Hair particles not following their cap (but only on cycles render)

Well OK, I found this to be weird enough: I have a character, full with some cap with hair attached and what not. But the moment I rig the character (It has 1 subdiv level) hair behaves as expected on viewports and eevee, but remains on rest position only in cycles render.
I am using a mesh deform to keep the cap in place when character moves around. Found out that if I remove the subdiv modifier from the main mesh, it will work as expected.
So my workaround so far: hide the original mesh in render, and duplicate it (with its subdivision) and keep the original one without it. Alt solution would be to just skin the hair cap to the skeleton, but eyelashes still would need to be done this way to work with mesh shapes.

Is this behaviour intended or is it a bug?? I’m pretty new to Blender so I tried to reproduce my usual pipeline for these kind of characters. Am I missing something?

Hey Abishai, welcome to Blender and the forums!

My first question would be whether that subdiv modifier is enabled for rendering?

Might help if you can post a screen grab of the modifier panel, or a stripped down version of the .blend file.

Hi thanks for your awnser! I’ve been further looking into the issue:

Well this is my character, with half-done hair (I was upset at the fact it wasnt working as I wanted, so I didnt bother with it very munch) So the moment I move the head around (eyelashes are hair systems as well)

So, what I found out is, if you subdivide the mesh on render time in any way, it “breaks” weighting done by SurfaceDeform applied to the cap. I know it could be plain logic and thus, intended, but it shouldn’t work like this (as armature modifier is not broken by this fact in any way) This sadly, includes the super-cool dynamic subdivision based on camera distance :frowning:

So the workaround should be either subdividing a copy of the original mesh, or bind the hair cap after a fixed subdivision is done.

So my question now is: maybe shall I report it as a bug?