Error in cloudflare workers : Uncaught (in response) Error: The script will never generate a response

TL;DR

For "A hanging Promise was canceled. This happens when the worker runtime is waiting for a Promise from JavaScript to resolve, but has detected t": this happens when the worker runtime is waiting for a Promise from JavaScript to resolve, but has detected that the Promise cannot possibly ever resolve because all code and events related to the Promise's I/O context have already finished. ✘ [ERROR] Uncaught (in response) Error: The script will never generate a response. My code is simple ` import { Client } from '@neondatabase/serverless' import { Env } from './models' export default { async f

A hanging Promise was canceled. This happens when the worker runtime is waiting for a Promise from JavaScript to resolve, but has detected that the Promise cannot possibly ever resolve because all code and events related to the Promise's I/O context have already finished. ✘ [ERROR] Uncaught (in response) Error: The script will never generate a response.

Steps

1. Issue neondatabase/serverless#11 (closed, 17 comments): Hi I’m getting the following error in Cloudflare workers

A hanging Promise was canceled. This happens when the worker runtime is waiting for a Promise from JavaScript to resolve, but has detected that the Promise cannot possibly ever resolve because all code and events related to the Promise's I/O context have already finished. ✘ [ERROR] Uncaught (in response) Error: The script will never generate a response.

2. `

import { Client } from '@neondatabase/serverless' import { Env } from './models'

3. export default { async fetch(request: Request, env: Env

When to use

You are seeing this: Issue neondatabase/serverless#11 (closed, 17 comments): Hi I’m getting the following error in Cloudflare workers `` A hanging Promise was canceled. Use this skill when you run into "Error in cloudflare workers : Uncaught (in response) Error: The script will never generate a response".

When not to use

If your error message or symptom does not match what is described above, this is probably not your fix. Search for your exact error text instead of forcing this one to fit.

Versions

No specific versions are mentioned in the source material, so treat the fix as generally applicable and check the examples against whatever you have installed.

Why this happens

The original report does not dig into a root cause. It documents the symptom and the fix that resolved it.

Asked in gh:neondatabase/serverless#11 (https://github.com/neondatabase/serverless/issues/11): Error in cloudflare workers : Uncaught (in response) Error: The script will never generate a response. The issue report: Issue neondatabase/serverless#11 (closed, 17 comments): Hi I’m getting the following error in Cloudflare workers

A hanging Promise was canceled. This happens when the worker runtime is waiting for a Promise from JavaScript to resolve, but has detected that the Promise cannot possibly ever resolve because all code and events related to the Promise's I/O context have already finished. ✘ [ERROR] Uncaught (in response) Error: The script will never generate a response.

My code is simple

import { Client } from '@neondatabase/serverless'
import { Env } from './models'

export default {
    async fetch(request: Request, env: Env The verified answer: [jawj (maintainer)]: Do not keep a Pool/Client alive between requests on Cloudflare Workers  -  each invocation is isolated and the worker kills promises tied to a finished request's I/O context ('The script will never generate a response'). Create the Pool inside the fetch/request handler. Same symptom occurs locally when the connection string env var is undefined (put env vars in `.dev.vars` for `wrangler dev`), and newer driver versions surface connect errors more helpfully instead of hanging.