I ran Claude Code, Codex, and Cursor on the same AI model, and the tool mattered more than I expected

I write about AI coding agents a lot, and somewhere along the way I'd decided the model was doing all the heavy lifting. Swap Claude Code for Codex or Cursor, keep the same brain underneath, and you should get the same work back. So I put that to the test. I gave all three Claude Sonnet 5.5 at high reasoning, the same buggy WebSocket proxy that feeds my Kindle data from Home Assistant, 30 minutes, and $10 each. Every one of them scored a perfect 16 out of 16 on the final code, but that's the last thing they had in common. You'd think that choosing the model would be the easy part, but it turned out to be more complicated than I expected.

First reported by XDA Developers. This page is a short excerpt; the full text is theirs.