chore(api): describe 30-minute cache-write usage counts

[jbeckwith-oai]

Summary

Describe the optional 30-minute cache-write token metric in usage results.

Changes

• Document input_cache_write_30m_tokens for completions and Decisions usage.
• Keep command flags and request behavior unchanged.

Validation

• The diff is limited to the transformed API reference and generation metadata; no response decoder or command code changes.

[chatgpt-codex-connector]

Codex Review Summary

This comment shows the latest Codex review activity on this pull request.

Review	Status	Commit	Review trigger
📝 Code Review	✅ Completed 2026-10-19T18:13:08.782955Z	f19dc90	Draft marked ready
🔒 Security Review	✅ Completed 2026-10-19T18:14:03.540646Z	f19dc90	Draft marked ready

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[github-actions]

Castiron custom code

Evaluated main: 16662513ea347c92f911c6568203449620642522.

Trusted main policy: 16662513ea347c92f911c6568203449620642522.

✅ No new custom-code files detected.

0 mixed files remain; 0 existing customizations changed.

Compared 16662513ea34 → f19dc90a6d6b. Generated baselines verified.

A changed generated baseline means this report cannot reliably identify which handwritten lines changed.

Inspect the custom-code diff

Download the exact patch produced by this run (requires repository access):

gh run download 39300577502 --repo openai/openai-cli \
  --name castiron-custom-code-39300577502-1 --dir /tmp/castiron-custom-code-39300577502-1
git apply --stat /tmp/castiron-custom-code-39300577502-1/custom-code.patch
cat /tmp/castiron-custom-code-39300577502-1/custom-code.patch

Or reproduce it from an SDK checkout containing the vendored reporter:

git fetch --no-tags origin 16662513ea347c92f911c6568203449620642522 f19dc90a6d6b561d34744a51245694b3ebceb009
python3 scripts/castiron/custom_code_report.py report \
  --base 16662513ea347c92f911c6568203449620642522 \
  --head f19dc90a6d6b561d34744a51245694b3ebceb009 --fetch --require-head-hash --public \
  --out /tmp/castiron-custom-code-f19dc90a6d6b
cat /tmp/castiron-custom-code-f19dc90a6d6b/custom-code.patch

This is the current full custom patch for mixed files, not an attribution of only the handwritten lines changed by this PR.

Full report and patch

[markstuart-oai]

Reviewed f19dc90a6d6b561d34744a51245694b3ebceb009.

The reference schema adds the optional, nullable counter to completions and Decisions without changing required fields. The diff is limited to the schema and generation metadata; command code and runtime dependencies are unchanged.

No blocking findings. Source review only; I did not run the code or tests locally. Observed checks for this commit passed or were skipped; the WSL rerun passed.