GitHub Copilot app frequently hangs without any feedback or timeouts due to "coordination" failures

Logs .zip

Cross-session message reports success, but parent does not resume; completed child remains “Running”

Summary

In the GitHub Copilot app on Windows, a child session sent a completion message to its parent and the send operation reported success. The parent did not record the corresponding incoming message or resume work. Progress stalled for several hours until the user manually prompted the parent.

A separate completed child continued to appear Running, despite its event log recording task completion and turn termination.

Observed interaction sequence

1. A parent session delegated work to child sessions.

2. The parent ended its current turn while awaiting a child’s result.

3. The child sent its result through send_session_message; the tool reported success.

4. The child completed its task and ended its turn.

5. The parent did not consume the result or continue automatically.

This is one observed incident; deterministic reproduction has not been established.

Evidence timeline

September 9, 2026, Pacific time (UTC−7):

Time	Event
15:21:22	Parent recorded assistant.turn_end.
15:22:13	Child called send_session_message targeting the parent; tool.execution_complete reported success.
15:22:18	Child recorded session.task_complete and assistant.turn_end.
15:21:22–20:45:22	Parent recorded no events: 5 hours 24 minutes without activity. No incoming handoff appeared around 15:22:13.
20:45:22–20:45:59	Parent recorded model instrumentation, but no tool execution or workflow progress followed.
20:55:15	User manually prompted the parent about the hang.
20:55:33	Parent tool execution resumed.

Separately, another child recorded completion at 13:08:24, but the app’s session-status snapshot still reported it as running during recovery.

Expected behavior

• A successful cross-session send is durably delivered and schedules recipient processing when appropriate.

• A completed child transitions to an accurate idle/completed status.

• Delivery or resumption failures are surfaced rather than leaving the workflow apparently running indefinitely.

Actual behavior and impact

The sender acknowledged success, but no corresponding recipient event or continuation was recorded. The app also exposed stale running state. Autonomous coordination stopped without an actionable error.

At recovery, there were no active build/release shells or pending approval/input requests. Completed work remained intact.

Investigation boundary

The evidence narrows the failure to handoff delivery/resumption and session-state synchronization. It does not establish whether the defect was message persistence, queue dispatch, recipient wake-up, completion notification handling, or another runtime component. Send acknowledgement alone did not demonstrate recipient consumption.

Start by reviewing the linked logs and tracing the send_session_message sequence from the child to the parent, including the recorded session-status snapshots. Confirm whether successful handoffs are delivered and resume the recipient, whether completed children become idle or completed, and whether failures surface instead of hanging indefinitely.