> ## Documentation Index
> Fetch the complete documentation index at: https://docs.microsandbox.dev/llms.txt
> Use this file to discover all available pages before exploring further.

# Codex CLI

> Run OpenAI Codex CLI against a project on your host

This example installs a pinned Codex CLI release inside a Node.js microVM and opens it in a project mounted from your host. Codex can work directly in the checkout, while its executable, authentication, configuration, and sessions stay inside the sandbox.

## Run Codex CLI

<Steps>
  <Step title="Start Codex">
    <Tooltip tip="Writable host-directory mounts are local-only. On microsandbox cloud, use the isolated-copy alternative and omit replace-on-create."><span className="msb-badge-local">Local-only <Icon icon="circle-info" size={11} /></span></Tooltip>

    Replace `./my-project` with the project directory you want Codex to work on:

    <CodeGroup>
      ```sh macOS & Linux theme={null}
      msb run -t --name codex-demo --replace \
        --cpus 2 --memory 2G --root-disk 4G \
        --mount-dir ./my-project:/workspace:rw \
        --workdir /workspace \
        node:24-bookworm-slim -- sh -lc '
          apt-get update &&
          apt-get install -y --no-install-recommends ca-certificates git &&
          npm install -g @openai/codex@0.148.0 &&
          exec codex
        '
      ```

      ```powershell Windows theme={null}
      msb run -t --name codex-demo --replace `
        --cpus 2 --memory 2G --root-disk 4G `
        --mount-dir ./my-project:/workspace:rw `
        --workdir /workspace `
        node:24-bookworm-slim -- sh -lc '
          apt-get update &&
          apt-get install -y --no-install-recommends ca-certificates git &&
          npm install -g @openai/codex@0.148.0 &&
          exec codex
        '
      ```
    </CodeGroup>

    On first launch, choose Sign in with ChatGPT, Sign in with Device Code, or provide an API key. Browser-based sign-in happens on your host while the resulting Codex credentials are stored on the sandbox's root disk.

    <Tip>
      For an isolated workspace, or when using microsandbox cloud, replace `--mount-dir ./my-project:/workspace:rw` with `--copy-dir ./my-project:/workspace`.
    </Tip>
  </Step>

  <Step title="Start another session">
    After leaving Codex, return to the same sandbox and workspace with:

    ```sh theme={null}
    msb exec -t codex-demo -- codex
    ```

    The sandbox root disk retains the files under `/root/.codex`, including authentication, configuration, and session history.
  </Step>

  <Step title="Verify the installation">
    Exit the TUI and run:

    ```sh theme={null}
    msb exec codex-demo -- codex --version
    ```

    The pinned example prints `codex-cli 0.148.0`.
  </Step>

  <Step title="Review or export changes">
    With the default writable mount, changes are already in the host checkout. Review them inside the sandbox:

    ```sh theme={null}
    msb exec codex-demo -- sh -lc 'cd /workspace && git status --short && git diff --stat && git diff'
    ```

    If you chose the isolated `--copy-dir` alternative, create a patch inside the sandbox:

    ```sh theme={null}
    msb exec codex-demo -- sh -lc 'cd /workspace && git add -N . && git diff --binary > /tmp/codex.patch'
    ```

    Copy the patch to the host:

    ```sh theme={null}
    msb cp codex-demo:/tmp/codex.patch ./codex.patch
    ```

    Check that it applies cleanly before applying it:

    ```sh theme={null}
    git apply --check ./codex.patch
    ```
  </Step>

  <Step title="Clean up">
    Remove the sandbox:

    ```sh theme={null}
    msb rm -f codex-demo
    ```

    Removing the sandbox also removes its Codex credentials, configuration, and sessions. Changes made through the default workspace mount remain in the host checkout.
  </Step>
</Steps>

## Reference

* [Codex CLI](https://developers.openai.com/codex/cli/)
* [Codex CLI repository](https://github.com/openai/codex)