Sub-agent bash tasks stuck 'running' in Tasks panel after agent completes; Stop button no-op

Symptom

When the main chat spawns a sub-agent via the Agent tool with run_in_background: true, and that sub-agent internally invokes Bash commands, those bash commands appear in the UI Tasks panel. After the sub-agent has fully completed (completion notification has reached the parent chat, commits pushed, agent summary received), the bash tasks remain listed as "Wird ausgeführt" / "Running" in the panel. Clicking the Stop button next to one of those tasks has no visible effect — the task stays in the list.

Repro

1. In the main chat: spawn ≥2 sub-agents in parallel with run_in_background: true. Each sub-agent should internally run several Bash commands (e.g. Run pytest …, Run baseline tests).
2. Wait until both sub-agents finish (completion notifications arrive in the parent chat).
3. Open the UI Tasks panel → the sub-agents' internal bash tasks are still shown as "Wird ausgeführt".
4. Click Stop on one of them → no effect; the task stays in the list.

Concrete example observed today (2026-05-12)

• Sub-agent A (id a03326852bd70edf8): "Fix node_join.py alias_fields + LEFT JOIN bugs" → committed 7bbcc9a2, sent its result summary back to parent.
• Sub-agent B (id a4aef66c9086d38ef): "Fix compound_filter neq with empty string" → committed 3785c5c6, sent its result summary.
• 1+ hour after both completion notifications arrived, the UI shows 12 bash tasks still as "running":
• Run baseline tests
• Run pytest with -x to fail fast
• Test if Bug 1 is fixed
• Re-test Bug 1 fix execution
• Run pytest skipping pre-existing failure
• Find close_jn references in history
• Wait for pytest to finish, print summary
• Run full test suite excluding live/drive cache tests
• Run focused test suite without slow tests
• Run full test suite
• Wait for tests to complete
• Run tests with unbuffered output

On the OS side there are no corresponding processes alive (ps aux | grep pytest empty). It's purely a UI state-sync issue.

Expected

When a sub-agent completes (regardless of success/error/cancelled), every bash task started during its lifetime should disappear from the parent chat's "running" indicator. The Stop button on a stuck task should at minimum let the user clear the slot manually.

Suspected cause

The Tasks panel probably counts bash slots transitively (parent-chat bashes + all sub-agent bashes). When the agent's lifecycle ends, the cleanup event for the children isn't propagated into the UI pipeline.

Side effect

The status line shows e.g. "12 Shells laufen" / "12 shells running" even when the OS has zero such processes. Cosmetic but confusing.

Platform

• Claude Code CLI (macOS, Darwin 25.3.0)
• Model: Opus 4.7 (claude-opus-4-7)
• Project: a software-engineering session with two parallel sub-agents

Workaround

None known besides ignoring it until next UI refresh / session change. No functional impact.