We analyzed how @claudeai's writing has changed from Fable 5 to Fable 5.1 across tens of thousands of high-reasoning Text Arena outputs. Overall, Fable 5.1 by @AnthropicAI uses fewer agreement openers, fewer em dashes and less wording like “honestly” and “frankly”, while its answers have grown longer. Compared with Fable 5: – Agreement openers such as “yes” and “exactly” are 58% less common, appearing in 0.99% of responses versus 2.35%. – Honesty wording such as “honestly” and “frankly” falls 45% per 1,000 words. – Em dashes fall 32% per 1,000 words. It has also shifted some patterns in another direction, e.g.: semicolons increase 63% per 1,000 words. Fable 5.1 still writes long answers, with sentence length and clause frequency close to Opus 5: – Median response length rises 30% from Fable 5: 319 → 414 words. – That remains 21% shorter than Opus 5’s 525 words. – Its sentence-length measure is slightly higher than Opus 5’s: 12.54 versus 12.20 words per sentence. Other familiar patterns also become less common compared with Fable 5: – Stock phrases such as “load-bearing” fall 20% per 1,000 words. – Hedges and caveats such as “perhaps” and “arguably” fall 36% per 1,000 words. – Praise and validation appear in 1.98% of responses, down from 3.17%. Long content words fall from 42.6% to 38.6%, while abstract nouns fall 25%, from 4.39 to 3.28 per 100 words. Let us know what you think in the comments.