The Messenger Incidence Has No Internal Interference Cycle
The complete common-singlet interaction grammar has ten vertices on sixteen field labels. Its signed interaction incidence has exact row rank ten, and its modulo-two left kernel is also zero.
Therefore no nonempty product of coupling phases or signs survives all legal
field rephasings. The common-singlet collapse is structural, not peculiar to
one proposed reference. Every internal sign or phase is presentation data
before the map to physical16.
A progressive successor must add a gauge-legal cycle-closing carrier. Because up- and down-type messengers differ by one unit of hypercharge, such a carrier changes the field, anomaly, threshold, decay, and instrument census.
Evidence: research/flavor/flavor-messenger-incidence-cycle-no-go.md and
research/flavor/results/wp634_messenger_incidence_cycle_no_go.json.