fix(prebuilt): catch asyncio.CancelledError in ToolNode to prevent INVALID_CHAT_HISTORY#6945
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Subham Singhania (Subhamsinghania18) wants to merge 1 commit intolangchain-ai:mainfrom
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…on paths asyncio.CancelledError was changed to inherit from BaseException (not Exception) in Python 3.8 (bpo-32528). ToolNode's async error handlers only caught Exception, so a task cancellation propagated unhandled, leaving the message history in an invalid state: AIMessage(tool_calls=[...]) <- no matching ToolMessage --> next LLM call raises INVALID_CHAT_HISTORY Two sites are fixed: 1. _execute_tool_async — the primary execution try/except block. A CancelledError handler is inserted between GraphBubbleUp (must always propagate) and the general Exception handler. When handle_tool_errors is truthy an error ToolMessage is returned to keep history valid; when it is falsy the error is re-raised unchanged. 2. _arun_one wrapper block — the outer try/except that wraps calls through _awrap_tool_call / _wrap_tool_call. Same logic applies. asyncio is already imported at the top of the module; no new imports are required. Closes: langchain-ai#6726
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asyncio.CancelledErrorwas changed to inherit fromBaseException(notException) in Python 3.8 (bpo-32528).ToolNode's async error handlersonly caught
Exception, so any task cancellation propagated unhandled,leaving the message history in an invalid state — an
AIMessagewithtool_callsbut no correspondingToolMessage. The next LLM call thenraised
INVALID_CHAT_HISTORY.Two sites are fixed:
_execute_tool_async— primary execution try/except block. ACancelledErrorhandler is inserted betweenGraphBubbleUp(must alwayspropagate) and the general
Exceptionhandler._arun_onewrapper block — the outer try/except wrapping_awrap_tool_call/_wrap_tool_call.When
handle_tool_errorsis truthy a proper errorToolMessageisreturned to keep chat history valid. When falsy the error is re-raised
unchanged — zero behaviour change for the default case.
asynciois already imported at the top of the module.Issue: #6726
Dependencies: None