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LangChain errors / Schema

ValueError: System message must be at beginning of message list.

platform: LangChain / category: Schema / versions: langchain==0.2.7

Cause

LangGraph appends a system message node after the user message is already in state, but the Anthropic API requires the system message to be first.

Fix

Bind the system prompt directly to the ChatAnthropic model via the system= parameter instead of inserting it as a graph node. Remove any initialize_system_prompt node and its edges. This ensures the system message is always first when sent to the API.

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