The shipped subagent example could say a child was done while it was
still working, lose the useful part of process failures, and return a
normal-looking tool result when the delegated work had actually failed.
Single and chain output could also exceed the normal tool limit.
This also adds a dedicated regression suite covering progress state,
cancellation, process failures, output limits, cwd-based agent
selection, and persisted tool-result error state.
After this change:
- queued, running, completed, failed, and aborted work stay distinct
throughout the run;
- interrupting the parent run preserves partial child results, stops
queued work from starting, and escalates when a child ignores SIGTERM;
- signal exits, spawn failures, provider errors, stderr, and assistant
output remain visible instead of collapsing to `(no output)`;
- failed subagents become failed tool results, so the parent model can
react instead of treating them as successful calls;
- single and chain results stay within the normal 50 KB / 2,000-line
limit;
- project agents are selected and confirmed from each task's actual
working directory rather than the dispatcher's directory.
## Further potential improvements
These are useful follow-ups, but they are separate product and storage
decisions rather than part of the failure-handling fixes in this PR.
<details>
<summary>Potential follow-ups</summary>
### Keep persisted transcripts bounded
Subagent tool results persist the full child message history in
`details`, which can make parent session files large and slow to reload.
A follow-up could compact that history or spill it to disk.
### Define an aggregate parallel-output budget
Parallel mode still gives every task its own 50 KB budget. A follow-up
could keep every task represented while enforcing one overall
tool-result limit.
### Report child usage to the calling session
Per-child token and cost usage is visible in result cards but is not
added to the calling session's totals.
### Isolate malformed agent definitions
One malformed YAML agent can still break discovery for every valid agent
in the same directory.
### Limit subagent recursion
A nesting limit would prevent accidental process and paid-request
multiplication when subagents can invoke the subagent tool again.
* https://github.com/earendil-works/pi/issues/8195
### Add a configurable timeout
Unattended runs would benefit from a generous opt-in timeout for
children that never complete.
</details>
## Related issues
### Spawn failures lose their diagnostics
This directly addresses the reported case where a nonexistent child
working directory produces `(no output)` instead of the actual spawn
error. The regression suite includes that same reproduction.
* https://github.com/earendil-works/pi/issues/8129
### Persisted child history can bloat sessions
This PR intentionally keeps full child history in tool-result details,
so session compaction or spill-to-disk remains follow-up work rather
than something fixed here.
* https://github.com/earendil-works/pi/issues/7452
Breaking changes:
- Settings: 'hooks' and 'customTools' arrays replaced with 'extensions'
- CLI: '--hook' and '--tool' flags replaced with '--extension' / '-e'
- API: HookMessage renamed to CustomMessage, role 'hookMessage' to 'custom'
- API: FileSlashCommand renamed to PromptTemplate
- API: discoverSlashCommands() renamed to discoverPromptTemplates()
- Directories: commands/ renamed to prompts/ for prompt templates
Migration:
- Session version bumped to 3 (auto-migrates v2 sessions)
- Old 'hookMessage' role entries converted to 'custom'
Structural changes:
- src/core/hooks/ and src/core/custom-tools/ merged into src/core/extensions/
- src/core/slash-commands.ts renamed to src/core/prompt-templates.ts
- examples/hooks/ and examples/custom-tools/ merged into examples/extensions/
- docs/hooks.md and docs/custom-tools.md merged into docs/extensions.md
New test coverage:
- test/extensions-runner.test.ts (10 tests)
- test/extensions-discovery.test.ts (26 tests)
- test/prompt-templates.test.ts
2026-01-05 01:43:35 +01:00
Renamed from packages/coding-agent/examples/custom-tools/subagent/README.md (Browse further)
