Hi, I am trying to minimize an AF3-generated protein–RNA complex [1, attached] in ChimeraX [2,3] , but the minimization fails with the following error: `KeyError: 'RNA-o'` The traceback points to OpenMM while creating the system (`forcefield.createSystem()`). I assume AF3 uses standard nomenclature for atoms and residues, so I was wondering whether this is a known issue with the force field used by ChimeraX for minimization, or if there is a way to work around it. I am aware of the limitations of ChimeraX minimization and am only using it as a quick check before (eventually) proceeding with more rigorous refinement. Thank you for any suggestions. Best regards, -- Bruno Hay Mele, PhD https://github.com/bhym/ [1] metrics (pae/plddt/iptm) are very good [2] just plain minimize #1 [3] Daily build of couple days ago (UCSF ChimeraX version: 1.13.dev202607062345 (2026-07-06) )