fix(tui): stop swallowing escape during cell size detection closes #2661

packages/tui/CHANGELOG.md

@@ -2,6 +2,10 @@
 
 ## [Unreleased]
 
+### Fixed
+
+- Fixed TUI cell size response handling to consume only exact `CSI 6 ; height ; width t` replies, so bare `Escape` is no longer swallowed while waiting for terminal image metadata ([#2661](https://github.com/badlogic/pi-mono/issues/2661))
+
 ## [0.63.2] - 2026-03-29
 
 ## [0.63.1] - 2026-03-27

packages/tui/src/tui.ts

@@ -223,8 +223,6 @@ export class TUI extends Container {
 	private renderRequested = false;
 	private cursorRow = 0; // Logical cursor row (end of rendered content)
 	private hardwareCursorRow = 0; // Actual terminal cursor row (may differ due to IME positioning)
-	private inputBuffer = ""; // Buffer for parsing terminal responses
-	private cellSizeQueryPending = false;
 	private showHardwareCursor = process.env.PI_HARDWARE_CURSOR === "1";
 	private clearOnShrink = process.env.PI_CLEAR_ON_SHRINK === "1"; // Clear empty rows when content shrinks (default: off)
 	private maxLinesRendered = 0; // Track terminal's working area (max lines ever rendered)
@@ -439,7 +437,6 @@ export class TUI extends Container {
 		}
 		// Query terminal for cell size in pixels: CSI 16 t
 		// Response format: CSI 6 ; height ; width t
-		this.cellSizeQueryPending = true;
 		this.terminal.write("\x1b[16t");
 	}
 
@@ -497,12 +494,9 @@ export class TUI extends Container {
 			data = current;
 		}
 
-		// If we're waiting for cell size response, buffer input and parse
+		// Consume terminal cell size responses without blocking unrelated input.
-		if (this.cellSizeQueryPending) {
+		if (this.consumeCellSizeResponse(data)) {
-			this.inputBuffer += data;
+			return;
-			const filtered = this.parseCellSizeResponse();
-			if (filtered.length === 0) return;
-			data = filtered;
 		}
 
 		// Global debug key handler (Shift+Ctrl+D)
@@ -537,46 +531,24 @@ export class TUI extends Container {
 		}
 	}
 
-	private parseCellSizeResponse(): string {
+	private consumeCellSizeResponse(data: string): boolean {
 		// Response format: ESC [ 6 ; height ; width t
-		// Match the response pattern
+		const match = data.match(/^\x1b\[6;(\d+);(\d+)t$/);
-		const responsePattern = /\x1b\[6;(\d+);(\d+)t/;
+		if (!match) {
-		const match = this.inputBuffer.match(responsePattern);
+			return false;
+		}
 
-		if (match) {
 		const heightPx = parseInt(match[1], 10);
 		const widthPx = parseInt(match[2], 10);
+		if (heightPx <= 0 || widthPx <= 0) {
+			return true;
+		}
 
-			if (heightPx > 0 && widthPx > 0) {
 		setCellDimensions({ widthPx, heightPx });
-				// Invalidate all components so images re-render with correct dimensions
+		// Invalidate all components so images re-render with correct dimensions.
 		this.invalidate();
 		this.requestRender();
-			}
+		return true;
-
-			// Remove the response from buffer
-			this.inputBuffer = this.inputBuffer.replace(responsePattern, "");
-			this.cellSizeQueryPending = false;
-		}
-
-		// Check if we have a partial cell size response starting (wait for more data)
-		// Patterns that could be incomplete cell size response: \x1b, \x1b[, \x1b[6, \x1b[6;...(no t yet)
-		const partialCellSizePattern = /\x1b(\[6?;?[\d;]*)?$/;
-		if (partialCellSizePattern.test(this.inputBuffer)) {
-			// Check if it's actually a complete different escape sequence (ends with a letter)
-			// Cell size response ends with 't', Kitty keyboard ends with 'u', arrows end with A-D, etc.
-			const lastChar = this.inputBuffer[this.inputBuffer.length - 1];
-			if (!/[a-zA-Z~]/.test(lastChar)) {
-				// Doesn't end with a terminator, might be incomplete - wait for more
-				return "";
-			}
-		}
-
-		// No cell size response found, return buffered data as user input
-		const result = this.inputBuffer;
-		this.inputBuffer = "";
-		this.cellSizeQueryPending = false; // Give up waiting
-		return result;
 	}
 
 	/**

packages/tui/test/tui-cell-size-input.test.ts

@@ -0,0 +1,81 @@
+import assert from "node:assert";
+import { describe, it } from "node:test";
+import { getCellDimensions, resetCapabilitiesCache, setCellDimensions } from "../src/terminal-image.js";
+import { type Component, TUI } from "../src/tui.js";
+import { VirtualTerminal } from "./virtual-terminal.js";
+
+class InputRecorder implements Component {
+	readonly inputs: string[] = [];
+
+	render(): string[] {
+		return [""];
+	}
+
+	handleInput(data: string): void {
+		this.inputs.push(data);
+	}
+
+	invalidate(): void {}
+}
+
+function withImageTerminal<T>(fn: () => T): T {
+	const prevTermProgram = process.env.TERM_PROGRAM;
+	const prevTerm = process.env.TERM;
+	const prevGhosttyResourcesDir = process.env.GHOSTTY_RESOURCES_DIR;
+
+	process.env.TERM_PROGRAM = "ghostty";
+	delete process.env.TERM;
+	delete process.env.GHOSTTY_RESOURCES_DIR;
+	resetCapabilitiesCache();
+
+	try {
+		return fn();
+	} finally {
+		if (prevTermProgram === undefined) delete process.env.TERM_PROGRAM;
+		else process.env.TERM_PROGRAM = prevTermProgram;
+		if (prevTerm === undefined) delete process.env.TERM;
+		else process.env.TERM = prevTerm;
+		if (prevGhosttyResourcesDir === undefined) delete process.env.GHOSTTY_RESOURCES_DIR;
+		else process.env.GHOSTTY_RESOURCES_DIR = prevGhosttyResourcesDir;
+		resetCapabilitiesCache();
+	}
+}
+
+describe("TUI cell size responses", () => {
+	it("forwards bare escape even when a cell size query was sent at startup", () => {
+		withImageTerminal(() => {
+			const terminal = new VirtualTerminal(80, 24);
+			const tui = new TUI(terminal);
+			const recorder = new InputRecorder();
+
+			tui.setFocus(recorder);
+			tui.start();
+
+			terminal.sendInput("\x1b");
+
+			assert.deepStrictEqual(recorder.inputs, ["\x1b"]);
+			tui.stop();
+		});
+	});
+
+	it("consumes cell size responses and still forwards later user input", () => {
+		withImageTerminal(() => {
+			setCellDimensions({ widthPx: 9, heightPx: 18 });
+
+			const terminal = new VirtualTerminal(80, 24);
+			const tui = new TUI(terminal);
+			const recorder = new InputRecorder();
+
+			tui.setFocus(recorder);
+			tui.start();
+
+			terminal.sendInput("\x1b[6;20;10t");
+			assert.deepStrictEqual(recorder.inputs, []);
+			assert.deepStrictEqual(getCellDimensions(), { widthPx: 10, heightPx: 20 });
+
+			terminal.sendInput("q");
+			assert.deepStrictEqual(recorder.inputs, ["q"]);
+			tui.stop();
+		});
+	});
+});