fix(terminal): publish daemon sessions before output

config/reliability-gates.jsonc

@@ -3687,7 +3687,8 @@
           "assertions": [
             "a reused live daemon session rejects attach and kill from a replacement pane identity",
             "native immediate force-kill failure preserves the live daemon session for retry",
-            "same-id create waits for physical exit proof without disposing the terminating session owner"
+            "same-id create waits for physical exit proof without disposing the terminating session owner",
+            "the host publishes Session ownership and attaches its client before buffered data and exit flush synchronously on subscription"
           ]
         },
         {
@@ -4193,6 +4194,15 @@
           "result": "passed",
           "durationSeconds": 10.49,
           "summary": "1800 tests passed with exact same-id startup replay admission, retained pre-handler/liveness bounds, and cross-provider retry identity preserved."
+        },
+        {
+          "date": "2026-07-12",
+          "runner": "local",
+          "platform": "macos",
+          "command": "pnpm exec vitest run --config config/vitest.config.ts src/main/providers/local-pty-provider.test.ts src/main/daemon/daemon-pty-adapter.test.ts src/main/daemon/daemon-pty-router.test.ts src/main/daemon/degraded-daemon-pty-provider.test.ts src/main/daemon/session.test.ts src/main/daemon/pty-subprocess.test.ts src/main/daemon/terminal-host.test.ts src/main/daemon/terminal-host-session-reaping-leak.test.ts src/main/daemon/daemon-server.test.ts src/main/ipc/pty.test.ts src/main/ipc/runtime-terminal-close-retry-owner.test.ts src/main/runtime/orca-runtime.test.ts",
+          "result": "passed",
+          "durationSeconds": 9.06,
+          "summary": "1443 tests passed: two-phase Session startup delivered synchronous buffered BOOT output and exit to the published owner/client, reaped the exact map entry, and allowed a clean same-ID replacement."
         }
       ],
       "runtimeBudget": {

src/main/daemon/session.ts

@@ -93,6 +93,9 @@ export type SessionOptions = {
   shellReadyTimeoutMs?: number
   historySeed?: string
   scrollback?: number
+  // Why: TerminalHost must publish the Session and attach its first client
+  // before node-pty flushes buffered data/exit synchronously on subscription.
+  deferSubprocessSubscription?: boolean
   // Why: fired once the session reaches a terminal state (natural exit or
   // kill-timeout force-dispose) so the owner (TerminalHost) can reap it —
   // dispose the headless emulator and drop it from its session map. Without a
@@ -141,6 +144,7 @@ export class Session {
   private readonly _historySeeded: boolean | undefined
   private readonly exitProofPromise: Promise<void>
   private resolveExitProof!: () => void
+  private subprocessSubscriptionStarted = false
 
   constructor(opts: SessionOptions) {
     this.sessionId = opts.sessionId
@@ -179,6 +183,16 @@ export class Session {
     }
 
     this.postReadyFlushGate = new PostReadyFlushGate(() => this.flushPreReadyQueue())
+    if (!opts.deferSubprocessSubscription) {
+      this.startSubprocessSubscription()
+    }
+  }
+
+  startSubprocessSubscription(): void {
+    if (this.subprocessSubscriptionStarted) {
+      return
+    }
+    this.subprocessSubscriptionStarted = true
     this.subprocess.onData((data) => this.handleSubprocessData(data))
     this.subprocess.onExit((code) => this.handleSubprocessExit(code))
   }

src/main/daemon/terminal-host.test.ts

@@ -156,6 +156,41 @@ describe('TerminalHost', () => {
       expect(spawnFn).toHaveBeenCalledTimes(2)
     })
 
+    it('publishes ownership before buffered data and exit flush on subscription', async () => {
+      const buffered = createMockSubprocess()
+      buffered.onData = vi.fn((callback) => callback('BOOT'))
+      buffered.onExit = vi.fn((callback) => callback(0))
+      const replacement = createMockSubprocess()
+      spawnFn = vi.fn().mockReturnValueOnce(buffered).mockReturnValue(replacement)
+      host.dispose()
+      host = new TerminalHost({ spawnSubprocess: spawnFn as MockSpawnFn })
+      const onData = vi.fn()
+      const onExit = vi.fn()
+
+      const first = await host.createOrAttach({
+        sessionId: 'session-1',
+        cols: 80,
+        rows: 24,
+        streamClient: { onData, onExit }
+      })
+
+      expect(first).toMatchObject({ isNew: true, snapshot: null })
+      expect(onData).toHaveBeenCalledWith('BOOT')
+      expect(onExit).toHaveBeenCalledWith(0, first.sessionGeneration)
+      expect(host.listSessions()).toHaveLength(0)
+
+      await expect(
+        host.createOrAttach({
+          sessionId: 'session-1',
+          cols: 80,
+          rows: 24,
+          streamClient: { onData: vi.fn(), onExit: vi.fn() }
+        })
+      ).resolves.toMatchObject({ isNew: true })
+      expect(host.listSessions()).toHaveLength(1)
+      expect(spawnFn).toHaveBeenCalledTimes(2)
+    })
+
     it('returns snapshot when attaching to existing session', async () => {
       await host.createOrAttach({
         sessionId: 'session-1',

src/main/daemon/terminal-host.ts

@@ -136,6 +136,7 @@ export class TerminalHost {
       subprocess,
       shellReadySupported,
       historySeed: opts.historySeed,
+      deferSubprocessSubscription: true,
       // Why: reap the dead session (dispose emulator + drop from the map) the
       // moment its subprocess exits, instead of retaining it for the daemon's
       // lifetime. Nothing reads a dead session's emulator (getSnapshot/
@@ -149,6 +150,7 @@ export class TerminalHost {
     this.sessions.set(opts.sessionId, session)
 
     const token = session.attachClient(opts.streamClient)
+    session.startSubprocessSubscription()
 
     if (opts.command && !subprocess.startupCommandDeliveredInShellArgs) {
       // Why: startup commands must run inside the long-lived interactive shell