On September 28, 2026, Anthropic announced Claude Sonnet 5.5 on its official website — the second model in the Claude 5.5 family. Pricing is identical to Sonnet 5: $2 per million input tokens, $10 per million output tokens, and $0.20 for cache reads. Output is over 30% faster, and most workloads can cost up to 30% less. Faster and cheaper at the same price: a rare "more for the same money" move for the Sonnet line.
The benchmarks are the most persuasive part of this launch. On Terminal-Bench 4.0, Sonnet 5.5 scores 70.6%, compared with just 10.3% for Sonnet 5; on GDPval-AA it reaches 1844 points versus 1449 for Sonnet 5. It is also the first Sonnet model to beat Pokémon Red using only in-game screenshots — a test of long-horizon planning and trial-and-error that matters for agentic workloads. On safety, it is the first Sonnet to ship with cybersecurity guardrails on by default: high-risk cybersecurity requests automatically fall back to Sonnet 5, while biology-related guardrails match Sonnet 5.
The Sonnet line reaches for Opus territory for the first time
Anthropic positions Sonnet 5.5 plainly: a faster, cheaper complement to Opus 5.5 ($4 input / $20 output per million tokens), aimed at everyday work — fixing bugs, writing docs, building slides and spreadsheets. There used to be a clear capability wall between Sonnet and Opus; that wall just got thinner. When a Sonnet-priced model approaches higher-tier quality on some benchmarks, developers need to redo the math on their default choice.
Early testers are already signaling
Daniel Vogel, COO of Epic Games, says Sonnet 5.5 reached higher-tier model quality in system design audits; Curtis Allen, an engineer at Slack, notes that in internal Slackbot evaluations it completes tasks in fewer steps and uses about 14% fewer output tokens — for pay-per-use API calls, that translates directly into thinner bills.
What it means for model selection
For developers, Sonnet 5.5 is likely to become the new default workhorse: agentic coding and bulk document processing — the token-hungry workloads — where you want speed without paying Opus-level prices, sit squarely in its range. It is available on every platform, including AWS, Google Cloud, and Azure, under the API name claude-sonnet-5-5, with a zero data retention option. Anthropic also says Haiku 5.5 will join the 5.5 family in the coming weeks, giving lighter workloads an even cheaper option. Hitting speed, cost, and safety in a single release, Sonnet 5.5 looks less like a routine upgrade and more like a repricing of the whole product line.
