Under the hood
stage_file now flags outputs-mount paths and tracks concurrency for non-filestore staging
What
The stage_file control request now checks whether the requested mount_path falls under a new STAGE_FILE_OUTPUTS_MOUNT_PREFIX path and flags it if so. Separately, requests that don't include a filestore_path are now wrapped in a begin/cleanup pair that tracks concurrency and keeps the process alive while staging is in progress, which wasn't done before.
Why
The mount-path check lets Claude Code distinguish files staged to a special outputs location. The added concurrency tracking for non-filestore staging helps ensure such staging operations complete properly rather than being cut short.