We present a deterministic framework for discovering, validating, and falsifying structural invariants in decoder transformation pipelines. Rather than optimizing convergence speed or heuristic performance, this work focuses on identifying algebraic and dynamical properties that remain invariant under repeated application of transformation operators. Using a fully deterministic experimental pipeline, we demonstrate that several non-trivial invariants-such as ternary closure, idempotence classes, and dark-state cascade behavior-can be formally proven against the actual implementation. Crucially, we complement positive results with adversarial counterexamples, showing that commonly assumed properties (e.g., universal absorbing states, global idempotence under damping) do not hold in general. This establishes a new methodology for invariant-driven analysis of message-passing systems, shifting emphasis from optimization toward structural understanding and computation elimination.