Initial conditions: properties.initial_conditions takes source and constraints alone. mode, generator, params, field, source_file and the built-in zero, constant, streamwise_constant and poiseuille are refused, each naming its replacement: an expression source, source: {generator, params}, or source: {type: file, field, path}. Existing cases must be edited. The solver's -finit, -ucont_*, -flow_direction and -ic_velocity_physical options are gone.