Anthropic released Claude Sonnet 5.5 on September 28 at the same price as Sonnet 5. That is $2 per million input tokens and $10 per million output tokens, half the price of Opus 5.5. Anthropic says it scores close to Opus 5.5 on several tests. Artificial Analysis, an independent tester, ranks it two points behind Opus 5.5 but measured heavy token use at the highest effort setting.
New to this? Read it in simple words
- Anthropic released a new AI model called Claude Sonnet 5.5.
- It costs half as much per token as Anthropic’s top model and scores almost as well in its tests.
- An independent tester agrees that it is nearly as good.
- But at the highest setting it used many tokens per task, which made it expensive.
- Token
- A small piece of text, often part of a word, that AI companies count and charge for.
- Effort setting
- How long a model may think; more effort usually means better answers and a higher cost.
- Benchmark
- A standard test used to compare AI models.
What Anthropic claims
Sonnet 5.5 costs $2 per million input tokens and $10 per million output tokens, the same as Sonnet 5 and half the price of Opus 5.5.
Anthropic says it generates output more than 30% faster than Sonnet 5 and costs up to 30% less per task, because it needs far fewer tokens.
On Anthropic’s own tests, it scores 70.6% on Terminal-Bench 4.0, an agentic coding test, against 66.4% for Opus 5.5 and 10.3% for Sonnet 5. On GDPval-AA, a test of office work across 44 professions, it scores 1,844 against 1,846 for Opus 5.5.
Anthropic’s claims next to Artificial Analysis’s independent results.
What the independent test found
Artificial Analysis gave Sonnet 5.5 a score of 56 on its Intelligence Index at maximum effort, two points behind Opus 5.5.
At that setting it used about 193,000 output tokens per task, the most the firm has measured. It cost $7.60 per task, about 50% more than Sonnet 5.
Anthropic’s savings claims mostly refer to lower effort settings, where costs are much smaller: $0.59 per task at medium effort, by Artificial Analysis’s count. The firm says it tested a pre-release version with a since-fixed bug and will re-run some tests.
Sources2
Safeguards and what comes next
Because its cyber skills are comparable to Opus 5’s, Anthropic says, Sonnet 5.5 is the first Sonnet to launch with cyber safeguards. Higher-risk cybersecurity requests fall back to Sonnet 5.
Artificial Analysis saw that fallback in about 0.1% of its tasks.
Sonnet 5.5 is available on Anthropic’s platform, AWS, Google Cloud and Microsoft Azure. Anthropic says a cheaper Haiku 5.5 will follow in the coming weeks.
Sources
Every fact in this story comes from the sources below. Open them to check our work.
- 1
- 2Research · September 28, 2026Claude Sonnet 5.5 reaches #2 on the Artificial Analysis Intelligence Index Artificial Analysis
- 3Research · September 28, 2026Anthropic’s Claude Sonnet 5.5 nearly matches Opus 5.5 on benchmarks while costing up to 30 percent less per task The Decoder
- 4Research · September 28, 2026Anthropic launches Claude Sonnet 5.5 with 30% cost reduction per-task due to faster speeds and fewer tool calls VentureBeat
We read Anthropic’s announcement and Artificial Analysis’s independent results, and compared The Decoder and VentureBeat. The speed and cost-per-task claims are Anthropic’s. Some of the scores Anthropic cites were run for it by Artificial Analysis on a pre-release version.