Codex: auto-review classifier runs at default effort and shares the main session's prompt_cache_key #181

⚠️ Drafted by Claude (Opus 5.5) in Claude Code at @Butanium's request; not reviewed by a human. We hit this in real use while looking into why Codex usage ran out fast. Draft PR: #183. Close either if it isn't useful.

On the Codex provider, Claude Code's auto-mode classifier runs at the model's default reasoning effort and uses the main conversation's prompt_cache_key. Codex's own approval reviewer uses Low effort and a separate, reviewer-scoped cache key.

Problem

The proxy detects the classifier request (is_claude_auto_review_request) and routes it to gpt-6-luna (#72). Two differences from Codex's own reviewer remain:

• Effort. Stage 1 of the classifier asks for max_tokens: 64, a </severity> stop sequence and thinking: {"type":"disabled"}. None of these has a Codex equivalent, and the request carries no output_config.effort. So reasoning.effort is omitted and Luna reasons at its default effort on every classified action.
• Cache key. prompt_cache_key is the Claude Code session id (request.rs), the same key the main loop uses. The classifier prompt has a different prefix.

Scale: in a replay of a real Claude Code 2.1.293 session, each classifier request was about 55k tokens. That is ~30k of classifier rules, ~12k of the user's CLAUDE.md and the transcript digest, sent once or twice per classified action.

What Codex does

• Low effort when the review model supports it: select_review_model.
• prompt_cache_key = guardian:{parent_thread_id}: prompt_cache_key_override_for_review_session.

Not covered here

• Under ChatGPT auth, Codex reviews with codex-auto-review, while the proxy uses gpt-6-luna.
• Codex's reviewer is its own thread, with its own session-id header, and appends only new transcript to a persistent reviewer conversation. Claude Code rebuilds the digest on every call, and a proxy can't change that.
• feat(auto-review): add opt-in classifier effort override #93 proposed an opt-in effort setting for this route and was closed without comment.

Drafted by Claude Opus 5.5 in Claude Code on behalf of @Butanium; not reviewed by a human.