fix(issue): headless classifies child exit code 0 as 'exited unexpectedly' when no terminal notify observed (headless.js:780)

src/headless.ts

@@ -900,9 +900,14 @@ async function runHeadlessOnce(options: HeadlessOptions, restartCount: number):
   if (internalProcess) {
     internalProcess.on('exit', (code: number | null) => {
       if (!completed) {
-        const msg = `[headless] Child process exited unexpectedly with code ${code ?? 'null'}\n`
-        process.stderr.write(msg)
-        exitCode = EXIT_ERROR
+        if (code === 0) {
+          process.stderr.write('[headless] Child exited cleanly (code 0) without terminal notification\n')
+          exitCode = EXIT_SUCCESS
+        } else {
+          const msg = `[headless] Child process exited unexpectedly with code ${code ?? 'null'}\n`
+          process.stderr.write(msg)
+          exitCode = EXIT_ERROR
+        }
         resolveCompletion()
       }
     })

src/tests/headless-v2-migration.test.ts

@@ -170,6 +170,12 @@ function handleEvent(
   }
 }
 
+function handleChildExitWithoutTerminalNotification(code: number | null, state: EventHandlerState): void {
+  if (state.completed) return
+  state.completed = true
+  state.exitCode = code === 0 ? EXIT_SUCCESS : EXIT_ERROR
+}
+
 // ─── execution_complete event handling ──────────────────────────────────────
 
 test('execution_complete with status success triggers completion with EXIT_SUCCESS', () => {
@@ -224,6 +230,33 @@ test('execution_complete ignored if already completed', () => {
   assert.equal(state.exitCode, EXIT_SUCCESS)
 })
 
+test('clean child exit without terminal notification is treated as success', () => {
+  const state: EventHandlerState = { completed: false, blocked: false, exitCode: -1, v2Enabled: true }
+
+  handleChildExitWithoutTerminalNotification(0, state)
+
+  assert.equal(state.completed, true)
+  assert.equal(state.exitCode, EXIT_SUCCESS)
+})
+
+test('nonzero child exit without terminal notification remains an error', () => {
+  const state: EventHandlerState = { completed: false, blocked: false, exitCode: -1, v2Enabled: true }
+
+  handleChildExitWithoutTerminalNotification(1, state)
+
+  assert.equal(state.completed, true)
+  assert.equal(state.exitCode, EXIT_ERROR)
+})
+
+test('null child exit without terminal notification remains an error', () => {
+  const state: EventHandlerState = { completed: false, blocked: false, exitCode: -1, v2Enabled: true }
+
+  handleChildExitWithoutTerminalNotification(null, state)
+
+  assert.equal(state.completed, true)
+  assert.equal(state.exitCode, EXIT_ERROR)
+})
+
 // ─── v1 string-matching fallback ────────────────────────────────────────────
 
 test('v1 fallback: terminal notification still triggers completion', () => {