Three AI coding agents walked into a terminal. That is not a joke setup — it is the current state of developer tooling in 2026. OpenAI has Codex. Anthropic has Claude Code. Google has Gemini CLI. I ran all three through the same tasks to see which one actually helps.
The Test Setup
I gave each tool five tasks: write a Python script from a description, refactor a messy function, add error handling, explain a legacy codebase, and fix a bug in a test suite. Same prompts, same project, timed from start to finish.
Claude Code
Claude Code impressed me most on refactoring and code comprehension. It read the whole project, understood the architecture, and made changes that fit the existing style. When I asked it to explain a 10-year-old PHP file, the answer was clearer than anything I have seen from the other two.
Downside: it is usage-priced, so heavy sessions cost real money. A day of intensive work ran me about $6.
Codex
Codex is fast. It generates code quicker than the others, and it handles boilerplate well. For greenfield projects — starting from scratch — it gets you to a working prototype fastest.
The trade-off: Codex is less careful. It writes code that works, but sometimes in a way that is hard to maintain. You need to review its output more closely.
Gemini CLI
Gemini CLI is the newest and the most polished in terms of UX. The terminal interface is clean, and it handles long conversations well. Its strength is breadth — it knows a huge range of libraries and frameworks.
In my testing, Gemini CLI was the weakest on deep project understanding. It is excellent for quick tasks and one-off questions but less suited to large refactors.
Which One Wins?
There is no single winner. It depends on the job. For refactoring and understanding existing code: Claude Code. For rapid prototyping from scratch: Codex. For general quick help with good UX: Gemini CLI.
I personally keep Claude Code for the hard problems and Codex for fast generation. That combination covers most of what I do.