UXP Extension for Premiere Pro 2025 Beta: uxp.host.eval() Issue & Timeline Access

Premiere Pro
1

Hello !

I’ve developed a UXP extension for Premiere Pro 2025 Beta to automate video editing workflows. After extensive testing, I’ve encountered critical blocking issues that I need community help with.

Project Context
Goal: Automate YouTube workflow tasks (clip scaling, audio sync, timeline manipulation)
Target: Adobe Premiere Pro 2025 Beta
Approach: UXP Extension with ExtendScript bridge

What I’ve Successfully Tested

Native UXP API Access - This works perfectly:

const project = await Project.getActiveProject();
console.log(project.name); // ✅ Returns actual project name
const sequence = project.activeSequence;
console.log(sequence.name); // ✅ Returns actual sequence name

Manifest Configuration:

  • Tested manifestVersion 4 with proper permissions
  • ExtendScript permissions in hostCapabilities
  • Adobe Spectrum UI integration working

ExtendScript Fallback:

  • Complete ExtendScript implementation works when run manually
  • Native dialog interface functional
  • Timeline manipulation successful via pure ExtendScript

Critical Blocking Issues

Issue 1: uxp.host.eval() Always Returns False

console.log('uxp.host.eval exists:', !!uxp.host.eval); // Always false

Manifest Configuration Tested:

{
  "manifestVersion": 4,
  "requiredPermissions": {
    "allowCodeGenerationFromStrings": true,
    "localFileSystem": "request"
  },
  "hostCapabilities": {
    "premierepro": {
      "permissions": ["ExtendScript", "allowCodeGenerationFromStrings"]
    }
  }
}

Issue 2: Extension Load Timeouts

  • Both complex and minimal extensions fail with “Plugin load timed out”
  • Even 300-line extensions cannot load successfully
  • UXP Developer Tool consistent timeout errors

Issue 3: Timeline Access Limitation

  • Can access project/sequence metadata :white_check_mark:
  • Cannot access clips, tracks, or timeline components :cross_mark:
  • Missing bridge between UXP API and actual editing operations

Technical Approaches Attempted

Approach 1: Direct uxp.host.eval

if (uxp.host && uxp.host.eval) {
    const script = `
        var clip = app.project.activeSequence.videoTracks[0].clips[0];
        clip.components[1].properties[1].setValue([36, 36], true);
    `;
    const result = await uxp.host.eval(script);
} else {
    console.log('uxp.host.eval not available'); // Always executes
}

Approach 2: Adobe OAuth2/IMS Authentication

  • Researched Adobe Developer Console setup
  • Implemented OAuth2 flow for Creative Cloud API
  • Authentication successful but uxp.host.eval still unavailable

Approach 3: Alternative UXP APIs

// Works for metadata only
const sequenceEditor = SequenceEditor.getEditor();
// No access to actual clips or timeline manipulation

Specific Questions for Community

Question 1: uxp.host.eval Availability
Has anyone successfully used uxp.host.eval() in Premiere Pro 2025 Beta?

  • What specific authentication/setup is required?
  • Are there manifest configuration requirements I’m missing?
  • Is this feature disabled in the Beta version?

Question 2: Timeline Manipulation Alternatives
Are there alternative UXP APIs for direct timeline access?

  • Methods to access clip properties (Motion, scale, position)?
  • APIs for track manipulation?
  • Undocumented UXP interfaces for editing operations?

Question 3: Extension Load Issues
Anyone experiencing UXP extension timeout issues?

  • Is this a known issue with Premiere Pro Beta?
  • Workarounds for load timeout problems?
  • Minimum system requirements causing issues?

Question 4: Development Environment
What’s the recommended setup for UXP development with Premiere Pro?

  • Specific UXP Developer Tool version compatibility?
  • Premiere Pro version requirements?
  • System configuration recommendations?

Current Working Solutions

ExtendScript Fallback (Fully Functional):

// This works when run manually in Premiere Pro
(function() {
    var sequence = app.project.activeSequence;
    var clip = sequence.videoTracks[0].clips[0];
    // Direct timeline manipulation successful
    for (var i = 0; i < clip.components.numItems; i++) {
        var component = clip.components[i];
        if (component.displayName === "Motion") {
            component.properties[1].setValue([36, 36], true);
        }
    }
})();

System Information

  • Premiere Pro: 2025 Beta (latest)
  • UXP Developer Tool: v2.1+
  • macOS: Latest version
  • Testing: Extensive debugging over multiple sessions

Expected Outcome
I need uxp.host.eval() functionality to bridge UXP interface with ExtendScript automation, enabling seamless workflow automation within the extension panel.

Code Available
I have a complete codebase with all testing approaches documented. Happy to share specific code snippets or collaborate on solutions.

Any insights from the community would be incredibly valuable. This seems like a fundamental UXP limitation that others might have encountered.