diff --git a/lib/core/theme/theme_registry_service.dart b/lib/core/theme/theme_registry_service.dart
new file mode 100644
index 00000000..2330c14b
--- /dev/null
+++ b/lib/core/theme/theme_registry_service.dart
@@ -0,0 +1,188 @@
+import 'dart:convert';
+import 'dart:io';
+
+import 'package:flutter/foundation.dart';
+import 'package:path/path.dart' as p;
+
+import 'parser/jsonc_preprocessor.dart';
+import 'parser/querya_theme_manifest.dart';
+import 'theme_definition.dart';
+import 'theme_paths.dart';
+
+/// Scans theme directories and exposes lightweight [ThemeDefinition] metadata.
+class ThemeRegistryService {
+  ThemeRegistryService({
+    Future<Directory> Function()? userThemesDirectory,
+    Future<Directory> Function()? importedThemesDirectory,
+  })  : _userThemesDirectory =
+            userThemesDirectory ?? ThemePaths.userThemesDirectory,
+        _importedThemesDirectory =
+            importedThemesDirectory ?? ThemePaths.importedThemesDirectory;
+
+  final Future<Directory> Function() _userThemesDirectory;
+  final Future<Directory> Function() _importedThemesDirectory;
+
+  Future<List<ThemeDefinition>> loadThemeDefinitions() async {
+    final definitions = <ThemeDefinition>[];
+
+    await _scanDirectory(
+      await _userThemesDirectory(),
+      ThemeSource.filesystem,
+      definitions,
+    );
+    await _scanDirectory(
+      await _importedThemesDirectory(),
+      ThemeSource.imported,
+      definitions,
+    );
+
+    definitions.sort(
+      (a, b) => a.name.toLowerCase().compareTo(b.name.toLowerCase()),
+    );
+    return List.unmodifiable(definitions);
+  }
+
+  Future<void> _scanDirectory(
+    Directory directory,
+    ThemeSource source,
+    List<ThemeDefinition> out,
+  ) async {
+    if (!await directory.exists()) return;
+
+    await for (final entity in directory.list(followLinks: false)) {
+      if (entity is Directory) {
+        if (p.basename(entity.path) == 'imported') continue;
+        continue;
+      }
+      if (entity is! File) continue;
+
+      final ext = p.extension(entity.path).toLowerCase();
+      if (ext != '.json' && ext != '.jsonc') continue;
+
+      final definition = await _definitionFromFile(entity, source);
+      if (definition != null) {
+        out.add(definition);
+      }
+    }
+  }
+
+  Future<ThemeDefinition?> _definitionFromFile(
+    File file,
+    ThemeSource source,
+  ) async {
+    try {
+      final stat = await file.stat();
+      final raw = await file.readAsString();
+      final hash = _contentHash(raw);
+      final json = _decodeRoot(raw);
+      if (json == null) {
+        _logScanError(file.path, 'Invalid JSON');
+        return null;
+      }
+
+      final schema = json['schema']?.toString();
+      if (schema == queryaThemeSchemaV1) {
+        return _customDefinition(
+          json: json,
+          file: file,
+          source: source,
+          lastModified: stat.modified,
+          contentHash: hash,
+        );
+      }
+
+      return _vscodeDefinition(
+        json: json,
+        file: file,
+        source: source,
+        lastModified: stat.modified,
+        contentHash: hash,
+      );
+    } on Object catch (e) {
+      _logScanError(file.path, e);
+      return null;
+    }
+  }
+
+  ThemeDefinition? _customDefinition({
+    required Map<String, dynamic> json,
+    required File file,
+    required ThemeSource source,
+    required DateTime lastModified,
+    required String contentHash,
+  }) {
+    final id = json['id']?.toString().trim();
+    final name = json['name']?.toString().trim();
+    final type = json['type']?.toString().trim().toLowerCase();
+
+    if (id == null || id.isEmpty || name == null || name.isEmpty) {
+      _logScanError(file.path, 'Missing required custom theme fields');
+      return null;
+    }
+    if (type != 'dark' && type != 'light') {
+      _logScanError(file.path, 'Invalid custom theme type "$type"');
+      return null;
+    }
+
+    return ThemeDefinition(
+      id: id,
+      name: name,
+      source: source,
+      format: ThemeFormat.queryaCustom,
+      isDark: type == 'dark',
+      path: file.path,
+      lastModified: lastModified,
+      contentHash: contentHash,
+    );
+  }
+
+  ThemeDefinition? _vscodeDefinition({
+    required Map<String, dynamic> json,
+    required File file,
+    required ThemeSource source,
+    required DateTime lastModified,
+    required String contentHash,
+  }) {
+    final fileId = p.basenameWithoutExtension(file.path);
+    final rawName = json['name']?.toString().trim();
+    final name = rawName != null && rawName.isNotEmpty ? rawName : fileId;
+    final type = json['type']?.toString().trim().toLowerCase();
+
+    return ThemeDefinition(
+      id: fileId,
+      name: name,
+      source: source,
+      format: ThemeFormat.vscode,
+      isDark: type == 'dark',
+      path: file.path,
+      lastModified: lastModified,
+      contentHash: contentHash,
+    );
+  }
+
+  Map<String, dynamic>? _decodeRoot(String raw) {
+    try {
+      final decoded = jsonDecode(stripJsonc(raw));
+      if (decoded is Map<String, dynamic>) return decoded;
+    } on FormatException {
+      return null;
+    }
+    return null;
+  }
+
+  static String _contentHash(String content) {
+    final bytes = utf8.encode(content);
+    var hash = 0x811c9dc5;
+    for (final b in bytes) {
+      hash ^= b;
+      hash = (hash * 0x01000193) & 0xffffffff;
+    }
+    return hash.toRadixString(16).padLeft(8, '0');
+  }
+
+  void _logScanError(String path, Object error) {
+    if (kDebugMode) {
+      debugPrint('ThemeRegistryService: skipped $path ($error)');
+    }
+  }
+}
diff --git a/test/core/theme/theme_registry_service_test.dart b/test/core/theme/theme_registry_service_test.dart
new file mode 100644
index 00000000..b94ffdcf
--- /dev/null
+++ b/test/core/theme/theme_registry_service_test.dart
@@ -0,0 +1,158 @@
+import 'dart:io';
+
+import 'package:flutter_test/flutter_test.dart';
+import 'package:path/path.dart' as p;
+import 'package:path_provider_platform_interface/path_provider_platform_interface.dart';
+import 'package:querya_desktop/core/theme/theme_definition.dart';
+import 'package:querya_desktop/core/theme/theme_registry_service.dart';
+
+class _FakePathProvider extends PathProviderPlatform {
+  _FakePathProvider(this._root);
+  final String _root;
+
+  @override
+  Future<String?> getApplicationSupportPath() async => _root;
+}
+
+Future<void> _copyFixture(String fixtureName, File destination) async {
+  final source = File(p.join('test/fixtures/themes', fixtureName));
+  await destination.writeAsString(await source.readAsString());
+}
+
+void main() {
+  TestWidgetsFlutterBinding.ensureInitialized();
+
+  late Directory tempDir;
+  late Directory themesDir;
+  late Directory importedDir;
+  late ThemeRegistryService registry;
+
+  setUpAll(() async {
+    tempDir = await Directory.systemTemp.createTemp('querya_theme_registry_test_');
+    PathProviderPlatform.instance = _FakePathProvider(tempDir.path);
+  });
+
+  setUp(() async {
+    themesDir = Directory(p.join(tempDir.path, 'themes'));
+    importedDir = Directory(p.join(themesDir.path, 'imported'));
+    await importedDir.create(recursive: true);
+
+    registry = ThemeRegistryService(
+      userThemesDirectory: () async => themesDir,
+      importedThemesDirectory: () async => importedDir,
+    );
+  });
+
+  tearDown(() async {
+    if (await themesDir.exists()) {
+      await themesDir.delete(recursive: true);
+    }
+  });
+
+  tearDownAll(() async {
+    if (await tempDir.exists()) {
+      await tempDir.delete(recursive: true);
+    }
+  });
+
+  group('ThemeRegistryService.loadThemeDefinitions', () {
+    test('includes valid custom and VS Code themes, skips broken file', () async {
+      await _copyFixture(
+        'querya_custom_dark.json',
+        File(p.join(themesDir.path, 'querya_custom_dark.json')),
+      );
+      await _copyFixture(
+        'dark_subset.json',
+        File(p.join(themesDir.path, 'dark_subset.json')),
+      );
+      await _copyFixture(
+        'querya_custom_invalid_missing_id.json',
+        File(p.join(themesDir.path, 'broken.json')),
+      );
+
+      final definitions = await registry.loadThemeDefinitions();
+
+      expect(definitions, hasLength(2));
+      expect(
+        definitions.map((d) => d.format).toSet(),
+        equals({ThemeFormat.queryaCustom, ThemeFormat.vscode}),
+      );
+      expect(
+        definitions.singleWhere((d) => d.format == ThemeFormat.queryaCustom).id,
+        'fixture-custom-dark',
+      );
+      expect(
+        definitions.singleWhere((d) => d.format == ThemeFormat.vscode).name,
+        'Fixture Dark Subset',
+      );
+    });
+
+    test('sorts definitions by name case-insensitively', () async {
+      await File(p.join(themesDir.path, 'z-theme.json')).writeAsString('''
+{
+  "schema": "querya.theme.v1",
+  "id": "z-theme",
+  "name": "Zebra Theme",
+  "type": "dark",
+  "shadcn_colors": {},
+  "editor_colors": {}
+}
+''');
+      await File(p.join(themesDir.path, 'a-theme.json')).writeAsString('''
+{
+  "schema": "querya.theme.v1",
+  "id": "a-theme",
+  "name": "alpha theme",
+  "type": "light",
+  "shadcn_colors": {},
+  "editor_colors": {}
+}
+''');
+
+      final definitions = await registry.loadThemeDefinitions();
+
+      expect(definitions.map((d) => d.name), ['alpha theme', 'Zebra Theme']);
+    });
+
+    test('content hash changes when file content changes', () async {
+      final themeFile = File(p.join(themesDir.path, 'hash-theme.json'));
+      await _copyFixture('querya_custom_minimal.json', themeFile);
+
+      final before = await registry.loadThemeDefinitions();
+      expect(before, hasLength(1));
+      final originalHash = before.single.contentHash;
+
+      final raw = await themeFile.readAsString();
+      await themeFile.writeAsString(raw.replaceFirst('#FF00AA', '#00FFAA'));
+
+      final after = await registry.loadThemeDefinitions();
+      expect(after, hasLength(1));
+      expect(after.single.contentHash, isNot(originalHash));
+    });
+
+    test('scans imported directory with imported source', () async {
+      await _copyFixture(
+        'querya_custom_light.json',
+        File(p.join(importedDir.path, 'querya_custom_light.json')),
+      );
+
+      final definitions = await registry.loadThemeDefinitions();
+
+      expect(definitions, hasLength(1));
+      expect(definitions.single.source, ThemeSource.imported);
+      expect(definitions.single.id, 'fixture-custom-light');
+    });
+
+    test('ignores non-json theme extensions', () async {
+      await File(p.join(themesDir.path, 'notes.txt')).writeAsString('not a theme');
+      await _copyFixture(
+        'querya_custom_dark.json',
+        File(p.join(themesDir.path, 'querya_custom_dark.json')),
+      );
+
+      final definitions = await registry.loadThemeDefinitions();
+
+      expect(definitions, hasLength(1));
+    });
+  });
+}