Multi-Browser MCP Proxies — Arc & Chrome Beta

Companion bundle to Chrome MCP Background Proxy. 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

Both wrap the same cdp-proxy.mjs from the parent bundle (Chrome MCP Background Proxy). Drop that file into ~/scripts/ first.

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:

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

.mcp.json:

"arc": {
  "command": "bash",
  "args": ["/Users/<you>/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.

"beta": {
  "command": "bash",
  "args": ["/Users/<you>/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.

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 Operations Runbook skill for the full cleanup protocol.

#!/bin/bash

Arc MCP + 持久 Proxy

用法: arc-mcp-proxy.sh [proxy端口] [arc调试端口]

复用 cdp-proxy.mjs，但连接 Arc 浏览器（固定端口 9223）

Arc 需要用 open -a "Arc" --args --remote-debugging-port=9223 启动

PROXY_PORT=${1:-9501} ARC_DEBUG_PORT=${2:-9223} PROXY_SCRIPT="/Users/wangkai/scripts/cdp-proxy.mjs" PID_DIR="/Users/wangkai/chrome-profiles/pids" LOG_DIR="/Users/wangkai/chrome-profiles/logs" ARC_DEVTOOLS_PORT_FILE="/Users/wangkai/chrome-profiles/arc-DevToolsActivePort"

mkdir -p "$PID_DIR" "$LOG_DIR"

本地连接绕过代理

unset http_proxy HTTP_PROXY https_proxy HTTPS_PROXY all_proxy ALL_PROXY export no_proxy="127.0.0.1,localhost" export NO_PROXY="127.0.0.1,localhost"

从 Arc 调试端口的 /json/version 获取 wsPath，写入 DevToolsActivePort 格式文件

WS_URL=$(curl -s --noproxy '*' "http://127.0.0.1:${ARC_DEBUG_PORT}/json/version" 2>/dev/null
| python3 -c "import sys,json; print(json.load(sys.stdin)['webSocketDebuggerUrl'])" 2>/dev/null)

if [ -n "$WS_URL" ]; then # 从 ws://127.0.0.1:9223/devtools/browser/xxx 中提取路径部分 WS_PATH=$(echo "$WS_URL" | sed 's|ws://[^/]*||') printf '%s\n%s\n' "${ARC_DEBUG_PORT}" "${WS_PATH}" > "${ARC_DEVTOOLS_PORT_FILE}" fi

如果 Proxy 没跑，启动它（持久运行，不随 Claude Code 退出而死）

if ! lsof -i :${PROXY_PORT} >/dev/null 2>&1; then nohup node "${PROXY_SCRIPT}"
--port ${PROXY_PORT}
--chrome-port ${ARC_DEBUG_PORT}
--devtools-port-file "${ARC_DEVTOOLS_PORT_FILE}"
&>"${LOG_DIR}/proxy-${PROXY_PORT}.log" & echo $! > "${PID_DIR}/proxy-${PROXY_PORT}.pid" disown sleep 2 fi

启动 chrome-devtools-mcp，连接到 Proxy

exec npx -y chrome-devtools-mcp@latest --browserUrl "http://127.0.0.1:${PROXY_PORT}"

#!/bin/bash

Chrome Beta MCP + 持久 Proxy

用法: chrome-beta-mcp-proxy.sh [proxy端口] [chrome端口]

与普通 Chrome proxy 完全独立，互不干扰

PROXY_PORT=${1:-9402} CHROME_PORT=${2:-9222} PROXY_SCRIPT="/Users/wangkai/scripts/cdp-proxy.mjs" PID_DIR="/Users/wangkai/chrome-profiles/pids" LOG_DIR="/Users/wangkai/chrome-profiles/logs" DEVTOOLS_PORT_FILE="$HOME/Library/Application Support/Google/Chrome Beta/DevToolsActivePort"

mkdir -p "$PID_DIR" "$LOG_DIR"

本地连接绕过代理

unset http_proxy HTTP_PROXY https_proxy HTTPS_PROXY all_proxy ALL_PROXY export no_proxy="127.0.0.1,localhost" export NO_PROXY="127.0.0.1,localhost"

如果 Proxy 没跑，启动它（持久运行，不随 Claude Code 退出而死）

if ! lsof -i :${PROXY_PORT} >/dev/null 2>&1; then nohup node "${PROXY_SCRIPT}"
--port ${PROXY_PORT}
--chrome-port ${CHROME_PORT}
--devtools-port-file "${DEVTOOLS_PORT_FILE}"
&>"${LOG_DIR}/proxy-${PROXY_PORT}.log" & echo $! > "${PID_DIR}/proxy-${PROXY_PORT}.pid" disown sleep 2 fi

启动 chrome-devtools-mcp，连接到 Proxy

exec npx -y chrome-devtools-mcp@latest --browserUrl "http://127.0.0.1:${PROXY_PORT}"