# Multi-Browser MCP Proxies — Arc Browser & Chrome Beta Variants

> Companion to 'CDP WebSocket 代理' for running parallel, isolated MCP fleets against Arc Browser and Chrome Beta on top of the same cdp-proxy.mjs. Portable $HOME paths + install steps included. Arc proxy auto-discovers the WebSocket path from /json/version; Chrome Beta proxy points at Beta's own DevToolsActivePort. Lets you run mcp__chrome__*, mcp__beta__*, and mcp__arc__* side-by-side with independent client state and no cross-talk.

## Install

Merge the JSON below into your `.mcp.json`:

# Multi-Browser MCP Proxies — Arc & Chrome Beta

Companion bundle to the **CDP WebSocket Proxy** (cdp-proxy.mjs,
https://tokrepo.com/en/workflows/cdp-websocket-agent-e0f83e28). Same
`cdp-proxy.mjs` backbone, repointed at Arc Browser and Chrome Beta so you can
run independent, isolated MCP fleets for each browser without losing focus
protection or popup suppression.

## Why a separate proxy per browser

- **Independent login state** — your work Chrome stays untouched while Arc
  drives experiments, or vice versa.
- **Independent debug ports** — Arc and Chrome Beta both write their own
  `DevToolsActivePort` files; the proxy reads each browser's file via
  `--devtools-port-file`.
- **No cross-talk** — each proxy has its own `clientState`, `sessionOwners`,
  and `pendingRequests` map. A Chrome Beta sub-agent can't accidentally
  hijack Arc tabs.

## Files

| File | Default ports | Reads DevToolsActivePort from |
|------|---------------|-------------------------------|
| `arc-mcp-proxy.sh` | proxy `9501` → Arc `9223` | `~/chrome-profiles/arc-DevToolsActivePort` (auto-built from `/json/version` on each launch) |
| `chrome-beta-mcp-proxy.sh` | proxy `9402` → Chrome Beta `9222` | `~/Library/Application Support/Google Chrome Beta/DevToolsActivePort` |

Both wrap the same `cdp-proxy.mjs`.

## Install

```bash
mkdir -p "$HOME/scripts" "$HOME/chrome-profiles/pids" "$HOME/chrome-profiles/logs"
# 1. save arc-mcp-proxy.sh / chrome-beta-mcp-proxy.sh (this bundle) into ~/scripts/
# 2. get cdp-proxy.mjs from https://tokrepo.com/en/workflows/cdp-websocket-agent-e0f83e28
#    and save it as ~/scripts/cdp-proxy.mjs
chmod +x "$HOME/scripts/arc-mcp-proxy.sh" "$HOME/scripts/chrome-beta-mcp-proxy.sh"
npm install ws --prefix "$HOME/scripts"   # cdp-proxy.mjs dependency
```

All scripts use `$HOME`-relative paths — no editing needed.

## Arc setup

Arc doesn't write `DevToolsActivePort` to a standard location. Launch it with
an explicit debug port and the proxy script will discover the WebSocket path
on its own:

```bash
open -a "Arc" --args --remote-debugging-port=9223
bash ~/scripts/arc-mcp-proxy.sh   # proxy :9501 → Arc :9223
```

`.mcp.json` (note: `.mcp.json` does not expand `~`, hence the `bash -c` form):

```json
"arc": {
  "command": "bash",
  "args": ["-c", "exec \"$HOME/scripts/arc-mcp-proxy.sh\" 9501 9223"]
}
```

## Chrome Beta setup

Chrome Beta writes its own `DevToolsActivePort` file under
`~/Library/Application Support/Google Chrome Beta/`. Once Beta is running with
remote debugging enabled (`chrome://inspect/#remote-debugging` → Allow), the
proxy auto-discovers it.

```json
"beta": {
  "command": "bash",
  "args": ["-c", "exec \"$HOME/scripts/chrome-beta-mcp-proxy.sh\" 9402 9222"]
}
```

## Running all three side by side

```
Claude Code window A → mcp__chrome__*  → :9401 → Chrome stable :9222
Claude Code window B → mcp__beta__*    → :9402 → Chrome Beta   :9222
Claude Code window C → mcp__arc__*     → :9501 → Arc           :9223
```

Three independent proxies, three independent browsers, three sets of MCP
tool namespaces. They never collide.

(The stable-Chrome proxy on `:9401` is `chrome-mcp-proxy.sh`,
https://tokrepo.com/en/workflows/chrome-mcp-85bd27cc)

## Caveat — don't kill cross-session

Heuristics like "kill 9401/9402 because they're not LISTEN" will tear down a
sibling session's MCP. Always check `lsof -nP -p <pid>` for live stdio before
killing anything. See the **Chrome MCP 完整运维指南**
(https://tokrepo.com/en/workflows/chrome-mcp-d5db19b8) for the full cleanup
protocol.


---
Source: https://tokrepo.com/en/workflows/multi-browser-mcp-proxies-arc-browser-chrome-beta-variants-deaee53e
Author: henuwangkai