MogrtText write-back causes getStartValue() to reject previously readable text

Summary

In Premiere Pro (Beta) 27.0.0 Build 57, a MogrtText value can initially be read successfully through the public UXP API. However, after writing the text back once through a transaction, the same parameter can no longer be read with getStartValue().

Environment

- Adobe Premiere Pro (Beta): 27.0.0 BETA StaticLib (Build 57)
- Premiere UXP: uxp-9.4.0-local
- After Effects: 26.5.0 (Build 89)
- Adobe UXP Developer Tools: 2.3.0.5
- Windows 11 Home, Version 25H2 (OS Build 26200.9457)

MOGRT configuration

The MOGRT was created in After Effects 26.5.0.
It contains one non-animated text layer with uniform styling.

Exposed text parameter:
ShizukuText

Initial text:
字幕テスト

Steps to reproduce

1. Place the AE-created MOGRT on V1.
2. Retrieve the exposed ShizukuText parameter through the UXP API.
3. Call getStartValue().
4. The returned value is successfully recognized as MogrtText.
5. getText() successfully returns "字幕テスト".
6. Call setText("字幕テスト成功！") on the MogrtText value.
7. Create a keyframe and a set-value action, then execute it through executeTransaction().
8. executeTransaction() returns true.
9. Reacquire the same MOGRT clip and ShizukuText parameter.
10. Call getStartValue() again.

Expected result

The parameter should remain readable as MogrtText and return the updated text.

Actual result

After the write transaction, the MOGRT disappears from the Program Monitor although the clip remains on V1.

The ShizukuText parameter still exists and isTimeVarying() succeeds and returns false.

However, getStartValue() now fails with the following exact error:

MogrtText is encoded in a format that is not supported by this version of the API.

Before the write, the same parameter was readable and getText() returned "字幕テスト".

Premiere's Properties > Template panel continues to display the original value "字幕テスト" after the failed state.

The thrown error is a string rather than an Error object:
typeof error: string

Additional note

This report does not assume that Japanese text, the font, AE-created MOGRTs, or Premiere Beta itself is the root cause. These have not been independently established as the cause.

The issue reproduced during this test after one write transaction; automatic retries were not performed.


[Moved to Premiere (Beta) by a moderator］