fix(cli): replace clearTerminal with targeted repaint on resize (#3967)

Add repaintStaticViewport() that uses cursorTo(0,0)+eraseDown instead
of the full clearTerminal (ESC[2J ESC[3J ESC[H]) sequence. Hook it to
terminal width changes via a new useEffect that guards against no-op
repaints when width is unchanged.

clearTerminal remains in use for explicit refreshStatic() calls (model
switches, /clear, etc.) where a full history remount is intended.
previousTerminalWidthRef ensures the resize effect only fires on actual
column changes, not height-only resizes.

Closes the full-screen flash that occurs on every terminal width change.

Generated with AI

Co-authored-by: 秦奇 <gary.gq@alibaba-inc.com>
Co-authored-by: Qwen-Coder <qwen-coder@alibabacloud.com>

packages/cli/src/ui/AppContainer.tsx

@@ -374,6 +374,7 @@ export const AppContainer = (props: AppContainerProps) => {
 
   // Terminal and layout hooks
   const { columns: terminalWidth, rows: terminalHeight } = useTerminalSize();
+  const previousTerminalWidthRef = useRef(terminalWidth);
   const { stdin, setRawMode } = useStdin();
   const { stdout } = useStdout();
 
@@ -570,6 +571,13 @@ export const AppContainer = (props: AppContainerProps) => {
     remountStaticHistory();
   }, [remountStaticHistory, stdout]);
 
+  // Targeted repaint for resize events: move cursor to top-left and erase
+  // downward instead of a full clearTerminal, avoiding the full-screen flash.
+  const repaintStaticViewport = useCallback(() => {
+    stdout.write(`${ansiEscapes.cursorTo(0, 0)}${ansiEscapes.eraseDown}`);
+    remountStaticHistory();
+  }, [remountStaticHistory, stdout]);
+
   // Keep the static header in sync with model changes without polling.
   // Ink's <Static> output is append-only, so model changes must explicitly
   // clear and remount the static region to redraw the banner at the top.
@@ -1765,6 +1773,14 @@ export const AppContainer = (props: AppContainerProps) => {
     }
   }, [terminalWidth, availableTerminalHeight, activePtyId]);
 
+  useEffect(() => {
+    if (previousTerminalWidthRef.current === terminalWidth) {
+      return;
+    }
+    previousTerminalWidthRef.current = terminalWidth;
+    repaintStaticViewport();
+  }, [terminalWidth, repaintStaticViewport]);
+
   useEffect(() => {
     if (ideNeedsRestart) {
       // IDE trust changed, force a restart.