diff --git a/.github/workflows/CI.yaml b/.github/workflows/CI.yaml
index 8799b38b..5546d196 100644
--- a/.github/workflows/CI.yaml
+++ b/.github/workflows/CI.yaml
@@ -144,6 +144,10 @@ jobs:
       contents: write
     steps:
       - uses: actions/checkout@v4
+      - uses: actions/setup-python@v5
+        with:
+          python-version-file: .python-version-default
+      - uses: hynek/setup-cached-uv@v2
 
       - name: Download coverage data
         uses: actions/download-artifact@v4
@@ -151,12 +155,31 @@ jobs:
           pattern: coverage-*
           merge-multiple: true
 
+      - name: Combine coverage & fail if it's <100%.
+        run: |
+          uv tool install 'coverage[toml]>7'
+
+          coverage combine
+          coverage html --skip-covered --skip-empty --show-missing
+
+          # Report and write to summary.
+          coverage report --skip-covered --skip-empty --show-missing --format=markdown >> $GITHUB_STEP_SUMMARY
+
+          ## Report again and fail if under 100%.
+          #coverage report --fail-under=100
+
+      - name: Upload HTML report if check failed.
+        uses: actions/upload-artifact@v4
+        with:
+          name: html-report
+          path: htmlcov
+        #if: ${{ failure() }}
+
       - name: Coverage comment
         id: coverage_comment
         uses: py-cov-action/python-coverage-comment-action@v3
         with:
           GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}
-          MERGE_COVERAGE_FILES: true
 
       - name: Store Pull Request comment to be posted
         uses: actions/upload-artifact@v4