Function mtp_multi_seq_mode 

pub fn mtp_multi_seq_mode() -> bool

True when the MTP cap is raised above one sequence. The catchup ring (types.rs mtp_catchup_ring + meta), the refeed label convention, and the carry slot (mtp_carry.rs) are SINGLE-SEQUENCE structures — one ring, one label range, one slot. Running them with n concurrently-verifying sequences interleaves unrelated hiddens under one label space and breaks after_verify’s env-keyed trim contract (mtp_rows_to_trim). Disabling them process-wide when the cap > 1 is the only consistent option; a slot-keyed ring is recorded follow-up work (acceptance debt at n>1).