A Non-Linear Action-Limit Model for Stochastic Gravitational Wave-Function Collapse

We present a non-linear action-limit model (NALM) that resolves the conflict between macroscopic gravitational geometry and microscopic quantum superpositions. By establishing a fundamental phase-action threshold of ħ/2, the spacetime substrate exerts a reactive back-pressure that triggers objective, norm-preserving wave-function localization via an Itô stochastic noise drive. The model incorporates a spatial correlation cutoff σ_cut ≈ 100 nm to suppress unphysical thermal heating in deep classical states below 10^-17 J/s/kg, strictly satisfying Gran Sasso and IGEX experimental bounds. We further demonstrate that the non-linear noise drive acts on instantaneous boundary conditions at detection, naturally resolving Wheeler's delayed-choice paradox without retrocausality.