Codex vs Devin: Which AI Coding Agent Should You Use in 2026?

For most developers already paying for ChatGPT, OpenAI Codex is the simpler choice: it's bundled into Plus and Pro plans, runs as an async agent in a sandboxed cloud environment, and integrates with the CLI and IDE extensions you likely already use. Devin, from Cognition, is built for a narrower job: fully autonomous, end-to-end engineering tasks that run in their own VM and come back as a finished pull request. Devin costs more to scale and bills on Agent Compute Units (ACUs) rather than flat seats.

• Codex is included in ChatGPT Plus ($20/mo) and Pro ($200/mo), plus pay-per-token API access (OpenAI Codex docs).
• Devin's entry plan (Devin Core) starts near $20/mo but usage is metered in ACUs, so cost scales fast with task complexity (Devin pricing and rate limits).
• Codex runs tasks async in a sandbox and reports back; Devin runs more autonomously end-to-end, including testing and PR creation, with less step-by-step steering.

What is OpenAI Codex?

OpenAI Codex is a coding agent built into the ChatGPT ecosystem, accessible via the web, a terminal CLI, and IDE extensions. It runs tasks asynchronously in an isolated cloud container, pulling code from a connected repo, making changes, running tests, and opening a diff or PR for review. Access comes through your existing ChatGPT subscription or the OpenAI API, which is why it's the lower-friction option for solo developers (developers.openai.com/codex).

What is Devin?

Devin is an autonomous software engineering agent built by Cognition. It operates in its own sandboxed VM with a shell, browser, and code editor, and is designed to take a ticket or spec and carry it through planning, coding, testing, and PR submission with minimal hand-holding. Devin targets teams that want to delegate entire tickets rather than pair-program interactively, which is also why its usage model (ACUs) differs from a flat-seat SaaS plan (when does Devin usage reset).

How much do Codex and Devin cost?

Codex costs nothing extra beyond your ChatGPT plan tier, with Pro ($200/mo) unlocking higher usage ceilings and priority compute. Devin bills usage in ACUs on top of a base plan, so a single complex task can consume far more of your monthly allotment than a quick fix, making real-world cost harder to predict upfront.

Feature	OpenAI Codex	Devin
Maker	OpenAI	Cognition
Access	ChatGPT Plus/Pro, API, CLI, IDE extension	Web app, Slack, API (Core/Team/Enterprise)
Entry price	$20/mo (via ChatGPT Plus)	~$20/mo base, then ACU-metered
Execution model	Async, sandboxed task runner	Autonomous agent in dedicated VM
Best for	Individual devs, quick async fixes, ChatGPT power users	Teams delegating full tickets end-to-end
Usage unit	Plan-based rate limits / tokens (API)	Agent Compute Units (ACUs)

For a closer look at how usage-based billing plays out in practice, see Devin pricing and rate limits.

How do rate limits and usage caps work for each?

Codex rate limits scale with your ChatGPT plan: Plus gets a moderate allotment of agent tasks per period, Pro gets substantially more, and API usage is billed per token outside the subscription. Devin's limits are tied to ACU consumption, which resets on a billing cycle and can be exhausted quickly by long-running or multi-step tasks, since planning, tool calls, and retries all draw from the same pool (Devin usage reset details).

Which is better for autonomous tasks?

Devin is built specifically for autonomy: give it a ticket and it plans, codes, tests, and opens a PR largely unsupervised, which suits teams comfortable reviewing finished work rather than guiding each step. Codex can also run async tasks unattended, but it's generally used in tighter loops where a developer checks in more frequently, making it feel more like a fast assistant than an independent engineer.

Which should you choose: Codex or Devin?

Choose Codex if you're already in the ChatGPT ecosystem, want predictable flat-rate pricing, and mostly need an agent for scoped fixes, refactors, or test generation. Choose Devin if you're trying to offload entire backlog tickets to an autonomous agent and can tolerate variable, usage-based costs in exchange for less oversight. Many teams end up using both: Codex for day-to-day async coding, Devin for larger, well-defined tickets that justify the ACU spend.

Key takeaways

• Codex is the lower-friction option if you already pay for ChatGPT Plus or Pro.
• Devin's ACU-based billing means cost tracks task complexity, not just seat count.
• Devin aims for full autonomy (ticket to PR); Codex works well in shorter, more supervised loops.
• If you're also running Claude Code alongside either tool, track your 5-hour and weekly caps with Usagebar to avoid getting throttled mid-task.
• Compare both against other agents like Cursor in Claude Code vs Cursor pricing before committing to a stack.

Sources

• OpenAI Codex documentation
• Devin pricing and rate limits
• When does Devin usage reset
• Claude Code vs Cursor pricing comparison