Issue 20348; before; main 8acbefefc5; Linux x86_64; real web dev server; collaborative Chromium 1280x800; Codex gpt-6.1-sol, same instance.
UI sequence: send parent request to delegate READY; wait for child READY and parent PARENT_DONE; Thread actions > Settle thread; open existing child in Lineage; send Reply exactly PONG.
UI result: child still Working without PONG.
('thread:project:b5c67249-dd52-4586-bfe6-3233c9ffb7b4:ed555ab9-25b6-4fcd-bc8c-a99ea22568cb', 'completed', '2026-10-22T01:32:00.801Z', '2026-10-22T01:32:20.465Z')
('thread:delegated-task:command%3Amcp%3A195a9786-15ef-4d3d-8008-f4c0e068d4f0%3Adelegate-task%3Aruntime-ready-once-20348', 'completed', '2026-10-22T01:32:13.896Z', '2026-10-22T01:32:17.700Z')
('thread:delegated-task:command%3Amcp%3A195a9786-15ef-4d3d-8008-f4c0e068d4f0%3Adelegate-task%3Aruntime-ready-once-20348', 'running', '2026-10-22T01:33:56.387Z', None)
[2026-10-22T01:32:02.504Z] thread/start thread=None
[2026-10-22T01:32:05.223Z] turn/start thread=01a1613c-9458-75d0-b321-693278d6f1d3
[2026-10-22T01:32:13.963Z] thread/start thread=None
[2026-10-22T01:32:14.720Z] turn/start thread=01a1613c-c122-7f03-a0ef-7c4f5b1ae19f
[2026-10-22T01:33:44.231Z] thread/unsubscribe thread=01a1613c-c122-7f03-a0ef-7c4f5b1ae19f
[2026-10-22T01:33:44.241Z] thread/unsubscribe thread=01a1613c-9458-75d0-b321-693278d6f1d3
[2026-10-22T01:33:56.546Z] turn/start thread=01a1613c-c122-7f03-a0ef-7c4f5b1ae19f
{"timestamp": "2026-10-22T01:32:17.662Z", "ordinal": 22, "type": "event_msg", "payload": {"type": "task_complete", "root_turn_id": "01a1613c-c404-7930-82e5-003f7876f1ae", "turn_id": "01a1613c-c404-7930-82e5-003f7876f1ae", "last_agent_message": "READY", "started_at": 1792632734, "completed_at": 1792632737, "duration_ms": 2933, "time_to_first_token_ms": 2812}}
{"timestamp": "2026-10-22T01:34:00.883Z", "ordinal": 32, "type": "event_msg", "payload": {"type": "task_complete", "root_turn_id": "01a1613e-51c9-7ee2-bc8c-e6e069013aaf", "turn_id": "01a1613e-51c9-7ee2-bc8c-e6e069013aaf", "last_agent_message": "PONG", "started_at": 1792632836, "completed_at": 1792632840, "duration_ms": 4310, "time_to_first_token_ms": 4053}}