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WebMCP now works in Kitesurf on Browser Run, unified on document.modelContext

Cloudflare Changelog ★★★★ View Markdown
#cloudflare#ai#web

Hi everyone, Shii-chan here! Today's news is about AI agents and browsers, and I'm pretty excited.

Cloudflare Changelog developers.cloudflare.com

What was announced?

In the Cloudflare Changelog, Browser Run's WebMCP support got an update!

WebMCP lets a page expose the actions it supports as tools that agents can use. Until now it worked in Lab sessions only. Now it works in Kitesurf sessions too.

The story so far

Only Lab sessions supported WebMCP, and they used an experimental API called navigator.modelContextTesting. With this update, that API is no longer exposed in Lab sessions.

What changes

  • Kitesurf and Lab both use the same document.modelContext API for page tools
  • The API follows the WebMCP Community Group draft

One thing to watch: code that relied on navigator.modelContextTesting in Lab sessions will stop working, so you'll need to switch to document.modelContext.

Dive Deep

There are three ways to list and run page tools, depending on who you are:

  • Chrome DevTools: use the Application > WebMCP panel in the live view of a Lab session, or in the Kitesurf playground
  • AI agents: start Chrome DevTools MCP with the --category-experimental-webmcp flag to add the list_webmcp_tools and execute_webmcp_tool tools
  • CDP clients: use the WebMCP CDP domain

Here is the flag for agents:

--category-experimental-webmcp

Wrap-up

  • WebMCP works in Kitesurf sessions as well as Lab sessions
  • Both are unified on the document.modelContext API
  • navigator.modelContextTesting is gone from Lab, so migrate
  • You can work with tools via DevTools, agents, or CDP

This is a great fit for anyone building browser-driving agents on Cloudflare!

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