fix(tui): protected editor border from IME preedit

- Kept the focused hardware-cursor row empty to its right so terminal-local marked text cannot shift box chrome.

- Rendered a dedicated bottom border and covered terminal insert-mode preedit with a regression test.

Fixes #5563

packages/tui/CHANGELOG.md

@@ -7,6 +7,10 @@
 - Display LaTeX now renders `\underbrace`/`\overbrace` (and the bracket/paren variants) as drawn horizontal braces with centered labels, and stacks `\overset`/`\underset`/`\stackrel` annotations above/below the base instead of falling back to flat inline glyphs.
 - Display LaTeX renders multi-letter script words (`N_{turns}`) as raised/lowered blocks instead of ragged per-character Unicode sub/superscript glyphs; single letters and digits keep the compact Unicode forms.
 
+### Fixed
+
+- Fixed macOS IME marked text displacing the prompt editor border when entering fullwidth CJK punctuation ([#5563](https://github.com/can1357/oh-my-pi/issues/5563)).
+
 ## [16.5.2] - 2026-07-14
 
 ### Fixed

packages/tui/src/components/editor.ts

@@ -866,6 +866,7 @@ export class Editor implements Component, Focusable {
 			let displayWidth = visibleWidth(layoutLine.text);
 			let cursorPaddingOverflow = 0;
 			let decorated = false;
+			let imeSafeCursorTail = false;
 			const showPromptGutter = promptGutter !== undefined && visibleIndex === 0;
 			const gutterText =
 				promptGutter === undefined ? "" : showPromptGutter ? promptGutter.firstLine : promptGutter.continuation;
@@ -931,6 +932,10 @@ export class Editor implements Component, Focusable {
 						displayText = this.#renderTerminalCursorMarker(before, marker, lineContentWidth);
 					} else {
 						displayText = before + marker + after;
+						// Terminal frontends render IME marked text locally before committed bytes
+						// reach the application. Keep the end-of-input cursor row empty to its
+						// right so that insertion cannot shift box chrome onto the next row.
+						imeSafeCursorTail = after.length === 0 && borderVisible;
 					}
 				}
 			} else if (hasCursor && !this.#useTerminalCursor) {
@@ -1022,6 +1027,15 @@ export class Editor implements Component, Focusable {
 			// trailing `─`, but never the corner/vertical bar itself.
 			const isLastLine = visibleIndex === visibleLayoutLines.length - 1;
 			const rightChromeCells = Math.max(1, paddingX + 1 - cursorPaddingOverflow);
+			if (isLastLine && imeSafeCursorTail) {
+				const leftBorder = this.borderColor(`${box.vertical}${padding(paddingX)}`);
+				const bottomBorder = this.borderColor(
+					`${box.bottomLeft}${box.horizontal.repeat(Math.max(0, width - 2))}${box.bottomRight}`,
+				);
+				result.push(leftBorder + displayText);
+				result.push(bottomBorder);
+				continue;
+			}
 			if (isLastLine) {
 				const rightPad = Math.max(0, rightChromeCells - 2);
 				const includeHorizontal = rightChromeCells >= 2;

packages/tui/test/editor.test.ts

@@ -3,13 +3,14 @@ import * as fs from "node:fs/promises";
 import * as os from "node:os";
 import * as path from "node:path";
 import { stripVTControlCharacters } from "node:util";
-import { CURSOR_MARKER } from "@oh-my-pi/pi-tui";
+import { CURSOR_MARKER, TUI } from "@oh-my-pi/pi-tui";
 import { CombinedAutocompleteProvider } from "@oh-my-pi/pi-tui/autocomplete";
 import { Editor } from "@oh-my-pi/pi-tui/components/editor";
 import { KeybindingsManager, setKeybindings, TUI_KEYBINDINGS } from "@oh-my-pi/pi-tui/keybindings";
 import { setKittyProtocolActive } from "@oh-my-pi/pi-tui/keys";
 import { visibleWidth } from "@oh-my-pi/pi-tui/utils";
 import { defaultEditorTheme } from "./test-themes";
+import { VirtualTerminal } from "./virtual-terminal";
 
 describe("Editor component", () => {
 	afterEach(() => {
@@ -852,6 +853,36 @@ describe("Editor component", () => {
 			}
 		});
 
+		it("keeps terminal-local IME preedit from displacing the editor border (#5563)", async () => {
+			const width = 20;
+			const terminal = new VirtualTerminal(width, 6, 1_000);
+			const tui = new TUI(terminal, true);
+			const editor = new Editor(defaultEditorTheme);
+			tui.addChild(editor);
+			tui.setFocus(editor);
+
+			try {
+				tui.start();
+				await terminal.waitForRender();
+				for (const char of "ast") editor.handleInput(char);
+				tui.requestRender();
+				await terminal.waitForRender();
+
+				const beforePreedit = terminal.getViewport().map(row => row.trimEnd());
+				expect(beforePreedit.slice(0, 3)).toEqual(["+------------------+", "|  ast", "+------------------+"]);
+
+				// macOS Terminal renders marked text locally in insertion mode before
+				// committed bytes reach OMP. The open cursor row must not carry right
+				// chrome that the marked text can shift onto another row.
+				terminal.write("\x1b[4hast，\x1b[4l");
+				const afterPreedit = terminal.getViewport().map(row => row.trimEnd());
+				expect(afterPreedit[1]).toBe("|  astast，");
+				expect(afterPreedit[2]).toBe(beforePreedit[2]);
+			} finally {
+				tui.stop();
+			}
+		});
+
 		it("shows cursor at end before wrap and wraps on next char", () => {
 			for (const paddingX of [0, 1]) {
 				const editor = new Editor({ ...defaultEditorTheme, editorPaddingX: paddingX });