Claude Opus 5.5: 40% Cheaper Than Opus 5, 66.4% on Terminal-Bench 4.0

Anthropic released Claude Opus 5.5, the first model in the new Claude 5.5 family. It performs at the level of Claude Fable 5.1 on most work and costs 40% less to run than Opus 5. Input and output tokens are priced at $4 and $20 per million respectively — 20% less than Opus 5 — while cache reads, which Anthropic says make up most agentic and coding work costs, drop to $0.20 per million, a 60% reduction. Output generates more than 30% faster than Opus 5.

Benchmarks

Opus 5.5 leads across agentic coding, computer use, and knowledge work:

• Terminal-Bench 4.0: 66.4% (vs 55.8% Fable 5.1, 52.3% Opus 5, 57.9% GPT-6 Astra, 37.3% GPT-5.6 Sol)
• FrontierCode v1.1 (Main): 54.4% (Fable 5.1: 50.3%, Opus 5: 48.0%)
• CursorBench 4.0: 57.8% (Fable 5.1: 51.8%, Opus 5: 46.6%)
• GDPval-AA v2.1: 1846 (Fable 5.1: 1735, Opus 5: 1708)
• AutomationBench: 40.0% (Fable 5.1: 31.4%, Opus 5: 26.9%)
• Humanity's Last Exam: 67.7% with tools (Fable 5.1: 65.6%, Opus 5: 63.6%)
• Terminal-Bench-Science 0.1: 58.7% (Fable 5.1: 52.6%, Opus 5: 29.0%, GPT-6 Astra: 64.6%)

Anthropic notes benchmark margins have become a less reliable guide to real-world differences at this level, and that the gap between Opus 5.5 and Fable 5.1 is narrower in practice than the scores suggest.

Reported workloads

One tester completed a 680,000-line code migration in under a day. In an internal test to cut load times across every page of a web app, Opus 5.5 succeeded 39 of 40 times — Opus 5 made smaller improvements that also altered app behavior. Another tester had several Claude models build a game from a single prompt; Opus 5.5 scored highest on graphics and polish.

Safety and verification

Opus 5.5 posts the best scores to date on Anthropic's automated behavioral audit, a suite that tests Claude across thousands of simulated scenarios. It is less likely than recent models to take hard-to-reverse actions or act outside given boundaries, and is more resistant to prompt injection than Opus 5. Testing now covers longer tasks, impossible tasks, and scenarios modeled on real incidents. Because it's comparable to Claude Mythos 5.1 in biology and cybersecurity, Anthropic is deploying it with safeguards similar to Claude Fable 5.1.

Vetted organizations can apply to the Life Sciences Verification Program for biology research use; the Cyber Verification Program expands in coming weeks for verified practitioners.

Limits and availability

Five-hour usage limits on Pro, Max, Team, and seat-based Enterprise plans are increasing. Subscription users get a rate limit reset that can be saved and used at will. Claude Sonnet 5.5 and Claude Haiku 5.5 follow in the coming weeks with similar improvements to performance, efficiency, and safety.