Gemini 503 model_overloaded

Retry with exponential backoff

Standard retry pattern.

from google.genai import errors
import random, time

for attempt in range(5):
    try:
        return client.models.generate_content(
            model="gemini-3.5-pro", contents=prompt,
        )
    except errors.APIError as e:
        if e.code == 503 and attempt < 4:
            time.sleep(random.uniform(0, min(60, 2 ** attempt)))
            continue
        raise

Fall over to Gemini Flash

Flash has separate capacity from Pro — often available when Pro is overloaded.

Fall over to a different provider

Multi-provider fallback (Gemini → Claude → GPT) preserves uptime.

Try a different Vertex AI region

If one region is overloaded, another may still serve.