Three Families of Memory Methods

knowledge-organizationstructure what the model has thought or noted retrieval-mechanism-orientedan external library and a recall rule architecture-drivenchange the control flow that reads and writes TiM Think-in-Memory · Liu et al. 2023 raw turnsnot kept post-think LLM reflectsafter answering thought "user runs to get fit" this is whatgets stored bucket 1 bucket 2 ← thought bucket 3 LSH recall similar thoughts hash to one bucket; a query reads the bucket it lands in memory ops on thoughts · insert · merge · forget stores reasoning outcomes, not raw turnsrecall by LSH over stored thoughtsmemory ops · insert, forget, merge focus · storage structure A-Mem Agentic Memory · Xu et al. 2025 earlier sessions new session notekw · tags · ctxnotekw · tags · ctxnotekw · tags · ctx updated ✎ links new note kw · tags · ctx LLM writes it memory evolution a new note is linked to related notes and may rewrite their context and tags LLM writes a structured note per turnlinks it into a knowledge networkold notes evolve when new ones arrive focus · storage structure MemoryBank Zhong et al. 2024 vector DB · entries daily conversation logevent summariesuser portrait · traits each entry · embedding + time memory strength recalled → restored time Ebbinghaus forgetting curve recall · query embedding vs entries; weak entries fade out, recalled ones are refreshed logs conversations, events, user traitsstrength decays on an Ebbinghaus curverefreshed on recall · portrait grows focus · retrieval mechanism MemGPT Packer et al. 2023 LLM main context · the fixed window system prompt · recent messages · working set page out page in LLM calls external context · outside the window recall storage (past messages) · archival storage the model itself decides when to read and write two contexts in an OS-like hierarchyexplicit read / write calls page datapast the fixed window focus · control flow
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