fix(android): keep link preview metadata UTF-16 safe (#102988)

* fix(android): keep link preview metadata UTF-16 safe

* refactor(android): share UTF-16-safe truncation

---------

Co-authored-by: Peter Steinberger <steipete@gmail.com>

apps/android/app/src/main/java/ai/openclaw/app/Utf16Text.kt

@@ -0,0 +1,8 @@
+package ai.openclaw.app
+
+internal fun String.takeUtf16Safe(maxChars: Int): String {
+  if (length <= maxChars) return this
+  // Keep the code-unit cap without leaving a high surrogate at its boundary.
+  val endsOnHighSurrogate = maxChars > 0 && Character.isHighSurrogate(this[maxChars - 1])
+  return take(if (endsOnHighSurrogate) maxChars - 1 else maxChars)
+}

apps/android/app/src/main/java/ai/openclaw/app/node/DeviceNotificationListenerService.kt

@@ -4,6 +4,7 @@ import ai.openclaw.app.NotificationBurstLimiter
 import ai.openclaw.app.SecurePrefs
 import ai.openclaw.app.allowsPackage
 import ai.openclaw.app.isWithinQuietHours
+import ai.openclaw.app.takeUtf16Safe
 import android.app.Notification
 import android.app.NotificationManager
 import android.app.RemoteInput
@@ -30,17 +31,6 @@ internal fun sanitizeNotificationText(value: CharSequence?): String? {
   return normalized.takeUtf16Safe(MAX_NOTIFICATION_TEXT_CHARS).ifEmpty { null }
 }
 
-private fun String.takeUtf16Safe(maxChars: Int): String {
-  if (length <= maxChars) return this
-  val end =
-    if (maxChars > 0 && Character.isHighSurrogate(this[maxChars - 1])) {
-      maxChars - 1
-    } else {
-      maxChars
-    }
-  return take(end)
-}
-
 /**
  * Stable notification snapshot entry exposed through the Android notifications command.
  */

apps/android/app/src/main/java/ai/openclaw/app/ui/chat/ChatLinkPreview.kt

@@ -1,5 +1,6 @@
 package ai.openclaw.app.ui.chat
 
+import ai.openclaw.app.takeUtf16Safe
 import android.graphics.Bitmap
 import android.graphics.BitmapFactory
 import android.util.LruCache
@@ -524,7 +525,7 @@ private fun sanitizeMetadataText(
       .filterNot(Character::isISOControl)
       .replace(Regex("\\s+"), " ")
       .trim()
-  return sanitized.take(maxChars).takeIf(String::isNotEmpty)
+  return sanitized.takeUtf16Safe(maxChars).takeIf(String::isNotEmpty)
 }
 
 private fun findTitle(html: String): String? =

apps/android/app/src/test/java/ai/openclaw/app/ui/chat/ChatLinkPreviewTest.kt

@@ -164,6 +164,21 @@ class ChatLinkPreviewTest {
     )
   }
 
+  @Test
+  fun metadataTruncationPreservesUtf16Boundaries() {
+    val titlePrefix = "t".repeat(LINK_PREVIEW_TITLE_MAX_CHARS - 1)
+    val descriptionPrefix = "d".repeat(LINK_PREVIEW_DESCRIPTION_MAX_CHARS - 2)
+    val result =
+      parseOpenGraph(
+        "<meta property='og:title' content='$titlePrefix\uD83D\uDE80 trailing'>" +
+          "<meta property='og:description' content='$descriptionPrefix\uD83D\uDE80 trailing'>",
+        "https://example.com",
+      ) as LinkPreviewResult.Loaded
+
+    assertEquals(titlePrefix, result.metadata.title)
+    assertEquals("$descriptionPrefix\uD83D\uDE80", result.metadata.description)
+  }
+
   @Test
   fun fetchesHtmlWithoutAmbientHeaders() =
     withServer { server ->