diff --git a/roles/reproducer/files/merge_yaml_override.py b/roles/reproducer/files/merge_yaml_override.py
index 8af81a437..5b8b05c58 100644
--- a/roles/reproducer/files/merge_yaml_override.py
+++ b/roles/reproducer/files/merge_yaml_override.py
@@ -56,11 +56,14 @@ def _str_representer(dumper, data):
 
 def deep_merge(base: object, override: object) -> object:
     """Take two parsed values;
-    return merge where both are dicts (recursive), else override wins."""
+    return merge where both are dicts (recursive), else override wins.
+    Empty dict in override replaces base value entirely."""
     if base is None:
         return override
     if override is None:
         return base
+    if isinstance(override, dict) and len(override) == 0:
+        return {}
     if isinstance(base, dict) and isinstance(override, dict):
         out = dict(base)
         for key, val in override.items():
diff --git a/tests/unit/modules/test_merge_yaml_override.py b/tests/unit/modules/test_merge_yaml_override.py
new file mode 100644
index 000000000..da56fea0b
--- /dev/null
+++ b/tests/unit/modules/test_merge_yaml_override.py
@@ -0,0 +1,193 @@
+# Copyright Red Hat, Inc.
+# All Rights Reserved.
+#
+# Licensed under the Apache License, Version 2.0 (the "License"); you may
+# not use this file except in compliance with the License. You may obtain
+# a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+# WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
+# License for the specific language governing permissions and limitations
+# under the License.
+
+"""Unit tests for merge_yaml_override.py deep_merge function."""
+
+import sys
+import unittest
+from pathlib import Path
+
+# Import the deep_merge function from the reproducer role
+sys.path.insert(0, str(Path(__file__).parents[3] / "roles" / "reproducer" / "files"))
+from merge_yaml_override import deep_merge
+
+
+class TestDeepMerge(unittest.TestCase):
+    """Test deep_merge function behavior."""
+
+    def test_empty_dict_overrides_non_empty_dict(self):
+        """Empty dict in override should replace base dict entirely."""
+        base = {"hook": {"type": "playbook", "source": "test.yml"}}
+        override = {"hook": {}}
+        result = deep_merge(base, override)
+        self.assertEqual(result, {"hook": {}})
+
+    def test_nested_empty_dict_override(self):
+        """Empty dict at nested level should override base value."""
+        base = {"outer": {"inner": {"key": "value"}}}
+        override = {"outer": {"inner": {}}}
+        result = deep_merge(base, override)
+        self.assertEqual(result, {"outer": {"inner": {}}})
+
+    def test_normal_dict_merge(self):
+        """Non-empty dicts should merge recursively, combining keys."""
+        base = {"a": {"x": 1, "y": 2}}
+        override = {"a": {"y": 3, "z": 4}}
+        result = deep_merge(base, override)
+        expected = {"a": {"x": 1, "y": 3, "z": 4}}
+        self.assertEqual(result, expected)
+
+    def test_scalar_override(self):
+        """Scalar values should override base completely."""
+        base = {"key": "old"}
+        override = {"key": "new"}
+        result = deep_merge(base, override)
+        self.assertEqual(result, {"key": "new"})
+
+    def test_list_override(self):
+        """Lists should override entirely, not merge elements."""
+        base = {"items": [1, 2, 3]}
+        override = {"items": [4, 5]}
+        result = deep_merge(base, override)
+        self.assertEqual(result, {"items": [4, 5]})
+
+    def test_none_base(self):
+        """When base is None, override should win."""
+        base = None
+        override = {"key": "value"}
+        result = deep_merge(base, override)
+        self.assertEqual(result, {"key": "value"})
+
+    def test_none_override(self):
+        """When override is None, base should win."""
+        base = {"key": "value"}
+        override = None
+        result = deep_merge(base, override)
+        self.assertEqual(result, {"key": "value"})
+
+    def test_both_none(self):
+        """When both are None, None should be returned."""
+        base = None
+        override = None
+        result = deep_merge(base, override)
+        self.assertIsNone(result)
+
+    def test_manila_hook_disable_scenario(self):
+        """Real-world scenario: disabling Manila hook in day2 scenarios.
+
+        This is the regression test for the PreMetal bug where empty dict
+        failed to override the hook definition from bootstrap phase.
+        """
+        # Bootstrap phase - hook defined in 05-hooks.yaml
+        base = {
+            "post_admin_setup_05_create_manila_resources": {
+                "type": "playbook",
+                "source": "manila_create_default_resources.yml",
+            }
+        }
+        # Testing phase - day2/scenario.yaml tries to disable with {}
+        override = {"post_admin_setup_05_create_manila_resources": {}}
+
+        result = deep_merge(base, override)
+
+        # Hook should be disabled (empty dict)
+        expected = {"post_admin_setup_05_create_manila_resources": {}}
+        self.assertEqual(result, expected)
+
+    def test_multiple_hooks_disable(self):
+        """Test disabling multiple hooks simultaneously."""
+        base = {
+            "post_admin_setup_05_create_manila_resources": {
+                "type": "playbook",
+                "source": "manila.yml",
+            },
+            "post_deploy_90_Watcher_Download_needed_tools": {
+                "inventory": "/path/to/inventory",
+                "source": "/path/to/download_tools.yaml",
+            },
+            "post_deploy_91_Watcher_Patch_Prometheus": {
+                "source": "/path/to/prometheus.yaml",
+                "type": "playbook",
+            },
+        }
+        override = {
+            "post_admin_setup_05_create_manila_resources": {},
+            "post_deploy_90_Watcher_Download_needed_tools": {},
+            "post_deploy_91_Watcher_Patch_Prometheus": {},
+        }
+
+        result = deep_merge(base, override)
+
+        expected = {
+            "post_admin_setup_05_create_manila_resources": {},
+            "post_deploy_90_Watcher_Download_needed_tools": {},
+            "post_deploy_91_Watcher_Patch_Prometheus": {},
+        }
+        self.assertEqual(result, expected)
+
+    def test_partial_hook_override_with_empty_dict(self):
+        """Test scenario where some hooks are disabled, others modified."""
+        base = {
+            "hook_a": {"type": "playbook", "source": "a.yml"},
+            "hook_b": {"type": "playbook", "source": "b.yml"},
+            "hook_c": {"type": "playbook", "source": "c.yml"},
+        }
+        override = {
+            "hook_a": {},  # Disable this one
+            "hook_b": {"type": "shell", "source": "b_modified.yml"},  # Modify
+            # hook_c not mentioned - should keep base
+        }
+
+        result = deep_merge(base, override)
+
+        expected = {
+            "hook_a": {},
+            "hook_b": {"type": "shell", "source": "b_modified.yml"},
+            "hook_c": {"type": "playbook", "source": "c.yml"},
+        }
+        self.assertEqual(result, expected)
+
+    def test_deeply_nested_empty_dict(self):
+        """Test empty dict override at multiple nesting levels."""
+        base = {"level1": {"level2": {"level3": {"level4": {"key": "value"}}}}}
+        override = {"level1": {"level2": {"level3": {}}}}  # Clear everything at level3
+
+        result = deep_merge(base, override)
+
+        expected = {"level1": {"level2": {"level3": {}}}}
+        self.assertEqual(result, expected)
+
+    def test_empty_dict_alongside_normal_merge(self):
+        """Test empty dict override mixed with normal dict merging."""
+        base = {
+            "section_a": {"x": 1, "y": 2},
+            "section_b": {"p": "old", "q": "old"},
+        }
+        override = {
+            "section_a": {},  # Clear section_a
+            "section_b": {"q": "new", "r": "new"},  # Merge into section_b
+        }
+
+        result = deep_merge(base, override)
+
+        expected = {
+            "section_a": {},
+            "section_b": {"p": "old", "q": "new", "r": "new"},
+        }
+        self.assertEqual(result, expected)
+
+
+if __name__ == "__main__":
+    unittest.main()