Anthropic open-sources sandbox-runtime for OS-level AI agent isolation

Anthropic has released sandbox-runtime (srt), the OS-level sandbox behind Claude Code's sandboxed bash tool, as an open-source npm package. Version 0.0.81 under Apache-2.0 requires Node.js 22.12+ and uses Seatbelt on macOS and bubblewrap on Linux; Anthropic reports an 84% drop in permission prompts in internal Claude Code usage.

• Package @anthropic-ai/sandbox-runtime v0.0.81 is about 11.4 MB unpacked under Apache-2.0
• macOS uses Seatbelt, Linux uses bubblewrap; Windows support is alpha
• Writes and network are denied by default, reads allowed everywhere
• Anthropic's internal data shows 84% fewer permission prompts in Claude Code