Anthropic introduced Claude Sonnet 5.5 on September 28, the second model in its Claude 5.5 family, positioning it as a faster, lower-cost complement to Claude Opus 5.5. The company says it runs more than 30% faster than Sonnet 5 and costs up to 30% less for most work.

Same price, fewer tokens

List pricing is unchanged from Sonnet 5: $2 per million input tokens, $10 per million output tokens and $0.20 per million tokens for cache reads. The "up to 30% cheaper" claim therefore does not come from a price cut. According to Anthropic's own testing as reported by AI Weekly, the model uses fewer tokens and batches tool calls more efficiently, so the same task consumes less. Like all vendor-run measurements, the figure comes from Anthropic and has not been independently reproduced in the sources we reviewed.

Benchmarks and positioning

Anthropic reports 70.6% on Terminal-Bench 4.0, an agentic coding evaluation, versus 10.3% for Sonnet 5 and 66.4% for Opus 5.5. AI Weekly also cites 80.1% on OSWorld 2.1 and a GDPval-AA v2.1 score of 1,844, close to Opus 5.5's 1,846. Anthropic describes the model as strongest at well-scoped everyday tasks, bug fixes and producing documents, slides and spreadsheets, and says it is the first Sonnet model able to beat Pokémon Red working only from screenshots. Benchmark results are self-reported and should be read with that caveat.

Cyber safeguards and availability

Because Sonnet 5.5's cybersecurity capabilities are comparable to Opus 5's, Anthropic says it is the first Sonnet model to launch with the cyber safeguards and fallbacks developed for its most capable models. The company has also pointed to a forthcoming Haiku 5.5, per AI Weekly.

Sonnet 5.5 is available through the Claude Platform and on Amazon Web Services, Google Cloud and Microsoft Foundry, under the model ID claude-sonnet-5-5.

For teams running agents at volume, the practical question is whether the efficiency gain holds on real workloads: when a model is cheaper per task but not per token, the saving depends on how much tool-call batching your own workflows allow.