@@ -112,6 +112,44 @@ jobs:
       - name: Test browser
         run: npm run test:${{ matrix.browser }}
 
+  # The package is built against firebase 12, the oldest major the peer range accepts. This job
+  # runs that build's specs against firebase 13. firebase 13 requires Node 24.12 or newer.
+  firebase-13:
+    runs-on: ubuntu-latest
+    needs: build
+    name: Test firebase 13
+    steps:
+      - name: Checkout
+        uses: actions/checkout@9c091bb21b7c1c1d1991bb908d89e4e9dddfe3e0 # v7.0.0
+        with:
+          persist-credentials: false
+      - name: Setup node
+        uses: actions/setup-node@48b55a011bda9f5d6aeb4c2d9c7362e8dae4041e # v6.4.0
+        with:
+          node-version: '>=24.15.0 <25'
+          check-latest: false
+      - name: Setup java
+        uses: actions/setup-java@1bcf9fb12cf4aa7d266a90ae39939e61372fe520 # v5.4.0
+        with:
+          distribution: 'temurin'
+          java-version: '21'
+      - name: Install deps
+        run: |
+          npm ci
+          npm install --no-save firebase@13.1.0
+          node -e "const version = require('firebase/package.json').version; console.log('firebase', version); process.exit(version === '13.1.0' ? 0 : 1)"
+      - name: Download Artifacts
+        uses: actions/download-artifact@3e5f45b2cfb9172054b4087a40e8e0b5a5461e7c # v8.0.1
+        with:
+          name: angularfire-${{ github.run_id }}
+          path: dist
+      - name: Test Node
+        run: |
+          npm run build:jasmine
+          npm run test:node
+      - name: Test headless
+        run: npm run test:chrome-headless
+
   contribute:
     runs-on: ${{ matrix.os }}
     name: Contribute Node ${{ matrix.node }} (${{ matrix.os }})
@@ -154,14 +192,14 @@ jobs:
   test_and_contribute:
     runs-on: ubuntu-latest
     name: Branch protection
-    needs: ['test', 'contribute', 'browser']
+    needs: ['test', 'contribute', 'browser', 'firebase-13']
     steps:
       - run: true
 
   publish:
     runs-on: ubuntu-latest
     name: Publish (NPM)
-    needs: ['build', 'test', 'browser']
+    needs: ['build', 'test', 'browser', 'firebase-13']
     if: ${{ github.ref == 'refs/heads/main' || github.event_name == 'release' }}
     # One npm publish at a time, each held until npm lists it (about 20 minutes at most), so every
     # check below reads what the previous publish wrote.
 
@@ -72,7 +72,7 @@
     "jsonc-parser": "^3.0.0",
     "open": "^7.0.3 || ^8.0.0",
     "ora": "^5.3.0",
-    "rxfire": "^6.2.0",
+    "rxfire": "^6.3.0",
     "rxjs": "~7.8.0",
     "semver": "^7.1.3",
     "triple-beam": "^1.3.0",
 
@@ -31,7 +31,7 @@
     "@angular/common": "^22.0.0",
     "@angular/core": "^22.0.0",
     "@angular/platform-browser": "^22.0.0",
-    "firebase": "^12.18.0",
+    "firebase": "^12.18.0 || ^13.0.0",
     "rxjs": "~7.8.0",
     "firebase-tools": "^14.0.0 || ^15.0.0",
     "typescript": ">=6.0 <6.1"
@@ -41,7 +41,7 @@
     "typescript": { "optional": true }
   },
   "dependencies": {
-    "rxfire": "^6.2.0",
+    "rxfire": "^6.3.0",
     "@angular-devkit/architect": ">= 0.2200.0 < 0.2300.0",
     "tslib": "^2.3.0"
   },
 
@@ -1,8 +1,17 @@
-import { readFileSync } from 'fs';
-import { logging } from '@angular-devkit/core';
+import { mkdirSync, mkdtempSync, readFileSync, rmdirSync, writeFileSync } from 'fs';
+import { tmpdir } from 'os';
+import { join } from 'path';
+import { logging, normalize, virtualFs } from '@angular-devkit/core';
+import { NodeJsSyncHost } from '@angular-devkit/core/node';
 import { HostTree, SchematicContext } from '@angular-devkit/schematics';
 import { minVersion as semverMinVersion } from 'semver';
-import { alignFirebaseVersion, firebaseVersionRange, pinInstalledPrereleaseVersion } from './common.js';
+import {
+  alignFirebaseVersion,
+  firebase13VersionRange,
+  firebaseVersionRange,
+  pinInstalledPrereleaseVersion,
+  supportedFirebaseRange,
+} from './common.js';
 import 'jasmine';
 
 const context = { logger: new logging.Logger('test') } as unknown as SchematicContext;
@@ -135,6 +144,11 @@ const treeWithFirebase = (firebaseVersion?: string, section = 'dependencies') =>
   return tree;
 };
 
+const withInstalledFirebase = (tree: HostTree, version: string) => {
+  tree.create('node_modules/firebase/package.json', JSON.stringify({ name: 'firebase', version }));
+  return tree;
+};
+
 describe('alignFirebaseVersion', () => {
 
   it('rewrites a previous-major range', () => {
@@ -214,9 +228,116 @@ describe('alignFirebaseVersion', () => {
     expect(sectionIn(tree, 'devDependencies').firebase).toBe(firebaseVersionRange);
   });
 
+  it('leaves a firebase 13 range untouched', () => {
+    for (const declared of ['^13.0.0', '^13.1.0', '~13.1.0', supportedFirebaseRange]) {
+      const tree = treeWithFirebase(declared);
+      expect(alignFirebaseVersion(tree, context)).withContext(declared).toBeFalse();
+      expect(dependenciesIn(tree).firebase).withContext(declared).toBe(declared);
+    }
+  });
+
+  it('rewrites an out-of-range entry that starts at firebase 13 to the 13 range, not back to 12', () => {
+    for (const declared of ['>=13.0.0', '^13.0.0-20260929163754']) {
+      const tree = treeWithFirebase(declared);
+      expect(alignFirebaseVersion(tree, context)).withContext(declared).toBeTrue();
+      expect(dependenciesIn(tree).firebase).withContext(declared).toBe(firebase13VersionRange);
+    }
+  });
+
+  it('rewrites an out-of-range entry that reaches below firebase 13 to the 12 range when nothing is installed', () => {
+    for (const declared of ['*', '>=12.18.0']) {
+      const tree = treeWithFirebase(declared);
+      expect(alignFirebaseVersion(tree, context)).withContext(declared).toBeTrue();
+      expect(dependenciesIn(tree).firebase).withContext(declared).toBe(firebaseVersionRange);
+    }
+  });
+
+  it('adds the range of the firebase major already installed', () => {
+    for (const [installed, expected] of [['13.1.0', firebase13VersionRange], ['12.19.0', firebaseVersionRange]]) {
+      const tree = withInstalledFirebase(treeWithFirebase(undefined), installed);
+      expect(alignFirebaseVersion(tree, context)).withContext(installed).toBeTrue();
+      expect(dependenciesIn(tree).firebase).withContext(installed).toBe(expected);
+    }
+  });
+
+  it('rewrites an out-of-range entry to the range of the firebase major already installed', () => {
+    for (const [installed, expected] of [['13.1.0', firebase13VersionRange], ['12.19.0', firebaseVersionRange]]) {
+      const tree = withInstalledFirebase(treeWithFirebase('*'), installed);
+      expect(alignFirebaseVersion(tree, context)).withContext(installed).toBeTrue();
+      expect(dependenciesIn(tree).firebase).withContext(installed).toBe(expected);
+    }
+  });
+
+  it('falls back to the declared range when the installed firebase is outside both majors', () => {
+    for (const [installed, declared, expected] of [
+      ['11.10.0', '^11.0.0', firebaseVersionRange],
+      ['13.0.0-20260929163754', '^13.0.0-20260929163754', firebase13VersionRange],
+    ]) {
+      const tree = withInstalledFirebase(treeWithFirebase(declared), installed);
+      expect(alignFirebaseVersion(tree, context)).withContext(installed).toBeTrue();
+      expect(dependenciesIn(tree).firebase).withContext(installed).toBe(expected);
+    }
+  });
+
+  it('ignores an installed copy that the workspace entry excludes', () => {
+    for (const [installed, declared, expected] of [
+      ['13.1.0', '~12.10.0', firebaseVersionRange],
+      ['12.19.0', '>=13.0.0', firebase13VersionRange],
+    ]) {
+      const tree = withInstalledFirebase(treeWithFirebase(declared), installed);
+      expect(alignFirebaseVersion(tree, context)).withContext(declared).toBeTrue();
+      expect(dependenciesIn(tree).firebase).withContext(declared).toBe(expected);
+    }
+  });
+
+  it('finds firebase installed at a monorepo root above the workspace', () => {
+    const repository = mkdtempSync(join(tmpdir(), 'angularfire-monorepo-'));
+    try {
+      const workspace = join(repository, 'apps', 'web');
+      mkdirSync(workspace, { recursive: true });
+      mkdirSync(join(repository, 'node_modules', 'firebase'), { recursive: true });
+      writeFileSync(join(repository, 'node_modules', 'firebase', 'package.json'),
+        JSON.stringify({ name: 'firebase', version: '13.1.0', exports: { './package.json': './package.json' } }));
+      writeFileSync(join(workspace, 'package.json'), JSON.stringify({ name: 'web' }));
+      // The host `ng add` and `ng update` give a schematic: the real filesystem, scoped to the workspace.
+      const tree = new HostTree(new virtualFs.ScopedHost(new NodeJsSyncHost(), normalize(workspace)));
+      expect(alignFirebaseVersion(tree, context)).toBeTrue();
+      expect(dependenciesIn(tree).firebase).toBe(firebase13VersionRange);
+    } finally {
+      // rmdirSync, not rmSync: this repo's @types/node predates fs.rmSync.
+      rmdirSync(repository, { recursive: true });
+    }
+  });
+
+  it('ignores an installed firebase manifest it cannot read', () => {
+    const tree = treeWithFirebase(undefined);
+    tree.create('node_modules/firebase/package.json', 'not json');
+    expect(alignFirebaseVersion(tree, context)).toBeTrue();
+    expect(dependenciesIn(tree).firebase).toBe(firebaseVersionRange);
+  });
+
+  it('mentions the supported range when it rewrites an entry', () => {
+    const infoSpy = spyOn(context.logger, 'info');
+    alignFirebaseVersion(treeWithFirebase('^11.0.0'), context);
+    expect(infoSpy).toHaveBeenCalledWith(jasmine.stringContaining(supportedFirebaseRange));
+  });
+
   it('matches the firebase range the library declares as its peer dependency', () => {
     const libraryManifest = JSON.parse(readFileSync('src/package.json', 'utf8'));
-    expect(libraryManifest.peerDependencies.firebase).toBe(firebaseVersionRange);
+    expect(libraryManifest.peerDependencies.firebase).toBe(supportedFirebaseRange);
+  });
+
+  it('builds against the oldest firebase major the peer dependency accepts', () => {
+    /* tools/build.ts imports wrapped functions by name from the installed firebase, so building
+     * on a newer major can emit an import that the older major does not export. */
+    const rootManifest = JSON.parse(readFileSync('package.json', 'utf8'));
+    expect(semverMinVersion(rootManifest.dependencies.firebase)?.major)
+      .toBe(semverMinVersion(supportedFirebaseRange)?.major);
+  });
+
+  it('writes a range for exactly the majors the peer dependency accepts', () => {
+    expect(supportedFirebaseRange.split('||').map(range => range.trim()).sort())
+      .toEqual([firebaseVersionRange, firebase13VersionRange].sort());
   });
 
   it('is a no-op when run a second time', () => {