SameSite=Strict prevents cookies from being sent when iframe content (like the LND UI at /app/lnd/) fetches endpoints on the parent origin (/lnd-connect-info). Lax still protects against CSRF on POST requests but allows same-site GET navigations and fetches from iframes. This was the root cause of "Failed to fetch" on LND Connect. Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>