Claude Sonnet 5 / 5.5
by Anthropic — the Sonnet tier of the Claude family: “the best combination of speed and intelligence” (Anthropic’s wording). Sonnet 5.5 is the recommended Sonnet and the replacement Anthropic names for deprecated Sonnet 4.5.
Versions
| Sonnet 5.5 (current) | Sonnet 5 (legacy) | |
|---|---|---|
| Released | 2026-09-28 | 2026-06-30 |
| API ID | claude-sonnet-5-5 | claude-sonnet-5 |
| Knowledge cutoff | Jun 2026 | Jan 2026 |
| Retirement | not sooner than 2027-09-28 | not sooner than 2027-06-30 |
Shared: 1M-token context, 128K max output (300K on Batches API with beta header), token-based API pricing (Batch 50% off), adaptive thinking (default effort high), text and image input, text output. Non-default temperature/top_p/top_k return a 400 error. Latency rated “fast” (second only to Haiku 4.5).
Sonnet 5.5 vs Sonnet 5 (breaking changes)
New between_tools setting turns off up-front thinking (at high effort or below); forced tool use returns an error; thinking blocks are tied to the model and conversation; computer_20251124 tool rejected on Claude API and Google Cloud; the advisor tool rejects Opus 4.8, Opus 4.7 and Sonnet 5 as advisors.
Availability
Claude API, Amazon Bedrock (anthropic.claude-sonnet-5-5), Google Cloud, Microsoft Foundry, Claude Platform on AWS.
Lineage
Predecessors: Sonnet 4.6, Sonnet 4.5. Prices dropped from Sonnet 5 onward.
Sources
- https://platform.claude.com/docs/en/models/sonnet-5-5/overview (accessed 2026-09-30)
- https://platform.claude.com/docs/en/models/sonnet-5/overview (accessed 2026-09-30)
- https://platform.claude.com/docs/en/about-claude/models/overview (accessed 2026-09-30)
- https://platform.claude.com/docs/en/about-claude/model-deprecations (accessed 2026-09-30)