Files
tai/research/shell-multiplexer-auto-attach/bbs-archlinux-tmux-env-guard.md
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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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Markdown

# Arch Linux Forum Thread — The $TMUX Guard Pattern
## Metadata
| Field | Value |
|---|---|
| Institute | Molodetz Institute — Research & Retrieval Division |
| Subject | shell-multiplexer-auto-attach |
| Document type | Source Dossier |
| Tier | 1 |
| Source title | bbs.archlinux.org forum thread (tmux auto-attach) |
| Source URL | https://bbs.archlinux.org/viewtopic.php?id=144544 |
| Source publisher / author | Arch Linux Forums (community) |
| Source type | forum thread |
| Source date (published) | Unknown — not stated |
| Date researched | 2026-10-09 |
| Researched by | tai (agent), model: Claude Sonnet 5, on behalf of retoor |
| Research method | web search synthesis |
| Confidence | Medium |
| Status | Active |
## Summary
Establishes the core, near-universal guard for auto-attaching tmux from a shell rc file: `[[ -z "$TMUX" ]]`, since tmux itself sets the `$TMUX` environment variable inside any pane it creates. A forum participant confirms a simple `if [[ -z "$TMUX" ]]; then tmux attach; fi` block worked for them in practice.
## Key findings
- `$TMUX` is tmux's own self-identifying environment variable, set automatically inside every pane — checking for its absence is the standard way to avoid launching tmux inside itself (nested sessions).
- This is community-tested, working advice, not a theoretical suggestion.
## Pros / strengths
- Simple, single-variable, directly tied to tmux's own behavior rather than an inferred heuristic — about as reliable a signal as exists for "am I already inside a tmux pane."
## Cons / limitations / caveats
- Only detects nesting on the *same host* — per the query D SSH-nesting dossier in this subject, `$TMUX` does not survive an SSH hop, so this guard alone is insufficient once remote sessions are involved.
## Relevance to tai
The mandatory first guard for the proposal's `.bashrc` hook: never attempt to auto-attach if `$TMUX` (or tai's own equivalent marker) is already set, to prevent runaway nested sessions — this is non-negotiable baseline safety, not an optional refinement.
## Changelog
| Date | Change |
|---|---|
| 2026-10-09 | Initial dossier created. |