high93%
core: finalize_tool_call_chunk coerces id=None to empty string, collapsing parallel id-less tool calls
langchain-core's finalize_tool_call_chunk maps missing tool_call id (None) to "" in the tool_call and server_tool_call branches, causing multiple id-less parallel tool calls to share the same empty id and collide downstream (e.g., deepagents FilesystemMiddleware offloads all to /large_tool_results/unknown). The proposed fix replaces the empty-string fallback with uuid4().hex to guarantee distinct ids.