HI,

When I'm saving a session displaying 3D image stacks as surfaces into a csx file, I get this error:

TypeError: object of type 'SurfaceUpdaters' has no len()

File "/Applications/ChimeraX_Daily.app/Contents/Library/Frameworks/Python.framework/Versions/3.9/lib/python3.9/site-packages/chimerax/core/session.py", line 242, in discovery
if sm is None and len(value) == 0:

However if I switch the displayed stacks as volume, then there is no error on save.

This is with the daily build 1.3.dev202109160803 (2021-09-16) on OSX Big Sur (Intel architecture).

Thanks,

Christophe