diff --git a/apps/desktop/src/app/chat/composer/enter-submit-dom-race.test.tsx b/apps/desktop/src/app/chat/composer/enter-submit-dom-race.test.tsx
index 76fdf79f8097..80f59e98b367 100644
--- a/apps/desktop/src/app/chat/composer/enter-submit-dom-race.test.tsx
+++ b/apps/desktop/src/app/chat/composer/enter-submit-dom-race.test.tsx
@@ -2,6 +2,8 @@ import { act, cleanup, fireEvent, render } from '@testing-library/react'
 import { useRef, useState } from 'react'
 import { afterEach, describe, expect, it, vi } from 'vitest'
 
+import { isImeComposingKeyEvent } from './ime'
+
 // No global setupFiles registers auto-cleanup, so unmount between tests —
 // otherwise a second render() leaks the first editor and getByTestId('editor')
 // matches multiple nodes.
@@ -78,6 +80,10 @@ function Harness({
   }
 
   const handleKeyDown = (event: React.KeyboardEvent<HTMLDivElement>) => {
+    if (isImeComposingKeyEvent(event)) {
+      return
+    }
+
     if (event.key === 'Enter' && !event.shiftKey) {
       event.preventDefault()
 
@@ -132,6 +138,21 @@ describe('composer Enter submit — live DOM vs stale composer state (#39630)',
     expect(onSubmit).toHaveBeenCalledWith('hello world')
   })
 
+  it('does not submit when Chromium reports IME Enter as keyCode 229', async () => {
+    const onSubmit = vi.fn()
+    const { getByTestId } = render(
+      <Harness onCancel={vi.fn()} onDrain={vi.fn()} onQueue={vi.fn()} onSubmit={onSubmit} />
+    )
+    const editor = getByTestId('editor')
+
+    await act(async () => {
+      editor.textContent = '你好'
+      fireEvent.keyDown(editor, { key: 'Enter', keyCode: 229 })
+    })
+
+    expect(onSubmit).not.toHaveBeenCalled()
+  })
+
   it('queues a fast-typed message while busy instead of draining the queue or cancelling', async () => {
     const onQueue = vi.fn()
     const onDrain = vi.fn()
diff --git a/apps/desktop/src/app/chat/composer/ime.test.ts b/apps/desktop/src/app/chat/composer/ime.test.ts
new file mode 100644
index 000000000000..3cf4673425f3
--- /dev/null
+++ b/apps/desktop/src/app/chat/composer/ime.test.ts
@@ -0,0 +1,27 @@
+import type { KeyboardEvent as ReactKeyboardEvent } from 'react'
+import { describe, expect, it } from 'vitest'
+
+import { isImeComposingKeyEvent } from './ime'
+
+function keyEvent({ isComposing = false, keyCode = 13 }: { isComposing?: boolean; keyCode?: number }) {
+  return {
+    nativeEvent: {
+      isComposing,
+      keyCode
+    }
+  } as ReactKeyboardEvent<HTMLElement>
+}
+
+describe('isImeComposingKeyEvent', () => {
+  it('detects standard composing key events', () => {
+    expect(isImeComposingKeyEvent(keyEvent({ isComposing: true }))).toBe(true)
+  })
+
+  it('detects Chromium IME processing keyCode 229 after isComposing flips false', () => {
+    expect(isImeComposingKeyEvent(keyEvent({ isComposing: false, keyCode: 229 }))).toBe(true)
+  })
+
+  it('does not treat normal Enter as IME composition', () => {
+    expect(isImeComposingKeyEvent(keyEvent({ isComposing: false, keyCode: 13 }))).toBe(false)
+  })
+})
diff --git a/apps/desktop/src/app/chat/composer/ime.ts b/apps/desktop/src/app/chat/composer/ime.ts
new file mode 100644
index 000000000000..f80d43838c4f
--- /dev/null
+++ b/apps/desktop/src/app/chat/composer/ime.ts
@@ -0,0 +1,11 @@
+import type { KeyboardEvent as ReactKeyboardEvent } from 'react'
+
+const CHROMIUM_IME_PROCESSING_KEY_CODE = 229
+
+export function isImeComposingKeyEvent(event: ReactKeyboardEvent<HTMLElement>): boolean {
+  // Chromium/Electron can report the IME confirmation key as keyCode 229
+  // even when isComposing is already false by the time React handles keydown.
+  // Treat it as composition so Enter confirms CJK preedit text instead of
+  // submitting the composer.
+  return event.nativeEvent.isComposing || event.nativeEvent.keyCode === CHROMIUM_IME_PROCESSING_KEY_CODE
+}
diff --git a/apps/desktop/src/app/chat/composer/index.tsx b/apps/desktop/src/app/chat/composer/index.tsx
index d8b06a68d377..1c176cbc6693 100644
--- a/apps/desktop/src/app/chat/composer/index.tsx
+++ b/apps/desktop/src/app/chat/composer/index.tsx
@@ -59,6 +59,7 @@ import {
 } from './focus'
 import { HelpHint } from './help-hint'
 import { useAtCompletions } from './hooks/use-at-completions'
+import { isImeComposingKeyEvent } from './ime'
 import { useSlashCompletions } from './hooks/use-slash-completions'
 import { useVoiceConversation } from './hooks/use-voice-conversation'
 import { useVoiceRecorder } from './hooks/use-voice-recorder'
@@ -672,11 +673,10 @@ export function ChatBar({
 
   const handleEditorKeyDown = (event: KeyboardEvent<HTMLDivElement>) => {
     // IME composition: Enter confirms composed text, not a message submission.
-    // We check both composingRef (set by compositionstart/compositionend, robust
-    // across browsers) and nativeEvent.isComposing (Chromium fallback).  Without
-    // this guard, pressing Enter to finalise a Korean/Japanese/Chinese IME
-    // preedit fires submitDraft() and splits the message mid-word.
-    if (composingRef.current || event.nativeEvent.isComposing) {
+    // Check React's composition ref, native isComposing, and Chromium's
+    // IME-processing keyCode 229 fallback. Some Electron/macOS/CJK paths flip
+    // isComposing false before the Enter keydown reaches React.
+    if (composingRef.current || isImeComposingKeyEvent(event)) {
       return
     }
 
diff --git a/apps/desktop/src/components/assistant-ui/thread.tsx b/apps/desktop/src/components/assistant-ui/thread.tsx
index 9bcc05da3bf2..e41a09c6a75f 100644
--- a/apps/desktop/src/components/assistant-ui/thread.tsx
+++ b/apps/desktop/src/components/assistant-ui/thread.tsx
@@ -36,6 +36,7 @@ import {
   onComposerInsertRequest
 } from '@/app/chat/composer/focus'
 import { useAtCompletions } from '@/app/chat/composer/hooks/use-at-completions'
+import { isImeComposingKeyEvent } from '@/app/chat/composer/ime'
 import { useSlashCompletions } from '@/app/chat/composer/hooks/use-slash-completions'
 import {
   dragHasAttachments,
@@ -1401,6 +1402,12 @@ const UserEditComposer: FC<UserEditComposerProps> = ({ cwd, gateway, sessionId }
   )
 
   const handleKeyDown = (event: KeyboardEvent<HTMLDivElement>) => {
+    // IME Enter confirms the composed text in the edit composer. Do not let it
+    // select trigger items or submit the edited message.
+    if (isImeComposingKeyEvent(event)) {
+      return
+    }
+
     if (trigger && triggerItems.length > 0) {
       if (event.key === 'ArrowDown') {
         event.preventDefault()