Claude Opus 5.5
Claude Opus 5.5 is aimed at extended coding and knowledge work. It supports vision and computer-use workflows, but several important limits differ between ordinary requests and the batch service.
The larger output limit is not the default
The 300,000-token output option belongs to Message Batches and requires a beta header. Do not size an interactive request around that number. The regular maximum is lower.Claude Opus 5.5 reference
Short prompts do not qualify for caching
Opus 5.5 requires at least 512 prompt tokens for caching. The service also prices cache writes, reads and ordinary input separately.Claude Opus 5.5 reference
Make large code changes reviewable
Practical guidance. For a refactor, ask for the intended behavior, changed interfaces and verification evidence. Keep business requirements explicit. A model can produce a coherent explanation while still missing an edge case, so review the actual change against the requirement.
Specifications & access
| Detail | Value and conditions |
|---|---|
| Launch date | |
| Access | API |
| Model identifiers | claude-opus-5-5 |
| Context window | 1,000,000 tokens Context limit Claude Opus 5.5 reference |
| Maximum output | 128,000 tokens Ordinary maximum output Claude Opus 5.5 reference |
| Maximum output | 300,000 tokens Message Batches API with output-300k-2026-03-24 beta header Claude Opus 5.5 reference |
| Input price | 4 USD per million tokens Standard input rate Claude Opus 5.5 reference |
| Output price | 20 USD per million tokens Standard output rate Claude Opus 5.5 reference |
| Thinking control | Always on; adjust depth through effort rather than turning it off.Claude Opus 5.5 reference |
| Default effort | mediumClaude Opus 5.5 reference |
| Minimum cacheable prompt | 512 tokensClaude Opus 5.5 reference |
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