diff --git a/docs/desktop-release.md b/docs/desktop-release.md
index 5706843..fed660a 100644
--- a/docs/desktop-release.md
+++ b/docs/desktop-release.md
@@ -139,6 +139,9 @@ Windows installer too: a tag push builds Linux only).
 
 - **Linux** (`runs-on: ubuntu-22.04`, a container): AppImage and .deb built with the path-free environment, then:
   - self-tests of the extracted AppImage and the unpacked .deb;
+  - both started for real under Xvfb (no xdg-utils or desktop-file-utils in the container, like a minimal system):
+    the job fails unless host.log says `sidecar started` (the window, WebKitGTK and the UI ran) with no error line in
+    host.log or webview.log;
   - the privacy scan and SHA256SUMS;
   - an artifact `storebound-desktop-linux`.