fix(tui): deduplicate kitty printable input

closes #3780

packages/tui/CHANGELOG.md

@@ -2,6 +2,10 @@
 
 ## [Unreleased]
 
+### Fixed
+
+- Fixed duplicate printable characters from Kitty keyboard protocol CSI-u plus raw character input on layouts such as Italian ([#3780](https://github.com/badlogic/pi-mono/issues/3780))
+
 ## [0.70.2] - 2026-04-24
 
 ## [0.70.1] - 2026-04-24

packages/tui/src/stdin-buffer.ts

@@ -181,6 +181,14 @@ function isCompleteApcSequence(data: string): "complete" | "incomplete" {
 /**
  * Split accumulated buffer into complete sequences
  */
+function parseUnmodifiedKittyPrintableCodepoint(sequence: string): number | undefined {
+	const match = sequence.match(/^\x1b\[(\d+)(?::\d*)?(?::\d+)?u$/);
+	if (!match) return undefined;
+
+	const codepoint = parseInt(match[1]!, 10);
+	return codepoint >= 32 ? codepoint : undefined;
+}
+
 function extractCompleteSequences(buffer: string): { sequences: string[]; remainder: string } {
 	const sequences: string[] = [];
 	let pos = 0;
@@ -246,6 +254,7 @@ export class StdinBuffer extends EventEmitter<StdinBufferEventMap> {
 	private readonly timeoutMs: number;
 	private pasteMode: boolean = false;
 	private pasteBuffer: string = "";
+	private pendingKittyPrintableCodepoint: number | undefined;
 
 	constructor(options: StdinBufferOptions = {}) {
 		super();
@@ -274,7 +283,7 @@ export class StdinBuffer extends EventEmitter<StdinBufferEventMap> {
 		}
 
 		if (str.length === 0 && this.buffer.length === 0) {
-			this.emit("data", "");
+			this.emitDataSequence("");
 			return;
 		}
 
@@ -291,6 +300,7 @@ export class StdinBuffer extends EventEmitter<StdinBufferEventMap> {
 
 				this.pasteMode = false;
 				this.pasteBuffer = "";
+				this.pendingKittyPrintableCodepoint = undefined;
 
 				this.emit("paste", pastedContent);
 
@@ -307,10 +317,11 @@ export class StdinBuffer extends EventEmitter<StdinBufferEventMap> {
 				const beforePaste = this.buffer.slice(0, startIndex);
 				const result = extractCompleteSequences(beforePaste);
 				for (const sequence of result.sequences) {
-					this.emit("data", sequence);
+					this.emitDataSequence(sequence);
 				}
 			}
 
+			this.pendingKittyPrintableCodepoint = undefined;
 			this.buffer = this.buffer.slice(startIndex + BRACKETED_PASTE_START.length);
 			this.pasteMode = true;
 			this.pasteBuffer = this.buffer;
@@ -323,6 +334,7 @@ export class StdinBuffer extends EventEmitter<StdinBufferEventMap> {
 
 				this.pasteMode = false;
 				this.pasteBuffer = "";
+				this.pendingKittyPrintableCodepoint = undefined;
 
 				this.emit("paste", pastedContent);
 
@@ -337,7 +349,7 @@ export class StdinBuffer extends EventEmitter<StdinBufferEventMap> {
 		this.buffer = result.remainder;
 
 		for (const sequence of result.sequences) {
-			this.emit("data", sequence);
+			this.emitDataSequence(sequence);
 		}
 
 		if (this.buffer.length > 0) {
@@ -345,12 +357,23 @@ export class StdinBuffer extends EventEmitter<StdinBufferEventMap> {
 				const flushed = this.flush();
 
 				for (const sequence of flushed) {
-					this.emit("data", sequence);
+					this.emitDataSequence(sequence);
 				}
 			}, this.timeoutMs);
 		}
 	}
 
+	private emitDataSequence(sequence: string): void {
+		const rawCodepoint = sequence.length === 1 ? sequence.codePointAt(0) : undefined;
+		if (rawCodepoint !== undefined && rawCodepoint === this.pendingKittyPrintableCodepoint) {
+			this.pendingKittyPrintableCodepoint = undefined;
+			return;
+		}
+
+		this.pendingKittyPrintableCodepoint = parseUnmodifiedKittyPrintableCodepoint(sequence);
+		this.emit("data", sequence);
+	}
+
 	flush(): string[] {
 		if (this.timeout) {
 			clearTimeout(this.timeout);
@@ -363,6 +386,7 @@ export class StdinBuffer extends EventEmitter<StdinBufferEventMap> {
 
 		const sequences = [this.buffer];
 		this.buffer = "";
+		this.pendingKittyPrintableCodepoint = undefined;
 		return sequences;
 	}
 
@@ -374,6 +398,7 @@ export class StdinBuffer extends EventEmitter<StdinBufferEventMap> {
 		this.buffer = "";
 		this.pasteMode = false;
 		this.pasteBuffer = "";
+		this.pendingKittyPrintableCodepoint = undefined;
 	}
 
 	getBuffer(): string {

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

@@ -204,9 +204,25 @@ describe("StdinBuffer", () => {
 			assert.deepStrictEqual(emittedSequences, ["a", "\x1b[97;1:3u"]);
 		});
 
-		it("should handle Kitty sequence followed by plain characters", () => {
+		it("should drop raw duplicate character after matching Kitty printable sequence", () => {
-			processInput("\x1b[97ua");
+			processInput("\x1b[224uà");
-			assert.deepStrictEqual(emittedSequences, ["\x1b[97u", "a"]);
+			assert.deepStrictEqual(emittedSequences, ["\x1b[224u"]);
+		});
+
+		it("should drop raw duplicate character after matching Kitty printable sequence across chunks", () => {
+			processInput("\x1b[64u");
+			processInput("@");
+			assert.deepStrictEqual(emittedSequences, ["\x1b[64u"]);
+		});
+
+		it("should keep non-matching plain character after Kitty printable sequence", () => {
+			processInput("\x1b[97ub");
+			assert.deepStrictEqual(emittedSequences, ["\x1b[97u", "b"]);
+		});
+
+		it("should keep raw character after modified Kitty printable sequence", () => {
+			processInput("\x1b[64;3u@");
+			assert.deepStrictEqual(emittedSequences, ["\x1b[64;3u", "@"]);
 		});
 
 		it("should handle rapid typing simulation with Kitty protocol", () => {