openclaw - 💡(How to fix) Fix Bug: sessions_yield wakes parent with yield continuation instead of child completion event

Environment

• OpenClaw version: v2026.5.19
• Model: deepseek-v4-pro
• Agent: coder (using sessions_spawn + sessions_yield to delegate to subagent)

Symptoms

When a parent agent calls sessions_spawn → sessions_yield to wait for a child subagent, and the child completes, the parent never receives a completion notification. The parent is only awakened by a timer-based yield continuation, sees the old yield context ("waiting for child"), assumes the child is still running, and stops — never processing the completion.

The child subagent's work is fully successful, but the parent never learns about it.

Evidence

Parent transcript (c10a8206-5248-4089-9c09-623895716f40.jsonl)

[05:25:26] sessions_spawn → child c329eb41 created
[05:25:34] sessions_yield → "status": "yielded"
[05:25:34] custom_message: openclaw.sessions_yield (yield note)
                                           ← 6 minutes of nothing
[05:31:25] assistant: "子 agent 正在执行，等待完成通知。" → stop
           ↑ parentId = yield note (62054bbe)
           ↑ No child completion event between yield and this

Child transcript (cd255cda-0103-45bf-b25f-98e3e65c6091.jsonl)

[05:26:23] 6 tool + 2 feature directories deleted
[05:29:08] src/index.ts rewritten (imports + registrations removed)
[05:30:48] npm run build ✅
[05:30:58] npx tsc --noEmit ✅
[05:31:02] todo-4 → completed  ← ALL WORK DONE
[05:31:14] "All done. Here's the summary..."  ← LAST MESSAGE

Gateway log (openclaw-2026-05-21.log) — 13:31:00–13:31:26 CST

13:31:02  [lcm] child afterTurn (todo-4 completed, persisted)
13:31:15  ⇄ res ✓ agent.wait 349006ms  ← timer-based return, NO payload
13:31:15  [lcm] child afterTurnTranscriptReconcile (last child turn)
13:31:16  "All done. Here's the summary..." (console.log — NOT a dispatch)
13:31:18  persona-bootstrap → agent:coder:main  ← parent session restarts
13:31:18  [lcm] parent bootstrap + assemble (restores yield context)
13:31:26  "子 agent 正在执行，等待完成通知。" → stop

Root Cause

The Gateway does not dispatch child completion events to a yielded parent period.

There is no subagent_announce, deliverToRequester, wakeParent, or any similar event anywhere in the gateway log. A full-text search of the entire 7438-line log file confirmed zero matches for any child→parent completion delivery mechanism.

The two lifecycles are fully decoupled in the Gateway:

Child:  work completes → session end (status=done) → LCM persist → END
                                                      ↑
                                                      No event dispatched to parent
                                                      
Parent: sessions_yield → agent.wait(timer) → timer fires → return bare
                                                              ↓
                                                     LCM restore yield context
                                                              ↓
                                                     Model sees "still waiting" → stop

The agent.wait call (L5816) returned after 349,006ms with no payload whatsoever — it is purely a timer-based yield continuation, not triggered by child completion.

Expected Behavior

When a child session completes while the parent is yielded via sessions_yield:

1. The Gateway should dispatch a child completion event to the parent
2. This event should wake the parent from the yielded state
3. The parent transcript should contain the child's completion summary or metadata
4. The parent can then process completion, verify results, and respond to the user

Affected Sessions

Impact

• Parent agent never learns child work is complete → no verification, no result reporting to user
• User sees incomplete response ("still waiting")
• All child work is actually correct and complete — no data loss, but UX is broken
• sessions_spawn + sessions_yield cannot be used to reliably wait for child completion