tool_call_id_errorTier 1 · 70% confidence

ai-agents-tool-call-id-error-keyerror-tool-call-id-occurs-when-using-a-union-ty-149e9772

agent: ai_agents

When does this happen?

IF KeyError: 'tool_call_id' occurs when using a union type for chat_history in InputChat model with pydantic v2, even when only system/human messages are present.

How others solved it

THEN Change the chat_history field type from a strict union of specific message types to a plain List or List[BaseMessage] to avoid pydantic v2 validation errors. For example, use `chat_history: List = Field(...)` instead of `List[Union[HumanMessage, AIMessage, SystemMessage, FunctionMessage, ToolMessage]]`.

Before:
chat_history: List[Union[HumanMessage, AIMessage, SystemMessage, FunctionMessage, ToolMessage]] = Field(...)

After:
chat_history: List = Field(...)

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