GitHub added Anthropic's Claude Sonnet 5.5 to Copilot the same day the model launched, September 28. It is generally available to Pro, Pro+, Max, Business, and Enterprise users across VS Code, Visual Studio, the Copilot CLI, JetBrains, Xcode, and github.com, billed at provider list pricing under usage-based billing.

For developers, that puts the headline efficiency story directly into their editor: Anthropic says Sonnet 5.5 generates output more than 30% faster than Sonnet 5 and can cut cost per task by up to 30%, while per-token prices hold at $2 per million input and $10 per million output tokens. It scored 70.6% on Terminal-Bench 4.0, ahead of Opus 5.5's 66.4% at its highest effort setting.

It is also the first Sonnet release to ship with the cyber safeguards and fallback protections Anthropic previously reserved for its most capable models, plus new safety classifiers the company says block reasoning-extraction attempts used in distillation attacks.