Early-warning thread: what broke and when

[SysAdminDoc]

When YouTube changes something, this thread is where the first reports land, and speed genuinely matters: the earlier a breakage pattern shows up here, the faster a rule or engine fix ships.

When you post, include four things: your browser, your userscript manager and its version, what you saw (ad played, black screen, endless spinner, playback stutter), and roughly when it started. YouTube rolls changes gradually, so two users can see different behavior on the same day, and that spread is diagnostic information in itself.

Quiet periods are worth a post too. If you've had a clean week on a setup that was breaking before, saying so confirms a fix actually landed for someone other than me.