mergeMessageRuns

import { mergeMessageRuns, AIMessage, HumanMessage, SystemMessage, ToolCall } from "@langchain/core/messages";

const messages = [
  new SystemMessage("you're a good assistant."),
  new HumanMessage({ content: "what's your favorite color", id: "foo" }),
  new HumanMessage({ content: "wait your favorite food", id: "bar" }),
  new AIMessage({
    content: "my favorite colo",
    tool_calls: [{ name: "blah_tool", args: { x: 2 }, id: "123" }],
    id: "baz",
  }),
  new AIMessage({
    content: [{ type: "text", text: "my favorite dish is lasagna" }],
    tool_calls: [{ name: "blah_tool", args: { x: -10 }, id: "456" }],
    id: "blur",
  }),
];

mergeMessageRuns(messages);