From 585d01684abaf9c8ea656845ef81e3d2fec85be1 Mon Sep 17 00:00:00 2001
From: Neil <4138956+nwparker@users.noreply.github.com>
Date: Tue, 4 Aug 2026 08:53:55 -0700
Subject: [PATCH] fix(chat): preserve browser IME composition ownership

---
 .../native-chat/NativeChatComposerField.tsx   |  57 ++++++++-
 .../native-chat-composer-autogrow.test.tsx    | 120 +++++++++++++++++-
 2 files changed, 166 insertions(+), 11 deletions(-)

diff --git a/src/renderer/src/components/native-chat/NativeChatComposerField.tsx b/src/renderer/src/components/native-chat/NativeChatComposerField.tsx
index 6f954a60aa5..b255055dc9b 100644
--- a/src/renderer/src/components/native-chat/NativeChatComposerField.tsx
+++ b/src/renderer/src/components/native-chat/NativeChatComposerField.tsx
@@ -4,6 +4,7 @@ import type {
   KeyboardEventHandler,
   RefObject
 } from 'react'
+import { useLayoutEffect, useRef } from 'react'
 import { Image as ImageIcon, ImageOff, X } from 'lucide-react'
 import { translate } from '@/i18n/i18n'
 import { cn } from '@/lib/utils'
@@ -97,6 +98,17 @@ export function NativeChatComposerField({
   sessionOptionsSurface,
   sessionOptionsSnapshot
 }: NativeChatComposerFieldProps): React.JSX.Element {
+  const compositionActiveRef = useRef(false)
+  const pendingCompositionEnterRef = useRef(false)
+
+  useLayoutEffect(() => {
+    const textarea = textareaRef.current
+    if (!textarea || compositionActiveRef.current || textarea.value === draft) {
+      return
+    }
+    textarea.value = draft
+  }, [draft, textareaRef])
+
   return (
     <div className="shrink-0 bg-background">
       {/* Extra bottom padding keeps the input box off the window rim. */}
@@ -164,13 +176,50 @@ export function NativeChatComposerField({
             ) : null}
             <textarea
               ref={textareaRef}
-              value={draft}
+              defaultValue={draft}
               disabled={disabled}
               rows={2}
               onChange={(e) => onDraftChange(e.target.value, e.currentTarget)}
-              onKeyDown={onKeyDown}
-              onCompositionStart={onCompositionStart}
-              onCompositionEnd={onCompositionEnd}
+              onKeyDown={(event) => {
+                const ownsCompositionEnter =
+                  event.nativeEvent.isComposing &&
+                  ((event.key === 'Enter' && event.keyCode === 13) ||
+                    (event.key === 'Process' && event.keyCode === 229))
+                if (ownsCompositionEnter) {
+                  pendingCompositionEnterRef.current = true
+                  return
+                }
+                if (
+                  pendingCompositionEnterRef.current &&
+                  event.key === 'Enter' &&
+                  event.keyCode === 13 &&
+                  !event.nativeEvent.isComposing
+                ) {
+                  event.preventDefault()
+                  return
+                }
+                onKeyDown(event)
+              }}
+              onKeyUp={(event) => {
+                if (
+                  (event.key === 'Enter' && event.keyCode === 13) ||
+                  (event.key === 'Process' && event.keyCode === 229)
+                ) {
+                  pendingCompositionEnterRef.current = false
+                }
+              }}
+              onBlur={() => {
+                compositionActiveRef.current = false
+                pendingCompositionEnterRef.current = false
+              }}
+              onCompositionStart={(event) => {
+                compositionActiveRef.current = true
+                onCompositionStart(event)
+              }}
+              onCompositionEnd={(event) => {
+                compositionActiveRef.current = false
+                onCompositionEnd(event)
+              }}
               onPaste={onPaste}
               onSelect={(e) => onTextareaSelect(e.currentTarget)}
               aria-expanded={autocomplete.mode === 'slash' || autocomplete.mode === 'skill'}
diff --git a/src/renderer/src/components/native-chat/native-chat-composer-autogrow.test.tsx b/src/renderer/src/components/native-chat/native-chat-composer-autogrow.test.tsx
index 96f82876114..a78980ebcd1 100644
--- a/src/renderer/src/components/native-chat/native-chat-composer-autogrow.test.tsx
+++ b/src/renderer/src/components/native-chat/native-chat-composer-autogrow.test.tsx
@@ -6,7 +6,7 @@
  *  has no layout engine, so real pixel growth is covered by app validation. */
 
 import { createRef } from 'react'
-import { cleanup, render, screen } from '@testing-library/react'
+import { cleanup, fireEvent, render, screen } from '@testing-library/react'
 import { afterEach, describe, expect, it, vi } from 'vitest'
 
 vi.mock('@/i18n/i18n', () => ({
@@ -22,12 +22,20 @@ vi.mock('./NativeChatAutocompleteMenus', () => ({
   NativeChatPickerMenu: () => null
 }))
 
-import { NativeChatComposerField } from './NativeChatComposerField'
+import {
+  NativeChatComposerField,
+  type NativeChatComposerFieldProps
+} from './NativeChatComposerField'
 
 afterEach(() => cleanup())
 
-function renderField(draft: string): HTMLTextAreaElement {
-  render(
+function composerField(
+  draft: string,
+  callbacks: Partial<
+    Pick<NativeChatComposerFieldProps, 'onDraftChange' | 'onKeyDown' | 'onCompositionEnd'>
+  > = {}
+): React.JSX.Element {
+  return (
     <NativeChatComposerField
       textareaRef={createRef<HTMLTextAreaElement>()}
       draft={draft}
@@ -44,11 +52,11 @@ function renderField(draft: string): HTMLTextAreaElement {
       dictationDisabled={false}
       isDictating={false}
       isDictationHoldMode={false}
-      onDraftChange={vi.fn()}
+      onDraftChange={callbacks.onDraftChange ?? vi.fn()}
       onTextareaSelect={vi.fn()}
-      onKeyDown={vi.fn()}
+      onKeyDown={callbacks.onKeyDown ?? vi.fn()}
       onCompositionStart={vi.fn()}
-      onCompositionEnd={vi.fn()}
+      onCompositionEnd={callbacks.onCompositionEnd ?? vi.fn()}
       onPaste={vi.fn()}
       pickerListboxId="picker"
       onChoosePickerItem={vi.fn()}
@@ -64,6 +72,10 @@ function renderField(draft: string): HTMLTextAreaElement {
       sessionOptionsSnapshot={[]}
     />
   )
+}
+
+function renderField(draft: string): HTMLTextAreaElement {
+  render(composerField(draft))
   return screen.getByRole('textbox') as HTMLTextAreaElement
 }
 
@@ -96,3 +108,97 @@ describe('native chat composer autogrow', () => {
     expect(renderField('a\n'.repeat(6)).style.height).toBe('')
   })
 })
+
+describe('native chat composer composition ownership', () => {
+  it('preserves browser-owned Korean preedit through stale streaming rerenders', () => {
+    const onCompositionEnd = vi.fn()
+    const view = render(composerField('', { onCompositionEnd }))
+    const textarea = screen.getByRole('textbox') as HTMLTextAreaElement
+    fireEvent.compositionStart(textarea)
+    textarea.value = '가'
+
+    for (let index = 0; index < 120; index += 1) {
+      view.rerender(composerField(`stale stream ${index}`, { onCompositionEnd }))
+      expect(screen.getByRole('textbox')).toBe(textarea)
+      expect(textarea.value).toBe('가')
+    }
+
+    fireEvent.compositionEnd(textarea, { data: '가' })
+    expect(onCompositionEnd).toHaveBeenCalledOnce()
+    expect(onCompositionEnd.mock.calls[0][0].target.value).toBe('가')
+  })
+
+  it('applies draft rerenders while ordinary English input is idle', () => {
+    const view = render(composerField('abc'))
+    const textarea = screen.getByRole('textbox') as HTMLTextAreaElement
+
+    view.rerender(composerField('ordinary'))
+
+    expect(screen.getByRole('textbox')).toBe(textarea)
+    expect(textarea.value).toBe('ordinary')
+  })
+
+  it('owns an unmarked Enter redispatch until the marked IME gesture keyup', () => {
+    const onKeyDown = vi.fn()
+    render(composerField('가', { onKeyDown }))
+    const textarea = screen.getByRole('textbox') as HTMLTextAreaElement
+    fireEvent.compositionStart(textarea)
+
+    const markedResult = fireEvent.keyDown(textarea, {
+      key: 'Enter',
+      keyCode: 13,
+      isComposing: true
+    })
+    fireEvent.compositionEnd(textarea, { data: '가' })
+    const redispatchResult = fireEvent.keyDown(textarea, {
+      key: 'Enter',
+      keyCode: 13,
+      isComposing: false
+    })
+
+    expect(markedResult).toBe(true)
+    expect(redispatchResult).toBe(false)
+    expect(onKeyDown).not.toHaveBeenCalled()
+
+    fireEvent.keyUp(textarea, { key: 'Enter', keyCode: 13 })
+    fireEvent.keyDown(textarea, { key: 'Enter', keyCode: 13, isComposing: false })
+    expect(onKeyDown).toHaveBeenCalledOnce()
+  })
+
+  it('retains the Windows Process gesture through its unmarked Enter redispatch', () => {
+    const onKeyDown = vi.fn()
+    render(composerField('가', { onKeyDown }))
+    const textarea = screen.getByRole('textbox') as HTMLTextAreaElement
+    fireEvent.compositionStart(textarea)
+    fireEvent.keyDown(textarea, {
+      key: 'Process',
+      keyCode: 229,
+      isComposing: true
+    })
+    fireEvent.compositionEnd(textarea, { data: '가' })
+
+    const redispatchResult = fireEvent.keyDown(textarea, {
+      key: 'Enter',
+      keyCode: 13,
+      isComposing: false
+    })
+
+    expect(redispatchResult).toBe(false)
+    expect(onKeyDown).not.toHaveBeenCalled()
+
+    fireEvent.keyUp(textarea, { key: 'Process', keyCode: 229 })
+    fireEvent.keyUp(textarea, { key: 'Enter', keyCode: 13 })
+    fireEvent.keyDown(textarea, { key: 'Enter', keyCode: 13, isComposing: false })
+    expect(onKeyDown).toHaveBeenCalledOnce()
+  })
+
+  it('passes ordinary English Enter through without an IME gesture', () => {
+    const onKeyDown = vi.fn()
+    render(composerField('abc', { onKeyDown }))
+    const textarea = screen.getByRole('textbox') as HTMLTextAreaElement
+
+    fireEvent.keyDown(textarea, { key: 'Enter', keyCode: 13, isComposing: false })
+
+    expect(onKeyDown).toHaveBeenCalledOnce()
+  })
+})