head to head · open source
langchain vs Letta
langchain has 146,538 GitHub stars, 24,504 forks, 492 open issues and last shipped yesterday. Letta has 3,366 stars, 411 forks, 347 open issues and last shipped yesterday. langchain leads on adoption by 4,253% (146,538 vs 3,366 stars). langchain is written in Python under MIT; Letta is written in TypeScript under Apache-2.0. langchain has attracted 17% as many forks as stars, Letta 12%. langchain was the more recently maintained of the two, and both are self-hostable with no licence fee. The two share 1 topic tag (ai), so they are genuine substitutes rather than adjacent tools.
Two open source projects, one decision. Both are free and self-hostable — the differences are community size, license terms, language stack and release pace.
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Side by side
| langchain | Letta | |
|---|---|---|
| GitHub stars | ★ 147K | ★ 3.4K |
| License | MIT | Apache-2.0 |
| Written in | Python | TypeScript |
| Last push | 2026-09-17 | 2026-09-17 |
| Forks | ⑂ 25K | ⑂ 411 |
| Self-hosting | Yes | Yes |
| Data ownership | Your server | Your server |
pick langchain if
- You weight community size — 147K stars and counting
- You want the MIT license terms
- Your stack matches Python
- You value the larger contributor base for long-term maintenance
pick Letta if
- You want the Letta feature set and don't need the biggest community
- You prefer the Apache-2.0 license terms
- Your stack matches TypeScript
- You evaluated both and Letta fits your workflow better
About langchain
LangChain is an open source framework for building agents and LLM powered applications, written in Python and released under the MIT license. It lives in the AI and machine learning ecosystem, specifically among AI development platforms, and it works by chaining together interoperable components and third party integrations so that AI application development becomes simpler. The project describes itself as the agent engineering platform, and its abstractions are designed to keep applications working as the underlying technology evolves.
read the full langchain overview →
About Letta
Letta Code is an open source TypeScript harness under Apache 2.0 for stateful AI agents. It lives in the AI & Machine Learning / AI Development Platforms ecosystem. It gives agents memory, identity, and a sense of experience over time. It targets agents that behave more like people than tools.
read the full Letta overview →
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Frequently asked questions
Is langchain or Letta more popular?
langchain has 146,538 GitHub stars and Letta has 3,366. langchain has the larger community by that measure.
Are langchain and Letta free?
Both are open source. langchain is licensed under MIT and Letta under Apache-2.0. Neither carries a licence fee.
What is the difference between langchain and Letta?
langchain is written in Python and Letta in TypeScript. The practical differences are community size, licence terms, language stack and release cadence — all compared in the table above.
Which should I choose, langchain or Letta?
Choose langchain if you want the larger community (146,538 stars) or its MIT licence terms. Choose Letta if its feature set, stack or Apache-2.0 licence fits better. Both are self-hostable.