Our take

Shines on background multi-task coding — assign several issues and it works them in parallel.

What it is

OpenAI Codex is OpenAI's cloud-based coding agent. It can take a task, run it in an isolated cloud sandbox, and return a patch with a description of what changed. A standout feature is parallelism: you can throw several issues at it at once and it works them in parallel sandboxes.

Best for

Delegate several bug fixes in parallel
Background work on long-running tasks
Generate a PR from a written task description

Pros

Runs in cloud sandboxes — your machine is free
Parallelism: multiple tasks at once
Bundled with ChatGPT Plus/Pro

Cons

Slower turn-around than local agents for small fixes
Quality varies with task complexity

Quick start

Open ChatGPT → click "Codex" in the sidebar (Plus / Pro / Team tiers).
Connect your GitHub repo (one-time OAuth), pick a branch, click "Create task".
Type the task: "Add unit tests for src/orders/ — open a PR if lint + tests pass."
Watch the Cloud VM logs live, or background it and check the PR when ready.
Stack multiple tasks — Codex runs them in parallel sandboxes, so 6 PRs land roughly at once.

Sample input / output

Input

Tasks submitted in one batch:
  - "Tighten input validation in src/api/users/* and add zod schemas"
  - "Replace lodash.get with native optional chaining across utils/"
  - "Update package.json to drop unused deps"

Output

~15 min later, 3 PRs opened:
  - #451: zod validation (+12 files, all tests pass)
  - #452: lodash cleanup (-420 lines across 38 files, no behavior change)
  - #453: dep cleanup (-340 KB bundle, lockfile regenerated)
Each PR has its own focused diff and a one-line summary from Codex.

Benchmarks

Inclusion Bundled with ChatGPT Plus ($20) / Pro ($200) / Team

Sandbox isolation Each task runs in its own cloud VM — no local env

Parallelism Multiple tasks at once across separate branches

Underlying model codex-1 (OpenAI custom); some GPT-4o class fallback

Pricing

Included with ChatGPT Plus/Pro

Underlying models

codex-1 (OpenAI custom), GPT-4o class

Should you pick this?

Pick it if You already pay for ChatGPT Plus/Pro and have a backlog of small coding tasks — Codex runs them in parallel while you keep coding locally.

Skip it if You want local execution and full control over the model — Aider, Cline, or Claude Code are local-first. For deep reasoning on long agent tasks, Devin is the deeper (and pricier) pick.

OpenAI Codex