Custom UI SDK Image Gallery not rendering in Appian 25.4 (Portals & Sites)

Hi everyone,

I am developing a Custom UI SDK component (JavaScript/Web Component) to create a custom image gallery. My goal is to have this component working seamlessly in both Appian Sites and Appian Portals in version 25.4.

The Problem: I have tried using existing plugins and my own custom code, but images are not rendering. When passing the Document IDs to the SDK, the component fails to display the images. I suspect this is due to session/authentication restrictions or how the source URL is being handled, especially considering the architectural differences between Portals and Sites.

Technical Details:

• Version: Appian 25.4.

• Component type: UI SDK (JavaScript).

• Current approach: Passing a list of Document IDs and trying to resolve them within the component.

• Issue: The <img> tags remain empty or return 401/403 errors when the component is loaded.

What I need help with:

1. What is the best practice for passing Appian Documents to a Custom UI SDK so they are accessible in both Portals (Public/Service Account) and Sites (User Session)?

2. Are there specific CORS or Security settings I should check to ensure the SDK can fetch these assets?

3. Through the link I get with document url, I can download it but I can't view it

Any code snippets or architectural advice would be greatly appreciated.

Thanks in advance!