Using a browser on the host

Agents that test web apps need a browser. Instead of installing Chrome in every devcontainer, you can let containers reach a Chrome that already runs on your machine. opendevhub carries the connection through the relay it runs in each container, the same way it forwards your ssh-agent.

Host portsCopy Anchor Link

A project's host ports are ports on your machine that its containers reach at localhost on the same port. Add them in the project's settings (the gear in the project header), under Host ports. Running containers pick changes up right away; nothing restarts.

• Inside the container, the port listens on 127.0.0.1 (and ::1 where the container has it). Each connection goes to localhost:<port> on your machine.
• opendevhub only connects to your machine's loopback, and only on ports in the list. Nothing on your machine is opened to the network.
• The checkout page shows each host port next to the forwarded ports. A red dot means it isn't working; hover it for the reason.
• A port can't be both a forwarded port and a host port. If devcontainer.json forwards a port that is also a host port, the host port wins and the log says the forward was skipped.

They are stored in ~/.config/opendevhub/config.json:

{ "projects": { "/src/app": { "hostPorts": [9222] } } }

Start Chrome for agentsCopy Anchor Link

Run a separate Chrome with a debugging port and its own profile folder:

# Linux
google-chrome --remote-debugging-port=9222 --user-data-dir="$HOME/.opendevhub-chrome"

# macOS
"/Applications/Google Chrome.app/Contents/MacOS/Google Chrome" \
  --remote-debugging-port=9222 --user-data-dir="$HOME/.opendevhub-chrome"

--user-data-dir is required: Chrome 136 and later ignore --remote-debugging-port on your default profile. Check that it listens with curl http://localhost:9222/json/version on your machine.

Then add 9222 under Host ports in the project's settings. From inside a container, curl http://localhost:9222/json/version now answers too.

Point the MCP server at itCopy Anchor Link

For chrome-devtools-mcp, pass --browser-url so it connects instead of launching its own Chrome. In the project's opencode.json:

{
  "mcp": {
    "chrome-devtools": {
      "type": "local",
      "command": [
        "npx",
        "-y",
        "chrome-devtools-mcp@latest",
        "--browser-url=http://localhost:9222"
      ]
    }
  }
}

For Playwright MCP, use --cdp-endpoint the same way:

{
  "mcp": {
    "playwright": {
      "type": "local",
      "command": [
        "npx",
        "-y",
        "@playwright/mcp@latest",
        "--cdp-endpoint=http://localhost:9222"
      ]
    }
  }
}

The container still needs Node for npx, but no browser.

Things to knowCopy Anchor Link

• All tasks of the project share the one browser, so parallel tasks can step on each other's tabs.
• The browser is only reachable while opendevhub runs; otherwise connections inside the container are refused.
• See Known limitations for what host ports don't do.