Fix iOS TextField cursor placement on CJK punctuation

compose/foundation/foundation/src/skikoMain/kotlin/androidx/compose/foundation/text/StringHelpers.skiko.kt

@@ -252,6 +252,31 @@ internal fun String.isWhitespaceOrPunctuation(offset: Int): Boolean {
     return codePoint.isPunctuation() || codePoint.isWhitespace()
 }
 
+/**
+ * Returns whether iOS cursor placement should remain at the character boundary instead of
+ * applying Cupertino's Latin word adjustment. This helper lives in `skikoMain` alongside the
+ * shared Cupertino cursor adjustment, but its production callers are iOS-only.
+ */
+internal fun String.requiresCharacterLevelCursorPlacement(index: Int): Boolean {
+    if (index !in indices) return false
+
+    return when (codePointAt(index)) {
+        in 0x2E80..0x312F, // CJK radicals, punctuation, Hiragana, Katakana, and Bopomofo.
+        in 0x3130..0x318F, // Hangul compatibility jamo.
+        in 0x31A0..0x31FF, // Bopomofo extended and Katakana phonetic extensions.
+        in 0x3400..0x4DBF, // CJK unified ideographs extension A.
+        in 0x4E00..0x9FFF, // CJK unified ideographs.
+        in 0xAC00..0xD7AF, // Hangul syllables and jamo extensions.
+        in 0xF900..0xFAFF, // CJK compatibility ideographs.
+        in 0xFE30..0xFE4F, // CJK compatibility forms.
+        in 0xFF00..0xFFEF, // Half-width and full-width forms.
+        in 0x20000..0x3134F, // Supplementary CJK ideographs.
+        -> true
+
+        else -> false
+    }
+}
+
 /**
  * Returns the midpoint position in the string considering Unicode symbols.
  *

compose/foundation/foundation/src/skikoMain/kotlin/androidx/compose/foundation/text/TextFieldDelegate.skiko.kt

@@ -93,6 +93,8 @@ internal fun determineCursorDesiredOffset(
             textLayoutResult.getLineEnd(lineNumber)
         }
 
+        currentText.requiresCharacterLevelCursorPlacement(offset) -> offset
+
         currentText.isWhitespaceOrPunctuation(offset) -> findNextNonWhitespaceSymbolsSubsequenceStartOffset(
             offset,
             currentText
@@ -131,4 +133,4 @@ private fun isRightEdgeTapped(textLayoutResult: TextLayoutResult, caretOffset: I
     val lineNumber = textLayoutResult.getLineForOffset(caretOffset)
     val lineEndOffset = textLayoutResult.getLineEnd(lineNumber)
     return lineEndOffset == caretOffset
-}
+}

compose/foundation/foundation/src/skikoTest/kotlin/androidx/compose/foundation/text/CharacterLevelCursorPlacementTest.kt

@@ -0,0 +1,55 @@
+/*
+ * Copyright 2026 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package androidx.compose.foundation.text
+
+import kotlin.test.Test
+import kotlin.test.assertFalse
+import kotlin.test.assertTrue
+
+class CharacterLevelCursorPlacementTest {
+    @Test
+    fun cjkPunctuation_requiresCharacterLevelCursorPlacement() {
+        val text = "a\u3001\u3002\uFF01z"
+
+        assertTrue(text.requiresCharacterLevelCursorPlacement(1))
+        assertTrue(text.requiresCharacterLevelCursorPlacement(2))
+        assertTrue(text.requiresCharacterLevelCursorPlacement(3))
+    }
+
+    @Test
+    fun cjkScriptsAndFullWidthForms_requireCharacterLevelCursorPlacement() {
+        assertTrue("\u4E2D".requiresCharacterLevelCursorPlacement(0))
+        assertTrue("\u3042".requiresCharacterLevelCursorPlacement(0))
+        assertTrue("\u30A2".requiresCharacterLevelCursorPlacement(0))
+        assertTrue("\uD55C".requiresCharacterLevelCursorPlacement(0))
+        assertTrue("\uFF21".requiresCharacterLevelCursorPlacement(0))
+        assertTrue("\uD840\uDC00".requiresCharacterLevelCursorPlacement(0))
+    }
+
+    @Test
+    fun latinAsciiPunctuationAndEmoji_keepCupertinoWordPlacement() {
+        assertFalse("a".requiresCharacterLevelCursorPlacement(0))
+        assertFalse(",".requiresCharacterLevelCursorPlacement(0))
+        assertFalse("\uD83D\uDE42".requiresCharacterLevelCursorPlacement(0))
+    }
+
+    @Test
+    fun invalidIndex_doesNotRequireCharacterLevelCursorPlacement() {
+        assertFalse("\u4E2D".requiresCharacterLevelCursorPlacement(-1))
+        assertFalse("\u4E2D".requiresCharacterLevelCursorPlacement(1))
+    }
+}

compose/foundation/foundation/src/skikoTest/kotlin/androidx/compose/foundation/text/CupertinoTextFieldDelegateTest.kt

@@ -80,6 +80,21 @@ class CupertinoTextFieldDelegateTest : SkikoComposeTestBase() {
         testDetermineCursorDesiredOffset(givenOffset, desiredOffset, text)
     }
 
+    @Test
+    fun determineCursorDesiredOffset_tap_on_cjk_punctuation() {
+        val text = "tap\u3001" + "\u540E".repeat(120) + " html"
+        val punctuationOffset = text.indexOf('\u3001')
+
+        val actual =
+            determineCursorDesiredOffset(
+                offset = punctuationOffset,
+                textLayoutResult = createSimpleTextLayoutResult(text),
+                currentText = text,
+            )
+
+        assertEquals(punctuationOffset, actual)
+    }
+
     @Test
     fun determineCursorDesiredOffset_tap_in_the_first_half_of_word() {
         val givenOffset = 23
@@ -205,4 +220,4 @@ class CupertinoTextFieldDelegateTest : SkikoComposeTestBase() {
         density = defaultDensity,
         fontFamilyResolver = fontFamilyResolver
     )
-}
+}