diff --git a/packages/app/src/components/message-input.tsx b/packages/app/src/components/message-input.tsx
index 80c9e2054..fbe4cb3d5 100644
--- a/packages/app/src/components/message-input.tsx
+++ b/packages/app/src/components/message-input.tsx
@@ -115,13 +115,15 @@ export interface MessageInputRef {
 
 const MIN_INPUT_HEIGHT = 30;
 const MAX_INPUT_HEIGHT = 160;
-const IS_WEB = isWeb;
 
 type WebTextInputKeyPressEvent = NativeSyntheticEvent<
   TextInputKeyPressEventData & {
     metaKey?: boolean;
     ctrlKey?: boolean;
     shiftKey?: boolean;
+    // Web-only: present on DOM KeyboardEvent during IME composition (CJK input).
+    isComposing?: boolean;
+    keyCode?: number;
   }
 >;
 
@@ -222,7 +224,7 @@ export const MessageInput = forwardRef<MessageInputRef, MessageInputProps>(funct
   ref,
 ) {
   const { theme } = useUnistyles();
-  const buttonIconSize = IS_WEB ? theme.iconSize.md : theme.iconSize.lg;
+  const buttonIconSize = isWeb ? theme.iconSize.md : theme.iconSize.lg;
   const investigationComponentId = `MessageInput:${voiceServerId ?? "unknown-server"}:${voiceAgentId ?? "unknown-agent"}`;
   markScrollInvestigationRender(investigationComponentId);
   const toast = useToast();
@@ -293,7 +295,7 @@ export const MessageInput = forwardRef<MessageInputRef, MessageInputProps>(funct
       return false;
     },
     getNativeElement: () => {
-      if (!IS_WEB) return null;
+      if (!isWeb) return null;
       const current = textInputRef.current as (TextInput & { getNativeRef?: () => unknown }) | null;
       const native = typeof current?.getNativeRef === "function" ? current.getNativeRef() : current;
       return native instanceof HTMLElement ? native : null;
@@ -328,7 +330,7 @@ export const MessageInput = forwardRef<MessageInputRef, MessageInputProps>(funct
 
   // Autofocus on web when autoFocus is true, and re-run when focus key changes.
   useEffect(() => {
-    if (!IS_WEB || !autoFocus) return;
+    if (!isWeb || !autoFocus) return;
     return focusWithRetries({
       focus: () => textInputRef.current?.focus(),
       isFocused: () => {
@@ -371,7 +373,7 @@ export const MessageInput = forwardRef<MessageInputRef, MessageInputProps>(funct
         onChangeText(nextValue);
       }
 
-      if (IS_WEB && typeof requestAnimationFrame === "function") {
+      if (isWeb && typeof requestAnimationFrame === "function") {
         requestAnimationFrame(() => {
           measureWebInputHeight("dictation");
         });
@@ -627,13 +629,13 @@ export const MessageInput = forwardRef<MessageInputRef, MessageInputProps>(funct
   const webTextareaRef = useRef<HTMLElement | null>(null);
 
   useLayoutEffect(() => {
-    if (IS_WEB) {
+    if (isWeb) {
       webTextareaRef.current = getWebTextArea() as HTMLElement | null;
     }
   }, [getWebTextArea]);
 
   const inputScrollbar = useWebElementScrollbar(webTextareaRef, {
-    enabled: IS_WEB && inputHeight >= MAX_INPUT_HEIGHT,
+    enabled: isWeb && inputHeight >= MAX_INPUT_HEIGHT,
   });
 
   const getWebElement = useCallback((target: "root" | "wrapper"): HTMLElement | null => {
@@ -647,7 +649,7 @@ export const MessageInput = forwardRef<MessageInputRef, MessageInputProps>(funct
   }, []);
 
   useEffect(() => {
-    if (!IS_WEB || !onAddImages) {
+    if (!isWeb || !onAddImages) {
       return;
     }
 
@@ -700,7 +702,7 @@ export const MessageInput = forwardRef<MessageInputRef, MessageInputProps>(funct
   ]);
 
   useEffect(() => {
-    if (!IS_WEB || typeof ResizeObserver === "undefined") {
+    if (!isWeb || typeof ResizeObserver === "undefined") {
       return;
     }
 
@@ -754,7 +756,7 @@ export const MessageInput = forwardRef<MessageInputRef, MessageInputProps>(funct
   }, [getWebElement, getWebTextArea]);
 
   useEffect(() => {
-    if (!IS_WEB) {
+    if (!isWeb) {
       return;
     }
     const textarea = getWebTextArea() as (HTMLTextAreaElement & TextAreaHandle) | null;
@@ -792,7 +794,7 @@ export const MessageInput = forwardRef<MessageInputRef, MessageInputProps>(funct
   }, [getWebTextArea]);
 
   function measureWebInputHeight(source: string): boolean {
-    if (!IS_WEB) return false;
+    if (!isWeb) return false;
     const textarea = getWebTextArea();
     if (!textarea || typeof textarea.scrollHeight !== "number") return false;
     const scrollHeight = textarea.scrollHeight ?? 0;
@@ -846,7 +848,7 @@ export const MessageInput = forwardRef<MessageInputRef, MessageInputProps>(funct
     event: NativeSyntheticEvent<TextInputContentSizeChangeEventData>,
   ) {
     const contentHeight = event.nativeEvent.contentSize.height;
-    if (IS_WEB) {
+    if (isWeb) {
       logWebStickyBottom("composer_content_size_change", {
         reportedHeight: contentHeight,
       });
@@ -866,7 +868,7 @@ export const MessageInput = forwardRef<MessageInputRef, MessageInputProps>(funct
   function handleSelectionChange(event: NativeSyntheticEvent<TextInputSelectionChangeEventData>) {
     const start = event.nativeEvent.selection?.start ?? 0;
     const end = event.nativeEvent.selection?.end ?? start;
-    if (IS_WEB) {
+    if (isWeb) {
       const textarea = getWebTextArea();
       logWebStickyBottom("composer_selection_changed", {
         now: getDebugNow(),
@@ -880,12 +882,17 @@ export const MessageInput = forwardRef<MessageInputRef, MessageInputProps>(funct
     onSelectionChangeCallback?.({ start, end });
   }
 
-  const shouldHandleDesktopSubmit = IS_WEB;
+  const shouldHandleDesktopSubmit = isWeb;
 
   function handleDesktopKeyPress(event: WebTextInputKeyPressEvent) {
     markScrollInvestigationEvent(investigationComponentId, "keyPress");
     if (!shouldHandleDesktopSubmit) return;
 
+    // IME composition in progress (e.g. CJK input) — all key events belong to the
+    // IME, not the app. keyCode 229 is a Chromium fallback for when isComposing is
+    // cleared before the keydown fires.
+    if (event.nativeEvent.isComposing || event.nativeEvent.keyCode === 229) return;
+
     // Allow parent to intercept key events (e.g., for autocomplete navigation)
     if (onKeyPressCallback) {
       const handled = onKeyPressCallback({
@@ -935,7 +942,7 @@ export const MessageInput = forwardRef<MessageInputRef, MessageInputProps>(funct
     (nextValue: string) => {
       markScrollInvestigationEvent(investigationComponentId, "inputChange");
       onChangeText(nextValue);
-      if (IS_WEB) {
+      if (isWeb) {
         logWebStickyBottom("composer_text_changed", {
           valueLength: nextValue.length,
           lineCount: nextValue.split("\n").length,
@@ -966,7 +973,7 @@ export const MessageInput = forwardRef<MessageInputRef, MessageInputProps>(funct
                       <View
                         style={[
                           styles.removeImageButton,
-                          (hovered || !IS_WEB) && styles.removeImageButtonVisible,
+                          (hovered || !isWeb) && styles.removeImageButtonVisible,
                         ]}
                       >
                         <X size={theme.iconSize.md} color="white" />
@@ -998,7 +1005,7 @@ export const MessageInput = forwardRef<MessageInputRef, MessageInputProps>(funct
             }}
             style={[
               styles.textInput,
-              IS_WEB
+              isWeb
                 ? {
                     height: inputHeight,
                     minHeight: MIN_INPUT_HEIGHT,
@@ -1010,12 +1017,12 @@ export const MessageInput = forwardRef<MessageInputRef, MessageInputProps>(funct
                   },
             ]}
             multiline
-            scrollEnabled={IS_WEB ? inputHeight >= MAX_INPUT_HEIGHT : true}
+            scrollEnabled={isWeb ? inputHeight >= MAX_INPUT_HEIGHT : true}
             onContentSizeChange={handleContentSizeChange}
             editable={!isDictating && !isRealtimeVoiceForCurrentAgent && !disabled}
             onKeyPress={shouldHandleDesktopSubmit ? handleDesktopKeyPress : undefined}
             onSelectionChange={handleSelectionChange}
-            autoFocus={IS_WEB && autoFocus}
+            autoFocus={isWeb && autoFocus}
           />
           {inputScrollbar}
         </View>
@@ -1206,7 +1213,7 @@ const styles = StyleSheet.create(((theme: any) => ({
       xs: theme.spacing[3],
       md: theme.spacing[4],
     },
-    ...(IS_WEB
+    ...(isWeb
       ? {
           transitionProperty: "border-color",
           transitionDuration: "200ms",
@@ -1225,7 +1232,7 @@ const styles = StyleSheet.create(((theme: any) => ({
     borderWidth: 1,
     borderColor: theme.colors.borderAccent,
     overflow: "hidden",
-    ...(IS_WEB
+    ...(isWeb
       ? {
           cursor: "pointer",
         }
@@ -1250,7 +1257,7 @@ const styles = StyleSheet.create(((theme: any) => ({
     justifyContent: "center",
     backgroundColor: "rgba(0, 0, 0, 0.5)",
     opacity: 0,
-    ...(IS_WEB
+    ...(isWeb
       ? {
           transitionProperty: "opacity",
           transitionDuration: "150ms",
@@ -1269,7 +1276,7 @@ const styles = StyleSheet.create(((theme: any) => ({
     fontSize: theme.fontSize.base,
     fontWeight: theme.fontWeight.normal,
     lineHeight: theme.fontSize.base * 1.4,
-    ...(IS_WEB
+    ...(isWeb
       ? {
           outlineStyle: "none" as const,
           outlineWidth: 0,