Funny, I find Codex to still be better at Coding than Opus or Fable.

I A/B tested on a whole array of prompts between Codex and Fable, and Fable almost always found that Codex had produced a better plan and covered more edge cases than it did itself.

For every problem I gave the exact same prompt to both models, then I had each analyze the other's output. For roughly 80% of the prompts, Fable acknowledged that Codex's output was an improvement on its own, for 20% the converse situation occurred.

There was one egregious case where Fable suggested deploying code which would have resulted in a production bug, an edge-case which Codex identified and proposed a fix.

Note: this is all for optimized Rust code designed to be highly CPU and memory efficient.

I do prefer Anthropic's models for any tasks with front-end/design work needed. But I don't do much of that kind of work usually.