Nightly WeChat publish failures traced to flawed IP probe, not IP drift

A developer publishing to a WeChat Official Account had been blocked for 20+ nights by errcode 40164, an IP whitelist rejection, and had been treating the failures as a drifting outbound IP. On a late check, the probing script returned an IPv6 address that WeChat's whitelist cannot accept, exposing two flaws in the v1 tool. The first was that it could return IPv6 addresses, and the second was that its echo services sit behind Cloudflare, so the addresses it reported belonged to Cloudflare edge nodes rather than the local egress. The developer built a v2 probe that reads the IP WeChat itself reports in its error message and cross-checks it against IPv4-only echo services, all of which agreed on one address. The v2 tool also flags addresses within known CDN ranges as unusable for whitelisting.