Under the hood
A Node VM sandbox polyfill for Error instance checks now only overrides behavior for the base Error class
What
Claude Code runs some code inside a Node VM context (an isolated JavaScript sandbox), which needs a workaround so instanceof Error checks work correctly across that boundary. That workaround now only kicks in when the check is against Error itself; checks against subclasses of Error fall back to JavaScript's normal built-in behavior instead of being overridden.
Why
The previous version overrode the check unconditionally, which could give wrong answers for custom error subclasses. Narrowing it to just Error makes instance checks behave correctly in more cases.