Claude in Chrome: browser automation from one machine took over the browser on a different machine

What happened

A Claude Code session running on machine A used the Claude in Chrome browser tools during a task. The browser automation attached to a Chrome instance on machine B — a different physical computer — and took over the active browser window there, navigating it away from what the user was doing.

The user was not working in the Claude Code session on machine B and did not expect any browser on that machine to be driven.

Expected

Browser automation initiated from a session on one machine should only be able to drive a browser on that same machine, or at minimum should require an explicit, per-machine confirmation before attaching to a browser elsewhere.

Actual

The session silently attached to and controlled the browser on another machine, interrupting the user's work there.

Notes

• The extension was installed and previously authorized on machine B.
• No prompt or indication appeared on machine A that the browser being driven was remote.
• This is a surprising trust boundary: "allow Claude to use my browser" on one machine appears to grant browser control from sessions running elsewhere.

Impact

Unexpected takeover of an active browser window on a machine the user was actively using, with no confirmation step and no indication in the originating session that the target browser was on a different device.