tj8rUdZddlmZddlZddlmZmZddlmZddl m Z m Z m Z m Z mZmZddlmZerddlmZmZdd lmZdd lmZmZmZejeZd3dZd4dZd5dZ d6dZ!d7dZ"d8dZ#d9d"Z$d:d%Z%d;d'Z&du8Model fallback middleware for agents. When a caching middleware such as `AnthropicPromptCachingMiddleware` wraps this middleware from the outside, it applies Anthropic `cache_control` markers to the request *before* the fallback loop runs. Those markers are provider-specific and cause API errors on non-Anthropic fallback models, so this middleware strips them from fallback attempts — but only when the fallback model itself cannot accept Anthropic cache markers. When the fallback is another Anthropic model the markers are valid and preserve prompt caching, so they are left intact. The knowledge of the `cache_control` marker is duplicated here (rather than owned solely by the Anthropic partner package) because an outer caching middleware never re-runs during fallback and therefore cannot clean up after itself. ) annotationsN) TYPE_CHECKINGAny)BaseTool)AgentMiddleware AgentStateContextT ModelRequest ModelResponse ResponseT)init_chat_model) AwaitableCallable) BaseChatModel) AIMessage AnyMessage SystemMessagecontent str | list[str | dict[str, Any]]returnct|ts|Sg}d}|D]X}t|ts||-t |\}}|p|}||Y|r|n|S)z;Remove Anthropic cache markers from message content blocks.F) isinstancelistdictappend)_without_cache_control_from_content_block)rsanitized_contentchangedblocksanitized_block block_changeds h/var/www/html/CA-Chatbot/venv/lib/python3.11/site-packages/langchain/agents/middleware/model_fallback.py_sanitize_content_blocksr#*s gt $ $46G22%&&   $ $U + + + )RSX)Y)Y&*]  1111 ' 4  W4system_messageSystemMessage | Nonecx|dSt|j}||jur|S|d|iS)z5Remove Anthropic cache markers from a system message.Nrupdater#r model_copy)r%rs r"_sanitize_system_messager,@sQt01GHHN222  $ $Y8I,J $ K KKr$messageslist[AnyMessage]cvg}d}|D]-}t|\}}|p|}||.|r|n|S)z5Remove Anthropic cache markers from request messages.F)_sanitize_messager)r-sanitized_messagesrmessagesanitized_messagemessage_changeds r"_sanitize_messagesr5Nsb+-G55->w-G-G*?,_!!"34444!( 6  h6r$toolslist[BaseTool | dict[str, Any]]cg}d}|D]U}t|trt|\}}nt|\}}|p|}||V|r|n|S)z2Remove Anthropic cache markers from tool payloads.F)rr_sanitize_base_tool_sanitize_dict_toolr)r6sanitized_toolsrtoolsanitized_tool tool_changeds r"_sanitize_toolsr?[s8:OG// dH % % E+>t+D+D (NLL+>t+D+D (NL)\~....% 0??50r$requestModelRequest[ContextT]ci}t|j\}}|r||d<t|j}||jur||d<t |j}||jur||d<t |j}||jur||d<|s|St dt||j di|S)zLSanitize provider-specific Anthropic cache markers before fallback attempts.model_settingsr%r-r6zHStripped Anthropic cache_control markers from %s before fallback attempt) _without_cache_controlrCr,r%r5r-r?r6loggerdebugsortedoverride)r@ overridesrCmodel_settings_changedr%r-r6s r"_sanitize_request_for_fallbackrLos "I-CGDZ-[-[*N*5&4 "#-g.DEENW333&4 "#!'"233Hw''' ( * GM * *E GM!!" '  LLRy 7  ( (i ( ((r$r2rtuple[AnyMessage, bool]cxt|j}||jur|dfS|d|idfS)zRemove Anthropic cache markers from a single message. Returns: The sanitized message (the original instance when unchanged) and whether any marker was removed. Frr(Tr*)r2rs r"r0r0sM1AAGO++~   i1B%C  D Dd JJr$r<rtuple[BaseTool, bool]c|js|dfSt|j\}}|s|dfS|d|pdidfS)zRemove Anthropic cache markers from a `BaseTool` payload. Returns: The sanitized tool (the original instance when unchanged) and whether any marker was removed. Emptied `extras` collapse back to `None`. FextrasNr(T)rQrEr+)r<sanitized_extrasrs r"r9r9sc ;U{ 6t{ C Cg U{ ??8-=-E"F? G G MMr$dict[str, Any]tuple[dict[str, Any], bool]ct|\}}|d}t|ts||fSt|\}}|s||fSi|d|pdidfS)zRemove Anthropic cache markers from a dict-style tool payload. Returns: The sanitized tool (the original instance when unchanged) and whether any marker was removed. Emptied `extras` collapse back to `None`. rQNTrEgetrr)r<r=rrQrRextras_changeds r"r:r:s5T::NG    ) )F fd # #'w&&'=f'E'E$n 'w&& An Ah(8(@D A A4 GGr$payloadcRd|vr|dfSd|DdfS)zFReturn payload without `cache_control`, plus whether anything changed. cache_controlFc&i|]\}}|dk ||S)r[rD).0keyvalues r" z*_without_cache_control..s(PPP U9O9Oe9O9O9Or$T)items)rYs r"rErEs@g%%~ QPgmmooPPP  r$rct|\}}dD]\}||}t|ts-t|\}}|sB||urt|}|||<d}]||fS)a'Return content block without Anthropic cache markers. Strips `cache_control` from the block itself and from its nested `extras` and `metadata` payloads. Returns: The sanitized block (the original instance when unchanged) and whether any marker was removed. )rQmetadataTrV)rr r nested_keynested_payloadsanitized_payloadnested_changeds r"rrs 6e<<OW,   (,,Z88.$//  ,B>,R,R)>   e # #"5kkO&7 # G ##r$>anthropic-chatanthropic-bedrock-chatanthropic-chat-vertexaizfrozenset[str]_ANTHROPIC_LLM_TYPESmodelrboolc`t|dd}t|to|tvS)arReturn whether `model` accepts Anthropic `cache_control` markers. Checked via `_llm_type` so the decision is provider-based rather than model-name-based: any Anthropic-compatible model (including future model IDs we have not seen) keeps its cache markers on fallback, while OpenAI, Gemini, and other non-Anthropic providers get a sanitized request. _llm_typeN)getattrrstrrk)rlllm_types r"!_supports_anthropic_cache_controlrs s0uk400H h $ $ I5I)IIr$c4eZdZdZdfd Zdd ZddZxZS)ModelFallbackMiddlewarea<Automatic 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 import ModelFallbackMiddleware from langchain.agents import create_agent fallback = ModelFallbackMiddleware( "openai:gpt-5.5", # Try first on error "anthropic:claude-sonnet-4-5-20250929", # Then this ) agent = create_agent( model="openai:gpt-5.5", # Primary model middleware=[fallback], ) # If primary fails: tries gpt-5.5, then claude-sonnet-4-5-20250929 result = await agent.invoke({"messages": [HumanMessage("Hello")]}) ``` first_modelstr | BaseChatModeladditional_modelsrNonect|g|R}g|_|D]Y}t|tr(|jt |?|j|ZdS)zInitialize model fallback middleware. Args: first_model: First fallback model (string name or instance). *additional_models: Additional fallbacks in order. N)super__init__modelsrrqrr )selfrvrx all_modelsrl __class__s r"r|z ModelFallbackMiddleware.__init__0s "6$566 +-  * *E%%% * ""?5#9#9:::: ""5))))  * *r$r@rAhandler%>^%>%T%TUUUUUUUUUUU   !" s( +&+$A?? B BB)rvrwrxrwrry)r@rArrrr)r@rArrrr)__name__ __module__ __qualname____doc__r|rr __classcell__)rs@r"rurusp2******,((((T((((((((r$ru)rrrr)r%r&rr&)r-r.rr.)r6r7rr7)r@rArrA)r2rrrM)r<rrrO)r<rSrrT)rYrSrrT)rrSrrT)rlrrrm)-r __future__rloggingtypingrrlangchain_core.toolsr!langchain.agents.middleware.typesrrr r r r langchain.chat_modelsr collections.abcrr*langchain_core.language_models.chat_modelsrlangchain_core.messagesrrr getLoggerrrFr#r,r5r?rLr0r9r:rEr frozensetrk__annotations__rsrurDr$r"rs   #"""""%%%%%%%%))))))211111M33333333HHHHHHLLLLLLLLLL  8 $ $5555, L L L L 7 7 7 71111())))B K K K KNNNN&HHHH,$$$$^(1y(( J J J JBBBBBoj.CXy.XYBBBBBr$