An Independent Reproduction and Four Extensions of the MUB(6) Fourth-Vector Feasibility Wall

Title. An Independent Reproduction and Four Extensions of the MUB(6) Fourth-Vector Feasibility Wall Abstract. We present a companion note that cites N. Erlwein’s exact fourth-vector feasibility wall for a canonical mutually unbiased product triple in dimension six (Zenodo 20682233; theorem W = (88 + 3√6)/100). We do not redistribute the upstream software bundle. Independently, we (A) maintain a pure-Rust exact verification surface; (B) raise a d=10 closed-form hunt to a 460-decimal-place stationarity anchor with a widened PSLQ menu (no relation found); (C) run a full Cl(2)×Cl(5) single-qudit Clifford census at d=10, finding a single antiunitary Z/2 real structure; and (D) issue exact rational finite-cover exclusion certificates on a specified cell of the gauge-fixed candidate 5-torus. MUB(6)=3 and MUB(10) remain open. Local certificates mint no authority. Why a researcher should care. The note strengthens a rare exact, machine-checkable obstruction artifact in d=6 quantum information with a second language (Rust), higher-precision d=10 evidence, and independently checkable finite covers—while keeping claim boundaries explicit. What this does not claim. Not MUB(6)=3; not MUB(10); not a closed form at d=10; not joint authorship of Erlwein’s wall; not a global moduli theorem. Reproduction. cd crate && cargo test -j 1cargo run --release --bin mub_cover -- --region quadrant DOI. Pending human mint. Upstream wall: 10.5281/zenodo.20682233.