A First-Repair Mass Zero Without Angular-Moment Cancellation

For each fixed outgoing source Profile, every sufficiently small positive parameter admits a point strictly inside the first repair window where the mass history vanishes while the angular-weighted history remains strictly positive at the same point. The proof compares the weighted future tails of two separated repair bumps. This version also derives a strictly positive angular-history margin independent of the chosen mass-zero witness, and a normalized cutoff-plateau lower bound. The paper provides definitions, proofs, Lean 4 declaration correspondence and fixed compilation checkpoints. The qualitative and quantitative runs have separate identities; neither is presented as an independently reproduced experiment. The result concerns a specified construction and a prospective ratio denominator, without asserting uniqueness, a pole or a general Navier–Stokes solution. Author: Yun Kwansub. Version 0.5, 31 October 2026. Paper and source: CC BY 4.0. Supporting software and Lean files: MIT. Software archive: https://doi.org/10.5281/zenodo.23381778. Repository: https://github.com/flamehaven01/NavierStokes-Research-Workbench. Companion research-software case study: https://doi.org/10.5281/zenodo.23835112.