Both are open source harness options with comparable terms, so the choice comes down to which model of the problem you prefer — compare the descriptions below rather than the licence.
Self-improving agent from Nous Research — writes its own skills from experience and carries them forward.
The learning loop is the point: it creates skills after complex tasks and searches its own past sessions. Runs anywhere from a $5 VPS to Modal or Vercel Sandbox.
Stateful agent server where memory is the primary abstraction.
| Hermes Agent | Letta | |
|---|---|---|
| Licence | Open source | Open source |
| Pricing | open source | freemium |
| Self-hostable | Yes | Yes |
| Languages | Any language | Python, TypeScript |
| Install | curl -fsSL https://hermes-agent.nousresearch.com/install.sh | bash | pip install letta |
| Keys required | None | None |
Both are open source harness options with comparable terms, so the choice comes down to which model of the problem you prefer — compare the descriptions below rather than the licence. Hermes Agent: Self-improving agent from Nous Research — writes its own skills from experience and carries them forward. Letta: Stateful agent server where memory is the primary abstraction.
Hermes Agent can run on your own infrastructure. Letta can run on your own infrastructure.
Hermes Agent is open source (open source). Letta is open source (freemium).
Every page here answers to Accept: text/markdown and returns the same content at roughly a tenth the tokens. No separate site, no toggle — same URL.
curl -s -H "Accept: text/markdown" https://newagent.build/compare/hermes-agent-vs-letta