fix(anthropic): unhandled tool choice 'none'

[ghdcksgml1]

Summary

Fix missing 'none' tool choice handling in ChatAnthropic

Bug Example

import {ChatAnthropic} from "@langchain/anthropic";
import {z} from "zod";
import {tool} from "@langchain/core/tools";

const adderTool = tool(
  async ({a, b}) => {
    return a + b;
  },
  {
    name: "add",
    description: "Adds a and b",
    schema: z.object({
      a: z.number(),
      b: z.number(),
    }),
  }
);

const runner = async () => {
  const tools = [adderTool];

  const llm = new ChatAnthropic({
    model: "claude-4-sonnet-20250514",
  });
  const llmWithTools = llm.bindTools(tools, {tool_choice: "none"});

  let result = await llmWithTools.invoke([
    {
      role: "user",
      content: "please 2 + 3"
    }
  ]);

  console.log("tool_calls: " + result.tool_calls);
};
runner().catch(console.error);

// expect => tool_calls: []
// actual => BadRequestError: 400 {"type":"error","error":{"type":"invalid_request_error","message":"Tool 'none' not found in provided tools"},"request_id":"req_011CT..."}

Details

The Anthropic integration didn't handle tool_choice: "none" option. Users couldn't disable tool calling when needed.

Added the missing case in handleToolChoice() function to map "none" to { type: "none" } format that Anthropic's API expects.

reference: https://docs.anthropic.com/en/docs/agents-and-tools/tool-use/implement-tool-use

Impact

✅ tool_choice: "none" now works
✅ No tools called when set to "none"
✅ Test added to verify behavior

[changeset-bot]

🦋 Changeset detected

Latest commit: 417dd42

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

This PR includes changesets to release 1 package

Name	Type
@langchain/anthropic	Patch

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Project	Deployment	Preview	Comments	Updated (UTC)
langchainjs-docs	Ready	Preview		Sep 11, 2025 7:59pm

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[hntrl]

Good catch! Thanks @ghdcksgml1!