fetchOptions.dispatcher not work for "undici": "^8.3.0"

[kiinoo]

Confirm this is a Node library issue and not an underlying OpenAI API issue

• This is an issue with the Node library

Describe the bug

code:

import { serve } from '@hono/node-server'
import { Hono } from 'hono'
import OpenAI from 'openai'
import { fetch, ProxyAgent } from 'undici';

const app = new Hono()

const proxyUrl = process.env.HTTPS_PROXY
  ?? process.env.HTTP_PROXY
  ?? process.env.https_proxy;

console.log(`proxy ${proxyUrl}`);

const dispatcher = proxyUrl ? new ProxyAgent(proxyUrl) : undefined;
console.log(`dispatcher ${!!dispatcher}`);

const client = new OpenAI({
  apiKey: process.env.OPENAI_API_KEY,
  fetchOptions: {
    dispatcher,
  }
})

app.post('/chat', async (c) => {
  const { message } = await c.req.json()

  const response =
    await client.chat.completions.create({
      model: 'gpt-4.1-mini',
      messages: [
        {
          role: 'user',
          content: message,
        },
      ],
    })

  return c.json({
    reply: response.choices[0].message.content,
  })
})

serve(
  {
    fetch: app.fetch,
    port: 3000,
  },
  () => {
    console.log(
      '🚀 Server running at http://localhost:3000',
    )
  },
)

error:

APIConnectionError: Connection error.
    at OpenAI.makeRequest (/Users/app/ai-code/node_modules/.pnpm/openai@6.38.0/node_modules/openai/src/client.ts:792:13)
    at async Array.<anonymous> (/Users/app/ai-code/src/index-openai-proxy.ts:43:5)
    at async responseViaResponseObject (/Users/app/ai-code/node_modules/.pnpm/@hono+node-server@2.0.2_hono@4.12.19/node_modules/@hono/node-server/dist/index.cjs:710:13)
    at async Server.<anonymous> (/Users/app/ai-code/node_modules/.pnpm/@hono+node-server@2.0.2_hono@4.12.19/node_modules/@hono/node-server/dist/index.cjs:808:11) {
  status: undefined,
  headers: undefined,
  requestID: undefined,
  error: undefined,
  code: undefined,
  param: undefined,
  type: undefined,
  cause: TypeError: fetch failed
      at node:internal/deps/undici/undici:13502:13
      at async OpenAI.fetchWithTimeout (/Users/app/ai-code/node_modules/.pnpm/openai@6.38.0/node_modules/openai/src/client.ts:969:14)
      at async OpenAI.fetchWithAuth (/Users/app/ai-code/node_modules/.pnpm/openai@6.38.0/node_modules/openai/src/client.ts:934:22)
      at async OpenAI.makeRequest (/Users/app/ai-code/node_modules/.pnpm/openai@6.38.0/node_modules/openai/src/client.ts:744:22)
      at async Array.<anonymous> (/Users/app/ai-code/src/index-openai-proxy.ts:43:5)
      at async responseViaResponseObject (/Users/app/ai-code/node_modules/.pnpm/@hono+node-server@2.0.2_hono@4.12.19/node_modules/@hono/node-server/dist/index.cjs:710:13)
      at async Server.<anonymous> (/Users/app/ai-code/node_modules/.pnpm/@hono+node-server@2.0.2_hono@4.12.19/node_modules/@hono/node-server/dist/index.cjs:808:11) {
    [cause]: InvalidArgumentError: invalid onRequestStart method
        at assertRequestHandler (/Users/app/ai-code/node_modules/.pnpm/undici@8.3.0/node_modules/undici/lib/core/util.js:568:11)
        at new Request (/Users/app/ai-code/node_modules/.pnpm/undici@8.3.0/node_modules/undici/lib/core/request.js:271:5)
        at [dispatch] (/Users/app/ai-code/node_modules/.pnpm/undici@8.3.0/node_modules/undici/lib/dispatcher/client.js:342:21)
        at Client.dispatch (/Users/app/ai-code/node_modules/.pnpm/undici@8.3.0/node_modules/undici/lib/dispatcher/dispatcher-base.js:171:29)
        at [dispatch] (/Users/app/ai-code/node_modules/.pnpm/undici@8.3.0/node_modules/undici/lib/dispatcher/pool-base.js:164:28)
        at Pool.dispatch (/Users/app/ai-code/node_modules/.pnpm/undici@8.3.0/node_modules/undici/lib/dispatcher/dispatcher-base.js:171:29)
        at [dispatch] (/Users/app/ai-code/node_modules/.pnpm/undici@8.3.0/node_modules/undici/lib/dispatcher/agent.js:138:23)
        at Agent.dispatch (/Users/app/ai-code/node_modules/.pnpm/undici@8.3.0/node_modules/undici/lib/dispatcher/dispatcher-base.js:171:29)
        at ProxyAgent.dispatch (/Users/app/ai-code/node_modules/.pnpm/undici@8.3.0/node_modules/undici/lib/dispatcher/proxy-agent.js:250:25)
        at node:internal/deps/undici/undici:11136:55 {
      code: 'UND_ERR_INVALID_ARG'
    }
  }
}

To Reproduce

1. run HTTPS_PROXY=http://127.0.0.1:8888 OPENAI_API_KEY=sk-proj-QA56X-*** npx tsx src/index.ts
2. run

curl -X POST http://localhost:3000/chat \
  -H "Content-Type: application/json" \
  -d '{"message":"what is AI"}'

Code snippets

OS

macOS

Node version

v22.14.0

Library version

^6.38.0