diff --git a/packages/browseros-agent/apps/server/src/browser/browser.ts b/packages/browseros-agent/apps/server/src/browser/browser.ts
index e4a45cd83..4789dbcf0 100644
--- a/packages/browseros-agent/apps/server/src/browser/browser.ts
+++ b/packages/browseros-agent/apps/server/src/browser/browser.ts
@@ -249,6 +249,20 @@ export class Browser {
     return this.pages.get(pageId)
   }
 
+  private async resolvePageInfo(pageId: number): Promise<PageInfo | undefined> {
+    const cached = this.pages.get(pageId)
+    if (cached) return cached
+
+    await this.listPages()
+    return this.pages.get(pageId)
+  }
+
+  private unknownPageError(pageId: number): Error {
+    return new Error(
+      `Unknown page ${pageId}. Use list_pages to see available pages.`,
+    )
+  }
+
   async refreshPageInfo(pageId: number): Promise<PageInfo | undefined> {
     let info = this.pages.get(pageId)
     if (!info) {
@@ -591,15 +605,31 @@ export class Browser {
   }
 
   async closePage(page: number): Promise<void> {
-    const info = this.pages.get(page)
-    if (!info)
-      throw new Error(
-        `Unknown page ${page}. Use list_pages to see available pages.`,
-      )
-    await this.cdp.Browser.closeTab({ tabId: info.tabId })
+    let info = await this.resolvePageInfo(page)
+    if (!info) throw this.unknownPageError(page)
+    const targetIdsToDetach = new Set([info.targetId])
+
+    try {
+      await this.cdp.Browser.closeTab({ targetId: info.targetId })
+    } catch (error) {
+      const refreshed = await this.refreshPageInfo(page)
+      if (
+        !refreshed ||
+        (refreshed.targetId === info.targetId && refreshed.tabId === info.tabId)
+      ) {
+        throw error
+      }
+
+      info = refreshed
+      targetIdsToDetach.add(info.targetId)
+      await this.cdp.Browser.closeTab({ targetId: info.targetId })
+    }
+
     this.consoleCollector.detach(page)
     this.pages.delete(page)
-    this.sessions.delete(info.targetId)
+    for (const targetId of targetIdsToDetach) {
+      this.sessions.delete(targetId)
+    }
   }
 
   // --- Navigation ---
diff --git a/packages/browseros-agent/apps/server/tests/browser/browser.test.ts b/packages/browseros-agent/apps/server/tests/browser/browser.test.ts
new file mode 100644
index 000000000..9fb0aad4e
--- /dev/null
+++ b/packages/browseros-agent/apps/server/tests/browser/browser.test.ts
@@ -0,0 +1,187 @@
+import { describe, it } from 'bun:test'
+import assert from 'node:assert'
+import type {
+  CloseTabParams,
+  GetTabInfoParams,
+  TabInfo,
+} from '@browseros/cdp-protocol/domains/browser'
+import type { ProtocolApi } from '@browseros/cdp-protocol/protocol-api'
+import type { CdpBackend } from '../../src/browser/backends/types'
+import { Browser } from '../../src/browser/browser'
+
+class FakeCdpBackend {
+  readonly closeTabCalls: CloseTabParams[] = []
+  private nextSessionId = 1
+  private readonly protocolSessions = new Map<string, ProtocolApi>()
+  tabs: TabInfo[]
+
+  Browser = {
+    getTabs: async () => ({ tabs: this.tabs }),
+    getTabInfo: async (params: GetTabInfoParams) => {
+      const tab = this.tabs.find(
+        (t) => t.tabId === params.tabId || t.targetId === params.targetId,
+      )
+      if (!tab) throw new Error('Unknown page')
+      return { tab }
+    },
+    closeTab: async (params: CloseTabParams) => {
+      this.closeTabCalls.push(params)
+      const index = this.tabs.findIndex(
+        (t) => t.tabId === params.tabId || t.targetId === params.targetId,
+      )
+      if (index === -1) throw new Error('Unknown page')
+      this.tabs.splice(index, 1)
+    },
+  }
+
+  Target = {
+    on: () => () => {},
+    attachToTarget: async () => {
+      const sessionId = `session-${this.nextSessionId++}`
+      this.protocolSessions.set(sessionId, createProtocolSession())
+      return { sessionId }
+    },
+  }
+
+  constructor(tabs: TabInfo[]) {
+    this.tabs = tabs
+  }
+
+  async connect(): Promise<void> {}
+  async disconnect(): Promise<void> {}
+  isConnected(): boolean {
+    return true
+  }
+  async getTargets(): Promise<[]> {
+    return []
+  }
+  session(sessionId: string): ProtocolApi {
+    const session = this.protocolSessions.get(sessionId)
+    if (!session) throw new Error(`Unknown session ${sessionId}`)
+    return session
+  }
+  onSessionEvent(): () => void {
+    return () => {}
+  }
+}
+
+function createProtocolSession(): ProtocolApi {
+  return {
+    Page: { enable: async () => {} },
+    DOM: { enable: async () => {} },
+    Runtime: { enable: async () => {} },
+    Log: { enable: async () => {} },
+    Accessibility: { enable: async () => {} },
+  } as unknown as ProtocolApi
+}
+
+function createTab(overrides: Partial<TabInfo>): TabInfo {
+  return {
+    tabId: 101,
+    targetId: 'target-101',
+    url: 'https://example.com',
+    title: 'Example',
+    isActive: false,
+    isLoading: false,
+    loadProgress: 1,
+    isPinned: false,
+    isHidden: false,
+    windowId: 1,
+    index: 0,
+    ...overrides,
+  }
+}
+
+function createBrowser(tabs: TabInfo[]): {
+  browser: Browser
+  cdp: FakeCdpBackend
+} {
+  const cdp = new FakeCdpBackend(tabs)
+  return {
+    browser: new Browser(cdp as unknown as CdpBackend),
+    cdp,
+  }
+}
+
+function getSessionCache(browser: Browser): Map<string, string> {
+  return (browser as unknown as { sessions: Map<string, string> }).sessions
+}
+
+async function attachSession(
+  browser: Browser,
+  targetId: string,
+  pageId: number,
+): Promise<void> {
+  await (
+    browser as unknown as {
+      attachToPage(targetId: string, pageId: number): Promise<string>
+    }
+  ).attachToPage(targetId, pageId)
+}
+
+describe('Browser', () => {
+  it('closes listed pages by target ID', async () => {
+    const { browser, cdp } = createBrowser([
+      createTab({ tabId: 401, targetId: 'target-401' }),
+    ])
+
+    const pages = await browser.listPages()
+    assert.strictEqual(pages.length, 1)
+
+    await browser.closePage(pages[0].pageId)
+
+    assert.deepStrictEqual(cdp.closeTabCalls, [{ targetId: 'target-401' }])
+    assert.strictEqual(cdp.tabs.length, 0)
+  })
+
+  it('refreshes pages before treating closePage page IDs as unknown', async () => {
+    const { browser, cdp } = createBrowser([
+      createTab({ tabId: 402, targetId: 'target-402' }),
+    ])
+
+    await browser.closePage(1)
+
+    assert.deepStrictEqual(cdp.closeTabCalls, [{ targetId: 'target-402' }])
+    assert.strictEqual(cdp.tabs.length, 0)
+  })
+
+  it('retries closePage when the tab target changes before close', async () => {
+    const { browser, cdp } = createBrowser([
+      createTab({ tabId: 403, targetId: 'target-403-old' }),
+    ])
+
+    const pages = await browser.listPages()
+    cdp.tabs[0].targetId = 'target-403-new'
+
+    await browser.closePage(pages[0].pageId)
+
+    assert.deepStrictEqual(cdp.closeTabCalls, [
+      { targetId: 'target-403-old' },
+      { targetId: 'target-403-new' },
+    ])
+    assert.strictEqual(cdp.tabs.length, 0)
+  })
+
+  it('clears stale session cache when closePage retries with a refreshed target ID', async () => {
+    const { browser, cdp } = createBrowser([
+      createTab({ tabId: 404, targetId: 'target-404-old' }),
+    ])
+
+    const pages = await browser.listPages()
+    await attachSession(browser, 'target-404-old', pages[0].pageId)
+    assert.deepStrictEqual(
+      [...getSessionCache(browser).keys()],
+      ['target-404-old'],
+    )
+
+    cdp.tabs[0].targetId = 'target-404-new'
+
+    await browser.closePage(pages[0].pageId)
+
+    assert.deepStrictEqual(cdp.closeTabCalls, [
+      { targetId: 'target-404-old' },
+      { targetId: 'target-404-new' },
+    ])
+    assert.deepStrictEqual([...getSessionCache(browser).keys()], [])
+  })
+})