Download Stems button now zips all stem files into a single .zip

- New /admin/request/<id>/download-stems endpoint
- Parses stems_url (label: url; label: url format), fetches each stem file,
  bundles them into a zip served as an attachment download
- If MusicGPT returns a single .zip bundle URL, redirects directly
- Template button now points to the zip endpoint instead of raw CDN URLs

app.py

@@ -34,6 +34,9 @@ import hmac
 import shutil
 import time
 import json
+import io
+import zipfile
+import re
 from pathlib import Path
 
 # Flask and related imports
@@ -790,6 +793,75 @@ def audio(token, version):
     abort(404)
 
 
+@app.route('/admin/request/<int:rid>/download-stems')
+def admin_download_stems(rid):
+    """Download all stems files for a request as a single .zip archive."""
+    redir = require_admin()
+    if redir:
+        return redir
+    req = get_request_by_id(rid)
+    if not req:
+        abort(404)
+    req = dict(req)
+
+    stems_url = req.get('stems_url') or ''
+    if not stems_url:
+        flash('No stems available to download.', 'error')
+        return redirect(url_for('admin_request', rid=rid))
+
+    # Parse the stems_url field. It can be:
+    #   1. A single bundle/zip URL (use directly)
+    #   2. "label1: url1; label2: url2" (multiple individual stem files)
+    #   3. Just a bare URL
+    urls = []
+    if ';' in stems_url or ': ' in stems_url:
+        # Multiple stems: "instrumental: https://...; vocals: https://..."
+        parts = stems_url.split(';')
+        for part in parts:
+            part = part.strip()
+            if not part:
+                continue
+            # Split on first ": " to separate label from URL
+            if ': ' in part:
+                label, url = part.split(': ', 1)
+                urls.append((label.strip(), url.strip()))
+            else:
+                urls.append(('stem', part))
+    else:
+        urls.append(('stems', stems_url.strip()))
+
+    if not urls:
+        flash('No stems files found.', 'error')
+        return redirect(url_for('admin_request', rid=rid))
+
+    # If there's only one URL and it's already a .zip, redirect directly.
+    if len(urls) == 1 and urls[0][1].endswith('.zip'):
+        return redirect(urls[0][1])
+
+    # Download each stem file and bundle them into a zip in memory.
+    import requests as req_lib
+    buf = io.BytesIO()
+    with zipfile.ZipFile(buf, 'w', zipfile.ZIP_DEFLATED) as zf:
+        for label, url in urls:
+            try:
+                r = req_lib.get(url, timeout=60)
+                r.raise_for_status()
+                # Derive a filename from the URL or label.
+                filename = url.split('/')[-1] if '/' in url else f"{label}.mp3"
+                # If the URL has no extension, use the label.
+                if '.' not in filename:
+                    filename = f"{label}.mp3"
+                zf.writestr(filename, r.content)
+            except Exception:
+                # Skip files that fail to download, but include the rest.
+                pass
+    buf.seek(0)
+
+    title = req.get('suno_title') or req.get('name') or f'request_{rid}'
+    download_name = f"stems_{title}.zip"
+    return send_file(buf, mimetype='application/zip', as_attachment=True, download_name=download_name)
+
+
 # ---------------------------------------------------------------------------
 # Admin routes
 # ---------------------------------------------------------------------------

templates/admin/request.html

@@ -618,7 +618,7 @@
             {% endif %}
             {% if req.stems_url %}
             <div class="actions">
-              <a href="{{ req.stems_url }}" target="_blank" rel="noopener noreferrer" class="button-link" style="display:inline-flex;align-items:center;gap:.4rem;padding:.5rem 1rem;background:#4b5563;border-radius:.375rem;color:#fff;text-decoration:none;font-size:.875rem">⬇ Download Stems</a>
+              <a href="{{ url_for('admin_download_stems', rid=req.id) }}" class="button-link" style="display:inline-flex;align-items:center;gap:.4rem;padding:.5rem 1rem;background:#4b5563;border-radius:.375rem;color:#fff;text-decoration:none;font-size:.875rem">⬇ Download Stems (zip)</a>
             </div>
             {% endif %}