Claude Opus 5.5
Released
Claude Opus 5.5 is an AI model released by Anthropic on Tuesday, Sep 22 2026, 21 days after Claude Mythos 5.1. It has a 1M token context window. Benchmark results (shown below) cover CheatBench, CursorBench 4.0, FrontierCode v1.1 (Main), Next.js Evals, Supabase Evals, Humanity's Last Exam, and 10 more.
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API pricing
- InputWhat you pay for everything you send the model — your question, plus any documents or earlier conversation you include with it.
- $4.00
- Cached inputA reduced rate for text you send over and over. If every request starts with the same instructions or the same document, the provider keeps a copy ready and charges less to read it again.
- $0.20
- 5 min cache writeA one-off charge for storing text so later requests can reuse it at the cheaper cached rate. This option keeps it for five minutes.
- $5.00
- 1 hr cache writeA one-off charge for storing text so later requests can reuse it at the cheaper cached rate. This option keeps it for an hour, so it costs more than the five-minute one.
- $8.00
- OutputWhat you pay for the text the model writes back. It is normally the dearer half: producing an answer costs more than reading one.
- $20.00
- Adaptive thinking is always on.
- Cache reads are priced at 0.05x the base input price on this model, against 0.1x on Opus 5.
- Anthropic also publishes a Fast mode for this model at exactly twice the standard rate — $8.00 per million input tokens and $40.00 per million output — on the Claude API only, with up to 2.5x the output speed.
Available from
| Amazon Bedrock | — | — | $4.00 | $20.00 | 1M |
|---|---|---|---|---|---|
| Anthropic | — | — | $4.00 | $20.00 | 1M |
| Azure | global | — | $4.00 | $20.00 | 1M |
| Claude Platform on AWS | — | — | $4.00 | $20.00 | 1M |
| global | — | $4.00 | $20.00 | 1M | |
| Amazon Bedrock | eu-west-1 | — | $4.40 | $22.00 | 1M |
| Amazon Bedrock | us-east-1 | — | $4.40 | $22.00 | 1M |
| Azure | us | — | $4.40 | $22.00 | 1M |
| eu | — | $4.40 | $22.00 | 1M | |
| us | — | $4.40 | $22.00 | 1M | |
| Anthropic | — | fast | $8.00 | $40.00 | 1M |
Benchmarks
Coding
Terminal & CLI
Agentic & tool use
Reasoning & science
Knowledge work
Multimodal
Robustness
Community preference
Source: CursorBench, retrieved 28 September 2026 · Source: BenchLM, retrieved 28 September 2026 · Source: CheatBench, retrieved 25 September 2026. Other sources are identified on the linked benchmark pages.
Compare Claude Opus 5.5 with
Suggested comparisons
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Claude Opus 5.5, released September 22, 2026, succeeded Claude Opus 5 at Anthropic's Opus tier eight and a half weeks after it and three weeks after Claude Fable 5.1 took the top of the lineup. It arrived with a price cut: $4 per million input tokens and $20 per million output against Opus 5's $5 and $25, with cache reads at $0.20 per million, less than half Opus 5's $0.50, and cache writes at $5. Its launch table did something no earlier Opus release had done: it put the Opus model ahead of the Fable model above it on every board the two shared. At launch it scored 66.4% on Terminal-Bench 4.0 against Fable 5.1's 55.8% and Opus 5's 52.3% under Anthropic's own harness, 54.4% on the main split of FrontierCode v1.1, a GDPval-AA v2.1 Elo of 1846 for knowledge work where Fable 5.1 sat at 1735, and 67.7% on Humanity's Last Exam with tools. All of those were the best published scores at the time.
The rest of the card was agentic breadth. Opus 5.5 reached 81.8% partial completion on OSWorld 2.0 computer use, 89.0% on Chartography with tools and 58.7% on Terminal-Bench-Science 0.1, double Opus 5's 29.0% and six points behind GPT-6 Astra's 64.6%. On AutomationBench, run by Zapier during early access, it scored 40.0%, a point and a half short of GPT-6 Astra's 41.4% and up from Opus 5's 26.9%. Anthropic ran the table with production safeguards enabled, so cybersecurity tasks the classifiers intercepted were completed by Claude Opus 4.8 and biology and frontier-LLM-development tasks by Claude Opus 5, which it said likely lowered the reported numbers. The Terminal-Bench 4.0 result was reported at xhigh effort with a standard error of ±2.6 points; every other Claude figure used adaptive thinking at max effort.
Frequently asked questions
Claude Opus 5.5 was released by Anthropic on Tuesday, Sep 22 2026.