Mem0
Open-source persistent memory layer that gives AI agents the ability to remember users, preferences, and context across sessions. Supports vector, graph, and key-value storage backends. AWS partner for Strands Agents. YC W23, $24M raised, 30K+ GitHub stars.
Graphiti
OSS temporal knowledge graph engine purpose-built for AI agents. The engine underneath Zep, also usable standalone. Tracks facts and their validity over time so agents can reason about state changes, not just current truth.