Codex and Claude Code are both AI agents that do coding work, and both can be used from the terminal; the difference begins with which company's models and which working environment you commit to. For a small agency, the right choice is less about "which is better" and more about which tool fits your workflow. This article covers only the differences we could verify in the official documentation; because these tools change quickly, check the current docs for anything critical.
What are they?
Claude Code is Anthropic's coding agent. It reads your project folder, edits files and runs commands. Codex is OpenAI's coding agent, with a command-line tool (CLI), an IDE extension, an app and a web interface. Both work inside the project, beyond a chat window.
Where do they run?
- Claude Code: According to its official docs, it runs in the terminal, in IDE extensions (such as VS Code), in a desktop app and in the browser.
- Codex: Used through the terminal (CLI), an IDE extension, an app and a web interface (chatgpt.com/codex). The CLI is described as open source.
So in terms of surfaces they are close. Someone who likes working in the terminal will be comfortable in either.
How do they authenticate?
- Claude Code: You can sign in with a claude.ai account (for example a Pro or Max subscription), a Claude Console account, or through cloud providers (Amazon Bedrock, Google Cloud, Microsoft Foundry).
- Codex: You can sign in with your ChatGPT account or use an OpenAI API key.
Both offer two routes: sign in with an existing subscription, or connect with a pay-per-use API key. Which suits you depends on how often you use it.
Multi-agent support
Both support helper agents. In Claude Code you can define customizable subagents. According to OpenAI's documentation, Codex can also start subagents that work in parallel on specific jobs; the feature is offered in the Codex app and CLI. Because scope can change from version to version, do not build a workflow on it without trying it in your own setup.
Pricing model
We give no numbers here; prices and limits change often. The general model is this: both tools can be used through a subscription (with a usage limit) or through usage-based payment with an API key. Heavy agent use on a small team can hit limits, so check each company's own page for current prices and limits.
Comparison table
How should a small agency choose?
- Which subscription do you already have? If someone on the team already pays for one, trying that tool is the cheapest start.
- What kind of work? For long, multi-file, repetitive jobs, try both on the same task in your own project; model differences vary by task.
- Are your rules written down? Whichever tool you pick, the rules file determines a large share of quality.
- Who reviews? Both can make mistakes; a human to check the output is essential.
Three things that matter more than the tool
The tool debate often hides the real issue. In our experience, the results are decided by these:
- The rules file: If a project's design rules, do-nots and past mistakes are not written down, any agent will repeat the same errors.
- Permission boundaries: Think before giving an agent broad access to secrets, a live database or a deploy account. Read access first, then limited write access, is a safer start.
- Verification habit: A passing build does not mean the job is done. Checking in a real browser, measuring, and verifying content claims against sources is a discipline that does not depend on the tool.
So when you compare two tools, you are also testing your own way of working. A team with a settled routine keeps its speed when it switches tools; a disorganized team keeps producing errors even with the best tool.
How to run a trial
For one week, do the same small task with each tool separately: have it write a page component, find a bug, edit a piece of content. Note the time, the number of corrections and the result. Base the decision on results in your own work, not on someone else's benchmark table.
The limit of this comparison
The table above includes only points we could verify in the two companies' official documentation and announcements. We did not declare a winner on speed, code quality or error rate, because these vary by task, project and model version, and we have no data from running the two tools side by side on the same job. We plan to revisit this article as the tools are updated.
Using both together
Using the two tools together is possible: one writes the work while the other reviews the output. At Vinci Studio our main tool is Claude Code. We are evaluating Codex as a collaboration plan; we do not claim to use it, we plan to try it. One useful detail: our project also has an AGENTS.md file and CLAUDE.md imports it, so the rules live in one place. If you want to talk about your site, see our web design service, and for visibility after launch, our SEO·GEO·AEO service.
