Intel / article

Quoting Felix Rieseberg

Source: simonwillison.net
Date: Published Oct 5, 2026

Why it matters

Cowork sessions now run in isolated cloud sandboxes instead of a local VM. Work continues after you close your laptop and works from a phone, while the desktop app only brokers file access. Useful for anyone designing sandboxing.

Key takeaways · AI-distilled

Rieseberg says the earlier Cowork already ran in the cloud, but executed tool calls inside an Anthropic-provided VM shipped to the user's computer, mapping in only the data explicitly added to a session.
Anthropic added that local VM for capability, safety and security, but users disliked its disk, battery and performance cost, and the fact that closing the laptop stopped the work.
In the new design each session gets its own cloud that shares no state with other sessions; when the VM needs something on the device, such as a file, the desktop app handles that file-access tool call.

Terms in this piece · Glossary

inference — Running a trained model to get answers — the phase where AI is actually used, as opposed to trained.
sandbox — An isolated environment where AI-generated code or agent actions run without being able to touch anything real.
AI agent — An AI system that doesn't just answer once but works toward a goal in a loop — taking actions, reading the results, and deciding what to do next.

Read the source simonwillison.net