diff --git a/src/main/dock/unread-badge.ts b/src/main/dock/unread-badge.ts
new file mode 100644
index 000000000..e97860228
--- /dev/null
+++ b/src/main/dock/unread-badge.ts
@@ -0,0 +1,14 @@
+import { app } from 'electron'
+
+export function setUnreadDockBadgeCount(count: number): void {
+  if (process.platform !== 'darwin') {
+    return
+  }
+
+  const normalizedCount = Number.isFinite(count) ? Math.max(0, Math.trunc(count)) : 0
+  const label = normalizedCount === 0 ? '' : normalizedCount > 99 ? '99+' : String(normalizedCount)
+
+  // Why: unread counts belong on the native Dock tile on macOS.
+  // Windows/Linux are skipped until we define the right platform behavior.
+  app.dock?.setBadge(label)
+}
diff --git a/src/main/index.ts b/src/main/index.ts
index 354b35fe2..ac53966d0 100644
--- a/src/main/index.ts
+++ b/src/main/index.ts
@@ -51,6 +51,7 @@ import { cursorHookService } from './cursor/hook-service'
 import { getPtyIdForPaneKey, registerPaneKeyTeardownListener, getLocalPtyProvider } from './ipc/pty'
 import { AgentBrowserBridge } from './browser/agent-browser-bridge'
 import { browserManager } from './browser/browser-manager'
+import { setUnreadDockBadgeCount } from './dock/unread-badge'
 
 let mainWindow: BrowserWindow | null = null
 /** Whether a manual app.quit() (Cmd+Q, etc.) is in progress. Shared with the
@@ -659,6 +660,7 @@ app.on('will-quit', (e) => {
   // so without this ordering, running agents would produce orphaned
   // agent_start events with no matching stops.
   starNag?.stop()
+  setUnreadDockBadgeCount(0)
   agentHookServer.stop()
   stats?.flush()
   // Why: agent-browser daemon processes would otherwise linger after Orca quits,
diff --git a/src/main/ipc/app.ts b/src/main/ipc/app.ts
index da5d57cd9..f283d428a 100644
--- a/src/main/ipc/app.ts
+++ b/src/main/ipc/app.ts
@@ -3,6 +3,7 @@ import { promisify } from 'node:util'
 import { app, ipcMain } from 'electron'
 import { isPwshAvailable } from '../pwsh'
 import { isWslAvailable } from '../wsl'
+import { setUnreadDockBadgeCount } from '../dock/unread-badge'
 
 const execFileAsync = promisify(execFile)
 
@@ -66,4 +67,8 @@ export function registerAppHandlers(): void {
       app.exit(0)
     }, 150)
   })
+
+  ipcMain.handle('app:setUnreadDockBadgeCount', (_event, count: number) => {
+    setUnreadDockBadgeCount(Number.isFinite(count) ? count : 0)
+  })
 }
diff --git a/src/preload/api-types.ts b/src/preload/api-types.ts
index f41144e0c..bcb0c2143 100644
--- a/src/preload/api-types.ts
+++ b/src/preload/api-types.ts
@@ -361,6 +361,8 @@ export type AppApi = {
    *  US QWERTY but whose Option layer composes characters (issue #1205).
    *  Returns null on non-Darwin platforms or when the defaults read fails. */
   getKeyboardInputSourceId: () => Promise<string | null>
+  /** Updates the macOS Dock unread badge. No-op on Windows/Linux. */
+  setUnreadDockBadgeCount: (count: number) => Promise<void>
 }
 
 export type PreloadApi = {
diff --git a/src/preload/index.ts b/src/preload/index.ts
index 45a81564f..a72438a29 100644
--- a/src/preload/index.ts
+++ b/src/preload/index.ts
@@ -252,7 +252,9 @@ const api = {
     // src/renderer/src/lib/keyboard-layout/input-source-id.ts, issue #1205).
     // Returns null on non-Darwin or when the defaults read fails.
     getKeyboardInputSourceId: (): Promise<string | null> =>
-      ipcRenderer.invoke('app:getKeyboardInputSourceId')
+      ipcRenderer.invoke('app:getKeyboardInputSourceId'),
+    setUnreadDockBadgeCount: (count: number): Promise<void> =>
+      ipcRenderer.invoke('app:setUnreadDockBadgeCount', count)
   },
 
   wsl: {
diff --git a/src/renderer/src/App.tsx b/src/renderer/src/App.tsx
index 5d1efdf4e..f8bdda416 100644
--- a/src/renderer/src/App.tsx
+++ b/src/renderer/src/App.tsx
@@ -36,6 +36,7 @@ import { SshPassphraseDialog } from './components/settings/SshPassphraseDialog'
 import { useGitStatusPolling } from './components/right-sidebar/useGitStatusPolling'
 import { useEditorExternalWatch } from './hooks/useEditorExternalWatch'
 import { useAutoAckViewedAgent } from './hooks/useAutoAckViewedAgent'
+import { useUnreadDockBadge } from './hooks/useUnreadDockBadge'
 import {
   setRuntimeGraphStoreStateGetter,
   setRuntimeGraphSyncEnabled
@@ -139,6 +140,8 @@ const PetOverlay = lazy(() => import('./components/pet/PetOverlay'))
 const OnboardingFlow = lazy(() => import('./components/onboarding/OnboardingFlow'))
 
 function App(): React.JSX.Element {
+  useUnreadDockBadge()
+
   // Why: Zustand actions are referentially stable, but each individual
   // useAppStore(s => s.someAction) still registers a subscription that React
   // must check on every store mutation. Consolidating 19 action refs into one
diff --git a/src/renderer/src/hooks/useUnreadDockBadge.ts b/src/renderer/src/hooks/useUnreadDockBadge.ts
new file mode 100644
index 000000000..1f6674a98
--- /dev/null
+++ b/src/renderer/src/hooks/useUnreadDockBadge.ts
@@ -0,0 +1,25 @@
+import { useEffect } from 'react'
+import { getUnreadBadgeCount } from '@/lib/unread-badge-count'
+import { useAppStore } from '@/store'
+
+export function useUnreadDockBadge(): void {
+  const unreadCount = useAppStore((state) =>
+    getUnreadBadgeCount({
+      worktreesByRepo: state.worktreesByRepo,
+      tabsByWorktree: state.tabsByWorktree,
+      unreadTerminalTabs: state.unreadTerminalTabs
+    })
+  )
+
+  useEffect(() => {
+    void window.api.app.setUnreadDockBadgeCount(unreadCount).catch(() => {
+      // Dock sync is best-effort chrome; stale badge state should not affect app use.
+    })
+  }, [unreadCount])
+
+  useEffect(() => {
+    return () => {
+      void window.api.app.setUnreadDockBadgeCount(0).catch(() => {})
+    }
+  }, [])
+}
diff --git a/src/renderer/src/lib/unread-badge-count.test.ts b/src/renderer/src/lib/unread-badge-count.test.ts
new file mode 100644
index 000000000..fdf20dfab
--- /dev/null
+++ b/src/renderer/src/lib/unread-badge-count.test.ts
@@ -0,0 +1,43 @@
+import { describe, expect, it } from 'vitest'
+import type { TerminalTab, Worktree } from '../../../shared/types'
+import { getUnreadBadgeCount } from './unread-badge-count'
+
+function worktree(id: string, isUnread: boolean): Worktree {
+  return { id, isUnread } as Worktree
+}
+
+function tab(id: string): TerminalTab {
+  return { id } as TerminalTab
+}
+
+describe('getUnreadBadgeCount', () => {
+  it('counts unread worktrees', () => {
+    expect(
+      getUnreadBadgeCount({
+        worktreesByRepo: { repo: [worktree('wt-1', true), worktree('wt-2', false)] },
+        tabsByWorktree: {},
+        unreadTerminalTabs: {}
+      })
+    ).toBe(1)
+  })
+
+  it('dedupes unread terminal tabs against their worktree', () => {
+    expect(
+      getUnreadBadgeCount({
+        worktreesByRepo: { repo: [worktree('wt-1', true)] },
+        tabsByWorktree: { 'wt-1': [tab('tab-1'), tab('tab-2')] },
+        unreadTerminalTabs: { 'tab-1': true, 'tab-2': true }
+      })
+    ).toBe(1)
+  })
+
+  it('counts tab-only unread activity by owning worktree', () => {
+    expect(
+      getUnreadBadgeCount({
+        worktreesByRepo: { repo: [worktree('wt-1', false), worktree('wt-2', false)] },
+        tabsByWorktree: { 'wt-1': [tab('tab-1')], 'wt-2': [tab('tab-2')] },
+        unreadTerminalTabs: { 'tab-1': true, 'tab-2': true }
+      })
+    ).toBe(2)
+  })
+})
diff --git a/src/renderer/src/lib/unread-badge-count.ts b/src/renderer/src/lib/unread-badge-count.ts
new file mode 100644
index 000000000..79cd2ffa3
--- /dev/null
+++ b/src/renderer/src/lib/unread-badge-count.ts
@@ -0,0 +1,39 @@
+import type { TerminalTab, Worktree } from '../../../shared/types'
+
+export function getUnreadBadgeCount({
+  worktreesByRepo,
+  tabsByWorktree,
+  unreadTerminalTabs
+}: {
+  worktreesByRepo: Record<string, Worktree[]>
+  tabsByWorktree: Record<string, TerminalTab[]>
+  unreadTerminalTabs: Record<string, true>
+}): number {
+  const unreadWorktreeIds = new Set<string>()
+
+  for (const worktrees of Object.values(worktreesByRepo)) {
+    for (const worktree of worktrees) {
+      if (worktree.isUnread) {
+        unreadWorktreeIds.add(worktree.id)
+      }
+    }
+  }
+
+  const unreadTabIds = new Set(Object.keys(unreadTerminalTabs))
+  if (unreadTabIds.size === 0) {
+    return unreadWorktreeIds.size
+  }
+
+  for (const [worktreeId, tabs] of Object.entries(tabsByWorktree)) {
+    for (const tab of tabs) {
+      if (!unreadTabIds.delete(tab.id)) {
+        continue
+      }
+      unreadWorktreeIds.add(worktreeId)
+    }
+  }
+
+  // Why: tab unread state should normally map to a live worktree, but counting
+  // unmatched entries keeps the Dock badge honest during hydration races.
+  return unreadWorktreeIds.size + unreadTabIds.size
+}