Show HN: Fentaris, an open-source proxy for managing multiple MCP servers

Fentaris launched as an open-source proxy and control plane for managing multiple Model Context Protocol (MCP) servers behind a single stable endpoint, unifying stdio, Streamable HTTP, SSE, and HTTP upstream MCP servers. The project ships three packages — @fentaris/core, @fentaris/cli, and @fentaris/approval-telegram — and supports API keys, bearer tokens, custom headers, and OAuth 2.1 for authenticating clients and upstream servers, with the CLI generating a proxy that listens on http://localhost:4000/mcp by default. Fentaris targets teams that want MCP servers to behave like production infrastructure, with namespaced tool names, policy-based access control, manual approval for risky actions, and structured logging of every proxied operation.

Table of contents Fentaris is a control plane for your MCP servers — one place to run, route, and manage every MCP server behind a single, stable endpoint. - Unify stdio, Streamable HTTP, SSE, and HTTP upstream MCP servers behind one proxy. - Manage which servers and tools are exposed, to whom, and how they behave — without touching client configs. - Observe every proxied operation with structured logging, lifecycle events, and per-request context. - Protect tool calls, resources, prompts, and completions with policy, identity, middleware, hooks, and rate limits. - Authenticate clients and upstream MCP servers with API keys, bearer tokens, custom headers, and OAuth 2.1. Fentaris is designed for teams that want MCP servers to behave like production infrastructure: stable names, centralized management, auditable calls, and predictable client-facing endpoints. Visit our docs https://fentaris.mintlify.app or jump to a quickstart https://fentaris.mintlify.app/getting-started/quickstart Using Claude Code, Codex, Cursor or other AI coding agents? For a complete runnable project with API-key users, groups, allow-list policy, a remote MCP upstream, and app-owned local tools, see examples/team-governed-proxy https://github.com/Fentaris/fentaris/blob/main/examples/team-governed-proxy . Use the CLI to start a new Fentaris proxy project: npm install -g @fentaris/cli fentaris init my-proxy cd my-proxy fentaris dev The generated proxy listens on http://localhost:4000/mcp by default. Point your MCP client to that endpoint. Under the hood, a Fentaris proxy is just a few lines of code: js import { approval, fentaris, oauth, policy, stdio, streamableHttp, user, } from "@fentaris/core"; const app = fentaris ; app.mcp "filesystem", { transport: stdio { command: "npx", args: "-y", "@modelcontextprotocol/server-filesystem", "/tmp" , } , } ; await app.start ; Upstream tool names stay stable and namespaced by server, no matter how many servers you add. A filesystem tool is exposed to clients with a proxy name such as: filesystem list directory Add another server behind the same endpoint: app.mcp "github", { transport: stdio { command: "npx", args: "-y", "@modelcontextprotocol/server-github" } , } ; Restrict who can call what: app.policy "read-only" .mcp "filesystem" .allow "list directory" ; app.group "operators" .users user "alice", { email: "alice@example.com" } .policy "read-only" ; Require approval before a risky action runs: js const deploy = policy "deploy" .mcp "github" .allow "deploy production", approval.manual { reason: "Production deploy requires approval", } ; Observe every tool call: js app.on "tool:success", { ctx, durationMs } = { ctx.log.info "tool.success", { tool: ctx.tool?.name, durationMs } ; } ; Runtime routes can deny, approve, hide, log, or transform calls to any tool, resource, prompt, or completion. Authenticate clients with an API key, and let Fentaris handle OAuth 2.1 for upstream servers automatically: fentaris auth api-key add alice --generate app.mcp "linear", { transport: streamableHttp { url: "https://mcp.linear.app/mcp" } , auth: oauth , } ; Credential values are never exposed to middleware, hooks, logs, or policy callbacks. | Package | Description | |---|---| | @fentaris/core https://github.com/Fentaris/fentaris/blob/main/packages/core | Proxy runtime, MCP server wrapper, transports, policy, auth, logging, and middleware APIs. | | @fentaris/cli https://github.com/Fentaris/fentaris/blob/main/packages/cli | Project generator and local development commands. | | @fentaris/approval-telegram https://github.com/Fentaris/fentaris/blob/main/packages/approval-telegram | Telegram approval adapter for Fentaris policies. | Run the project for development: fentaris dev From a clean clone, install the locked dependency graph and run the same validation used by CI: pnpm install --frozen-lockfile pnpm verify pnpm verify runs lint, typecheck, build, and every package test in that order. Before promoting a release, verify the exact npm tarballs in clean projects: pnpm verify:release This packs Core, CLI, Edge, and Telegram approval, validates their manifests and entrypoints, installs them in an empty project, generates and builds a real CLI project, and exercises upgrade, downgrade, reinstall, and re-upgrade from the previous published package set. It requires access to the npm registry. Generate docs reference: pnpm docs:generate MIT https://github.com/Fentaris/fentaris/blob/main/LICENSE.txt , as declared by the published Fentaris packages.