io.github.libtmux.query.FilterExpr.FilterExpr.negate

and and or below are deliberately *overloads* of the inherited Predicate methods rather than overrides: their parameter is a FilterExpr, so combining two expressions stays an expression, while passing a bare lambda selects the inherited method and yields a plain predicate. That is the intended boundary — a lambda cannot be printed or serialized, so an expression built from one must not claim to be inspectable.