g3fizdZddlmZddlmZddlmZmZmZm Z ddl m Z erddl m Z mZddlmZGdd eZy ) z%Model fallback middleware for agents.) annotations) TYPE_CHECKING)AgentMiddlewareModelCallResult ModelRequest ModelResponse)init_chat_model) AwaitableCallable) BaseChatModelcXeZdZdZ dfd Z ddZ ddZxZS)ModelFallbackMiddlewareaRAutomatic fallback to alternative models on errors. Retries failed model calls with alternative models in sequence until success or all models exhausted. Primary model specified in `create_agent`. Example: ```python from langchain.agents.middleware.model_fallback import ModelFallbackMiddleware from langchain.agents import create_agent fallback = ModelFallbackMiddleware( "openai:gpt-4o-mini", # Try first on error "anthropic:claude-sonnet-4-5-20250929", # Then this ) agent = create_agent( model="openai:gpt-4o", # Primary model middleware=[fallback], ) # If primary fails: tries gpt-4o-mini, then claude-sonnet-4-5-20250929 result = await agent.invoke({"messages": [HumanMessage("Hello")]}) ``` ct||g|}g|_|D]R}t|tr%|jj t |8|jj |Ty)zInitialize model fallback middleware. Args: first_model: First fallback model (string name or instance). *additional_models: Additional fallbacks in order. N)super__init__models isinstancestrappendr )self first_modeladditional_models all_modelsmodel __class__s h/var/www/auto_recruiter/arenv/lib/python3.12/site-packages/langchain/agents/middleware/model_fallback.pyrz ModelFallbackMiddleware.__init__/si "6$56 +-  *E%% ""?5#9: ""5)  *c ||S#t$r }|}Yd}~nd}~wwxYw|jD]4} ||j|cS#t$r }|}Yd}~.d}~wwxYw|)a<Try fallback models in sequence on errors. Args: request: Initial model request. handler: Callback to execute the model. Returns: AIMessage from successful model call. Raises: Exception: If all models fail, re-raises last exception. Nr Exceptionroverriderrequesthandlerelast_exceptionfallback_models rwrap_model_callz'ModelFallbackMiddleware.wrap_model_callEsz& 7# # N #kk N w//n/EFF !"  s' A  A!AA!cK ||d{S7#t$r }|}Yd}~nd}~wwxYw|jD]=} ||j|d{7cS#t$r }|}Yd}~7d}~wwxYw|w)aRTry fallback models in sequence on errors (async version). Args: request: Initial model request. handler: Async callback to execute the model. Returns: AIMessage from successful model call. Raises: Exception: If all models fail, re-raises last exception. Nrr r#s rawrap_model_callz(ModelFallbackMiddleware.awrap_model_callgs&  )) )) N #kk N $W%5%5N%5%KLLLL !"  seA< A< +&A<+A<A!AA!A<! A6*A1,A<1A66A<)rstr | BaseChatModelrr,returnNone)r$rr%z'Callable[[ModelRequest], ModelResponse]r-r)r$rr%z2Callable[[ModelRequest], Awaitable[ModelResponse]]r-r)__name__ __module__ __qualname____doc__rr)r+ __classcell__)rs@rrrsm2*(*0*  *,  9   D  D   rrN)r2 __future__rtypingr!langchain.agents.middleware.typesrrrrlangchain.chat_modelsr collections.abcr r *langchain_core.language_models.chat_modelsr rrrr;s4+"  23Hrorr