Ah that was the issue. I made the assumption that the alembic would work the same as other tools, setting the parent would control the children unless I override a specific child.

Interesting that the new simulation caching (via alembic) appears to automatically apply merge connected and bake as alembic doesn't. That gives different behavior when using the default settings for what at first appear to be equivalent operations.

Ah well. Thanks for the reply and the insight.

The title pretty much says it all. As a minimal reproduceable test I created a file with a cube on a plain. I added a bullet.collider tag to the plain and put the cube into a voroni fracture with a bullet.rigidbody tag. I then baked to alembic with the default settings.

When I imported the alembic the playback was correct, however retiming seem to be completely broken. I unchecked 'Use Animation' and keyframed the 'frame' parameter to reverse the animation, which failed entirely, the animation still played forward. I am attching a zip file containing the c4d file and the alembic to this.

Any assistance (even just confirming that this feature is borked) would be helpful.

Hmmm apparently uploading files here doesn't work. Here is a dropbox link for the zip file: https://www.dropbox.com/scl/fi/grpbjnpecwwb2ij9yzk8g/alembic.zip?rlkey=v895dxz6zncjcdf1lu2g4lk7z&st=8bp3hfko&dl=0

Update: I corrected my post to indiciate that I was using bullet tags. When I switched to the new simulation tags and cached the simulation all worked as expected. This still leaves the question of "What is up with the bullet tags?".