> ## Documentation Index
> Fetch the complete documentation index at: https://langchain-5e9cc07a-preview-docscl-1781043860-248c713.mintlify.site/llms.txt
> Use this file to discover all available pages before exploring further.

# INVALID_CHAT_HISTORY

This error is raised in the prebuilt [`createAgent`](https://reference.langchain.com/javascript/langchain/index/createAgent) when the `callModel` graph node receives a malformed list of messages. Specifically, it is malformed when there are `AIMessage`s with `tool_calls` (LLM requesting to call a tool) that do not have a corresponding [`ToolMessage`](https://reference.langchain.com/javascript/langchain-core/messages/ToolMessage) (result of a tool invocation to return to the LLM).

There could be a few reasons you're seeing this error:

1. You manually passed a malformed list of messages when invoking the graph, e.g. `graph.invoke({messages: [new AIMessage({..., tool_calls: [...]})]})`
2. The graph was interrupted before receiving updates from the `tools` node (i.e. a list of [`ToolMessage`](https://reference.langchain.com/javascript/langchain-core/messages/ToolMessage))
   and you invoked it with an input that is not null or a ToolMessage,
   e.g. `graph.invoke({messages: [new HumanMessage(...)]}, config)`.
   This interrupt could have been triggered in one of the following ways:
   * You manually set `interruptBefore: ['tools']` in `createAgent`
   * One of the tools raised an error that wasn't handled by the [`ToolNode`](https://reference.langchain.com/javascript/langchain-langgraph/prebuilt/ToolNode) (`"tools"`)

## Troubleshooting

To resolve this, you can do one of the following:

1. Don't invoke the graph with a malformed list of messages
2. In case of an interrupt (manual or due to an error) you can:

* provide `ToolMessage` objects that match existing tool calls and call `graph.invoke({messages: [new ToolMessage(...)]})`.
  **NOTE**: this will append the messages to the history and run the graph from the START node.
  * manually update the state and resume the graph from the interrupt:
    1. get the list of most recent messages from the graph state with `graph.getState(config)`
    2. modify the list of messages to either remove unanswered tool calls from AIMessages

or add `ToolMessage` objects with `toolCallId`s that match unanswered tool calls 3. call `graph.updateState(config, {messages: ...})` with the modified list of messages 4. resume the graph, e.g. call `graph.invoke(null, config)`

***

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