Towards In-Parameter Memory Augmentation for Large Language Models

Recently Large Language Models (LLMs) and LLM-based agents increasingly need to incorporate knowledge acquired after pretraining, e.g., domain facts, user preferences, documents, and interaction experience. In-context learning (ICL) and ICL-based agent harness remain flexible, but they consume context capacity and incur repeated discretized encoding cost that grows with context length. $\mathbf{\text{In-parameter}}\mathbf{\text{memory}}$ offers a complementary substrate: reusable memory information is represented in model parameters, adapters, or other parameter-like objects that are composed into the forward pass at inference time. This survey focuses on methods that augment LLMs with such parametric memory at deployment: a memory-bearing parameter object is plugged into the forward pass during inference, whether it is acquired before or during deployment. We organize the landscape with two orthogonal axes: $\mathbf{\text{Parameter}}\mathbf{\text{Placement}}$, which includes Embedding, Attention, FFN layers, or Hybrid when two or more layers are used; and $\mathbf{\text{Parameter}}\mathbf{\text{Acquisition}}\mathbf{\text{Time}}$, which distinguishes methods whose memory object is acquired during deployment (online) from those acquired before it (offline). We clarify boundaries, conduct comparisons, and discuss open directions in interference, safety, co-design with ICL, and recursive self-improvement.