mcp-rtc

Browser tab as MCP server. Peer-to-peer over WebRTC.

What this is

Existing MCP transports (stdio, Streamable HTTP) cover local processes and public-URL backends. They don't cover an MCP server that lives in a browser tab — exposing the device's camera, screen, files, paired BLE or Serial — to a local Claude. WebRTC's NAT-traversing data channel does. This repo is the spec, the reference transport, and a browser-side bridge.

Architecture

        Browser tab                                  Local MCP client
   ┌──────────────────┐                          ┌──────────────────┐
   │   MCP server     │ ◄── MCP JSON-RPC ──────► │  Claude Code     │
   │                  │     WebRTC data channel  │  Cursor          │
   │ camera · GPS     │     DTLS, NAT-traversing │  Claude.ai (ext) │
   │ screen · files   │                          │  Claude Desktop  │
   │ BT · serial      │                          │                  │
   └──────────────────┘                          └──────────────────┘

Initial handshake: peers find each other via a shared site id, exchange SDP/ICE through a WebSocket lobby. No public URL on either side. Three layers, independently pluggable:

Layer	Role	Spec	Reference
1 — Transport	MCP JSON-RPC over WebRTC data channel	mandated	@nevescloud/mcp-rtc
2 — Signaling	rendezvous, SDP / ICE exchange	recommended	@nevescloud/pip-relay
3 — Identity	peer authentication	recommended	TOFU via signed pair-request

Implementations interoperate at Layer 1 even when Layer 2 / 3 differ. Full text in SPEC.md.

Try it

Two URLs, one Claude.

1. neves.cloud/h/ — the tab becomes an MCP server. Eleven capabilities (camera, GPS, screen share, files, BT, serial, …) register as tools; permissions stay lazy. Note the #hi-XXXXXX it generates.

2. Reach it from a local Claude:

   From Claude Code (or any stdio MCP client) — install the bridge once:

   claude mcp add mcp-rtc-bridge -- npx -y @nevescloud/mcp-rtc-bridge

   Then paste the "Paste in Claude Code" prompt the host page generates.

   From Claude.ai / Desktop — open neves.cloud/b/#hi-XXXXXX in Chrome 146+ with a WebMCP consumer (e.g. the Anthropic Claude extension). Tools surface in the local tab; Claude calls them natively over WebMCP.

Two machines work the same way. /h/ and /b/ are the deployed pages; docs/examples/hello-tool/ is the minimal forkable example.

Repo

packages/transport/    @nevescloud/mcp-rtc             transport reference impl
packages/bridge-tab/   @nevescloud/mcp-rtc-bridge-tab  WebMCP ↔ mcp-rtc browser adapter
packages/bridge/       @nevescloud/mcp-rtc-bridge      stdio MCP server → mcp-rtc
docs/examples/         hello-tool: minimal working example
SPEC.md                wire-format contract (draft 0.1)

Status

Substrate published. Capability host (/h/) live with eleven capabilities → fifteen MCP tools across heartbeat, sensors, screen share, file pickers, paired BLE / Serial. Path B (terminal Claude via stdio bridge) and Path A (in-browser open-weights inference via @nevescloud/pip + LFM2.5-350M) both working. Next: fragment-driven host/consumer role + QR, marketing landings, confer's canvas.html migration onto bridge-tab. Standardization (SEP / W3C-CG / informal RFC) intentionally uncommitted — the library and the capability host are what people use; the spec catches up if a standardization moment arrives.

License

MIT