feat(tui): append git branch to cwd label in status bar

Adds useGitBranch hook (async, cached, 15s TTL) and fmtCwdBranch
helper so the footer shows `~/repo (main)` instead of just `~/repo`.
Degrades silently when git is unavailable or cwd is outside a repo.

Partial fix for #12267 (TUI portion; #12277 covers the Python side).

ui-tui/src/__tests__/paths.test.ts

@@ -0,0 +1,70 @@
+import { afterEach, beforeEach, describe, expect, it } from 'vitest'
+
+import { fmtCwdBranch, shortCwd } from '../domain/paths.js'
+
+describe('shortCwd', () => {
+  const origHome = process.env.HOME
+
+  beforeEach(() => {
+    process.env.HOME = '/Users/bb'
+  })
+
+  afterEach(() => {
+    process.env.HOME = origHome
+  })
+
+  it('collapses HOME to ~', () => {
+    expect(shortCwd('/Users/bb/proj/repo')).toBe('~/proj/repo')
+  })
+
+  it('leaves non-HOME paths alone', () => {
+    expect(shortCwd('/tmp/work')).toBe('/tmp/work')
+  })
+
+  it('truncates long paths from the left with ellipsis', () => {
+    const out = shortCwd('/var/long/deeply/nested/workspace/here', 10)
+    expect(out.startsWith('…')).toBe(true)
+    expect(out.length).toBe(10)
+    expect('/var/long/deeply/nested/workspace/here'.endsWith(out.slice(1))).toBe(true)
+  })
+
+  it('keeps paths shorter than max intact', () => {
+    expect(shortCwd('/a/b', 10)).toBe('/a/b')
+  })
+})
+
+describe('fmtCwdBranch', () => {
+  const origHome = process.env.HOME
+
+  beforeEach(() => {
+    process.env.HOME = '/Users/bb'
+  })
+
+  afterEach(() => {
+    process.env.HOME = origHome
+  })
+
+  it('returns bare cwd when branch is null', () => {
+    expect(fmtCwdBranch('/Users/bb/proj', null)).toBe('~/proj')
+  })
+
+  it('returns bare cwd when branch is empty', () => {
+    expect(fmtCwdBranch('/Users/bb/proj', '')).toBe('~/proj')
+  })
+
+  it('appends branch in parens', () => {
+    expect(fmtCwdBranch('/Users/bb/proj', 'main')).toBe('~/proj (main)')
+  })
+
+  it('truncates the path to keep the branch tag readable', () => {
+    const out = fmtCwdBranch('/Users/bb/very/deeply/nested/project/folder', 'feature-branch', 30)
+    expect(out).toMatch(/ \(feature-branch\)$/)
+    expect(out.length).toBeLessThanOrEqual(30)
+  })
+
+  it('truncates very long branch names from the right', () => {
+    const out = fmtCwdBranch('/Users/bb/p', 'a-very-long-feature-branch-name')
+    expect(out).toMatch(/^~\/p \(…/)
+    expect(out).toContain(')')
+  })
+})

ui-tui/src/app/useMainApp.ts

@@ -5,7 +5,7 @@ import { useCallback, useEffect, useMemo, useRef, useState } from 'react'
 import { STARTUP_RESUME_ID } from '../config/env.js'
 import { MAX_HISTORY, WHEEL_SCROLL_STEP } from '../config/limits.js'
 import { imageTokenMeta } from '../domain/messages.js'
-import { shortCwd } from '../domain/paths.js'
+import { fmtCwdBranch } from '../domain/paths.js'
 import { type GatewayClient } from '../gatewayClient.js'
 import type {
   ClarifyRespondResponse,
@@ -13,6 +13,7 @@ import type {
   GatewayEvent,
   TerminalResizeResponse
 } from '../gatewayTypes.js'
+import { useGitBranch } from '../hooks/useGitBranch.js'
 import { useVirtualHistory } from '../hooks/useVirtualHistory.js'
 import { asRpcResult, rpcErrorMessage } from '../lib/rpc.js'
 import { buildToolTrailLine, sameToolTrailGroup, toolTrailLabel } from '../lib/text.js'
@@ -620,9 +621,12 @@ export function useMainApp(gw: GatewayClient) {
     [turn, showProgressArea]
   )
 
+  const cwd = ui.info?.cwd || process.env.HERMES_CWD || process.cwd()
+  const gitBranch = useGitBranch(cwd)
+
   const appStatus = useMemo(
     () => ({
-      cwdLabel: shortCwd(ui.info?.cwd || process.env.HERMES_CWD || process.cwd()),
+      cwdLabel: fmtCwdBranch(cwd, gitBranch),
       goodVibesTick,
       sessionStartedAt: ui.sid ? sessionStartedAt : null,
       showStickyPrompt: !!stickyPrompt,
@@ -630,7 +634,7 @@ export function useMainApp(gw: GatewayClient) {
       stickyPrompt,
       voiceLabel: voiceRecording ? 'REC' : voiceProcessing ? 'STT' : `voice ${voiceEnabled ? 'on' : 'off'}`
     }),
-    [goodVibesTick, sessionStartedAt, stickyPrompt, ui, voiceEnabled, voiceProcessing, voiceRecording]
+    [cwd, gitBranch, goodVibesTick, sessionStartedAt, stickyPrompt, ui, voiceEnabled, voiceProcessing, voiceRecording]
   )
 
   const appTranscript = useMemo(

ui-tui/src/domain/paths.ts

@@ -4,3 +4,14 @@ export const shortCwd = (cwd: string, max = 28) => {
 
   return p.length <= max ? p : `…${p.slice(-(max - 1))}`
 }
+
+export const fmtCwdBranch = (cwd: string, branch: null | string, max = 40) => {
+  if (!branch) {
+    return shortCwd(cwd, max)
+  }
+
+  const b = branch.length > 16 ? `…${branch.slice(-15)}` : branch
+  const tag = ` (${b})`
+
+  return `${shortCwd(cwd, Math.max(8, max - tag.length))}${tag}`
+}

ui-tui/src/hooks/useGitBranch.ts

@@ -0,0 +1,72 @@
+import { execFile } from 'node:child_process'
+import { promisify } from 'node:util'
+
+import { useEffect, useState } from 'react'
+
+const TTL_MS = 15_000
+const TIMEOUT_MS = 500
+
+const pexec = promisify(execFile)
+const cache = new Map<string, { at: number; branch: null | string }>()
+const inflight = new Map<string, Promise<null | string>>()
+
+const resolveBranch = async (cwd: string): Promise<null | string> => {
+  try {
+    const { stdout } = await pexec('git', ['-C', cwd, 'rev-parse', '--abbrev-ref', 'HEAD'], { timeout: TIMEOUT_MS })
+    const b = stdout.trim()
+
+    return !b || b === 'HEAD' ? null : b
+  } catch {
+    return null
+  }
+}
+
+const fetchBranch = (cwd: string): Promise<null | string> => {
+  const pending = inflight.get(cwd)
+
+  if (pending) {
+    return pending
+  }
+
+  const p = resolveBranch(cwd).finally(() => inflight.delete(cwd))
+  inflight.set(cwd, p)
+
+  return p
+}
+
+export function useGitBranch(cwd: string): null | string {
+  const [branch, setBranch] = useState<null | string>(() => cache.get(cwd)?.branch ?? null)
+
+  useEffect(() => {
+    let cancelled = false
+
+    const tick = async () => {
+      const hit = cache.get(cwd)
+
+      if (hit && Date.now() - hit.at < TTL_MS) {
+        if (!cancelled) {
+          setBranch(hit.branch)
+        }
+
+        return
+      }
+
+      const b = await fetchBranch(cwd)
+      cache.set(cwd, { at: Date.now(), branch: b })
+
+      if (!cancelled) {
+        setBranch(b)
+      }
+    }
+
+    void tick()
+    const id = setInterval(() => void tick(), TTL_MS)
+
+    return () => {
+      cancelled = true
+      clearInterval(id)
+    }
+  }, [cwd])
+
+  return branch
+}