Follow-up to the salvaged #96044 hunk: drop the 'or callable(...)' arm —
callable(MagicMock) is True, which would have flipped stubbed sessions
into the fast-fail race the surrounding comment explicitly routes to the
plain-await path. inspect.iscoroutinefunction alone reproduces the old
isawaitable(call) split exactly (real async def / AsyncMock -> race,
MagicMock -> plain await) without creating the leaked coroutine.
Apply-ready delta distilled by @andrexibiza: deterministic watcher-consumer
tests (watcher times out while a child is alive, resolves when all are dead),
psutil-unavailable fail-open pin, and probe-failure fail-open handling in
_stdio_children_dead (unknown is never proof that every child exited).
Local: 8 passed on tests/tools/test_mcp_stdio_children_dead.py
_stdio_children_dead returned True ('all children dead') on the first LIVE
pid — the intended False was dead code right below it. Every spawn path
that captures child PIDs (observed in hermes -z oneshots) then failed the
#81995 pre-call fast-fail with 'TimeoutError: MCP stdio subprocess ... has
exited' on every tools/call while the subprocess was demonstrably alive.
Long-lived gateway/dashboard sessions were unaffected only when
_stdio_child_pids was empty (the not-pids short-circuit).
Return False on the first live pid and drop the unreachable line.
Teknium