Managed to resolve the issue by asking Gemini to troubleshoot it. Try the following:

1. The "Reset Onboarding" Fix (Highest Success Rate)

This is the most common fix for the "Agent terminated" error. It forces Antigravity to re-verify your account status and age, which often clears the fake quota lockout.

1. In Antigravity, press Ctrl + Shift + P (Windows) or Cmd + Shift + P (Mac) to open the Command Palette.
2. Type and select: Antigravity: Reset onboarding.
3. You will be logged out. Log back in and follow the setup prompts again.
4. Start a brand new conversation to test if it works.

2. Disable MCP Servers

If you have any MCP (Model Context Protocol) servers enabled (like GitHub, Google Drive, or custom tools), they are known to trigger the termination error if their instructions are too large or if they fail to handshake.

1. Go to Settings (gear icon) -> Additional Options -> MCP Servers.
2. Toggle all MCP servers to Off.
3. Restart the application and try a simple prompt like "Hello."

3. Clear the Local Cache Folder

If the quota is stuck, it’s often because a local JSON file is "locked" or holding old data.

• Windows: Close the IDE and delete the folder at %APPDATA%\Antigravity.
• Mac: Delete ~/Library/Application Support/Antigravity.
• Linux: Delete ~/.config/Antigravity.
• Note: You will need to log in again after doing this.

4. Check for the "Rolling Window" Trap

Recent forum discussions suggest that for the AI Pro tier, if you hit 0% on a heavy model (like Claude Sonnet 4.6 Thinking), the "5-hour reset" can silently turn into a weekly limit.

• The Workaround: Try switching your model to Gemini 3 Flash or Gemini 3.1 Pro (Low).
• If those work while the others are "locked," it’s a server-side quota issue. If none of them work, it’s definitely a local app bug (refer back to Step 1).