diff --git "a/claudetool/onstart/testdata/\303\234bung.html" "b/claudetool/onstart/testdata/\303\234bung.html"
new file mode 100644
index 0000000..afc66ab
--- /dev/null
+++ "b/claudetool/onstart/testdata/\303\234bung.html"
@@ -0,0 +1,10 @@
+<!DOCTYPE html>
+<html>
+<head>
+    <title>German Umlaut Test</title>
+</head>
+<body>
+    <h1>Übung HTML File</h1>
+    <p>This HTML file has German umlaut characters in the filename.</p>
+</body>
+</html>