Model Fallback

Reviewed by Proof · Updated

Definition

Model fallback means trying a second luv13 model id when the first one is unavailable, instead of failing or waiting.

Key takeaways

  • luv13 runs on single-provider capacity. luv13.ai/docs says that if a model is unavailable, the error names the model, and you should switch to another id.
  • All seven models cost the same $0.33 per 1M tokens, so falling back never changes the price.
  • Fall back only on availability errors, not on 401 (a key problem affects every model) or 400-type request errors.
  • Pick fallbacks that accept the same inputs. If you send images, only fall back to models that take images; see the model list.

Python

import os
import openai
from openai import OpenAI

client = OpenAI(base_url="https://api.luv13.ai/v1", api_key=os.environ["LUV13_API_KEY"])

MODELS = ["luv13/glm-5.3-flash", "luv13/kimi-k3-fast", "luv13/qwen-3.8-27b"]

def ask(messages):
    last_error = None
    for model in MODELS:
        try:
            return client.chat.completions.create(model=model, messages=messages)
        except openai.AuthenticationError:
            raise  # same key for every model; switching won't help
        except (openai.APIStatusError, openai.APIConnectionError) as e:
            last_error = e  # try the next model
    raise last_error

reply = ask([{"role": "user", "content": "ping"}])
print(reply.choices[0].message.content)

Each model is tried with the SDK's own retries first (2 by default), so a brief blip doesn't trigger a switch. See Retrying Requests.

Things to keep in mind

  • Different models give different answers. If output format matters, validate it after a fallback.
  • Log which id you sent, so you know which model answered.
  • For choosing between models on purpose (for example by task), see Model Routing.
  • Check GET /v1/models now and then. If an id in your list disappears, replace it. See Listing Models.