Claude Opus 5.5 follows your writing rules more closely
Is Claude Opus 5.5 better for marketing writing?
Anthropic says Opus 5.5 costs 40% less to run than Opus 5, writes more clearly and follows the user’s writing rules.
14 October 2026 · By Mary-Anne Da’Marzo
Your written rules now do more of the work. Make them good.
Anthropic released Claude Opus 5.5 on 22 September. It says the model costs 40% less to run than Opus 5 on typical work, writes its answers more than 30% faster, puts key information first and follows the user’s writing rules. Sonnet 5.5 followed on 28 September.
For anyone executing with AI, the headline isn’t the speed. It’s the rules. A model that follows your rules more closely rewards whoever wrote the best rules. Vague rules get you polished, generic copy. Specific rules get you copy that sounds like you.
That’s exactly what an AI rulebook inside a B.R.A.I.N.™ is for: your voice, your words, the ones you never use and the customer you’re talking to, written down so every model reads the same thing.
Try this this week
- Write your ten most important writing rules in one document
- Run the same brief through your current model and Opus 5.5, then compare
- Add one rule for every mistake you spot, and run it again
Here are my brand’s writing rules: [paste]. Rewrite the draft below so it follows every rule. Then list each rule you applied and one place you weren’t sure. Draft: [paste]
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14 October 2026 · via TechCrunchB.R.A.I.N.™ opens on 1 December with three tracks
Join the waitlist now to be first in when the doors open.
14 October 2026