Claude Sonnet 5.5

Overview

Claude Sonnet 5.5 is Anthropic's mid-tier frontier model in the 5.x generation, positioned between the efficient Haiku and the top-of-range Opus lines. It delivers strong reasoning, coding, and agentic task performance at a cost point designed for high-volume enterprise deployment. Sonnet 5.5 builds on extended thinking capabilities introduced in earlier Claude generations, making it viable for complex multi-step workflows without the compute overhead of Opus-class models.

Why it matters

For enterprise buyers, Sonnet 5.5 sits at the inflection point where capability meets deployment economics — capable enough for production agentic workflows, efficient enough to run at scale without Opus-level spend. As Anthropic's IPO prospectus reveals a company burning $8B annually while growing revenue 12x, the Sonnet tier is the product line that has to carry the commercial weight: it's what most API customers actually pay for. Agentic deployments increasingly require models that can sustain multi-step reasoning across tool calls and long contexts, and Sonnet 5.5 targets exactly that use case. For investors and procurement teams evaluating Anthropic as a vendor, understanding how Sonnet 5.5 prices and performs relative to GPT-6-class models from OpenAI and Gemini 2.5 Pro from Google is now a core part of AI vendor due diligence.