Encode the hard-won lesson from the forkserver
cancel-cascade investigation into two skill docs
so future sessions grep-find it before spelunking
into trio internals.
Deats,
- `.claude/skills/conc-anal/SKILL.md`:
- new "Unbounded waits in cleanup paths"
section — rule: bound every `await X.wait()`
in cleanup paths with `trio.move_on_after()`
unless the setter is unconditionally
reachable. Recent example:
`ipc_server.wait_for_no_more_peers()` in
`async_main`'s finally (was unbounded,
deadlocked when any peer handler stuck)
- new "The capture-pipe-fill hang pattern"
section — mechanism, grep-pointers to the
existing `conftest.py` guards (`tests/conftest
.py:258`, `:316`), cross-ref to the full
post-mortem doc, and the grep-note: "if a
multi-subproc tractor test hangs, `pytest -s`
first, conc-anal second"
- `.claude/skills/run-tests/SKILL.md`: new
"Section 9: The pytest-capture hang pattern
(CHECK THIS FIRST)" with symptom / cause /
pre-existing guards to grep / three-step debug
recipe (try `-s`, lower loglevel, redirect
stdout/stderr) / signature of this bug vs. a
real code hang / historical reference
Cost several investigation sessions before the
capture-pipe issue surfaced — it was masked by
deeper cascade deadlocks. Once the cascades were
fixed, the tree tore down enough to generate
pipe-filling log volume. Lesson: **grep this
pattern first when any multi-subproc tractor test
hangs under default pytest but passes with `-s`.**
(this commit msg was generated in some part by [`claude-code`][claude-code-gh])
[claude-code-gh]: https://github.com/anthropics/claude-code
Gud Boi