Remove mergedeep dependency

docs/about/release-notes.md

@@ -23,6 +23,12 @@ The current members of the MkDocs-NG team.
 
 * [@shenxianpeng](https://github.com/shenxianpeng)
 
+## Version 1.7.1 (Unreleased)
+
+### Maintenance
+
+* Remove the unmaintained `mergedeep` dependency by replacing it with an internal deep-merge helper for inherited YAML configuration. #29
+
 ## Version 1.7.0 (2026-04-24)
 
 MkDocs NG 1.7.0 is a small but important release. The biggest change is that

mkdocs/tests/utils/utils_tests.py

@@ -19,6 +19,10 @@
 baz:
     sub1: replaced
     sub3: new
+replace_list:
+    - child
+replace_scalar:
+    nested: value
 deep1:
     deep2-1:
         deep3-1: replaced
@@ -28,6 +32,9 @@
 baz:
     sub1: 1
     sub2: 2
+replace_list:
+    - parent
+replace_scalar: value
 deep1:
     deep2-1:
         deep3-1: foo
@@ -291,6 +298,8 @@ def test_yaml_inheritance(self, tdir):
                 "sub2": 2,
                 "sub3": "new",
             },
+            "replace_list": ["child"],
+            "replace_scalar": {"nested": "value"},
             "deep1": {
                 "deep2-1": {
                     "deep3-1": "replaced",

mkdocs/utils/yaml.py

@@ -4,9 +4,9 @@
 import logging
 import os
 import os.path
+from collections.abc import MutableMapping
 from typing import IO, TYPE_CHECKING, Any
 
-import mergedeep  # type: ignore
 import yaml
 import yaml.constructor
 import yaml_env_tag  # type: ignore
@@ -19,6 +19,20 @@
 log = logging.getLogger(__name__)
 
 
+def _deep_merge(
+    parent: MutableMapping[Any, Any], child: MutableMapping[Any, Any]
+) -> MutableMapping[Any, Any]:
+    for key, child_value in child.items():
+        parent_value = parent.get(key)
+        if isinstance(parent_value, MutableMapping) and isinstance(
+            child_value, MutableMapping
+        ):
+            _deep_merge(parent_value, child_value)
+        else:
+            parent[key] = child_value
+    return parent
+
+
 def _construct_dir_placeholder(
     config: MkDocsConfig, loader: yaml.BaseLoader, node: yaml.ScalarNode
 ) -> _DirPlaceholder:
@@ -152,5 +166,5 @@ def yaml_load(
         log.debug(f"Loading inherited configuration file: {abspath}")
         with open(abspath, "rb") as fd:
             parent = yaml_load(fd, loader)
-        result = mergedeep.merge(parent, result)
+        result = _deep_merge(parent, result)
     return result

pyproject.toml

@@ -46,7 +46,6 @@ dependencies = [
     "pyyaml_env_tag >=0.1",
     "importlib-metadata >=4.4; python_version < '3.10'",
     "packaging >=20.5",
-    "mergedeep >=1.3.4",
     "pathspec >=0.11.1",
     "mkdocs-get-deps >=0.2.0",
     "colorama >=0.4; platform_system == 'Windows'",
@@ -66,7 +65,6 @@ min-versions = [
     "pyyaml_env_tag ==1.1",
     "importlib-metadata ==4.4; python_version < '3.10'",
     "packaging ==26.1",
-    "mergedeep ==1.3.4",
     "pathspec ==1.0.4",
     "mkdocs-get-deps ==0.2.2",
     "colorama ==0.4.6; platform_system == 'Windows'",