Under the hood
Detection of a specific thinking-display API error now uses only a regex match, not an added string check
What
Claude Code detects a particular API error (a 400-level error about how 'thinking' output should be displayed) in order to handle it specially. The detection logic now relies only on a regular expression match against the error message, dropping a second string-matching condition that used to also trigger the detection.
Why
Simplifying to a single check reduces duplicate logic; the regex alone was apparently sufficient to catch the cases the extra string match was also catching.