Function approximation_scale 

pub fn approximation_scale(n: usize) -> f64

The upstream wall, measured. The approximation scale of the log-unit collapse at dimension n: the covering radius μ(Λ) against the shortest basis log-length — a proxy for the factor by which a log-unit-decoded generator can exceed the true shortest vector. To threaten Module-LWE this factor would have to stay polynomial; instead it grows super-polynomially with n (asymptotically 2^{Õ(√n)}, Cramer–Ducas–Wesolowski 2017). This is the real wall — not the symmetry-collapse rung (which is cheap, as recovery_margin shows) but the quality of what the collapse can decode as the field grows.