Files

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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Conclusion: tai_test.py's Transport, Cleanup, and Framework Design

Metadata

Field	Value
Institute	Molodetz Institute — Research & Retrieval Division
Subject	async-pty-process-testing
Document type	Conclusion
Tier	N/A
Date decided	2026-10-09
Decided by	retoor, advised by tai (agent, Claude Sonnet 5)
Status	Active
Confidence	High

Question / problem statement

How should tai_test.py — a reusable integration-test framework for driving tai.py both as a one-shot subprocess and as a persistent interactive REPL (including scripting input and detecting turn boundaries) — be built so that it's safe (no leaked zombie processes on timeout, crash, or cancellation) and extensible (a clean base class future tests can subclass), using only the Python standard library, consistent with tai.py's own zero-dependency rule?

Conclusion

The framework uses two unified transports behind one asyncio.StreamReader-based interface: plain asyncio.create_subprocess_exec with PIPE streams for one-shot calls, and a real pty (stdlib pty.openpty(), the slave fd given to the child as stdin/stdout/stderr, the master fd wrapped into a StreamReader via loop.connect_read_pipe) for anything that needs the child to behave as if a human were typing — because tai.py's own code branches on sys.stdin.isatty(). Optional live human stdin passthrough is bridged via loop.add_reader + raw os.read on the fd (never buffered sys.stdin, which blocks), with no background thread, mirroring how the child's own output is already consumed. Every process is started with start_new_session=True and torn down through an escalating SIGTERM-then-SIGKILL os.killpg call that always finishes with proc.wait() to reap it, so a timeout or crash never leaves an orphan. The TestCase base class (setup/run/verify/teardown hooks, typed exceptions carrying the full transcript) follows the declarative-base-class-plus-override-hooks pattern used by real prior art (CERN's Gaudi, gem5, OpenStack's oslotest) rather than being invented from scratch.

Supporting sources

../ptyprocess-docs.md, ../pypi-shellous.md, ../github-agents-issue1-controlling-terminal.md — established why a real pty (not a pipe) was needed, and the documented, accepted limitation that tai_test.py's pty mode does not call ioctl(TIOCSCTTY) and so doesn't guarantee job-control signal semantics.
../github-gist-nonblocking-stdin-os-read.md, ../python-asyncio-issue499-add-reader-eof.md, ../glama-mcp-remote-py-stdio-jsonl.md — the exact techniques StdinBridge (raw os.read via add_reader) and ManagedProcess's pty-mode StreamReader wrapping (loop.connect_read_pipe) implement.
../pypi-pexpect.md, ../pyte-terminal-emulator.md, ../pypi-stitch-pty.md — the alternatives surveyed and not adopted.
../iannuccisolutions-timeout-process-group.md, ../python-docs-asyncio-subprocess.md, ../alexandra-zaharia-kill-subprocess-children-timeout.md, ../execa-termination-docs.md — the direct justification for start_new_session + killpg + always-reap.
../discourse-merge-two-streams.md — the reason a generic multi-stream-merge utility was deliberately not built.
../gaudi-subprocess-base-test.md, ../gem5-test-infrastructure-commit.md, ../oslotest-timeout-fixture.md — the test-framework architecture TestCase is modeled on.
../discourse-subprocess-process-gc.md, ../slingacademy-stop-kill-child-process.md, ../bpo-wait-for-timeout-leaves-process-alive.md — confirmation that relying on timeout or garbage collection alone to clean up a process is documented, known-unreliable, which is why execute()'s finally block always calls terminate() explicitly regardless of how the test ended.

Alternatives considered and rejected

pexpect — rejected because it's a blocking/synchronous library and tai_test.py is asyncio-native throughout; mixing a blocking library in would have meant either wrapping every call in a thread executor or accepting blocking the event loop, neither of which fit.
stitch-pty — rejected as too young/unverified to depend on for core framework plumbing, and as a compiled Rust-backed dependency it would also have violated the project's stdlib-only constraint.
A generic tagged-queue multi-stream-merge utility — rejected because the Discourse thread's own participants described the resulting async-generator plumbing as hard to maintain, and tai_test.py's actual need (merging stdout+stderr in pipe mode) is fully satisfied by the simpler stderr=STDOUT subprocess argument, making the general utility unnecessary complexity.
A background thread for bridging live stdin — not rejected as wrong, but passed over in favor of loop.add_reader + os.read specifically so stdin-bridging follows the same no-thread, fd-based pattern as the child's own output handling, rather than mixing two different concurrency models in one framework.

Risks / open questions

The pty mode does not explicitly call ioctl(TIOCSCTTY), so there is no guarantee the child's session becomes the pty's controlling terminal in the full job-control sense. isatty()-based behavior (all that tai.py's own code checks) is unaffected, since that's a property of the fd itself, not of session leadership — but SIGWINCH-based resize forwarding and tty-line-discipline-generated Ctrl-C-as-SIGINT are not guaranteed to work. This is accepted because no test built so far needs either capability; every test built on tai_test.py so far only scripts line-based input/output.

Action taken

Implemented the same day as this research: tai_test.py (ManagedProcess, StdinBridge, TeeLogger, TestCase, TestRunner, main_cli) at the repository root, and tests/rag.py built on it — both already in use and passing against the real tai.py binary.

Changelog

Date	Change
2026-10-09	Initial conclusion recorded.

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