Cowork Can Use a Chrome Instance on Another Machine Without You Knowing

A Reddit user testing Cowork on Linux asked it to search booking.com. Cowork requested Chrome permission, but Chrome wasn't installed on the Linux machine. When confronted, the Claude-powered assistant admitted the browser connected was flagged isLocal: false — meaning the Chrome instance with the Claude in Chrome extension was on a Windows device elsewhere (authenticated via Anthropic account). The user later confirmed the open tab on their Windows desktop.

Key technical detail: the assistant stated the connected browser appears as isLocal: false, indicating it's not on the current machine. The extension must be installed and paired via the same Anthropic account on the remote machine, and that browser must be left running.

This behavior is not documented — the assistant itself couldn't find docs when asked. Developers using Cowork should be aware that permission prompts for browser use may refer to a remote Chrome instance. To see the actual browser tab, you need to be physically at the machine where the extension is paired.

This is a significant privacy/routing consideration: the AI agent can transparently use a browser on another machine without explicit user awareness that the browser is remote. The user wasn't gaslit — the assistant simply misidentified the browser's location initially.

Who this affects

Anyone using Cowork (or similar AI agents with browser use) across multiple machines with the same Anthropic account. Check which machine has the paired extension and is currently running Chrome.