Two independent authentication layers
An Access token authorizes reaching the SSH application; an SSH key authorizes a host login. Neither should replace the other. Pinning the SSH host key prevents DNS or route changes from silently substituting another machine.
Origin validation
An HTTP header alone is not proof of identity. The backend validates Google ID-token signatures, issuer, audience, expiration, nonce, verified email and the owner allowlist before issuing an application session. It never trusts identity headers. A loopback listener prevents the application from exposing an unprotected LAN port.
DNS and certificate boundaries
The wiki uses its own DNS-only GitHub Pages record and HTTPS certificate. It is a nested subdomain, so relying on a Cloudflare certificate that covers only one subdomain level would be incorrect. Portal and SSH records use the existing tunnel, preserving its production AI ingress rule.