fix(cli): fall back to SelectSelector when kqueue can't watch stdin on macOS#26077
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On macOS with uv-managed cPython 3.11, the default kqueue selector cannot
register fd 0, so prompt_toolkit's loop.add_reader raises
OSError(EINVAL) ("[Errno 22] Invalid argument") from kqueue.control()
and the agent crashes immediately on startup (#5884, also reported in
#6393).
Probe KqueueSelector.register(0, EVENT_READ) before launching
prompt_toolkit. If it fails, install an event-loop policy that returns a
SelectorEventLoop backed by SelectSelector — select() works fine on
stdin in this Python build, so add_reader succeeds and the agent
launches normally.
Also extend the existing #6393 fallback handler to recognize EINVAL /
EBADF / "Invalid argument" so that any future selector failure on stdin
shows the friendly "reinstall Python via pyenv or Homebrew" guidance
instead of an opaque traceback.
Verified on macOS (Darwin 24.6.0) with uv-managed cPython 3.11.15: the
kqueue probe fails, the policy switch fires, and `hermes` launches
cleanly. No effect on platforms where kqueue can register fd 0.
This was referenced May 15, 2026
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🔎 Lint report:
|
alt-glitch
added
type/bug
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Salvage of #20948 by @outdoorsea onto current main.
Summary
Prevents the
OSError: [Errno 22] Invalid argumentstartup crash that hits uv-managed cPython 3.11 on macOS (issue #5884). ProbesKqueueSelector.register(0, EVENT_READ)at CLI startup; on failure, installs an event-loop policy that returns aSelectorEventLoop(SelectSelector())so prompt_toolkit'sadd_reader(0, …)works. Also widens the existingexcept (KeyError, OSError)net to matchEINVAL/EBADF/ "Invalid argument" so any future leak hits the friendly "reinstall Python via pyenv/Homebrew" message instead of a raw traceback.Changes
cli.py: kqueue probe + SelectSelector fallback beforeapp.run(); widened post-app.run()except. Gated onsys.platform == 'darwin', no-op on Linux/Windows and on Homebrew/pyenv/system Python.scripts/release.py: AUTHOR_MAP entry forjeremy@geocaching.com→outdoorsea.Validation
py_compile cli.pyok.#6393os.fstat(0)stdin pre-check.Fan-out
~15 sibling PRs (#19501, #21660, #20482, #18363, #11253, #12111, #11866, #8796, #13251, #9996, #15720, #8843, #15706, etc.) target the same crash but only widen the except. This PR is the only one that actually prevents the failure. They'll be closed pointing here.
Closes #5884
Supersedes #20482, #21660, #19501, #18363, #11253, #12111, #11866, #8796, #13251, #9996, #15720, #8843, #15706