Run Claude Code and Codex in parallel on Mac

Running Claude Code and Codex at the same time helps when their tasks can progress independently. Start with clear ownership: what each agent may change, which resources it uses, and how you will review the combined result.

This guide is published by Codz and demonstrates its native Mac workspace. The coordination rules also apply when you use separate terminals or another agent workspace.

Give each agent a bounded job

Suppose you are working on an app’s documentation and its test coverage. Give Claude Code the documentation task and Codex a test review. Include the expected result and the files each owns in both prompts.

The second task can begin in Ask or Plan while the first is being written. An agent doing a review does not need write access to the same files. When both jobs need to write shared code, sequence those edits or explicitly choose separate checkouts.

Choose the checkout deliberately

In Codz, start a chat, choose the project, select the agent, and choose the execution location before sending the task. Use the current checkout for work you want to share directly. Choose an isolated worktree when you want that task’s file changes and branch kept separate.

A worktree is a separate checkout of the same repository. It does not make all resources independent:

• Development servers can still compete for the same port.
• Tests can still write to the same database or external service.
• Build tools can still share caches, derived data, or output directories.
• Two branches can still conflict when their changes are combined.

Assign separate ports and test data where needed. Serialize operations that share mutable outputs. For a repository with a one-checkout workflow, respect that policy; do not create worktrees automatically because another agent is running. The Git worktree manual explains the underlying Git behavior.

Follow decisions from one window

Open the two chats in Codz and keep each task’s goal visible in its conversation. The transcript shows the work as it happens, while the rail keeps the diff, files, terminal, and browser beside the chat.

The product scene is an illustrative example of Codz working on Codz.

An approval is a decision about a specific action. Read the command, path, or diff before approving it. A blocked task may need an answer rather than more agents. Stop or redirect work that has crossed into another task’s files before the overlap grows.

Codz’s modes and approvals explain the permissions available for a chat. Choose the mode for the work you want done; parallel execution does not justify broader permissions.

Review each task before combining it

For each result, ask for a short account of what changed, what was tested, and what remains uncertain. Then inspect the diff yourself. In Codz, open the Git panel or the change card to review the files and select what belongs in the change.

If you chose separate worktrees, combine the reviewed branches through your normal Git process. Run the relevant checks again against the combined result. Two independently passing branches can still fail together because they change an interface, a fixture, or shared state.

If the agents shared a checkout, keep commits and staging under one owner. Confirm that the diff contains only the intended task before committing; another agent’s uncommitted work is not permission to include it.

Check whether parallel work helped

Look at the completed change, review time, failed runs, and the amount of coordination it required. Usage totals can help explain repeated work, but more tokens or more simultaneous chats are not proof of progress.

Parallel work is a good fit for independent investigations, separate components, and a review alongside implementation. A small change in one tightly coupled file is often easier to finish sequentially.

Start with two agents

Use one implementation task and one bounded review, agree on ownership, and finish the full review-and-test loop. Add another task only when you can explain what it owns and how it avoids the resources already in use.

The agent overview, Git and worktrees, and change-review reference describe the controls used in this workflow.