Letta
Open-source agent memory framework — the missing layer for stateful AI agents.
Visit Letta Open source (free), Cloud from $50/mo
What is Letta?
Letta (formerly MemGPT) is the open-source framework for giving AI agents persistent memory across sessions. Critical infrastructure for any agent that needs to remember context beyond a single conversation. Backed by significant Series A funding in 2025.
Key features
- Persistent memory across agent sessions
- Compatible with Claude, GPT, open models
- Open source (Apache 2.0)
- Cloud-hosted option
- Hierarchical memory architecture
Pros
- Solves a real problem agent builders hit
- Genuinely open source
- Active research community
Cons
- Developer-only — no consumer UI
- Setup complexity is non-trivial
- Niche use case unless you build agents
Best for
Developers building production AI agentsResearchers experimenting with memoryEnterprises needing stateful AI workflows
