Janusmcp

JanusMCP

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

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[](https://janusmcp.dev)

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One-click buttons require the npm package to be published. See RELEASING.md.

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](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:

| Command | What it does | |---|---| | janusmcp serve | Run the broker (default). Transports via env: JANUS_TRANSPORT=stdio\|http\|both, JANUS_HTTP_HOST, JANUS_HTTP_PORT. | | janusmcp ui | Open the local control panel — add accounts, log in, set secrets. | | janusmcp add [id] | Add an account from a template (janusmcp catalog lists them). | | janusmcp catalog | List the built-in account templates. | | janusmcp connect | Connect an account; for remote OAuth, opens the browser. | | janusmcp status | Show each account's login/secret status (no secret values). | | janusmcp vault set / delete | Store / remove a secret in the OS keychain. | | janusmcp login | OAuth loopback login; token referenced as oauth:. | | janusmcp providers | List built-in OAuth providers. | | janusmcp install | Configure an LLM client to launch JanusMCP. | | janusmcp uninstall | Remove JanusMCP from an LLM client's config. | | janusmcp version · janusmcp help | Version · this reference. |

Supported ` 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, and janus_login.

Key features

| | | |---|---| | Multi-account, one endpoint | N identities for the same service, no reconnecting | | Identity scoping | per-call → per-session (Mcp-Session-Id) → global, via bindingMode: global \| session \| locked | | Dual transport | stdio (local-first clients) + Streamable HTTP (remote-first clients), same process | | Secure vault | OS keychain (macOS/Windows/Linux) + encrypted-file fallback; secrets as vault: | | OAuth loopback | janusmcp login (PKCE), tokens stored in the vault, auto-refresh, oauth: | | Context-safe | only the active account's tools are exposed; switching emits tools/list_changed |

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.

Status & roadmap

Alpha — the core is implemented and tested in Go.

• [x] Active-account model, per-session / global / locked scoping
• [x] stdio + Streamable HTTP transports
• [x] OS-keychain vault + encrypted-file fallback
• [x] OAuth loopback (PKCE) with auto-refresh and per-spawn token resolution
• [x] 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-client 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](design-broker-mcp-multi-account.md) for the full design.

Repository layout

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

Contributing

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

License

MIT — see [LICENSE](LICENSE).

Source & license

This open-source MCP server is cataloged on AgentStack and links to its original source — we do not rehost the code.

• Author: Bayway
• Source: Bayway/janusmcp
• License: MIT

Install and usage instructions live in the source repository linked above.