Anthropic ships Claude Sonnet 5.5: 30% faster, 70.6% on Terminal-Bench 4.0, now the free-tier model

Anthropic's Claude Sonnet 5.5 follows Opus 5.5 as the second model in the 5.5 family, and the headline numbers are large:

- more than 30% faster than Sonnet 5;

- API costs cut by up to 30%;

- 70.6% on the Terminal-Bench 4.0 agentic coding benchmark, versus 10.3% for Sonnet 5;

- within two points of Opus 5.5 on real-world workflow benchmarks such as GDPval-AA.

Anthropic positions it as its most capable mid-tier model for everyday coding and knowledge work.

Distribution was broad from day one. AWS made Sonnet 5.5 available on Amazon Bedrock and the Claude Platform on AWS, with guidance on when to pick Sonnet over Opus. It is also in AWS GovCloud (US) for regulated public-sector workloads. Simon Willison flagged what he called the most important detail: Sonnet 5.5 now powers the free tier on claude.ai. Free users therefore get these capabilities. ChatGPT's free tier, by contrast, still runs GPT-5.6 Luna, which Willison called 'a lot less capable.'

Competitively, the launch lands in a strange week. OpenAI pulled GPT-6.1 Astra over safety failures, leaving Anthropic with open space to push a shipping product. The pressure on price is heavy, though. DeepSeek V4.1-Flash's roughly 70% price cut keeps squeezing Western mid-tier pricing. Community observers explicitly named Sonnet 5.5 as the model under that pressure, and r/LocalLLaMA users keep showing Qwen 27B-class models doing impressive work on a single 4090.

The open questions for readers:

- whether the Terminal-Bench leap holds up in independent harnesses, since the 'harness matters' debate is loud this week;

- whether cost-per-task savings survive heavy agentic workloads;

- how Anthropic's IPO prospectus, which Reuters says shows surging costs, squares with giving a frontier-class model away on the free tier.