LangGraph ToolNode Tests Breaking Since v1.0.2: Causes and Fixes Explained

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Since the release of langgraph-prebuilt 1.0.2 in October 2025, developers have reported silent and explicit test failures in LangGraph ToolNode unit tests due to undocumented breaking changes. The update introduced a required runtime parameter to ToolNode internals, causing ValueError crashes when invoking ToolNode outside a compiled graph without injecting a Runtime() context. Additionally, the default value of handle_tool_errors quietly reverted from True to False, causing tools to fail silently in production without raising exceptions. Async tool functions not accepting **kwargs also began crashing with TypeError, as LangGraph now injects runtime as a keyword argument into all callables. As of September 2026, key related issues remain open against LangGraph v1.2.11, and developers are advised to explicitly pass Runtime(), handle_tool_errors=True, and use **kwargs in async tool signatures as permanent fixes.

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