Lemma
Lemma is an open-source MCP server that gives AI assistants persistent memory across sessions: memories are injected automatically, strengthen with use and fade when unused.
Open npm ↗Live · v0.20.0
What it does
- Injects relevant memories into every session automatically, without the model having to call a tool first.
- Lets frequently used knowledge strengthen and unused knowledge fade, and promotes recurring patterns into reusable skills.
- Records approaches that were tried and rejected, and recalls those dead ends at the start of a new session so the same failed path is not explored twice.
- Runs a background layer that detects conflicts between memories, suggests actions and links related knowledge.
- Ships a library view (lemma -lib) and an interactive memory graph in the browser (lemma -vis).
How it works
- Lemma is a Model Context Protocol server distributed on npm as lemma-mcp and started by the MCP client with npx. It needs Node.js 20 or newer.
- Configuration is a single entry in the client’s MCP settings; the README documents Claude Desktop, Claude Code and opencode.
Who it is for
Developers who use AI coding assistants daily and are tired of re-explaining the same project context every session.
Limits
- It is a local MCP server: it works with MCP-compatible clients, not with chat products that do not support MCP.
Built with
- TypeScript
- MCP
- Node.js
Sources
Last checked · Published by OWL APP LTD