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retoorandClaude Sonnet 5 9dbd1fe667 Add plexer subsystem, container test infra, and last-resort opencode box backend

- 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>

2026-10-10 04:36:05 +02:00

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Your timeout killed the process, not the process group — Iannucci Solutions

Metadata

Field	Value
Institute	Molodetz Institute — Research & Retrieval Division
Subject	async-pty-process-testing
Document type	Source Dossier
Tier	1
Source title	Your timeout killed the process, not the process group
Source URL	https://www.iannuccisolutions.com/blog/timeout-does-not-kill-child-processes.html
Source publisher / author	Iannucci Solutions (blog)
Source type	blog post
Source date (published)	Unknown — not stated
Date researched	2026-10-09
Researched by	tai (agent), model: Claude Sonnet 5, on behalf of retoor
Research method	web search synthesis
Confidence	High
Status	Active

Summary

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.

Key findings

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.
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.

Pros / strengths

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.

Cons / limitations / caveats

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.

Relevance to tai

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.

Changelog

Date	Change
2026-10-09	Initial dossier created.

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