Litmus MCP Server

The open behavioral litmus harness for MCP servers - grade A–F, reproducible.

People connecting this server to Claude, Cursor, VS Code, or another MCP client. The project is written in TypeScript.

VERIFIED ACTIVE

LAST COMMIT 2026-07-20 · ★ 8 · #286 OF 848 MAINTAINED OTHER · VERIFIED 2026-08-25

Apache-2.0 · TypeScript servers · how we verify → /methodology

01 · Install Litmus

Claude Code

claude mcp add polygraphso-litmus --transport http https://polygraph.so/api/mcp

Claude Desktop / Cursor / VS Code - add to config

{
  "mcpServers": {
    "polygraphso-litmus": {
      "url": "https://polygraph.so/api/mcp"
    }
  }
}

Same JSON for Cursor. For VS Code, rename the top-level key from `mcpServers` to `servers`.

Using another client? Same JSON, different key

Claude Desktop · mcpServers

Cursor · mcpServers

VS Code · servers

Windsurf · mcpServers

Zed · context_servers

Cline · mcpServers

Roo Code · mcpServers

Continue · mcpServers

LibreChat · mcpServers

Gemini CLI · mcpServers

Codex CLI · mcp_servers

Full setup guides: every client.

02 · Evidence

https://polygraph.so/api/mcp

transport: streamable-http

endpoint alive - responded to MCP initialize · probed 2026-08-25

Security posture

What to check before giving this server access to your agent - from the registry, GitHub, and our own probes. We don't score safety; we show what's verifiable.

runs as local process (stdio) - runs on your machine with your user's permissions · remote - your agent's requests go to polygraph.so

endpoint auth accepted our unauthenticated MCP initialize - no credentials needed to connect

license Apache-2.0 - declared in the repository

npm package @polygraphso/litmus - published under the repo owner's npm scope (@polygraphso)

registry namespace io.github.polygraphso is GitHub-verified and matches the repo owner

03 · What Litmus can do

Prose above is summarized from the project's README and registry record - no invented capabilities.

Latest releases

litmus-v0.36.0 · 2026-07-20

Ships the litmus-v17 remote-grading hardening to the published package and the MCP registry. · Honest C-03 on remote targets. A remote (Streamable HTTP) server cannot have canaries planted in its environment, so probe…

litmus-v0.35.0 · 2026-07-18

list_servers is paged: grade / limit (default 25, max 100) / offset inputs, with a full-corpus summary (total plus per-grade counts). Default calls no longer return the full graded list. · The hosted lookup endpoint (…

litmus-v0.34.0 · 2026-07-16

request_grade now surfaces polygraph.so's $1 grading fee: recording a request is free, grading starts on payment (web checkout in $POLYGRAPH, or $1 USDC on Base via x402 for agents), and the grade publishes within 48h…

04 · Who maintains Litmus

litmus is maintained by polygraphso. It's the only MCP server we track from this author; the repo dates to Jun 2026.

05 · Facts

repository: github.com/polygraphso/litmus
website: https://polygraph.so/
category: other - ranked #286 of 848 actively-maintained other servers as of 2026-08-25.
release cadence: 10+ releases in the last 90 days (latest 2026-07-20)
registry: io.github.polygraphso/litmus (active, first published 2026-06-19 · 12 versions)
packages: npm:@polygraphso/litmus

06 · Litmus FAQ

What is Litmus?

The open behavioral litmus harness for MCP servers - grade A–F, reproducible.

Is Litmus still maintained?

Yes - as of 2026-08-25, its last commit was 2026-07-20 and it shipped 10+ releases in the last 90 days. We re-verify nightly.

How do I install Litmus?

Run `npx -y @polygraphso/litmus`. You can also paste the ready-made client config above.

Does Litmus require authentication?

No - the endpoint accepted our unauthenticated MCP initialize when probed on 2026-08-25; you can connect without credentials.

07 · Alternatives to Litmus

Alternatives to Litmus

Maintained other servers if Litmus isn't the fit.

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