4th species cadence — the final bar suspends the syncopation pattern

In 4th species (syncopated) counterpoint, the cadence cannot be reached while preserving the tied-over syncopation figure, because the standard cadential suspension-and-resolution requires the CP's last note to land on the downbeat rather than tied in from the previous bar. Standard practice therefore breaks the syncopation in the final bar (sometimes the second-to-last), presenting the cadential figure as plain note-against-note so the piece can close cleanly — a deliberate, universally-taught EXCEPTION to 'every bar of 4th species is syncopated,' not a lapse in discipline.

A 4th-species exercise either forces the tie-over pattern through the final bar (producing an unresolvable/awkward cadence), or breaks the syncopation 2+ bars before the end with no structural reason (an unintentional lapse, not the licensed exception).

Fux (Gradus ad Parnassum) via Jeppesen's Counterpoint, standard treatment of the 4th-species cadence.

This rule can be decided from pitches, durations and voices — no layout required. A validator can check it before anything is drawn.