TopicClaude 5.5 models
Google Antigravity Adds Claude Opus 5.5 and Sonnet 5.5 for Paid Subscribers
On October 3, Google's AI coding platform Antigravity updated its model selector: Anthropic's two newest flagships — Claude Opus 5.5 and Claude Sonnet 5.5 — showed up in the official model documentation, letting paid users call a rival's models directly inside Google's own developer tool, no separate Anthropic API key needed. Multiple outlets verified Google's docs on the day; Google issued no formal announcement for the listing. The same documentation also named the retirement list: the Claude 4.6 series and the open model GPT-OSS-120B leave the platform on November 2, 2026.

What Happened
Antigravity is Google's autonomous coding workspace: it plans, writes and tests code across complex software repositories. The new additions are the thinking variants of Claude Sonnet 5.5 and Claude Opus 5.5. According to outlets that checked the documentation, only paid Google AI Pro and Google AI Ultra subscribers get them — Free, Plus and Enterprise accounts are excluded, and trial Pro subscriptions don't qualify.
The same documentation published a retirement schedule: Claude Sonnet 4.6, Claude Opus 4.6 and GPT-OSS-120B leave Antigravity on November 2, 2026. The docs say the reasoning-model choice persists within a conversation, and switching models while an agent is running won't affect the active turn.
Key Facts
- New models: Claude Opus 5.5 / Claude Sonnet 5.5 (thinking), listed in Antigravity's official model documentation on Oct 3.
- Who gets them: Google AI Pro and AI Ultra paid subscribers only; Free, Plus, Enterprise and trial Pro accounts are excluded.
- Retiring: Claude Sonnet 4.6, Claude Opus 4.6 and GPT-OSS-120B leave on November 2, 2026.
- Division of labor: Sonnet 5.5 targets faster, cheaper task execution; Opus 5.5 targets deep reasoning and long-horizon agent workflows (per PC-Tablet).
Context
Google is one of Anthropic's early investors. Putting a rival's newest flagships inside Google's own flagship developer tool, alongside Gemini, is a first. This site reported Anthropic's Sonnet 5.5 launch on Sept 28: output runs 30%+ faster than Sonnet 5 at unchanged API prices, typically needing fewer tokens for the same work.
Why it matters
It is the first time Google has put a rival's newest flagship models inside its own flagship developer tool alongside Gemini; no separate Anthropic API key is needed, but access is limited to Google AI Pro/Ultra paid subscribers.
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