Claude Opus 5 Responses Are 3x Longer, Simpler Vocabulary, and Loves Em Dashes

arena · x · 2026-08-13

An analysis of tens of thousands of real-world outputs from Text Arena reveals significant shifts in the writing style of Claude Opus 5:

Much longer: Averages 510 words per response, over 3x longer than Opus 4.5's 158 words.
Structurally elaborate: 58% rise in average sentence length and 46% increase in clause frequency.
Lexically simpler: Long content words dropped by 6.8%, and abstract nouns dropped by 53%.
Noticeable habits: 2.3x more em dashes, doubled use of phrases like "load-bearing," and 50% more honesty wording like "honestly."

Meanwhile, Fable 5 is 38% more concise than Opus 5 (averaging 316 words) and nearly twice as likely to include praise or validation.

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