Running Codex and Claude Code side by side
Putting them side by side is just picking one per cell. The differences arrive afterwards.
Table of contents
Where the conventions diverge
| Claude Code | Codex | |
|---|---|---|
| Session id | we mint it | it mints its own |
| Resuming | --resume <id> | resume <id> |
| Waiving approvals | --permission-mode | none |
| Tool-call history | kept | turn edges only |
| Dollar cost | shown | not shown |
Approvals matter most. Left running in parallel, Codex always stops somewhere, so being told that it stopped has to be arranged first.
Picking between them
Claude Code shows more of itself. Good for long unattended work you will want to audit later, and approvals can be waived so it keeps moving.
Codex stops and asks. Inconvenient in parallel, reassuring on work you do not want running ahead of you — touching production configuration, for instance.
Sending one task to both
Cheap once they are side by side. Open two cells, give the same instruction, compare what comes back.
It is also the escape hatch when one gets stuck. Same repository is fine: the worktrees are separate, so both touching the same file breaks nothing.
Separate subscriptions
Claude Code subscriptions can be assigned per cell. See rotating between subscriptions; the Codex equivalent is in using several Codex subscriptions.
Related
日本語版: codex-and-claude-code