Claude Sonnet 5.5
Language modelCard summarizedThe best combination of speed and intelligence
Active (latest) · retires not before 28 Sep 2027● Re-checked 12 Oct 2026 · 95 facts · 0 corrections · 1 unconfirmedSource: System Card: Claude Sonnet 5.5 (148 pp)
Use it via API
Where to call it
- Claude API
claude-sonnet-5-5 - Amazon Bedrock
anthropic.claude-sonnet-5-5 - Google Vertex AI
claude-sonnet-5-5 - Microsoft Foundry / Azure
claude-sonnet-5-5
Supports
- Image input
- PDF input
- Structured outputs
- Reasoning control
- Tool calling
- Web search
- Prompt caching
- Batch API
Good for
- Agentic coding: large gains over Sonnet 5 (SWE-bench Pro 81.3% vs 63.2%)
- Professional knowledge work: GDPval-AA and AA-Briefcase close to Opus 5.5
- Healthcare: beats Opus 5.5 on HealthBench Professional
Overview
Sonnet 5.5
The best combination of speed and intelligence
- Cost
- $2.00 in
- Context
- 1M
- Input / output
- $2.00 / $10.00
- Max output
- 128K
- Knows up to
- June 2026
- Released
- 28 Sep 2026
Anthropic's latest Sonnet-class large language model. It significantly outperforms Claude Sonnet 5 across many domains and in a few areas rivals or exceeds Claude Opus 5.5, but is broadly less capable than Opus 5.5 and crosses no new RSP thresholds. p.2–3
claude-sonnet-5-5- Input / output per 1M
- $2.00 / $10.00
- Context window
- 1M
- Max output
- 128K
- Knows up to
- June 2026
- Reasoning
- Adaptive
- Weights
- Closed
About this card. A model card is the maker's own account of a model: what it's for, how it was trained and tested, and where it falls short. This page condenses Anthropic's System Card: Claude Sonnet 5.5. Every claim carries its source page.