diff --git a/.jules/sentinel.md b/.jules/sentinel.md
new file mode 100644
index 0000000..2804c91
--- /dev/null
+++ b/.jules/sentinel.md
@@ -0,0 +1 @@
+# Sentinel Journal - Security Learnings
diff --git a/auth/utils.py b/auth/utils.py
index 4bded89..d993e23 100644
--- a/auth/utils.py
+++ b/auth/utils.py
@@ -128,8 +128,9 @@ def decorated_function(*args, **kwargs):
             g.user_id = user_id
             g.user = user_data
             return f(*args, **kwargs)
-        except Exception as e:
-            return jsonify({'error': 'Unauthorized', 'details': str(e)}), 401
+        except Exception:
+            # Secure error handling: do not expose exception details to caller
+            return jsonify({'error': 'Unauthorized'}), 401
     return decorated_function
 
 
diff --git a/src/handoff/__init__.py b/src/handoff/__init__.py
new file mode 100644
index 0000000..e69de29
diff --git a/tests/test_auth.py b/tests/test_auth.py
new file mode 100644
index 0000000..11aa16d
--- /dev/null
+++ b/tests/test_auth.py
@@ -0,0 +1,39 @@
+import sys
+from unittest.mock import MagicMock, patch
+
+# Mock cache_db module dependencies required by auth.utils
+mock_redis = MagicMock()
+mock_models = MagicMock()
+sys.modules['cache_db'] = MagicMock()
+sys.modules['cache_db.redis_client'] = mock_redis
+sys.modules['cache_db.models'] = mock_models
+
+from flask import Flask
+from auth.utils import login_required, PasswordUtils, JWTUtils
+
+
+def test_login_required_unauthorized_error_no_details_leak():
+    """Verify login_required does not leak internal exception details in response."""
+    app = Flask(__name__)
+
+    @app.route('/protected')
+    @login_required
+    def protected_route():
+        return {'status': 'ok'}
+
+    with app.test_request_context('/protected'):
+        with patch('auth.utils.verify_jwt_in_request', side_effect=Exception('Secret internal stack trace detail')):
+            response, status_code = protected_route()
+
+            assert status_code == 401
+            json_data = response.get_json()
+            assert json_data == {'error': 'Unauthorized'}
+            assert 'details' not in json_data
+
+
+def test_password_utils_hash_and_verify():
+    """Verify password hashing and verification functionality."""
+    pwd = "securepassword123"
+    hashed = PasswordUtils.hash_password(pwd)
+    assert PasswordUtils.verify_password(pwd, hashed) is True
+    assert PasswordUtils.verify_password("wrongpassword", hashed) is False