A plugin that installed with upia under 27.9 fails to install under 27.10.
The UPIA error message is Installing extension with file path = /Users/bensonmargulies/Downloads/c41.ccx
Failed to install, status = -267!.
EMCL.log says, “Failed to generate mxi for uxp extension)” which is bizarre.
On the other hand, opening the ccx file works, which was broken in 27.9.
Claude and I found the bottom of this hole.
The current UXP manifest schema says host is an array (to allow multiple host apps), and that’s what @bubblydoo/vite-uxp-plugin writes. The UXP runtime and UDT accept either form. Creative Cloud’s installer only accepts the object form — with the array it can’t generate the legacy MXI and bails with status = -267 (Failed to generate mxi for uxp extension in EMCL.log). UDT’s Package step silently collapses host to an object; that’s why its output installs.
This also retro-explains the whole -267 saga: it wasn’t purely a CCD regression — the array host was always the problem. PS 27.9’s CLI path tolerated it; 27.10 doesn’t.