2026-10-19, for the maintainer's questions in the ocx2 thread (ca6f0cf49f): whether the need is a network-wide sync trigger or NAT traversal, peers behind NATs without the public server, Tailscale's and Syncthing's hosted parts, UPnP, NAT-PMP and PCP, and the Syncthing thread 22471. Four readers each read sources for one part, each claim with its source; one writer answered the questions; one checker opened every source and corrected twelve sentences that overstated.

The answer, in short: the trigger needs no NAT traversal, since a node's request outward reaches the public server through nearly any NAT; the smallest thing is a wait page on the server that answers once its receipt number passes the one the node last saw. Peers syncing without the public server need a machine both can reach, as Tailscale's and Syncthing's do.

The attachment sync-trigger-research.tar, plain, holds the question, each reader's claims with sources, the draft, and the checked reply with what the checker changed and why.