ng serve with esbuild/Vite ignores sourceMap configuration, injecting large inline source maps into all files

Reproduce the issue with ng new, angular.json, tsconfig.json, and ng serve, then inspect served JavaScript in the browser Network tools. Trace how the Vite/esbuild development-server path handles the sourceMap setting. Done means sourceMap false prevents inline Base64 maps in application and node_modules JavaScript files.

Command

serve

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

The development server (ng serve), which uses Vite/esbuild, consistently injects large, inline Base64 source maps into every JavaScript file it serves.

This behavior occurs even when source maps are explicitly disabled in angular.json and/or tsconfig.json. The most problematic aspect is that this transformation is also applied to pre-built, third-party packages from node_modules.

This unnecessarily inflates file sizes (often by 2-3x), which slows down page loads in development and makes debugging in browser DevTools more difficult due to the massive file content. The core issue is that the configuration to disable this behavior is not being respected.

Minimal Reproduction

1. Create a new Angular project:

   ng new sourcemap-repro
   cd sourcemap-repro
   

2. In angular.json, modify the configuration for the development server to explicitly disable all source maps. Under projects.sourcemap-repro.architect.build.configurations.development, set the sourceMap option:

   "sourceMap": false
   

   (Alternatively, using a more granular object like {"scripts": false, "styles": false, "vendor": false} also fails to prevent the issue.)

3. Run the development server:

   ng serve
   

4. Open the application in a browser and launch the developer tools (e.g., Chrome DevTools).

5. Navigate to the "Network" tab, refresh the page, and inspect any .js file (e.g., main.js, polyfills.js, or a chunk from @angular/core).

6. View the "Response" or "Source" for that file.

Expected Behavior:
The served JavaScript files should not contain an inline source map. The file should end without a //# sourceMappingURL=... comment.

Actual Behavior:
Every JavaScript file has a large inline Base64 source map appended to it, directly contradicting the configuration in angular.json.

Exception or Error

Your Environment

Angular CLI: 19.2.14
Node: 20.19.0
Package Manager: npm 10.8.2
OS: darwin arm64

Angular: undefined
...

Package                         Version
---------------------------------------------------------
@angular-devkit/architect       0.1902.15
@angular-devkit/build-angular   19.2.14
@angular-devkit/core            19.2.14
@angular-devkit/schematics      19.2.14
@angular/cli                    19.2.14
@angular/compiler               19.2.14
@angular/compiler-cli           19.2.14
@angular/language-service       19.2.14
@schematics/angular             18.2.11
ng-packagr                      18.2.1
typescript                      5.7.2
zone.js                         0.15.0

Anything else relevant?