Claude Code vs Codex CLI session logs

The two most used terminal agents both keep sessions as JSONL files on your machine. The details differ in ways that matter if you want to keep, measure or share them.

#Side by side

#The difference that bites: retention

Claude Code removes sessions older than 30 days unless you raise cleanupPeriodDays. Codex keeps everything and compresses what is old. If you use both, your Codex history probably goes back further than your Claude Code history, even if you used Claude Code more.

{ "cleanupPeriodDays": 365 }

#The difference that bites tools: compression

Tools that only look for .jsonl files miss Codex's compressed sessions. ccusage and the groundedby evaluator read both.

#Training defaults

• Claude Code on Free, Pro and Max plans may be used for training unless you opt out. Team, Enterprise and API use are excluded.
• Codex on personal ChatGPT plans follows the "Improve the model for everyone" setting. Business, Enterprise and Edu are not used by default.

What the terms say.

#Details

Claude Code storage · Codex storage · What is inside a session file