Splitting work between AI subscriptions, such as Claude and ChatGPT, means one sometimes drains faster than the others. Re-balancing them mid-job runs into a simple wall: a session stays with the agent that started it.

casr, short for Cross Agent Session Resumer, is a free and open source command-line tool for macOS and Linux. It converts a session from one coding agent into another’s native format and prints the command to resume it, leaving the original untouched; Claude Code, Codex, Gemini CLI, and Cursor are among more than a dozen it reads and writes.

Unlike cswap, which switches Claude accounts, casr lets different models work on one job, albeit half-way. I use it when I need to re-balance the drain between Claude and Codex, and it gets the job done.

The half-way part is context. Message text, order, and roles carry over, but some tool calls become plain descriptions and provider-specific metadata doesn’t always map; the README covers the gap in more detail. If I’m not mistaken, the receiving agent also spends tokens loading the converted session again, much as switching models mid-session does in Claude Code or Codex. For re-balancing subscriptions, half-way is enough.