavigationBudget },
     ) => Promise<T>,
-    opts: { tabId?: string; write?: boolean; persist?: boolean; patch?: (out: T) => RecoveryState } = {},
+    opts: {
+      tabId?: string;
+      write?: boolean;
+      persist?: boolean;
+      patch?: (out: T) => RecoveryState;
+      /** 后台维护调用(保活):不记自动化活动 */
+      background?: boolean;
+    } = {},
   ): Promise<T> {
     let row = await this.expireLeases(await this.sessionRow(id));
     if (row.controller === "closed") throw new BrowserServiceError("conflict", "会话已关闭");
@@ -1366,7 +1421,9 @@ export class BrowserService {
         throw fromBrowserError(e2);
       }
     }
-    const automation: RecoveryState = actor.kind === "automation" ? { lastAutomationAt: this.now().toISOString() } : {};
+    const automation: RecoveryState =
+      actor.kind === "automation" && !opts.background ? { lastAutomationAt: this.now().toISOString() } : {};
+    if (actor.agentRunId) this.holdForAgent(id, actor.agentRunId);
     if (opts.persist !== false)
       await this.persist(id, loaded.provider, { ...(opts.patch?.(out) ?? {}), ...automation });
     else if (automation.lastAutomationAt) await this.patchRecovery(await this.sessionRow(id), automation);
@@ -1374,6 +1431,23 @@ export class BrowserService {
     return out;
   }
 
+  /** 智能体会话最后一次用各浏览器会话的时间(保活复查用) */
+  private readonly agentUse = new Map<string, number>();
+
+  /** 智能体会话在用这个浏览器会话:会话还在排队 / 运行期间保活(最后一次使用后最多 AGENT_KEEPALIVE_MAX_IDLE_MS) */
+  holdForAgent(sessionId: string, runId: string): void {
+    const key = `agent:${runId}`;
+    this.agentUse.set(`${sessionId}|${runId}`, Date.now());
+    this.keepalive.ensure(sessionId, key, "agent", async () => {
+      const last = this.agentUse.get(`${sessionId}|${runId}`) ?? 0;
+      const r = await this.ctx.db.selectFrom("agent_run").select("status").where("id", "=", runId).executeTakeFirst();
+      const ok =
+        !!r && (r.status === "running" || r.status === "queued") && Date.now() - last < AGENT_KEEPALIVE_MAX_IDLE_MS;
+      if (!ok) this.agentUse.delete(`${sessionId}|${runId}`);
+      return ok;
+    });
+  }
+
   // ---------- BR-3 浏览器服务重启后自愈 ----------
 
   /** 各浏览器服务最近一次读到的实例标识(节流缓存;只在进程内) */
diff --git a/apps/server/src/modules/desktop/desktop.ts b/apps/server/src/modules/desktop/desktop.ts
index 621f2b47..40bbdfbc 100644
--- a/apps/server/src/modules/desktop/desktop.ts
+++ b/apps/server/src/modules/desktop/desktop.ts
@@ -64,6 +64,8 @@ export interface DesktopDeps {
   fetch?: typeof fetch;
   /** 角色复查间隔 */
   roleCheckMs?: number;
+  /** 桌面连接建立(AG-4):返回连接断开时调用的函数。用于连接期间保活浏览器会话 */
+  onConnect?: (sessionId: string) => () => void;
   /** 可用性探测缓存 */
   probeTtlMs?: number;
   log?: (msg: string, extra?: Record<string, unknown>) => void;
@@ -256,6 +258,7 @@ export function registerDesktopRoutes(app: ModuleApp, deps: DesktopDeps): { clos
       if (!sameOrigin(c.req.raw)) throw new ApiException("forbidden", "桌面连接必须来自本站页面");
       const s = await requireSession(deps, sessionId, holder);
       return bridgeWebSocket(c.req.raw, target.replace(/^http/, "ws"), s.role, {
+        ...(deps.onConnect ? { onOpen: () => deps.onConnect?.(sessionId) ?? (() => {}) } : {}),
         auth: (role) => basicAuth(passwords[role]),
         recheck: async () => {
           if (!(await deps.consoleSessionValid(sessionRowId))) return null;
@@ -312,6 +315,8 @@ interface BridgeOpts {
   roleCheckMs: number;
   live: Set<() => void>;
   log(msg: string, extra?: Record<string, unknown>): void;
+  /** 连接已升级:返回断开时调用的函数(保活登记) */
+  onOpen?: () => () => void;
 }
 
 /** 浏览器 ⇄ app ⇄ Selkies 的 WebSocket 双向转发;角色变化时断开(客户端重连后按新角色认证) */
@@ -321,6 +326,7 @@ function bridgeWebSocket(req: Request, target: string, role: DesktopRole, o: Bri
     .map((s) => s.trim())
     .filter(Boolean);
   const { socket: client, response } = Deno.upgradeWebSocket(req, protocols[0] ? { protocol: protocols[0] } : {});
+  const onClose = o.onOpen?.();
   client.binaryType = "arraybuffer";
   // Deno 的客户端 WebSocket 支持自定义请求头;不带 Origin(Selkies 对无 Origin 的非浏览器客户端放行)
   // (tsc 按 DOM 类型只认 protocols 参数;Deno 运行时接受 { headers, protocols })
@@ -336,6 +342,7 @@ function bridgeWebSocket(req: Request, target: string, role: DesktopRole, o: Bri
     closed = true;
     if (timer !== undefined) clearInterval(timer);
     o.live.delete(close);
+    onClose?.();
     try {
       if (client.readyState <= WebSocket.OPEN) client.close(code, reason);
     } catch {
diff --git a/apps/server/src/modules/desktop/index.ts b/apps/server/src/modules/desktop/index.ts
index a05deae4..2dbe9fd1 100644
--- a/apps/server/src/modules/desktop/index.ts
+++ b/apps/server/src/modules/desktop/index.ts
@@ -1,3 +1,4 @@
+import { browserServiceFor } from "../browser/index.ts";
 import type { ServerContext, ServerModule } from "../types.ts";
 import { dbSessionChecks, desktopUpstream, registerDesktopRoutes } from "./desktop.ts";
 
@@ -18,6 +19,8 @@ export function createDesktopModule(): ServerModule {
         }),
         accessKey: ctx.config?.BROWSER_ACCESS_KEY ?? null,
         ...dbSessionChecks(ctx.db),
+        // 桌面连接期间保活浏览器会话(AG-4):人在桌面里的操作不经 camofox API,不保活会被空闲 5 分钟回收
+        onConnect: (sessionId) => browserServiceFor(ctx)?.keepalive.hold(sessionId, "desktop", "desktop") ?? (() => {}),
         log: (msg, extra) => ctx.logger.warn({ component: "desktop", ...extra }, msg),
       });
       closeAll = r.closeAll;
diff --git a/docker-compose.yml b/docker-compose.yml
index 6829f3a2..ff3d2063 100644
--- a/docker-compose.yml
+++ b/docker-compose.yml
@@ -191,6 +191,8 @@ services:
       BROWSER_PROVIDER_URL: ${BROWSER_PROVIDER_URL:-http://camofox:9377}
       BROWSER_ACCESS_KEY: ${BROWSER_ACCESS_KEY:-${CAMOFOX_ACCESS_KEY:-}}
       BROWSER_ENABLED: ${BROWSER_ENABLED:-true}
+      # 桌面接管 / 人工接管 / 智能体正在用的会话每隔多久保活一次(camofox 标签页空闲 5 分钟回收);0 = 关闭
+      BROWSER_KEEPALIVE_MS: ${BROWSER_KEEPALIVE_MS:-120000}
       # 原站视图桌面模式的上游(桌面镜像的 Selkies);缺省由 BROWSER_PROVIDER_URL 推出(端口换 3000)
       BROWSER_DESKTOP_URL: ${BROWSER_DESKTOP_URL:-}
       # 出站代理(HTTP_PROXY/HTTPS_PROXY)在 override 里给(见 docs/runbook/deploy.md「容器经宿主代理」)。
diff --git a/docker/compose.env.example b/docker/compose.env.example
index d71061fd..6a71fcb6 100644
--- a/docker/compose.env.example
+++ b/docker/compose.env.example
@@ -50,6 +50,8 @@ CAMOFOX_ACCESS_KEY=
 # 完全不用浏览器:CAMOFOX_REPLICAS=0 且 BROWSER_ENABLED=false(界面标"浏览器不可用")
 # CAMOFOX_REPLICAS=1
 # BROWSER_ENABLED=true
+# 桌面接管 / 人工接管 / 智能体正在用的浏览器会话的保活间隔(毫秒,0 = 关闭;要比 camofox 标签页空闲回收 5 分钟短)
+# BROWSER_KEEPALIVE_MS=120000
 # camofox 调优(可选):会话空闲回收(回收时落盘登录状态)、浏览器空闲退出、最多会话数、内存上限
 # CAMOFOX_SESSION_TIMEOUT_MS=1800000
 # CAMOFOX_BROWSER_IDLE_TIMEOUT_MS=300000
diff --git a/docs/runbook/browser.md b/docs/runbook/browser.md
index cedd7e87..67d080b6 100644
--- a/docs/runbook/browser.md
+++ b/docs/runbook/browser.md
@@ -342,7 +342,8 @@ docker compose cp caddy:/data/caddy/pki/authorities/local/root.crt ./umt-root.cr
 
 - Firefox 工具栏里有 Playwright 的 "JUGGLER" 标识;用户可在画面里打开 `about:addons`、新标签页、输入任意网址——越界防护
   (`policies.json`、`context.route` 白名单、交还时核对 URL,方案 §6)未做。
-- 接管期间 camofox 看不到 API 请求,`SESSION_TIMEOUT_MS`(缺省 30 分钟)到期会回收会话窗口;接管心跳(方案 §5.5 插件)未做。
+- 接管期间 camofox 看不到 API 请求:桌面连接期间与人工接管期间由 app 定期保活(§12,AG-4),不再被空闲回收;
+  浏览器里的心跳插件(方案 §5.5)不做。
 - 一个桌面承载所有站点会话:持有 A 站租约的人在画面里能看到 / 操作切到前台的其它窗口;目前同一时刻一般只有一个会话窗口。
 - 真实输入法(Windows 微软拼音、macOS 日文)、Firefox / Safari 客户端、真实 PT 站点未测;容器内 fcitx5 只验证能启动,未验证组字。
 - 画面坐标与 camofox 截图坐标不同(桌面含 56 px 工具栏,Camoufox 伪装了 `screenX` / `outerHeight`),Agent 视觉操作继续用 camofox 截图。
@@ -605,3 +606,39 @@ Camoufox 浏览器包的层都走构建缓存,**不会重新下载 Camoufox(约
 `migration-browser-identity.test.ts`、`apps/server/src/modules/browser/__tests__/browser-identity.test.ts`(出口下发、身份存库)、
 `packages/adapters/src/browser/umt-plugin.test.ts`(插件纯函数、适配器接口);真机:本地临时容器(`--network none`,只开容器内本地
 页面)核验了 §11.1 表格与 §11.5 出口行为,未对真实站点发请求。
+
+## 12. 会话保活(AG-4)
+
+camofox 按 **API 调用**判断活动,有三道空闲回收(`docker-compose.yml` 的 camofox 环境变量):
+
+| 回收 | 缺省 | 判据 |
+| --- | --- | --- |
+| 标签页 `TAB_INACTIVITY_MS` | 5 分钟 | 每 60 秒看一次标签页的 `toolCalls` 有没有变;没变且超过 5 分钟 → 关标签页,会话空了连会话一起关 |
+| 会话 `SESSION_TIMEOUT_MS` | 30 分钟 | 会话 `lastAccess`(大部分 `/tabs/{id}/*` 接口都会刷新) |
+| 浏览器 `BROWSER_IDLE_TIMEOUT_MS` | 5 分钟 | 一个会话都没有之后浏览器进程退出 |
+
+桌面模式里人的键鼠直接进 Selkies,原站视图截图(`GET /tabs/{id}/screenshot`)只刷新 `lastAccess`、不加 `toolCalls`——
+接管 5 分钟后标签页被关掉,桌面画面里的窗口消失。app 在"正在用"的会话上定期保活,代码 `modules/browser/keepalive.ts`、
+`BrowserService.keepAlive`、适配器 `keepAlive`。
+
+**保活调用**:camofox 1.17 没有 keepalive / touch 接口;`GET /tabs/{id}/stats` 只刷新 `lastAccess`,挡不住标签页回收。
+用 `GET /tabs/{id}/downloads?userId=…`(不带 `includeData` / `consume`):只列下载元数据,不读页面、不改页面、不清下载记录,
+会让 `toolCalls` 加一、刷新 `lastAccess`。只对当前标签页做,不要求控制权,不记 `lastAutomationAt`。
+
+**什么时候保活**(进程内登记,各进程保活自己登记的):
+
+| 使用方 | 开始 | 停止 |
+| --- | --- | --- |
+| 桌面连接 | 桌面模式 WebSocket 建立(控制或只读都算,多个连接按引用计数) | 全部连接断开 |
+| 人工接管 | `control/acquire` | 交还(`control/release`)、租约过期、会话关闭 |
+| 智能体会话 | 智能体会话里的浏览器能力调用(`browser.*`,含 `browser.navigate` 新开会话) | 智能体会话不再是排队 / 运行中(结束、等待下载或等用户),或最后一次使用后 30 分钟 |
+
+每 `BROWSER_KEEPALIVE_MS`(缺省 120000 = 2 分钟,0 = 关闭;要比 `TAB_INACTIVITY_MS` 短)对登记的会话各做一次;
+每轮先复查登记是否还有效,没有使用方的会话不再保活,照常由 camofox 空闲回收。会话关闭(`DELETE`)立即撤销全部登记。
+
+**保活失败**:保活走与其它动作相同的 `run()` 路径——浏览器重启过(实例标识变了)或标签页已被回收(404 / 410、适配器里没有打开的标签页)
+→ 按 §10 自愈重连(注入 Cookie、同一会话新开标签页回到原地址)后在新标签页上再保活一次;重连也失败(浏览器服务不可用)只记 warn 日志
+「浏览器会话保活失败」,会话照常标 `needsReconnect` / `reconnect.status = failed`,下一轮再试。
+
+核验:`apps/server/src/modules/browser/__tests__/browser-keepalive.test.ts`(登记 / 引用计数 / 复查;对 mock camofox:接管期间保活、
+不记自动化活动、交还后停;桌面连接期间标签页被回收 → 保活时自愈重连;智能体会话结束后停、会话关闭撤销)。真机未核验。
diff --git a/docs/runbook/deploy.md b/docs/runbook/deploy.md
index 9a95dbdf..16161ad2 100644
--- a/docs/runbook/deploy.md
+++ b/docs/runbook/deploy.md
@@ -134,6 +134,7 @@ docker compose logs app | grep 'setup token'
 | `BROWSER_PROVIDER_URL` | `http://camofox:9377` | app 登记的浏览器服务地址(`camofox-env`);接自有实例时改 |
 | `BROWSER_ACCESS_KEY` | `CAMOFOX_ACCESS_KEY` | 该服务的访问凭据,只在进程内使用,不入库 |
 | `BROWSER_ENABLED` | `true` | `false` = 停用 `camofox-env`,界面标"浏览器不可用" |
+| `BROWSER_KEEPALIVE_MS` | `120000` | 桌面接管 / 人工接管 / 智能体正在用的浏览器会话的保活间隔,0 = 关闭;要比 camofox 标签页空闲回收(5 分钟)短(`docs/runbook/browser.md` §12) |
 | `CAMOFOX_REPLICAS` | `1` | `0` = 不起 camofox 容器 |
 | `CAMOFOX_SESSION_TIMEOUT_MS` / `CAMOFOX_BROWSER_IDLE_TIMEOUT_MS` | `1800000` / `300000` | 会话空闲回收(落盘登录状态)/ 浏览器空闲退出 |
 | `CAMOFOX_MAX_SESSIONS` / `CAMOFOX_MEM_LIMIT` | `8` / `2g` | 最多并发会话 / 容器内存上限 |
diff --git a/packages/adapters/src/browser/camofox/client.ts b/packages/adapters/src/browser/camofox/client.ts
index 5229f147..dcc0e7e4 100644
--- a/packages/adapters/src/browser/camofox/client.ts
+++ b/packages/adapters/src/browser/camofox/client.ts
@@ -811,6 +811,24 @@ export class CamofoxBrowserProvider implements BrowserProvider {
     });
   }
 
+  /**
+   * AG-4 保活:camofox 1.17 没有 keepalive / touch 接口。`GET /tabs/{id}/stats` 只刷新会话的 lastAccess,
+   * 不算标签页活动(标签页回收看 toolCalls 有没有变化);最轻的会让 toolCalls 加一的只读调用是
+   * `GET /tabs/{id}/downloads`(不带 includeData / consume:只列下载元数据,不读页面、不清下载记录)。
+   */
+  async keepAlive(ref: TabRef): Promise<void> {
+    const s = this.state(ref.sessionId);
+    await this.withProfile(s, async () => {
+      const tab = this.tabOf(s, ref);
+      const path = `/tabs/${encodeURIComponent(tab.upstreamTabId)}/downloads`;
+      const res = await this.request("GET", path, {
+        query: { userId: s.session.profileKey },
+        timeoutMs: Math.min(this.cfg.timeoutMs ?? 30_000, 10_000),
+      });
+      await res.body?.cancel();
+    });
+  }
+
   // ---------- 页面 ----------
 
   async navigate(ref: TabRef, url: string, budget: NavigationBudget): Promise<NavigationResult> {
diff --git a/packages/adapters/src/browser/provider.ts b/packages/adapters/src/browser/provider.ts
index b40f5b17..4734b743 100644
--- a/packages/adapters/src/browser/provider.ts
+++ b/packages/adapters/src/browser/provider.ts
@@ -93,6 +93,14 @@ export interface BrowserProvider {
    */
   reopenSession?(sessionId: string, req: ReopenSessionRequest): Promise<ReopenSessionResult>;
 
+  // ── AG-4 保活 ──
+  /**
+   * 对标签页做一次最轻的只读调用,让上游把它算作"有活动"(camofox 标签页空闲回收 TAB_INACTIVITY_MS 与会话空闲回收
+   * SESSION_TIMEOUT_MS 都按 API 调用计;桌面模式里人的键鼠操作不经 API,不算活动)。不检查控制者、不改页面。
+   * 标签页不在了报 not_found(调用方按 BR-3 自愈重连)。
+   */
+  keepAlive?(ref: TabRef): Promise<void>;
+
   // ── BR-4 浏览器 UA 与指纹统一、出口按站点 ──
   /** 固定浏览器身份的公开部分(UA、OS、版本);上游没有时返回 null */
   identity?(): Promise<BrowserIdentity | null>;