We present Stage Σ of the Criterion C2 relativistic consistency program: a rigid, fixed–baseline closure diagnostic of the Weyl (gravitational lensing) sector using real Dark Energy Survey Year 3 (DES Y3) MagLim weak–lensing two–point statistics. All background cosmological parameters and DES nuisance parameters are held fixed to the official DES Y3 baseline best–fit values. The Weyl sector is then probed through a single global amplitude deformation Σ applied to a baseline theory vector in the known DES Y3 MagLim data–vector ordering (with the appropriate powers for each two–point type). Over broad scale ranges, this intentionally restrictive one–parameter closure hypothesis provides a statistically unacceptable description of the data. We interpret this outcome as evidence that the rigid, frozen–baseline closure ansatz is insufficient for the DES Y3 lensing two–point products under the present construction (e.g. residual scale/tomography structure not captured by a single amplitude), rather than as evidence for modified gravity. Accordingly, the main deliverable is a fully reproducible, audit–ready closure framework and a clear diagnostic baseline for subsequent iterations (controlled scale cuts, alternative validated template extraction, and systematic–stress tests) required before any cross–sector C2 statement becomes physically meaningful.

This record contains the manuscript and supporting data for Stage Σ of the Criterion C2 relativistic consistency program. The study performs an internal closure test of the Weyl (gravitational lensing) sector using the official Dark Energy Survey Year 3 (DES Y3) MagLim weak-lensing two-point statistics. By fixing background cosmological parameters to the DES Y3 baseline, this work isolates the lensing sector through an intentionally rigid amplitude deformation (Σ). The results indicate that the current lensing sector fails to close internally under this rigid hypothesis, pointing toward residual scale-dependent modeling systematics rather than modified gravity. Stage Σ serves as a reproducible diagnostic baseline and a foundational building block for direct consistency tests between growth and lensing sectors.

The manuscript emphasizes reproducibility and auditability. It is accompanied by a verified artifact bundle containing the exact data vectors, covariance matrices, theory templates, scripts, numerical outputs, and a SHA256 manifest, allowing full independent reproduction of all results. The bundle includes extensive numerical stability tests, scale-cut robustness checks, covariance stress tests, and failure-localization diagnostics documented in detail.

Version 2 — Forensic audit revision This release adds formal robustness diagnostics and editorial clarifications to the Stage Σ Weyl-sector closure test. The numerical results are unchanged; the update strengthens reproducibility and interpretation framing. New material includes scale-cut analysis, covariance stress tests, and refined discussion of closure failure as a rigid-ansatz diagnostic rather than a modified-gravity claim.

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