Discovery, Validation and Editing of Large Language Models Mechanisms: Recent Advances and Future Perspectives

Abstract

Large language models (LLMs) have demonstrated remarkable capabilities across a wide range of tasks, yet their internal mechanisms remain largely opaque, making it difficult to understand, predict, or control their behavior. As LLMs are increasingly deployed in high-stakes settings, this lack of transparency raises serious concerns about reliability and safety. Mechanistic interpretability (MI) has emerged as a promising approach to address this challenge, seeking to reverse-engineer the internal computations of LLMs into human-understandable mechanisms, i.e., an approximate high-level algorithm that the LLM implements with a subset of its components (a circuit) to complete a certain language task or exhibit a certain behavior. This tutorial provides a comprehensive and up-to-date overview of LLM mechanism discovery, validation, and editing. We begin by introducing foundational concepts, including features, components, computational graphs, and circuits, along with key notation. We then examine mechanism discovery through four methodological families: causal mediation, attribution, sparse decomposition, and optimization-based approaches. Next, we turn to mechanism validation, covering methods for verifying proposed mechanisms and emerging standards for rigorous evaluation. Building on these foundations, we survey mechanistic editing techniques that leverage MI insights to modify behavior at varying granularity, from fine-grained representation-level steering to coarser circuit-level interventions. Lastly, we outline open challenges and future research directions, including scalability of interpretability methods, evaluation benchmarks for mechanistic circuits, and the integration of interpretability with training-time objectives, aiming to inspire continued progress in understanding and governing large language models.