Claude vs Codex

Claude Code and Codex are not the same thing. Here's the one difference that matters by default:

Claude Code is local-first: the agent runs on your machine (model inference still happens in the cloud, same for both).

Codex is hybrid: cloud-first by default (agent runs in OpenAI's cloud sandboxes), with a full local CLI.

Both can technically be configured to behave like the other. But defaults shape the experience.

1.      Claude Code → sees your real files, runs your real tests, uses your local tools.

2.      Codex Cloud → runs in a cloud sandbox, faster to start, zero setup, parallel tasks.

3.      Codex CLI → runs locally like Claude Code.

When to use Claude Code:

1. Projects that need full access to your codebase
2. You want to test on YOUR setup, not a sandbox.
3. Long sessions where context matters.

When to use Codex:

1. Quick tasks you want done fast.
2. You don't need local access.
3. You want multiple tasks running at once.

Most people pick one and ignore the other. Now you know when to use each.