update dev notes

.dev-notes/2025-12-30.md

@@ -192,6 +192,23 @@ function wakeUpN8n() {
 4. **Transaction pooler (6543)** - Better for ephemeral environments
 5. **Built-in /healthz** - Simpler than custom webhook for wake-up
 6. **tini as init** - Proper signal handling for container shutdown
+7. **Space must be PUBLIC** - Private Spaces return 404 when accessing the app URL directly. Change visibility in Settings > Visibility > Public
+
+---
+
+## Troubleshooting
+
+### 404 Not Found when accessing the Space URL
+- **Cause**: Space is set to Private
+- **Solution**: Go to HF Space Settings > Change visibility from Private to Public
+
+### "self-signed certificate in certificate chain" error
+- **Cause**: Supabase SSL certificate verification
+- **Solution**: Set `DB_POSTGRESDB_SSL_REJECT_UNAUTHORIZED=false` in HF Spaces secrets
+
+### "refused to connect" in HF preview iframe
+- **Cause**: n8n blocks iframe embedding (X-Frame-Options: sameorigin)
+- **Solution**: Click "Open in new tab" or access the URL directly in browser
 
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