Under the hoodTier: how much it should matter to you
2Useful: my rating, 1 to 5
2Signal: worth watching, 1 to 5
ElsewhereArea: what it touches
Internal ChangesKind: in v2.1.302,
Internal ChangesSection of the release
What
A sandbox is a restricted environment that limits which files and folders the commands Claude runs can touch. Two things changed in how Claude Code handles it:
Sandbox errors are now reported from a table of named messages, such as "sandbox: failed to initialize".
On Windows, reading and changing folder permissions now goes through a built-in feature of the runtime Claude Code runs on, instead of calling Windows system functions directly.
If the runtime does not have that feature, Claude Code logs a message saying folder permissions can be neither read nor changed, and asks you to run the pinned @anthropic-ai/bun-internal runtime.
Why
This lays groundwork for sandboxing on Windows and gives sandbox failures clearer, consistent names.
