fix(tui): preserve ANSI order at slice boundaries

Fixes color bleeding after mouse selection and search highlights in
fullscreen mode when a styled token ends at the highlight boundary.

closes #10169

packages/tui/CHANGELOG.md

@@ -6,6 +6,10 @@
 
 - Added `TuiAltScreen.getScreenLines()`, which returns the lines of the last rendered frame.
 
+### Fixed
+
+- Fixed color bleeding past mouse selections and search highlights in fullscreen mode when a styled token ends at the highlight boundary ([#10169](https://github.com/earendil-works/pi/issues/10169))
+
 ## [0.99.2] - 2026-09-30
 
 ## [0.99.1] - 2026-09-29

packages/tui/src/utils.ts

@@ -1273,8 +1273,11 @@ export function sliceWithWidth(
 	while (i < line.length) {
 		const ansi = extractAnsiCode(line, i);
 		if (ansi) {
-			if (currentCol >= startCol && currentCol < endCol) result += ansi.code;
-			else if (currentCol < startCol) pendingAnsi += ansi.code;
+			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;
 			i += ansi.length;
 			continue;
 		}

packages/tui/test/regression-slice-by-column-ansi-order.test.ts

@@ -0,0 +1,17 @@
+import assert from "node:assert";
+import { describe, it } from "node:test";
+import { sliceByColumn } from "../src/utils.ts";
+
+// https://github.com/earendil-works/pi/issues/10169
+describe("sliceByColumn ANSI order regression", () => {
+	it("keeps a reset at the slice start after earlier style codes", () => {
+		const line = "\x1b[32mfoo\x1b[39m bar";
+		assert.strictEqual(sliceByColumn(line, 3, 4, true), "\x1b[32m\x1b[39m bar");
+	});
+
+	it("does not leak color into text after a highlighted token", () => {
+		const line = "Another \x1b[35malpha\x1b[39m line with \x1b[35mbeta\x1b[39m later.";
+		const after = sliceByColumn(line, 13, 100, true);
+		assert.strictEqual(after, "\x1b[35m\x1b[39m line with \x1b[35mbeta\x1b[39m later.");
+	});
+});