fix(tui): prevent cursor marker leaks (#9441)

Closes #9257, closes #9332

packages/tui/src/tui.ts

@@ -1458,7 +1458,8 @@ export abstract class TuiBase extends Container implements TUI {
 		for (let i = 0; i < lines.length; i++) {
 			const line = lines[i];
 			if (!isImageLine(line)) {
-				lines[i] = normalizeTerminalOutput(line) + reset;
+				// Cursor markers are internal render metadata and must never reach terminal output.
+				lines[i] = normalizeTerminalOutput(line.replaceAll(CURSOR_MARKER, "")) + reset;
 			}
 		}
 		return lines;
@@ -1493,8 +1494,9 @@ export abstract class TuiBase extends Container implements TUI {
 				const beforeMarker = line.slice(0, markerIndex);
 				const col = visibleWidth(beforeMarker);
 
-				// Strip marker from the line
-				lines[row] = line.slice(0, markerIndex) + line.slice(markerIndex + CURSOR_MARKER.length);
+				// Strip all markers from the selected line. The first marker determines the
+				// hardware cursor position; any others are stale internal sentinels.
+				lines[row] = line.replaceAll(CURSOR_MARKER, "");
 
 				return { row, col };
 			}

packages/tui/src/utils.ts

@@ -1347,11 +1347,13 @@ export function sliceWithWidth(
 	while (i < line.length) {
 		const ansi = extractAnsiCode(line, i);
 		if (ansi) {
+			// APC sequences (cursor markers) are positional one-shot commands, not persistent style
+			// state, so codes before the range carry over only when they are not APC.
 			if (currentCol >= startCol && currentCol < endCol) {
 				// Keep original order: codes from before the range must precede codes at the boundary
 				result += pendingAnsi + ansi.code;
 				pendingAnsi = "";
-			} else if (currentCol < startCol) pendingAnsi += ansi.code;
+			} else if (currentCol < startCol && !ansi.code.startsWith("\x1b_")) pendingAnsi += ansi.code;
 			i += ansi.length;
 			continue;
 		}

packages/tui/test/tab-width.test.ts

@@ -1,6 +1,6 @@
 import assert from "node:assert";
 import { describe, it } from "node:test";
-import type { Component, TUI } from "../src/tui.ts";
+import { type Component, CURSOR_MARKER, type TUI } from "../src/tui.ts";
 import { TuiMainScreen } from "../src/tui-main-screen.ts";
 import { extractSegments, normalizeTerminalOutput, sliceWithWidth, visibleWidth } from "../src/utils.ts";
 import { VirtualTerminal } from "./virtual-terminal.ts";
@@ -44,6 +44,21 @@ describe("tab width accounting", () => {
 		assert.strictEqual(visibleWidth(slice.text), slice.width);
 	});
 
+	it("does not carry cursor markers into later slices", () => {
+		// Regression for #9332: APC markers are positional metadata, not persistent style.
+		const line = `ab${CURSOR_MARKER}cdefghij`;
+
+		assert.deepStrictEqual(sliceWithWidth(line, 4, 2, true), { text: "ef", width: 2 });
+		assert.deepStrictEqual(sliceWithWidth(line, 6, 4, true), { text: "ghij", width: 4 });
+	});
+
+	it("continues to carry persistent styling into later slices", () => {
+		// Regression for #9332: excluding APC must not disable persistent SGR styling.
+		const line = "\x1b[31mabcdefghij\x1b[0m";
+
+		assert.deepStrictEqual(sliceWithWidth(line, 4, 2, true), { text: "\x1b[31mef", width: 2 });
+	});
+
 	it("keeps overlay segment widths consistent with visible width", () => {
 		const text = "out 192M\t.pi/skill-tests/results-ha";
 		const segments = extractSegments(text, 10, 13, 10, true);

packages/tui/test/tui-alt-screen.test.ts

@@ -22,7 +22,7 @@ import {
 	resetCapabilitiesCache,
 	setCapabilities,
 } from "../src/terminal-image.ts";
-import { renderFakeCursor, type TuiMouseEvent } from "../src/tui.ts";
+import { CURSOR_MARKER, renderFakeCursor, type TuiMouseEvent } from "../src/tui.ts";
 import { TuiAltScreen } from "../src/tui-alt-screen.ts";
 import { stripTerminalSequences, visibleWidth } from "../src/utils.ts";
 import { defaultEditorTheme } from "./test-themes.ts";
@@ -65,6 +65,34 @@ class RecordingTerminal extends VirtualTerminal {
 }
 
 describe("TuiAltScreen", () => {
+	it("does not leak cursor markers while selecting after the caret", async () => {
+		const terminal = new RecordingTerminal(20, 4);
+		const tui = new TuiAltScreen(terminal, undefined, undefined, { copyOnSelect: false });
+		// Regression for #9257 and #9332: selection slicing must not duplicate cursor markers.
+		tui.addChild({
+			render: () => [`ab${CURSOR_MARKER}cdefghij`],
+			invalidate() {},
+		});
+
+		tui.start();
+		await terminal.waitForRender();
+		const eventCount = terminal.events.length;
+
+		terminal.sendInput("\x1b[<0;5;1M");
+		terminal.sendInput("\x1b[<32;7;1M");
+		await terminal.waitForRender();
+
+		const output = terminal.events
+			.slice(eventCount)
+			.filter((event) => event.type === "write")
+			.map((event) => event.data)
+			.join("");
+		assert.ok(output.includes("\x1b[7m"), "dragged text should be highlighted");
+		assert.ok(!output.includes(CURSOR_MARKER), "internal cursor markers must not reach the terminal");
+		terminal.sendInput("\x1b[<0;7;1m");
+		tui.stop();
+	});
+
 	it("renders a terminal-height viewport and preserves manual scroll position", async () => {
 		const terminal = new VirtualTerminal(20, 4);
 		const tui = new TuiAltScreen(terminal);

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

@@ -165,6 +165,40 @@ describe("TUI debug logging", () => {
 });
 
 describe("TUI bounded render output", () => {
+	it("does not write duplicate cursor markers to the terminal", () => {
+		const terminal = new BoundedWriteTerminal();
+		const tui = new TuiMainScreen(terminal);
+		const component = new TestComponent();
+		// Regression for #9257: terminals may render the payload of a leaked APC marker.
+		component.lines = [`\x1b[31m界🙂\x1b[0m${CURSOR_MARKER} world${CURSOR_MARKER}`];
+		tui.addChild(component);
+
+		tui.renderNow();
+
+		const output = terminal.writes.join("");
+		assert.ok(output.includes("\x1b[31m界🙂\x1b[0m world"), "visible styled text should be preserved");
+		assert.ok(!output.includes(CURSOR_MARKER), "internal cursor markers must not reach the terminal");
+		assert.ok(output.includes("\x1b[5G"), "the first marker should keep the cursor at visible column 4");
+	});
+
+	it("does not write cursor markers from other visible or scrollback lines", () => {
+		const terminal = new BoundedWriteTerminal();
+		terminal.rows = 2;
+		const tui = new TuiMainScreen(terminal);
+		const component = new TestComponent();
+		// Regression for #9257: cursor extraction must not leave markers on other rendered lines.
+		component.lines = [`offscreen${CURSOR_MARKER}`, `a${CURSOR_MARKER}`, `visible-b${CURSOR_MARKER}`];
+		tui.addChild(component);
+
+		tui.renderNow();
+
+		const output = terminal.writes.join("");
+		assert.ok(output.includes("offscreen"), "full renders should preserve scrollback content");
+		assert.ok(output.includes("a"), "full renders should preserve other visible lines");
+		assert.ok(!output.includes(CURSOR_MARKER), "internal cursor markers must not reach the terminal");
+		assert.ok(output.includes("\x1b[10G"), "the bottom visible marker should determine the cursor column");
+	});
+
 	it("splits a large full render without changing its output", () => {
 		const terminal = new BoundedWriteTerminal();
 		const tui = new TuiMainScreen(terminal);