Function within_m16_tc_budget 

pub fn within_m16_tc_budget(
    actual_bits: u16,
    reference_bits: u16,
    k: usize,
    row_rms: f64,
) -> bool

The tier’s numerics contract, as ONE predicate every oracle and host simulation evaluates, so they cannot drift.

An element passes if EITHER it is within M16_TC_MAX_ULP ordinal BF16 ULP of the reference, OR its absolute error is under m16_tc_acc_floor for the reduction depth k and the reference ROW’s RMS.

k is the reduction depth the kernel actually ran, not the output width — passing n here would make the floor grow with the vocabulary, which is the one axis it must not depend on.