diff --git a/backend/scripts/diagnose_tree.php b/backend/scripts/diagnose_tree.php
new file mode 100644
index 0000000..cb5239d
--- /dev/null
+++ b/backend/scripts/diagnose_tree.php
@@ -0,0 +1,98 @@
+<?php
+
+declare(strict_types=1);
+
+require_once dirname(__DIR__) . '/app/bootstrap.php';
+
+use App\Core\Database;
+use App\Services\CurriculumService;
+
+echo "=== DIAGNOSING CURRICULUM TREE ENRICHMENT ===\n\n";
+
+// 1. Database check
+try {
+    $approvedCount = Database::selectOne("SELECT COUNT(*) as cnt FROM curriculum_lessons WHERE source_status = 'approved'");
+    echo "1. Database Status:\n";
+    echo "   Approved curriculum lessons in DB: " . ($approvedCount['cnt'] ?? 0) . "\n";
+    
+    $samples = Database::select("SELECT id, uuid, source_manifest_path, source_status FROM curriculum_lessons WHERE source_status = 'approved' LIMIT 3");
+    foreach ($samples as $s) {
+        echo "   - [{$s['source_status']}] uuid: {$s['uuid']} | path: {$s['source_manifest_path']}\n";
+    }
+} catch (Throwable $e) {
+    echo "   ERROR querying curriculum_lessons: " . $e->getMessage() . "\n";
+}
+
+// 2. Storage manifest.json check
+echo "\n2. Live manifest.json check:\n";
+$tree = CurriculumService::getCurriculumTree();
+if (empty($tree)) {
+    echo "   ERROR: CurriculumService::getCurriculumTree() returned empty array!\n";
+    echo "   Check: backend/storage/curriculum/manifest.json\n";
+} else {
+    $firstLesson = $tree['grade_10']['subjects']['math_10']['semesters']['semester_1']['units']['unit_01']['lessons'][1] ?? null;
+    echo "   Grade 10 math lesson 1 in manifest.json:\n";
+    if ($firstLesson) {
+        echo "   - id: " . ($firstLesson['id'] ?? '') . "\n";
+        echo "   - file: " . ($firstLesson['file'] ?? '') . "\n";
+    } else {
+        echo "   - Not found at expected key!\n";
+    }
+}
+
+// 3. Test Enrichment Logic directly
+echo "\n3. Testing Tree Enrichment Logic:\n";
+try {
+    $approvedLessons = Database::select("SELECT id, uuid, source_manifest_path FROM curriculum_lessons WHERE source_status='approved'");
+    $byPath = [];
+    foreach ($approvedLessons as $row) {
+        $p = (string)$row['source_manifest_path'];
+        $byPath[$p] = [
+            'curriculum_lesson_id' => (string)$row['uuid'],
+            'has_video' => false,
+        ];
+    }
+    echo "   Mapped " . count($byPath) . " paths in \$byPath lookup table.\n";
+
+    $matchCount = 0;
+    foreach ($tree as &$grade) {
+        foreach (($grade['subjects'] ?? []) as &$subject) {
+            foreach (($subject['semesters'] ?? []) as &$semester) {
+                foreach (($semester['units'] ?? []) as &$unit) {
+                    foreach (($unit['lessons'] ?? []) as &$lesson) {
+                        $path = (string)($lesson['file'] ?? '');
+                        if (isset($byPath[$path])) {
+                            $lesson = array_merge($lesson, $byPath[$path]);
+                            $matchCount++;
+                        }
+                    }
+                }
+            }
+        }
+    }
+    unset($grade, $subject, $semester, $unit, $lesson);
+
+    echo "   Enriched matches in manifest.json tree: {$matchCount}\n";
+    
+    // Check if first lesson got enriched
+    $sampleEnriched = $tree['grade_10']['subjects']['math_10']['semesters']['semester_1']['units']['unit_01']['lessons'][1] ?? null;
+    if (!empty($sampleEnriched['curriculum_lesson_id'])) {
+        echo "\n=== SUCCESS! Enrichment logic works perfectly in CLI! ===\n";
+        echo "Sample enriched lesson:\n";
+        print_r($sampleEnriched);
+        echo "\nNOTE: If curl returns empty while CLI works, PHP-FPM has cached the old bytecode in OPcache.\n";
+        echo "Run: systemctl reload php8.3-fpm (or your server php-fpm service) to reload PHP-FPM.\n";
+    } else {
+        echo "\n=== WARNING: Sample lesson did not get enriched. Checking sample path... ===\n";
+        $samplePath = $sampleEnriched['file'] ?? 'none';
+        echo "Sample path is: '{$samplePath}'\n";
+        echo "Is set in \$byPath? " . (isset($byPath[$samplePath]) ? "YES" : "NO") . "\n";
+        if (!isset($byPath[$samplePath])) {
+            echo "Top 5 paths in \$byPath:\n";
+            print_r(array_slice(array_keys($byPath), 0, 5));
+        }
+    }
+} catch (Throwable $e) {
+    echo "   EXCEPTION during enrichment: " . $e->getMessage() . "\n";
+    echo $e->getTraceAsString() . "\n";
+}