fix(tui): avoid tall dialog redraw loops

closes #5990

packages/tui/test/tui-render.test.ts

@@ -378,6 +378,44 @@ describe("TUI resize handling", () => {
 		});
 	});
 
+	it("full re-renders in Termux when height changes reveal skipped offscreen changes", async () => {
+		await withEnv({ TERMUX_VERSION: "1" }, async () => {
+			const terminal = new VirtualTerminal(20, 5);
+			const tui = new TUI(terminal);
+			const component = new TestComponent();
+			tui.addChild(component);
+
+			component.lines = Array.from({ length: 11 }, (_, i) => `Line ${i}`);
+			tui.start();
+			await terminal.waitForRender();
+
+			component.lines = Array.from({ length: 11 }, (_, i) => (i === 5 ? "Changed 5" : `Line ${i}`));
+			tui.requestRender();
+			await terminal.waitForRender();
+
+			const redrawsAfterSkippedChange = tui.fullRedraws;
+			assert.deepStrictEqual(terminal.getViewport(), ["Line 6", "Line 7", "Line 8", "Line 9", "Line 10"]);
+
+			terminal.resize(20, 6);
+			await terminal.waitForRender();
+
+			assert.ok(
+				tui.fullRedraws > redrawsAfterSkippedChange,
+				"Height change should redraw before skipped offscreen content becomes visible",
+			);
+			assert.deepStrictEqual(terminal.getViewport(), [
+				"Changed 5",
+				"Line 6",
+				"Line 7",
+				"Line 8",
+				"Line 9",
+				"Line 10",
+			]);
+
+			tui.stop();
+		});
+	});
+
 	it("triggers full re-render when terminal width changes", async () => {
 		const terminal = new VirtualTerminal(40, 10);
 		const tui = new TUI(terminal);
@@ -657,6 +695,32 @@ describe("TUI differential rendering", () => {
 		tui.stop();
 	});
 
+	it("does not full redraw for offscreen changes above the viewport", async () => {
+		const terminal = new VirtualTerminal(20, 5);
+		const tui = new TUI(terminal);
+		const component = new TestComponent();
+		tui.addChild(component);
+
+		const stableVisibleLines = Array.from({ length: 8 }, (_, i) => `Dialog ${i}`);
+		component.lines = ["Ticker 0", "Intro", "", ...stableVisibleLines];
+		tui.start();
+		await terminal.waitForRender();
+
+		const initialRedraws = tui.fullRedraws;
+		const initialViewport = terminal.getViewport();
+
+		for (let i = 1; i <= 3; i++) {
+			component.lines = [`Ticker ${i}`, "Intro", "", ...stableVisibleLines];
+			tui.requestRender();
+			await terminal.waitForRender();
+		}
+
+		assert.strictEqual(tui.fullRedraws, initialRedraws, "Offscreen changes should not force full redraws");
+		assert.deepStrictEqual(terminal.getViewport(), initialViewport, "Visible viewport should remain stable");
+
+		tui.stop();
+	});
+
 	it("full re-renders when deleted lines move the viewport upward", async () => {
 		const terminal = new VirtualTerminal(20, 5);
 		const tui = new TUI(terminal);