LLM Personas Exhibit Regime-Dependent Behavior, Challenging Individuation

A recent ontological framework for the LLM individuation problem assumes that a persona vector consistently refers to the same content, regardless of whether it's activated through prompt-conditioning, gradient-descent fine-tuning, or inference-time steering. This paper presents empirical evidence that challenges this fundamental assumption. Through a series of persona-topology experiments conducted on Qwen3-4B-Instruct and Mistral-7B-Instruct-v0.2, researchers uncovered several "wedges." These include non-collinearity between prompt-extracted vectors and fine-tune basins, fictional personas having a stronger displacement effect than real anchors, contradictory-valenced mixtures being biased towards training history, and asymmetric compositional algebra under different operational regimes. These findings collectively undermine the idea of a single, stable persona identity. The paper proposes a "regime-indexed individuation" framework, suggesting that the identity unit for representational content should be considered a (vehicle, regime) pair, not just the vehicle itself. This implies that existing theories about LLM personas might be describing different regime-internal objects rather than competing for the same referent.