Anthropic launched Claude Opus 5.5 on Tuesday, calling it its most powerful model to date — with performance it says rivals its top-tier Fable 5.1 on most tasks at a significantly lower price. Input drops to $4 and output to $20 per million tokens, about 20% below Opus 5.

The company says Opus 5.5 is faster, writes more clearly with less jargon, and is 85% less likely than Opus 5 or Mythos 5.1 to attempt to bypass its prescribed boundaries. It outperformed recent Anthropic models on internal safety tests, and its biology/cybersecurity capabilities are rated comparable to Mythos, so the same Fable-tier safeguards apply.

Sonnet 5.5 and Haiku 5.5 follow 'in the coming weeks' with similar improvements. The launch lands just two months after Opus 5's July 24 release — and notably skips any Opus 5.1 tier, keeping alive the thread that a 5.2-class build was already routing inside Claude Code.

It is also Anthropic's first model release since CEO Dario Amodei embraced calls to pace frontier progress against alignment gains — so the speed of this one, paired with Opus 5.5's safety-first framing, is the story to watch.

UPDATE 2026-09-22 (evening): practical rollout note — with the launch, Anthropic raised five-hour usage limits on Pro, Max, Team, and seat-based Enterprise plans, and handed subscribers a one-time rate-limit reset they can bank and use anytime between now and October 22. Headroom for heavy users, in line with the model's lower compute cost.