diff --git a/apps/student_app/lib/data/repositories/curriculum_repository.dart b/apps/student_app/lib/data/repositories/curriculum_repository.dart
index 730673e..211cc5d 100644
--- a/apps/student_app/lib/data/repositories/curriculum_repository.dart
+++ b/apps/student_app/lib/data/repositories/curriculum_repository.dart
@@ -127,10 +127,10 @@ class CurriculumRepository {
   }
 
   /// Fetch lesson playback details (streams, checkpoints, and versions) from Live API
-  Future<LessonPlaybackData> getLessonPlayback(String lessonId, {String? subjectId, String? unitId}) async {
-    AppLogger.log('Fetching live playback data for lesson $lessonId from /api/lessons/$lessonId/playback...', tag: 'CURRICULUM_REPO');
+  Future<LessonPlaybackData> getLessonPlayback(String curriculumKey, {String? subjectId, String? unitId}) async {
+    AppLogger.log('Fetching live playback data for curriculum key $curriculumKey...', tag: 'CURRICULUM_REPO');
     
-    final res = await _api.get('/api/lessons/$lessonId/playback');
+    final res = await _api.get('/api/lessons/playback', queryParams: {'curriculum_key': curriculumKey});
     if (res is Map && res['data'] != null) {
       return LessonPlaybackData.fromJson(Map<String, dynamic>.from(res['data']));
     }
diff --git a/apps/student_app/lib/logic/cubits/video_playback_cubit.dart b/apps/student_app/lib/logic/cubits/video_playback_cubit.dart
index 4f29d71..f86e6c4 100644
--- a/apps/student_app/lib/logic/cubits/video_playback_cubit.dart
+++ b/apps/student_app/lib/logic/cubits/video_playback_cubit.dart
@@ -78,7 +78,7 @@ class VideoPlaybackCubit extends Cubit<VideoPlaybackState> {
     AppLogger.log('Loading Socratic playback for lesson: ${lesson.title}', tag: 'VIDEO_CUBIT');
     emit(VideoPlaybackLoading());
     try {
-      final playback = await _repo.getLessonPlayback(lesson.id, subjectId: subject?.id);
+      final playback = await _repo.getLessonPlayback(lesson.markdownFilePath ?? lesson.id, subjectId: subject?.id);
       emit(VideoPlaybackReady(
         playbackData: playback,
         lessonItem: lesson,
diff --git a/backend/app/Controllers/CurriculumController.php b/backend/app/Controllers/CurriculumController.php
index d48c67d..04fb1aa 100644
--- a/backend/app/Controllers/CurriculumController.php
+++ b/backend/app/Controllers/CurriculumController.php
@@ -267,8 +267,8 @@ class CurriculumController
             $manifestLesson = CurriculumService::findLessonByFile($file);
             $title = $manifestLesson['title'] ?? basename($file, '.md');
             $existingLesson = \App\Core\Database::selectOne(
-                "SELECT id, course_id FROM lessons WHERE title = ? OR markdown_content LIKE ? LIMIT 1",
-                [$title, '%' . $file . '%']
+                "SELECT id, course_id FROM lessons WHERE curriculum_key = ? OR title = ? OR markdown_content LIKE ? LIMIT 1",
+                [$file, $title, '%' . $file . '%']
             );
             $courseId = $existingLesson
                 ? (int)$existingLesson['course_id']
@@ -283,14 +283,14 @@ class CurriculumController
             if ($existingLesson) {
                 $lessonId = (int)$existingLesson['id'];
                 \App\Core\Database::query(
-                    "UPDATE lessons SET storage_type = 'api_upload', video_uuid = ?, bunny_video_id = '', local_path = ?, hls_url = ?, thumbnail_url = ?, duration_seconds = ?, encoding_status = 'ready', ai_video_url = ? WHERE id = ?",
-                    [$uploadResult['video_uuid'], $uploadResult['local_path'], $uploadResult['hls_url'], $uploadResult['thumbnail_url'], $uploadResult['duration'] ?? 0, $videoUrl, $lessonId]
+                    "UPDATE lessons SET curriculum_key = ?, storage_type = 'api_upload', video_uuid = ?, bunny_video_id = '', local_path = ?, hls_url = ?, thumbnail_url = ?, duration_seconds = ?, encoding_status = 'ready', ai_video_url = ? WHERE id = ?",
+                    [$file, $uploadResult['video_uuid'], $uploadResult['local_path'], $uploadResult['hls_url'], $uploadResult['thumbnail_url'], $uploadResult['duration'] ?? 0, $videoUrl, $lessonId]
                 );
             } else {
                 $lessonId = \App\Core\Database::insert(
-                    "INSERT INTO lessons (course_id, title, sequence_order, storage_type, video_uuid, bunny_video_id, local_path, hls_url, thumbnail_url, duration_seconds, is_free_preview, encoding_status, ai_video_url)
-                     VALUES (?, ?, 1, 'api_upload', ?, '', ?, ?, ?, ?, 0, 'ready', ?)",
-                    [$courseId, $title, $uploadResult['video_uuid'], $uploadResult['local_path'], $uploadResult['hls_url'], $uploadResult['thumbnail_url'], $uploadResult['duration'] ?? 0, $videoUrl]
+                    "INSERT INTO lessons (course_id, title, curriculum_key, sequence_order, storage_type, video_uuid, bunny_video_id, local_path, hls_url, thumbnail_url, duration_seconds, is_free_preview, encoding_status, ai_video_url)
+                     VALUES (?, ?, ?, 1, 'api_upload', ?, '', ?, ?, ?, ?, 0, 'ready', ?)",
+                    [$courseId, $title, $file, $uploadResult['video_uuid'], $uploadResult['local_path'], $uploadResult['hls_url'], $uploadResult['thumbnail_url'], $uploadResult['duration'] ?? 0, $videoUrl]
                 );
             }
 
diff --git a/backend/app/Controllers/VideoController.php b/backend/app/Controllers/VideoController.php
index 4e0e474..d726a86 100644
--- a/backend/app/Controllers/VideoController.php
+++ b/backend/app/Controllers/VideoController.php
@@ -385,13 +385,16 @@ class VideoController
         VideoService::ensureSchema();
         CurriculumService::ensureSchema();
 
-        $rawId = $request->getParam('id') ?? '';
+        $curriculumKey = trim((string)($request->getQuery('curriculum_key') ?? ''));
+        $rawId = $curriculumKey !== '' ? $curriculumKey : ($request->getParam('id') ?? '');
         $lesson = null;
 
-        if (is_numeric($rawId) && (int)$rawId > 0) {
+        if ($curriculumKey !== '') {
+            $lesson = Database::selectOne("SELECT * FROM lessons WHERE curriculum_key = ? LIMIT 1", [$curriculumKey]);
+        } elseif (is_numeric($rawId) && (int)$rawId > 0) {
             $lesson = Database::selectOne("SELECT * FROM lessons WHERE id = ? LIMIT 1", [(int)$rawId]);
         } elseif (!empty($rawId)) {
-            $lesson = Database::selectOne("SELECT * FROM lessons WHERE title LIKE ? OR local_path LIKE ? OR markdown_content LIKE ? LIMIT 1", ["%{$rawId}%", "%{$rawId}%", "%{$rawId}%"]);
+            $lesson = Database::selectOne("SELECT * FROM lessons WHERE curriculum_key = ? OR title LIKE ? OR local_path LIKE ? OR markdown_content LIKE ? LIMIT 1", [$rawId, "%{$rawId}%", "%{$rawId}%", "%{$rawId}%"]);
             // Flutter curriculum lessons use the manifest slug (e.g. u1_l1_*),
             // while the database stores the canonical lesson title.
             if (!$lesson) {
diff --git a/backend/app/Services/VideoService.php b/backend/app/Services/VideoService.php
index f81effb..8792955 100644
--- a/backend/app/Services/VideoService.php
+++ b/backend/app/Services/VideoService.php
@@ -37,6 +37,12 @@ class VideoService
                 Database::query("ALTER TABLE lessons ADD COLUMN video_uuid CHAR(36) NULL AFTER storage_type");
             }
 
+            $colsCurriculumKey = Database::select("SHOW COLUMNS FROM lessons LIKE 'curriculum_key'");
+            if (empty($colsCurriculumKey)) {
+                Database::query("ALTER TABLE lessons ADD COLUMN curriculum_key VARCHAR(500) NULL AFTER title");
+                Database::query("ALTER TABLE lessons ADD INDEX idx_lessons_curriculum_key (curriculum_key)");
+            }
+
             $colsPath = Database::select("SHOW COLUMNS FROM lessons LIKE 'local_path'");
             if (empty($colsPath)) {
                 Database::query("ALTER TABLE lessons ADD COLUMN local_path VARCHAR(500) NULL AFTER bunny_video_id");
diff --git a/backend/database_schema.sql b/backend/database_schema.sql
index c840574..0103ff9 100644
--- a/backend/database_schema.sql
+++ b/backend/database_schema.sql
@@ -222,6 +222,7 @@ CREATE TABLE IF NOT EXISTS `lessons` (
   `id` BIGINT UNSIGNED NOT NULL AUTO_INCREMENT,
   `course_id` BIGINT UNSIGNED NOT NULL,
   `title` VARCHAR(255) NOT NULL,
+  `curriculum_key` VARCHAR(500) DEFAULT NULL COMMENT 'المسار الفريد لدرس الـManifest داخل storage/curriculum',
   `sequence_order` INT UNSIGNED NOT NULL DEFAULT 1,
   
   -- المعلم الحقيقي (Teacher Video)
@@ -249,6 +250,7 @@ CREATE TABLE IF NOT EXISTS `lessons` (
   `updated_at` TIMESTAMP NULL DEFAULT CURRENT_TIMESTAMP ON UPDATE CURRENT_TIMESTAMP,
   PRIMARY KEY (`id`),
   KEY `idx_lessons_course` (`course_id`),
+  KEY `idx_lessons_curriculum_key` (`curriculum_key`),
   KEY `idx_lessons_video_uuid` (`video_uuid`),
   CONSTRAINT `fk_lessons_course` FOREIGN KEY (`course_id`) REFERENCES `courses` (`id`) ON DELETE CASCADE
 ) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4 COLLATE=utf8mb4_unicode_ci;
diff --git a/backend/public/index.php b/backend/public/index.php
index 8a973a2..9331647 100644
--- a/backend/public/index.php
+++ b/backend/public/index.php
@@ -114,6 +114,7 @@ $router->post('/api/teacher/lessons/checkpoints',     [\App\Controllers\VideoCon
 $router->get('/api/student/lessons',                  [\App\Controllers\VideoController::class, 'getStudentLessons']);
 $router->get('/api/videos/stream/{uuid}',             [\App\Controllers\VideoController::class, 'streamLocalVideo']);
 $router->get('/api/videos/hls/{uuid}/{file}',         [\App\Controllers\VideoController::class, 'streamHls']);
+$router->get('/api/lessons/playback',                  [\App\Controllers\VideoController::class, 'getPlaybackData']);
 $router->get('/api/lessons/{id}/playback',            [\App\Controllers\VideoController::class, 'getPlaybackData']);
 
 // Student & Teacher Chat Routes (API-Driven, Authenticated)
diff --git a/backend/scripts/sync_curriculum_to_database.php b/backend/scripts/sync_curriculum_to_database.php
index f0c8be3..e5bd2d8 100644
--- a/backend/scripts/sync_curriculum_to_database.php
+++ b/backend/scripts/sync_curriculum_to_database.php
@@ -9,6 +9,10 @@ use App\Services\CurriculumService;
 
 echo "=== SAQEL ENTERPRISE CURRICULUM DATABASE SYNC ===\n";
 
+// Keep an existing production database compatible with the canonical
+// curriculum-key linkage before querying or inserting synchronized lessons.
+\App\Services\VideoService::ensureSchema();
+
 $manifestFile = __DIR__ . '/../storage/curriculum/manifest.json';
 if (!file_exists($manifestFile)) {
     die("Error: manifest.json not found at $manifestFile\n");
@@ -99,24 +103,24 @@ foreach ($manifest as $gradeKey => $grade) {
                     $cheatSheet = $les['cheat_sheet'] ?? null;
                     $socraticQuiz = isset($les['socratic_quiz']) ? json_encode($les['socratic_quiz'], JSON_UNESCAPED_UNICODE) : null;
 
-                    // Match existing lesson by course_id and title or file path
+                    // The manifest file path is the canonical, globally unique lesson key.
                     $dbLesson = Database::selectOne(
-                        "SELECT id FROM lessons WHERE course_id = ? AND title = ? LIMIT 1",
-                        [$courseId, $lessonTitle]
+                        "SELECT id FROM lessons WHERE curriculum_key = ? OR (course_id = ? AND title = ?) LIMIT 1",
+                        [$filePath, $courseId, $lessonTitle]
                     );
 
                     if (!$dbLesson) {
                         $lesId = Database::insert(
-                            "INSERT INTO lessons (course_id, title, sequence_order, ai_video_url, markdown_content, cheat_sheet_markdown, socratic_quiz_json, is_free_preview) 
-                             VALUES (?, ?, ?, ?, ?, ?, ?, 1)",
-                            [$courseId, $lessonTitle, $seqOrder, $aiVideoUrl, $mdContent, $cheatSheet, $socraticQuiz]
+                            "INSERT INTO lessons (course_id, title, curriculum_key, sequence_order, ai_video_url, markdown_content, cheat_sheet_markdown, socratic_quiz_json, is_free_preview)
+                             VALUES (?, ?, ?, ?, ?, ?, ?, ?, 1)",
+                            [$courseId, $lessonTitle, $filePath, $seqOrder, $aiVideoUrl, $mdContent, $cheatSheet, $socraticQuiz]
                         );
                         echo "    📄 [NEW] Lesson inserted: {$lessonTitle} (ID: {$lesId})\n";
                     } else {
                         $lesId = (int)$dbLesson['id'];
                         Database::query(
-                            "UPDATE lessons SET sequence_order = ?, markdown_content = ?, ai_video_url = COALESCE(?, ai_video_url), cheat_sheet_markdown = COALESCE(?, cheat_sheet_markdown), socratic_quiz_json = COALESCE(?, socratic_quiz_json) WHERE id = ?",
-                            [$seqOrder, $mdContent, $aiVideoUrl, $cheatSheet, $socraticQuiz, $lesId]
+                            "UPDATE lessons SET curriculum_key = ?, sequence_order = ?, markdown_content = ?, ai_video_url = COALESCE(?, ai_video_url), cheat_sheet_markdown = COALESCE(?, cheat_sheet_markdown), socratic_quiz_json = COALESCE(?, socratic_quiz_json) WHERE id = ?",
+                            [$filePath, $seqOrder, $mdContent, $aiVideoUrl, $cheatSheet, $socraticQuiz, $lesId]
                         );
                         echo "    🔄 [UPDATED] Lesson: {$lessonTitle} (ID: {$lesId})\n";
                     }