Quoting Felix Rieseberg

Anthropic has moved Claude Cowork's model inference and its VM entirely to the cloud, with each session getting its own sandbox that does not share state with other sessions, according to Felix Rieseberg of Anthropic. The previous version ran inference in the cloud but executed tool calls in an Anthropic-provided VM shipped to the user's computer, which users disliked for its disk, battery and performance cost and because closing the laptop stopped the work. In the new version, when the VM needs something on the user's device such as a file, the desktop app handles that file access tool call, which Anthropic says enables using Cowork from a phone and keeping work running without draining battery.

The "old" version of Cowork runs model inference in the cloud, executing tool calls in an Anthropic-provided VM we shipped to your computer. We added the VM for capability, safety, and security reasons - mapping in just the data you explicitly added to your session. People loved what they were able to do with Claude but didn't love the disk, battery, and performance cost of running the VM locally. Also, people didn't love that closing your laptop means the work stops. The "new" version of Cowork runs model inference and the VM in the cloud. Each session gets its own sandbox, not sharing state with other sessions. When the VM needs something on the users' device like a file , the desktop app is responsible for that file access tool call. ... We think this solves a lot of problems we've heard about like using Cowork from a phone, keeping work running, or getting all the same power without losing battery to the VM — Felix Rieseberg https://twitter.com/felixrieseberg/status/2107206431376334975 , Anthropic, see also this help page https://support.claude.com/en/articles/15520349-use-claude-cowork-on-web-desktop-and-mobile h f951c27c48 Tags: claude-cowork https://simonwillison.net/tags/claude-cowork , anthropic https://simonwillison.net/tags/anthropic , claude https://simonwillison.net/tags/claude , generative-ai https://simonwillison.net/tags/generative-ai , ai https://simonwillison.net/tags/ai , general-agents https://simonwillison.net/tags/general-agents , llms https://simonwillison.net/tags/llms