Codex sessions that run the code review ask for fresh sub-agents #616

Parent

#429

What to build

When Codex runs a session that reviews the change, its prompt asks for fresh reviewer sub-agents (fork_turns: "none"), each given only its own task and the evidence it needs. Security sessions on Codex already ask this. This applies to:

• implement sessions, fresh and Continuation;
• Spec reviews;
• the Repair that reviews Foreign commits;
• every Resume of each of those.

Why: in 54 Codex implement and Spec-review sessions from 7 to 9 October, the model chose fork_turns itself. It used "none" 23 times, "all" 6 times, and left it out 25 times. Codex's tool text says the last two hand the parent's history to the child. So far no reviewer has received the implementer's work, apparently because Codex copies only completed turns. A Resume continues a session whose first turn is complete, though. A review run there could then hand the implementer's whole first turn to the reviewers. That case is inferred and hasn't been seen. This Ticket makes the review's independence a setting, rather than the model's choice or a detail of how Codex forks. Decided in #429's grilling, Q28.

The request is Codex's own, so it belongs to the Codex Harness, not to the Session prompts every Harness shares.

Acceptance criteria

• Every kind of Codex session that runs the code review carries the fresh-sub-agent request, and so does each of its Resumes.
• Codex's thread cap isn't raised for these sessions; it stays a Security session's setting.
• A Codex session that doesn't run the review, such as an Architecture review, is unchanged.
• Sessions on every other Harness are unchanged.
• The prompts page is unchanged: UPDATE_PROMPTS=1 cargo test prompts_page leaves prompts/ as it is.
• The test that keeps fork_turns out of ordinary Codex prompts is narrowed to sessions that don't run the review, and a test covers the review sessions and their Resumes.

Blocked by

None (can start immediately).