@hono/node-server/vercel: POST requests hang (no response) on Vercel Node runtime while GET works

[leohahn]

What version of Hono?

• hono@4.11.9
• @hono/node-server@1.19.9

What version of Node.js?

• Vercel function runtime nodejs24.x

What happened?

Using the official Vercel adapter from @hono/node-server/vercel:

import { handle } from '@hono/node-server/vercel'
import app from '../apps/api/src/server.js'

export default handle(app)

in a Vercel function (api/server.ts) with rewrites (/api/* and /rpc/* -> /api/server), GET requests work, but POST requests never return a response (client times out).

Repro matrix from Preview deployment:

Case	Method	Path	Result
health	GET	/api/health (separate function)	200
slack-url-verification	POST	/api/slack	timeout (curl exit 28 after 25s)
slack-interactivity-invalid-signature	POST	/api/slack/interactivity	timeout (curl exit 28 after 25s)
rpc-ping-no-csrf	POST	/rpc/ping	timeout (curl exit 28 after 25s)
rpc-ping-csrf-no-auth	POST	/rpc/ping	timeout (curl exit 28 after 25s)

When we switch back to a custom Node IncomingMessage/ServerResponse bridge that buffers the request body and calls app.fetch(request), the same POST routes return immediately with expected app-level responses.

Minimal reproduction steps

1. Deploy a Vite + Hono app on Vercel with:
   • API function at api/server.ts
   • rewrites /api/:path((?!health$|server$).*) -> /api/server and /rpc/(.*) -> /api/server
2. Use @hono/node-server/vercel handle(app) as above
3. Call POST route (JSON or form-encoded) via Preview URL
4. Observe no response body/status until client timeout

Expected

POST routes should behave like GET routes and return app responses.

Actual

POST routes hang indefinitely on Vercel Node runtime.

Additional context

• Using hono/vercel in this same Node function setup also hangs, but that appears to be a signature mismatch (Request handler in Node req/res runtime).
• The issue here is specifically with the Node-targeted Vercel adapter from @hono/node-server/vercel.

[venarius]

+1 Same Issue here

My solution:

// @ts-nocheck — pre-built backend bundle has no type declarations
import type { IncomingMessage, ServerResponse } from 'http';

import app from '../apps/backend/dist/app.js';

export default async function handler(req: IncomingMessage, res: ServerResponse) {
  const proto = req.headers['x-forwarded-proto'] || 'https';
  const host = req.headers['x-forwarded-host'] || req.headers.host;
  const url = new URL(req.url!, `${proto}://${host}`);

  const headers = new Headers();
  for (const [key, value] of Object.entries(req.headers)) {
    if (value) headers.set(key, Array.isArray(value) ? value.join(', ') : value);
  }

  const init: RequestInit = { method: req.method, headers };

  if (req.method !== 'GET' && req.method !== 'HEAD') {
    init.body = await readBody(req);
  }

  const request = new Request(url.toString(), init);
  const response = await app.fetch(request);

  const respHeaders: Record<string, string[] | string> = {};
  response.headers.forEach((value, key) => {
    const existing = respHeaders[key];
    if (existing) {
      respHeaders[key] = Array.isArray(existing) ? [...existing, value] : [existing, value];
    } else {
      respHeaders[key] = value;
    }
  });

  res.writeHead(response.status, respHeaders);

  if (response.body) {
    const reader = response.body.getReader();
    let chunk = await reader.read();
    while (!chunk.done) {
      res.write(chunk.value);
      chunk = await reader.read();
    }
  }

  res.end();
}

function readBody(req: IncomingMessage): Promise<Buffer> {
  return new Promise((resolve, reject) => {
    const chunks: Buffer[] = [];
    req.on('data', (chunk: Buffer) => chunks.push(chunk));
    req.on('end', () => resolve(Buffer.concat(chunks)));
    req.on('error', reject);
  });
}

export const config = {
  api: {
    bodyParser: false,
  },
};

[yusukebe]

Hi @leohahn @venarius

Honestly, I'm not familiar with Vercel recently, but is there any case to use @hono/node-server/vercel when Vercel already supports Hono apps natively? https://vercel.com/docs/frameworks/backend/hono