Cylinder collision, bit non-reuse and effective non-degeneracy in the 2-adic Collatz dynamics

This paper proves the effective non-degeneracy conjecture formulated in the author’s previous study on the 2-adic structure of the compressed Collatz dynamics 10.5281/zenodo.18685581. It establishes that the restricted survival sets inside a fixed modular class decrease exactly by a factor of one half at each step. The proof relies on the precise cylindrical structure of the 2-adic valuation levels, the affine behavior of the dynamics within each branch, and a structural separation argument based on cumulative 2-adic depth. It is shown that distinct itineraries cannot collide at any finite resolution, ensuring injectivity of the correspondence between admissible trajectories and initial residues. As a consequence, the infinite survival set has Haar measure zero. The question of its emptiness, which is equivalent to the classical Collatz conjecture in the principal modular class, remains open.