FESADev/.codex/skills/fem-formulation-spec/SKILL.md

name, description

name	description
fem-formulation-spec	Produce an implementation-ready mathematical formulation for a new or changed structural FEM model.

FEM Formulation Specification

Define only the model required by the assigned feature: assumptions, strong/weak form, kinematics, constitutive update, discretization, DOF/component and sign conventions, residual, consistent tangent where applicable, integration, state update, recovery, and formulation-level invariants. Distinguish small/large deformation and analysis-family assumptions.

Use approved requirements and evidence; consult analysis-family guidance when specifying that family's formulation. Make physics-changing choices explicit and return unresolved scope or evidence gaps rather than silently choosing them. Include verification implications, but do not prescribe C++ storage, persistent schema, tolerance values, or reference-result edits.