PsPLUG uses a "personalization residual" plug-in to curb style-instruction suppression of user preferences, outperforming baselines on LaMP
The work identifies that explicit style instructions can erode the user-specific traits that personalized LLMs aim to preserve (a failure mode it calls personalization collapse), proposes modeling personalization as a distributional residual between the user's true linguistic distribution and the base model's neutral distribution under the same input, and builds PsPLUG: a lightweight plug-in that prepends a 3-token prefix (system instruction vector, user vector, input vector) to a frozen Qwen3-8B backbone, learns the user-specific residual with a style-conditioned Bradley–Terry preference objective, and tunes personalization strength at inference via a scaling coefficient; on the LaMP benchmark, PsPLUG generally outperforms non-personalized, RAG, PAG, PPlug, and OPPU baselines without styl