fix(tmux-subagent): track pane without blocking on session readiness

waitForSessionReady polled session.status for up to 10s before the pane was registered, but session.status only becomes visible after promptAsync starts. Blocking pane tracking on that signal caused the attach client to see an empty session and render a blank TUI.

Track the pane immediately after spawn, and run the readiness probe in the background purely for observability.

Ultraworked with [Sisyphus](https://github.com/code-yeongyu/oh-my-openagent)

Co-authored-by: Sisyphus <clio-agent@sisyphuslabs.ai>

src/features/tmux-subagent/manager.test.ts

@@ -1056,6 +1056,27 @@ describe('TmuxSessionManager', () => {
         logSpy.mockRestore()
       })
     })
+
+    test('#given session.status never reports session ready #when onSessionCreated runs #then pane is tracked immediately without blocking', async () => {
+      // given
+      mockIsInsideTmux.mockReturnValue(true)
+      mockQueryWindowState.mockImplementation(async () => createWindowState())
+
+      const { TmuxSessionManager } = await import('./manager')
+      const ctx = createMockContext({ sessionStatusResult: { data: {} } })
+      const config = createTmuxConfig({ enabled: true })
+      const manager = new TmuxSessionManager(ctx, config, mockTmuxDeps)
+      const event = createSessionCreatedEvent('ses_fast_track', 'ses_parent', 'Fast Track')
+
+      // when
+      const start = Date.now()
+      await manager.onSessionCreated(event)
+      const elapsed = Date.now() - start
+
+      // then
+      expect(elapsed < 500).toBe(true)
+      expect(getTrackedSessions(manager).has('ses_fast_track')).toBe(true)
+    })
   })
 
   describe('onSessionDeleted', () => {

src/features/tmux-subagent/manager.ts

@@ -511,7 +511,6 @@ export class TmuxSessionManager {
     if (deferred.retryIsolatedContainer) {
       const isolatedPaneId = await this.spawnInIsolatedContainer(sessionId, deferred.title)
       if (isolatedPaneId) {
-        const sessionReady = await this.waitForSessionReady(sessionId)
         this.sessions.set(
           sessionId,
           createTrackedSession({
@@ -525,8 +524,8 @@ export class TmuxSessionManager {
         log("[tmux-session-manager] deferred session attached in isolated window", {
           sessionId,
           paneId: isolatedPaneId,
-          sessionReady,
         })
+        this.logSessionReadinessInBackground(sessionId)
         return
       }
     }
@@ -585,14 +584,6 @@ export class TmuxSessionManager {
       return
     }
 
-    const sessionReady = await this.waitForSessionReady(sessionId)
-    if (!sessionReady) {
-      log("[tmux-session-manager] deferred session not ready after timeout", {
-        sessionId,
-        paneId: result.spawnedPaneId,
-      })
-    }
-
     this.sessions.set(
       sessionId,
       createTrackedSession({
@@ -606,18 +597,27 @@ export class TmuxSessionManager {
     log("[tmux-session-manager] deferred session attached", {
       sessionId,
       paneId: result.spawnedPaneId,
-      sessionReady,
+    })
+    this.logSessionReadinessInBackground(sessionId)
+  }
+
+  private logSessionReadinessInBackground(sessionId: string): void {
+    void this.waitForSessionReady(sessionId).catch((error) => {
+      log("[tmux-session-manager] background readiness probe failed", {
+        sessionId,
+        error: String(error),
+      })
     })
   }
 
   private async waitForSessionReady(sessionId: string): Promise<boolean> {
     const startTime = Date.now()
-    
+
     while (Date.now() - startTime < SESSION_READY_TIMEOUT_MS) {
       try {
         const statusResult = await this.client.session.status({ path: undefined })
         const allStatuses = normalizeSDKResponse(statusResult, {} as Record<string, { type: string }>)
-        
+
         if (allStatuses[sessionId]) {
           log("[tmux-session-manager] session ready", {
             sessionId,
@@ -629,10 +629,10 @@ export class TmuxSessionManager {
       } catch (err) {
         log("[tmux-session-manager] session status check error", { error: String(err) })
       }
-      
+
       await new Promise((resolve) => setTimeout(resolve, SESSION_READY_POLL_INTERVAL_MS))
     }
-    
+
     log("[tmux-session-manager] session ready timeout", {
       sessionId,
       timeoutMs: SESSION_READY_TIMEOUT_MS,
@@ -682,7 +682,6 @@ export class TmuxSessionManager {
       try {
         const isolatedPaneId = await this.spawnInIsolatedContainer(sessionId, title)
         if (isolatedPaneId) {
-          const sessionReady = await this.waitForSessionReady(sessionId)
           this.sessions.set(
             sessionId,
             createTrackedSession({ sessionId, paneId: isolatedPaneId, description: title }),
@@ -691,8 +690,8 @@ export class TmuxSessionManager {
           log("[tmux-session-manager] first subagent spawned in isolated window", {
             sessionId,
             paneId: isolatedPaneId,
-            sessionReady,
           })
+          this.logSessionReadinessInBackground(sessionId)
           return
         }
 
@@ -773,15 +772,6 @@ export class TmuxSessionManager {
         }
 
         if (result.success && result.spawnedPaneId) {
-          const sessionReady = await this.waitForSessionReady(sessionId)
-
-          if (!sessionReady) {
-            log("[tmux-session-manager] session not ready after timeout, tracking anyway", {
-              sessionId,
-              paneId: result.spawnedPaneId,
-            })
-          }
-
           this.sessions.set(
             sessionId,
             createTrackedSession({
@@ -793,9 +783,9 @@ export class TmuxSessionManager {
           log("[tmux-session-manager] pane spawned and tracked", {
             sessionId,
             paneId: result.spawnedPaneId,
-            sessionReady,
           })
           this.pollingManager.startPolling()
+          this.logSessionReadinessInBackground(sessionId)
         } else {
           log("[tmux-session-manager] spawn failed", {
             success: result.success,