Claude Opus 5 'Completely Useless Today': Developer Slams Model for Year-Old-Level Mistakes

jasonkneen · x · 2026-09-16

Developer Jason Kneen reports that Claude Opus 5 is "cooked" and "completely useless" today, making stupid mistakes he'd expect from a model a year or so old. The complaint adds to recurring user concerns about quality fluctuations in frontier model serving.

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