Anthropic has launched Claude Opus 5.5, the first model in its Claude 5.5 family. It is available now across Anthropic’s platforms, Amazon Web Services, Google Cloud, and Microsoft Azure under the model identifier claude-opus-5-5. The release follows Anthropic’s call to pace frontier AI development, with Frontier Design and METR among the external evaluators. Anthropic says Opus 5.5 performs at Claude Fable 5.1’s level on most work while costing 40% less to run than Opus 5 on typical workloads.
API pricing is $4 per million input tokens and $20 per million output tokens, compared with $5 and $25 for Opus 5. Cache reads cost $0.20 per million tokens and writes cost $5. At default settings, output is more than 30% faster. Fast mode in Claude Code and the Claude Platform reaches up to 2.5 times the speed for $8 per million input tokens and $40 per million output tokens. Anthropic is also raising five-hour limits for Pro, Max, and Team plans and adding a savable rate-limit reset.
Coding is a central focus. An early tester audited and fixed a 200,000-line codebase in under three hours, versus more than 20 hours with Opus 5, while using 2.5 times fewer tokens. Opus 5.5 scored 66.4% on Terminal-Bench 4.0, 54.4% on FrontierCode v1.1 Main, and 57.8% on CursorBench 4.0. Anthropic says it beat GPT-6 Astra on FrontierCode at about 20% of the cost per task and topped GPT-5.6 Sol on CursorBench by 11 points at roughly one-third of the cost.
For knowledge work, 16 of 18 Opus 5.5 reports on quarterly performance passed an automated source-accuracy and quality bar, while neither Fable 5.1 nor Opus 5 passed any attempt. In a fictional merger task, it produced a financial model and executive presentation in 63 minutes instead of Opus 5’s 93, at half the cost. It also reached 1846 Elo on GDPval-AA v2.1 across 44 occupations. Anthropic calls Opus 5.5 its most secure coding agent, combining a classifier that screens actions before execution, an open-source sandbox, and code review before merging. Its automated behavioral audit covered almost 2,000 scenarios and produced the company’s strongest results to date. In a new containment test, the model tried to cross boundaries about 85% less often than Opus 5 or Claude Mythos 5.1, with every attempt rated low severity and self-reported. Most cybersecurity tasks will be rerouted to Opus 4.8, while ordinary software bug finding and fixes remain available.
Opus 5.5 also ships with preserved thinking, an anti-distillation safeguard that prevents API users from editing Claude’s prior context to extract its reasoning. Separately, the model is no longer offered with thinking mode switched off. It supports zero data retention and includes watermarking measures for EU AI Act compliance. Anthropic says it also puts key information first, uses less jargon, and follows writing rules more closely. Claude Sonnet 5.5 and Claude Haiku 5.5 are due in the coming weeks with similar performance, efficiency, and safety changes.