fix(tui): apply PI_TUI_ESC_TIMEOUT only to lone ESC

Split StdinBuffer's incomplete-sequence wait from the lone-ESC wait so SSH and PI_TUI_ESC_TIMEOUT can reassemble split Alt+Enter without delaying Escape or mouse/CSI buffering.

packages/coding-agent/docs/environment-variables.md

@@ -87,7 +87,7 @@ These variables are read by Pi itself:
 | `PI_CACHE_RETENTION` | Set to `long` for extended provider prompt caching where supported |
 | `PI_SHARE_VIEWER_URL` | Override the base URL used by `/share` |
 | `PI_HARDWARE_CURSOR` | Set to `1` to show the hardware cursor; see [Terminal setup](terminal-setup.md) |
-| `PI_TUI_ESC_TIMEOUT` | Escape-sequence timeout in milliseconds; defaults to `100` over SSH and `10` otherwise. Increase if Alt-key input is misread as Escape |
+| `PI_TUI_ESC_TIMEOUT` | How long to wait after a lone ESC before treating it as Escape, in milliseconds; defaults to `100` over SSH and `10` otherwise. Increase if Alt-key input is misread as Escape |
 | `VISUAL`, `EDITOR` | External editor fallback when `externalEditor` is unset |
 | `HTTP_PROXY`, `HTTPS_PROXY` | Proxy outbound HTTP requests |
 

packages/tui/src/stdin-buffer.ts

@@ -20,7 +20,8 @@
 import { EventEmitter } from "events";
 
 const ESC = "\x1b";
-const LONE_ESCAPE_TIMEOUT_MS = 10;
+const DEFAULT_SEQUENCE_TIMEOUT_MS = 50;
+const DEFAULT_ESCAPE_TIMEOUT_MS = 10;
 const BRACKETED_PASTE_START = "\x1b[200~";
 const BRACKETED_PASTE_END = "\x1b[201~";
 
@@ -257,10 +258,15 @@ function extractCompleteSequences(buffer: string): { sequences: string[]; remain
 
 export type StdinBufferOptions = {
 	/**
-	 * Maximum time to wait for sequence completion (default: 50ms).
-	 * A lone Escape uses at most 10ms to preserve keyboard responsiveness.
+	 * Maximum time to wait for an incomplete sequence such as CSI or mouse
+	 * (default: 50ms).
 	 */
 	timeout?: number;
+	/**
+	 * Maximum time to wait after a lone ESC before treating it as Escape
+	 * (default: 10ms). Increase for high-latency Alt+key input (SSH).
+	 */
+	escapeTimeout?: number;
 };
 
 export type StdinBufferEventMap = {
@@ -276,13 +282,15 @@ export class StdinBuffer extends EventEmitter<StdinBufferEventMap> {
 	private buffer: string = "";
 	private timeout: ReturnType<typeof setTimeout> | null = null;
 	private readonly timeoutMs: number;
+	private readonly escapeTimeoutMs: number;
 	private pasteMode: boolean = false;
 	private pasteBuffer: string = "";
 	private pendingKittyPrintableCodepoint: number | undefined;
 
 	constructor(options: StdinBufferOptions = {}) {
 		super();
-		this.timeoutMs = options.timeout ?? 50;
+		this.timeoutMs = options.timeout ?? DEFAULT_SEQUENCE_TIMEOUT_MS;
+		this.escapeTimeoutMs = options.escapeTimeout ?? DEFAULT_ESCAPE_TIMEOUT_MS;
 	}
 
 	public process(data: string | Buffer): void {
@@ -377,7 +385,7 @@ export class StdinBuffer extends EventEmitter<StdinBufferEventMap> {
 		}
 
 		if (this.buffer.length > 0) {
-			const timeoutMs = this.buffer === ESC ? Math.min(this.timeoutMs, LONE_ESCAPE_TIMEOUT_MS) : this.timeoutMs;
+			const timeoutMs = this.buffer === ESC ? this.escapeTimeoutMs : this.timeoutMs;
 			this.timeout = setTimeout(() => {
 				const flushed = this.flush();
 

packages/tui/src/terminal.ts

@@ -202,7 +202,7 @@ export class ProcessTerminal implements Terminal {
 	 * to handle the case where the response arrives split across multiple events.
 	 */
 	private setupStdinBuffer(): void {
-		this.stdinBuffer = new StdinBuffer({ timeout: resolveEscapeTimeoutMs() });
+		this.stdinBuffer = new StdinBuffer({ escapeTimeout: resolveEscapeTimeoutMs() });
 
 		// Forward individual sequences to the input handler
 		this.stdinBuffer.on("data", (sequence) => {

packages/tui/test/stdin-buffer.test.ts

@@ -149,6 +149,21 @@ describe("StdinBuffer", () => {
 		});
 
 		it("should merge ESC + CR split across chunks within a larger timeout", async () => {
+			buffer = new StdinBuffer({ escapeTimeout: 100 });
+			emittedSequences = [];
+			buffer.on("data", (sequence) => {
+				emittedSequences.push(sequence);
+			});
+
+			processInput("\x1b");
+			await wait(20); // > 10ms default escapeTimeout, < 100ms configured escapeTimeout
+			processInput("\r");
+
+			assert.deepStrictEqual(emittedSequences, ["\x1b\r"]);
+			assert.equal(matchesKey(emittedSequences[0] ?? "", "alt+enter"), true);
+		});
+
+		it("does not apply the sequence timeout to a lone ESC", async () => {
 			buffer = new StdinBuffer({ timeout: 100 });
 			emittedSequences = [];
 			buffer.on("data", (sequence) => {
@@ -156,11 +171,11 @@ describe("StdinBuffer", () => {
 			});
 
 			processInput("\x1b");
-			await wait(20); // > 10ms old default, < 100ms configured timeout
+			await wait(20);
 			processInput("\r");
 
-			assert.deepStrictEqual(emittedSequences, ["\x1b\r"]);
-			assert.equal(matchesKey(emittedSequences[0] ?? "", "alt+enter"), true);
+			assert.deepStrictEqual(emittedSequences, ["\x1b", "\r"]);
+			assert.equal(matchesKey(emittedSequences[0] ?? "", "escape"), true);
 		});
 
 		it("keeps fragmented mouse sequences buffered across delayed chunks by default", async () => {

packages/tui/test/terminal.test.ts

@@ -223,7 +223,7 @@ describe("ProcessTerminal Kitty keyboard protocol negotiation", () => {
 		const harness = setupNegotiation();
 		try {
 			harness.send("\x1b[");
-			mock.timers.tick(resolveEscapeTimeoutMs());
+			mock.timers.tick(50); // StdinBuffer sequence timeout, not the lone-ESC timeout
 
 			assert.equal(harness.getInput(), undefined);