Curve objects with Curve to Tube Modifier are missing texture coordinates after export

[3ditsb]

Describe the bug
When exporting curve objects with the "Curve To Tube" modifier, they are missing texture coordinates and don't show any texture in gltf viewer.
The same file exported from Blender 5.0.1 works fine.

To Reproduce
Steps to reproduce the behavior:

1. Open attached blend-file
2. Export GLB with Apply Modifiers enabled (or File -> Export All Collections)
3. Open the exported GLB file in gltf viewer (https://gltf-viewer.donmccurdy.com/)
4. The texture is visible in blender but not in gltf viewer. Also there is a validation error "MESH_PRIMITIVE_TOO_FEW_TEXCOORDS".

Expected behavior
The texture from the blend file should be visible on the curve object after export.

Screenshots

.blend file/ .gltf (mandatory)
CurveToTube_Bug.zip

Version

• OS: Windows 11
• Blender Version 5.1

Additional context
It seems like a change from Blender 5.0.1 to 5.1. Applying the modifier manually and exporting also doesn't immediately fix the issue, even though the object seems to have a UVMap. It is necessary to enter Edit-Mode once before exporting, then it works as expected.

[julienduroure]

I can confirm the bug
Setting Blender 5.1 with glTF 5.0 does not solve the bug, so the root cause may be in Blender itself, not glTF I/O.
Investigation and bisecting in progress

[julienduroure]

Bisecting found: https://projects.blender.org/blender/blender/pulls/150112

[julienduroure]

Blender bug created: https://projects.blender.org/blender/blender/issues/156415