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Hermes Desktop vs Letta: catalog facts
Hermes Desktop	Letta
Free Free and open source under the MIT licence.	Freemium The agent installs from npm; the homepage does not detail pricing.
Windows, macOS, Linux	Command line
Keeps memory across sessions Writes and improves its own skills	Persistent memory that carries over between sessions Installs with a single npm command
Linux has no installer package and installs through the terminal Autonomous agents need care with the access they are given	Homepage gives few details on pricing or licensing Aimed at developers comfortable with the command line
Downloadable app	Downloadable app
Open source	Closed source
License: MIT	License not stated
Not stated if an account is needed	Not stated if an account is needed
Not stated if it works offline	Not stated if it works offline
Official website Full listing and sources Checked October 1, 2026	Official website Full listing and sources Checked September 26, 2026

Catalog facts only. Anything “not stated” is unconfirmed. Check full listings for details.