Opus 4.8 Thinking keeps deteroriating on Hard Prompts English in LMArena (again)

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model-performance benchmark hard-prompts opus-thinking lma-arena degradation

Summary

Opus 4.8 Thinking continues to deteriorate on the Hard Prompts English benchmark on LMArena, scoring 23 points lower than Opus 4.6 Thinking, which retains the top spot.

Opus 4.6 Thinking keeps the #1 spot. Followed by Opus 4.7 Thinking (-15 points). Lastly, Opus 4.8 Thinking (-23 points compared to 4.6 Thinking). [https://arena.ai/leaderboard/text/hard-prompts-english](https://arena.ai/leaderboard/text/hard-prompts-english) As a non-coder, I find the Hard Prompts (English) benchmark on LMArena to be the one that best matches my experience at work. It's probably more immune to benchmaxxing. Simple Bench also shows that 4.6 is the best model in the Opus family.
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