๐ค AI Summary
Traditional continual learning is constrained by a parameter-centric paradigm, limiting its capacity to meet system-level adaptation demands in dynamic environments. This work proposes a โTri-Axis Frameworkโ (When, How, Where), offering a unified perspective that reorients continual learning beyond mere parameter updates toward external architectures and inference-time adaptation. By integrating off-policy/on-policy learning, test-time training, external memory systems, and skill repositories, the framework transcends the limitations of static parameter spaces and gradient-based optimization. A systematic review elucidates the fieldโs evolutionary trajectory and highlights pivotal challenges and future directions inherent in this paradigm shift.
๐ Abstract
Classical continual learning (CL) has primarily focused on enabling models to update and retain knowledge through parameter-centric mechanisms, e.g., training strategies, architectural designs, and weight adaptation. However, emerging paradigms are reshaping the scope of CL beyond this traditional model adaptation view. For instance, on-policy learning broadens the space of update mechanisms; test-time training extends CL from the training phase to inference; and external harness components such as memory, skill libraries, and interaction protocols extend the evolutionary boundaries of model capabilities far beyond the static parameter space. Collectively, these developments indicate a transition from parameter-centric learning toward system-level adaptation. To characterize this transition, we examine the evolution of continual learning through three dimensions: When, How, and Where learning occurs. The How dimension encompasses off-policy, on-policy, and beyond-gradient optimization mechanics. The When dimension captures evolution across pre-training, post-training, and inference-time stages. The Where dimension delineates updates occurring within internal parameters versus external structural constraints. Anchored by this tri-axial framework, we systematically survey representative methods, trace the ongoing transition of continual learning, and discuss the key challenges, broader implications, and future directions arising from this paradigm shift.