JanusMCP

One MCP endpoint, every account. Add your credentials once, switch identity without reconnecting — from any LLM.

_{One-click buttons require the npm package to be published. See <a href="RELEASING.md">RELEASING.md</a>.}

The problem

If you work with more than one company, you use the same MCP server (Supabase, GitHub, Slack…) with different identities — a different account, email and token per client. Today most LLM clients hold one account at a time per connector: to switch client you disconnect, reconnect, and redo the OAuth login. Every time.

The MCP protocol has no notion of "account": one session = one identity = one set of credentials. JanusMCP fills that gap.

What it does

JanusMCP is a local broker that sits between your LLM client and the real MCP servers:

• Add N accounts once for the same service and keep them all available.
• Switch identity without reconnecting — no re-login, no fiddling with config.
• Works with any LLM client — it just speaks standard MCP (stdio + Streamable HTTP).
• Runs locally — your machine, your keychain, your control.
• Keeps the context clean — it exposes only the active account's tools, not N×tools.

                 ┌─────────────────────────────┐   ┌─ Supabase (Client A)
LLM client ─MCP─▶│   JanusMCP broker           │─▶ ├─ Supabase (Client B)
(Claude/GPT/     │   active-account · vault ·  │   ├─ GitHub  (Client A)
 Gemini/…)       │   per-session scoping       │   └─ …
                 └─────────────────────────────┘

You drive it with three control tools that appear in any client: janus_list_accounts, janus_use_account, janus_whoami.

Install

Once released, install via your favorite channel (all published automatically on each tag — see RELEASING.md):

npx @bayway/janusmcp serve                                   # npm (works inside MCP/npx setups)
brew install bayway/janusmcp/janusmcp     # Homebrew (macOS/Linux)
scoop install janusmcp                               # Windows
docker run --rm -p 7332:7332 ghcr.io/bayway/janusmcp:latest

…or download a prebuilt binary from Releases.

Build from source (60-second quickstart)

git clone https://github.com/bayway/janusmcp
cd janusmcp/go
make build                       # produces ./bin/janusmcp
cp config.example.json config.json   # edit with your accounts
./bin/janusmcp serve             # stdio, for Claude Desktop/Code

Two Supabase clients, PATs kept in your OS keychain (never in the config):

./bin/janusmcp vault set supabase_client_a   # paste the PAT
./bin/janusmcp vault set supabase_client_b

// config.json
{
  "bindingMode": "session",
  "accounts": [
    { "id": "client_a", "service": "supabase", "command": "npx",
      "args": ["-y", "@supabase/mcp-server-supabase@latest", "--read-only", "--project-ref=REF_A"],
      "env": { "SUPABASE_ACCESS_TOKEN": "vault:supabase_client_a" } },
    { "id": "client_b", "service": "supabase", "command": "npx",
      "args": ["-y", "@supabase/mcp-server-supabase@latest", "--read-only", "--project-ref=REF_B"],
      "env": { "SUPABASE_ACCESS_TOKEN": "vault:supabase_client_b" } }
  ]
}

Add it to Claude Desktop:

{ "mcpServers": { "janusmcp": {
  "command": "/abs/path/janusmcp/go/bin/janusmcp", "args": ["serve"],
  "env": { "JANUS_CONFIG": "/abs/path/janusmcp/go/config.json" } } } }

For ChatGPT / Gemini / Cursor / Copilot, run HTTP and point them at the URL:

JANUS_TRANSPORT=http JANUS_HTTP_PORT=7332 ./bin/janusmcp serve
# → http://127.0.0.1:7332/mcp

Commands

Run janusmcp help for the full reference. The essentials:

Supported <client> values for install / uninstall: claude-desktop, claude-code, cursor, vscode, gemini, codex, chatgpt, print. Run janusmcp install list (or uninstall list) to see each target and whether it's already configured.

janusmcp install claude-desktop      # one-command setup
janusmcp uninstall claude-desktop    # clean removal (restart the client afterwards)

Inside any connected client you also get the control tools janus_list_accounts, janus_use_account, janus_whoami, janus_login, janus_use_profile, and janus_with_account.

Profiles — a whole client's stack at once

A profile groups accounts of the same client across different services. Activating it exposes the tools of all its accounts together, and each call is routed to the right upstream:

// config.json
{
  "accounts": [
    { "id": "supabase_a", "service": "supabase", "transport": "http", "url": "https://mcp.supabase.com/mcp", "auth": "oauth" },
    { "id": "github_a",   "service": "github",   "transport": "http", "url": "https://api.githubcopilot.com/mcp/", "auth": "oauth" }
  ],
  "profiles": {
    "client_a": ["supabase_a", "github_a"]
  }
}

Then in chat: janus_use_profile with { "profile": "client_a" } → Supabase and GitHub tools for Client A are available simultaneously. Colliding tool names across accounts are namespaced (<account>_<tool>).

One-shot cross-account calls

janus_with_account runs a single call on another account without changing the active one — e.g. { "account_id": "client_b", "tool": "list_tables" }. Omit tool to list that account's available tools first.

Key features

How it's different

The MCP gateway space (MetaMCP, mcp-proxy, IBM ContextForge, …) aggregates different servers behind one endpoint. JanusMCP solves the orthogonal, under-served problem: many identities for the same service, without saturating the model's context, from any LLM, fully local. It's a credential-aware broker, not a flat aggregator.

Provider notes

Figma

Figma offers two MCP servers, handled differently here:

• Local Dev Mode server (recommended). Figma's desktop app hosts an MCP server on http://127.0.0.1:3845/mcp. It's local, needs no OAuth, and works out of the box: enable it in the desktop app (Dev Mode → Inspect → Enable desktop MCP server) and add it with janusmcp add figma-desktop figma_work. Requires a Dev/Full seat on a paid Figma plan.

• Remote server (https://mcp.figma.com/mcp) — restricted. Figma allowlists the OAuth client_name during dynamic client registration and returns 403 Forbidden to any client that isn't in its MCP catalog (VS Code, Cursor, Claude Code, …). JanusMCP is not (yet) an approved client.

  ⚠️ Workaround — opt-in, use at your own risk. You can make JanusMCP register under an approved name by setting "clientName": "Claude Code" on a remote figma account in your config.json. This impersonates an approved client and may violate Figma's Terms of Service; it can also break whenever Figma updates its allowlist. It is not enabled by default. Prefer the local Dev Mode server above for real work.

  The proper long-term fix is for JanusMCP to be submitted to and approved for Figma's MCP catalog, so no client_name override is needed. This is planned.

Status & roadmap

Alpha — the core is implemented and tested in Go.

• Active-account model, per-session / global / locked scoping
• stdio + Streamable HTTP transports
• OS-keychain vault + encrypted-file fallback
• OAuth loopback (PKCE) with auto-refresh and per-spawn token resolution
• One-command client install (janusmcp install …), Claude Desktop .mcpb, registry server.json
• Multi-server "profiles" per client (Supabase + GitHub + Slack of Client A at once)
• with_account one-shot cross-account calls
• CLI / code-execution mode — invoke tools on demand via a CLI instead of loading all tool definitions, to cut token usage (à la "code execution with MCP")
• SSE upstream transport (in addition to Streamable HTTP + stdio) for SSE-only servers
• Signed, per-OS release binaries & registry auto-publish in CI

See design-broker-mcp-multi-account.md for the full design.

Repository layout

• go/ — the broker (Go). This is the real implementation. Build & docs →
• spike/ — the original TypeScript spike, kept as a verified reference of behavior.
• design-broker-mcp-multi-account.md — architecture & rationale.

Privacy Policy

JanusMCP runs entirely on your machine. It has no backend servers, collects no data, and contains no analytics or telemetry — the developers receive nothing about you or your usage. Credentials and tokens are stored in your OS keychain (or, if you opt in, an encrypted local file) and are used only to authenticate to the services you configure; they never pass through the model context. Network connections are made only to the MCP servers and OAuth providers you configure. Because everything is local, data is retained only on your own device for as long as you keep it, and removing it (janusmcp vault delete <name>, or uninstalling) removes it entirely.

Full policy: https://janusmcp.dev/privacy.

Contributing

Contributions are very welcome — see CONTRIBUTING.md. New connector presets, client integration guides, and packaging help are especially appreciated.

License

MIT — see LICENSE.