fix(terminal): preserve zellij mouse mode on reconnect

frontend/src/renderer/components/TerminalPane.tsx

@@ -7,7 +7,7 @@ import { SearchAddon } from "@xterm/addon-search";
 import { WebLinksAddon } from "@xterm/addon-web-links";
 import type { WorkspaceSession } from "../types/workspace";
 import type { Theme } from "../stores/ui-store";
-import { useTerminalSession, type TerminalSessionState } from "../hooks/useTerminalSession";
+import { useTerminalSession, type AttachableTerminal, type TerminalSessionState } from "../hooks/useTerminalSession";
 
 type TerminalPaneProps = {
 	session?: WorkspaceSession;
@@ -70,6 +70,8 @@ function bannerText(state: TerminalSessionState, error?: string): string | undef
 	return undefined;
 }
 
+const CLEAR_SEQUENCE = "\x1b[3J\x1b[2J\x1b[H";
+
 function XtermTerminal({ session, theme, daemonReady }: TerminalPaneProps) {
 	const containerRef = useRef<HTMLDivElement | null>(null);
 	const terminalRef = useRef<Terminal | null>(null);
@@ -84,6 +86,9 @@ function XtermTerminal({ session, theme, daemonReady }: TerminalPaneProps) {
 			fontFamily: 'Menlo, Monaco, Consolas, "Liberation Mono", "Courier New", monospace',
 			fontSize: 13,
 			lineHeight: 1.35,
+			// Zellij owns scrollback inside the attached pane; keeping xterm
+			// scrollback creates a dead scrollbar beside the alt-buffer app.
+			scrollback: 0,
 			theme: terminalTheme(theme),
 		});
 		terminalRef.current = terminal;
@@ -112,7 +117,20 @@ function XtermTerminal({ session, theme, daemonReady }: TerminalPaneProps) {
 		if (session?.terminalHandleId) {
 			rafId = requestAnimationFrame(() => {
 				fitTerminal();
-				detach = attach(terminal);
+				const attachable: AttachableTerminal = {
+					get cols() {
+						return terminal.cols;
+					},
+					get rows() {
+						return terminal.rows;
+					},
+					write: (data) => terminal.write(data),
+					writeln: (line) => terminal.writeln(line),
+					clear: () => terminal.write(CLEAR_SEQUENCE),
+					onData: (listener) => terminal.onData(listener),
+					onResize: (listener) => terminal.onResize(listener),
+				};
+				detach = attach(attachable);
 			});
 		} else {
 			rafId = requestAnimationFrame(fitTerminal);

frontend/src/renderer/hooks/useTerminalSession.test.tsx

@@ -79,7 +79,7 @@ function createFakeMux(): FakeMux {
 
 type FakeTerminal = AttachableTerminal & {
 	lines: string[];
-	resets: number;
+	clears: number;
 	typeKeys(data: string): void;
 	emitResize(cols: number, rows: number): void;
 };
@@ -91,11 +91,11 @@ function createFakeTerminal(): FakeTerminal {
 		cols: 80,
 		rows: 24,
 		lines: [],
-		resets: 0,
+		clears: 0,
 		write: (bytes) => terminal.lines.push(new TextDecoder().decode(bytes)),
 		writeln: (line) => terminal.lines.push(line),
-		reset: () => {
+		clear: () => {
-			terminal.resets += 1;
+			terminal.clears += 1;
 		},
 		onData: (listener) => {
 			dataListeners.add(listener);
@@ -189,7 +189,7 @@ describe("useTerminalSession", () => {
 		expect(muxes).toHaveLength(1);
 	});
 
-	it("reattaches with a fresh mux after a socket drop, resetting the stale screen", () => {
+	it("reattaches with a fresh mux after a socket drop, clearing the stale screen", () => {
 		const { view, terminal, muxes } = setup();
 		act(() => muxes[0].emitOpened("handle-1"));
 		act(() => muxes[0].emitConnection("closed"));
@@ -197,7 +197,7 @@ describe("useTerminalSession", () => {
 		act(() => void vi.advanceTimersByTime(500));
 		expect(muxes).toHaveLength(2);
 		expect(muxes[0].disposed).toBe(true);
-		expect(terminal.resets).toBe(1); // the server replays the output ring on open
+		expect(terminal.clears).toBe(1); // the server replays the output ring on open
 		expect(muxes[1].opens).toEqual([["handle-1", 80, 24]]);
 		act(() => muxes[1].emitOpened("handle-1"));
 		expect(view.result.current.state).toBe("attached");

frontend/src/renderer/hooks/useTerminalSession.ts

@@ -23,7 +23,11 @@ export type AttachableTerminal = {
 	rows: number;
 	write: (data: Uint8Array) => void;
 	writeln: (line: string) => void;
-	reset: () => void;
+	/**
+	 * Erase screen + scrollback while preserving terminal modes. A full reset
+	 * drops zellij mouse tracking, so wheel scroll stops after reconnect.
+	 */
+	clear: () => void;
 	onData: (listener: (data: string) => void) => { dispose: () => void };
 	onResize: (listener: (size: { cols: number; rows: number }) => void) => { dispose: () => void };
 };
@@ -154,8 +158,9 @@ export function useTerminalSession(session: WorkspaceSession | undefined, option
 			terminal.writeln(`\x1b[2mAttaching to ${sessionRef.current?.title ?? handle}…\x1b[0m`);
 		} else {
 			// The server replays the recent-output ring on open (backend
-			// internal/terminal/ring.go); drop the stale screen so it isn't doubled.
+			// internal/terminal/ring.go); clear the stale screen so it isn't doubled.
-			terminal.reset();
+			// Screen-clear only, never reset(): RIS wipes zellij's mouse mode.
+			terminal.clear();
 		}
 		r.firstAttach = false;