55  Known Limitations

• OPALX is not documented as a drop-in implementation of every historical OPAL flavor. OPAL-CYCL and OPAL-MAP material is not part of this manual.
• Registered but regression-untested interfaces are identified as source-supported; that label does not claim regression coverage.
• Some physics chapters document recently implemented models whose interface may still change; these pages are marked experimental.
• Backend support must be checked for each new algorithm; successful serial execution does not establish GPU support.
• Hard-edge fields and active elements shorter than a few integration steps can create numerical splitting. Always check time-step convergence.
• The experimental COF command solves static, fixed-energy, four-dimensional ring closure. It does not provide RF/6D closure, space-charge matching, or automatic integer-tune and plane assignment. A converged orbit does not establish stability.
• COF-to-TRACK handover requires a fresh generated beam with completed emission. TRACK closure needs its own timestep study because its integration and return plane can differ from COF’s. Explicit TURNS currently excludes space charge and RF.

These limitations are documentation status, not a substitute for the issue tracker. Report unexpected implemented behavior with a reproducible case.