Model · Anthropic · Text
Claude Sonnet 5.5
Anthropic's mid-tier workhorse — the best combination of speed and intelligence in the current lineup, at the same $2/$10 price as Claude Sonnet 5, which it succeeds.
- 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.
- Released
- September 28, 2026
- Last verified
- October 28, 2026
- Runs locally
- No
- Also handles
- vision
Strengths
- Best combination of speed and intelligence in the Claude lineup
- Same $2/$10 per MTok as Sonnet 5, with cache reads at 5% of the input price
- Adaptive thinking defaults to `high` effort; the `between_tools` setting turns off up-front thinking for lower latency
Weaknesses
- Setting `temperature`, `top_p`, or `top_k` returns a 400 error
- Forced tool use (`tool_choice` of `any` or `tool`) returns a 400 error
- Text between tool calls arrives in thinking blocks, so streamed progress updates go quiet until a display setting is chosen
- The older `computer_20251124` computer-use tool is rejected on the Claude API and Google-managed Google Cloud
- 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 | Claude apps |
Used in solutions
Version history
- Claude Haiku 5.5 Oct 2026
- Claude Sonnet 5.5 Sep 2026 Current
- 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 5.5 docs
- Models overview docs
Change log
- — Initial entry. Released 2026-09-28, superseding Claude Sonnet 5; $2/$10 per MTok, 1M-token context, 128k output (300k on Batch with the beta header).
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