@spocapp/mcp-bridge

Small stdio bridge that lets Claude Desktop, Cursor, Zed, Windsurf and other stdio-only MCP clients talk to the SPOC MCP server at spoc.com/mcp/rpc.

• npm: @spocapp/mcp-bridge

• MCP Registry: io.github.SPOC-App/mcp-bridge

• Live server: https://spoc.com/mcp/rpc — reports itself as spoc / 1.27.0

What this is (and isn't)

Most current MCP clients only speak the stdio transport — JSON-RPC over a subprocess's stdin/stdout. SPOC's MCP server speaks HTTP+SSE so it can serve many clients at once. This bridge is the shim between the two: install it, point your MCP client at it, and SPOC's tools appear in the client's tool picker.

It is not a rewrite of the MCP protocol, and it doesn't cache, batch, or reinterpret requests. Every JSON-RPC frame goes through unchanged. If you need behaviour that differs from what the bridge does today, it's usually easier to fix in SPOC itself than in the shim.

Related MCP server: MCP Stdio to SSE Proxy

Install

You don't need to install it — most MCP clients will fetch it on demand with npx:

npx -y @spocapp/mcp-bridge

Or install it once and point clients at the binary:

npm install -g @spocapp/mcp-bridge
which spoc-mcp-bridge

Configure your MCP client

Claude Desktop

Edit the config file:

• macOS: ~/Library/Application Support/Claude/claude_desktop_config.json

• Windows: %APPDATA%\Claude\claude_desktop_config.json

{
  "mcpServers": {
    "spoc": {
      "command": "npx",
      "args": ["-y", "@spocapp/mcp-bridge"],
      "env": {
        "SPOC_BEARER": "spk_live_..."
      }
    }
  }
}

Restart Claude Desktop. SPOC's tools should appear in the tool picker within a few seconds.

Cursor

~/.cursor/mcp.json (or Settings → MCP → Edit mcp.json):

{
  "mcpServers": {
    "spoc": {
      "command": "npx",
      "args": ["-y", "@spocapp/mcp-bridge"],
      "env": { "SPOC_BEARER": "spk_live_..." }
    }
  }
}

Zed

~/.config/zed/settings.json:

{
  "context_servers": {
    "spoc": {
      "command": {
        "path": "npx",
        "args": ["-y", "@spocapp/mcp-bridge"],
        "env": { "SPOC_BEARER": "spk_live_..." }
      }
    }
  }
}

Windsurf, Continue, etc.

Any client that speaks the MCP stdio transport works the same way. Set the command to npx -y @spocapp/mcp-bridge and pass a bearer via environment.

Environment variables

Bearer tokens

Generate one at https://spoc.com/settings/api-keys. Make sure the harness:issue scope is checked or SPOC will reject calls that need to issue harnesses.

Anonymous access works for read-only tools that don't need a principal. Bearer is only required for tools that act on behalf of an identity.

Smoke test

Confirm the bridge and the upstream are both healthy:

npx -y @spocapp/mcp-bridge <<< '{"jsonrpc":"2.0","id":1,"method":"initialize","params":{"protocolVersion":"2024-11-05","capabilities":{},"clientInfo":{"name":"smoke","version":"0"}}}'

You should get a single JSON line back that includes "name":"spoc" and "version":"1.27.0". If you see that, MCP-aware clients will work.

Troubleshooting

Tools don't appear in the client after restart. Run the smoke test above in a plain terminal. If it returns an error frame, the error.data field will tell you why. If it returns nothing at all, check the client's log for a spawn error — the usual cause is npx not being on the client's PATH.

ERR_INTERNAL on tool calls. Almost always an upstream issue rather than a bridge issue. Set SPOC_DEBUG=1 and re-run — the bridge will log the raw upstream response.

401 errors. The bearer token is missing, wrong, or lacks scope. Verify at https://spoc.com/settings/api-keys.

SSE won't connect. Notifications are optional. Set SPOC_DISABLE_SSE=1 and everything except server-initiated notifications continues to work.

Testing

npm ci
npm run build
npm test        # unit + client-integration suites (offline, no network)

The client-integration suite spawns spoc-mcp-bridge as a real subprocess and drives it through the same stdio protocol that Claude Desktop, Cursor, Zed, and Windsurf use — initialize, notifications/initialized, tools/list, tools/call, concurrent in-flight calls, mixed-type ids, SSE notifications, upstream errors, and timeouts. If it passes, MCP clients that speak stdio will work.

To also exercise the real production endpoint:

SPOC_LIVE_TEST=1 npm test                              # anonymous only
SPOC_LIVE_TEST=1 SPOC_BEARER=spk_live_... npm test     # + tools/call

CI runs the offline suite on Node 18 / 20 / 22 for every push and PR; the live suite runs on main only.

Writing your own client

If you're implementing SPOC's report-event HMAC signing directly (rather than going through this bridge), one thing to watch out for: SPOC's canonical form matches JavaScript JSON.stringify behaviour, which leaves non-ASCII characters as themselves rather than escaping them to \uXXXX. Python's default json.dumps(...) escapes non-ASCII — you'll get a bad_signature 401 the first time you include an em-dash, curly quote, or accented character. Pass ensure_ascii=False.

Links

• https://spoc.com — the underlying service

• https://spoc.com/mcp/manifest — the tool catalogue

• https://spoc.com/docs/api — the full HTTP API

• CHANGELOG.md — release history and what changed between versions

• RELEASING.md — how to cut a new release

License

MIT