Claude Sonnet 5.5
Anthropic's speed-and-intelligence tier: $2 / $10 per million tokens, 1M context, 30%+ faster output than Sonnet 5.
What it is
Claude Sonnet 5.5 is the second model in the Claude 5.5 family. Pricing is unchanged from Sonnet 5 ($2 / $10), but Anthropic says it uses fewer tokens per task, so most work costs up to 30% less. It is the default model for free Claude.ai users according to launch coverage.
Pricing
| Input | $2.00 |
| Output | $10.00 |
| Cached input (cache read) | $0.100 |
| Cache write | $2.50 |
| Batch input | $1.00 |
| Batch output | $5.00 |
| Fast / priority input | not published |
| Fast / priority output | not published |
- Cache read is 5% of input price (0.05x).
- 1-hour cache write is $4 / MTok.
- Same list price as Sonnet 5.
- Full 1M context at standard price.
Capability highlights
- Output generation 30%+ faster than Sonnet 5; up to 30% lower cost per task (vendor claims).
- Terminal-Bench 4.0 70.6% vs 10.3% for Sonnet 5 (vendor-reported).
- Setting temperature, top_p or top_k to a non-default value returns a 400 error.
- First Sonnet model with classifiers that prevent reasoning extraction.
Modalities: text, image → text. Adaptive thinking (can turn off up-front thinking with between_tools); default effort high. 300K output tokens on the Message Batches API with a beta header.
How to use it
API: Claude API model ID claude-sonnet-5-5; Amazon Bedrock anthropic.claude-sonnet-5-5; Google Cloud, Microsoft Foundry and Claude Platform on AWS use claude-sonnet-5-5.
Versus Claude Sonnet 5
Same $2 / $10 list price; cache reads halved to $0.10.
| Claude Sonnet 5 | Sonnet 5.5 | |
|---|---|---|
| Input / 1M | $2.00 | $2.00 |
| Output / 1M | $10.00 | $10.00 |
| Cached input / 1M | $0.200 | $0.100 |
| Context window | 1M | 1M |
| Max output | 128K | 128K |
Published benchmark numbers
Vendor-reported, quoted from the linked announcement. Not independently verified; different vendors run benchmarks under different settings.
| Benchmark | Sonnet 5.5 | Comparison in the same source | Source |
|---|---|---|---|
| Terminal-Bench 4.0 | 70.6% | Sonnet 5: 10.3%, Opus 5.5: 66.4% | Anthropic announcement |
| GDPval-AA v2.1 (Elo) | 1844 | Sonnet 5: 1449, Opus 5.5: 1846 | Anthropic announcement |
| OSWorld 2.1 (partial) | 80.1% | Sonnet 5: 57.0% | Anthropic announcement |
| Humanity's Last Exam (with tools) | 64.5% | Sonnet 5: 54.9% | Anthropic announcement |
Comparisons
Sources
Every number above comes from one of these pages, read on the date shown. Searched for: sonnet 5.5, sonnet 5.5 cost, claude sonnet 5.5.
- Claude Sonnet 5.5 model page (platform.claude.com) read 2026-10-08
release date, model IDs, context, output, pricing, cutoff - Anthropic pricing page read 2026-10-08
cache, batch prices - Anthropic announcement: Claude Sonnet 5.5 read 2026-10-08
benchmarks (vendor-reported), speed and cost claims