Closing — re-evaluated against the original tracker goal in #23972 ("ruff complexity reduction"). The actual LOC accounting here is net positive (+26 / +66 / +85 / +139 across the stack), not negative.

The C901 number drops (45/51/39/37 → all <22) come at a real cost: each extracted helper carries ~3-6 lines of decomposition tax (signature + docstring + return-plumbing for shared locals that the original monolithic function held in scope). The helpers themselves are real single-responsibility units, but Python's function-scope semantics don't give us a free way to split without that tax.

For complexity reductions that trade LOC for testability, the bar is "is the function so untestable that the tax is worth it?" — and for these four codex functions, they're already exercised by the agent-loop integration tests in tests/run_agent/ and tests/agent/test_codex_responses_adapter.py. The bisect-during-debug argument is real but doesn't justify +139 LOC in already-covered code.

What's still moving forward from this tracker:

• refactor: extract 6 helpers from convert_messages_to_anthropic #23968 (convert_messages_to_anthropic, 79→10, net -4 LOC) — net negative on both LOC and complexity, will be rebased and shipped separately.

If a future refactor of these codex functions ends up net-negative on LOC (e.g. by collapsing repeated patterns or eliminating dead-code branches alongside the extraction), I'll reopen.