What
Claude Code can start a spare process in the background ahead of time, ready to become a session when one is needed. While a spare is parked (waiting), claiming (being taken for a session) or failed, it now behaves differently:
- A parked spare records
spare_parkedbefore it reads any input. - Control requests, the instructions a program sends to a running Claude Code, are refused with an error unless they are of a permitted kind.
- After start-up, a parked spare skips the step that sets up the terminal host, and it tracks idle time for when input arrives.
- When the process shuts down, it does not run your
SessionEndhooks. Before, these hooks always ran at this point. A hook is a script you configure to run at set points, andSessionEndruns when a session ends.
Why
A spare that never became a real session no longer runs your SessionEnd hooks, so those scripts do not fire for sessions you never opened. Refusing most requests while it waits keeps a spare idle until it is actually claimed.
Names in the bundleSessionEnd
The entry above is what we published on the day. These lines were added later, as Anthropic's own pages caught up, and they sit beside the original rather than replacing it.
Confirmed since
Anthropic's documentation has since written up SessionEnd, on Sessions.
- `stop_reason: BetaManagedAgentsSessionEndTurn or BetaManagedAgentsSessionRequiresAction or BetaManagedAgentsSessionRetriesExhausted or 2 more`api/beta/sessions see the edit
One source agreesOne thing we can check says the same as this entry.
Anthropic's documentation agrees
Anthropic's documentation has since written up SessionEnd, on Sessions.