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fix: fallback model never triggers on a malformed provider response #117

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fix: fallback model never triggers on a malformed provider response #117

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0736efb
fix: fallback model never triggers on a malformed provider response
fabceolin Sep 25, 2026
ebfd48a
fix: use ModelHTTPError instead of ModelAPIError (not in pinned pydan…
fabceolin Sep 25, 2026
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8 changes: 6 additions & 2 deletions codewiki/src/be/llm_services.py
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Original file line number Diff line number Diff line change
Expand Up @@ -13,7 +13,7 @@

from openai.types import chat

from pydantic_ai.exceptions import ModelHTTPError
from pydantic_ai.exceptions import ModelHTTPError, UnexpectedModelBehavior
from pydantic_ai.models.openai import OpenAIChatModel, OpenAIChatModelSettings
from pydantic_ai.models.fallback import FallbackModel
from pydantic_ai.providers.openai import OpenAIProvider
Expand Down Expand Up @@ -254,7 +254,11 @@ def create_fallback_models(config: Config) -> FallbackModel:
"""Create fallback models chain from configuration."""
main = create_main_model(config)
fallback = create_fallback_model(config)
return FallbackModel(main, fallback)
# Default fallback_on=(ModelHTTPError,) does NOT cover UnexpectedModelBehavior, which
# is what pydantic-ai raises for a 200 response with a malformed/empty body (seen once
# against OpenRouter: choices/model/object all None). Without this, that failure mode
# skips the fallback model entirely and kills the module outright.
return FallbackModel(main, fallback, fallback_on=(ModelHTTPError, UnexpectedModelBehavior))


def create_openai_client(config: Config) -> OpenAI:
Expand Down
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