subagent: completion event fires at first idle, no event at real finish #62296

Summary

A subagent completion notification is emitted when the child session first goes idle, not when the child's work ends. When a child waits on a background shell, the parent receives state="completed" while the child still works. The real finish sends no second event, so the parent stays idle until the user types.

Environment

• opencode version: 2.2.5
• OS: Linux 7.0.0-38-generic x86_64 (Ubuntu)
• Terminal: TERM=xterm-256color, COLORTERM=truecolor (opencode TUI)
• Shell: /bin/bash
• Install/channel: latest
• Active plugins: caveman, asd-ste100

Reproduction

1. Spawn a background subagent (background: true). Its task starts a long background shell job, then ends its turn and waits for the job.
2. The child goes idle while the shell job runs.
3. In the parent, observe the synthetic subagent event: metadata.state = "completed", while the child's last text says the work continues.
4. The shell job ends. The child wakes on the shell completion event and writes the final report.
5. Observe that no second subagent event reaches the parent.

Expected Behavior

• state="completed" only when the child session has no pending work.
• An event (or a state update) when the child finally ends.

Actual Behavior

• The parent gets state="completed" at the child's first idle.
• No event arrives at the real finish.
• The parent idles indefinitely. Only a user message resumes the session.

Measured on one session (ses_e6328c204ffe0bFi0yELaa7OnI, 24 subagents): 4 early notifications. Gap between the notification and the real last message: 226 s, 483 s, 2057 s, 5851 s.

Additional Context

Worked example, child ses_e508d5162ffeX4osMnA0F9exEU:

• 07:06:24 child idle. Parent event: state="completed", body "Checks 1, 3, 4 done. Check 2 (M5 gate) still running in background. Waiting for its completion notification..."
• 07:06:26 the background shell completes. The child resumes.
• 07:08:14 the child writes the final report.
• 07:10:11 the child idles again. No event to the parent.
• The parent stayed idle until the user typed at 07:17:38 and again at 07:19:35.

The second reported symptom (parent says a subagent is done, or says it is still running) has the same root cause: one event claims completed while its body says the child is still working.

Suggested fix: emit the subagent event on the child's terminal state, when no background job is pending. Alternatively send repeated state updates per child instead of one deduplicated event.

Workaround: no subagents. Run the work on the main thread and use background shell jobs.