abcd dashboard start never starts on a Mac whose Tailscale cannot reach its own IPv6 address. Start listens on both of the computer's Tailscale addresses and requires a self-check fetch to answer on every one; on 2026-10-09, with Tailscale 1.102.4 on macOS, a TCP connection to the computer's own Tailscale IPv4 address succeeded while one to its own Tailscale IPv6 address timed out, so the IPv6 self-check failed and start stopped the dashboard with 'could not be reached from this computer ... check that nothing on this computer blocks the port' (exit 1). Nothing blocks the port; the dashboard is unusable from every device.

abcd dashboard start never starts on a Mac whose Tailscale cannot reach its own IPv6 address. Start listens on both of the computer's Tailscale addresses and requires a self-check fetch to answer on every one; on 2026-10-09, with Tailscale 1.102.4 on macOS, a TCP connection to the computer's own Tailscale IPv4 address succeeded while one to its own Tailscale IPv6 address timed out, so the IPv6 self-check failed and start stopped the dashboard with 'could not be reached from this computer ... check that nothing on this computer blocks the port' (exit 1). Nothing blocks the port; the dashboard is unusable from every device.

Grounds

• pursued: dropping an unreachable address instead of stopping makes the dashboard usable on a Mac whose Tailscale cannot reach its own IPv6, without weakening the gate on the kept addresses; shown wrong if a dropped address is still served, or if this computer is admitted on any address