@lensmcp/bridge

The build-agnostic browser-event bridge for LensMCP.

A tiny WebSocket server that the injected @lensmcp/client-runtime connects to, forwarding every observed browser event (errors, console, fetch, route changes, and pre-formed React/Valtio publishes) onto the LensMCP event bus — either in-process or, more usually, cross-process over the same LENSMCP_EVENT_FILE / LENSMCP_UDS / LENSMCP_IPC_SOCKET transport the MCP server tails.

This logic used to live inside @lensmcp/vite-plugin, which is why LensMCP only worked for Vite apps. It was lifted out here so the exact same bridge can run:

• embedded in the Vite dev server (the plugin calls createBridgeServer on an ephemeral port), or
• standalone as a sidecar on a fixed port for webpack, Next.js, or no-build hosts — where the browser runtime finds the endpoint by a known URL (ws://127.0.0.1:5747 by default) instead of one a bundler baked in.

Standalone

LENSMCP_EVENT_FILE=.lensmcp/events.jsonl node bridge.js
# or
lensmcp bridge

| Env | Default | Meaning | | --- | --- | --- | | LENSMCP_WS_HOST | 127.0.0.1 | bind host | | LENSMCP_WS_PORT | 5747 | bind port (0 = ephemeral) | | LENSMCP_SESSION_ID | — | session id stamped on each event | | LENSMCP_EVENT_FILE | — | JSONL sink the MCP server ingests |

Point the browser at it with @lensmcp/client-runtime/auto (zero build):

import '@lensmcp/client-runtime/auto';

Embedding

import { createBridgeServer } from '@lensmcp/bridge';

const bridge = await createBridgeServer({ port: 0, bus });
console.log(bridge.port);
await bridge.close();

The bridge is strictly passive: it never mutates app state, never changes scheduling, and never throws into the host.