diff --git a/drift_detector/src/drift_detector/cli.py b/drift_detector/src/drift_detector/cli.py
new file mode 100644
index 0000000..9ed25ed
--- /dev/null
+++ b/drift_detector/src/drift_detector/cli.py
@@ -0,0 +1,51 @@
+import argparse
+import json
+import sys
+from pathlib import Path
+
+from drift_detector import core
+
+def _validate_input_file(path_str: str) -> Path:
+    path = Path(path_str)
+    if not path.exists() or not path.is_file():
+        raise FileNotFoundError(f'Eingabedatei nicht gefunden: {path}')
+    return path
+
+def _validate_output_path(path_str: str | None) -> Path | None:
+    if not path_str:
+        return None
+    path = Path(path_str)
+    path.parent.mkdir(parents=True, exist_ok=True)
+    return path
+
+def main() -> None:
+    """CLI-Einstiegspunkt für die Drift-Erkennung."""
+    parser = argparse.ArgumentParser(description='Detect structural drift in key logs.')
+    parser.add_argument('--input', required=True, help='Pfad zur Eingabedatei im JSONL-Format mit Mess-Logs')
+    parser.add_argument('--output', required=False, help='Optionale Ausgabedatei für den Driftbericht')
+    args = parser.parse_args()
+
+    try:
+        input_path = _validate_input_file(args.input)
+        output_path = _validate_output_path(args.output)
+
+        drift_detected = core.detect_drift(str(input_path))
+
+        result = {
+            'input_file': str(input_path),
+            'drift_detected': drift_detected
+        }
+
+        if output_path:
+            with output_path.open('w', encoding='utf-8') as f:
+                json.dump(result, f, ensure_ascii=False, indent=2)
+        else:
+            json.dump(result, sys.stdout, ensure_ascii=False, indent=2)
+            sys.stdout.write('\n')
+
+    except Exception as e:
+        sys.stderr.write(f'Fehler: {e}\n')
+        sys.exit(1)
+
+if __name__ == '__main__':
+    main()
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