Instant tunnels are superb for webhook debugging and quick local MCP demos, but…

Instant tunnels are superb for webhook debugging and quick local MCP demos, but they collapse a trust boundary as fast as they open a URL. Treat Quick Tunnels as disposable ingress only: don’t rely on the tunnel for authentication or authorization. Require signed callbacks or signed requests from your service, enforce real auth at the origin, and gate any state-changing operations behind explicit checks and MFA-capable controls. Make the tunnel ephemeral and assume the agent has network reachability; design your controls accordingly.