Model · Anthropic · Text
Claude Sonnet 5
Anthropic's mid-tier workhorse of mid-2026 — a balance of speed and intelligence, and a drop-in replacement for Claude Sonnet 4.6 at a lower price. Superseded by Claude Sonnet 5.5 (2026-09-28) but still available.
- Modality
- Text
- License
- Proprietary (Proprietary)
- Context window
- 1,000,000 tokens 1M tokens is both the default and the maximum — there is no smaller context variant. Up to 128k output, or 300k on the Batch API with the output-300k beta header. Uses the newer tokenizer: the same input text produces roughly 30% more tokens than on Sonnet 4.6, so cost does not fall in direct proportion to the lower per-token price.
- Released
- June 30, 2026
- Last verified
- October 28, 2026
- Runs locally
- No
- Also handles
- vision
Strengths
- Best combination of speed and intelligence in the Claude lineup
- A capability upgrade over Sonnet 4.6 at a lower price ($2/$10 per MTok), with the largest gains in coding and agentic tasks
- Adds the browser use tool and the 2026-08-01 computer-use toolset, neither of which Sonnet 4.6 supports
- Fills the gap between Sonnet 4.6 and Opus-class models without Opus pricing
Weaknesses
- Setting `temperature`, `top_p`, or `top_k` to a non-default value returns a 400 error
- Manual extended thinking and assistant-message prefill both return 400 errors
- New tokenizer inflates token counts ~30% versus Sonnet 4.6
- May refuse requests involving prohibited or high-risk cybersecurity topics
- Closed weights — cannot be self-hosted
Try it
| Where | Type | Notes |
|---|---|---|
| Anthropic API | hosted-api | API key required |
| AWS Bedrock | hosted-api | Enterprise / regional |
| Google Vertex AI | hosted-api | GCP integration |
| Claude.ai | product | Free tier |
Version history
- Claude Haiku 5.5 Oct 2026
- Claude Sonnet 5.5 Sep 2026
- Claude Opus 5.5 Sep 2026
- Claude Fable 5.1 Sep 2026
- Claude Mythos 5.1 Sep 2026
Official sources
- Model docs docs
- What's new in Sonnet 5 docs
- Models overview docs
Change log
- — Deprecated — superseded by Claude Sonnet 5.5 (released 2026-09-28). Sonnet 5 moves to Anthropic's legacy list; still available, retirement not sooner than 2027-06-30.
- — Initial entry. Released 2026-06-30 as a drop-in replacement for Claude Sonnet 4.6. The $2/$10 per MTok launch pricing became the standard price — the increase to $3/$15 scheduled for 2026-09-01 was cancelled.
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