Parallel tool calls merge bug could corrupt tool execution results

langchain-core 1.2.14 fixes merge_lists incorrectly merging parallel tool calls, which could cause tool execution results to be corrupted or misattributed when multiple tools run concurrently. Affected all versions prior to 1.2.14.

Upgrade to langchain-core 1.2.14 immediately if using parallel tool calling. Review historical tool execution logs for anomalous results where tool outputs don't match expected tool inputs. Monitor langchain_tool_error rate for unexpected spikes.