diff --git a/.github/workflows/test.yml b/.github/workflows/test.yml
index f52ae128e..666b0d126 100644
--- a/.github/workflows/test.yml
+++ b/.github/workflows/test.yml
@@ -163,6 +163,11 @@ jobs:
     name: Publish (NPM)
     needs: ['build', 'test', 'browser']
     if: ${{ github.ref == 'refs/heads/main' || github.event_name == 'release' }}
+    # One canary publish at a time, so the check below reads the canary the previous one published.
+    concurrency:
+      group: ${{ github.event_name == 'release' && github.run_id || 'canary-publish' }}
+      cancel-in-progress: false
+      queue: max
     steps:
       - name: Setup node
         uses: actions/setup-node@48b55a011bda9f5d6aeb4c2d9c7362e8dae4041e # v6.4.0
@@ -175,7 +180,37 @@ jobs:
         with:
           name: angularfire-${{ github.run_id }}
           path: dist
+      - name: Skip a canary that is not newer than npm's
+        id: canary_check
+        run: |
+          VERSION=$(node -p "require('./dist/packages-dist/package.json').version")
+          if [[ $VERSION == *-canary.* ]]; then
+            # The dist-tags endpoint is not CDN-cached, unlike the package data `npm view` reads.
+            DIST_TAGS=$(curl -fsS --retry 3 --max-time 30 https://registry.npmjs.org/-/package/@angular/fire/dist-tags)
+            NPM_CANARY=$(node -p "JSON.parse(process.argv[1]).canary" "$DIST_TAGS")
+            # Order by position on main, not by version, which can be higher for an older commit.
+            git clone --quiet --bare --filter=tree:0 "$GITHUB_SERVER_URL/$GITHUB_REPOSITORY" history.git
+            HOW_TO_FIX="Every canary publish fails until the canary dist-tag points at a build of a commit on main. Publish rights are required to fix it with: npm dist-tag add @angular/fire@<version> canary"
+            if ! NPM_CANARY_COMMIT=$(git -C history.git rev-parse --verify --quiet "${NPM_CANARY##*[.-]}^{commit}"); then
+              echo "::error::Could not match the canary on npm, $NPM_CANARY, to a single commit in this repository. $HOW_TO_FIX"
+              exit 1
+            fi
+            # `npm publish` always moves a dist-tag, so a canary that is not newer must not publish at all.
+            if [[ $NPM_CANARY_COMMIT == "$GITHUB_SHA" ]]; then
+              if [[ $VERSION == "$NPM_CANARY" ]]; then
+                echo "::notice::Not publishing $VERSION, because it is already the canary on npm."
+                echo "skip=true" >> "$GITHUB_OUTPUT"
+              fi
+            elif git -C history.git merge-base --is-ancestor "$GITHUB_SHA" "$NPM_CANARY_COMMIT"; then
+              echo "::warning::Not publishing $VERSION, because the canary on npm, $NPM_CANARY, is from a later commit on main."
+              echo "skip=true" >> "$GITHUB_OUTPUT"
+            elif ! git -C history.git merge-base --is-ancestor "$NPM_CANARY_COMMIT" "$GITHUB_SHA"; then
+              echo "::error::Not publishing $VERSION, because its commit and the commit of the canary on npm, $NPM_CANARY, are not on the same line of history. One of them is not on main. $HOW_TO_FIX"
+              exit 1
+            fi
+          fi
       - name: Publish
+        if: steps.canary_check.outputs.skip != 'true'
         run: |
           cd ./dist/packages-dist
           chmod +x publish.sh