The check that enables scroll-region terminal rendering (DECSTBM) was rewired to new guard functions
Claude Code can use a terminal feature called DECSTBM (a way of scrolling only part of the screen, used to make rendering smoother) when the terminal supports it. The sequence of checks that decides whether to turn this on was changed: the previous set of checks was replaced with two new guard functions, before falling through to the same CLAUDE_CODE_DECSTBM environment variable and the same underlying experiment flag as before.
The replacement checks appear to serve the same gating purpose as the old ones, so this looks like an internal restructuring rather than a change in behavior, though what exactly the new guard functions test isn't identified.
tengu_marlin_porch Not enough to sayNothing here resolved what this flag was doing on this version, so nothing here should be read as on or off.
This account: no value returned · anonymous baseline: no value returned · compiled default in v2.1.269: off
Read once, for one account on one subscription tier, against v2.1.269. It isn't a statement about your account. What a flag value here can and cannot tell you
The new guard functions are unnamed beyond minified identifiers, so what they specifically check is not established; nothing has been read…