Hi @MangoExecutor, @Roedy_Rustam,
Welcome to the Forum,
Under Antigravity’s Models Policy, Claude Opus 5.5 and Sonnet 5.5 are only available on directly billed (non-trial) Google AI Pro and Ultra subscriptions. If your Google AI Pro plan is currently on an introductory trial, device promo (e.g., Pixel, Chromebook), or partner benefit (e.g., Jio), it is classified as a promotional plan and does not include Claude 5.5 access.
Additionally, legacy third-party models will be retired on November 2, 2026. To retain access to third-party models after that date, you will need to upgrade to a directly billed Google AI Pro or Ultra plan via Google One.
(Note: All Gemini models remain fully available on your current plan)