retoorandClaude Sonnet 5
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- Plexer: always-active terminal multiplexing. NativePlexerController/ TmuxPlexerController share one interface, chosen by which env var is already set (TAI_PLEXER_SOCKET vs TMUX_PANE); NativePlexerBackend is the pty.fork()-based wrapper (raw mode, SIGWINCH resize forwarding, a Unix-socket control protocol, continuous session logging, a Ctrl+A prefix key distinct from tmux's own Ctrl+B). Auto-wraps new interactive shells via a .bashrc hook mirroring the existing command-not-found install pattern, gated on $TMUX/$TAI_PLEXER_ACTIVE/ a $HOME/.tai-no-plexer bypass. New plexer_send/read/type/status tools, env-gated on a detected controller. - tests/container.py + docker-compose.yml + tests/docker/Dockerfile: a disposable podman/docker image for the tests that must never touch a real machine (installing the plexer hook into a real ~/.bashrc, a live tmux session). Required suite (test_seal.py, test_tai.py, tests/plexer.py, tests/bashrc.py) gates the result; tests/rag.py runs as best-effort since its real-LLM dependency can't be satisfied inside a disposable container with no nested engine. - tests/bashrc.py: real end-to-end hook install + bash -i auto-wrap, anti-recursion, tmux-active skip, non-interactive skip, a live TmuxPlexerController test, and an install/uninstall round-trip. - tests/plexer.py: NativePlexerBackend under a real pty, plus a dedicated robustness pass (file permissions, >64KB payload framing, a malformed control request, a genuine self-deadlock fix in the write-to-child path). - tai_test.py: the shared async process-driving framework (pipe/pty transport, group-wide kill-and-reap, a StdinBridge for --interactive) both test files build on. - ChatClient last-resort backend: when there's no local opencode CLI but the sandbox box is already running, install opencode into it (official Node tarball, not apt -- apt's nodejs/npm pull in webpack/babel/jest as transitive deps) and route through it instead of giving up. Only reachable after the first retry round already failed everything else; never creates the box itself. TmuxPlexerController.status() fixed to use `list-panes` instead of `display-message -p`, which silently fell back to the default pane instead of erroring against a dead target. - Fix 4 pre-existing test_tai.py bugs surfaced by running it in a clean environment for the first time: two stale mock signatures (subprocess.run's stdout= kwarg, Chat.complete's deadline= kwarg), one $TMUX-dependent catalog assertion, one tty-dependent color assertion. - research/: a sourced research archive (Source Dossier/Citation Card/Conclusion tiers) backing the above design decisions, with its own audit.py consistency checker. - .gitignore: fix a blanket *.md rule that was about to silently drop the entire research/ archive from version control; add __pycache__/ and the one-off debug transcript this session started from. Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
48 lines
2.7 KiB
Markdown
48 lines
2.7 KiB
Markdown
# Your timeout killed the process, not the process group — Iannucci Solutions
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## Metadata
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| Field | Value |
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| Institute | Molodetz Institute — Research & Retrieval Division |
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| Subject | async-pty-process-testing |
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| Document type | Source Dossier |
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| Tier | 1 |
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| Source title | Your timeout killed the process, not the process group |
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| Source URL | https://www.iannuccisolutions.com/blog/timeout-does-not-kill-child-processes.html |
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| Source publisher / author | Iannucci Solutions (blog) |
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| Source type | blog post |
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| Source date (published) | Unknown — not stated |
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| Date researched | 2026-10-09 |
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| Researched by | tai (agent), model: Claude Sonnet 5, on behalf of retoor |
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| Research method | web search synthesis |
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| Confidence | High |
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| Status | Active |
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## Summary
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A blog post documenting a real incident: a script's timeout mechanism killed only the top-level process it had launched, while a worker process that script had itself spawned kept running in the background. The root cause and fix described are directly applicable to any subprocess-timeout design.
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## Key findings
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- `proc.kill()`/`proc.terminate()` signal only the direct child process — if that child spawns further children (a shell command, a subagent, a worker), killing the direct child does not propagate to them.
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- The documented fix: start the child in its own session/process group (e.g. `start_new_session=True` in Python), which makes the child's PID equal to its process group ID (PGID), then signal the whole group (`os.killpg(pgid, sig)`) rather than just the one process.
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## Pros / strengths
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- A concrete, lived incident report, not a theoretical warning — the exact failure mode (worker alive after the "parent" was killed) is precisely the risk a test framework's timeout handling needs to guard against, since `tai.py` itself can spawn subagents and shell commands.
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## Cons / limitations / caveats
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- Describes the synchronous `subprocess` module's behavior; the asyncio adaptation (confirming `start_new_session=True` is forwarded correctly by `asyncio.create_subprocess_exec`) was treated as a reasonable extrapolation, not independently verified against asyncio's own documentation in this specific source.
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## Relevance to tai
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This is the direct, primary justification for `tai_test.py`'s `ManagedProcess` always spawning with `start_new_session=True` and `terminate()` using `os.killpg(self.proc.pid, sig)` rather than `self.proc.terminate()`. Without this, a timed-out test driving `tai.py` through a shell command or a forked subagent could leave that spawned work running indefinitely in the background after the test framework believed it had cleaned up.
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## Changelog
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| Date | Change |
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| 2026-10-09 | Initial dossier created. |
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