What
A warm spare is a Claude Code session started in advance so it is ready when needed. Each spare now remembers the extra launch arguments (extraArgs) it was started with.
- When the pool checks its spares and finds different arguments, it restarts the spare, logged as
extra_args_mismatch_reboot. - When something tries to claim a spare with outdated arguments, the claim is refused as
stale-argvand a new session is started from scratch instead.
Why
A claimed spare no longer runs with outdated launch options. The cost is that a mismatch means waiting for a fresh start instead of getting a ready session.