Letta

Letta is an open-source platform and cloud service for building stateful AI agents that keep long-term memory, identity and learned skills across sessions and machines. It is aimed at engineering teams building personalised or long-running agents, and removes the need to hand-roll memory, context management and state persistence on top of a stateless LLM API.

Letta is a San Francisco company spun out of UC Berkeley's Sky Lab that builds stateful AI agents: agents with persistent memory, identity and the ability to learn from their own work across sessions. Its founders, Charles Packer (CEO) and Sarah Wooders (CTO), created MemGPT, the research project that introduced self-editing memory for LLMs, and launched Letta in September 2024 with a $10M seed round led by Felicis, with angels including Jeff Dean and Clem Delangue. The product has shifted since. In March 2026 Letta announced a new phase centred on Letta Code, an open-source (Apache-2.0), model-agnostic agent harness with persistent memory, skills, subagents and computer use, and deprecated earlier server-side features such as templates, the Letta Filesystem, server-side MCP integrations and tool rules. Letta Code runs as a CLI, as desktop apps for macOS, Windows and Linux, in the browser, and inside Slack, Telegram, Discord and GitHub Actions, and works with OpenAI, Anthropic and other providers through bring-your-own keys. On August 17, 2026 the company released the Letta Agents SDK, a TypeScript library for embedding long-running stateful agents into custom web, mobile and desktop applications. Agents can live on Letta Cloud, on a self-hosted Letta App Server or on a local backend, and keep the same memory while moving between registered laptops, VMs and containers. Letta lists Bilt, 11x, Kognitos and Hunt Club as customers. It competes with memory layers such as Mem0 and agent frameworks such as LangGraph, and differentiates on transparent, white-box memory that developers can inspect and edit directly.

Category

Agent Development

Pricing

Freemium, Subscription, Usage-based

Target Market

CTOs, Heads of AI, Enterprise Developers, AI Engineers

Deployment

Open-source, Self-hosted, Cloud-first

Founded

2024

Headquarters

San Francisco, USA

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  Persistent white-box memory

  Agents rewrite their own context and memory over time, and developers can inspect every raw LLM request and edit memory directly.

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  Letta Agents SDK (TypeScript)

  Released August 2026, it embeds long-running stateful agents into custom web, mobile and desktop apps over the same WebSocket layer as Letta Desktop.

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  Portable agent state

  The same agent keeps its memory and identity across cloud, self-hosted and local backends and across registered laptops, VMs and containers.

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  Letta Code harness

  Open-source, model-agnostic coding agent with skills, subagents and computer use, which Letta reports ranked first among model-agnostic open-source agents on Terminal-Bench.

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  Multi-channel deployment

  Agents run from the CLI, desktop apps, browser, Slack, Telegram, Discord and GitHub Actions, so one agent can serve several surfaces.

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  Bring-your-own model keys

  Every plan accepts your own OpenAI, Anthropic or other provider API keys, avoiding lock-in to a single model vendor.

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  Personalised customer-facing assistants

  Build assistants that remember each user's history and preferences across sessions instead of starting cold in every conversation.

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  Long-running coding agents

  Run Letta Code agents that accumulate knowledge of a codebase and team conventions, reducing the context re-supplied in every session.

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  Embedding agents in products

  Use the TypeScript Agents SDK to add a stateful agent to a web, mobile or desktop app while keeping its state on Letta Cloud or a self-hosted server.

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  Shared team agents in chat

  Deploy an agent into Slack or Discord that retains organisational context and can be shared with access control on Teams Pro.

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  Private self-hosted agents

  Run the Letta App Server in your own environment when agent memory contains proprietary data that should not sit in a vendor cloud.

Letta publishes list prices: a free tier with limited agents, Pro at $20/month for up to 20 stateful agents, and an API plan at $20/month plus $0.10 per active agent per month and $0.00015 per second of tool execution, with LLM tokens billed pay-as-you-go or through your own provider keys. Teams Pro is $20 per seat per month; RBAC, SAML/OIDC SSO, higher quotas and dedicated support require custom Enterprise pricing. The open-source code is free to self-host.

This page was written from 9 sources, 7 on domains other than letta.com.

1. 1.letta.com — introducing the letta agent sdkvendor
2. 2.letta.com — our next phasevendor
3. 3.docs.letta.com — pricing
4. 4.docs.letta.com — docs.letta.com
5. 5.github.com — letta
6. 6.github.com — letta code
7. 7.prnewswire.com — berkeley ai research lab spinout letta raises 10m seed finan
8. 8.felicis.com — letta
9. 9.news.ycombinator.com — item