You'll noticeTier: how much it should matter to you
2Useful: my rating, 1 to 5
3Signal: worth watching, 1 to 5
RuntimeArea: what it touches
ImprovementsKind: in v2.1.319,
ImprovementsSection of the release
What
Bun is the JavaScript runtime, the engine, that can run Claude Code. Claude Code sometimes runs code in a separate isolated context. If the Bun it is running under cannot recognise such a context, Claude Code now refuses to create it. The error says sandbox checks could otherwise be bypassed and tells you to run Claude Code's native build, whose runtime can recognise it.
Why
This closes a gap in the sandbox, the protective boundary around what code can do, when Claude Code is not run as its native build.
