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fix(langchain_v1): ToolNode initialization uses tool attributes in create_agent for middleware #33282

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fix(langchain_v1): ToolNode initialization uses tool attributes in create_agent for middleware #33282

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d363c3b
fix: ToolNode
keenborder786 Oct 5, 2025
afbaae7
Merge branch 'master' into fix/node_tool_middleware
keenborder786 Oct 6, 2025
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21 changes: 19 additions & 2 deletions libs/langchain_v1/langchain/agents/middleware_agent.py
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Original file line number Diff line number Diff line change
Expand Up @@ -35,6 +35,7 @@
)
from langchain.chat_models import init_chat_model
from langchain.tools import ToolNode
from langchain.tools.tool_node import ToolInvocationError

STRUCTURED_OUTPUT_ERROR_TEMPLATE = "Error: {error}\n Please fix your mistakes."

Expand Down Expand Up @@ -174,6 +175,12 @@ def _handle_structured_output_error(
return False, ""


def _default_handle_tool_errors(e: Exception) -> str:
if isinstance(e, ToolInvocationError):
return e.message
raise e


def create_agent( # noqa: PLR0915
*,
model: str | BaseChatModel,
Expand Down Expand Up @@ -231,7 +238,7 @@ def create_agent( # noqa: PLR0915
if isinstance(tools, list):
# Extract built-in provider tools (dict format) and regular tools (BaseTool)
built_in_tools = [t for t in tools if isinstance(t, dict)]
regular_tools = [t for t in tools if not isinstance(t, dict)]
regular_tools = [t for t in tools if isinstance(t, BaseTool)]

# Tools that require client-side execution (must be in ToolNode)
available_tools = middleware_tools + regular_tools
Expand All @@ -248,7 +255,17 @@ def create_agent( # noqa: PLR0915
if tool_node:
# Add middleware tools to existing ToolNode
available_tools = list(tool_node.tools_by_name.values()) + middleware_tools
tool_node = ToolNode(available_tools)
tool_node = ToolNode(
tools=available_tools,
name=tool_node.name if tool_node else "tools",
tags=list(tool_node.tags) if tool_node and tool_node.tags else None,
handle_tool_errors=tool_node._handle_tool_errors
if tool_node and tool_node._handle_tool_errors
else _default_handle_tool_errors,
messages_key=tool_node._messages_key
if tool_node and tool_node._messages_key
else "messages",
)

# default_tools includes all client-side tools (no built-ins or structured tools)
default_tools = available_tools
Expand Down
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