Anthropic describes containment as the core security strategy for increasingly capable Claude agents. The post compares ephemeral containers for claude.ai, OS-level sandboxing and approvals for Claude Code, and VM isolation for Claude Cowork. It also details missed risks, including pre-trust project config execution, user-delivered prompt injection, exfiltration through approved domains, and reduced enterprise visibility inside VMs.
Anthropic explains how process sandboxes, VMs, filesystem boundaries, and egress controls limit what Claude agents can access. Claude.ai uses gVisor; local Claude Code uses Seatbelt on macOS and Bubblewrap on Linux; Cowork runs in a full VM. Simon Willison highlights the documentation quality, notes a previously missed file-exfiltration path, and plans to revisit Anthropic's open-source srt tool.