Letta, formerly MemGPT, is an open source platform for agents that keep memory over time. You can run it yourself or use the hosted service.
Letta's docs list a personal Free plan at $0 per month, limited to 3 stateful agents, and Pro at $20 per month. Last checked 16 Oct 2026.
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Three other agent frameworks tools listed in this directory.
Agent frameworks
Agent-Native is an open source TypeScript framework for building agents that share actions with a user interface. You define a capability once, and the agent, the app, and other clients call the same code.
Agent frameworks
Dify is an open source platform for building AI apps and agents with a visual editor. You can self-host it or use Dify Cloud.
Agent frameworks
Flowise is an open source visual builder for model workflows. You connect nodes for models, tools, and data, then call the result from an API.