Reason Gate MCP Server
A self-hostable gate that inspects the text going into and out of an LLM and returns an explainable allow / flag / block decision with a machine-readable audit record for every call. It runs locally over stdio via the published package.
People who work with ai safety, guardrails and jailbreak detection and want it reachable from Claude, Cursor, VS Code, or another MCP client. The project is written in Python.
VERIFIED ACTIVE
LAST COMMIT 2026-09-18 · ★ 14 · #167 OF 204 MAINTAINED SECURITY · VERIFIED 2026-09-18
Apache-2.0 · Python servers · how we verify → /methodology
01 · Install Reason Gate
before you install - you'll need
The README does not document required environment variables for a basic install.
Claude Code
claude mcp add cgrtml-reasongate -- uvx reasongateClaude Desktop / Cursor / VS Code - add to config
{
"mcpServers": {
"cgrtml-reasongate": {
"command": "uvx",
"args": [
"reasongate"
]
}
}
}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
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
license Apache-2.0 - declared in the repository
pypi package reasongate - check the name against the project README before installing (PyPI has no namespace ownership)
registry namespace io.github.cgrtml is GitHub-verified and matches the repo owner
03 · What Reason Gate can do
Prose above is summarized from the project's README and registry record - no invented capabilities.
Latest releases
v0.6.1 · 2026-09-17
reasongate is now a second name for the reasongate-mcp gateway so MCP clients can start it as uvx reasongate -- <server command>; server.json for the official MCP Registry (io.github.cgrtml/reasongate). See CHANGELOG.md.
v0.6.0 · 2026-09-17
pip install reasongate now installs reasongate-mcp: the action gate as a stdio MCP · gateway, so it runs where the tool calls actually happen. · bash · claude mcp add docs -- reasongate-mcp -- npx -y…
v0.5.0 · 2026-09-15
Everything in this release was measured before it was kept, on the same 609 AgentDojo · pairs, and the numbers are in RESULTS.md next to the ones they replace. · The gate, six steps · | Step | Change | Utility, clean |…
04 · Who maintains Reason Gate
ReasonGate is maintained by cgrtml. It's the only MCP server we track from this author; the repo dates to May 2026.
05 · Facts
- repository
- github.com/cgrtml/reasongate
- category
- security - ranked #167 of 204 actively-maintained security servers as of 2026-09-18.
- release cadence
- 5 releases in the last 90 days (latest 2026-09-17)
- registry
- io.github.cgrtml/reasongate (active, first published 2026-09-17)
- packages
- pypi:reasongate
06 · Reason Gate FAQ
What is Reason Gate?
A self-hostable gate that inspects the text going into and out of an LLM and returns an explainable allow / flag / block decision with a machine-readable audit record for every call. It runs locally over stdio via the published package.
Is Reason Gate still maintained?
Yes - as of 2026-09-18, its last commit was 2026-09-18 and it shipped 5 releases in the last 90 days. We re-verify nightly.
How do I install Reason Gate?
Run `uvx reasongate`. The README does not document required environment variables for a basic install. You can also paste the ready-made client config above.
Does Reason Gate run locally?
Yes - it's a stdio server: it runs on your machine (via uvx) with your user's permissions. Your data stays local unless the server itself calls external APIs.
07 · Alternatives to Reason Gate
Alternatives to Reason Gate
Maintained security servers if Reason Gate isn't the fit.
- Treg To OpenRouter for tools and data. Compare catalog providers and call them from one hosted MCP endpoint. ★ 1,627 · 2026-09-18
- SafeDep Vet MCP Protect your AI agents and IDEs from malicious open-source packages. ★ 1,105 · 2026-09-16
- SonarQube MCP Server Analyze code quality and security with SonarQube Server or Cloud directly in AI assistants. ★ 652 · 2026-09-17
- HOL Guard Local-first AI agent security evidence and approval workflows through HOL Guard's stdio MCP server. ★ 625 · 2026-09-18
- Decionis CommerceGate MCP Commerce preflights, D365 authorization, signed evidence, and reports; no marketplace or ERP writes. ★ 533 · 2026-09-18
- Emisar Let AI operate servers without SSH. Choose actions, approve risky changes, and audit every step. ★ 353 · 2026-09-15
Pairs well with
Servers that cover what Reason Gate doesn't - only shown when the pairing reason fits the companion.