OpenAI Codex Agent vs. Devin: Which AI Engineer is Real?
The dream is simple: You write a prompt, and an AI builds the app.
For a long time, Devin (by Cognition) was the only serious player in this "autonomous software engineer" space. But OpenAI has finally entered the chat with Codex Agent.
So, which one actually works?
The Core Difference
Devin is an interface-first product. It gives you a dedicated browser, a terminal, and a "planner" view. It feels like watching a remote employee work.
Codex Agent is a reasoning-first product. It lives inside ChatGPT. You don't "watch" it work in the same way; you just get the result. It feels more like a really smart magic trick.
Use Case 1: Building a New App
I asked both to build a "Pomodoro Timer with a dark mode toggle and sound alerts."
Devin:
- Instantly spun up a react app.
- I saw it Google for "best react sound library."
- It hit a bug with the audio API, debugged it in the terminal, and fixed it.
- Result: A deployed, working app in 12 minutes.
Codex Agent:
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- "Thinking" for ~45 seconds.
- Spat out a complete artifact.
- I clicked "Preview" and it worked perfectly.
- Result: A working app in 6 minutes.
Winner: Codex Agent for speed. Devin for visibility.
Use Case 2: Refactoring a Legacy Repo
This is where things diverge.
Devin can connect to your existing GitHub repo, read 50 files, and "understand" the architecture. It takes time (sometimes hours), but it gets there.
Codex Agent struggles with massive context. If you feed it a huge repo, it often hallucinates imports or assumes a standard folder structure that you don't use. It’s getting better with o3, but it’s not accurate enough for enterprise-grade refactors yet.
Winner: Devin (by a mile).
Pricing Breakdown
| Feature | OpenAI Codex Agent | Devin |
|---|---|---|
| Cost | Part of ChatGPT Plus ($20/mo) | Custom / Seat-based (Expensive) |
| Model | codex-1 (o3) |
Proprietary (Cognition) |
| Environment | Ephemeral Sandbox | Persistent VM |
| Internet Access | Limited | Full |
The Verdict
If you are a Founder trying to build an MVP from scratch: Use Codex Agent. It's faster, cheaper (if you already have Pro), and the reasoning engine is smarter.
If you are an Engineering Team trying to automate maintenance tasks: Use Devin. The persistence and debugging visibility are essential for real-world codebases.
About Vibe Coding Team
Vibe Coding Team is part of the Vibe Coding team, passionate about helping developers discover and master the tools that make coding more productive, enjoyable, and impactful. From AI assistants to productivity frameworks, we curate and review the best development resources to keep you at the forefront of software engineering innovation.
