Large language model
Claude Opus 5.5
Claude Opus 5.5 is a large language model released by Anthropic on 22 September 2026 as the first model in the Claude 5.5 family. It accepts text and images, has a 1 million token context window and is aimed at long-running agentic coding and knowledge work at a lower price than Claude Opus 5.
Last reviewed 28 Oct 2026 · by Anthropic
Facts at a glance
| Developer | Anthropic |
|---|---|
| Released | 22 September 2026 source |
| API name | claude-opus-5-5 source |
| Context window | 1,000,000 tokens source |
| Max output | 128,000 tokens source |
| Knowledge cutoff | June 2026 (reliable knowledge and training data) source |
| API price | $4 per 1M input tokens, $20 per 1M output tokens, $0.20 cache reads, $5 cache writes source |
| Retirement | Not sooner than 22 September 2027 source |
What Claude Opus 5.5 is used for
Anthropic positions Opus 5.5 for long and sprawling jobs such as codebase-wide migrations and audits, financial analysis and research reports. Thinking is adaptive and always on, with medium as the default effort on the Claude Platform. A Fast mode with up to 2.5 times the speed costs $8 per million input tokens and $40 per million output tokens. The model is sold through the Claude Platform, Amazon Web Services, Google Cloud and Microsoft Azure, and ships with cybersecurity, biology and anti-distillation safeguards similar to those on Claude Fable 5.1.
Questions people ask
- When was Claude Opus 5.5 released?
- Anthropic announced it and made it available on 22 September 2026.
- 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 per million, according to Anthropic's announcement.
- 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.