Claude Sonnet 5

Claude Sonnet 5 became available on AI Gateway on June 29, 2026. Anthropic calls Claude Sonnet 5 the most agentic Sonnet model yet: Claude Sonnet 5 makes plans, uses tools like browsers and terminals, and runs autonomously at a level that recently required larger, more expensive models.

The gains over Claude Sonnet 4.6 land across reasoning, tool use, coding, and knowledge work. Anthropic reports strict improvements over Claude Sonnet 4.6 on agentic search and computer use evaluations, along with lower hallucination and sycophancy rates. Anthropic also reports overall performance that approaches its Opus line at a lower price, and Claude Sonnet 5 launched with real-time cyber safeguards enabled by default.

Effort levels define the cost-performance curve. Claude Sonnet 5 supports configurable effort, including an extra-high xhigh level, and higher effort can match Opus-tier output on some tasks while medium effort keeps mixed workloads efficient. Claude Sonnet 5 also uses an updated tokenizer, so the same input can map to more tokens than earlier Sonnet models; verify budgets against real usage rather than prior baselines.

Through AI Gateway, Claude Sonnet 5 is available with the standard unified API, observability, retries, and failover across anthropic, vertexAnthropic, bedrock. Set the model to anthropic/claude-sonnet-5 in the AI SDK, Chat Completions API, Responses API, Messages API, or other API formats, from TypeScript or Python. AI Gateway mirrors provider pricing with no markup and adds no platform fee on inference, including for Bring Your Own Key requests.