Persistent 503 MODEL_CAPACITY_EXHAUSTED on gemini-3-flash-agent (Antigravity Ultra account)

I am getting persistent HTTP 503 errors using gemini-3-flash-agent in Antigravity.

Error:
MODEL_CAPACITY_EXHAUSTED
No capacity available for model gemini-3-flash-agent

Trajectory ID: 119bd8a9-6407-40a3-8778-
TraceID: f52088e76

Important context:

  • Happens only on my Ultra account
  • Works with a free account
  • Not related to project or billing
  • Blocks agent workflows completely

Is this a backend routing or capacity pool issue for this account?