[m-hodges]

It fails the MU Puzzle¹ by violating rules:

To transform the string "AB" to "AC" using the given rules, follow these steps:

1. *Apply Rule 1*: Add "C" to the end of "AB" (since it ends in "B"). - Result: "ABC"

2. *Apply Rule 4*: Remove the substring "CC" from "ABC". - Result: "AC"

Thus, the series of transformations is: - "AB" → "ABC" (Rule 1) - "ABC" → "AC" (Rule 4)

This sequence successfully transforms "AB" to "AC".

¹ https://matthodges.com/posts/2025-04-21-openai-o4-mini-high-...

[invalidroot]

Nice writeup! This is the second post I've seen in the genre of "I've had a secret, personal benchmark for LLMs where the 'solution' requires questioning the premises, and o4-mini-high beats it." The first post I saw was about a chessboard and the prompt "mate in one:" https://x.com/KelseyTuoc/status/1912945346126417940

(Edited to remove direct spoiler for the MU-puzzle, in case people want to try it.)