@angular/cli v20. NPM cannot resolve @angular/fire

Empieza con el package.json indicado y reproduce tanto ng add @angular/fire como npm i @angular/fire usando las versiones indicadas de Angular 20.1.x, Firebase 12.1.0, Node 22.18.0 y npm 10.9.3. Inspecciona las dependencias peer de @angular/fire@20.0.1 y compáralas con los paquetes de Angular resueltos. Se considera completado cuando un proyecto nuevo de Angular 20 puede instalar @angular/fire sin --force ni --legacy-peer-deps.

I'm trying to install @angular/fire to my Angular 20 project, but NPM won't resolve the package.

package.json

{
  "name": "my-project",
  "version": "0.0.0",
  "scripts": {
    "ng": "ng",
    "start": "ng serve",
    "build": "ng build",
    "watch": "ng build --watch --configuration development",
    "test": "ng test"
  },
  "prettier": {
    "overrides": [
      {
        "files": "*.html",
        "options": {
          "parser": "angular"
        }
      }
    ]
  },
  "private": true,
  "dependencies": {
    "@angular/common": "^20.1.0",
    "@angular/compiler": "^20.1.0",
    "@angular/core": "^20.1.0",
    "@angular/forms": "^20.1.0",
    "@angular/platform-browser": "^20.1.0",
    "@angular/router": "^20.1.0",
    "@ng-select/ng-select": "^20.1.2",
    "firebase": "^12.1.0",
    "rxjs": "~7.8.0",
    "tslib": "^2.3.0",
    "zone.js": "~0.15.0"
  },
  "devDependencies": {
    "@angular/build": "^20.1.5",
    "@angular/cli": "^20.1.5",
    "@angular/compiler-cli": "^20.1.0",
    "@types/jasmine": "~5.1.0",
    "jasmine-core": "~5.8.0",
    "karma": "~6.4.0",
    "karma-chrome-launcher": "~3.2.0",
    "karma-coverage": "~2.2.0",
    "karma-jasmine": "~5.1.0",
    "karma-jasmine-html-reporter": "~2.1.0",
    "typescript": "~5.8.2"
  }
}

I'm using the add command
ng add @angular/fire

Output

√ Determining Package Manager
  › Using package manager: npm
√ Searching for compatible package version
  › Found compatible package version: @angular/fire@20.0.1.
√ Loading package information from registry
√ Confirming installation
× Unable to install package

npm error code ERESOLVE
npm error ERESOLVE could not resolve
npm error
npm error While resolving: my-project@0.0.0
npm error Found: @angular/core@20.1.6
npm error node_modules/@angular/core
npm error   peerOptional @angular/core@"^20.0.0" from @angular/build@20.1.5
npm error   node_modules/@angular/build
npm error     dev @angular/build@"^20.1.5" from the root project
npm error   peer @angular/core@"20.1.6" from @angular/common@20.1.6
npm error   node_modules/@angular/common
npm error     peer @angular/common@"20.1.6" from @angular/forms@20.1.6
npm error     node_modules/@angular/forms
npm error       peer @angular/forms@"^20.0.0" from @ng-select/ng-select@20.1.2
npm error       node_modules/@ng-select/ng-select
npm error         @ng-select/ng-select@"^20.1.2" from the root project
npm error       1 more (the root project)
npm error     peer @angular/common@"20.1.6" from @angular/platform-browser@20.1.6
npm error     node_modules/@angular/platform-browser
npm error       peerOptional @angular/platform-browser@"^20.0.0" from @angular/build@20.1.5
npm error       node_modules/@angular/build
npm error         dev @angular/build@"^20.1.5" from the root project
npm error       3 more (@angular/forms, @angular/router, the root project)
npm error     3 more (@angular/router, @ng-select/ng-select, the root project)
npm error   5 more (@angular/forms, @angular/platform-browser, ...)
npm error
npm error Could not resolve dependency:
npm error @angular/fire@"20.0.1" from the root project
npm error
npm error Conflicting peer dependency: @angular/core@20.1.7
npm error node_modules/@angular/core
npm error   peer @angular/core@"20.1.7" from @angular/platform-browser-dynamic@20.1.7
npm error   node_modules/@angular/platform-browser-dynamic
npm error     peer @angular/platform-browser-dynamic@"^20.0.0" from @angular/fire@20.0.1
npm error     node_modules/@angular/fire
npm error       @angular/fire@"20.0.1" from the root project
npm error
npm error Fix the upstream dependency conflict, or retry
npm error this command with --force or --legacy-peer-deps
npm error to accept an incorrect (and potentially broken) dependency resolution.
npm error
npm error
npm error For a full report see:
npm error C:\Users\Marco\AppData\Local\npm-cache\_logs\2025-08-15T19_42_39_683Z-eresolve-report.txt
npm error A complete log of this run can be found in: C:\Users\Marco\AppData\Local\npm-cache\_logs\2025-08-15T19_42_39_683Z-debug-0.log

Angular version

Angular CLI: 20.1.5                                     
Node: 22.18.0                                           
Package Manager: npm 10.9.3                             
OS: win32 x64                                           
                                                        
Angular: 20.1.6                                         
... common, compiler, compiler-cli, core, forms         
... platform-browser, router                            
                                                        
Package                      Version                    
------------------------------------------------------  
@angular-devkit/architect    0.2001.5                   
@angular-devkit/core         20.1.5                     
@angular-devkit/schematics   20.1.5                     
@angular/build               20.1.5                     
@angular/cli                 20.1.5                     
@schematics/angular          20.1.5                     
rxjs                         7.8.2                      
typescript                   5.8.3                      
zone.js                      0.15.1

Same thing happens if I install directly with npm

npm i @angular/fire