Study: 2,500 telltale phrases reveal text written by Claude Opus 5.5

Graphite compared 10,000 articles generated by Claude Opus 5.5 with 10,000 human-written pieces on the same topics. The model still carries over 2,500 tells, with phrases like "this matters because" appearing 146 times more often than in human writing, while "helps to understand" never appeared in human texts. Em dash overuse has nearly vanished: 0.015 per 1,000 words, a 99% drop from Opus 5.

• Opus 5.5 retains over 2,500 AI tells, fewer than earlier models
• "this matters because" appears 146 times more often than in human writing
• Em dashes nearly gone: 0.015 per 1,000 words, down 99% from Opus 5
• Mannered prose fell 37% but is still 1.6 times more common than in human texts