Model · Multimodal language model
Claude Sonnet 5.5
The second model of Anthropic's Claude 5.5 family, released September 28, 2026, a text-and-image model with 1M-token context and adaptive thinking, served through the Claude API, Amazon Bedrock, Google Cloud, Microsoft Foundry, and Claude Platform on AWS.
- Developer
- Anthropic
- Distribution
- Developer API · Third-party hosting
- Artifact licensing
- Proprietary access
- License scope
- Reviewed release artifacts and mandatory terms; not an assessment of training code or training data openness.
- Licenses
- Anthropic Commercial Terms of Service
- Boundary
- This record represents the Claude Sonnet 5.5 release of September 28, 2026, the second model of the Claude 5.5 family with the pinned claude-sonnet-5-5 API identifier and per-platform IDs on Amazon Bedrock, Google Cloud, Microsoft Foundry, and Claude Platform on AWS. The reviewed Sonnet 5, Sonnet 4.6, and Opus 5.5 lines, the unlaunched Claude Haiku 5.5, and independent hosts are separate boundaries.
Risk statements
“CB-1 and Autonomy-1” · Precautionary
We do treat Sonnet 5.5 as meeting our CB-1 and Autonomy-1 thresholds and apply the corresponding mitigations from our RSP.
- Risk areas
- Biological or chemical · Autonomy
- Covers
- The model itself
Read the developer's statement ↗ · 2026-10-07 · Research confidence: Medium
Anthropic names this release against “CB-1 and Autonomy-1” in biological or chemical and autonomy capability, as a precaution. The statement covers the model itself. This is the developer's own statement, not an Atlas risk rating.
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