Honestly I think Claude Code enjoyed an "accidental" success much like ChatGPT; Anthropic engineers have said they never though this thing could catch on.

But being first doesn't mean you're necessarily the best. Not to mention, they weren't the first anyway (aider was).

I'm building a product on the Claude Agent SDK, and it is the best in a specific way.

Codex and Open Code are competition for coding, but if we talk about an open-ended agentic harness for doing useful work... well it was bad enough a year ago I'd consider anyone even claiming one exists to be a grifter and now we have one.

And while being first might not matter, I think having both post-training and the harness being developed under the same roof is going to be hard to beat.