fix(langchain): use override in model fallbacks #33716
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Reset model_settings when switching to fallback model to prevent provider-specific parameters from causing errors. Fixes langchain-ai#33709
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Oct 29, 2025
| # Try fallback models | ||
| for fallback_model in self.models: | ||
| request.model = fallback_model | ||
| request.model_settings = {} |
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Could you do this using override? request = request.override(model=fallback_model)
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Taking over the implementation |
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Thank you so much for the helpful review and for taking over the implementation! |
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@bart0401 I pushed this to avoid the mutation in place on the model parameter, not the model_settings. We'd need a different solution for model settings, since we can't assume it's safe to clear them |
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But what if your fallback model is also an Anthropic model? You shouldn't be removing the context-control from it. |
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Description:
Clears
model_settingswhenModelFallbackMiddlewareswitches to a fallback model. Previously, provider-specific settings like Anthropic'scache_controlwould persist and cause errors when passed to other providers (e.g., OpenAI throwingTypeError: unexpected keyword argument 'cache_control').Issue: Fixes #33709
Dependencies: None
Testing:
model_settingsare cleared on fallback