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, and janus_login.

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-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 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.