Using Codex and Claude Code Together: A Handoff That Does Not Double the Work

If you pay for both Codex and Claude Code, give them different jobs. Let one make the change and ask the other to review a specific risk in the result. Having both rebuild the same feature usually adds another problem: deciding which version to keep.

For the subscription side of this setup, our Claude and Codex budget guide looks at how to divide a limited monthly budget between the two tools.

The planner, executor and reviewer are roles. They should not be permanently assigned by a model's reputation when your own tasks provide better evidence.

Make the second opinion useful

A second opinion is useful when you're unsure about an approach or need someone to challenge a patch. It becomes expensive when the second agent has to rediscover the whole project, or when both spend their time agreeing with each other. A short handoff and clear ownership make the difference.

The practical question is how to get an independent check without paying twice to rediscover the repository.

Give each stage an output

The planner should produce a short implementation brief: the behavior to change, constraints, relevant files and acceptance checks. It should investigate unclear requirements before expanding the plan. A plan that reproduces the entire repository is expensive to create and difficult for the executor to follow.

The executor should produce a coherent diff and the evidence that the specified behavior works. It owns the edits during this stage. The reviewer should identify reproducible defects or consequential risks in that diff, rather than generate a new wish list for the product.

You can run all three stages with one subscription. Add a second only when independent review or overflow capacity earns its place.

Make the handoff smaller than the conversation

Give the receiving agent the current commit or diff, the user's requirement, accepted design decisions and commands needed to reproduce the result. Include known failures, especially failures that predate the change. Leave out obsolete plans and repeated progress messages.

For a review, a useful request is: inspect authorization behavior and empty-state handling in this patch; reproduce any claimed defect; do not edit until findings are reviewed. That is more discriminating than “review everything and make it better.”

Repository instructions should contain durable conventions, while the handoff contains this task's specific constraints. OpenAI's custom review guidance describes using scoped repository rules to focus review and keeping mechanical checks in CI. An agent review supplements those checks; it does not replace enforcement. Repository-specific review rules.

Avoid competing edits

If agents need to work concurrently, use separate worktrees or separate files with explicit ownership. Decide who merges the result and runs the combined checks. Separate worktrees isolate working copies, but they do not automatically resolve incompatible design decisions or shared external database writes.

The Codex worktree documentation explains isolated chats in a repository. The general coordination rule applies across tools too: each agent needs a clear view of which changes it owns and which state it must preserve. Worktree documentation.

For a sequential workflow, the simpler option is usually enough: finish one stage, inspect the diff, then hand over. Parallelism is useful only when the tasks are genuinely independent.

Choose the daily executor empirically

Run a small set of recurring tasks with each product and record accepted outcomes, supervision time and allowance consumption. Use the tool that reliably finishes your ordinary work as the default executor. Escalate difficult architecture or debugging questions when the default fails a concrete criterion, rather than routing every prompt to the most expensive setting.

The second agent's review should be judged by useful findings, including how often it invents problems. Agreement between agents is not proof of correctness: both can share the same misleading assumption. Tests, runtime observations and the user's actual requirement remain the deciding evidence.

When to cancel the second subscription

Keep a short ledger of decisions the second tool changed and errors it helped prevent. If it mostly repeats the first agent's explanation, rarely gets used, or causes more integration work than it saves, return to one subscription.

Keep the second subscription if you can point to recent mistakes it caught, decisions it improved or work it let you finish while the first was limited. If it mostly repeats what you already know, one subscription may be enough. You can always add the second again when the work calls for it.