Hey, I think that's basically a duplicate of HV-726. As suggested by George, we are considering in that issue to derive the target from the composing constraints in case of purely composed constraints. An alternative suggested by Emmanuel was to allow the supported target to be given via @SupportedValidationTarget on the composing constraint definition in the case of a purely composed constraint.

As a workaround, you could just implement a no-op validator which always returns true from isValid() and annotate this validator with{{@SupportedValidationTarget}} to specify the supported target. The actual validation would still happen via the composing constraints in this case.