Expose costs of api call

[visory-kunal]

It would be useful using this as a github action to return costs as you can with the openai sdk/ api.

[adamhenson]

I ran into the same need. While native cost output isn't available yet from this action, I built a workaround that's been working well in production.

The Codex CLI writes a rollout JSONL file to $CODEX_HOME/sessions/…/rollout-*.jsonl when running without --ephemeral. The last token_count event in that file contains cumulative totals for the full run. You can extract them with a shell step after the codex step and pass them to a tracking action.

I packaged this pattern into AgentMeter Action — it extracts token counts from the rollout file, calculates cost using live pricing, and posts a summary on the PR. Works with openai/codex-action today without any changes to this action.

That said, having input_tokens, output_tokens, and cached_input_tokens as native step outputs here (similar to what anthropics/claude-code-action does) would be the right long-term fix. Happy to submit a PR for that if it would be accepted.