Command

build

Is this a regression?

• Yes, this behavior used to work in the previous version

The previous version in which this bug was not present was

No response

Description

Including any js/ts file in the polyfills array causes the angular server to incorrectly identify the app as a non-zoneless app. Thus it tries to include zone.js, which is deleted, because I uninstall the package as per the guide.

Minimal Reproduction

Exception or Error

Your Environment

Angular CLI: 20.1.0
Node: 22.14.0
Package Manager: pnpm 10.13.1
OS: linux x64
Angular: 20.1.0
... animations, build, cdk, cli, common, compiler, compiler-cli
... core, forms, language-service, material
... material-luxon-adapter, platform-browser
... platform-browser-dynamic, platform-server, router, ssr
Package Version
---------------------------------------------------------
@angular-devkit/architect 0.2001.0
@angular-devkit/build-angular 20.1.0
@angular-devkit/core 20.1.0
@angular-devkit/schematics 20.1.0
@schematics/angular 20.0.6
ng-packagr 20.0.1
rxjs 7.8.1
typescript 5.8.3

Anything else relevant?

TLDR

This is essentially a re-open of #28898. Developers are forced to avoid adding any js/ts file to the polyfills array. Instead, they have to create js scripts inline inside index.html, or write js files, and include them as assets with index.html

The problem is within these lines:

The presence of any js/ts file in the polyfills array causes zone to be included, even though I uninstalled zone.js and do everything zone-less-ly.

I had a file called polyfill-buffer.ts which I used to add to the polyfill array:

import { Buffer } from 'buffer';
if (!globalThis.Buffer) {
 Object.assign(globalThis, { Buffer });
}

Now I have to add it to index.html as a script

import { Buffer } from 'https://cdn.jsdelivr.net/npm/buffer/+esm';
if (!globalThis.Buffer) {
 Object.assign(globalThis, { Buffer });
}

This is maintainable for small scripts like these. But it eliminates the possibility of using any file-based polyfill stuff.