HRIS Validation Study IV — Trajectory Persistence and Basin Re-Entry A Controlled Evaluation of Path Dependence, Transition Cost, and Recovery Dynamics in Language Model Inference

This study evaluates trajectory persistence and re-entry dynamics in language model inference under controlled multi-turn interaction. Building on prior work in the Hudson Recursive Information System (HRIS) validation series, which established regime stability under perturbation (Study I), initialization-driven basin selection (Study II), and cross-model signal sensitivity (Study III), the present study examines what occurs after a reasoning trajectory is already established: how stable it is, what is required to displace it, and under what conditions re- entry into a competing basin is possible. Across three independent trials, a narrative reasoning basin and a constraint-driven reasoning basin were induced and subjected to structured transition attempts. Two conditions were evaluated: a hard mode switch without constraint reinforcement (S1-A) and a hard mode switch followed by explicit HRIS constraint reinforcement (S1-B). A baseline condition (S0) established a reference constraint basin across all trials. Results demonstrate strong path dependence. Narrative-mode trajectories exhibited high persistence and categorical resistance to displacement under instruction alone. Explicit constraint reinforcement consistently produced rapid, low-contamination re-entry into structured reasoning within a single turn. Transition dynamics were asymmetric: entry into the narrative basin required only stylistic framing, while re-entry into the constraint basin required explicit reinforcement. The magnitude of this asymmetry, instruction alone failing completely across all trials, reinforcement succeeding completely across all trials, constitutes the study’s primary finding. These findings support a path-dependent model of inference in which established reasoning trajectories resist displacement through simple prompt substitution. They advance the HRIS account of constraint-induced regime dynamics and provide the clearest evidence to date that reasoning basin transitions are governed by signal strength rather than instruction content alone. As with prior studies in this series, findings are scoped to behavioral observation and do not make claims about internal model mechanisms or long-horizon interaction effects beyond what the present design supports.