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T

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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LKML 2003 — SIGWINCH Only Reaches the Foreground Process Group

Metadata

Field	Value
Institute	Molodetz Institute — Research & Retrieval Division
Subject	shell-multiplexer-auto-attach
Document type	Source Dossier
Tier	1
Source title	RFC/CFT 1/1: SIGWINCH - behaviour change
Source URL	https://lkml.iu.edu/hypermail/linux/kernel/0302.1/1591.html
Source publisher / author	Linux kernel mailing list (2003)
Source type	forum thread
Source date (published)	2003 (approximate, per thread era)
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 kernel-mailing-list discussion establishing that SIGWINCH is only ever delivered to the foreground process group of a terminal — a backgrounded or detached job (exactly tmux's own panes when no client is attached) will not receive it even if the underlying terminal size genuinely changed.

Key findings

A process group needs to be in the foreground to receive SIGWINCH at all; this is a kernel-level restriction, not an application bug.
The direct consequence: relying solely on the signal to learn about a resize is insufficient for anything that can be backgrounded or detached (a tmux session with no client, or any session reattached later) — the size must be re-read and re-applied explicitly on resume/reattach, not assumed to have been kept in sync via signals the whole time.

Pros / strengths

Primary-source kernel discussion, not a secondary summary — authoritative on kernel signal-delivery semantics.

Cons / limitations / caveats

Old (2003) thread; kernel behavior in this specific area has been stable since, per the broader search synthesis, but worth a sanity check against current kernel docs if correctness here is load-bearing for a safety property.

Relevance to tai

Directly explains why tmux itself re-queries and re-applies window size on attach/reattach rather than relying purely on signals (this is exactly the detach/reattach cycle the proposal's whole persistent-session model depends on) — confirms that if tai ever builds any of this logic itself rather than delegating to tmux, it must re-sync size explicitly on every reattach, never assume signals alone kept it current.

Changelog

Date	Change
2026-10-09	Initial dossier created.

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