fix(tui): reset styles per line

packages/coding-agent/docs/tui.md

@@ -24,6 +24,8 @@ interface Component {
 | `handleInput?(data)` | Receive keyboard input when component has focus. |
 | `invalidate?()` | Clear cached render state. |
 
+The TUI appends a full SGR reset and OSC 8 reset at the end of each rendered line. Styles do not carry across lines. If you emit multi-line text with styling, reapply styles per line or use `wrapTextWithAnsi()` so styles are preserved for each wrapped line.
+
 ## Using Components
 
 **In hooks** via `ctx.ui.custom()`:

packages/tui/CHANGELOG.md

@@ -10,6 +10,7 @@
 ### Fixed
 
 - Cursor now moves to end of content on exit, preventing status line from being overwritten ([#629](https://github.com/badlogic/pi-mono/pull/629) by [@tallshort](https://github.com/tallshort))
+- Reset ANSI styles after each rendered line to prevent style leakage
 
 ## [0.42.5] - 2026-01-11
 

packages/tui/README.md

@@ -74,6 +74,8 @@ interface Component {
 | `handleInput?(data)` | Called when the component has focus and receives keyboard input. The `data` string contains raw terminal input (may include ANSI escape sequences). |
 | `invalidate?()` | Called to clear any cached render state. Components should re-render from scratch on the next `render()` call. |
 
+The TUI appends a full SGR reset and OSC 8 reset at the end of each rendered line. Styles do not carry across lines. If you emit multi-line text with styling, reapply styles per line or use `wrapTextWithAnsi()` so styles are preserved for each wrapped line.
+
 ## Built-in Components
 
 ### Container

packages/tui/src/tui.ts

@@ -289,6 +289,11 @@ export class TUI extends Container {
 
 	private static readonly SEGMENT_RESET = "\x1b[0m\x1b]8;;\x07";
 
+	private applyLineResets(lines: string[]): string[] {
+		const reset = TUI.SEGMENT_RESET;
+		return lines.map((line) => (this.containsImage(line) ? line : line + reset));
+	}
+
 	/** Splice overlay content into a base line at a specific column. Single-pass optimized. */
 	private compositeLineAt(
 		baseLine: string,
@@ -343,6 +348,8 @@ export class TUI extends Container {
 			newLines = this.compositeOverlays(newLines, width, height);
 		}
 
+		newLines = this.applyLineResets(newLines);
+
 		// Width changed - need full re-render
 		const widthChanged = this.previousWidth !== 0 && this.previousWidth !== width;
 

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

@@ -1,5 +1,6 @@
 import assert from "node:assert";
 import { describe, it } from "node:test";
+import type { Terminal as XtermTerminalType } from "@xterm/headless";
 import { type Component, TUI } from "../src/tui.js";
 import { VirtualTerminal } from "./virtual-terminal.js";
 
@@ -11,6 +12,16 @@ class TestComponent implements Component {
 	invalidate(): void {}
 }
 
+function getCellItalic(terminal: VirtualTerminal, row: number, col: number): number {
+	const xterm = (terminal as unknown as { xterm: XtermTerminalType }).xterm;
+	const buffer = xterm.buffer.active;
+	const line = buffer.getLine(buffer.viewportY + row);
+	assert.ok(line, `Missing buffer line at row ${row}`);
+	const cell = line.getCell(col);
+	assert.ok(cell, `Missing cell at row ${row} col ${col}`);
+	return cell.isItalic();
+}
+
 describe("TUI differential rendering", () => {
 	it("tracks cursor correctly when content shrinks with unchanged remaining lines", async () => {
 		const terminal = new VirtualTerminal(40, 10);
@@ -68,6 +79,20 @@ describe("TUI differential rendering", () => {
 		tui.stop();
 	});
 
+	it("resets styles after each rendered line", async () => {
+		const terminal = new VirtualTerminal(20, 6);
+		const tui = new TUI(terminal);
+		const component = new TestComponent();
+		tui.addChild(component);
+
+		component.lines = ["\x1b[3mItalic", "Plain"];
+		tui.start();
+		await terminal.flush();
+
+		assert.strictEqual(getCellItalic(terminal, 1, 0), 0);
+		tui.stop();
+	});
+
 	it("renders correctly when first line changes but rest stays same", async () => {
 		const terminal = new VirtualTerminal(40, 10);
 		const tui = new TUI(terminal);