Letta
Free tierAn AI research lab building self-improving agents that remember everything and learn continuously.
Free tier available·All audiences·API available·Open source
Key strengths
Stateful agents with persistent memoryContinual learning and self-improvementOpen-source (Apache 2.0)Self-hostableGit-based memory versioningSleep-time compute / background reasoningMulti-channel integrations (Slack, Discord, WhatsApp, etc.)
Free tier + paid plans
San Francisco, USA
Founded 2023
Self-hostable
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Documentation & Developer Resources
Letta provides developer-facing resources oriented around its open-source codebase and API-first design.
What's available:
- Open-source repository — Apache 2.0 licensed, with 25,000+ GitHub stars; the repo serves as the primary reference for self-hosted deployments and contribution
- REST API — a documented API layer for managing agents, reading and writing memory, and handling multi-session state programmatically
- Self-hosting support — full self-hostable deployment path for teams and enterprises that require on-premises or private-cloud operation
- Protocol support — MCP and ACP integration documentation for connecting agents into broader multi-agent or tool-use pipelines
- BYOK configuration — documentation for connecting your own LLM API keys (available on the Free plan)
- Integration guides — connectors for Slack, Telegram, Discord, WhatsApp, Signal, GitHub, Claude, ChatGPT, and Cursor
Pricing-relevant notes for developers:
- Free tier: 3–5 stateful agents, 5 MiB storage, BYOK
- API Plan ($20/mo): unlimited agents, usage-based billing — suited for production API workloads
- Enterprise: custom pricing with dedicated support
Alternatives
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