diff --git a/sonar-project.properties b/sonar-project.properties
index 9d47eedb83..0d9709e930 100644
--- a/sonar-project.properties
+++ b/sonar-project.properties
@@ -39,12 +39,52 @@ sonar.exclusions=\
   addons/**/webpack.config.js,\
   i18n/**/*.json
 
-# Exclude test/generated files from coverage metrics
+# Exclude files from coverage metrics that cannot be practically covered by Karma unit tests.
+#
+# Categories:
+#  - Test files themselves
+#  - HTML files (**.html) — while many contain inline <script> with executable Polymer logic,
+#    Istanbul does not instrument <script> blocks inside HTML via the Karma ESM pipeline;
+#    only standalone .js modules are instrumented for coverage
+#  - CSS / JSON / YAML — no executable code
+#  - Root-level bootstrap files (index.js, legacy.js, public-path.js, sw.js) — app entry points
+#    and service worker that require a full browser bootstrap context
+#  - elements/routing.js — runs Page.js route setup at import time, requires Nuxeo.UI app shell
+#  - elements/elements.js — side-effect import barrel (no exportable logic, just registers elements)
+#  - i18n/i18n.js — i18n bootstrap loader
+#  - themes/*.html — covered by **/*.html above; themes/base.js and themes/loader.js have
+#    unit tests and remain in coverage scope
+#  - Addon index.js barrel files — side-effect registrations / re-exports
+#  - nuxeo-spreadsheet/app/ — only files deeply coupled to jQuery/Handsontable/Select2 at import time:
+#    app.js (imports vendor), lib/ (patches Handsontable prototype), ui/spreadsheet.js (jQuery container),
+#    ui/editors/ (extend Select2Editor). Testable modules NOT excluded: utils.js, nuxeo/rest/*,
+#    nuxeo/rpc/*, nuxeo/widget.js, ui/i18n.js, ui/column.js, ui/widgets.js, ui/log.js
+#  - nuxeo-spreadsheet build config (webpack.config.js, eslint-rules.mjs)
+#  - nuxeo-platform-3d/ — THREE.js loaders/controls break Karma ESM; elements depend on them
+#  - .github/ — CI workflow YAML/JS, not application code
 sonar.coverage.exclusions=\
   **/*.test.js,\
+  **/*.html,\
+  **/*.css,\
   **/*.yaml,\
   **/*.yml,\
-  i18n/**/*.json
+  **/*.json,\
+  index.js,\
+  legacy.js,\
+  public-path.js,\
+  sw.js,\
+  elements/routing.js,\
+  elements/elements.js,\
+  i18n/i18n.js,\
+  addons/*/index.js,\
+  addons/nuxeo-spreadsheet/app/app.js,\
+  addons/nuxeo-spreadsheet/app/lib/**,\
+  addons/nuxeo-spreadsheet/app/ui/spreadsheet.js,\
+  addons/nuxeo-spreadsheet/app/ui/editors/**,\
+  addons/nuxeo-spreadsheet/webpack.config.js,\
+  addons/nuxeo-spreadsheet/eslint-rules.mjs,\
+  addons/nuxeo-platform-3d/**,\
+  .github/**
 
 # Treat test/**/*.test.js and addon test files as test code, not source
 sonar.test.inclusions=test/**/*.test.js,addons/*/test/**/*.test.js
@@ -60,4 +100,4 @@ sonar.sourceEncoding=UTF-8
 # TODO: Remove once sub-packages have package-lock.json and npm ci can be used safely.
 sonar.issue.ignore.multicriteria=e1
 sonar.issue.ignore.multicriteria.e1.ruleKey=*
-sonar.issue.ignore.multicriteria.e1.resourceKey=.github/workflows/**
\ No newline at end of file
+sonar.issue.ignore.multicriteria.e1.resourceKey=.github/workflows/**