Claude Opus 5.5 in Antigravity: Plans and Admin Setup

To use Claude Opus 5.5 and Sonnet 5.5 in Antigravity, your plan and billing settings must be right first. Google announced on its official blog on October 21, 2026 that both models are available in Antigravity. Individual subscribers and company admins need to check different conditions.

Who can use Claude models in Antigravity

Sometimes a new model name shows up in the picker but you cannot click it. It is like a restaurant menu that lists a dish you cannot order with a coupon. You can see the item, but how you pay decides whether you can order it. Antigravity works the same way. Your subscription tier or your company admin's approval opens or locks the Claude models. The conditions below follow Google's official docs. They may change, so check the model docs again before you use them.

The Antigravity model docs list Claude Opus 5.5 and Claude Sonnet 5.5 as supported models. In the picker they appear as "Claude Sonnet 5.5 (Thinking)" and "Claude Opus 5.5 (Thinking)". Availability by plan is as follows.

Plan	Claude 5.5 access
Free	Not available
Google AI Plus	Not available
Google AI Pro	Paid subscriptions only, not trials
Google AI Ultra	Available
Enterprise	Available (admin approval required)

If you are on a Pro trial, you must end the trial and switch to paid Pro to use them.

How to select Claude Opus 5.5 in Antigravity

Developers update to the latest Antigravity 2.0, the Antigravity CLI, or one of the VS Code, JetBrains IntelliJ, or Visual Studio extensions, then pick a model. According to the Google Cloud announcement, you use the model picker or the /model command.

1. Update Antigravity to the latest version.
2. In the model selection menu below the chat input, choose Claude Opus 5.5 or Sonnet 5.5.
3. You can switch models between turns in the same conversation. Workspace state, open artifacts, and terminal context are kept.

If you switch models while the agent is running, the previous model keeps being used until the current turn ends or you cancel the run. So if the first reply right after switching sounds like the old model, that is normal. To confirm the switch worked, check that the picker shows the new model name when the next turn starts.

To split roles, set the model value in a subagent file (.agents/agents/*.md) to one of inherit (the current session model), flash, or pro. For example, use flash for test triage and pro for verifying changes. Google's announcement describes Opus 5.5 as the model for complex work and Sonnet 5.5 as a faster, lower-cost companion.

How company admins enable Claude models, and what it costs

In Gemini Enterprise (Standard and Plus), third-party models such as Claude are off by default. No matter how much developers update, they cannot use the models until an admin turns them on. The steps in the AI developer tools settings doc are below. You need the Gemini Enterprise Admin role, and the project must be linked to a Cloud Billing account that receives invoices.

1. In the Google Cloud console, go to Settings in Gemini Enterprise, then the AI developer tools tab.
2. Turn on overages first.
3. Under Antigravity authorized models, switch on the toggle for the model and accept the third-party terms.
4. Set a monthly spending limit for the project. The limit applies to all models, including third-party ones.

The cost structure matters. Third-party models do not use the pooled monthly Gemini token quota. They are billed pay-as-you-go to your Cloud Billing account. If you later turn overages off, developers cannot use third-party models until you turn them back on. If you turn a model off, access stops soon after. Even when you pick Claude, a lightweight Gemini model keeps running for background tasks such as context management, so those tokens may be billed.

On the API side (Gemini platform), you need to enable the Claude model in Model Garden and accept Anthropic's standard terms. Per-model prices and regional availability are not on the announcement page, so check the rates on the Google Cloud billing screen before you set a budget. For the API price and features of Claude Sonnet 5.5 itself, see Claude Sonnet 5.5 API features and pricing.

Common mistakes

• Assuming a Pro trial will unlock the models. You need a paid subscription.
• An admin turns on the model toggle but not overages. Overages must be on before activation.
• Making Opus 5.5 the default model for the whole team without a spending limit. Third-party models are pay-as-you-go, so set the limit first.

If AI coding tools are new to you, start with What vibe coding means and how to start to get a sense of how to choose a tool.

Frequently asked questions

Can I use only Claude in Antigravity instead of Gemini?

Even if you pick only Claude, a lightweight Gemini model runs alongside it in the background, and that usage may be billed.

Do I need admin settings with an individual Google AI Pro subscription?

Admin settings are for Gemini Enterprise organizations. As an individual, you only need to confirm that you are on paid Pro or higher.

Will I lose my work if I switch models mid-conversation?

No. Workspace state, open artifacts, and terminal context are kept.