Index: scripts/backfill-durations.mjs
===================================================================
--- scripts/backfill-durations.mjs	(revision 3e86f1cca344a75facd291ef34a6bf56445bf532)
+++ scripts/backfill-durations.mjs	(revision 3e86f1cca344a75facd291ef34a6bf56445bf532)
@@ -0,0 +1,53 @@
+#!/usr/bin/env node
+/**
+ * Backfill audio_tracks.duration voor bestaande tracks die nog géén duur hebben.
+ * Leest de duur uit het mp3-bestand via ffmpeg (probeDuration — geen aparte
+ * ffprobe-binary nodig). Idempotent: pakt alleen rijen met duration NULL of 0,
+ * dus veilig herhaalbaar.
+ *
+ *   npm run backfill:durations
+ *
+ * Respecteert AUDIO_PATH (env) net als de upload-route.
+ */
+import path from 'path';
+import fs from 'fs';
+import { fileURLToPath } from 'url';
+import db from '../src/config/database.js';
+import { probeDuration } from '../src/services/AudioTranscoder.js';
+
+const __dirname = path.dirname(fileURLToPath(import.meta.url));
+const AUDIO_DIR = path.resolve(
+  process.env.AUDIO_PATH || path.join(__dirname, '..', 'storage', 'audio')
+);
+
+// storage_path is absoluut (opgeslagen bij upload); val terug op AUDIO_DIR/filename.
+function resolveFile(t) {
+  const candidates = [t.storage_path, t.filename ? path.join(AUDIO_DIR, t.filename) : null].filter(Boolean);
+  for (const c of candidates) {
+    try { if (fs.statSync(c).isFile()) return c; } catch { /* volgende kandidaat */ }
+  }
+  return null;
+}
+
+const rows = db.prepare(`
+  SELECT t.id, m.filename, m.storage_path
+  FROM audio_tracks t
+  JOIN media m ON m.id = t.media_id
+  WHERE (t.duration IS NULL OR t.duration = 0) AND m.filename IS NOT NULL
+`).all();
+
+console.log(`[backfill-durations] ${rows.length} track(s) zonder duur`);
+const update = db.prepare('UPDATE audio_tracks SET duration = ? WHERE id = ?');
+
+let ok = 0, miss = 0, fail = 0;
+for (const t of rows) {
+  const file = resolveFile(t);
+  if (!file) { console.warn(`  - ${t.id}: bestand niet gevonden (${t.filename})`); miss++; continue; }
+  try {
+    const sec = await probeDuration(file);
+    if (sec && sec > 0) { update.run(sec, t.id); ok++; console.log(`  ✓ ${t.id}: ${sec}s`); }
+    else { console.warn(`  - ${t.id}: geen duur uit ffmpeg`); fail++; }
+  } catch (e) { console.warn(`  - ${t.id}: ${e.message}`); fail++; }
+}
+console.log(`[backfill-durations] klaar — ${ok} bijgewerkt, ${miss} bestand-mist, ${fail} mislukt`);
+process.exit(0);