WBSidecar

A lightweight, generic MCP stdio-to-HTTP bridge. Spawned by an MCP client (e.g. Claude Code, Cursor) as a stdio process; forwards JSON-RPC messages to any MCP-over-HTTP server and streams responses back.

Originally built for Webified Bridge but works with any server that speaks MCP over HTTP.

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Download

Pre-built Windows binary: GitHub Releases

No .NET runtime required — self-contained single-file executable.

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Usage

WBSidecar.exe [--url <endpoint>] [--port <n>] [--token <bearer-token>]

Argument	Default	Description
--url	(see below)	Full endpoint URL — overrides --port
--port	34763	Port for Webified Bridge's default endpoint
--token	(none)	Bearer token sent in Authorization header

When --url is omitted the endpoint defaults to http://127.0.0.1:{port}/wb/mcp.

Webified Bridge (Claude Code config)

{
  "mcpServers": {
    "webified-bridge": {
      "command": "C:\\path\\to\\WBSidecar.exe",
      "args": ["--port", "34763"]
    }
  }
}

Generic MCP-over-HTTP server

{
  "mcpServers": {
    "my-server": {
      "command": "C:\\path\\to\\WBSidecar.exe",
      "args": ["--url", "http://127.0.0.1:8080/mcp"]
    }
  }
}

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Build

Requires .NET 8 SDK.

dotnet publish WBSidecar/WBSidecar.csproj -c Release

Output: WBSidecar/bin/Release/net8.0/win-x64/publish/WBSidecar.exe

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How it works

MCP clients communicate over stdio using the LSP framing format (Content-Length: N\r\n\r\n{json}). WBSidecar reads each message, HTTP POSTs it to the configured endpoint, and writes the response back to stdout in the same framing format.

If the HTTP server is unreachable, WBSidecar returns a structured JSON-RPC error so the client gets a clear failure rather than a silent hang.

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License

MIT — see LICENSE.