Debian control files support custom fields prefixed with X and one or more of S, B, or according to the following rules: X: Signifies a user-defined field. S: Indicates the field should be included in the source package control file (.dsc). B: Indicates the field should be included in the binary package control file. C: Indicates the field should be included in the changes file (.changes) used for uploads. When the package is built, the XSBC- prefix is stripped, and the field is placed into the designated output files under its base name (e.g., XSBC-Custom-Field becomes Custom-Field). In Debcraft, this mechanism should replace the passthrough method to create custom entries in the control file. Since dsc or changes are not yet supported, it should only propagate the field to the binary package control file.