- Added `terminalHasEagerEraseScrollbackRisk` to detect WezTerm, kitty, ghostty, and alacritty on POSIX, where xterm ED3 (`CSI 3 J`) can snap scrolled-up readers back to the tail during streaming.
- Kept direct user-input and checkpoint rebuilds unaffected by the deferral.
- Added regression tests covering the deferred and non-deferred paths (issue #1682).