This repository isolates the final obstruction in the Yang–Mills mass gap problem: construction of an Osterwalder–Schrader positive Euclidean measure.

All classical and semiclassical analytic inputs (coercivity, Kato/FLIC control, HS-gap refutation) are assumed verified upstream. Assumed inputs (verified upstream):

• Uniform Jacobi coercivity modulo gauge (Kato/FLIC).
• Semiclassical stability.
• HS-gap line certified negative (no use here).

Status: OPEN — external, non-perturbative obstruction.