feat(openai): add support for apply patch tool

[christian-bromann]

This PR adds support for OpenAI's apply_patch tool, which allows models to propose structured diffs for creating, updating, and deleting files in a codebase. This enables iterative, multi-step code editing workflows.

Usage

import { ChatOpenAI, tools } from "@langchain/openai";
import { applyDiff } from "@openai/agents";
import * as fs from "fs/promises";

const model = new ChatOpenAI({ model: "gpt-5.1" });

const patchTool = tools.applyPatch({
  execute: async (operation) => {
    if (operation.type === "create_file") {
      const content = applyDiff("", operation.diff, "create");
      await fs.writeFile(operation.path, content);
      return `Created ${operation.path}`;
    }
    if (operation.type === "update_file") {
      const current = await fs.readFile(operation.path, "utf-8");
      const newContent = applyDiff(current, operation.diff);
      await fs.writeFile(operation.path, newContent);
      return `Updated ${operation.path}`;
    }
    if (operation.type === "delete_file") {
      await fs.unlink(operation.path);
      return `Deleted ${operation.path}`;
    }
    return "Unknown operation type";
  },
});

const llmWithPatch = model.bindTools([patchTool]);
const response = await llmWithPatch.invoke(
  "Rename the fib() function to fibonacci()"
);

[changeset-bot]

🦋 Changeset detected

Latest commit: 9ac949f

The changes in this PR will be included in the next version bump.

This PR includes changesets to release 5 packages

Name	Type
@langchain/openai	Minor
@langchain/classic	Patch
@langchain/community	Patch
@langchain/deepseek	Patch
@langchain/xai	Patch

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