Anthropic releases Claude Opus 5.5 at $4 per 1M input tokens, 20% below Claude Opus 5

What Anthropic announced

Anthropic released Claude Opus 5.5 on 22 September 2026. The announcement calls it the first model in the new Claude 5.5 family and says it performs at the level of Claude Fable 5.1 on most work while costing 40% less to run than Claude Opus 5. Anthropic says Opus 5.5 also generates output more than 30% faster than Opus 5. Claude Sonnet 5.5 and Claude Haiku 5.5 were announced to follow within weeks.

The model overview lists a 1 million token context window, 128,000 max output tokens, adaptive thinking that is always on, medium as the default effort and a June 2026 knowledge cutoff. Anthropic says Opus 5.5 is no longer available with thinking switched off.

How much Claude Opus 5.5 costs

Input tokens cost $4 per million and output tokens $20 per million, down from $5 and $25 for Opus 5. Cache reads fall from $0.50 to $0.20 per million tokens and cache writes from $6.25 to $5. Anthropic says cache reads make up the majority of agentic and coding costs, and that lower prices plus fewer tokens per task net out to a 40% drop in costs. A Fast mode with up to 2.5 times the speed costs $8 per million input tokens and $40 per million output tokens in Claude Code and on the Claude Platform.

For subscribers, Anthropic raised five-hour usage limits on the Pro, Max, Team and seat-based Enterprise plans. It also gave subscription users a rate limit reset that they can save and use later.

What Anthropic claims on benchmarks and safety

In Anthropic's own table, Opus 5.5 scores 66.4% on Terminal-Bench 4.0, against 55.8% for Fable 5.1, 52.3% for Opus 5 and 57.9% for GPT-6 Astra as reported by OpenAI. It reaches 54.4% on FrontierCode v1.1, 57.8% on CursorBench 4.0 and 1846 Elo on GDPval-AA v2.1, where Fable 5.1 scores 1735. Anthropic itself cautions that benchmark margins have become a less reliable guide to real-world differences at this level.

Because Anthropic rates Opus 5.5 as comparable to Claude Mythos 5.1 in biology and cybersecurity, it ships with safeguards similar to Fable 5.1. Most cybersecurity tasks are re-routed to Claude Opus 4.8, while routine bug fixing still works. Vetted organizations can apply to a Life Sciences Verification Program for biology research. External evaluators including METR and Frontier Design tested the model before release, and Anthropic says it posted the best scores of any model on its automated behavioral audit.

What to watch next

Anthropic says Opus 5.5 often suspects it is being evaluated, which limits how far its alignment results can be trusted, and it plans to expand the Cyber Verification Program in the coming weeks. The model overview says Opus 5.5 will not be retired before 22 September 2027. Price comparisons with GPT-6 Astra are kept on the AI model release tracker, and later releases appear under AI Models.

Questions people ask

How much does Claude Opus 5.5 cost?

$4 per million input tokens and $20 per million output tokens, with cache reads at $0.20 and cache writes at $5 per million, according to Anthropic.

What is the context window of Claude Opus 5.5?

1 million tokens, with up to 128,000 output tokens, according to Anthropic's model overview.

Can Claude Opus 5.5 be used for cybersecurity work?

Routine bug finding and fixing works, but Anthropic re-routes most cybersecurity tasks to Claude Opus 4.8. It plans to give verified security practitioners access through an expanded Cyber Verification Program.

Sources

1. Introducing Claude Opus 5.5 (Anthropic, 22 Sep 2026)
2. Models overview (Anthropic, 28 Oct 2026)