Claude Opus 5 tops an internal writing benchmark at 2,817 Elo
RLanceMartin · x · 2026-07-26
An internal writing benchmark shared by WhatsAI puts Claude Opus 5 at #1 for editorial writing, with a score of 2817 Elo. The post says it jumped from #15 to #1 versus its predecessor when all thinking variants are considered, while keeping the same API price as Opus 4.8.
The interesting wrinkle is that effort level changes the result: at default effort, Opus 5 lands around #6; at max effort, it reaches the top spot after thinking for more than three minutes per script. The chart also shows it overtaking Claude Fable 5 and Kimi in this benchmark.
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