## Why
Reasoning configuration changes need to retain their position and trusted provenance when model history is persisted and replayed. Client-injected history must not be able to forge these controls.
## What changed
- Add a typed `configuration_update` response item carrying reasoning effort, including custom model-defined values.
- Persist harness-authored updates with provenance and preserve them across history reconstruction, thread resume, raw response notifications, and agent forks.
- Exclude untrusted configuration updates from model history, strip client-supplied provenance metadata, and reject configuration updates supplied as turn input.
- Export the new item through the JSON and TypeScript app-server schemas and classify it in telemetry and persistence metrics.
## Testing
- Cover serialization, provenance persistence, history filtering and rollback, resume reconstruction, and injection attempts before and after restart.
GitOrigin-RevId: eb5559d2b52b7a931621e7c9812f009ff9fb8939
0d502a4230