Decision procedures can be either theory-specific, e.g., Presburger arithmetic, or theory-generic, applying to an infinite number of user-definable theories. Variant satisfiability is a theory-generic procedure for quantifier-free satisfiability in the initial algebra of an ordersorted equational theory pΣ, E Y Bq under two conditions: (i) E Y B has the finite variant property and B has a finitary unification algorithm; and (ii) pΣ, E Y Bq protects a constructor subtheory pΩ, EΩ Y BΩq that is OS-compact. These conditions apply to many user-definable theories, but have a main limitation: they apply well to data structures, but often do not hold for user-definable predicates on such data structures. We present a theory-generic satisfiability decision procedure, and a prototype implementation, extending variant-based satisfiability to initial algebras with user-definable predicates under fairly general conditions. Keywords: finite variant property (FVP), OS-compactness, user-definable predicates, decidable validity and satisfiability in initial algebras.