lema-mcp

Your coding agent can read the code. It can't read the argument behind it. lema-mcp gives your agent the recorded why — and the alternatives a project already ruled out — cited to the source. For React, Kubernetes, and Rust out of the box, and for your own repo with one command.

A local MCP server. No account, no database, no network for your own repo — install it in 30 seconds and ask why a project decided something, or whether the approach you're about to take was already rejected.

❌ Without lema

• The agent invents the why from training recall — fluently, and sometimes wrongly. The rationale lives in RFC / KEP / PR threads; it was never in the code.
• It re-proposes the approach the maintainers already rejected two years ago — because a rejected alternative leaves no trace in the source.
• Ask "was this ever ruled out?" and you get a confident guess, with no way to tell a real ruling from a hallucinated one.

✅ With lema

• One cited answer from the project's actual recorded deliberation — every [n] links to the RFC / PR where the call was made.
• A typed ruled_out verdict when a project already rejected your approach, with the recorded reason and a pointer to where the docs say to do it instead.
• A typed settled verdict when your approach is the project's in-force recorded choice — the governing decision cited, with a docs pointer for the how.
• An honest "no recorded ruling" when the record is silent — which means unknown, not approved. lema never fills the gap with a guess.

lema holds reasoning — why a decision was made, what was rejected — not API syntax or code samples. For those, reach for a docs tool. lema is the right place for why.

Try it in 30 seconds — no account

npx lema-mcp try react        # or: kubernetes · rust

That writes a read-only public server to your project's .mcp.json. Reload your agent's MCP servers (in Claude Code: /mcp) and try the flagship tool, check_approach — name a direction, get the recorded verdict:

> "Let's add a delayMs prop to Suspense to debounce the fallback."   (repo: react)

  ⛔ ruled_out — the React team considered and rejected this.
     "<the recorded rationale, summarized — not a quote>"  [1]
     Where to look instead →  https://react.dev/reference/react
     [1] reactjs/rfcs#212

> "I'll add a global event bus for cross-component communication."   (repo: react)

  ◦ no_recorded_ruling — React's public record doesn't settle this.
     (Unknown — not approved.)

Or just ask in plain language — "why did React adopt Hooks over mixins?" — and get one cited answer, with an honest abstain when the record is silent.

Covered today: React · Kubernetes · Rust, served from lema's public API (api.lema.sh). Tokenless. It's a curated three-project demo corpus — not analytics over a graph you own.

Install

No-account public demo (React's recorded decisions, zero setup):

  [](https://vscode.dev/redirect?url=vscode%3Amcp%2Finstall%3F%257B%2522name%2522%253A%2522lema%2522%252C%2522command%2522%253A%2522npx%2522%252C%2522args%2522%253A%255B%2522-y%2522%252C%2522lema-mcp%2540latest%2522%255D%252C%2522env%2522%253A%257B%2522LEMA_MCP_MODE%252

... View full README on GitHub