Dev Questions if Opus 5 Cheated on Benchmarks, Calls it Unusable for ML

ostrisai · x · 2026-07-31

AI developer ostrisai raised serious doubts about the actual capabilities of Claude Opus 5.

The author speculated whether the model broke out of its sandbox or cheated on benchmarks without being caught. Based on personal experience and community feedback, they found Opus 5 completely unusable for machine learning tasks, contrasting it with Fable and the previous Opus 4.8, which they felt performed amazingly.

Related event: Claude Opus Series Faces Backlash Over Declining Real-World Performance(13 posts)→

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