I’ve spent most of this site on independent, BYOK tools — Cline, Aider, OpenCode, that whole world. But the three biggest labs each ship their own terminal-native coding agent too, and they’re worth comparing on their own terms, because the tradeoffs are genuinely different from the community tools.
Claude Code is Anthropic’s own terminal agent, and it’s the one most often recommended as a migration target in the alternatives posts I’ve written on this site — for Roo Code refugees and people who lost Gemini CLI access alike. It isn’t open source; the public repo is issues and documentation, not the actual client. What you’re actually paying for is tight integration with Anthropic’s own models and a genuinely well-built terminal experience — no provider-juggling, because it only does one provider, but that one provider gets first-party support the day a new model ships.
Codex CLI is OpenAI’s answer, and unlike Claude Code, it’s genuinely open source — released with real BYOK support if you want to point it at something other than OpenAI’s own models, alongside first-party support for GPT and the o-series reasoning models. It sits in an interesting middle position: open enough to audit and self-host the client, but still clearly built as the reference way to use OpenAI’s own models specifically.
Gemini CLI is the cautionary tale of the three. It was genuinely open source too — Apache 2.0, 107k+ stars — and for a while the obvious pick if you wanted a fully open, zero-cost terminal agent running frontier Gemini models. Then Google cut off free individual access in June, pushing everyone toward the closed-source Antigravity CLI instead. The repository is technically unchanged and still Apache 2.0. What disappeared was the free backend that made the open code worth running day to day — a distinction I keep coming back to on this site, because “the code is open” and “the tool is usable for free” turned out to be two completely separable promises.
The practical read: if you want first-party support for a specific lab’s frontier models and don’t mind being locked to one provider, Claude Code and Codex CLI both do that well, with Codex CLI having the edge if you specifically want to audit the client or occasionally point it elsewhere. Gemini CLI is worth knowing about mostly as the clearest example yet of what happens when “open source” and “free to run” get treated as the same promise — they’re not, and the gap between them is exactly where the risk lives.
