Google updated its autonomous coding workspace Antigravity on October 3, adding Anthropic's Claude Opus 5.5 and Claude Sonnet 5.5 directly into its model selector. Antigravity functions as an agentic developer platform that plans, writes, and tests code across complex software repositories.

The catch: both models are reserved for paying Google AI Pro and Google AI Ultra subscribers. Users on free or basic plans don't get access. The update also retires Claude Opus 4.6, Claude Sonnet 4.6, and the open-weights GPT-OSS-120B from the platform on November 2.

Sonnet 5.5 is positioned for faster code execution at lower token cost, while Opus 5.5 handles deep logic and agentic workflows. The move gives Google-subscribed engineers direct access to newer frontier models without needing a separate Anthropic API key.