# UXP plugin can't install in 27 using UPIA

**URL:** <https://forums.creativeclouddeveloper.com/t/uxp-plugin-cant-install-in-27-using-upia/12135>\
**Category:** UXP Plugin API\
**Tags:** bug, uxp\
**Created:** [August 29, 2026, 8:24pm UTC](https://forums.creativeclouddeveloper.com/t/uxp-plugin-cant-install-in-27-using-upia/12135 "2026-08-29T20:24:01Z")\
**Posts on this page:** 3\
**Page:** 1

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**Author:** ![bimargulies](https://sea1.discourse-cdn.com/flex015/user_avatar/forums.creativeclouddeveloper.com/bimargulies/32/5156_2.png) [@bimargulies](https://forums.creativeclouddeveloper.com/u/bimargulies)\
**Post date:** [August 29, 2026, 8:24pm UTC](https://forums.creativeclouddeveloper.com/t/uxp-plugin-cant-install-in-27-using-upia/12135/1 "2026-08-29T20:24:01Z")

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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.

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<div class="post-metadata">

**Author:** ![bimargulies](https://sea1.discourse-cdn.com/flex015/user_avatar/forums.creativeclouddeveloper.com/bimargulies/32/5156_2.png) [@bimargulies](https://forums.creativeclouddeveloper.com/u/bimargulies)\
**Post date:** [August 29, 2026, 8:25pm UTC](https://forums.creativeclouddeveloper.com/t/uxp-plugin-cant-install-in-27-using-upia/12135/2 "2026-08-29T20:25:34Z")

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On the other hand, opening the ccx file works, which was broken in 27.9.

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<div class="post-metadata">

**Author:** ![bimargulies](https://sea1.discourse-cdn.com/flex015/user_avatar/forums.creativeclouddeveloper.com/bimargulies/32/5156_2.png) [@bimargulies](https://forums.creativeclouddeveloper.com/u/bimargulies)\
**Post date:** [August 29, 2026, 8:44pm UTC](https://forums.creativeclouddeveloper.com/t/uxp-plugin-cant-install-in-27-using-upia/12135/3 "2026-08-29T20:44:30Z")

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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.