The Memory Hierarchy of an Agent
Cognitive science spent a century mapping human memory into distinct systems — working, episodic, semantic, procedural — and agent engineering has been rediscovering the same partition from the opposite direction, because the same pressures produce the same shapes. The hierarchy isn't biomimicry for its own sake: each memory type answers a different question, is stored differently, retrieved differently, and fails differently. Confusing them is the root of most memory-system design mistakes.
Agent memory decomposes into four types with different jobs: working (the context window), episodic (what happened — read as history), semantic (what is true — needs revision, not just insertion), and procedural (how to act — evolves like code). They differ in storage, retrieval, and lifecycle, and most memory bugs are type confusions.