Letta (formerly MemGPT)
Long-term memory primitive: hierarchical context with explicit recall calls.
Letta exposes a memory primitive built around hierarchical context with explicit recall and edit operations.
Strengths. Best-in-class for explicit, inspectable memory state.
Weaknesses. Requires changes to the agent loop; not a drop-in.
Use it when you need durable memory across sessions and want to audit what the agent remembers.