diff --git a/.github/workflows/build-windows.yml b/.github/workflows/build-windows.yml
index 31e5114..6aca800 100644
--- a/.github/workflows/build-windows.yml
+++ b/.github/workflows/build-windows.yml
@@ -76,3 +76,13 @@ jobs:
           name: flowy-llink-windows-signed
           path: js/out/make/**/*
           if-no-files-found: warn
+
+      # When Squirrel reports a generic "Failed to sign", the real error from
+      # @electron/windows-sign is written to this log by the fake signtool stub.
+      - name: Upload signing log (on failure)
+        if: failure()
+        uses: actions/upload-artifact@v4
+        with:
+          name: electron-windows-sign-log
+          path: js/node_modules/electron-winstaller/vendor/electron-windows-sign.log
+          if-no-files-found: ignore