Unable to build angular project due to error: The error output was: Option “vendorSourceMap” is deprecated

Full error message –

AggregateException: One or more errors occurred. (One or more errors occurred. (The npm script ‘start’ exited without indicating that the Angular CLI was listening for requests. The error output was: This version of CLI is only compatible with Angular versions ^11.0.0-beta || >=11.0.0 <12.0.0,

but Angular version 8.0.0 was found instead.

Please visit the link below to find instructions on how to update Angular.


**When researching this issue most solutions state to change the angular.json file to
“architect”: {
“build”: {
“builder”: “@angular-devkit/build-angular:browser”,
“options”: {
“sourceMap”: {
“scripts”: true,
“styles”: true,
“vendor”: true

But when I check my angular.json file all I see is:

“architect”: {
“build”: {
“builder”: “@angular-devkit/build-angular:browser”,
“options”: {
“progress”: true,
“extractCss”: true,
“outputPath”: “dist”,
“index”: “src/index.html”,
“main”: “src/main.ts”,
“polyfills”: “src/polyfills.ts”,
“tsConfig”: “src/tsconfig.app.json”,
“assets”: [

I’ve been dealing with this error for a while so any solutions or assistance are appreciated. Thanks!


Thank you for visiting the Q&A section on Magenaut. Please note that all the answers may not help you solve the issue immediately. So please treat them as advisements. If you found the post helpful (or not), leave a comment & I’ll get back to you as soon as possible.

Method 1

The correct angular.json options are

"serve": {
  "builder": "@angular-devkit/build-angular:dev-server",
  "options": {
    "sourceMap": {
      "scripts": true,
      "styles": true,
      "vendor": true

Verified on 10.0.. (Updated verfied version from 7.2.15 > 10.0.)

Method 2

Actually I fixed this issue by including the following dependencies and devDependencies in my package.json file… I then ran npm install in both my project root and ClientApp folder.
The only reason I’m not accepting this as the main answer is because the answer accepted as solution is included in similar issues, I did make that change and perhaps that also had to do with the resolve.

"dependencies": {
    "@angular/common": "~11.0.5",
    "@angular/compiler": "~11.0.5",
    "@angular/core": "~11.0.5",
    "@angular/forms": "~11.0.5",
    "@angular/platform-browser": "~11.0.5",
    "@angular/platform-browser-dynamic": "~11.0.5",
    "@angular/router": "~11.0.5",
    "zone.js": "^~0.10.3"
  "devDependencies": {
    "@angular-devkit/build-angular": "^0.1100.5",
    "@angular/cli": "^11.0.5",
    "@angular/compiler": "^11.0.5",
    "@angular/compiler-cli": "^11.0.5"

All methods was sourced from stackoverflow.com or stackexchange.com, is licensed under cc by-sa 2.5, cc by-sa 3.0 and cc by-sa 4.0

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