From ffbc1f8f6e37d3a0f84a76d6ebecf7301676f7e5 Mon Sep 17 00:00:00 2001
From: Vasanthdev2004 <vasanth.dev2004@gmail.com>
Date: Thu, 2 Apr 2026 10:05:16 +0530
Subject: [PATCH] fix: support CSI-u printable input on Windows

---
 src/ink/parse-keypress.test.ts | 49 ++++++++++++++++++++++++++++++++++
 src/ink/parse-keypress.ts      | 28 ++++++++++++++++++-
 2 files changed, 76 insertions(+), 1 deletion(-)
 create mode 100644 src/ink/parse-keypress.test.ts

diff --git a/src/ink/parse-keypress.test.ts b/src/ink/parse-keypress.test.ts
new file mode 100644
index 00000000..23035286
--- /dev/null
+++ b/src/ink/parse-keypress.test.ts
@@ -0,0 +1,49 @@
+import { expect, test } from 'bun:test'
+
+import {
+  INITIAL_STATE,
+  parseMultipleKeypresses,
+  type ParsedKey,
+} from './parse-keypress.ts'
+import { InputEvent } from './events/input-event.ts'
+
+function parseInputEvent(sequence: string): InputEvent {
+  const [items] = parseMultipleKeypresses(INITIAL_STATE, sequence)
+
+  expect(items).toHaveLength(1)
+
+  const item = items[0]
+  expect(item?.kind).toBe('key')
+
+  return new InputEvent(item as ParsedKey)
+}
+
+test('treats CSI-u modifier 0 as unmodified printable input', () => {
+  const event = parseInputEvent('\x1b[47;0u')
+
+  expect(event.input).toBe('/')
+  expect(event.key.ctrl).toBe(false)
+  expect(event.key.meta).toBe(false)
+  expect(event.key.shift).toBe(false)
+  expect(event.key.super).toBe(false)
+})
+
+test('preserves printable Unicode CSI-u input', () => {
+  const event = parseInputEvent('\x1b[231u')
+
+  expect(event.input).toBe('ç')
+  expect(event.key.ctrl).toBe(false)
+  expect(event.key.meta).toBe(false)
+  expect(event.key.shift).toBe(false)
+  expect(event.key.super).toBe(false)
+})
+
+test('preserves printable Unicode CSI-u input with explicit modifier 0', () => {
+  const event = parseInputEvent('\x1b[231;0u')
+
+  expect(event.input).toBe('ç')
+  expect(event.key.ctrl).toBe(false)
+  expect(event.key.meta).toBe(false)
+  expect(event.key.shift).toBe(false)
+  expect(event.key.super).toBe(false)
+})
diff --git a/src/ink/parse-keypress.ts b/src/ink/parse-keypress.ts
index a7e43adc..ac4162fd 100644
--- a/src/ink/parse-keypress.ts
+++ b/src/ink/parse-keypress.ts
@@ -468,7 +468,10 @@ function decodeModifier(modifier: number): {
   ctrl: boolean
   super: boolean
 } {
-  const m = modifier - 1
+  // Some Windows VT stacks use 0 instead of 1 for an unmodified CSI-u key.
+  // Clamp to the protocol default so plain printable keys don't look like
+  // ctrl+meta+shift+super all at once.
+  const m = Math.max(modifier, 1) - 1
   return {
     shift: !!(m & 1),
     meta: !!(m & 2),
@@ -477,6 +480,14 @@ function decodeModifier(modifier: number): {
   }
 }
 
+function isPrivateUseCodepoint(codepoint: number): boolean {
+  return (
+    (codepoint >= 0xe000 && codepoint <= 0xf8ff) ||
+    (codepoint >= 0xf0000 && codepoint <= 0xffffd) ||
+    (codepoint >= 0x100000 && codepoint <= 0x10fffd)
+  )
+}
+
 /**
  * Map keycode to key name for modifyOtherKeys/CSI u sequences.
  * Handles both ASCII keycodes and Kitty keyboard protocol functional keys.
@@ -536,6 +547,21 @@ function keycodeToName(keycode: number): string | undefined {
       if (keycode >= 32 && keycode <= 126) {
         return String.fromCharCode(keycode).toLowerCase()
       }
+
+      // CSI-u can carry printable Unicode codepoints directly on some
+      // Windows terminals and keyboard layouts. Keep kitty's private-use
+      // functional key range excluded so special keys still stay non-text.
+      if (
+        keycode > 0x1f &&
+        keycode !== 0x7f &&
+        (keycode < 0x80 || keycode > 0x9f) &&
+        keycode <= 0x10ffff &&
+        (keycode < 0xd800 || keycode > 0xdfff) &&
+        !isPrivateUseCodepoint(keycode)
+      ) {
+        return String.fromCodePoint(keycode)
+      }
+
       return undefined
   }
 }