Reverse engineering Codex CLI rollout traces I spent a weekend building a DeepSeek proxy for Codex CLI so I could generate real tracing data. The proxying was straightforward. What I found when I looked at the actual trace files was not. The documented format and the real format don't match. This is the story of that mismatch: what I expected, what I found, and why it matters if you're building runtime tooling for coding agents. The setup: why a proxy? Codex CLI uses OpenAI's Responses API (via their SDK). DeepSeek only supports Chat Completions. To use DeepSeek as the backend, I needed a translation proxy — intercept Responses API calls and translate them to Chat Completions.…