Direct Regular Charts and Certified Stationarity at a Singular Lorentzian Simplicial Background

We construct and validate a direct regular source chart for two stationary branches at a singular background of a fixed boundary-capped Lorentzian simplicial action. The source retains nine four-simplices, eighteen independently varied Lorentz links, moving boundary returns, and all 114 stationary equations. A regular bordered solve defines the normal section directly from the original action, and a nonzero-parameter chart and controlled amplitude translation identify the incoming roots. A constraint-matched second predictor determines the correct zero-bottom bordered coefficient and cancels the off-shell linear action error. Complete differentiation of the averaged changing border yields a coefficient-subtracted quadratic remainder and all state-Jacobian bounds. A fixed two-branch contraction certifies [2^-120, 2^-118], with actual inclusion on [2^-120, 2^-119] and normalized error below 2.896689e-12. The outgoing estimate does not import the previous complete tail, although that tail remains in the incoming bootstrap and source premises remain inherited. The larger regular and analytic domains are not stationary-root intervals; the finite sections near t=1/64 remain unconnected. Two separate AI-session reviews examined the linked research and frozen manuscript at stated conditional scopes; this is not external human peer review. Accepted returned Lean evidence covers 131 supporting theorem declarations and 47 definitions, not end-to-end source formalization. Numerical and formal supplements preserve exact records, available histories, source bindings and reproducible selected workflows. Public log views distinguish redacted path metadata from original checksums. Licensing: CC BY 4.0 for author-owned manuscript/documentation/data; MIT for author-owned software, as detailed in the supplement rights maps.