How to Use Gemini 4 Argon in Antigravity on Google AI Pro (No $99.99 Ultra Plan Needed)

Google's current Antigravity model documentation lists Gemini 4 Argon for paid Google AI Pro subscribers, excluding trial subscriptions. Eligible Pro users can therefore access Argon without upgrading to Ultra.

The short version

• Who qualifies: Paid Google AI Pro subscribers, not free-trial users. Ultra and Enterprise are also listed as eligible.

• Where to use it: The Antigravity desktop app, CLI, or supported IDE extensions—not the standalone Antigravity IDE.

• Quota: Google does not publicly specify Argon's exact allowance. Check Settings or run /usage (alias /quota) in the CLI.

• Developer credits: These do not increase Antigravity quota. They may apply to eligible direct Gemini API usage, which is billed separately.

Set up Argon

1. Check your subscription. On your Google One page, confirm that you have paid Google AI Pro rather than a trial. Access to Argon in the Gemini app does not automatically mean it is enabled in Antigravity.

2. Update Antigravity. Install the latest desktop app or CLI. Access can roll out gradually, so the model may not appear immediately.

3. Use a supported surface. Open the desktop app, CLI, or an Antigravity extension for a supported editor such as VS Code, Visual Studio, JetBrains IDEs, Zed, or Xcode. The model documentation lists the standalone Antigravity IDE as unsupported.

4. Choose the model. In the app, use the model selector below the prompt box. In the CLI, run /model and select Gemini 4 Argon.

5. Choose effort and check usage. Use Low, Medium, or High thinking where available; High may be useful for difficult debugging or architecture work. Check Settings or run /usage (/quota) after a real task to see your account's quota status.

If Argon does not appear, confirm your paid subscription, update the app, and check again after the rollout has had time to reach your account. Antigravity is intended for personal Google Accounts in supported regions; Google suggests trying an @gmail.com account if Workspace sign-in causes trouble. Contact Google One support if the problem persists.

How the quota works

Google's plans documentation says the general Pro quota refreshes every five hours until the weekly limit is reached. However, it does not publish Argon's exact allowance or confirm whether Argon has a separate weekly-only quota. Treat the model-specific limit as unknown and use the in-product usage panel as your guide.

Quota depends on the work the agent performs, not just the number of prompts. Small edits usually require less work than long, multi-file refactors. To make the allowance last, reserve Argon for difficult debugging, architecture decisions, and complex agent runs; use Gemini 3.8 Flash for routine edits and quick questions.

Antigravity also has an AI Credit Overages setting. Never waits for the quota to refresh rather than automatically spending AI credits; Always permits purchased AI credits to cover overages at the applicable consumption pricing. These are Google One AI credits—not Google Developer Program credits. If you do not want unexpected charges, check the plans documentation and leave overages on Never until you understand the costs.

What Developer credits can—and can't—do

Google AI Pro includes a $10 monthly GenAI and Cloud credit through the Google Developer Program. These are Google Cloud credits, not Antigravity quota, and they cannot unlock Argon or top up your Antigravity plan limit.

You can use the Gemini API as a separate billing route, but API usage is not included in the Google AI Pro subscription. Google's Gemini API pricing page lists Argon under the model ID gemini-4-argon. I have not independently tested selecting Argon through the CLI's API-key mode, so do not assume that route works for your setup without testing it.

For the Standard paid API tier, Google's listed introductory rates through November 30, 2026, are:

• Input: $2 per million tokens

• Output, including thinking tokens: $10 per million tokens

• Cached input: $0.10 per million tokens when implicit caching applies

From December 1, 2026, the listed Standard rates rise to $4 per million input tokens and $20 per million output tokens, with cached input at $0.20. Check that pricing page for your tier and current rates.

Eligible Google Cloud credits may cover Gemini API usage, but eligibility depends on your billing setup. With the Prepay plan, Google says you must first buy prepaid API credits; the current minimum purchase is $5. Eligible Cloud credits are applied before the prepaid balance, but not every Cloud credit is eligible. Confirm eligibility in Google's Gemini API billing guide, and make a small test call before relying on the credits.

Important: Google's Antigravity FAQ says using your Antigravity login through third-party coding tools such as Claude Code, OpenClaw, or OpenCode violates its Terms of Service. For third-party coding agents, Google recommends a Gemini Enterprise or Google AI Studio API key, which is billed separately. The FAQ describes CLI headless mode (agy -p) as intended for direct scripting and CI—not as a way to wrap Antigravity inside third-party agents or rotate accounts.

Bottom line

Paid, non-trial Google AI Pro subscribers are listed as eligible for Argon in Antigravity. Use a supported app, CLI, or editor extension and check the usage panel; Google's public docs do not specify Argon's exact quota. Developer credits cannot increase that quota, though eligible credits may cover some separately billed Gemini API usage. Consider Ultra only if you regularly hit your Pro limits and the extra capacity is worth the cost for your work.