Abstract We predict a Discontinuous Loss of Interference at a fixed Critical Mass (M_c ≈ 2.2 × 10-14 kg), incompatible with any standard environmental decoherence or Continuous Spontaneous Localization (CSL) model. This "Topological Phase Step" is the unique signature of discrete spacetime saturation and acts as the singular falsification criterion for the entire unified framework. Project Overview The Tamesis Theory is a structurally closed proposal for a Theory of Everything (ToE) based on 5 irreducible geometric axioms. It derives the electron mass, fine structure constant, and Schrödinger equation from first principles of holographic thermodynamics. This upload includes: TheTamesisTheory...pdf: The consolidated scientific paper. paper.html: The interactive web-based report. TAMESIS_COMPLETE.rar: The full research archive containing: 01_Foundation_ToE: Holographic framework and derivation engines. 02_Research_Limits: M_c limit derivation. 03_System_Closure: Python simulations for the Spectral Operator, Axiom Validation, and the "Killer" Interference Prediction. Key Predictions: Topological Step: Abrupt collapse of wavefunction at M_c. Spectral Hierarchy: Particle masses follow values of the Tamesis Spectral Operator. Death Criteria: Explicit falsification conditions provided.