fix(tui): skip Kitty query inside Zellij\n\nfixes badlogic#3163

Author: badlogic

packages/coding-agent/CHANGELOG.md

@@ -4,6 +4,7 @@
 
 ### Fixed
 
+- Fixed Alt keybindings inside Zellij by skipping the Kitty keyboard protocol query there and enabling xterm `modifyOtherKeys` mode 2 directly ([#3163](https://github.com/badlogic/pi-mono/issues/3163))
 - Fixed `/scoped-models` reordering to propagate into the `/model` scoped tab, preserving the user-defined scoped model order instead of re-sorting it ([#3217](https://github.com/badlogic/pi-mono/issues/3217))
 - Fixed `session_shutdown` to fire on `SIGHUP` and `SIGTERM` in interactive, print, and RPC modes so extensions can run shutdown cleanup on those signal-driven exits ([#3212](https://github.com/badlogic/pi-mono/issues/3212))
 - Fixed screenshot path parsing to handle lower case am/pm in macOS screenshot filenames ([#3194](https://github.com/badlogic/pi-mono/pull/3194) by [@jay-aye-see-kay](https://github.com/jay-aye-see-kay))

packages/coding-agent/docs/terminal-setup.md

@@ -32,6 +32,12 @@ If you want `Shift+Enter` to keep working in tmux via that remap, add `ctrl+j` t
 }
 ```
 
+## Zellij
+
+Pi detects Zellij automatically and skips the Kitty keyboard protocol query there.
+Zellij currently forwards that query to the outer terminal but still sends Alt as legacy ESC-prefixed sequences, which can break Alt keybindings if applications enable Kitty mode.
+Pi uses xterm `modifyOtherKeys` mode 2 inside Zellij instead, so no extra Zellij config is required.
+
 ## WezTerm
 
 Create `~/.wezterm.lua`:

packages/tui/CHANGELOG.md

@@ -2,6 +2,10 @@
 
 ## [Unreleased]
 
+### Fixed
+
+- Fixed Alt keybindings inside Zellij by skipping the Kitty keyboard protocol query there and enabling xterm `modifyOtherKeys` mode 2 directly ([#3163](https://github.com/badlogic/pi-mono/issues/3163))
+
 ## [0.67.2] - 2026-04-14
 
 ### Added

packages/tui/src/terminal.ts

@@ -184,6 +184,17 @@ export class ProcessTerminal implements Terminal {
 	private queryAndEnableKittyProtocol(): void {
 		this.setupStdinBuffer();
 		process.stdin.on("data", this.stdinDataHandler!);
+
+		// Zellij forwards the Kitty query to the outer terminal, which can make
+		// Pi enable its Kitty parser even though Zellij still sends Alt as
+		// legacy ESC-prefixed sequences. Skip the Kitty query there and use
+		// modifyOtherKeys directly instead.
+		if (process.env.ZELLIJ) {
+			process.stdout.write("\x1b[>4;2m");
+			this._modifyOtherKeysActive = true;
+			return;
+		}
+
 		process.stdout.write("\x1b[?u");
 		setTimeout(() => {
 			if (!this._kittyProtocolActive && !this._modifyOtherKeysActive) {

packages/tui/test/terminal.test.ts

@@ -0,0 +1,76 @@
+import assert from "node:assert";
+import { describe, it } from "node:test";
+import { ProcessTerminal } from "../src/terminal.js";
+
+function withEnv(name: string, value: string | undefined, fn: () => void): void {
+	const previous = process.env[name];
+	if (value === undefined) delete process.env[name];
+	else process.env[name] = value;
+	try {
+		fn();
+	} finally {
+		if (previous === undefined) delete process.env[name];
+		else process.env[name] = previous;
+	}
+}
+
+describe("ProcessTerminal", () => {
+	it("should skip the Kitty query inside Zellij and enable modifyOtherKeys immediately", () => {
+		const terminal = new ProcessTerminal();
+		const writes: string[] = [];
+		const stdinOnCalls: Array<{ event: string | symbol; listener: (...args: unknown[]) => void }> = [];
+		const stdinRemoveCalls: Array<{ event: string | symbol; listener: (...args: unknown[]) => void }> = [];
+		const stdoutRemoveCalls: Array<{ event: string | symbol; listener: (...args: unknown[]) => void }> = [];
+
+		const originalStdoutWrite = process.stdout.write;
+		const originalStdinOn = process.stdin.on;
+		const originalStdinRemoveListener = process.stdin.removeListener;
+		const originalStdinPause = process.stdin.pause;
+		const originalStdoutRemoveListener = process.stdout.removeListener;
+
+		process.stdout.write = ((chunk: string | Uint8Array) => {
+			writes.push(typeof chunk === "string" ? chunk : Buffer.from(chunk).toString("utf8"));
+			return true;
+		}) as typeof process.stdout.write;
+		process.stdin.on = ((event: string | symbol, listener: (...args: unknown[]) => void) => {
+			stdinOnCalls.push({ event, listener });
+			return process.stdin;
+		}) as typeof process.stdin.on;
+		process.stdin.removeListener = ((event: string | symbol, listener: (...args: unknown[]) => void) => {
+			stdinRemoveCalls.push({ event, listener });
+			return process.stdin;
+		}) as typeof process.stdin.removeListener;
+		process.stdin.pause = (() => process.stdin) as typeof process.stdin.pause;
+		process.stdout.removeListener = ((event: string | symbol, listener: (...args: unknown[]) => void) => {
+			stdoutRemoveCalls.push({ event, listener });
+			return process.stdout;
+		}) as typeof process.stdout.removeListener;
+
+		try {
+			withEnv("ZELLIJ", "1", () => {
+				(
+					terminal as unknown as {
+						queryAndEnableKittyProtocol(): void;
+					}
+				).queryAndEnableKittyProtocol();
+			});
+
+			assert.deepStrictEqual(writes, ["\x1b[>4;2m"]);
+			assert.strictEqual(stdinOnCalls.length, 1);
+			assert.strictEqual(stdinOnCalls[0]?.event, "data");
+
+			terminal.stop();
+
+			assert.deepStrictEqual(writes, ["\x1b[>4;2m", "\x1b[?2004l", "\x1b[>4;0m"]);
+			assert.strictEqual(stdinRemoveCalls.length, 1);
+			assert.strictEqual(stdinRemoveCalls[0]?.event, "data");
+			assert.strictEqual(stdoutRemoveCalls.length, 0);
+		} finally {
+			process.stdout.write = originalStdoutWrite;
+			process.stdin.on = originalStdinOn;
+			process.stdin.removeListener = originalStdinRemoveListener;
+			process.stdin.pause = originalStdinPause;
+			process.stdout.removeListener = originalStdoutRemoveListener;
+		}
+	});
+});