Premiere Pro 26.1 Beta Regression: app no longer displays custom on-screen controls for AE plugins

[FxFactory]

It appears that Premiere Pro 26.1 Beta contains a regression whereby the app fails to display any custom-onscreen UI in the Canvas window for any 3rd party transitions based on the After Effects plug-in SDK.

It appears as Premiere is simply skipping giving plugins any chance to handle events in layer and comp windows.

Steps to reproduce:

Follow these instructions in Premiere Pro 2025, just so you know what UI should be there. You can then repeat these steps in 2026 Beta, which fails to display the same UI.

- Download and install FxFactory 9 https://fxfactory.com/download/ 

- Launch FxFactory and download the Block Party transition

- Launch Premiere Pro 2025

- Apply the Block Party transition in between two clips on your timeline.

- Select the effect header in the inspector to display its custom on-screen UI in the Canvas:

- In the Canvas, you will notice a row of buttons provided by the plugin:

- Repeat the same steps in Premiere Pro 2026 Beta and notice that the on-screen UI never appears. 

Behind the scenes, Premiere Pro is failing to call the plugin for any events related to PF_Window_LAYER and 

PF_Window_COMP.

[Bruce Bullis]

Repro'd; we're urgently triaging the issue.

[Bruce Bullis]

Ok, I observed this happening at least once, but can no longer reproduce it using either "Block Party", nor the custom comp and ecw ui samples, from the AE SDK. Specifically: I'm seeing successful custom UI drawing from Block Party, CCU and Custom_ECW_UI plugins, in PPro beta 26.1.0x6.

Gabriele, feel free to send me any/all info you find, which may help improve the repro. 

[FxFactory]

I haven't been able to get the custom controls to appear at all in the Beta, but I'll keep flipping all the switches I can see, and if I get lucky in identifying the one that makes a difference I'll report back.

[Bruce Bullis]

For those following along, this seems to only impact transition plugins. When their Effect title is selected in the Effect Controls Panel, custom UI should be displayed in the Program monitor. In 25.6.3, it displays; in the current beta, it doesn't.