Google Antigravity adds Anthropic's Claude Opus 5.5 and Sonnet 5.5

Google added Anthropic's Claude Opus 5.5 and Claude Sonnet 5.5 to the model picker in its Antigravity agentic IDE, according to Google's own Antigravity model documentation, with access restricted to paying Google AI Pro and Ultra subscribers. Pro costs $19.99 a month, Ultra 5x $99.99, and Ultra 20x $199.99, while trial Pro subscriptions, Free, AI Plus, and Enterprise tiers are excluded. The addition closes a gap that had left Antigravity running Claude Opus 4.6 and Sonnet 4.6 after Anthropic shipped Opus 5.5 on September 22 and Sonnet 5.5 on September 28, and Google's changelog still does not call out either model.

Only Pro and Ultra subscribers can access it, but Google has added Anthropic's newest flagship coding models to its own developer tool. Google's own Antigravity model documentation now lists Claude Opus 5.5 and Claude Sonnet 5.5 in its model picker. Both thinking variants sit under the conversation input next to Gemini, with access limited by plan. That's Google, a company spending billions building its own frontier models, choosing to bake a rival's best work directly into the core of its own product. You don't get it for free, though. Access is locked to paying Google AI Pro and Ultra subscribers, and even that comes with a catch: Google's model documentation says a trial Pro subscription doesn't unlock the new Claude models. Free, AI Plus, and Enterprise tiers are shut out entirely. If you want Opus 5.5 or Sonnet 5.5 inside Antigravity, you pay full price: $19.99 a month for Pro, $99.99 for Ultra 5x, or $199.99 for Ultra 20x, according to pricing details reported by CloudZero. Here's what makes the timing notable. Antigravity had already been running Claude's older Opus 4.6 and Sonnet 4.6 even after Anthropic shipped Opus 5.5 on September 22 and Sonnet 5.5 on September 28. Google's own agentic IDE, built after its $2.4 billion Windsurf licensing and talent deal, was running a generation behind on the rival model family it chose to feature. That gap just closed, and it closed quietly: Google's model page confirms the addition, while the changelog still does not call out either model. Antigravity runs Gemini 3.1 Pro by default, with a 1 million token context window that Google says can handle large code repositories. Putting Anthropic's 5.5 models in the same dropdown means every developer using Antigravity can run a live, head-to-head comparison every time they open a new session. That's a real bet, and it's not the first time Google has made it. Antigravity launched in November 2025 offering Claude Sonnet 4.5 and OpenAI's GPT-OSS alongside Gemini, all billed through a Google account rather than Anthropic's or OpenAI's. The strategy isn't new. What's new is that Google just extended it to Anthropic's current 5.5 family, not the older 4.6 models Google has scheduled for removal. Anthropic Calls Opus 5.5 Pacing the Frontier While It Tops the Benchmarks https://startupfortune.com/anthropic-calls-opus-55-pacing-the-frontier-while-it-tops-the-benchmarks/ Anthropic released Claude Opus 5.5 just ten days after CEO Dario Amodei called on AI labs to slow down for safety, but the new model beats Fable 5.1 on every benchmark shown and undercuts GPT-6 Astra on cost while running faster and cheaper than its predecessor. The launch raises the question of whether 'pacing the frontier' is a real slowdown or... - fastest Claude model among frontier AI options https://startupfortune.com/anthropic-calls-opus-55-pacing-the-frontier-while-it-tops-the-benchmarks/ - Opus 5.5 cheaper faster stronger benchmark performance https://startupfortune.com/anthropic-calls-opus-55-pacing-the-frontier-while-it-tops-the-benchmarks/ For a founder or engineering lead deciding where a team's AI coding budget goes, that bundling changes the math. Pay Anthropic directly and you're billed by the token through its API or through Cursor's wrapper around it. Pay Google $19.99, $99.99, or $199.99 a month and you get Opus 5.5, Sonnet 5.5, Gemini 3.1 Pro, and GPT-OSS 120B under one invoice, with usage limits set by Google's tier rather than Anthropic's API pricing. Teams already paying for Google Workspace or Google Cloud have an obvious reason to let Antigravity be the place model comparison happens, rather than running three separate subscriptions to three separate companies. It also says something about how little model-agnosticism costs a platform once the agent orchestration is the real product. Windsurf built its name on letting developers swap models without rewriting how they prompt or structure a task, and Google licensed that technology while hiring Windsurf's CEO and other senior R&D staff. A coding platform that locks a team into one model family is building a moat out of inconvenience, not value, and Google's own plan structure suggests it knows that: keeping Claude competitive inside Antigravity gives developers a reason to stay in Google's IDE even when they'd rather write Claude prompts than Gemini ones. The remaining question is how fully Google will explain the change. A feature can be live in documentation and product UI before it gets a blog post or changelog entry, and that is what appears to have happened here. The company still has 4.6-era models scheduled for removal on November 2, according to its model documentation. Until Google posts a fuller account of what changed and why, the clearest signal of Antigravity's direction is the model table itself: Claude 5.5 is in, older Claude models are on the clock, and Google is still willing to make its coding tool a place where rival frontier models compete. Also read: Manus gave its AI agents phone numbers and wallets days after Nvidia caged them https://startupfortune.com/manus-gave-its-ai-agents-phone-numbers-and-wallets-days-after-nvidia-caged-them/ • Aleph Alpha launches Kolibri, a sovereign German AI model for government use https://startupfortune.com/aleph-alpha-launches-kolibri-a-sovereign-german-ai-model-for-government-use/ • PewDiePie Says OpenAI Banned Him Twice Over the AI Model He Just Released https://startupfortune.com/pewdiepie-says-openai-banned-him-twice-over-the-ai-model-he-just-released/ This article is posted in Technology News https://startupfortune.com/category/technology/ , check it out for more related stories. Join the discussion Open in the community → https://startupfortune.com/community/ Almost there. Sign in and your reply posts straight away. Anthropic Says Claude Fable 5 Will Return to Subscriptions Once Capacity Allows https://startupfortune.com/anthropic-says-claude-fable-5-will-return-to-subscriptions-once-capacity-allows/ Anthropic is pulling Claude Fable 5 out of standard subscription plans on July 7, pushing Pro, Max, Team, and select Enterprise users onto metered API-rate credits. The company says the retreat is temporary and driven by compute scarcity, not strategy, echoing similar capacity strain at OpenAI. - Claude Fable 5 subscription pricing changes https://startupfortune.com/anthropic-says-claude-fable-5-will-return-to-subscriptions-once-capacity-allows/ - when will Fable 5 require paid https://startupfortune.com/anthropic-says-claude-fable-5-will-return-to-subscriptions-once-capacity-allows/