How-to develop a third-party panel plugin

Hi,

I'm developing a third-party panel plugin for Adobe Illustrator 2026 (version 30.5.1 on Windows), but I'm stuck on which framework to use.

Here's what I've tried and found:

• CEP: Placed the extension in both C:\Program Files (x86)\Common Files\Adobe\CEP\extensions\ and %appdata%\Adobe\CEP\extensions\, set PlayerDebugMode=1 in the registry for both CSXS.11 and CSXS.12, but the panel never appears under Window → Extensions.
• UXP: I understand UXP is not yet available to third-party developers for Illustrator.

My goal is to build a persistent side panel (similar to the Properties panel) that calls an external API and helps designers with their workflow.

My questions:

1. Is CEP still supported in Illustrator 2026, and if so, what am I doing wrong?
2. Is there any other framework available for building panel-type plugins for Illustrator 2026?
3. Is there a roadmap for when UXP will be available for third-party Illustrator developers?

Any guidance would be greatly appreciated. Thank you.