jif bc5957eac9 Preserve parent cache affinity for ephemeral forks (#44862) ...

## Why

ChatGPT derives Responses cache affinity from the `session-id` header. Ephemeral forks need to reuse their parent's cache routing while retaining their own session and thread identities.

## What changed

- Inherit the parent session ID as the `prompt_cache_key` for ephemeral root forks.
- Use the prompt cache key for root-agent Responses `session-id` headers, including WebSocket handshakes. Preserve the actual session identity in turn metadata and leave non-root-agent routing unchanged.
- Keep enabled goal tool definitions visible on ephemeral threads, but reject execution with `Goal tools require a persistent thread.` and disable automatic goal continuation without persistent state.

## Testing

Add regression coverage for inherited cache routing with distinct fork identities, matching parent and fork tool definitions, WebSocket session headers, and rejection of ephemeral goal tool execution.

GitOrigin-RevId: d235e97630068b27f7ebd562dd23ac6266ebc1b9

2026-09-11 16:41:56 +00:00

..

accounting.rs

Block goals after three empty automatic continuation turns (#44320)

2026-09-09 22:27:37 +00:00

goal_extension_backend.rs

Preserve parent cache affinity for ephemeral forks (#44862)

2026-09-11 16:41:56 +00:00

steering.rs

Make the update_plan tool opt-in (#41744)

2026-08-31 00:53:30 +00:00