diff --git a/src/config_manager.py b/src/config_manager.py
index 453e73b1..f544f35c 100644
--- a/src/config_manager.py
+++ b/src/config_manager.py
@@ -29,6 +29,7 @@ import os
 import logging
 from pathlib import Path
 from typing import Dict, Any, Optional, List
+from src.core_config_keys import CORE_CONFIG_KEYS, CORE_SECRETS_KEYS
 from src.exceptions import ConfigError
 from src.logging_config import get_logger
 from src.config_manager_atomic import (
@@ -756,12 +757,13 @@ class ConfigManager:
             
             valid_set = set(valid_plugin_ids)
             
-            # Find orphaned plugins in main config
-            main_plugins = set(main_config.keys())
+            # Find orphaned plugins in main config. Core sections (display,
+            # schedule, auto_update, ...) are not plugins and never orphans.
+            main_plugins = set(main_config.keys()) - CORE_CONFIG_KEYS
             orphaned_main = main_plugins - valid_set
             
             # Find orphaned plugins in secrets config
-            secrets_plugins = set(secrets_config.keys())
+            secrets_plugins = set(secrets_config.keys()) - CORE_CONFIG_KEYS - CORE_SECRETS_KEYS
             orphaned_secrets = secrets_plugins - valid_set
             
             all_orphaned = orphaned_main | orphaned_secrets
@@ -815,8 +817,8 @@ class ConfigManager:
                 if not isinstance(plugin_config, dict):
                     continue
                 
-                # Skip non-plugin config sections
-                if plugin_id in ['display', 'schedule', 'timezone', 'plugin_system']:
+                # Skip core config sections
+                if plugin_id in CORE_CONFIG_KEYS:
                     continue
                 
                 schema = plugin_schema_manager.load_schema(plugin_id, use_cache=True)
diff --git a/src/core_config_keys.py b/src/core_config_keys.py
index d68e785f..8d8a07fa 100644
--- a/src/core_config_keys.py
+++ b/src/core_config_keys.py
@@ -41,3 +41,13 @@ CORE_CONFIG_KEYS = frozenset({
     'vegas_excluded_plugins',
     'vegas_scroll_enabled',
 })
+
+#: Top-level keys of ``config_secrets.json`` that belong to the core rather than
+#: to a plugin: the GitHub token the Plugin Store reads, and the historical
+#: ``youtube`` section. Plugin secrets are namespaced by plugin id, so anything
+#: deciding whether a secrets section is a plugin's needs this as well as
+#: ``CORE_CONFIG_KEYS``.
+CORE_SECRETS_KEYS = frozenset({
+    'github',
+    'youtube',
+})
diff --git a/src/plugin_system/schema_manager.py b/src/plugin_system/schema_manager.py
index b56e6126..2be222ef 100644
--- a/src/plugin_system/schema_manager.py
+++ b/src/plugin_system/schema_manager.py
@@ -13,6 +13,8 @@ from typing import Any, Dict, List, Optional, Tuple
 import jsonschema
 from jsonschema import Draft7Validator, ValidationError
 
+from src.core_config_keys import CORE_CONFIG_KEYS
+
 
 def _renders_as_object(prop: Dict[str, Any]) -> bool:
     """``field_type == 'object'`` as ``plugin_config.html`` computes it.
@@ -698,10 +700,11 @@ class SchemaManager:
         """
         collisions = []
 
-        # Reserved top-level config keys that plugins should not use as IDs
-        reserved_keys = {
-            'display', 'schedule', 'timezone', 'plugin_system',
-            'display_modes', 'system', 'hardware', 'debug',
+        # Reserved top-level config keys that plugins should not use as IDs:
+        # every core section (src/core_config_keys.py), plus a few names that
+        # read as core even though no current section uses them.
+        reserved_keys = set(CORE_CONFIG_KEYS) | {
+            'display_modes', 'hardware', 'debug',
             'log_level', 'emulator', 'web_interface'
         }
 
diff --git a/src/startup_validator.py b/src/startup_validator.py
index 7bf15a11..954c751f 100644
--- a/src/startup_validator.py
+++ b/src/startup_validator.py
@@ -8,6 +8,7 @@ Fails fast with clear error messages to prevent runtime issues.
 import os
 from typing import Any, List, Optional, Tuple
 from pathlib import Path
+from src.core_config_keys import CORE_CONFIG_KEYS
 from src.exceptions import ConfigError, PluginError, CacheError
 from src.logging_config import get_logger
 
@@ -275,8 +276,9 @@ class StartupValidator:
             
             # Check for enabled plugins that don't exist
             for plugin_id, plugin_config in config.items():
-                # Skip non-plugin config sections
-                if plugin_id in ['display', 'schedule', 'timezone', 'plugin_system']:
+                # Skip core sections: auto_update and dim_schedule have an
+                # 'enabled' key too, and are not plugins that went missing.
+                if plugin_id in CORE_CONFIG_KEYS:
                     continue
                 
                 if not isinstance(plugin_config, dict):
diff --git a/test/test_core_config_key_adopters.py b/test/test_core_config_key_adopters.py
new file mode 100644
index 00000000..c93e3b0d
--- /dev/null
+++ b/test/test_core_config_key_adopters.py
@@ -0,0 +1,108 @@
+"""Every "is this top-level key a plugin?" decision uses src/core_config_keys.py.
+
+#589 moved plugin-state reconciliation onto the shared list, but three private
+copies stayed behind and did not know about auto_update, dim_schedule, sync,
+location, target_fps, ...:
+
+- StartupValidator warned "Plugin 'auto_update' is enabled but not found in
+  plugins directory" on every display start with auto-update or a dim
+  schedule switched on;
+- SchemaManager.detect_config_key_collisions let a plugin id collide with
+  those sections silently;
+- ConfigManager.cleanup_orphaned_plugin_configs deleted display, schedule,
+  auto_update, ... as orphans, and validate_all_plugin_configs validated core
+  sections as plugins.
+"""
+
+import json
+import re
+from pathlib import Path
+from unittest.mock import MagicMock
+
+import pytest
+
+from src.config_manager import ConfigManager
+from src.core_config_keys import CORE_CONFIG_KEYS, CORE_SECRETS_KEYS
+from src.plugin_system.schema_manager import SchemaManager
+from src.startup_validator import StartupValidator
+
+REPO = Path(__file__).resolve().parent.parent
+
+
+class TestStartupValidator:
+    def test_enabled_core_sections_are_not_missing_plugins(self):
+        config = {
+            'display': {'hardware': {}},
+            'auto_update': {'enabled': True},
+            'dim_schedule': {'enabled': True},
+            'schedule': {'enabled': True},
+            'gone-plugin': {'enabled': True},
+        }
+        cm = MagicMock()
+        cm.get_config.return_value = config
+        pm = MagicMock()
+        pm.discover_plugins.return_value = []
+        validator = StartupValidator(cm, plugin_manager=pm, cache_manager=MagicMock())
+        validator.warnings = []
+        validator.errors = []
+        validator._validate_plugins()
+        missing = [w for w in validator.warnings if 'not found in plugins directory' in w]
+        assert missing == ["Plugin 'gone-plugin' is enabled but not found in plugins directory"]
+
+
+class TestReservedPluginIds:
+    @pytest.mark.parametrize('key', sorted(CORE_CONFIG_KEYS))
+    def test_every_core_key_is_reserved(self, key):
+        collisions = SchemaManager().detect_config_key_collisions([key])
+        assert [c['type'] for c in collisions] == ['reserved_key_collision']
+
+    def test_an_ordinary_plugin_id_is_not(self):
+        assert SchemaManager().detect_config_key_collisions(['clock-simple']) == []
+
+
+class TestConfigManagerHelpers:
+    @pytest.fixture
+    def manager(self, tmp_path):
+        config = {key: {'enabled': True} for key in ('display', 'schedule', 'auto_update',
+                                                      'dim_schedule', 'sync', 'location')}
+        config.update({'timezone': 'UTC', 'installed': {'enabled': True},
+                       'orphan': {'enabled': True}})
+        secrets = {'github': {'token': 't'}, 'youtube': {'api_key': 'k'},
+                   'installed': {'api_key': 'a'}, 'orphan': {'api_key': 'o'}}
+        (tmp_path / 'config.json').write_text(json.dumps(config))
+        (tmp_path / 'secrets.json').write_text(json.dumps(secrets))
+        manager = ConfigManager(config_path=str(tmp_path / 'config.json'),
+                                secrets_path=str(tmp_path / 'secrets.json'))
+        manager.template_path = str(tmp_path / 'no-template.json')
+        return manager
+
+    def test_cleanup_removes_only_real_orphans(self, manager, tmp_path):
+        removed = manager.cleanup_orphaned_plugin_configs(['installed'])
+        assert removed == ['orphan']
+        config = json.loads((tmp_path / 'config.json').read_text())
+        assert {'display', 'schedule', 'auto_update', 'dim_schedule', 'sync',
+                'location', 'timezone', 'installed'} == set(config)
+        secrets = json.loads((tmp_path / 'secrets.json').read_text())
+        assert set(secrets) == {'github', 'youtube', 'installed'}
+
+    def test_validate_all_skips_core_sections(self, manager):
+        schema_manager = MagicMock()
+        schema_manager.load_schema.return_value = None
+        results = manager.validate_all_plugin_configs(schema_manager)
+        assert set(results) == {'installed', 'orphan'}
+
+
+def test_core_secrets_keys_are_not_core_config_keys():
+    assert not (CORE_SECRETS_KEYS & CORE_CONFIG_KEYS)
+
+
+@pytest.mark.parametrize('relpath', [
+    'src/startup_validator.py',
+    'src/config_manager.py',
+    'src/plugin_system/schema_manager.py',
+])
+def test_no_private_copy_of_the_list_remains(relpath):
+    """The old copies all started with this literal; a new copy likely would too."""
+    source = (REPO / relpath).read_text(encoding='utf-8')
+    assert not re.search(r"""\[\s*['"]display['"]\s*,\s*['"]schedule['"]""", source), \
+        f'{relpath} has a private core-key list again; use src/core_config_keys.py'