From e0bc4e1126783fc4e5302e18521f92125956dec2 Mon Sep 17 00:00:00 2001
From: Neil <4138956+nwparker@users.noreply.github.com>
Date: Tue, 25 Aug 2026 00:30:47 -0700
Subject: [PATCH] refactor(editor): split notebook, editor, and external-watch
 surfaces (#16143)

* refactor(editor): split editor and watch surfaces

* fix(editor): revert behavior changes smuggled into the surface split

Restore merge-base React keys in IpynbCellOutputs: the content-identity keys
JSON.stringify'd every output value, including raw base64 image payloads, on
every keystroke.

Collapse the duplicated lazy() declarations into editor-lazy-views so each
viewer keeps a single React.lazy identity across the extracted surfaces.
---
 config/max-lines-baseline.txt                 |    3 -
 .../editor/EditorConflictReviewSurface.tsx    |  286 +++++
 .../EditorContent.monaco-lifecycle.test.tsx   |   72 ++
 .../src/components/editor/EditorContent.tsx   |  890 ++-------------
 .../editor/EditorDiffFileSurface.tsx          |  172 +++
 .../editor/EditorEditFileSurface.tsx          |  266 +++++
 .../editor/EditorFileLoadErrorView.tsx        |   29 +
 .../editor/EditorMarkdownFileSurface.tsx      |  167 +++
 .../src/components/editor/IpynbCellEditor.tsx |  148 +++
 .../components/editor/IpynbCellOutputs.tsx    |  121 ++
 .../components/editor/IpynbCellToolbar.tsx    |  176 +++
 .../src/components/editor/IpynbViewer.tsx     |  863 ++------------
 .../components/editor/editor-lazy-views.ts    |   16 +
 .../editor/useEditorConflictNavigation.ts     |   61 +
 .../editor/useIpynbCellExecution.test.tsx     |  121 ++
 .../editor/useIpynbCellExecution.ts           |  105 ++
 .../editor/useIpynbDocumentEditing.test.tsx   |  142 +++
 .../editor/useIpynbDocumentEditing.ts         |  221 ++++
 .../editor/useIpynbScrollRestoration.ts       |   43 +
 ...editor-external-watch-disk-verification.ts |  286 +++++
 ...tor-external-watch-event-reconciliation.ts |  300 +++++
 .../hooks/editor-external-watch-targets.ts    |  260 +++++
 ...EditorExternalWatch-subscriptions.test.tsx |  187 +++
 .../src/hooks/useEditorExternalWatch.ts       | 1000 ++---------------
 24 files changed, 3422 insertions(+), 2513 deletions(-)
 create mode 100644 src/renderer/src/components/editor/EditorConflictReviewSurface.tsx
 create mode 100644 src/renderer/src/components/editor/EditorDiffFileSurface.tsx
 create mode 100644 src/renderer/src/components/editor/EditorEditFileSurface.tsx
 create mode 100644 src/renderer/src/components/editor/EditorFileLoadErrorView.tsx
 create mode 100644 src/renderer/src/components/editor/EditorMarkdownFileSurface.tsx
 create mode 100644 src/renderer/src/components/editor/IpynbCellEditor.tsx
 create mode 100644 src/renderer/src/components/editor/IpynbCellOutputs.tsx
 create mode 100644 src/renderer/src/components/editor/IpynbCellToolbar.tsx
 create mode 100644 src/renderer/src/components/editor/editor-lazy-views.ts
 create mode 100644 src/renderer/src/components/editor/useEditorConflictNavigation.ts
 create mode 100644 src/renderer/src/components/editor/useIpynbCellExecution.test.tsx
 create mode 100644 src/renderer/src/components/editor/useIpynbCellExecution.ts
 create mode 100644 src/renderer/src/components/editor/useIpynbDocumentEditing.test.tsx
 create mode 100644 src/renderer/src/components/editor/useIpynbDocumentEditing.ts
 create mode 100644 src/renderer/src/components/editor/useIpynbScrollRestoration.ts
 create mode 100644 src/renderer/src/hooks/editor-external-watch-disk-verification.ts
 create mode 100644 src/renderer/src/hooks/editor-external-watch-event-reconciliation.ts
 create mode 100644 src/renderer/src/hooks/editor-external-watch-targets.ts
 create mode 100644 src/renderer/src/hooks/useEditorExternalWatch-subscriptions.test.tsx

diff --git a/config/max-lines-baseline.txt b/config/max-lines-baseline.txt
index e1bebf1b4b3..565b410a7c3 100644
--- a/config/max-lines-baseline.txt
+++ b/config/max-lines-baseline.txt
@@ -72,8 +72,6 @@ inline src/renderer/src/components/WorktreeJumpPalette.tsx
 inline src/renderer/src/components/activity/ActivityPrototypePage.tsx
 inline src/renderer/src/components/automations/AutomationsPage.tsx
 inline src/renderer/src/components/editor/CombinedDiffViewer.tsx
-inline src/renderer/src/components/editor/EditorContent.tsx
-inline src/renderer/src/components/editor/IpynbViewer.tsx
 inline src/renderer/src/components/editor/MarkdownPreview.tsx
 inline src/renderer/src/components/feature-wall/EditorAnimatedVisual.tsx
 inline src/renderer/src/components/floating-terminal/FloatingTerminalPanel.tsx
@@ -96,7 +94,6 @@ inline src/renderer/src/components/terminal-pane/pty-transport.ts
 inline src/renderer/src/components/terminal-pane/remote-runtime-pty-transport.ts
 inline src/renderer/src/components/terminal-pane/use-terminal-pane-lifecycle.ts
 inline src/renderer/src/hooks/useAutomationDispatchEvents.ts
-inline src/renderer/src/hooks/useEditorExternalWatch.ts
 inline src/renderer/src/hooks/useSettingsNavigationMetadata.ts
 inline src/renderer/src/lib/pane-manager/pane-terminal-output-scheduler.ts
 inline src/renderer/src/lib/pane-manager/pane-tree-ops.ts
diff --git a/src/renderer/src/components/editor/EditorConflictReviewSurface.tsx b/src/renderer/src/components/editor/EditorConflictReviewSurface.tsx
new file mode 100644
index 00000000000..85c53cfb41f
--- /dev/null
+++ b/src/renderer/src/components/editor/EditorConflictReviewSurface.tsx
@@ -0,0 +1,286 @@
+import React from 'react'
+import { detectLanguage } from '@/lib/language-detect'
+import { joinPath } from '@/lib/path'
+import { useAppStore } from '@/store'
+import type { OpenFile, PendingEditorReveal } from '@/store/slices/editor'
+import type { GitStatusEntry } from '../../../../shared/git-status-types'
+import { ConflictBanner, ConflictPlaceholderView, ConflictReviewPanel } from './ConflictComponents'
+import { ImageViewer, MonacoEditor } from './editor-lazy-views'
+import { EditorFileLoadErrorView } from './EditorFileLoadErrorView'
+import type { FileContent } from './editor-panel-content-types'
+import { translate } from '@/i18n/i18n'
+import type { EditorConflictNavigation } from './useEditorConflictNavigation'
+
+export function EditorConflictReviewSurface({
+  activeFile,
+  viewStateScopeId,
+  fileContents,
+  editBuffers,
+  openFiles,
+  worktreeEntries,
+  pendingEditorReveal,
+  getConflictNavigation,
+  handleContentChangeForFile,
+  handleSaveForFile,
+  reloadContent
+}: {
+  activeFile: OpenFile
+  viewStateScopeId: string
+  fileContents: Record<string, FileContent>
+  editBuffers: Record<string, string>
+  openFiles: OpenFile[]
+  worktreeEntries: GitStatusEntry[]
+  pendingEditorReveal: PendingEditorReveal | null
+  getConflictNavigation: (file: OpenFile, content: string) => EditorConflictNavigation | undefined
+  handleContentChangeForFile: (file: OpenFile, content: string) => void
+  handleSaveForFile: (file: OpenFile, content: string) => Promise<boolean>
+  reloadContent: (file: OpenFile) => void
+}): React.JSX.Element {
+  const openConflictReviewFile = useAppStore((s) => s.openConflictReviewFile)
+  const openConflictReview = useAppStore((s) => s.openConflictReview)
+  const closeFile = useAppStore((s) => s.closeFile)
+  const setRightSidebarTab = useAppStore((s) => s.setRightSidebarTab)
+  const selectedConflictReviewFile = activeFile.conflictReview?.selectedFileId
+    ? (openFiles.find((file) => file.id === activeFile.conflictReview?.selectedFileId) ?? null)
+    : null
+
+  const openConflictEntry = React.useCallback(
+    (entry: GitStatusEntry) => {
+      openConflictReviewFile(
+        activeFile.id,
+        activeFile.worktreeId,
+        activeFile.filePath,
+        entry,
+        detectLanguage(entry.path)
+      )
+    },
+    [activeFile.filePath, activeFile.id, activeFile.worktreeId, openConflictReviewFile]
+  )
+
+  const createContentFile = (entry: GitStatusEntry): OpenFile => {
+    const absolutePath = joinPath(activeFile.filePath, entry.path)
+    const conflict =
+      entry.conflictKind && entry.conflictStatus && entry.conflictStatusSource
+        ? entry.status === 'deleted'
+          ? {
+              kind: 'conflict-placeholder' as const,
+              conflictKind: entry.conflictKind,
+              conflictStatus: entry.conflictStatus,
+              conflictStatusSource: entry.conflictStatusSource,
+              message: translate(
+                'auto.components.editor.EditorContent.8b1a605bae',
+                'This file is in a conflict state, but no working-tree file is available to edit.'
+              ),
+              guidance: 'Resolve the conflict in Git or restore one side before reopening it.'
+            }
+          : {
+              kind: 'conflict-editable' as const,
+              conflictKind: entry.conflictKind,
+              conflictStatus: entry.conflictStatus,
+              conflictStatusSource: entry.conflictStatusSource
+            }
+        : undefined
+
+    return {
+      id: absolutePath,
+      filePath: absolutePath,
+      relativePath: entry.path,
+      worktreeId: activeFile.worktreeId,
+      language: detectLanguage(entry.path),
+      isDirty: false,
+      mode: 'edit',
+      conflict
+    }
+  }
+
+  const renderEditorContent = ({
+    contentFile,
+    entry,
+    className,
+    viewStateKeySuffix,
+    readOnly = false,
+    autoHeight = false
+  }: {
+    contentFile: OpenFile
+    entry: GitStatusEntry | null
+    className: string
+    viewStateKeySuffix: string
+    readOnly?: boolean
+    autoHeight?: boolean
+  }): React.JSX.Element => {
+    if (contentFile.conflict?.kind === 'conflict-placeholder') {
+      return (
+        <div className={className}>
+          <ConflictPlaceholderView file={contentFile} />
+        </div>
+      )
+    }
+
+    const fileContent = fileContents[contentFile.id]
+    if (!fileContent) {
+      return (
+        <div className={className}>
+          <div className="flex h-full items-center justify-center text-sm text-muted-foreground">
+            {translate('auto.components.editor.EditorContent.b2735221f5', 'Loading...')}
+          </div>
+        </div>
+      )
+    }
+    if (fileContent.loadError) {
+      return (
+        <div className={className}>
+          <EditorFileLoadErrorView
+            message={fileContent.loadError}
+            onRetry={() => reloadContent(contentFile)}
+          />
+        </div>
+      )
+    }
+    if (fileContent.isBinary) {
+      if (fileContent.isImage) {
+        return (
+          <div className={className}>
+            <ImageViewer
+              content={fileContent.content}
+              filePath={contentFile.filePath}
+              mimeType={fileContent.mimeType}
+            />
+          </div>
+        )
+      }
+      return (
+        <div className={className}>
+          <div className="flex h-full items-center justify-center text-sm text-muted-foreground">
+            {translate(
+              'auto.components.editor.EditorContent.b9de81ba52',
+              'Binary file — cannot display'
+            )}
+          </div>
+        </div>
+      )
+    }
+
+    const selectedLanguage = detectLanguage(contentFile.relativePath)
+    const monacoLanguage = selectedLanguage === 'notebook' ? 'json' : selectedLanguage
+    const selectedViewStateKey = `${contentFile.filePath}::${viewStateScopeId}:${viewStateKeySuffix}`
+    const selectedContent = editBuffers[contentFile.id] ?? fileContent.content
+
+    return (
+      <div className={className}>
+        {contentFile.conflict && (
+          <ConflictBanner
+            file={contentFile}
+            entry={entry}
+            conflictNavigation={getConflictNavigation(contentFile, selectedContent)}
+          />
+        )}
+        <div className={autoHeight ? 'shrink-0' : 'min-h-0 flex-1'}>
+          <MonacoEditor
+            key={`${viewStateScopeId}:${contentFile.id}:${viewStateKeySuffix}`}
+            fileId={contentFile.id}
+            filePath={contentFile.filePath}
+            viewStateKey={selectedViewStateKey}
+            relativePath={contentFile.relativePath}
+            content={selectedContent}
+            language={monacoLanguage}
+            onContentChange={
+              readOnly ? () => {} : (content) => handleContentChangeForFile(contentFile, content)
+            }
+            onSave={readOnly ? () => {} : (content) => handleSaveForFile(contentFile, content)}
+            worktreeId={contentFile.worktreeId}
+            markdownAnnotationsEnabled={false}
+            conflictDecorationsEnabled={contentFile.conflict?.conflictStatus === 'unresolved'}
+            readOnly={readOnly}
+            autoHeight={autoHeight}
+            revealLine={
+              matchesPendingEditorReveal(pendingEditorReveal, contentFile)
+                ? pendingEditorReveal.line
+                : undefined
+            }
+            revealColumn={
+              matchesPendingEditorReveal(pendingEditorReveal, contentFile)
+                ? pendingEditorReveal.column
+                : undefined
+            }
+            revealMatchLength={
+              matchesPendingEditorReveal(pendingEditorReveal, contentFile)
+                ? pendingEditorReveal.matchLength
+                : undefined
+            }
+          />
+        </div>
+      </div>
+    )
+  }
+
+  const renderSelectedContent = (selectedFile: OpenFile): React.JSX.Element => {
+    const selectedConflictEntry =
+      worktreeEntries.find((entry) => entry.path === selectedFile.relativePath) ?? null
+    return renderEditorContent({
+      contentFile: selectedFile,
+      entry: selectedConflictEntry,
+      className: 'flex min-h-0 flex-1 flex-col',
+      viewStateKeySuffix: 'selected'
+    })
+  }
+
+  const renderInlineFile = (entry: GitStatusEntry): React.JSX.Element =>
+    renderEditorContent({
+      contentFile: createContentFile(entry),
+      entry,
+      className: 'flex min-h-[120px] flex-col border-b border-border last:border-b-0',
+      viewStateKeySuffix: `overview:${entry.path}`,
+      readOnly: true,
+      autoHeight: true
+    })
+
+  const renderAllContent = (): React.JSX.Element => {
+    const snapshotEntries = activeFile.conflictReview?.entries ?? []
+    const liveEntriesByPath = new Map(worktreeEntries.map((entry) => [entry.path, entry]))
+    const unresolvedEntries = snapshotEntries.flatMap((entry) => {
+      const liveEntry = liveEntriesByPath.get(entry.path)
+      return liveEntry?.conflictStatus === 'unresolved' && liveEntry.conflictKind ? [liveEntry] : []
+    })
+    return (
+      <div className="min-h-0 flex-1 overflow-y-auto bg-editor-surface scrollbar-sleek">
+        {unresolvedEntries.map(renderInlineFile)}
+      </div>
+    )
+  }
+
+  return (
+    <ConflictReviewPanel
+      file={activeFile}
+      liveEntries={worktreeEntries}
+      onOpenEntry={openConflictEntry}
+      selectedFile={selectedConflictReviewFile}
+      selectedContent={
+        selectedConflictReviewFile
+          ? renderSelectedContent(selectedConflictReviewFile)
+          : renderAllContent()
+      }
+      onDismiss={() => closeFile(activeFile.id)}
+      onRefreshSnapshot={() =>
+        openConflictReview(
+          activeFile.worktreeId,
+          activeFile.filePath,
+          worktreeEntries
+            .filter((entry) => entry.conflictStatus === 'unresolved' && entry.conflictKind)
+            .map((entry) => ({ path: entry.path, conflictKind: entry.conflictKind! })),
+          'live-summary'
+        )
+      }
+      onReturnToSourceControl={() => setRightSidebarTab('source-control')}
+    />
+  )
+}
+
+function matchesPendingEditorReveal(
+  reveal: PendingEditorReveal | null,
+  file: Pick<OpenFile, 'id' | 'filePath'>
+): reveal is PendingEditorReveal {
+  if (!reveal) {
+    return false
+  }
+  return reveal.fileId ? reveal.fileId === file.id : reveal.filePath === file.filePath
+}
diff --git a/src/renderer/src/components/editor/EditorContent.monaco-lifecycle.test.tsx b/src/renderer/src/components/editor/EditorContent.monaco-lifecycle.test.tsx
index d0cc1cc78d9..0590a1a7b32 100644
--- a/src/renderer/src/components/editor/EditorContent.monaco-lifecycle.test.tsx
+++ b/src/renderer/src/components/editor/EditorContent.monaco-lifecycle.test.tsx
@@ -7,6 +7,19 @@ const lifecycle = vi.hoisted(() => ({
   events: [] as string[],
   diffModelKeys: [] as string[],
   models: new Map<string, { content: string; undo: string[] }>(),
+  notebookProps: [] as {
+    fileId: string
+    filePath: string
+    worktreeId: string
+    scrollCacheKey: string
+    onContentChange: (content: string) => void
+    onSave: (content: string) => Promise<boolean>
+  }[],
+  richMarkdownProps: [] as {
+    externalSshTargetId?: string
+    runtimeEnvironmentId?: string
+    worktreeId: string
+  }[],
   mountedProps: [] as {
     filePath: string
     readOnly?: boolean
@@ -34,6 +47,20 @@ vi.mock('@/lib/lazy-with-retry', async () => {
           return null
         }
       }
+      if (factory.toString().includes('/IpynbViewer.tsx')) {
+        return function MockIpynbViewer(props: (typeof lifecycle.notebookProps)[number]) {
+          lifecycle.notebookProps.push(props)
+          return null
+        }
+      }
+      if (factory.toString().includes('/RichMarkdownEditor.tsx')) {
+        return function MockRichMarkdownEditor(
+          props: (typeof lifecycle.richMarkdownProps)[number]
+        ) {
+          lifecycle.richMarkdownProps.push(props)
+          return null
+        }
+      }
       if (!factory.toString().includes('/MonacoEditor.tsx')) {
         return () => null
       }
@@ -187,6 +214,8 @@ afterEach(() => {
   lifecycle.diffModelKeys.length = 0
   lifecycle.models.clear()
   lifecycle.mountedProps.length = 0
+  lifecycle.notebookProps.length = 0
+  lifecycle.richMarkdownProps.length = 0
 })
 
 describe('EditorContent Monaco lifecycle boundary', () => {
@@ -261,4 +290,47 @@ describe('EditorContent Monaco lifecycle boundary', () => {
     // armed and a later rich-mode remount of this pane steals focus back.
     expect(lifecycle.mountedProps.at(0)?.viewStateId).toBe('same-pane')
   })
+
+  it('preserves notebook save ownership and worktree routing across the extracted surface', () => {
+    const notebook = file('/repo/analysis.ipynb', { language: 'notebook' })
+    const notebookProps = props(notebook, '{"cells": []}')
+
+    render(
+      <EditorContent {...notebookProps} resolvedLanguage="notebook" isNotebook mdViewMode="rich" />
+    )
+
+    expect(lifecycle.notebookProps).toHaveLength(1)
+    expect(lifecycle.notebookProps[0]).toMatchObject({
+      fileId: notebook.id,
+      filePath: notebook.filePath,
+      worktreeId: notebook.worktreeId,
+      scrollCacheKey: `${notebook.filePath}::same-pane:notebook`,
+      onContentChange: notebookProps.handleContentChange,
+      onSave: notebookProps.handleSave
+    })
+  })
+
+  it('forwards SSH and runtime ownership to rich markdown after extraction', () => {
+    const markdown = file('/repo/notes.md', {
+      language: 'markdown',
+      externalSshTargetId: 'ssh-target',
+      runtimeEnvironmentId: 'runtime-environment'
+    })
+
+    render(
+      <EditorContent
+        {...props(markdown, '# Notes')}
+        resolvedLanguage="markdown"
+        isMarkdown
+        mdViewMode="rich"
+      />
+    )
+
+    expect(lifecycle.richMarkdownProps).toHaveLength(1)
+    expect(lifecycle.richMarkdownProps[0]).toMatchObject({
+      externalSshTargetId: 'ssh-target',
+      runtimeEnvironmentId: 'runtime-environment',
+      worktreeId: markdown.worktreeId
+    })
+  })
 })
diff --git a/src/renderer/src/components/editor/EditorContent.tsx b/src/renderer/src/components/editor/EditorContent.tsx
index 01be65d3465..ca12823e846 100644
--- a/src/renderer/src/components/editor/EditorContent.tsx
+++ b/src/renderer/src/components/editor/EditorContent.tsx
@@ -1,59 +1,24 @@
-/* eslint-disable max-lines -- Why: dispatch surface for every editor mode; keeping the mode-selection branches colocated beats scattering the switch across per-mode wrappers. */
-import React from 'react'
-import { lazyWithRetry as lazy } from '@/lib/lazy-with-retry'
-import { AlertCircle, RefreshCw } from 'lucide-react'
-import { detectLanguage } from '@/lib/language-detect'
-import { joinPath } from '@/lib/path'
 import { useAppStore } from '@/store'
-import { Button } from '@/components/ui/button'
-import { ChangesModeView } from './ChangesModeView'
-import {
-  ConflictBanner,
-  ConflictPlaceholderView,
-  ConflictReviewPanel,
-  getNextConflictNavigationIndex
-} from './ConflictComponents'
 import type { MarkdownViewMode, OpenFile, PendingEditorReveal } from '@/store/slices/editor'
 import type { GitDiffResult } from '../../../../shared/git-diff-compare-types'
 import type { GitStatusEntry } from '../../../../shared/git-status-types'
-import { getMarkdownRenderMode } from './markdown-render-mode'
-import { getMarkdownRichModeUnsupportedMessage } from './markdown-rich-mode'
-import { exceedsMarkdownRichModeSizeLimit } from './markdown-rich-size-limit'
-import { extractFrontMatter, prependFrontMatter } from './markdown-frontmatter'
-import { RichMarkdownErrorBoundary } from './RichMarkdownErrorBoundary'
-import { useMarkdownDocuments } from './useMarkdownDocuments'
-import {
-  findGitConflictBlocks,
-  getGitConflictMarkerLineLength
-} from './monaco-conflict-decorations'
-import { getDiffContentSignature } from './diff-content-signature'
-import { translate } from '@/i18n/i18n'
 import { CheckRunDetailsPanel } from './CheckRunDetailsPanel'
-import { ExternalFileChangeBanner } from './ExternalFileChangeBanner'
+import { CombinedDiffViewer, MarkdownPreview } from './editor-lazy-views'
+import { EditorConflictReviewSurface } from './EditorConflictReviewSurface'
+import { EditorDiffFileSurface } from './EditorDiffFileSurface'
+import { EditorEditFileSurface } from './EditorEditFileSurface'
+import { EditorFileLoadErrorView } from './EditorFileLoadErrorView'
+import type { FileContent } from './editor-panel-content-types'
+import { translate } from '@/i18n/i18n'
+import { useEditorConflictNavigation } from './useEditorConflictNavigation'
+import { useMarkdownDocuments } from './useMarkdownDocuments'
 
-const MonacoEditor = lazy(() => import('./MonacoEditor'))
-const DiffViewer = lazy(() => import('./DiffViewer'))
-const CombinedDiffViewer = lazy(() => import('./CombinedDiffViewer'))
-const RichMarkdownEditor = lazy(() => import('./RichMarkdownEditor'), {
-  reloadKey: 'rich-markdown-editor'
-})
-const MarkdownPreview = lazy(() => import('./MarkdownPreview'))
-const ImageViewer = lazy(() => import('./ImageViewer'))
-const ImageDiffViewer = lazy(() => import('./ImageDiffViewer'))
-const MermaidViewer = lazy(() => import('./MermaidViewer'))
-const CsvViewer = lazy(() => import('./CsvViewer'))
-const IpynbViewer = lazy(() => import('./IpynbViewer'))
-
-// Why: module-level for a stable no-op identity so read-only tabs don't rebuild callbacks each render.
-const noopEditorContentChange = (_content: string): void => {}
-const noopEditorSave = async (_content: string): Promise<boolean> => false
+const noopCloseMarkdownTableOfContents = (): void => {}
 
 export function getMarkdownSourceLineOffset(frontMatterRaw: string): number {
   let offset = 0
-
   for (let index = 0; index < frontMatterRaw.length; index++) {
     const code = frontMatterRaw.charCodeAt(index)
-
     if (code === 13) {
       offset++
       if (frontMatterRaw.charCodeAt(index + 1) === 10) {
@@ -61,61 +26,13 @@ export function getMarkdownSourceLineOffset(frontMatterRaw: string): number {
       }
       continue
     }
-
     if (code === 10) {
       offset++
     }
   }
-
   return offset
 }
 
-type FileContent = {
-  content: string
-  isBinary: boolean
-  isImage?: boolean
-  mimeType?: string
-  loadError?: string
-}
-
-const noopCloseMarkdownTableOfContents = (): void => {}
-
-function matchesPendingEditorReveal(
-  reveal: PendingEditorReveal | null,
-  file: Pick<OpenFile, 'id' | 'filePath'>
-): reveal is PendingEditorReveal {
-  if (!reveal) {
-    return false
-  }
-  return reveal.fileId ? reveal.fileId === file.id : reveal.filePath === file.filePath
-}
-
-function FileLoadErrorView({
-  message,
-  onRetry
-}: {
-  message: string
-  onRetry: () => void
-}): React.JSX.Element {
-  return (
-    <div className="flex h-full items-center justify-center bg-editor-surface p-6 text-sm text-muted-foreground">
-      <div className="flex max-w-xl items-start gap-3 rounded-md border border-border bg-background p-4">
-        <AlertCircle className="mt-0.5 size-4 flex-shrink-0 text-destructive" />
-        <div className="min-w-0">
-          <div className="font-medium text-foreground">
-            {translate('auto.components.editor.EditorContent.39f018b052', 'Unable to load file')}
-          </div>
-          <div className="mt-1 break-words">{message}</div>
-          <Button type="button" variant="outline" size="sm" className="mt-3" onClick={onRetry}>
-            <RefreshCw className="size-3.5" />
-            {translate('auto.components.editor.EditorContent.2a512bb46a', 'Retry')}
-          </Button>
-        </div>
-      </div>
-    </div>
-  )
-}
-
 export function EditorContent({
   activeFile,
   viewStateScopeId,
@@ -181,31 +98,17 @@ export function EditorContent({
     viewStateScopeId === activeFile.id
       ? `${activeFile.id}:preview`
       : `${activeFile.id}::${viewStateScopeId}:preview`
-  // Why: only the single-pane edit path gets PDF scroll memory — the diff and
-  // conflict-review paths mount several viewers on one path (see PdfViewer).
+  // Why: only the single-pane edit path gets PDF scroll memory — diff and conflict review mount several viewers on one path.
   const pdfViewStateKey =
     viewStateScopeId === activeFile.id
       ? `${activeFile.filePath}:pdf`
       : `${activeFile.filePath}::${viewStateScopeId}:pdf`
   const monacoLanguage = resolvedLanguage === 'notebook' ? 'json' : resolvedLanguage
-
-  const openConflictReviewFile = useAppStore((s) => s.openConflictReviewFile)
-  const openConflictReview = useAppStore((s) => s.openConflictReview)
-  const closeFile = useAppStore((s) => s.closeFile)
-  const setRightSidebarTab = useAppStore((s) => s.setRightSidebarTab)
-  const setPendingEditorReveal = useAppStore((s) => s.setPendingEditorReveal)
-  const reloadOpenCheckRunDetailsTab = useAppStore((s) => s.reloadOpenCheckRunDetailsTab)
-  const [conflictNavigationIndexByFile, setConflictNavigationIndexByFile] = React.useState<
-    Record<string, number>
-  >({})
-  const md = useMarkdownDocuments(activeFile, isMarkdown, mdViewMode, handleSave)
+  const reloadOpenCheckRunDetailsTab = useAppStore((state) => state.reloadOpenCheckRunDetailsTab)
+  const markdownDocuments = useMarkdownDocuments(activeFile, isMarkdown, mdViewMode, handleSave)
+  const getConflictNavigation = useEditorConflictNavigation()
   const activeConflictEntry =
     worktreeEntries.find((entry) => entry.path === activeFile.relativePath) ?? null
-  const selectedConflictReviewFile =
-    activeFile.mode === 'conflict-review' && activeFile.conflictReview?.selectedFileId
-      ? (openFiles.find((file) => file.id === activeFile.conflictReview?.selectedFileId) ?? null)
-      : null
-
   const isCombinedDiff =
     activeFile.mode === 'diff' &&
     (activeFile.diffSource === 'combined-all' ||
@@ -213,408 +116,6 @@ export function EditorContent({
       activeFile.diffSource === 'combined-branch' ||
       activeFile.diffSource === 'combined-commit')
 
-  const getConflictNavigation = React.useCallback(
-    (file: OpenFile, content: string) => {
-      const blocks = findGitConflictBlocks(content)
-      if (blocks.length === 0) {
-        return undefined
-      }
-
-      const currentIndex = conflictNavigationIndexByFile[file.id] ?? null
-      return {
-        currentIndex,
-        total: blocks.length,
-        onJump: (direction: 'previous' | 'next') => {
-          const nextIndex = getNextConflictNavigationIndex({
-            currentIndex,
-            direction,
-            total: blocks.length
-          })
-          if (nextIndex === null) {
-            return
-          }
-          const line = blocks[nextIndex].startLine
-          const markerLineLength = getGitConflictMarkerLineLength(content, line)
-          setConflictNavigationIndexByFile((prev) => ({ ...prev, [file.id]: nextIndex }))
-          // Why: clear first so a repeated same-location reveal still changes the prop and re-runs the editor's reveal effect.
-          setPendingEditorReveal(null)
-          queueMicrotask(() => {
-            setPendingEditorReveal({
-              filePath: file.filePath,
-              line,
-              column: 1,
-              matchLength: markerLineLength
-            })
-          })
-        }
-      }
-    },
-    [conflictNavigationIndexByFile, setPendingEditorReveal]
-  )
-  const openConflictEntry = React.useCallback(
-    (entry: GitStatusEntry) => {
-      if (activeFile.mode !== 'conflict-review') {
-        return
-      }
-      openConflictReviewFile(
-        activeFile.id,
-        activeFile.worktreeId,
-        activeFile.filePath,
-        entry,
-        detectLanguage(entry.path)
-      )
-    },
-    [
-      activeFile.filePath,
-      activeFile.id,
-      activeFile.mode,
-      activeFile.worktreeId,
-      openConflictReviewFile
-    ]
-  )
-
-  const createConflictReviewContentFile = (entry: GitStatusEntry): OpenFile => {
-    const absolutePath = joinPath(activeFile.filePath, entry.path)
-    const conflict =
-      entry.conflictKind && entry.conflictStatus && entry.conflictStatusSource
-        ? entry.status === 'deleted'
-          ? {
-              kind: 'conflict-placeholder' as const,
-              conflictKind: entry.conflictKind,
-              conflictStatus: entry.conflictStatus,
-              conflictStatusSource: entry.conflictStatusSource,
-              message: translate(
-                'auto.components.editor.EditorContent.8b1a605bae',
-                'This file is in a conflict state, but no working-tree file is available to edit.'
-              ),
-              guidance: 'Resolve the conflict in Git or restore one side before reopening it.'
-            }
-          : {
-              kind: 'conflict-editable' as const,
-              conflictKind: entry.conflictKind,
-              conflictStatus: entry.conflictStatus,
-              conflictStatusSource: entry.conflictStatusSource
-            }
-        : undefined
-
-    return {
-      id: absolutePath,
-      filePath: absolutePath,
-      relativePath: entry.path,
-      worktreeId: activeFile.worktreeId,
-      language: detectLanguage(entry.path),
-      isDirty: false,
-      mode: 'edit',
-      conflict
-    }
-  }
-
-  const renderMonacoEditor = (fc: FileContent): React.JSX.Element => (
-    // Why: without a key React reuses the instance and skips cleanup (scroll snapshot); key forces a remount per pane+path.
-    <MonacoEditor
-      key={`${viewStateScopeId}\u0000${activeFile.filePath}`}
-      fileId={activeFile.id}
-      filePath={activeFile.filePath}
-      viewStateKey={editorViewStateKey}
-      viewStateId={viewStateScopeId}
-      relativePath={activeFile.relativePath}
-      content={editBuffers[activeFile.id] ?? fc.content}
-      language={monacoLanguage}
-      // Why: read-only tabs no-op the change/save callbacks so no draft, dirty state, or write can occur.
-      readOnly={activeFile.readOnly === true}
-      liveTail={activeFile.liveTail === true}
-      onContentChange={activeFile.readOnly === true ? noopEditorContentChange : handleContentChange}
-      onSave={activeFile.readOnly === true ? noopEditorSave : isMarkdown ? md.mdSave : handleSave}
-      worktreeId={activeFile.worktreeId}
-      markdownAnnotationsEnabled={markdownAnnotationsEnabled && isMarkdown}
-      conflictDecorationsEnabled={activeFile.conflict?.conflictStatus === 'unresolved'}
-      revealLine={
-        matchesPendingEditorReveal(pendingEditorReveal, activeFile)
-          ? pendingEditorReveal.line
-          : undefined
-      }
-      revealColumn={
-        matchesPendingEditorReveal(pendingEditorReveal, activeFile)
-          ? pendingEditorReveal.column
-          : undefined
-      }
-      revealMatchLength={
-        matchesPendingEditorReveal(pendingEditorReveal, activeFile)
-          ? pendingEditorReveal.matchLength
-          : undefined
-      }
-      markdownDocuments={isMarkdown ? md.markdownDocuments : undefined}
-    />
-  )
-
-  const renderMarkdownContent = (fc: FileContent): React.JSX.Element => {
-    const currentContent = editBuffers[activeFile.id] ?? fc.content
-    const richModeUnsupportedMessage = getMarkdownRichModeUnsupportedMessage(currentContent)
-    const renderMode = getMarkdownRenderMode({
-      exceedsRichModeSizeLimit: exceedsMarkdownRichModeSizeLimit(currentContent),
-      hasRichModeUnsupportedContent: richModeUnsupportedMessage !== null,
-      viewMode: mdViewMode
-    })
-
-    if (activeFile.conflict?.conflictStatus === 'unresolved') {
-      // Why: rich/preview modes hide the conflict-marker source text the user must edit directly.
-      return <div className="h-full min-h-0">{renderMonacoEditor(fc)}</div>
-    }
-
-    // Why: banner explains why the "rich" view is showing Monaco source (size forced a source-mode fallback).
-    if (renderMode === 'source' && mdViewMode === 'rich') {
-      const richFallbackMessage =
-        richModeUnsupportedMessage ??
-        'File is too large for rich editing. Showing source mode instead.'
-      return (
-        <div className="flex h-full min-h-0 flex-col">
-          <div className="border-b border-border/60 bg-blue-500/10 px-3 py-2 text-xs text-blue-950 dark:text-blue-100">
-            {richFallbackMessage}
-          </div>
-          <div className="min-h-0 flex-1 h-full">{renderMonacoEditor(fc)}</div>
-        </div>
-      )
-    }
-
-    if (renderMode === 'rich-editor') {
-      // Why: Tiptap has no front-matter node and would drop it, so strip it here and recombine on change/save.
-      const fm = extractFrontMatter(currentContent)
-      const editorContent = fm ? fm.body : currentContent
-
-      const onContentChangeWithFm = fm
-        ? (body: string): void => handleContentChange(prependFrontMatter(fm.raw, body))
-        : handleContentChange
-
-      const onSaveWithFm = fm
-        ? (body: string): Promise<boolean> => md.mdSave(prependFrontMatter(fm.raw, body))
-        : md.mdSave
-
-      return (
-        <div className="flex h-full min-h-0 flex-col">
-          <div className="min-h-0 flex-1">
-            {/* Why: keyed for remount like MonacoEditor; boundary contains a TipTap render crash (issue #826) to this pane. */}
-            <RichMarkdownErrorBoundary key={viewStateScopeId} fileId={activeFile.id}>
-              <RichMarkdownEditor
-                fileId={activeFile.id}
-                viewStateId={viewStateScopeId}
-                content={editorContent}
-                filePath={activeFile.filePath}
-                worktreeId={activeFile.worktreeId}
-                externalSshTargetId={activeFile.externalSshTargetId}
-                runtimeEnvironmentId={activeFile.runtimeEnvironmentId}
-                scrollCacheKey={`${editorViewStateKey}:rich`}
-                onContentChange={onContentChangeWithFm}
-                onDirtyStateHint={handleDirtyStateHint}
-                onSave={onSaveWithFm}
-                onOpenDocLink={md.onOpenDocLink}
-                markdownDocuments={md.markdownDocuments}
-                showTableOfContents={showMarkdownTableOfContents}
-                onCloseTableOfContents={onCloseMarkdownTableOfContents}
-                markdownAnnotationsEnabled={markdownAnnotationsEnabled}
-                markdownAnnotationFilePath={activeFile.relativePath}
-                markdownSourceLineOffset={fm ? getMarkdownSourceLineOffset(fm.raw) : 0}
-                markdownReviewContent={currentContent}
-                // Why: banner goes below the toolbar (inside the editor shell) so formatting controls stay at the top of the pane.
-                headerSlot={
-                  fm && showMarkdownFrontmatter ? <FrontMatterBanner raw={fm.raw} /> : null
-                }
-              />
-            </RichMarkdownErrorBoundary>
-          </div>
-        </div>
-      )
-    }
-
-    if (renderMode === 'preview') {
-      const shouldExplainRichFallback = mdViewMode === 'rich' && richModeUnsupportedMessage
-      return (
-        <div className="flex h-full min-h-0 flex-col">
-          {shouldExplainRichFallback ? (
-            <div className="border-b border-border/60 bg-amber-500/10 px-3 py-2 text-xs text-amber-950 dark:text-amber-100">
-              {richModeUnsupportedMessage}
-            </div>
-          ) : null}
-          {/* Why: fall back to the stable preview renderer when Tiptap can't safely own the document. */}
-          <div className="min-h-0 flex-1">
-            <MarkdownPreview
-              key={viewStateScopeId}
-              content={currentContent}
-              filePath={activeFile.filePath}
-              sourceFileId={activeFile.id}
-              sourceWorktreeId={activeFile.worktreeId}
-              sourceRuntimeEnvironmentId={activeFile.runtimeEnvironmentId}
-              scrollCacheKey={`${editorViewStateKey}:preview`}
-              showTableOfContents={showMarkdownTableOfContents}
-              onCloseTableOfContents={onCloseMarkdownTableOfContents}
-              markdownAnnotationsEnabled={markdownAnnotationsEnabled}
-              {...md.previewProps}
-            />
-          </div>
-        </div>
-      )
-    }
-
-    // Why: Monaco with height="100%" sizes to its immediate parent, so the wrapper needs an explicit height or it collapses.
-    return <div className="h-full min-h-0">{renderMonacoEditor(fc)}</div>
-  }
-
-  const renderConflictReviewEditorContent = ({
-    contentFile,
-    entry,
-    className,
-    viewStateKeySuffix,
-    readOnly = false,
-    autoHeight = false
-  }: {
-    contentFile: OpenFile
-    entry: GitStatusEntry | null
-    className: string
-    viewStateKeySuffix: string
-    readOnly?: boolean
-    autoHeight?: boolean
-  }): React.JSX.Element => {
-    if (contentFile.conflict?.kind === 'conflict-placeholder') {
-      return (
-        <div className={className}>
-          <ConflictPlaceholderView file={contentFile} />
-        </div>
-      )
-    }
-
-    const fc = fileContents[contentFile.id]
-    if (!fc) {
-      return (
-        <div className={className}>
-          <div className="flex h-full items-center justify-center text-sm text-muted-foreground">
-            {translate('auto.components.editor.EditorContent.b2735221f5', 'Loading...')}
-          </div>
-        </div>
-      )
-    }
-    if (fc.loadError) {
-      return (
-        <div className={className}>
-          <FileLoadErrorView message={fc.loadError} onRetry={() => reloadContent(contentFile)} />
-        </div>
-      )
-    }
-    if (fc.isBinary) {
-      if (fc.isImage) {
-        return (
-          <div className={className}>
-            <ImageViewer
-              content={fc.content}
-              filePath={contentFile.filePath}
-              mimeType={fc.mimeType}
-            />
-          </div>
-        )
-      }
-      return (
-        <div className={className}>
-          <div className="flex h-full items-center justify-center text-sm text-muted-foreground">
-            {translate(
-              'auto.components.editor.EditorContent.b9de81ba52',
-              'Binary file — cannot display'
-            )}
-          </div>
-        </div>
-      )
-    }
-
-    const selectedLanguage = detectLanguage(contentFile.relativePath)
-    const monacoSelectedLanguage = selectedLanguage === 'notebook' ? 'json' : selectedLanguage
-    const selectedViewStateKey = `${contentFile.filePath}::${viewStateScopeId}:${viewStateKeySuffix}`
-    const selectedContent = editBuffers[contentFile.id] ?? fc.content
-
-    return (
-      <div className={className}>
-        {contentFile.conflict && (
-          <ConflictBanner
-            file={contentFile}
-            entry={entry}
-            conflictNavigation={getConflictNavigation(contentFile, selectedContent)}
-          />
-        )}
-        <div className={autoHeight ? 'shrink-0' : 'min-h-0 flex-1'}>
-          <MonacoEditor
-            key={`${viewStateScopeId}:${contentFile.id}:${viewStateKeySuffix}`}
-            fileId={contentFile.id}
-            filePath={contentFile.filePath}
-            viewStateKey={selectedViewStateKey}
-            relativePath={contentFile.relativePath}
-            content={selectedContent}
-            language={monacoSelectedLanguage}
-            onContentChange={
-              readOnly ? () => {} : (content) => handleContentChangeForFile(contentFile, content)
-            }
-            onSave={readOnly ? () => {} : (content) => handleSaveForFile(contentFile, content)}
-            worktreeId={contentFile.worktreeId}
-            markdownAnnotationsEnabled={false}
-            conflictDecorationsEnabled={contentFile.conflict?.conflictStatus === 'unresolved'}
-            readOnly={readOnly}
-            autoHeight={autoHeight}
-            revealLine={
-              matchesPendingEditorReveal(pendingEditorReveal, contentFile)
-                ? pendingEditorReveal.line
-                : undefined
-            }
-            revealColumn={
-              matchesPendingEditorReveal(pendingEditorReveal, contentFile)
-                ? pendingEditorReveal.column
-                : undefined
-            }
-            revealMatchLength={
-              matchesPendingEditorReveal(pendingEditorReveal, contentFile)
-                ? pendingEditorReveal.matchLength
-                : undefined
-            }
-          />
-        </div>
-      </div>
-    )
-  }
-
-  const renderConflictReviewSelectedContent = (selectedFile: OpenFile): React.JSX.Element => {
-    const selectedConflictEntry =
-      worktreeEntries.find((entry) => entry.path === selectedFile.relativePath) ?? null
-
-    return renderConflictReviewEditorContent({
-      contentFile: selectedFile,
-      entry: selectedConflictEntry,
-      className: 'flex min-h-0 flex-1 flex-col',
-      viewStateKeySuffix: 'selected'
-    })
-  }
-
-  const renderConflictReviewInlineFile = (entry: GitStatusEntry): React.JSX.Element => {
-    const contentFile = createConflictReviewContentFile(entry)
-
-    return renderConflictReviewEditorContent({
-      contentFile,
-      entry,
-      className: 'flex min-h-[120px] flex-col border-b border-border last:border-b-0',
-      viewStateKeySuffix: `overview:${entry.path}`,
-      readOnly: true,
-      autoHeight: true
-    })
-  }
-
-  const renderConflictReviewAllContent = (): React.JSX.Element => {
-    const snapshotEntries = activeFile.conflictReview?.entries ?? []
-    const liveEntriesByPath = new Map(worktreeEntries.map((entry) => [entry.path, entry]))
-    const unresolvedEntries = snapshotEntries.flatMap((entry) => {
-      const liveEntry = liveEntriesByPath.get(entry.path)
-      return liveEntry?.conflictStatus === 'unresolved' && liveEntry.conflictKind ? [liveEntry] : []
-    })
-
-    return (
-      <div className="min-h-0 flex-1 overflow-y-auto bg-editor-surface scrollbar-sleek">
-        {unresolvedEntries.map(renderConflictReviewInlineFile)}
-      </div>
-    )
-  }
-
   if (activeFile.mode === 'check-details') {
     const checkRunDetails = activeFile.checkRunDetails
     if (!checkRunDetails) {
@@ -628,14 +129,13 @@ export function EditorContent({
       )
     }
     const details = checkRunDetails.details
-    const openUrl = details?.detailsUrl ?? details?.url ?? checkRunDetails.check.url
     return (
       <CheckRunDetailsPanel
         check={checkRunDetails.check}
-        details={checkRunDetails.details}
+        details={details}
         loading={checkRunDetails.loading}
         error={checkRunDetails.error}
-        openUrl={openUrl}
+        openUrl={details?.detailsUrl ?? details?.url ?? checkRunDetails.check.url}
         worktreeId={activeFile.worktreeId}
         onRefresh={() => {
           void reloadOpenCheckRunDetailsTab(activeFile.id)
@@ -646,31 +146,18 @@ export function EditorContent({
 
   if (activeFile.mode === 'conflict-review') {
     return (
-      <ConflictReviewPanel
-        file={activeFile}
-        liveEntries={worktreeEntries}
-        onOpenEntry={openConflictEntry}
-        selectedFile={selectedConflictReviewFile}
-        selectedContent={
-          selectedConflictReviewFile
-            ? renderConflictReviewSelectedContent(selectedConflictReviewFile)
-            : renderConflictReviewAllContent()
-        }
-        onDismiss={() => closeFile(activeFile.id)}
-        onRefreshSnapshot={() =>
-          openConflictReview(
-            activeFile.worktreeId,
-            activeFile.filePath,
-            worktreeEntries
-              .filter((entry) => entry.conflictStatus === 'unresolved' && entry.conflictKind)
-              .map((entry) => ({
-                path: entry.path,
-                conflictKind: entry.conflictKind!
-              })),
-            'live-summary'
-          )
-        }
-        onReturnToSourceControl={() => setRightSidebarTab('source-control')}
+      <EditorConflictReviewSurface
+        activeFile={activeFile}
+        viewStateScopeId={viewStateScopeId}
+        fileContents={fileContents}
+        editBuffers={editBuffers}
+        openFiles={openFiles}
+        worktreeEntries={worktreeEntries}
+        pendingEditorReveal={pendingEditorReveal}
+        getConflictNavigation={getConflictNavigation}
+        handleContentChangeForFile={handleContentChangeForFile}
+        handleSaveForFile={handleSaveForFile}
+        reloadContent={reloadContent}
       />
     )
   }
@@ -686,18 +173,23 @@ export function EditorContent({
   }
 
   if (activeFile.mode === 'markdown-preview') {
-    const fc = fileContents[activeFile.id]
-    if (!fc) {
+    const fileContent = fileContents[activeFile.id]
+    if (!fileContent) {
       return (
         <div className="flex items-center justify-center h-full text-muted-foreground text-sm">
           {translate('auto.components.editor.EditorContent.37a0e81fa6', 'Loading preview...')}
         </div>
       )
     }
-    if (fc.loadError) {
-      return <FileLoadErrorView message={fc.loadError} onRetry={() => reloadContent(activeFile)} />
+    if (fileContent.loadError) {
+      return (
+        <EditorFileLoadErrorView
+          message={fileContent.loadError}
+          onRetry={() => reloadContent(activeFile)}
+        />
+      )
     }
-    if (fc.isBinary) {
+    if (fileContent.isBinary) {
       return (
         <div className="flex h-full items-center justify-center px-6 text-center text-sm text-muted-foreground">
           {translate(
@@ -708,12 +200,11 @@ export function EditorContent({
       )
     }
     const previewSourceFileId = activeFile.markdownPreviewSourceFileId ?? activeFile.filePath
-    const previewContent = editBuffers[previewSourceFileId] ?? fc.content
     return (
       <div className="min-h-0 flex-1">
         <MarkdownPreview
           key={viewStateScopeId}
-          content={previewContent}
+          content={editBuffers[previewSourceFileId] ?? fileContent.content}
           filePath={activeFile.filePath}
           sourceFileId={previewSourceFileId}
           sourceWorktreeId={activeFile.worktreeId}
@@ -723,273 +214,66 @@ export function EditorContent({
           showTableOfContents={showMarkdownTableOfContents}
           onCloseTableOfContents={onCloseMarkdownTableOfContents}
           markdownAnnotationsEnabled={markdownAnnotationsEnabled}
-          {...md.previewProps}
+          {...markdownDocuments.previewProps}
         />
       </div>
     )
   }
 
   if (activeFile.mode === 'edit') {
-    if (activeFile.conflict?.kind === 'conflict-placeholder') {
-      return <ConflictPlaceholderView file={activeFile} />
-    }
-    const fc = fileContents[activeFile.id]
-    if (!fc) {
-      return (
-        <div className="flex items-center justify-center h-full text-muted-foreground text-sm">
-          {translate('auto.components.editor.EditorContent.b2735221f5', 'Loading...')}
-        </div>
-      )
-    }
-    if (fc.loadError) {
-      return <FileLoadErrorView message={fc.loadError} onRetry={() => reloadContent(activeFile)} />
-    }
-    if (fc.isBinary) {
-      if (fc.isImage) {
-        return (
-          <ImageViewer
-            content={fc.content}
-            filePath={activeFile.filePath}
-            mimeType={fc.mimeType}
-            scrollCacheKey={pdfViewStateKey}
-          />
-        )
-      }
-      return (
-        <div className="flex items-center justify-center h-full text-muted-foreground text-sm">
-          {translate(
-            'auto.components.editor.EditorContent.b9de81ba52',
-            'Binary file — cannot display'
-          )}
-        </div>
-      )
-    }
-    const externalChangeBanner =
-      activeFile.externalMutation === 'changed' ? (
-        <ExternalFileChangeBanner
-          file={activeFile}
-          currentContent={editBuffers[activeFile.id] ?? fc.content}
-          reloadContent={reloadContent}
-        />
-      ) : null
-    if (isChangesMode) {
-      const changesView = (
-        <ChangesModeView
-          activeFile={activeFile}
-          dc={diffContents[activeFile.id]}
-          modifiedContent={editBuffers[activeFile.id] ?? fc.content}
-          activeConflictEntry={activeConflictEntry}
-          resolvedLanguage={monacoLanguage}
-          sideBySide={sideBySide}
-          viewStateScopeId={viewStateScopeId}
-          diffViewStateKey={diffViewStateKey}
-          onContentChange={handleContentChange}
-          onSave={isMarkdown ? md.mdSave : handleSave}
-        />
-      )
-      if (!externalChangeBanner) {
-        return changesView
-      }
-      return (
-        <div className="flex flex-1 min-h-0 flex-col">
-          {externalChangeBanner}
-          <div className="min-h-0 flex-1">{changesView}</div>
-        </div>
-      )
-    }
     return (
-      <div className="flex flex-1 min-h-0 flex-col">
-        {externalChangeBanner}
-        {activeFile.conflict && (
-          <ConflictBanner
-            file={activeFile}
-            entry={activeConflictEntry}
-            conflictNavigation={getConflictNavigation(
-              activeFile,
-              editBuffers[activeFile.id] ?? fc.content
-            )}
-          />
-        )}
-        <div className="min-h-0 flex-1 relative">
-          {isMarkdown ? (
-            renderMarkdownContent(fc)
-          ) : isMermaid && mdViewMode === 'rich' ? (
-            <MermaidViewer
-              key={activeFile.id}
-              content={editBuffers[activeFile.id] ?? fc.content}
-              filePath={activeFile.filePath}
-            />
-          ) : isCsv && mdViewMode === 'rich' ? (
-            <CsvViewer
-              key={activeFile.id}
-              content={editBuffers[activeFile.id] ?? fc.content}
-              filePath={activeFile.filePath}
-            />
-          ) : isNotebook && mdViewMode === 'rich' ? (
-            <IpynbViewer
-              key={activeFile.id}
-              content={editBuffers[activeFile.id] ?? fc.content}
-              fileId={activeFile.id}
-              filePath={activeFile.filePath}
-              worktreeId={activeFile.worktreeId}
-              scrollCacheKey={`${editorViewStateKey}:notebook`}
-              onContentChange={handleContentChange}
-              onDirtyStateHint={handleDirtyStateHint}
-              onSave={handleSave}
-            />
-          ) : (
-            renderMonacoEditor(fc)
-          )}
-        </div>
-      </div>
-    )
-  }
-
-  // Diff mode
-  const dc = diffContents[activeFile.id]
-  if (!dc) {
-    return (
-      <div className="flex items-center justify-center h-full text-muted-foreground text-sm">
-        {translate('auto.components.editor.EditorContent.c88c73a0d3', 'Loading diff...')}
-      </div>
-    )
-  }
-  const isEditable = activeFile.diffSource === 'unstaged'
-  if (dc.kind === 'binary') {
-    if (dc.isImage) {
-      return (
-        <ImageDiffViewer
-          originalContent={dc.originalContent}
-          modifiedContent={dc.modifiedContent}
-          filePath={activeFile.relativePath}
-          mimeType={dc.mimeType}
-          sideBySide={sideBySide}
-        />
-      )
-    }
-    return (
-      <div className="flex h-full items-center justify-center px-6 text-center">
-        <div className="space-y-2">
-          <div className="text-sm font-medium text-foreground">
-            {translate('auto.components.editor.EditorContent.78541e254e', 'Binary file changed')}
-          </div>
-          <div className="text-xs text-muted-foreground">
-            {activeFile.diffSource === 'branch'
-              ? translate(
-                  'auto.components.editor.EditorContent.3c6e71df22',
-                  'Text diff is unavailable for this file in branch compare.'
-                )
-              : translate(
-                  'auto.components.editor.EditorContent.8a0898ae4c',
-                  'Text diff is unavailable for this file.'
-                )}
-          </div>
-        </div>
-      </div>
-    )
-  }
-  const modifiedDiffBuffer = editBuffers[activeFile.id]
-  const modifiedDiffContent = modifiedDiffBuffer ?? dc.modifiedContent
-  const largeDiffSaveContentAvailable = !(
-    dc.largeDiffRenderLimit?.limited === true &&
-    modifiedDiffBuffer === undefined &&
-    dc.modifiedContent.length === 0
-  )
-  // Why: shared by both diff sub-branches (preview and source) so preview mode surfaces the external change too.
-  const diffExternalChangeBanner =
-    activeFile.externalMutation === 'changed' ? (
-      <ExternalFileChangeBanner
-        file={activeFile}
-        currentContent={modifiedDiffContent}
+      <EditorEditFileSurface
+        activeFile={activeFile}
+        viewStateScopeId={viewStateScopeId}
+        editorViewStateKey={editorViewStateKey}
+        diffViewStateKey={diffViewStateKey}
+        pdfViewStateKey={pdfViewStateKey}
+        fileContent={fileContents[activeFile.id]}
+        diffContent={diffContents[activeFile.id]}
+        editBuffer={editBuffers[activeFile.id]}
+        activeConflictEntry={activeConflictEntry}
+        monacoLanguage={monacoLanguage}
+        isMarkdown={isMarkdown}
+        isMermaid={isMermaid}
+        isCsv={isCsv}
+        isNotebook={isNotebook}
+        mdViewMode={mdViewMode}
+        isChangesMode={isChangesMode}
+        sideBySide={sideBySide}
+        showMarkdownTableOfContents={showMarkdownTableOfContents}
+        showMarkdownFrontmatter={showMarkdownFrontmatter}
+        onCloseMarkdownTableOfContents={onCloseMarkdownTableOfContents}
+        markdownAnnotationsEnabled={markdownAnnotationsEnabled}
+        pendingEditorReveal={pendingEditorReveal}
+        markdownDocuments={markdownDocuments}
+        getConflictNavigation={getConflictNavigation}
+        getMarkdownSourceLineOffset={getMarkdownSourceLineOffset}
+        handleContentChange={handleContentChange}
+        handleDirtyStateHint={handleDirtyStateHint}
+        handleSave={handleSave}
         reloadContent={reloadContent}
       />
-    ) : null
-  if (isMarkdown && mdViewMode === 'preview' && dc.largeDiffRenderLimit?.limited !== true) {
-    return (
-      <div className="flex h-full min-h-0 flex-col">
-        {diffExternalChangeBanner}
-        <div className="border-b border-border/60 bg-muted/40 px-3 py-2 text-xs text-muted-foreground">
-          {/* Why: markdown preview can't show additions and deletions at once, so it shows only the modified side. */}
-          {translate(
-            'auto.components.editor.EditorContent.9640d1d3db',
-            'Previewing the modified version of this diff. Switch to source mode to inspect changes.'
-          )}
-        </div>
-        <div className="min-h-0 flex-1">
-          <MarkdownPreview
-            key={viewStateScopeId}
-            content={modifiedDiffContent}
-            filePath={activeFile.filePath}
-            sourceFileId={activeFile.id}
-            sourceWorktreeId={activeFile.worktreeId}
-            sourceRuntimeEnvironmentId={activeFile.runtimeEnvironmentId}
-            scrollCacheKey={`${diffViewStateKey}:preview`}
-            showTableOfContents={showMarkdownTableOfContents}
-            onCloseTableOfContents={onCloseMarkdownTableOfContents}
-            markdownAnnotationsEnabled={markdownAnnotationsEnabled}
-            {...md.previewProps}
-          />
-        </div>
-      </div>
     )
   }
-  // Why: key off fetched diff content + reload nonce (not the edit buffer) so Monaco reloads refreshed blobs but keeps undo.
-  const diffReloadNonce = activeFile.diffContentReloadNonce ?? 0
-  const originalModelKey = `${diffViewStateKey}:original:${getDiffContentSignature(dc.originalContent)}`
-  const modifiedModelKey = `${diffViewStateKey}:modified:${getDiffContentSignature(dc.modifiedContent)}:${diffReloadNonce}`
-  const diffViewer = (
-    <DiffViewer
-      // Why: content refreshes via modifiedModelKey; keying off content too would remount Monaco and flash on every save.
-      key={`${viewStateScopeId}:${diffReloadNonce}`}
-      modelKey={diffViewStateKey}
-      originalModelKey={originalModelKey}
-      modifiedModelKey={modifiedModelKey}
-      originalContent={dc.originalContent}
-      modifiedContent={modifiedDiffContent}
-      largeDiffRenderLimit={dc.largeDiffRenderLimit}
-      largeDiffSaveContentAvailable={largeDiffSaveContentAvailable}
-      language={monacoLanguage}
-      filePath={activeFile.filePath}
-      relativePath={activeFile.relativePath}
+
+  return (
+    <EditorDiffFileSurface
+      activeFile={activeFile}
+      diffContent={diffContents[activeFile.id]}
+      editBuffer={editBuffers[activeFile.id]}
+      resolvedLanguage={monacoLanguage}
       sideBySide={sideBySide}
-      editable={isEditable}
-      worktreeId={activeFile.worktreeId}
-      onContentChange={isEditable ? handleContentChange : undefined}
-      onSave={isEditable ? (isMarkdown ? md.mdSave : handleSave) : undefined}
+      viewStateScopeId={viewStateScopeId}
+      diffViewStateKey={diffViewStateKey}
+      mdViewMode={mdViewMode}
+      isMarkdown={isMarkdown}
+      showMarkdownTableOfContents={showMarkdownTableOfContents}
+      onCloseMarkdownTableOfContents={onCloseMarkdownTableOfContents}
+      markdownAnnotationsEnabled={markdownAnnotationsEnabled}
+      markdownDocuments={markdownDocuments}
+      onContentChange={handleContentChange}
+      onSave={handleSave}
+      reloadContent={reloadContent}
     />
   )
-  // Why: editable diffs get the changed-on-disk banner; its reload refetches the diff body, not plain file content.
-  if (activeFile.externalMutation !== 'changed') {
-    return diffViewer
-  }
-  return (
-    // Why: parent isn't a flex container, so flex-1 collapses to 0px — use h-full here and a flex column inside.
-    <div className="flex h-full min-h-0 flex-col">
-      {diffExternalChangeBanner}
-      <div className="flex min-h-0 flex-1 flex-col">{diffViewer}</div>
-    </div>
-  )
-}
-
-// Why: no collapsible state — layout shifts would interfere with ProseMirror's scroll management.
-function FrontMatterBanner({ raw }: { raw: string }): React.JSX.Element {
-  // Strip the opening/closing delimiters to show only the YAML/TOML content.
-  const inner = raw
-    .replace(/^(?:---|\+\+\+)\r?\n/, '')
-    .replace(/\r?\n(?:---|\+\+\+)\r?\n?$/, '')
-    .trim()
-
-  return (
-    <div className="border-b border-border/60 bg-muted/40 px-3 py-2">
-      <div className="mb-1 text-[10px] font-medium uppercase tracking-wider text-muted-foreground">
-        {translate('auto.components.editor.EditorContent.e4b074749d', 'Front Matter')}
-        <span className="ml-2 font-normal normal-case tracking-normal opacity-70">
-          {translate('auto.components.editor.EditorContent.56dba34e1a', '(edit in source mode)')}
-        </span>
-      </div>
-      <pre className="max-h-32 overflow-auto whitespace-pre-wrap text-xs text-muted-foreground font-mono scrollbar-editor">
-        {inner}
-      </pre>
-    </div>
-  )
 }
diff --git a/src/renderer/src/components/editor/EditorDiffFileSurface.tsx b/src/renderer/src/components/editor/EditorDiffFileSurface.tsx
new file mode 100644
index 00000000000..1597e3cef27
--- /dev/null
+++ b/src/renderer/src/components/editor/EditorDiffFileSurface.tsx
@@ -0,0 +1,172 @@
+import { translate } from '@/i18n/i18n'
+import type { OpenFile } from '@/store/slices/editor'
+import type { GitDiffResult } from '../../../../shared/git-diff-compare-types'
+import { getDiffContentSignature } from './diff-content-signature'
+import { DiffViewer, ImageDiffViewer, MarkdownPreview } from './editor-lazy-views'
+import { ExternalFileChangeBanner } from './ExternalFileChangeBanner'
+import type { useMarkdownDocuments } from './useMarkdownDocuments'
+
+type MarkdownDocumentsController = ReturnType<typeof useMarkdownDocuments>
+
+export function EditorDiffFileSurface({
+  activeFile,
+  diffContent,
+  editBuffer,
+  resolvedLanguage,
+  sideBySide,
+  viewStateScopeId,
+  diffViewStateKey,
+  mdViewMode,
+  isMarkdown,
+  showMarkdownTableOfContents,
+  onCloseMarkdownTableOfContents,
+  markdownAnnotationsEnabled,
+  markdownDocuments,
+  onContentChange,
+  onSave,
+  reloadContent
+}: {
+  activeFile: OpenFile
+  diffContent: GitDiffResult | undefined
+  editBuffer: string | undefined
+  resolvedLanguage: string
+  sideBySide: boolean
+  viewStateScopeId: string
+  diffViewStateKey: string
+  mdViewMode: 'source' | 'preview' | 'rich'
+  isMarkdown: boolean
+  showMarkdownTableOfContents: boolean
+  onCloseMarkdownTableOfContents: () => void
+  markdownAnnotationsEnabled: boolean
+  markdownDocuments: MarkdownDocumentsController
+  onContentChange: (content: string) => void
+  onSave: (content: string) => Promise<boolean>
+  reloadContent: (file: OpenFile) => void
+}): React.JSX.Element {
+  if (!diffContent) {
+    return (
+      <div className="flex items-center justify-center h-full text-muted-foreground text-sm">
+        {translate('auto.components.editor.EditorContent.c88c73a0d3', 'Loading diff...')}
+      </div>
+    )
+  }
+
+  const isEditable = activeFile.diffSource === 'unstaged'
+  if (diffContent.kind === 'binary') {
+    if (diffContent.isImage) {
+      return (
+        <ImageDiffViewer
+          originalContent={diffContent.originalContent}
+          modifiedContent={diffContent.modifiedContent}
+          filePath={activeFile.relativePath}
+          mimeType={diffContent.mimeType}
+          sideBySide={sideBySide}
+        />
+      )
+    }
+    return (
+      <div className="flex h-full items-center justify-center px-6 text-center">
+        <div className="space-y-2">
+          <div className="text-sm font-medium text-foreground">
+            {translate('auto.components.editor.EditorContent.78541e254e', 'Binary file changed')}
+          </div>
+          <div className="text-xs text-muted-foreground">
+            {activeFile.diffSource === 'branch'
+              ? translate(
+                  'auto.components.editor.EditorContent.3c6e71df22',
+                  'Text diff is unavailable for this file in branch compare.'
+                )
+              : translate(
+                  'auto.components.editor.EditorContent.8a0898ae4c',
+                  'Text diff is unavailable for this file.'
+                )}
+          </div>
+        </div>
+      </div>
+    )
+  }
+
+  const modifiedDiffContent = editBuffer ?? diffContent.modifiedContent
+  const largeDiffSaveContentAvailable = !(
+    diffContent.largeDiffRenderLimit?.limited === true &&
+    editBuffer === undefined &&
+    diffContent.modifiedContent.length === 0
+  )
+  const externalChangeBanner =
+    activeFile.externalMutation === 'changed' ? (
+      <ExternalFileChangeBanner
+        file={activeFile}
+        currentContent={modifiedDiffContent}
+        reloadContent={reloadContent}
+      />
+    ) : null
+
+  if (
+    isMarkdown &&
+    mdViewMode === 'preview' &&
+    diffContent.largeDiffRenderLimit?.limited !== true
+  ) {
+    return (
+      <div className="flex h-full min-h-0 flex-col">
+        {externalChangeBanner}
+        <div className="border-b border-border/60 bg-muted/40 px-3 py-2 text-xs text-muted-foreground">
+          {/* Why: markdown preview can't show additions and deletions at once, so it shows only the modified side. */}
+          {translate(
+            'auto.components.editor.EditorContent.9640d1d3db',
+            'Previewing the modified version of this diff. Switch to source mode to inspect changes.'
+          )}
+        </div>
+        <div className="min-h-0 flex-1">
+          <MarkdownPreview
+            key={viewStateScopeId}
+            content={modifiedDiffContent}
+            filePath={activeFile.filePath}
+            sourceFileId={activeFile.id}
+            sourceWorktreeId={activeFile.worktreeId}
+            sourceRuntimeEnvironmentId={activeFile.runtimeEnvironmentId}
+            scrollCacheKey={`${diffViewStateKey}:preview`}
+            showTableOfContents={showMarkdownTableOfContents}
+            onCloseTableOfContents={onCloseMarkdownTableOfContents}
+            markdownAnnotationsEnabled={markdownAnnotationsEnabled}
+            {...markdownDocuments.previewProps}
+          />
+        </div>
+      </div>
+    )
+  }
+
+  const diffReloadNonce = activeFile.diffContentReloadNonce ?? 0
+  const originalModelKey = `${diffViewStateKey}:original:${getDiffContentSignature(diffContent.originalContent)}`
+  const modifiedModelKey = `${diffViewStateKey}:modified:${getDiffContentSignature(diffContent.modifiedContent)}:${diffReloadNonce}`
+  const diffViewer = (
+    <DiffViewer
+      // Why: content refreshes via modifiedModelKey; keying off content too would remount Monaco and flash on every save.
+      key={`${viewStateScopeId}:${diffReloadNonce}`}
+      modelKey={diffViewStateKey}
+      originalModelKey={originalModelKey}
+      modifiedModelKey={modifiedModelKey}
+      originalContent={diffContent.originalContent}
+      modifiedContent={modifiedDiffContent}
+      largeDiffRenderLimit={diffContent.largeDiffRenderLimit}
+      largeDiffSaveContentAvailable={largeDiffSaveContentAvailable}
+      language={resolvedLanguage}
+      filePath={activeFile.filePath}
+      relativePath={activeFile.relativePath}
+      sideBySide={sideBySide}
+      editable={isEditable}
+      worktreeId={activeFile.worktreeId}
+      onContentChange={isEditable ? onContentChange : undefined}
+      onSave={isEditable ? (isMarkdown ? markdownDocuments.mdSave : onSave) : undefined}
+    />
+  )
+  if (activeFile.externalMutation !== 'changed') {
+    return diffViewer
+  }
+  return (
+    // Why: parent isn't a flex container, so flex-1 collapses to 0px — use h-full here and a flex column inside.
+    <div className="flex h-full min-h-0 flex-col">
+      {externalChangeBanner}
+      <div className="flex min-h-0 flex-1 flex-col">{diffViewer}</div>
+    </div>
+  )
+}
diff --git a/src/renderer/src/components/editor/EditorEditFileSurface.tsx b/src/renderer/src/components/editor/EditorEditFileSurface.tsx
new file mode 100644
index 00000000000..d0b83539ee6
--- /dev/null
+++ b/src/renderer/src/components/editor/EditorEditFileSurface.tsx
@@ -0,0 +1,266 @@
+import { translate } from '@/i18n/i18n'
+import type { MarkdownViewMode, OpenFile, PendingEditorReveal } from '@/store/slices/editor'
+import type { GitDiffResult } from '../../../../shared/git-diff-compare-types'
+import type { GitStatusEntry } from '../../../../shared/git-status-types'
+import { ChangesModeView } from './ChangesModeView'
+import { ConflictBanner, ConflictPlaceholderView } from './ConflictComponents'
+import {
+  CsvViewer,
+  ImageViewer,
+  IpynbViewer,
+  MermaidViewer,
+  MonacoEditor
+} from './editor-lazy-views'
+import type { EditorConflictNavigation } from './useEditorConflictNavigation'
+import { EditorFileLoadErrorView } from './EditorFileLoadErrorView'
+import type { FileContent } from './editor-panel-content-types'
+import { ExternalFileChangeBanner } from './ExternalFileChangeBanner'
+import type { useMarkdownDocuments } from './useMarkdownDocuments'
+import { EditorMarkdownFileSurface } from './EditorMarkdownFileSurface'
+
+const noopEditorContentChange = (_content: string): void => {}
+const noopEditorSave = async (_content: string): Promise<boolean> => false
+
+type MarkdownDocumentsController = ReturnType<typeof useMarkdownDocuments>
+
+export function EditorEditFileSurface({
+  activeFile,
+  viewStateScopeId,
+  editorViewStateKey,
+  diffViewStateKey,
+  pdfViewStateKey,
+  fileContent,
+  diffContent,
+  editBuffer,
+  activeConflictEntry,
+  monacoLanguage,
+  isMarkdown,
+  isMermaid,
+  isCsv,
+  isNotebook,
+  mdViewMode,
+  isChangesMode,
+  sideBySide,
+  showMarkdownTableOfContents,
+  showMarkdownFrontmatter,
+  onCloseMarkdownTableOfContents,
+  markdownAnnotationsEnabled,
+  pendingEditorReveal,
+  markdownDocuments,
+  getConflictNavigation,
+  getMarkdownSourceLineOffset,
+  handleContentChange,
+  handleDirtyStateHint,
+  handleSave,
+  reloadContent
+}: {
+  activeFile: OpenFile
+  viewStateScopeId: string
+  editorViewStateKey: string
+  diffViewStateKey: string
+  pdfViewStateKey: string
+  fileContent: FileContent | undefined
+  diffContent: GitDiffResult | undefined
+  editBuffer: string | undefined
+  activeConflictEntry: GitStatusEntry | null
+  monacoLanguage: string
+  isMarkdown: boolean
+  isMermaid: boolean
+  isCsv: boolean
+  isNotebook: boolean
+  mdViewMode: MarkdownViewMode
+  isChangesMode: boolean
+  sideBySide: boolean
+  showMarkdownTableOfContents: boolean
+  showMarkdownFrontmatter: boolean
+  onCloseMarkdownTableOfContents: () => void
+  markdownAnnotationsEnabled: boolean
+  pendingEditorReveal: PendingEditorReveal | null
+  markdownDocuments: MarkdownDocumentsController
+  getConflictNavigation: (file: OpenFile, content: string) => EditorConflictNavigation | undefined
+  getMarkdownSourceLineOffset: (frontMatterRaw: string) => number
+  handleContentChange: (content: string) => void
+  handleDirtyStateHint: (dirty: boolean) => void
+  handleSave: (content: string) => Promise<boolean>
+  reloadContent: (file: OpenFile) => void
+}): React.JSX.Element {
+  if (activeFile.conflict?.kind === 'conflict-placeholder') {
+    return <ConflictPlaceholderView file={activeFile} />
+  }
+  if (!fileContent) {
+    return (
+      <div className="flex items-center justify-center h-full text-muted-foreground text-sm">
+        {translate('auto.components.editor.EditorContent.b2735221f5', 'Loading...')}
+      </div>
+    )
+  }
+  if (fileContent.loadError) {
+    return (
+      <EditorFileLoadErrorView
+        message={fileContent.loadError}
+        onRetry={() => reloadContent(activeFile)}
+      />
+    )
+  }
+  if (fileContent.isBinary) {
+    if (fileContent.isImage) {
+      return (
+        <ImageViewer
+          content={fileContent.content}
+          filePath={activeFile.filePath}
+          mimeType={fileContent.mimeType}
+          scrollCacheKey={pdfViewStateKey}
+        />
+      )
+    }
+    return (
+      <div className="flex items-center justify-center h-full text-muted-foreground text-sm">
+        {translate(
+          'auto.components.editor.EditorContent.b9de81ba52',
+          'Binary file — cannot display'
+        )}
+      </div>
+    )
+  }
+
+  const currentContent = editBuffer ?? fileContent.content
+  const externalChangeBanner =
+    activeFile.externalMutation === 'changed' ? (
+      <ExternalFileChangeBanner
+        file={activeFile}
+        currentContent={currentContent}
+        reloadContent={reloadContent}
+      />
+    ) : null
+
+  if (isChangesMode) {
+    const changesView = (
+      <ChangesModeView
+        activeFile={activeFile}
+        dc={diffContent}
+        modifiedContent={currentContent}
+        activeConflictEntry={activeConflictEntry}
+        resolvedLanguage={monacoLanguage}
+        sideBySide={sideBySide}
+        viewStateScopeId={viewStateScopeId}
+        diffViewStateKey={diffViewStateKey}
+        onContentChange={handleContentChange}
+        onSave={isMarkdown ? markdownDocuments.mdSave : handleSave}
+      />
+    )
+    if (!externalChangeBanner) {
+      return changesView
+    }
+    return (
+      <div className="flex flex-1 min-h-0 flex-col">
+        {externalChangeBanner}
+        <div className="min-h-0 flex-1">{changesView}</div>
+      </div>
+    )
+  }
+
+  const monacoEditor = (
+    // Why: without a key React reuses the instance and skips cleanup (scroll snapshot); key forces a remount per pane+path.
+    <MonacoEditor
+      key={`${viewStateScopeId}\u0000${activeFile.filePath}`}
+      fileId={activeFile.id}
+      filePath={activeFile.filePath}
+      viewStateKey={editorViewStateKey}
+      viewStateId={viewStateScopeId}
+      relativePath={activeFile.relativePath}
+      content={currentContent}
+      language={monacoLanguage}
+      // Why: read-only tabs no-op the change/save callbacks so no draft, dirty state, or write can occur.
+      readOnly={activeFile.readOnly === true}
+      liveTail={activeFile.liveTail === true}
+      onContentChange={activeFile.readOnly === true ? noopEditorContentChange : handleContentChange}
+      onSave={
+        activeFile.readOnly === true
+          ? noopEditorSave
+          : isMarkdown
+            ? markdownDocuments.mdSave
+            : handleSave
+      }
+      worktreeId={activeFile.worktreeId}
+      markdownAnnotationsEnabled={markdownAnnotationsEnabled && isMarkdown}
+      conflictDecorationsEnabled={activeFile.conflict?.conflictStatus === 'unresolved'}
+      revealLine={
+        matchesPendingEditorReveal(pendingEditorReveal, activeFile)
+          ? pendingEditorReveal.line
+          : undefined
+      }
+      revealColumn={
+        matchesPendingEditorReveal(pendingEditorReveal, activeFile)
+          ? pendingEditorReveal.column
+          : undefined
+      }
+      revealMatchLength={
+        matchesPendingEditorReveal(pendingEditorReveal, activeFile)
+          ? pendingEditorReveal.matchLength
+          : undefined
+      }
+      markdownDocuments={isMarkdown ? markdownDocuments.markdownDocuments : undefined}
+    />
+  )
+
+  const editorSurface = isMarkdown ? (
+    <EditorMarkdownFileSurface
+      activeFile={activeFile}
+      viewStateScopeId={viewStateScopeId}
+      editorViewStateKey={editorViewStateKey}
+      currentContent={currentContent}
+      mdViewMode={mdViewMode}
+      showMarkdownTableOfContents={showMarkdownTableOfContents}
+      showMarkdownFrontmatter={showMarkdownFrontmatter}
+      onCloseMarkdownTableOfContents={onCloseMarkdownTableOfContents}
+      markdownAnnotationsEnabled={markdownAnnotationsEnabled}
+      markdownDocuments={markdownDocuments}
+      getMarkdownSourceLineOffset={getMarkdownSourceLineOffset}
+      handleContentChange={handleContentChange}
+      handleDirtyStateHint={handleDirtyStateHint}
+      monacoEditor={monacoEditor}
+    />
+  ) : isMermaid && mdViewMode === 'rich' ? (
+    <MermaidViewer key={activeFile.id} content={currentContent} filePath={activeFile.filePath} />
+  ) : isCsv && mdViewMode === 'rich' ? (
+    <CsvViewer key={activeFile.id} content={currentContent} filePath={activeFile.filePath} />
+  ) : isNotebook && mdViewMode === 'rich' ? (
+    <IpynbViewer
+      key={activeFile.id}
+      content={currentContent}
+      fileId={activeFile.id}
+      filePath={activeFile.filePath}
+      worktreeId={activeFile.worktreeId}
+      scrollCacheKey={`${editorViewStateKey}:notebook`}
+      onContentChange={handleContentChange}
+      onDirtyStateHint={handleDirtyStateHint}
+      onSave={handleSave}
+    />
+  ) : (
+    monacoEditor
+  )
+
+  return (
+    <div className="flex flex-1 min-h-0 flex-col">
+      {externalChangeBanner}
+      {activeFile.conflict && (
+        <ConflictBanner
+          file={activeFile}
+          entry={activeConflictEntry}
+          conflictNavigation={getConflictNavigation(activeFile, currentContent)}
+        />
+      )}
+      <div className="min-h-0 flex-1 relative">{editorSurface}</div>
+    </div>
+  )
+}
+
+function matchesPendingEditorReveal(
+  reveal: PendingEditorReveal | null,
+  file: Pick<OpenFile, 'id' | 'filePath'>
+): reveal is PendingEditorReveal {
+  if (!reveal) {
+    return false
+  }
+  return reveal.fileId ? reveal.fileId === file.id : reveal.filePath === file.filePath
+}
diff --git a/src/renderer/src/components/editor/EditorFileLoadErrorView.tsx b/src/renderer/src/components/editor/EditorFileLoadErrorView.tsx
new file mode 100644
index 00000000000..41964fbd444
--- /dev/null
+++ b/src/renderer/src/components/editor/EditorFileLoadErrorView.tsx
@@ -0,0 +1,29 @@
+import { AlertCircle, RefreshCw } from 'lucide-react'
+import { Button } from '@/components/ui/button'
+import { translate } from '@/i18n/i18n'
+
+export function EditorFileLoadErrorView({
+  message,
+  onRetry
+}: {
+  message: string
+  onRetry: () => void
+}): React.JSX.Element {
+  return (
+    <div className="flex h-full items-center justify-center bg-editor-surface p-6 text-sm text-muted-foreground">
+      <div className="flex max-w-xl items-start gap-3 rounded-md border border-border bg-background p-4">
+        <AlertCircle className="mt-0.5 size-4 flex-shrink-0 text-destructive" />
+        <div className="min-w-0">
+          <div className="font-medium text-foreground">
+            {translate('auto.components.editor.EditorContent.39f018b052', 'Unable to load file')}
+          </div>
+          <div className="mt-1 break-words">{message}</div>
+          <Button type="button" variant="outline" size="sm" className="mt-3" onClick={onRetry}>
+            <RefreshCw className="size-3.5" />
+            {translate('auto.components.editor.EditorContent.2a512bb46a', 'Retry')}
+          </Button>
+        </div>
+      </div>
+    </div>
+  )
+}
diff --git a/src/renderer/src/components/editor/EditorMarkdownFileSurface.tsx b/src/renderer/src/components/editor/EditorMarkdownFileSurface.tsx
new file mode 100644
index 00000000000..1d0500f58cb
--- /dev/null
+++ b/src/renderer/src/components/editor/EditorMarkdownFileSurface.tsx
@@ -0,0 +1,167 @@
+import { translate } from '@/i18n/i18n'
+import type { MarkdownViewMode, OpenFile } from '@/store/slices/editor'
+import { MarkdownPreview, RichMarkdownEditor } from './editor-lazy-views'
+import { exceedsMarkdownRichModeSizeLimit } from './markdown-rich-size-limit'
+import { extractFrontMatter, prependFrontMatter } from './markdown-frontmatter'
+import { getMarkdownRenderMode } from './markdown-render-mode'
+import { getMarkdownRichModeUnsupportedMessage } from './markdown-rich-mode'
+import { RichMarkdownErrorBoundary } from './RichMarkdownErrorBoundary'
+import type { useMarkdownDocuments } from './useMarkdownDocuments'
+
+type MarkdownDocumentsController = ReturnType<typeof useMarkdownDocuments>
+
+export function EditorMarkdownFileSurface({
+  activeFile,
+  viewStateScopeId,
+  editorViewStateKey,
+  currentContent,
+  mdViewMode,
+  showMarkdownTableOfContents,
+  showMarkdownFrontmatter,
+  onCloseMarkdownTableOfContents,
+  markdownAnnotationsEnabled,
+  markdownDocuments,
+  getMarkdownSourceLineOffset,
+  handleContentChange,
+  handleDirtyStateHint,
+  monacoEditor
+}: {
+  activeFile: OpenFile
+  viewStateScopeId: string
+  editorViewStateKey: string
+  currentContent: string
+  mdViewMode: MarkdownViewMode
+  showMarkdownTableOfContents: boolean
+  showMarkdownFrontmatter: boolean
+  onCloseMarkdownTableOfContents: () => void
+  markdownAnnotationsEnabled: boolean
+  markdownDocuments: MarkdownDocumentsController
+  getMarkdownSourceLineOffset: (frontMatterRaw: string) => number
+  handleContentChange: (content: string) => void
+  handleDirtyStateHint: (dirty: boolean) => void
+  monacoEditor: React.JSX.Element
+}): React.JSX.Element {
+  const richModeUnsupportedMessage = getMarkdownRichModeUnsupportedMessage(currentContent)
+  const renderMode = getMarkdownRenderMode({
+    exceedsRichModeSizeLimit: exceedsMarkdownRichModeSizeLimit(currentContent),
+    hasRichModeUnsupportedContent: richModeUnsupportedMessage !== null,
+    viewMode: mdViewMode
+  })
+
+  if (activeFile.conflict?.conflictStatus === 'unresolved') {
+    return <div className="h-full min-h-0">{monacoEditor}</div>
+  }
+  if (renderMode === 'source' && mdViewMode === 'rich') {
+    const richFallbackMessage =
+      richModeUnsupportedMessage ??
+      'File is too large for rich editing. Showing source mode instead.'
+    return (
+      <div className="flex h-full min-h-0 flex-col">
+        <div className="border-b border-border/60 bg-blue-500/10 px-3 py-2 text-xs text-blue-950 dark:text-blue-100">
+          {richFallbackMessage}
+        </div>
+        <div className="min-h-0 flex-1 h-full">{monacoEditor}</div>
+      </div>
+    )
+  }
+  if (renderMode === 'rich-editor') {
+    const frontMatter = extractFrontMatter(currentContent)
+    const editorContent = frontMatter ? frontMatter.body : currentContent
+    const onContentChange = frontMatter
+      ? (body: string): void => handleContentChange(prependFrontMatter(frontMatter.raw, body))
+      : handleContentChange
+    const onSave = frontMatter
+      ? (body: string): Promise<boolean> =>
+          markdownDocuments.mdSave(prependFrontMatter(frontMatter.raw, body))
+      : markdownDocuments.mdSave
+
+    return (
+      <div className="flex h-full min-h-0 flex-col">
+        <div className="min-h-0 flex-1">
+          {/* Why: keyed for remount like MonacoEditor; boundary contains a TipTap render crash (issue #826) to this pane. */}
+          <RichMarkdownErrorBoundary key={viewStateScopeId} fileId={activeFile.id}>
+            <RichMarkdownEditor
+              fileId={activeFile.id}
+              viewStateId={viewStateScopeId}
+              content={editorContent}
+              filePath={activeFile.filePath}
+              worktreeId={activeFile.worktreeId}
+              externalSshTargetId={activeFile.externalSshTargetId}
+              runtimeEnvironmentId={activeFile.runtimeEnvironmentId}
+              scrollCacheKey={`${editorViewStateKey}:rich`}
+              onContentChange={onContentChange}
+              onDirtyStateHint={handleDirtyStateHint}
+              onSave={onSave}
+              onOpenDocLink={markdownDocuments.onOpenDocLink}
+              markdownDocuments={markdownDocuments.markdownDocuments}
+              showTableOfContents={showMarkdownTableOfContents}
+              onCloseTableOfContents={onCloseMarkdownTableOfContents}
+              markdownAnnotationsEnabled={markdownAnnotationsEnabled}
+              markdownAnnotationFilePath={activeFile.relativePath}
+              markdownSourceLineOffset={
+                frontMatter ? getMarkdownSourceLineOffset(frontMatter.raw) : 0
+              }
+              markdownReviewContent={currentContent}
+              // Why: banner goes below the toolbar (inside the editor shell) so formatting controls stay at the top of the pane.
+              headerSlot={
+                frontMatter && showMarkdownFrontmatter ? (
+                  <FrontMatterBanner raw={frontMatter.raw} />
+                ) : null
+              }
+            />
+          </RichMarkdownErrorBoundary>
+        </div>
+      </div>
+    )
+  }
+  if (renderMode === 'preview') {
+    const shouldExplainRichFallback = mdViewMode === 'rich' && richModeUnsupportedMessage
+    return (
+      <div className="flex h-full min-h-0 flex-col">
+        {shouldExplainRichFallback ? (
+          <div className="border-b border-border/60 bg-amber-500/10 px-3 py-2 text-xs text-amber-950 dark:text-amber-100">
+            {richModeUnsupportedMessage}
+          </div>
+        ) : null}
+        {/* Why: fall back to the stable preview renderer when Tiptap can't safely own the document. */}
+        <div className="min-h-0 flex-1">
+          <MarkdownPreview
+            key={viewStateScopeId}
+            content={currentContent}
+            filePath={activeFile.filePath}
+            sourceFileId={activeFile.id}
+            sourceWorktreeId={activeFile.worktreeId}
+            sourceRuntimeEnvironmentId={activeFile.runtimeEnvironmentId}
+            scrollCacheKey={`${editorViewStateKey}:preview`}
+            showTableOfContents={showMarkdownTableOfContents}
+            onCloseTableOfContents={onCloseMarkdownTableOfContents}
+            markdownAnnotationsEnabled={markdownAnnotationsEnabled}
+            {...markdownDocuments.previewProps}
+          />
+        </div>
+      </div>
+    )
+  }
+  return <div className="h-full min-h-0">{monacoEditor}</div>
+}
+
+function FrontMatterBanner({ raw }: { raw: string }): React.JSX.Element {
+  const inner = raw
+    .replace(/^(?:---|\+\+\+)\r?\n/, '')
+    .replace(/\r?\n(?:---|\+\+\+)\r?\n?$/, '')
+    .trim()
+
+  return (
+    <div className="border-b border-border/60 bg-muted/40 px-3 py-2">
+      <div className="mb-1 text-[10px] font-medium uppercase tracking-wider text-muted-foreground">
+        {translate('auto.components.editor.EditorContent.e4b074749d', 'Front Matter')}
+        <span className="ml-2 font-normal normal-case tracking-normal opacity-70">
+          {translate('auto.components.editor.EditorContent.56dba34e1a', '(edit in source mode)')}
+        </span>
+      </div>
+      <pre className="max-h-32 overflow-auto whitespace-pre-wrap text-xs text-muted-foreground font-mono scrollbar-editor">
+        {inner}
+      </pre>
+    </div>
+  )
+}
diff --git a/src/renderer/src/components/editor/IpynbCellEditor.tsx b/src/renderer/src/components/editor/IpynbCellEditor.tsx
new file mode 100644
index 00000000000..77f319f034c
--- /dev/null
+++ b/src/renderer/src/components/editor/IpynbCellEditor.tsx
@@ -0,0 +1,148 @@
+import { memo, useCallback, useEffect, useLayoutEffect, useMemo, useRef } from 'react'
+import Editor, { type OnMount } from '@monaco-editor/react'
+import Markdown from 'react-markdown'
+import rehypeRaw from 'rehype-raw'
+import rehypeSanitize from 'rehype-sanitize'
+import remarkGfm from 'remark-gfm'
+import { monaco } from '@/lib/monaco-setup'
+import { computeEditorFontSize, resolveEditorFontFamily } from '@/lib/editor-font-zoom'
+import { resolveDocumentTheme } from '@/lib/document-theme'
+import { useAppStore } from '@/store'
+import { installEditorSaveShortcut, installMonacoEditorFindShortcut } from './editor-shortcuts'
+import { getIpynbCodeCellEditorHeight, getIpynbCodeCellPreviewLines } from './ipynb-code-cell-lines'
+import type { IpynbCell } from './ipynb-parse'
+import MonacoCodeExcerpt from './MonacoCodeExcerpt'
+
+export function IpynbMarkdownCell({ source }: { source: string }): React.JSX.Element {
+  return (
+    <div className="markdown-preview-body px-4 py-3 text-sm">
+      <Markdown remarkPlugins={[remarkGfm]} rehypePlugins={[rehypeRaw, rehypeSanitize]}>
+        {source || '\u00a0'}
+      </Markdown>
+    </div>
+  )
+}
+
+export function IpynbEditableTextCell({
+  source,
+  onChange
+}: {
+  source: string
+  onChange: (source: string) => void
+}): React.JSX.Element {
+  return (
+    <textarea
+      value={source}
+      onChange={(event) => onChange(event.target.value)}
+      className="block min-h-24 w-full resize-y border-0 bg-background px-4 py-3 text-sm text-foreground outline-none focus:ring-1 focus:ring-ring"
+    />
+  )
+}
+
+function IpynbCodeCellEditor({
+  cell,
+  source,
+  active,
+  onActivate,
+  onDeactivate,
+  onChange,
+  onSaveRequest
+}: {
+  cell: IpynbCell
+  source: string
+  active: boolean
+  onActivate: () => void
+  onDeactivate: () => void
+  onChange: (source: string) => void
+  onSaveRequest: () => Promise<void>
+}): React.JSX.Element {
+  const settings = useAppStore((s) => s.settings)
+  const editorFontZoomLevel = useAppStore((s) => s.editorFontZoomLevel)
+  const onDeactivateRef = useRef(onDeactivate)
+  const onSaveRequestRef = useRef(onSaveRequest)
+  useLayoutEffect(() => {
+    onDeactivateRef.current = onDeactivate
+    onSaveRequestRef.current = onSaveRequest
+  }, [onDeactivate, onSaveRequest])
+  const fontSize = computeEditorFontSize(settings?.terminalFontSize ?? 13, editorFontZoomLevel)
+  const editorHeight = getIpynbCodeCellEditorHeight(source, fontSize)
+  const isDark = resolveDocumentTheme(settings?.theme ?? 'system')
+  const lines = useMemo(() => getIpynbCodeCellPreviewLines(source), [source])
+  const handleMount: OnMount = useCallback((editorInstance, monacoInstance) => {
+    editorInstance.focus()
+    const cleanupSaveShortcut = installEditorSaveShortcut(
+      editorInstance.getContainerDomNode(),
+      () => {
+        void onSaveRequestRef.current()
+      }
+    )
+    const cleanupFindShortcut = installMonacoEditorFindShortcut(editorInstance)
+    const blurSub = editorInstance.onDidBlurEditorWidget(() => {
+      onDeactivateRef.current()
+    })
+    editorInstance.onDidDispose(() => {
+      cleanupSaveShortcut()
+      cleanupFindShortcut()
+      blurSub.dispose()
+    })
+    editorInstance.addCommand(monacoInstance.KeyCode.Escape, () => {
+      onDeactivateRef.current()
+    })
+  }, [])
+
+  useEffect(() => {
+    monaco.editor.setTheme(isDark ? 'vs-dark' : 'vs')
+  }, [isDark])
+
+  if (!active) {
+    return (
+      <div
+        role="button"
+        tabIndex={0}
+        className="block w-full cursor-text bg-editor-surface text-left"
+        onClick={onActivate}
+        onKeyDown={(event) => {
+          if (event.key === 'Enter') {
+            onActivate()
+          }
+        }}
+      >
+        <MonacoCodeExcerpt
+          lines={lines}
+          firstLineNumber={1}
+          highlightedStartLine={-1}
+          highlightedEndLine={-1}
+          language={cell.language}
+        />
+      </div>
+    )
+  }
+
+  return (
+    <div className="bg-editor-surface focus-within:ring-1 focus-within:ring-ring">
+      <Editor
+        height={editorHeight}
+        defaultLanguage={cell.language}
+        language={cell.language}
+        theme={isDark ? 'vs-dark' : 'vs'}
+        value={source}
+        onMount={handleMount}
+        onChange={(value) => onChange(value ?? '')}
+        options={{
+          automaticLayout: true,
+          fontFamily: resolveEditorFontFamily(settings),
+          fontSize,
+          glyphMargin: false,
+          lineNumbersMinChars: 3,
+          minimap: { enabled: false },
+          overviewRulerLanes: 0,
+          renderLineHighlight: 'none',
+          scrollBeyondLastLine: false,
+          wordWrap: 'off'
+        }}
+      />
+    </div>
+  )
+}
+
+export const IpynbCodeCell = memo(IpynbCodeCellEditor)
diff --git a/src/renderer/src/components/editor/IpynbCellOutputs.tsx b/src/renderer/src/components/editor/IpynbCellOutputs.tsx
new file mode 100644
index 00000000000..a51a0f6315e
--- /dev/null
+++ b/src/renderer/src/components/editor/IpynbCellOutputs.tsx
@@ -0,0 +1,121 @@
+import DOMPurify from 'dompurify'
+import { cn } from '@/lib/utils'
+import { translate } from '@/i18n/i18n'
+import { IpynbMarkdownCell } from './IpynbCellEditor'
+import type { IpynbCell, IpynbOutputItem } from './ipynb-parse'
+
+function valueToText(value: unknown): string {
+  if (Array.isArray(value)) {
+    return value.map((item) => String(item ?? '')).join('')
+  }
+  if (typeof value === 'string') {
+    return value
+  }
+  if (value === undefined || value === null) {
+    return ''
+  }
+  return typeof value === 'object' ? JSON.stringify(value, null, 2) : String(value)
+}
+
+function dataUriForImage(item: IpynbOutputItem): string | null {
+  const value = valueToText(item.value).replace(/\s/g, '')
+  if (!value) {
+    return null
+  }
+  if (item.mime === 'image/svg+xml') {
+    return `data:image/svg+xml;charset=utf-8,${encodeURIComponent(valueToText(item.value))}`
+  }
+  return `data:${item.mime};base64,${value}`
+}
+
+function PreformattedOutput({
+  text,
+  error = false
+}: {
+  text: string
+  error?: boolean
+}): React.JSX.Element {
+  return (
+    <pre
+      className={cn(
+        'max-h-[420px] overflow-auto whitespace-pre-wrap px-3 py-2 font-mono text-xs leading-5 scrollbar-editor',
+        error ? 'text-destructive' : 'text-foreground'
+      )}
+    >
+      {text}
+    </pre>
+  )
+}
+
+function OutputItem({ item }: { item: IpynbOutputItem }): React.JSX.Element | null {
+  if (item.mime === 'text/html') {
+    const html = DOMPurify.sanitize(valueToText(item.value), {
+      USE_PROFILES: { html: true, svg: true, svgFilters: true }
+    })
+    return (
+      <iframe
+        title={translate('auto.components.editor.IpynbViewer.66a3f7d330', 'Notebook HTML output')}
+        sandbox=""
+        referrerPolicy="no-referrer"
+        loading="lazy"
+        className="block h-80 w-full border-0 bg-background"
+        srcDoc={html}
+      />
+    )
+  }
+
+  if (item.mime.startsWith('image/')) {
+    const uri = dataUriForImage(item)
+    return uri ? (
+      <div className="flex max-w-full overflow-auto p-3 scrollbar-editor">
+        <img src={uri} alt={item.mime} className="max-h-[520px] max-w-full object-contain" />
+      </div>
+    ) : null
+  }
+
+  if (item.mime === 'application/json' || item.mime.endsWith('+json')) {
+    const text =
+      typeof item.value === 'string' ? item.value : JSON.stringify(item.value ?? null, null, 2)
+    return <PreformattedOutput text={text} />
+  }
+  if (item.mime === 'text/markdown') {
+    return <IpynbMarkdownCell source={valueToText(item.value)} />
+  }
+  if (item.mime.startsWith('text/') || item.mime === 'application/javascript') {
+    return <PreformattedOutput text={valueToText(item.value)} />
+  }
+  return null
+}
+
+export function IpynbCellOutputs({ cell }: { cell: IpynbCell }): React.JSX.Element | null {
+  if (cell.outputs.length === 0) {
+    return null
+  }
+  return (
+    <div className="border-t border-border/50 bg-background">
+      {cell.outputs.map((output, index) => {
+        if (output.kind === 'stream') {
+          return <PreformattedOutput key={index} text={output.text} />
+        }
+        if (output.kind === 'error') {
+          return (
+            <div key={index} className="border-l-2 border-destructive">
+              <PreformattedOutput
+                error
+                text={[output.name, output.message, output.traceback].filter(Boolean).join('\n')}
+              />
+            </div>
+          )
+        }
+        const renderedItems = output.items
+          .map((item, itemIndex) => <OutputItem key={`${item.mime}-${itemIndex}`} item={item} />)
+          .filter(Boolean)
+        return renderedItems.length > 0 ? (
+          <div key={index} className="border-b border-border/40 last:border-b-0">
+            {renderedItems}
+          </div>
+        ) : null
+      })}
+    </div>
+  )
+}
diff --git a/src/renderer/src/components/editor/IpynbCellToolbar.tsx b/src/renderer/src/components/editor/IpynbCellToolbar.tsx
new file mode 100644
index 00000000000..b32a76c2be8
--- /dev/null
+++ b/src/renderer/src/components/editor/IpynbCellToolbar.tsx
@@ -0,0 +1,176 @@
+import type { ReactNode } from 'react'
+import {
+  ArrowDownToLine,
+  ArrowUpToLine,
+  Braces,
+  FileCode2,
+  Loader2,
+  MoveDown,
+  MoveUp,
+  Play,
+  Trash2
+} from 'lucide-react'
+import { Button } from '@/components/ui/button'
+import { ShortcutKeyCombo } from '@/components/ShortcutKeyCombo'
+import { Tooltip, TooltipContent, TooltipTrigger } from '@/components/ui/tooltip'
+import type { ShortcutKeyComboDetails } from '@/hooks/useShortcutLabel'
+import { translate } from '@/i18n/i18n'
+import type { IpynbCell, IpynbCellKind } from './ipynb-parse'
+
+export function IpynbToolbarButton({
+  label,
+  disabled = false,
+  shortcut,
+  onClick,
+  children
+}: {
+  label: string
+  disabled?: boolean
+  shortcut?: ShortcutKeyComboDetails
+  onClick: () => void
+  children: ReactNode
+}): React.JSX.Element {
+  return (
+    <Tooltip>
+      <TooltipTrigger asChild>
+        <Button
+          type="button"
+          variant="ghost"
+          size="icon"
+          className="size-7"
+          aria-label={label}
+          disabled={disabled}
+          onClick={onClick}
+        >
+          {children}
+        </Button>
+      </TooltipTrigger>
+      <TooltipContent>
+        <span className="flex items-center gap-2">
+          <span>{label}</span>
+          {shortcut && shortcut.keys.length > 0 ? (
+            <ShortcutKeyCombo keys={shortcut.keys} doubleTap={shortcut.doubleTap} />
+          ) : null}
+        </span>
+      </TooltipContent>
+    </Tooltip>
+  )
+}
+
+export function IpynbCellToolbar({
+  cell,
+  index,
+  running,
+  canMoveUp,
+  canMoveDown,
+  onRun,
+  onKindChange,
+  onInsertAbove,
+  onInsertBelow,
+  onMoveUp,
+  onMoveDown,
+  onDelete
+}: {
+  cell: IpynbCell
+  index: number
+  running: boolean
+  canMoveUp: boolean
+  canMoveDown: boolean
+  onRun: () => void
+  onKindChange: (kind: IpynbCellKind) => void
+  onInsertAbove: (kind: IpynbCellKind) => void
+  onInsertBelow: (kind: IpynbCellKind) => void
+  onMoveUp: () => void
+  onMoveDown: () => void
+  onDelete: () => void
+}): React.JSX.Element {
+  const Icon = cell.kind === 'code' ? Play : cell.kind === 'markdown' ? FileCode2 : Braces
+  const executionLabel = cell.kind === 'code' ? `In [${cell.executionCount ?? ' '}]:` : cell.kind
+  return (
+    <div className="flex items-center gap-2 border-b border-border/50 bg-muted/20 px-3 py-1.5 text-xs text-muted-foreground">
+      <Icon className="size-3.5" />
+      <span className="font-mono">{executionLabel}</span>
+      <select
+        value={cell.kind}
+        onChange={(event) => onKindChange(event.target.value as IpynbCellKind)}
+        className="h-7 rounded-md border border-input bg-background px-2 text-xs text-foreground"
+      >
+        <option value="code">
+          {translate('auto.components.editor.IpynbViewer.7005960d73', 'Code')}
+        </option>
+        <option value="markdown">
+          {translate('auto.components.editor.IpynbViewer.1833dbbc43', 'Markdown')}
+        </option>
+        <option value="raw">
+          {translate('auto.components.editor.IpynbViewer.3e4cbf15ea', 'Raw')}
+        </option>
+      </select>
+      {cell.kind === 'code' ? (
+        <IpynbToolbarButton
+          label={translate('auto.components.editor.IpynbViewer.859bf9fc21', 'Run cell')}
+          disabled={running}
+          onClick={onRun}
+        >
+          {running ? <Loader2 className="size-3.5 animate-spin" /> : <Play className="size-3.5" />}
+        </IpynbToolbarButton>
+      ) : null}
+      <IpynbToolbarButton
+        label={translate('auto.components.editor.IpynbViewer.fd8ac707bc', 'Move cell up')}
+        disabled={!canMoveUp}
+        onClick={onMoveUp}
+      >
+        <MoveUp className="size-3.5" />
+      </IpynbToolbarButton>
+      <IpynbToolbarButton
+        label={translate('auto.components.editor.IpynbViewer.27e064e2db', 'Move cell down')}
+        disabled={!canMoveDown}
+        onClick={onMoveDown}
+      >
+        <MoveDown className="size-3.5" />
+      </IpynbToolbarButton>
+      <IpynbToolbarButton
+        label={translate('auto.components.editor.IpynbViewer.53b839b8a0', 'Insert code cell above')}
+        onClick={() => onInsertAbove('code')}
+      >
+        <ArrowUpToLine className="size-3.5" />
+      </IpynbToolbarButton>
+      <IpynbToolbarButton
+        label={translate('auto.components.editor.IpynbViewer.b4208cad7e', 'Insert code cell below')}
+        onClick={() => onInsertBelow('code')}
+      >
+        <ArrowDownToLine className="size-3.5" />
+      </IpynbToolbarButton>
+      <IpynbToolbarButton
+        label={translate(
+          'auto.components.editor.IpynbViewer.ffc1ac2699',
+          'Insert markdown cell above'
+        )}
+        onClick={() => onInsertAbove('markdown')}
+      >
+        <span className="relative size-4">
+          <FileCode2 className="absolute left-0.5 top-0.5 size-3" />
+          <MoveUp className="absolute -right-0.5 -top-0.5 size-2.5" />
+        </span>
+      </IpynbToolbarButton>
+      <IpynbToolbarButton
+        label={translate(
+          'auto.components.editor.IpynbViewer.b42f6a9547',
+          'Insert markdown cell below'
+        )}
+        onClick={() => onInsertBelow('markdown')}
+      >
+        <span className="relative size-4">
+          <FileCode2 className="absolute left-0.5 top-0.5 size-3" />
+          <MoveDown className="absolute -bottom-0.5 -right-0.5 size-2.5" />
+        </span>
+      </IpynbToolbarButton>
+      <IpynbToolbarButton
+        label={translate('auto.components.editor.IpynbViewer.781abd6926', 'Delete cell')}
+        onClick={onDelete}
+      >
+        <Trash2 className="size-3.5" />
+      </IpynbToolbarButton>
+      <span className="ml-auto font-mono">#{index + 1}</span>
+    </div>
+  )
+}
diff --git a/src/renderer/src/components/editor/IpynbViewer.tsx b/src/renderer/src/components/editor/IpynbViewer.tsx
index 882715ca4ff..bca7997943b 100644
--- a/src/renderer/src/components/editor/IpynbViewer.tsx
+++ b/src/renderer/src/components/editor/IpynbViewer.tsx
@@ -1,47 +1,7 @@
-/* eslint-disable max-lines -- Why: notebook editing, output rendering, and cell
-controls share one parsed document/update path for this first notebook editor
-slice; splitting before the model stabilizes would make save/run mutations
-harder to audit. */
-/* oxlint-disable react-doctor/no-adjust-state-on-prop-change -- Why: source drafts are reconciled against parsed notebook cells after editor flushes so stale drafts do not overwrite external notebook updates. */
-import React, {
-  useCallback,
-  useEffect,
-  useLayoutEffect,
-  useMemo,
-  useRef,
-  useState,
-  type MutableRefObject
-} from 'react'
-import Editor, { type OnMount } from '@monaco-editor/react'
-import DOMPurify from 'dompurify'
-import Markdown from 'react-markdown'
-import rehypeRaw from 'rehype-raw'
-import rehypeSanitize from 'rehype-sanitize'
-import remarkGfm from 'remark-gfm'
-import {
-  AlertCircle,
-  ArrowDownToLine,
-  ArrowUpToLine,
-  Braces,
-  FileCode2,
-  Loader2,
-  MoveDown,
-  MoveUp,
-  Play,
-  Save,
-  Trash2
-} from 'lucide-react'
-import { monaco } from '@/lib/monaco-setup'
-import {
-  computeEditorFontSize,
-  resolveEditorFontFamily,
-  resolveEditorFontFamilyOrInherit
-} from '@/lib/editor-font-zoom'
-import { getConnectionId } from '@/lib/connection-context'
-import { resolveDocumentTheme } from '@/lib/document-theme'
+import { useCallback, useMemo, useState } from 'react'
+import { AlertCircle, Save } from 'lucide-react'
+import { computeEditorFontSize, resolveEditorFontFamilyOrInherit } from '@/lib/editor-font-zoom'
 import { useAppStore } from '@/store'
-import { scrollTopCache, setWithLRU } from '@/lib/scroll-cache'
-import { cn } from '@/lib/utils'
 import { Button } from '@/components/ui/button'
 import {
   Dialog,
@@ -51,27 +11,20 @@ import {
   DialogHeader,
   DialogTitle
 } from '@/components/ui/dialog'
-import { Tooltip, TooltipContent, TooltipTrigger } from '@/components/ui/tooltip'
-import { ShortcutKeyCombo } from '@/components/ShortcutKeyCombo'
-import { useShortcutKeyDetails, type ShortcutKeyComboDetails } from '@/hooks/useShortcutLabel'
-import { registerPendingEditorFlush } from './editor-pending-flush'
-import {
-  editorShortcutMatches,
-  installEditorSaveShortcut,
-  installMonacoEditorFindShortcut
-} from './editor-shortcuts'
-import { getIpynbCodeCellEditorHeight, getIpynbCodeCellPreviewLines } from './ipynb-code-cell-lines'
-import MonacoCodeExcerpt from './MonacoCodeExcerpt'
-import {
-  deleteIpynbCell,
-  insertIpynbCell,
-  moveIpynbCell,
-  updateIpynbCellKind,
-  updateIpynbCellOutputs,
-  updateIpynbCellSources
-} from './ipynb-cell-mutations'
-import { parseIpynb, type IpynbCell, type IpynbCellKind, type IpynbOutputItem } from './ipynb-parse'
+import { useShortcutKeyDetails } from '@/hooks/useShortcutLabel'
 import { translate } from '@/i18n/i18n'
+import { editorShortcutMatches } from './editor-shortcuts'
+import { IpynbCellToolbar, IpynbToolbarButton } from './IpynbCellToolbar'
+import { IpynbCodeCell, IpynbEditableTextCell, IpynbMarkdownCell } from './IpynbCellEditor'
+import { IpynbCellOutputs } from './IpynbCellOutputs'
+import { parseIpynb } from './ipynb-parse'
+import {
+  getIpynbCellKey,
+  hasIpynbSourceDraft,
+  useIpynbDocumentEditing
+} from './useIpynbDocumentEditing'
+import { useIpynbCellExecution } from './useIpynbCellExecution'
+import { useIpynbScrollRestoration } from './useIpynbScrollRestoration'
 
 type IpynbViewerProps = {
   content: string
@@ -84,475 +37,6 @@ type IpynbViewerProps = {
   onSave: (content: string) => Promise<boolean>
 }
 
-const NOTEBOOK_SOURCE_COMMIT_DELAY_MS = 400
-
-function cancelIpynbStructuralContentFrames(frameIds: MutableRefObject<number[]>): void {
-  for (const frameId of frameIds.current) {
-    cancelAnimationFrame(frameId)
-  }
-  frameIds.current = []
-}
-
-function requestIpynbStructuralContentFrame(
-  frameIds: MutableRefObject<number[]>,
-  callback: FrameRequestCallback
-): void {
-  let completed = false
-  let frameId: number | undefined
-  frameId = requestAnimationFrame((timestamp) => {
-    completed = true
-    if (frameId !== undefined) {
-      frameIds.current = frameIds.current.filter((pendingFrameId) => pendingFrameId !== frameId)
-    }
-    callback(timestamp)
-  })
-  if (!completed) {
-    frameIds.current.push(frameId)
-  }
-}
-
-type NotebookExecutionTrustState = {
-  filePath: string
-  trustedForFile: boolean
-  pendingRunCellIndex: number | null
-}
-
-function createNotebookExecutionTrustState(filePath: string): NotebookExecutionTrustState {
-  return {
-    filePath,
-    trustedForFile: false,
-    pendingRunCellIndex: null
-  }
-}
-
-function valueToText(value: unknown): string {
-  if (Array.isArray(value)) {
-    return value.map((item) => String(item ?? '')).join('')
-  }
-  if (typeof value === 'string') {
-    return value
-  }
-  if (value === undefined || value === null) {
-    return ''
-  }
-  return typeof value === 'object' ? JSON.stringify(value, null, 2) : String(value)
-}
-
-function dataUriForImage(item: IpynbOutputItem): string | null {
-  const value = valueToText(item.value).replace(/\s/g, '')
-  if (!value) {
-    return null
-  }
-  if (item.mime === 'image/svg+xml') {
-    return `data:image/svg+xml;charset=utf-8,${encodeURIComponent(valueToText(item.value))}`
-  }
-  return `data:${item.mime};base64,${value}`
-}
-
-function NotebookCellHeader({
-  cell,
-  index,
-  running,
-  canMoveUp,
-  canMoveDown,
-  onRun,
-  onKindChange,
-  onInsertAbove,
-  onInsertBelow,
-  onMoveUp,
-  onMoveDown,
-  onDelete
-}: {
-  cell: IpynbCell
-  index: number
-  running: boolean
-  canMoveUp: boolean
-  canMoveDown: boolean
-  onRun: () => void
-  onKindChange: (kind: IpynbCellKind) => void
-  onInsertAbove: (kind: IpynbCellKind) => void
-  onInsertBelow: (kind: IpynbCellKind) => void
-  onMoveUp: () => void
-  onMoveDown: () => void
-  onDelete: () => void
-}): React.JSX.Element {
-  const Icon = cell.kind === 'code' ? Play : cell.kind === 'markdown' ? FileCode2 : Braces
-  const executionLabel = cell.kind === 'code' ? `In [${cell.executionCount ?? ' '}]:` : cell.kind
-  return (
-    <div className="flex items-center gap-2 border-b border-border/50 bg-muted/20 px-3 py-1.5 text-xs text-muted-foreground">
-      <Icon className="size-3.5" />
-      <span className="font-mono">{executionLabel}</span>
-      <select
-        value={cell.kind}
-        onChange={(event) => onKindChange(event.target.value as IpynbCellKind)}
-        className="h-7 rounded-md border border-input bg-background px-2 text-xs text-foreground"
-      >
-        <option value="code">
-          {translate('auto.components.editor.IpynbViewer.7005960d73', 'Code')}
-        </option>
-        <option value="markdown">
-          {translate('auto.components.editor.IpynbViewer.1833dbbc43', 'Markdown')}
-        </option>
-        <option value="raw">
-          {translate('auto.components.editor.IpynbViewer.3e4cbf15ea', 'Raw')}
-        </option>
-      </select>
-      {cell.kind === 'code' ? (
-        <NotebookHeaderButton
-          label={translate('auto.components.editor.IpynbViewer.859bf9fc21', 'Run cell')}
-          disabled={running}
-          onClick={onRun}
-        >
-          {running ? <Loader2 className="size-3.5 animate-spin" /> : <Play className="size-3.5" />}
-        </NotebookHeaderButton>
-      ) : null}
-      <NotebookHeaderButton
-        label={translate('auto.components.editor.IpynbViewer.fd8ac707bc', 'Move cell up')}
-        disabled={!canMoveUp}
-        onClick={onMoveUp}
-      >
-        <MoveUp className="size-3.5" />
-      </NotebookHeaderButton>
-      <NotebookHeaderButton
-        label={translate('auto.components.editor.IpynbViewer.27e064e2db', 'Move cell down')}
-        disabled={!canMoveDown}
-        onClick={onMoveDown}
-      >
-        <MoveDown className="size-3.5" />
-      </NotebookHeaderButton>
-      <NotebookHeaderButton
-        label={translate('auto.components.editor.IpynbViewer.53b839b8a0', 'Insert code cell above')}
-        onClick={() => onInsertAbove('code')}
-      >
-        <ArrowUpToLine className="size-3.5" />
-      </NotebookHeaderButton>
-      <NotebookHeaderButton
-        label={translate('auto.components.editor.IpynbViewer.b4208cad7e', 'Insert code cell below')}
-        onClick={() => onInsertBelow('code')}
-      >
-        <ArrowDownToLine className="size-3.5" />
-      </NotebookHeaderButton>
-      <NotebookHeaderButton
-        label={translate(
-          'auto.components.editor.IpynbViewer.ffc1ac2699',
-          'Insert markdown cell above'
-        )}
-        onClick={() => onInsertAbove('markdown')}
-      >
-        <span className="relative size-4">
-          <FileCode2 className="absolute left-0.5 top-0.5 size-3" />
-          <MoveUp className="absolute -right-0.5 -top-0.5 size-2.5" />
-        </span>
-      </NotebookHeaderButton>
-      <NotebookHeaderButton
-        label={translate(
-          'auto.components.editor.IpynbViewer.b42f6a9547',
-          'Insert markdown cell below'
-        )}
-        onClick={() => onInsertBelow('markdown')}
-      >
-        <span className="relative size-4">
-          <FileCode2 className="absolute left-0.5 top-0.5 size-3" />
-          <MoveDown className="absolute -bottom-0.5 -right-0.5 size-2.5" />
-        </span>
-      </NotebookHeaderButton>
-      <NotebookHeaderButton
-        label={translate('auto.components.editor.IpynbViewer.781abd6926', 'Delete cell')}
-        onClick={onDelete}
-      >
-        <Trash2 className="size-3.5" />
-      </NotebookHeaderButton>
-      <span className="ml-auto font-mono">#{index + 1}</span>
-    </div>
-  )
-}
-
-function NotebookHeaderButton({
-  label,
-  disabled = false,
-  shortcut,
-  onClick,
-  children
-}: {
-  label: string
-  disabled?: boolean
-  shortcut?: ShortcutKeyComboDetails
-  onClick: () => void
-  children: React.ReactNode
-}): React.JSX.Element {
-  return (
-    <Tooltip>
-      <TooltipTrigger asChild>
-        <Button
-          type="button"
-          variant="ghost"
-          size="icon"
-          className="size-7"
-          aria-label={label}
-          disabled={disabled}
-          onClick={onClick}
-        >
-          {children}
-        </Button>
-      </TooltipTrigger>
-      <TooltipContent>
-        <span className="flex items-center gap-2">
-          <span>{label}</span>
-          {shortcut && shortcut.keys.length > 0 ? (
-            <ShortcutKeyCombo keys={shortcut.keys} doubleTap={shortcut.doubleTap} />
-          ) : null}
-        </span>
-      </TooltipContent>
-    </Tooltip>
-  )
-}
-
-function MarkdownCell({ source }: { source: string }): React.JSX.Element {
-  return (
-    <div className="markdown-preview-body px-4 py-3 text-sm">
-      <Markdown remarkPlugins={[remarkGfm]} rehypePlugins={[rehypeRaw, rehypeSanitize]}>
-        {source || '\u00a0'}
-      </Markdown>
-    </div>
-  )
-}
-
-function CodeCell({
-  cell,
-  source,
-  active,
-  onActivate,
-  onDeactivate,
-  onChange,
-  onSaveRequest
-}: {
-  cell: IpynbCell
-  source: string
-  active: boolean
-  onActivate: () => void
-  onDeactivate: () => void
-  onChange: (source: string) => void
-  onSaveRequest: () => Promise<void>
-}): React.JSX.Element {
-  const settings = useAppStore((s) => s.settings)
-  const editorFontZoomLevel = useAppStore((s) => s.editorFontZoomLevel)
-  const onDeactivateRef = useRef(onDeactivate)
-  const onSaveRequestRef = useRef(onSaveRequest)
-  // Why: Monaco commands/listeners are installed once on mount and need the
-  // latest callbacks without rebuilding the embedded editor.
-  onDeactivateRef.current = onDeactivate
-  onSaveRequestRef.current = onSaveRequest
-  const fontSize = computeEditorFontSize(settings?.terminalFontSize ?? 13, editorFontZoomLevel)
-  const editorHeight = getIpynbCodeCellEditorHeight(source, fontSize)
-  const isDark = resolveDocumentTheme(settings?.theme ?? 'system')
-  const lines = useMemo(() => getIpynbCodeCellPreviewLines(source), [source])
-  const handleMount: OnMount = useCallback((editorInstance, monacoInstance) => {
-    editorInstance.focus()
-    const cleanupSaveShortcut = installEditorSaveShortcut(
-      editorInstance.getContainerDomNode(),
-      () => {
-        void onSaveRequestRef.current()
-      }
-    )
-    const cleanupFindShortcut = installMonacoEditorFindShortcut(editorInstance)
-    const blurSub = editorInstance.onDidBlurEditorWidget(() => {
-      onDeactivateRef.current()
-    })
-    editorInstance.onDidDispose(() => {
-      // Why: the inline source editor owns its shortcut bridges and blur
-      // subscription for the lifetime of this Monaco editor instance.
-      cleanupSaveShortcut()
-      cleanupFindShortcut()
-      blurSub.dispose()
-    })
-    editorInstance.addCommand(monacoInstance.KeyCode.Escape, () => {
-      onDeactivateRef.current()
-    })
-  }, [])
-
-  useEffect(() => {
-    monaco.editor.setTheme(isDark ? 'vs-dark' : 'vs')
-  }, [isDark])
-
-  if (!active) {
-    return (
-      <div
-        role="button"
-        tabIndex={0}
-        className="block w-full cursor-text bg-editor-surface text-left"
-        onClick={onActivate}
-        onKeyDown={(event) => {
-          if (event.key === 'Enter') {
-            onActivate()
-          }
-        }}
-      >
-        <MonacoCodeExcerpt
-          lines={lines}
-          firstLineNumber={1}
-          highlightedStartLine={-1}
-          highlightedEndLine={-1}
-          language={cell.language}
-        />
-      </div>
-    )
-  }
-
-  return (
-    <div className="bg-editor-surface focus-within:ring-1 focus-within:ring-ring">
-      <Editor
-        height={editorHeight}
-        defaultLanguage={cell.language}
-        language={cell.language}
-        theme={isDark ? 'vs-dark' : 'vs'}
-        value={source}
-        onMount={handleMount}
-        onChange={(value) => onChange(value ?? '')}
-        options={{
-          automaticLayout: true,
-          fontFamily: resolveEditorFontFamily(settings),
-          fontSize,
-          glyphMargin: false,
-          lineNumbersMinChars: 3,
-          minimap: { enabled: false },
-          overviewRulerLanes: 0,
-          renderLineHighlight: 'none',
-          scrollBeyondLastLine: false,
-          wordWrap: 'off'
-        }}
-      />
-    </div>
-  )
-}
-
-const MemoizedCodeCell = React.memo(CodeCell)
-
-function getCellKey(cell: IpynbCell, index: number): string {
-  return cell.id ?? `${index}:${cell.kind}`
-}
-
-function hasOwnDraft(drafts: Record<string, string>, key: string): boolean {
-  return Object.hasOwn(drafts, key)
-}
-
-function EditableTextCell({
-  source,
-  onChange
-}: {
-  source: string
-  onChange: (source: string) => void
-}): React.JSX.Element {
-  return (
-    <textarea
-      value={source}
-      onChange={(event) => onChange(event.target.value)}
-      className="block min-h-24 w-full resize-y border-0 bg-background px-4 py-3 text-sm text-foreground outline-none focus:ring-1 focus:ring-ring"
-    />
-  )
-}
-
-function PreformattedOutput({
-  text,
-  error = false
-}: {
-  text: string
-  error?: boolean
-}): React.JSX.Element {
-  return (
-    <pre
-      className={cn(
-        'max-h-[420px] overflow-auto whitespace-pre-wrap px-3 py-2 font-mono text-xs leading-5 scrollbar-editor',
-        error ? 'text-destructive' : 'text-foreground'
-      )}
-    >
-      {text}
-    </pre>
-  )
-}
-
-function OutputItem({ item }: { item: IpynbOutputItem }): React.JSX.Element | null {
-  if (item.mime === 'text/html') {
-    const html = DOMPurify.sanitize(valueToText(item.value), {
-      USE_PROFILES: { html: true, svg: true, svgFilters: true }
-    })
-    return (
-      <iframe
-        title={translate('auto.components.editor.IpynbViewer.66a3f7d330', 'Notebook HTML output')}
-        sandbox=""
-        referrerPolicy="no-referrer"
-        loading="lazy"
-        className="block h-80 w-full border-0 bg-background"
-        srcDoc={html}
-      />
-    )
-  }
-
-  if (item.mime.startsWith('image/')) {
-    const uri = dataUriForImage(item)
-    if (!uri) {
-      return null
-    }
-    return (
-      <div className="flex max-w-full overflow-auto p-3 scrollbar-editor">
-        <img src={uri} alt={item.mime} className="max-h-[520px] max-w-full object-contain" />
-      </div>
-    )
-  }
-
-  if (item.mime === 'application/json' || item.mime.endsWith('+json')) {
-    const text =
-      typeof item.value === 'string' ? item.value : JSON.stringify(item.value ?? null, null, 2)
-    return <PreformattedOutput text={text} />
-  }
-
-  if (item.mime === 'text/markdown') {
-    return <MarkdownCell source={valueToText(item.value)} />
-  }
-
-  if (item.mime.startsWith('text/') || item.mime === 'application/javascript') {
-    return <PreformattedOutput text={valueToText(item.value)} />
-  }
-
-  return null
-}
-
-function CellOutputs({ cell }: { cell: IpynbCell }): React.JSX.Element | null {
-  if (cell.outputs.length === 0) {
-    return null
-  }
-
-  return (
-    <div className="border-t border-border/50 bg-background">
-      {cell.outputs.map((output, index) => {
-        if (output.kind === 'stream') {
-          return <PreformattedOutput key={index} text={output.text} />
-        }
-        if (output.kind === 'error') {
-          return (
-            <div key={index} className="border-l-2 border-destructive">
-              <PreformattedOutput
-                error
-                text={[output.name, output.message, output.traceback].filter(Boolean).join('\n')}
-              />
-            </div>
-          )
-        }
-        const renderedItems = output.items
-          .map((item, itemIndex) => <OutputItem key={`${item.mime}-${itemIndex}`} item={item} />)
-          .filter(Boolean)
-        if (renderedItems.length === 0) {
-          return null
-        }
-        return (
-          <div key={index} className="border-b border-border/40 last:border-b-0">
-            {renderedItems}
-          </div>
-        )
-      })}
-    </div>
-  )
-}
-
 export default function IpynbViewer({
   content,
   fileId,
@@ -563,24 +47,9 @@ export default function IpynbViewer({
   onDirtyStateHint,
   onSave
 }: IpynbViewerProps): React.JSX.Element {
-  const rootRef = useRef<HTMLDivElement>(null)
   const settings = useAppStore((s) => s.settings)
   const editorFontZoomLevel = useAppStore((s) => s.editorFontZoomLevel)
-  const [runningCellIndex, setRunningCellIndex] = useState<number | null>(null)
-  const [runError, setRunError] = useState<string | null>(null)
   const [editingCellKey, setEditingCellKey] = useState<string | null>(null)
-  const [executionTrustState, setExecutionTrustState] = useState(() =>
-    createNotebookExecutionTrustState(filePath)
-  )
-  const [sourceDrafts, setSourceDrafts] = useState<Record<string, string>>({})
-  const sourceDraftsRef = useRef(sourceDrafts)
-  const contentRef = useRef(content)
-  const notebookRef = useRef<ReturnType<typeof parseIpynb> | null>(null)
-  const onContentChangeRef = useRef(onContentChange)
-  const onDirtyStateHintRef = useRef(onDirtyStateHint)
-  const sourceCommitTimerRef = useRef<ReturnType<typeof setTimeout> | null>(null)
-  const structuralContentFrameIdsRef = useRef<number[]>([])
-  const fontSize = computeEditorFontSize(13, editorFontZoomLevel)
   const parsed = useMemo(() => {
     try {
       return { notebook: parseIpynb(content), error: null as string | null }
@@ -591,151 +60,41 @@ export default function IpynbViewer({
       }
     }
   }, [content])
-  contentRef.current = content
-  notebookRef.current = parsed.notebook
-  onContentChangeRef.current = onContentChange
-  onDirtyStateHintRef.current = onDirtyStateHint
-
-  // Why: execution trust belongs to the currently rendered file; resetting
-  // during render avoids a paint with the previous file's trust prompt state.
-  if (executionTrustState.filePath !== filePath) {
-    setExecutionTrustState(createNotebookExecutionTrustState(filePath))
-  }
-  const executionTrustedForFile =
-    executionTrustState.filePath === filePath ? executionTrustState.trustedForFile : false
-  const pendingRunCellIndex =
-    executionTrustState.filePath === filePath ? executionTrustState.pendingRunCellIndex : null
-
-  const setPendingRunCellIndexForFile = (nextPendingRunCellIndex: number | null): void => {
-    setExecutionTrustState((current) => ({
-      filePath,
-      trustedForFile: current.filePath === filePath ? current.trustedForFile : false,
-      pendingRunCellIndex: nextPendingRunCellIndex
-    }))
-  }
-  const trustFileForExecution = (): void => {
-    setExecutionTrustState({
-      filePath,
-      trustedForFile: true,
-      pendingRunCellIndex: null
-    })
-  }
-
-  const materializeSourceDrafts = useCallback((): string => {
-    const notebook = notebookRef.current
-    const drafts = sourceDraftsRef.current
-    if (!notebook || Object.keys(drafts).length === 0) {
-      return contentRef.current
-    }
-    const updates = notebook.cells
-      .map((cell, index) => {
-        const key = getCellKey(cell, index)
-        return hasOwnDraft(drafts, key) ? { index, source: drafts[key] ?? '' } : null
-      })
-      .filter((update): update is { index: number; source: string } => update !== null)
-    return updateIpynbCellSources(contentRef.current, updates)
-  }, [])
-
-  const flushSourceDrafts = useCallback((): string => {
-    if (sourceCommitTimerRef.current !== null) {
-      clearTimeout(sourceCommitTimerRef.current)
-      sourceCommitTimerRef.current = null
-    }
-    const nextContent = materializeSourceDrafts()
-    if (nextContent !== contentRef.current) {
-      contentRef.current = nextContent
-      onContentChangeRef.current(nextContent)
-    }
-    return nextContent
-  }, [materializeSourceDrafts])
-
-  const queueSourceDraftCommit = useCallback((): void => {
-    if (sourceCommitTimerRef.current !== null) {
-      clearTimeout(sourceCommitTimerRef.current)
-    }
-    sourceCommitTimerRef.current = setTimeout(() => {
-      void flushSourceDrafts()
-    }, NOTEBOOK_SOURCE_COMMIT_DELAY_MS)
-  }, [flushSourceDrafts])
-
-  useEffect(() => {
-    return registerPendingEditorFlush(fileId, flushSourceDrafts)
-  }, [fileId, flushSourceDrafts])
-
-  const setRootRef = useCallback(
-    (node: HTMLDivElement | null): void => {
-      rootRef.current = node
-      if (node !== null) {
-        return
-      }
-      // Why: pending source edits and structural mutation frames belong to the
-      // notebook scroll root; clear them when that DOM owner detaches.
-      void flushSourceDrafts()
-      cancelIpynbStructuralContentFrames(structuralContentFrameIdsRef)
-    },
-    [flushSourceDrafts]
-  )
-
-  useEffect(() => {
-    if (!parsed.notebook || Object.keys(sourceDraftsRef.current).length === 0) {
-      return
-    }
-    const nextDrafts = { ...sourceDraftsRef.current }
-    let changed = false
-    parsed.notebook.cells.forEach((cell, index) => {
-      const key = getCellKey(cell, index)
-      if (hasOwnDraft(nextDrafts, key) && nextDrafts[key] === cell.source) {
-        delete nextDrafts[key]
-        changed = true
-      }
-    })
-    if (changed) {
-      sourceDraftsRef.current = nextDrafts
-      setSourceDrafts(nextDrafts)
-    }
-  }, [parsed.notebook])
-
-  useLayoutEffect(() => {
-    const container = rootRef.current
-    if (!container) {
-      return
-    }
-    let throttleTimer: ReturnType<typeof setTimeout> | null = null
-    const onScroll = (): void => {
-      if (throttleTimer !== null) {
-        clearTimeout(throttleTimer)
-      }
-      throttleTimer = setTimeout(() => {
-        setWithLRU(scrollTopCache, scrollCacheKey, container.scrollTop)
-        throttleTimer = null
-      }, 150)
-    }
-    container.addEventListener('scroll', onScroll, { passive: true })
-    return () => {
-      if (container.scrollHeight > container.clientHeight || container.scrollTop > 0) {
-        setWithLRU(scrollTopCache, scrollCacheKey, container.scrollTop)
-      }
-      if (throttleTimer !== null) {
-        clearTimeout(throttleTimer)
-      }
-      container.removeEventListener('scroll', onScroll)
-    }
-  }, [scrollCacheKey])
-
-  useLayoutEffect(() => {
-    const container = rootRef.current
-    const targetScrollTop = scrollTopCache.get(scrollCacheKey)
-    if (!container || targetScrollTop === undefined) {
-      return
-    }
-    container.scrollTop = targetScrollTop
-  }, [scrollCacheKey, content])
+  const deactivateEditor = useCallback((): void => setEditingCellKey(null), [])
+  const {
+    rootRef,
+    setRootRef,
+    sourceDrafts,
+    flushSourceDrafts,
+    applyContent,
+    updateCellSource,
+    updateCellKind,
+    insertCell,
+    moveCell,
+    deleteCell
+  } = useIpynbDocumentEditing({
+    content,
+    fileId,
+    notebook: parsed.notebook,
+    onContentChange,
+    onDirtyStateHint,
+    onDeactivateEditor: deactivateEditor
+  })
+  const execution = useIpynbCellExecution({
+    filePath,
+    worktreeId,
+    flushSourceDrafts,
+    applyContent,
+    onSave
+  })
+  useIpynbScrollRestoration(rootRef, scrollCacheKey, content)
+  const saveShortcut = useShortcutKeyDetails('editor.save')
+  const fontSize = computeEditorFontSize(13, editorFontZoomLevel)
 
   const saveNotebook = useCallback(async (): Promise<void> => {
     const latestContent = flushSourceDrafts()
     await onSave(latestContent)
   }, [flushSourceDrafts, onSave])
-  const saveShortcut = useShortcutKeyDetails('editor.save')
 
   const handleNotebookKeyDownCapture = useCallback(
     (event: React.KeyboardEvent<HTMLDivElement>): void => {
@@ -755,10 +114,9 @@ export default function IpynbViewer({
         return
       }
       const target = event.target instanceof Element ? event.target : null
-      if (target?.closest('.monaco-editor')) {
-        return
+      if (!target?.closest('.monaco-editor')) {
+        setEditingCellKey(null)
       }
-      setEditingCellKey(null)
     },
     [editingCellKey]
   )
@@ -783,97 +141,6 @@ export default function IpynbViewer({
   }
 
   const { notebook } = parsed
-  const applyContent = (nextContent: string): void => {
-    contentRef.current = nextContent
-    onContentChange(nextContent)
-  }
-  const updateCellSource = (index: number, source: string): void => {
-    const cell = notebook.cells[index]
-    if (!cell) {
-      return
-    }
-    const key = getCellKey(cell, index)
-    const nextDrafts = { ...sourceDraftsRef.current, [key]: source }
-    sourceDraftsRef.current = nextDrafts
-    setSourceDrafts(nextDrafts)
-    onDirtyStateHintRef.current(true)
-    queueSourceDraftCommit()
-  }
-  const applyStructuralContentChange = (
-    getNextContent: (latestContent: string) => string
-  ): void => {
-    const latestContent = flushSourceDrafts()
-    // Why: Monaco can still have a render frame queued for the active cell.
-    // Exit edit mode first, then reorder/replace cells on the next frame so
-    // structural notebook actions do not dispose an editor mid-render.
-    setEditingCellKey(null)
-    requestIpynbStructuralContentFrame(structuralContentFrameIdsRef, () => {
-      applyContent(getNextContent(latestContent))
-    })
-  }
-  const updateCellKind = (index: number, kind: IpynbCellKind): void => {
-    applyStructuralContentChange((latestContent) =>
-      updateIpynbCellKind(latestContent, index, kind, notebook.language)
-    )
-  }
-  const insertCell = (index: number, kind: IpynbCellKind): void => {
-    applyStructuralContentChange((latestContent) =>
-      insertIpynbCell(latestContent, index, kind, notebook.language)
-    )
-  }
-  const moveCell = (index: number, direction: -1 | 1): void => {
-    applyStructuralContentChange((latestContent) => moveIpynbCell(latestContent, index, direction))
-  }
-  const deleteCell = (index: number): void => {
-    applyStructuralContentChange((latestContent) => deleteIpynbCell(latestContent, index))
-  }
-  const runCell = async (
-    index: number,
-    options: { skipTrustPrompt?: boolean } = {}
-  ): Promise<void> => {
-    const latestContent = flushSourceDrafts()
-    const latestNotebook = parseIpynb(latestContent)
-    const cell = latestNotebook.cells[index]
-    if (!cell || cell.kind !== 'code' || runningCellIndex !== null) {
-      return
-    }
-    if (!executionTrustedForFile && !options.skipTrustPrompt) {
-      setPendingRunCellIndexForFile(index)
-      return
-    }
-    setRunError(null)
-    setRunningCellIndex(index)
-    try {
-      const didSave = await onSave(latestContent)
-      if (!didSave) {
-        return
-      }
-      const result = await window.api.notebook.runPythonCell({
-        filePath,
-        code: cell.source,
-        preamble: latestNotebook.cells
-          .slice(0, index)
-          .filter((previousCell) => previousCell.kind === 'code')
-          .map((previousCell) => previousCell.source)
-          .join('\n\n'),
-        connectionId: getConnectionId(worktreeId) ?? undefined
-      })
-      applyContent(updateIpynbCellOutputs(latestContent, index, result))
-    } catch (error) {
-      setRunError(error instanceof Error ? error.message : String(error))
-    } finally {
-      setRunningCellIndex(null)
-    }
-  }
-  const cancelPendingRun = (): void => setPendingRunCellIndexForFile(null)
-  const confirmPendingRun = (): void => {
-    const index = pendingRunCellIndex
-    trustFileForExecution()
-    if (index !== null) {
-      void runCell(index, { skipTrustPrompt: true })
-    }
-  }
-
   return (
     <div
       ref={setRootRef}
@@ -890,15 +157,15 @@ export default function IpynbViewer({
         </span>
         <span>{notebook.language}</span>
         {notebook.kernelName ? <span>{notebook.kernelName}</span> : null}
-        {runError ? <span className="text-destructive">{runError}</span> : null}
+        {execution.runError ? <span className="text-destructive">{execution.runError}</span> : null}
         <div className="ml-auto flex items-center gap-2">
-          <NotebookHeaderButton
+          <IpynbToolbarButton
             label={translate('auto.components.editor.IpynbViewer.15ec40a735', 'Save notebook')}
             shortcut={saveShortcut}
             onClick={() => void saveNotebook()}
           >
             <Save className="size-3.5" />
-          </NotebookHeaderButton>
+          </IpynbToolbarButton>
           <span className="rounded-sm border border-border bg-muted px-1.5 py-0.5 font-medium text-muted-foreground">
             {translate('auto.components.editor.IpynbViewer.329764e9fc', 'BETA')}
           </span>
@@ -915,8 +182,8 @@ export default function IpynbViewer({
           </div>
         ) : (
           notebook.cells.map((cell, index) => {
-            const cellKey = getCellKey(cell, index)
-            const source = hasOwnDraft(sourceDrafts, cellKey)
+            const cellKey = getIpynbCellKey(cell, index)
+            const source = hasIpynbSourceDraft(sourceDrafts, cellKey)
               ? (sourceDrafts[cellKey] ?? '')
               : cell.source
             return (
@@ -924,13 +191,13 @@ export default function IpynbViewer({
                 key={cellKey}
                 className="overflow-hidden rounded-md border border-border bg-background"
               >
-                <NotebookCellHeader
+                <IpynbCellToolbar
                   cell={cell}
                   index={index}
-                  running={runningCellIndex === index}
+                  running={execution.runningCellIndex === index}
                   canMoveUp={index > 0}
                   canMoveDown={index < notebook.cells.length - 1}
-                  onRun={() => void runCell(index)}
+                  onRun={() => void execution.runCell(index)}
                   onKindChange={(kind) => updateCellKind(index, kind)}
                   onInsertAbove={(kind) => insertCell(index, kind)}
                   onInsertBelow={(kind) => insertCell(index + 1, kind)}
@@ -940,16 +207,16 @@ export default function IpynbViewer({
                 />
                 {cell.kind === 'markdown' ? (
                   <div className="grid gap-0 lg:grid-cols-2">
-                    <EditableTextCell
+                    <IpynbEditableTextCell
                       source={source}
                       onChange={(nextSource) => updateCellSource(index, nextSource)}
                     />
                     <div className="border-t border-border/50 lg:border-l lg:border-t-0">
-                      <MarkdownCell source={source} />
+                      <IpynbMarkdownCell source={source} />
                     </div>
                   </div>
                 ) : cell.kind === 'code' ? (
-                  <MemoizedCodeCell
+                  <IpynbCodeCell
                     cell={cell}
                     source={source}
                     active={editingCellKey === cellKey}
@@ -961,22 +228,22 @@ export default function IpynbViewer({
                     onSaveRequest={saveNotebook}
                   />
                 ) : (
-                  <EditableTextCell
+                  <IpynbEditableTextCell
                     source={source}
                     onChange={(nextSource) => updateCellSource(index, nextSource)}
                   />
                 )}
-                <CellOutputs cell={cell} />
+                <IpynbCellOutputs cell={cell} />
               </section>
             )
           })
         )}
       </div>
       <Dialog
-        open={pendingRunCellIndex !== null}
+        open={execution.pendingRunCellIndex !== null}
         onOpenChange={(open) => {
           if (!open) {
-            cancelPendingRun()
+            execution.cancelPendingRun()
           }
         }}
       >
@@ -993,10 +260,10 @@ export default function IpynbViewer({
             </DialogDescription>
           </DialogHeader>
           <DialogFooter className="gap-2">
-            <Button type="button" variant="outline" size="sm" onClick={cancelPendingRun}>
+            <Button type="button" variant="outline" size="sm" onClick={execution.cancelPendingRun}>
               {translate('auto.components.editor.IpynbViewer.7f0d7077c6', 'Cancel')}
             </Button>
-            <Button type="button" size="sm" autoFocus onClick={confirmPendingRun}>
+            <Button type="button" size="sm" autoFocus onClick={execution.confirmPendingRun}>
               {translate('auto.components.editor.IpynbViewer.859bf9fc21', 'Run cell')}
             </Button>
           </DialogFooter>
diff --git a/src/renderer/src/components/editor/editor-lazy-views.ts b/src/renderer/src/components/editor/editor-lazy-views.ts
new file mode 100644
index 00000000000..bfdacaba622
--- /dev/null
+++ b/src/renderer/src/components/editor/editor-lazy-views.ts
@@ -0,0 +1,16 @@
+import { lazyWithRetry as lazy } from '@/lib/lazy-with-retry'
+
+// Why: one lazy() identity per viewer, shared by every editor surface — a second lazy() over the
+// same module is a distinct component type, so it gets its own Suspense boundary and remount.
+export const MonacoEditor = lazy(() => import('./MonacoEditor'))
+export const DiffViewer = lazy(() => import('./DiffViewer'))
+export const CombinedDiffViewer = lazy(() => import('./CombinedDiffViewer'))
+export const RichMarkdownEditor = lazy(() => import('./RichMarkdownEditor'), {
+  reloadKey: 'rich-markdown-editor'
+})
+export const MarkdownPreview = lazy(() => import('./MarkdownPreview'))
+export const ImageViewer = lazy(() => import('./ImageViewer'))
+export const ImageDiffViewer = lazy(() => import('./ImageDiffViewer'))
+export const MermaidViewer = lazy(() => import('./MermaidViewer'))
+export const CsvViewer = lazy(() => import('./CsvViewer'))
+export const IpynbViewer = lazy(() => import('./IpynbViewer'))
diff --git a/src/renderer/src/components/editor/useEditorConflictNavigation.ts b/src/renderer/src/components/editor/useEditorConflictNavigation.ts
new file mode 100644
index 00000000000..ccea82fd322
--- /dev/null
+++ b/src/renderer/src/components/editor/useEditorConflictNavigation.ts
@@ -0,0 +1,61 @@
+import { useCallback, useState } from 'react'
+import { useAppStore } from '@/store'
+import type { OpenFile } from '@/store/slices/editor'
+import { getNextConflictNavigationIndex } from './ConflictComponents'
+import {
+  findGitConflictBlocks,
+  getGitConflictMarkerLineLength
+} from './monaco-conflict-decorations'
+
+export type EditorConflictNavigation = {
+  currentIndex: number | null
+  total: number
+  onJump: (direction: 'previous' | 'next') => void
+}
+
+export function useEditorConflictNavigation(): (
+  file: OpenFile,
+  content: string
+) => EditorConflictNavigation | undefined {
+  const setPendingEditorReveal = useAppStore((state) => state.setPendingEditorReveal)
+  const [navigationIndexByFile, setNavigationIndexByFile] = useState<Record<string, number>>({})
+
+  return useCallback(
+    (file: OpenFile, content: string) => {
+      const blocks = findGitConflictBlocks(content)
+      if (blocks.length === 0) {
+        return undefined
+      }
+
+      const currentIndex = navigationIndexByFile[file.id] ?? null
+      return {
+        currentIndex,
+        total: blocks.length,
+        onJump: (direction: 'previous' | 'next') => {
+          const nextIndex = getNextConflictNavigationIndex({
+            currentIndex,
+            direction,
+            total: blocks.length
+          })
+          if (nextIndex === null) {
+            return
+          }
+          const line = blocks[nextIndex].startLine
+          const markerLineLength = getGitConflictMarkerLineLength(content, line)
+          setNavigationIndexByFile((previous) => ({ ...previous, [file.id]: nextIndex }))
+          // Why: clear first so a repeated same-location reveal still changes the prop and re-runs the editor's reveal effect.
+          setPendingEditorReveal(null)
+          queueMicrotask(() => {
+            setPendingEditorReveal({
+              filePath: file.filePath,
+              line,
+              column: 1,
+              matchLength: markerLineLength
+            })
+          })
+        }
+      }
+    },
+    [navigationIndexByFile, setPendingEditorReveal]
+  )
+}
diff --git a/src/renderer/src/components/editor/useIpynbCellExecution.test.tsx b/src/renderer/src/components/editor/useIpynbCellExecution.test.tsx
new file mode 100644
index 00000000000..c3292fc4490
--- /dev/null
+++ b/src/renderer/src/components/editor/useIpynbCellExecution.test.tsx
@@ -0,0 +1,121 @@
+// @vitest-environment happy-dom
+import { act, renderHook, waitFor } from '@testing-library/react'
+import { afterEach, beforeEach, describe, expect, it, vi } from 'vitest'
+import { parseIpynb } from './ipynb-parse'
+
+const { getConnectionIdMock } = vi.hoisted(() => ({
+  getConnectionIdMock: vi.fn(() => 'ssh-connection')
+}))
+
+vi.mock('@/lib/connection-context', () => ({
+  getConnectionId: getConnectionIdMock
+}))
+
+import { useIpynbCellExecution } from './useIpynbCellExecution'
+
+function notebookContent(): string {
+  return JSON.stringify({
+    nbformat: 4,
+    nbformat_minor: 5,
+    metadata: {},
+    cells: [
+      {
+        id: 'setup',
+        cell_type: 'code',
+        metadata: {},
+        execution_count: null,
+        outputs: [],
+        source: ['x = 41']
+      },
+      {
+        id: 'run',
+        cell_type: 'code',
+        metadata: {},
+        execution_count: null,
+        outputs: [],
+        source: ['print(x + 1)']
+      }
+    ]
+  })
+}
+
+describe('notebook cell execution lifecycle', () => {
+  const runPythonCell = vi.fn()
+
+  beforeEach(() => {
+    vi.clearAllMocks()
+    runPythonCell.mockResolvedValue({ stdout: '42\n', stderr: '', exitCode: 0 })
+    Object.defineProperty(window, 'api', {
+      configurable: true,
+      value: { notebook: { runPythonCell } }
+    })
+  })
+
+  afterEach(() => {
+    Reflect.deleteProperty(window, 'api')
+  })
+
+  it('requires file trust, saves first, and routes execution through the connection', async () => {
+    const content = notebookContent()
+    const onSave = vi.fn().mockResolvedValue(true)
+    const applyContent = vi.fn()
+    const { result } = renderHook(() =>
+      useIpynbCellExecution({
+        filePath: '/repo/notebook.ipynb',
+        worktreeId: 'worktree-a',
+        flushSourceDrafts: () => content,
+        applyContent,
+        onSave
+      })
+    )
+
+    await act(() => result.current.runCell(1))
+    expect(result.current.pendingRunCellIndex).toBe(1)
+    expect(onSave).not.toHaveBeenCalled()
+    expect(runPythonCell).not.toHaveBeenCalled()
+
+    act(() => result.current.confirmPendingRun())
+    await waitFor(() => expect(runPythonCell).toHaveBeenCalledOnce())
+    expect(onSave).toHaveBeenCalledWith(content)
+    expect(runPythonCell).toHaveBeenCalledWith({
+      filePath: '/repo/notebook.ipynb',
+      code: 'print(x + 1)',
+      preamble: 'x = 41',
+      connectionId: 'ssh-connection'
+    })
+    await waitFor(() => expect(applyContent).toHaveBeenCalledOnce())
+    expect(
+      parseIpynb(applyContent.mock.calls[0]?.[0] as string).cells[1]?.outputs[0]
+    ).toMatchObject({
+      kind: 'stream',
+      text: '42\n'
+    })
+  })
+
+  it('drops stale trust prompts across file moves and skips execution after a failed save', async () => {
+    const content = notebookContent()
+    const onSave = vi.fn().mockResolvedValue(false)
+    const hook = renderHook(
+      ({ filePath }: { filePath: string }) =>
+        useIpynbCellExecution({
+          filePath,
+          worktreeId: 'worktree-a',
+          flushSourceDrafts: () => content,
+          applyContent: vi.fn(),
+          onSave
+        }),
+      { initialProps: { filePath: '/repo/a.ipynb' } }
+    )
+
+    await act(() => hook.result.current.runCell(1))
+    expect(hook.result.current.pendingRunCellIndex).toBe(1)
+    hook.rerender({ filePath: '/repo/b.ipynb' })
+    expect(hook.result.current.pendingRunCellIndex).toBeNull()
+    hook.rerender({ filePath: '/repo/a.ipynb' })
+    expect(hook.result.current.pendingRunCellIndex).toBeNull()
+
+    await act(() => hook.result.current.runCell(1, { skipTrustPrompt: true }))
+    expect(onSave).toHaveBeenCalledWith(content)
+    expect(runPythonCell).not.toHaveBeenCalled()
+  })
+})
diff --git a/src/renderer/src/components/editor/useIpynbCellExecution.ts b/src/renderer/src/components/editor/useIpynbCellExecution.ts
new file mode 100644
index 00000000000..bda6f499654
--- /dev/null
+++ b/src/renderer/src/components/editor/useIpynbCellExecution.ts
@@ -0,0 +1,105 @@
+import { useLayoutEffect, useRef, useState } from 'react'
+import { getConnectionId } from '@/lib/connection-context'
+import { updateIpynbCellOutputs } from './ipynb-cell-mutations'
+import { parseIpynb } from './ipynb-parse'
+
+type FileExecutionTrust = {
+  filePath: string
+  revision: number
+  trusted: boolean
+}
+
+type PendingCellRun = {
+  fileRevision: number
+  cellIndex: number
+}
+
+type UseIpynbCellExecutionArgs = {
+  filePath: string
+  worktreeId: string
+  flushSourceDrafts: () => string
+  applyContent: (content: string) => void
+  onSave: (content: string) => Promise<boolean>
+}
+
+export function useIpynbCellExecution({
+  filePath,
+  worktreeId,
+  flushSourceDrafts,
+  applyContent,
+  onSave
+}: UseIpynbCellExecutionArgs) {
+  const trustRef = useRef<FileExecutionTrust>({ filePath, revision: 0, trusted: false })
+  const [pendingRun, setPendingRun] = useState<PendingCellRun | null>(null)
+  const [runningCellIndex, setRunningCellIndex] = useState<number | null>(null)
+  const [runError, setRunError] = useState<string | null>(null)
+  const fileRevision =
+    trustRef.current.filePath === filePath
+      ? trustRef.current.revision
+      : trustRef.current.revision + 1
+  useLayoutEffect(() => {
+    if (trustRef.current.filePath !== filePath) {
+      trustRef.current = { filePath, revision: fileRevision, trusted: false }
+    }
+  }, [filePath, fileRevision])
+  const pendingRunCellIndex =
+    pendingRun?.fileRevision === fileRevision ? pendingRun.cellIndex : null
+
+  const runCell = async (
+    index: number,
+    options: { skipTrustPrompt?: boolean } = {}
+  ): Promise<void> => {
+    const latestContent = flushSourceDrafts()
+    const latestNotebook = parseIpynb(latestContent)
+    const cell = latestNotebook.cells[index]
+    if (!cell || cell.kind !== 'code' || runningCellIndex !== null) {
+      return
+    }
+    if (!trustRef.current.trusted && !options.skipTrustPrompt) {
+      setPendingRun({ fileRevision, cellIndex: index })
+      return
+    }
+    setRunError(null)
+    setRunningCellIndex(index)
+    try {
+      const didSave = await onSave(latestContent)
+      if (!didSave) {
+        return
+      }
+      const result = await window.api.notebook.runPythonCell({
+        filePath,
+        code: cell.source,
+        preamble: latestNotebook.cells
+          .slice(0, index)
+          .filter((previousCell) => previousCell.kind === 'code')
+          .map((previousCell) => previousCell.source)
+          .join('\n\n'),
+        connectionId: getConnectionId(worktreeId) ?? undefined
+      })
+      applyContent(updateIpynbCellOutputs(latestContent, index, result))
+    } catch (error) {
+      setRunError(error instanceof Error ? error.message : String(error))
+    } finally {
+      setRunningCellIndex(null)
+    }
+  }
+
+  const cancelPendingRun = (): void => setPendingRun(null)
+  const confirmPendingRun = (): void => {
+    const index = pendingRunCellIndex
+    trustRef.current.trusted = true
+    setPendingRun(null)
+    if (index !== null) {
+      void runCell(index, { skipTrustPrompt: true })
+    }
+  }
+
+  return {
+    runningCellIndex,
+    runError,
+    pendingRunCellIndex,
+    runCell,
+    cancelPendingRun,
+    confirmPendingRun
+  }
+}
diff --git a/src/renderer/src/components/editor/useIpynbDocumentEditing.test.tsx b/src/renderer/src/components/editor/useIpynbDocumentEditing.test.tsx
new file mode 100644
index 00000000000..5b86b978480
--- /dev/null
+++ b/src/renderer/src/components/editor/useIpynbDocumentEditing.test.tsx
@@ -0,0 +1,142 @@
+// @vitest-environment happy-dom
+import { act, renderHook } from '@testing-library/react'
+import { afterEach, beforeEach, describe, expect, it, vi } from 'vitest'
+import { flushPendingEditorChange } from './editor-pending-flush'
+import { parseIpynb } from './ipynb-parse'
+import { useIpynbDocumentEditing } from './useIpynbDocumentEditing'
+
+function notebookContent(firstSource = 'a', secondSource = 'b'): string {
+  return JSON.stringify({
+    nbformat: 4,
+    nbformat_minor: 5,
+    metadata: { language_info: { name: 'python' } },
+    cells: [
+      {
+        id: 'a',
+        cell_type: 'code',
+        metadata: {},
+        execution_count: null,
+        outputs: [],
+        source: [firstSource]
+      },
+      {
+        id: 'b',
+        cell_type: 'code',
+        metadata: {},
+        execution_count: null,
+        outputs: [],
+        source: [secondSource]
+      }
+    ]
+  })
+}
+
+describe('notebook document editing lifecycle', () => {
+  const animationFrames = new Map<number, FrameRequestCallback>()
+  let nextFrameId = 1
+
+  beforeEach(() => {
+    vi.useFakeTimers()
+    animationFrames.clear()
+    nextFrameId = 1
+    vi.stubGlobal(
+      'requestAnimationFrame',
+      vi.fn((callback: FrameRequestCallback) => {
+        const frameId = nextFrameId
+        nextFrameId += 1
+        animationFrames.set(frameId, callback)
+        return frameId
+      })
+    )
+    vi.stubGlobal(
+      'cancelAnimationFrame',
+      vi.fn((frameId: number) => {
+        animationFrames.delete(frameId)
+      })
+    )
+  })
+
+  afterEach(() => {
+    vi.useRealTimers()
+    vi.unstubAllGlobals()
+  })
+
+  it('debounces drafts, flushes the latest source, and releases acknowledged drafts', () => {
+    const onContentChange = vi.fn()
+    const onDirtyStateHint = vi.fn()
+    const onDeactivateEditor = vi.fn()
+    const initialContent = notebookContent()
+    const hook = renderHook(
+      ({ content }: { content: string }) =>
+        useIpynbDocumentEditing({
+          content,
+          fileId: 'notebook-a',
+          notebook: parseIpynb(content),
+          onContentChange,
+          onDirtyStateHint,
+          onDeactivateEditor
+        }),
+      { initialProps: { content: initialContent } }
+    )
+
+    act(() => {
+      hook.result.current.updateCellSource(0, 'first draft')
+      hook.result.current.updateCellSource(0, 'latest draft')
+      vi.advanceTimersByTime(399)
+    })
+    expect(onDirtyStateHint).toHaveBeenCalledTimes(2)
+    expect(onContentChange).not.toHaveBeenCalled()
+
+    act(() => flushPendingEditorChange('notebook-a'))
+    expect(onContentChange).toHaveBeenCalledTimes(1)
+    const committedContent = onContentChange.mock.calls[0]?.[0] as string
+    expect(parseIpynb(committedContent).cells[0]?.source).toBe('latest draft')
+
+    hook.rerender({ content: committedContent })
+    expect(Object.hasOwn(hook.result.current.sourceDrafts, 'a')).toBe(false)
+
+    const externalContent = notebookContent('external source')
+    hook.rerender({ content: externalContent })
+    expect(Object.hasOwn(hook.result.current.sourceDrafts, 'a')).toBe(false)
+  })
+
+  it('flushes drafts before structural work and cancels queued work on detach', () => {
+    const onContentChange = vi.fn()
+    const onDeactivateEditor = vi.fn()
+    const content = notebookContent()
+    const { result } = renderHook(() =>
+      useIpynbDocumentEditing({
+        content,
+        fileId: 'notebook-a',
+        notebook: parseIpynb(content),
+        onContentChange,
+        onDirtyStateHint: vi.fn(),
+        onDeactivateEditor
+      })
+    )
+
+    act(() => {
+      result.current.updateCellSource(0, 'edited before move')
+      result.current.moveCell(0, 1)
+    })
+    expect(onDeactivateEditor).toHaveBeenCalledOnce()
+    expect(onContentChange).toHaveBeenCalledTimes(1)
+    expect(parseIpynb(onContentChange.mock.calls[0]?.[0] as string).cells[0]?.source).toBe(
+      'edited before move'
+    )
+    expect(animationFrames.size).toBe(1)
+
+    const [[frameId, frameCallback]] = [...animationFrames.entries()]
+    animationFrames.delete(frameId)
+    act(() => frameCallback(0))
+    const movedNotebook = parseIpynb(onContentChange.mock.calls[1]?.[0] as string)
+    expect(movedNotebook.cells.map((cell) => cell.id)).toEqual(['b', 'a'])
+    expect(movedNotebook.cells[1]?.source).toBe('edited before move')
+
+    act(() => result.current.deleteCell(0))
+    expect(animationFrames.size).toBe(1)
+    act(() => result.current.setRootRef(null))
+    expect(cancelAnimationFrame).toHaveBeenCalled()
+    expect(animationFrames.size).toBe(0)
+  })
+})
diff --git a/src/renderer/src/components/editor/useIpynbDocumentEditing.ts b/src/renderer/src/components/editor/useIpynbDocumentEditing.ts
new file mode 100644
index 00000000000..b831438edd6
--- /dev/null
+++ b/src/renderer/src/components/editor/useIpynbDocumentEditing.ts
@@ -0,0 +1,221 @@
+import {
+  useCallback,
+  useEffect,
+  useLayoutEffect,
+  useRef,
+  useState,
+  type MutableRefObject
+} from 'react'
+import { registerPendingEditorFlush } from './editor-pending-flush'
+import {
+  deleteIpynbCell,
+  insertIpynbCell,
+  moveIpynbCell,
+  updateIpynbCellKind,
+  updateIpynbCellSources
+} from './ipynb-cell-mutations'
+import type { IpynbCell, IpynbCellKind, ParsedIpynb } from './ipynb-parse'
+
+const NOTEBOOK_SOURCE_COMMIT_DELAY_MS = 400
+
+export function getIpynbCellKey(cell: IpynbCell, index: number): string {
+  return cell.id ?? `${index}:${cell.kind}`
+}
+
+export function hasIpynbSourceDraft(drafts: Record<string, string>, key: string): boolean {
+  return Object.hasOwn(drafts, key)
+}
+
+function cancelStructuralFrames(frameIds: MutableRefObject<number[]>): void {
+  for (const frameId of frameIds.current) {
+    cancelAnimationFrame(frameId)
+  }
+  frameIds.current = []
+}
+
+function requestStructuralFrame(
+  frameIds: MutableRefObject<number[]>,
+  callback: FrameRequestCallback
+): void {
+  let completed = false
+  let frameId: number | undefined
+  frameId = requestAnimationFrame((timestamp) => {
+    completed = true
+    if (frameId !== undefined) {
+      frameIds.current = frameIds.current.filter((pendingFrameId) => pendingFrameId !== frameId)
+    }
+    callback(timestamp)
+  })
+  if (!completed) {
+    frameIds.current.push(frameId)
+  }
+}
+
+type UseIpynbDocumentEditingArgs = {
+  content: string
+  fileId: string
+  notebook: ParsedIpynb | null
+  onContentChange: (content: string) => void
+  onDirtyStateHint: (dirty: boolean) => void
+  onDeactivateEditor: () => void
+}
+
+export function useIpynbDocumentEditing({
+  content,
+  fileId,
+  notebook,
+  onContentChange,
+  onDirtyStateHint,
+  onDeactivateEditor
+}: UseIpynbDocumentEditingArgs) {
+  const rootRef = useRef<HTMLDivElement>(null)
+  const [sourceDrafts, setSourceDrafts] = useState<Record<string, string>>({})
+  const sourceDraftsRef = useRef(sourceDrafts)
+  const contentRef = useRef(content)
+  const notebookRef = useRef(notebook)
+  const onContentChangeRef = useRef(onContentChange)
+  const onDirtyStateHintRef = useRef(onDirtyStateHint)
+  const sourceCommitTimerRef = useRef<ReturnType<typeof setTimeout> | null>(null)
+  const structuralFrameIdsRef = useRef<number[]>([])
+  useLayoutEffect(() => {
+    contentRef.current = content
+    notebookRef.current = notebook
+    onContentChangeRef.current = onContentChange
+    onDirtyStateHintRef.current = onDirtyStateHint
+  }, [content, notebook, onContentChange, onDirtyStateHint])
+
+  const materializeSourceDrafts = useCallback((): string => {
+    const latestNotebook = notebookRef.current
+    const drafts = sourceDraftsRef.current
+    if (!latestNotebook || Object.keys(drafts).length === 0) {
+      return contentRef.current
+    }
+    const updates = latestNotebook.cells
+      .map((cell, index) => {
+        const key = getIpynbCellKey(cell, index)
+        return hasIpynbSourceDraft(drafts, key) ? { index, source: drafts[key] ?? '' } : null
+      })
+      .filter((update): update is { index: number; source: string } => update !== null)
+    return updateIpynbCellSources(contentRef.current, updates)
+  }, [])
+
+  const flushSourceDrafts = useCallback((): string => {
+    if (sourceCommitTimerRef.current !== null) {
+      clearTimeout(sourceCommitTimerRef.current)
+      sourceCommitTimerRef.current = null
+    }
+    const nextContent = materializeSourceDrafts()
+    if (nextContent !== contentRef.current) {
+      contentRef.current = nextContent
+      onContentChangeRef.current(nextContent)
+    }
+    return nextContent
+  }, [materializeSourceDrafts])
+
+  const queueSourceDraftCommit = useCallback((): void => {
+    if (sourceCommitTimerRef.current !== null) {
+      clearTimeout(sourceCommitTimerRef.current)
+    }
+    sourceCommitTimerRef.current = setTimeout(() => {
+      void flushSourceDrafts()
+    }, NOTEBOOK_SOURCE_COMMIT_DELAY_MS)
+  }, [flushSourceDrafts])
+
+  useEffect(
+    () => registerPendingEditorFlush(fileId, flushSourceDrafts),
+    [fileId, flushSourceDrafts]
+  )
+
+  useEffect(() => {
+    if (!notebook || Object.keys(sourceDraftsRef.current).length === 0) {
+      return
+    }
+    const nextDrafts = { ...sourceDraftsRef.current }
+    let changed = false
+    for (const [index, cell] of notebook.cells.entries()) {
+      const key = getIpynbCellKey(cell, index)
+      if (hasIpynbSourceDraft(nextDrafts, key) && nextDrafts[key] === cell.source) {
+        delete nextDrafts[key]
+        changed = true
+      }
+    }
+    if (changed) {
+      sourceDraftsRef.current = nextDrafts
+      setSourceDrafts(nextDrafts)
+    }
+  }, [notebook])
+
+  const setRootRef = useCallback(
+    (node: HTMLDivElement | null): void => {
+      rootRef.current = node
+      if (node !== null) {
+        return
+      }
+      void flushSourceDrafts()
+      cancelStructuralFrames(structuralFrameIdsRef)
+    },
+    [flushSourceDrafts]
+  )
+
+  const applyContent = useCallback((nextContent: string): void => {
+    contentRef.current = nextContent
+    onContentChangeRef.current(nextContent)
+  }, [])
+
+  const updateCellSource = useCallback(
+    (index: number, source: string): void => {
+      const cell = notebookRef.current?.cells[index]
+      if (!cell) {
+        return
+      }
+      const key = getIpynbCellKey(cell, index)
+      const nextDrafts = { ...sourceDraftsRef.current, [key]: source }
+      sourceDraftsRef.current = nextDrafts
+      setSourceDrafts(nextDrafts)
+      onDirtyStateHintRef.current(true)
+      queueSourceDraftCommit()
+    },
+    [queueSourceDraftCommit]
+  )
+
+  const applyStructuralChange = useCallback(
+    (getNextContent: (latestContent: string) => string): void => {
+      const latestContent = flushSourceDrafts()
+      onDeactivateEditor()
+      requestStructuralFrame(structuralFrameIdsRef, () => {
+        applyContent(getNextContent(latestContent))
+      })
+    },
+    [applyContent, flushSourceDrafts, onDeactivateEditor]
+  )
+
+  const updateCellKind = (index: number, kind: IpynbCellKind): void => {
+    const language = notebookRef.current?.language ?? 'python'
+    applyStructuralChange((latestContent) =>
+      updateIpynbCellKind(latestContent, index, kind, language)
+    )
+  }
+  const insertCell = (index: number, kind: IpynbCellKind): void => {
+    const language = notebookRef.current?.language ?? 'python'
+    applyStructuralChange((latestContent) => insertIpynbCell(latestContent, index, kind, language))
+  }
+  const moveCell = (index: number, direction: -1 | 1): void => {
+    applyStructuralChange((latestContent) => moveIpynbCell(latestContent, index, direction))
+  }
+  const deleteCell = (index: number): void => {
+    applyStructuralChange((latestContent) => deleteIpynbCell(latestContent, index))
+  }
+
+  return {
+    rootRef,
+    setRootRef,
+    sourceDrafts,
+    flushSourceDrafts,
+    applyContent,
+    updateCellSource,
+    updateCellKind,
+    insertCell,
+    moveCell,
+    deleteCell
+  }
+}
diff --git a/src/renderer/src/components/editor/useIpynbScrollRestoration.ts b/src/renderer/src/components/editor/useIpynbScrollRestoration.ts
new file mode 100644
index 00000000000..46d5c489791
--- /dev/null
+++ b/src/renderer/src/components/editor/useIpynbScrollRestoration.ts
@@ -0,0 +1,43 @@
+import { useLayoutEffect, type RefObject } from 'react'
+import { scrollTopCache, setWithLRU } from '@/lib/scroll-cache'
+
+export function useIpynbScrollRestoration(
+  rootRef: RefObject<HTMLDivElement | null>,
+  scrollCacheKey: string,
+  content: string
+): void {
+  useLayoutEffect(() => {
+    const container = rootRef.current
+    if (!container) {
+      return
+    }
+    let throttleTimer: ReturnType<typeof setTimeout> | null = null
+    const onScroll = (): void => {
+      if (throttleTimer !== null) {
+        clearTimeout(throttleTimer)
+      }
+      throttleTimer = setTimeout(() => {
+        setWithLRU(scrollTopCache, scrollCacheKey, container.scrollTop)
+        throttleTimer = null
+      }, 150)
+    }
+    container.addEventListener('scroll', onScroll, { passive: true })
+    return () => {
+      if (container.scrollHeight > container.clientHeight || container.scrollTop > 0) {
+        setWithLRU(scrollTopCache, scrollCacheKey, container.scrollTop)
+      }
+      if (throttleTimer !== null) {
+        clearTimeout(throttleTimer)
+      }
+      container.removeEventListener('scroll', onScroll)
+    }
+  }, [rootRef, scrollCacheKey])
+
+  useLayoutEffect(() => {
+    const container = rootRef.current
+    const targetScrollTop = scrollTopCache.get(scrollCacheKey)
+    if (container && targetScrollTop !== undefined) {
+      container.scrollTop = targetScrollTop
+    }
+  }, [rootRef, scrollCacheKey, content])
+}
diff --git a/src/renderer/src/hooks/editor-external-watch-disk-verification.ts b/src/renderer/src/hooks/editor-external-watch-disk-verification.ts
new file mode 100644
index 00000000000..96caaf8c84a
--- /dev/null
+++ b/src/renderer/src/hooks/editor-external-watch-disk-verification.ts
@@ -0,0 +1,286 @@
+import { useAppStore } from '@/store'
+import type { OpenFile } from '@/store/slices/editor'
+import { joinPath } from '@/lib/path'
+import {
+  getOpenFilesForExternalFileChange,
+  notifyEditorExternalFileChange
+} from '@/components/editor/editor-autosave'
+import { markFileChangedOnDisk } from '@/components/editor/editor-changed-on-disk-mark'
+import { getDiskBaselineSignature } from '@/components/editor/diff-content-signature'
+import {
+  clearSelfWrite,
+  getRecentSelfWrite,
+  type RecentSelfWrite
+} from '@/components/editor/editor-self-write-registry'
+import { readRuntimeFileContent } from '@/runtime/runtime-file-client'
+import type { EditorExternalWatchTarget } from './editor-external-watch-targets'
+
+export type EditorExternalWatchNotification = {
+  worktreeId: string
+  worktreePath: string
+  relativePath: string
+  runtimeEnvironmentId: string | null
+  allowLocalWindowsWslAliases?: true
+  indexedOpenFiles?: {
+    matches: (openFiles: OpenFile[]) => OpenFile[]
+  }
+}
+
+// Why: atomic writes burst same-path events; one reload dispatch each fans out into N EditorPanel rebuilds that can wedge the renderer (issue #826), so debounce per owner+path.
+const EXTERNAL_RELOAD_DEBOUNCE_MS = 75
+const pendingExternalReloadTimers = new Map<string, ReturnType<typeof setTimeout>>()
+
+export function scheduleDebouncedEditorExternalReload(
+  notification: EditorExternalWatchNotification
+): void {
+  const key = `${notification.worktreeId}::${notification.runtimeEnvironmentId ?? 'client'}::${notification.relativePath}`
+  const existing = pendingExternalReloadTimers.get(key)
+  if (existing !== undefined) {
+    globalThis.clearTimeout(existing)
+  }
+  const handle = globalThis.setTimeout(() => {
+    pendingExternalReloadTimers.delete(key)
+    notifyEditorExternalFileChange(notification)
+  }, EXTERNAL_RELOAD_DEBOUNCE_MS)
+  pendingExternalReloadTimers.set(key, handle)
+}
+
+const inFlightEchoVerificationReads = new Map<string, ReturnType<typeof readRuntimeFileContent>>()
+
+// Why: one save echo can arrive as a burst of payloads; share the in-flight full-file read so concurrent payloads for the same file don't stack duplicate reads.
+function readFileForEchoVerification(args: {
+  runtimeEnvironmentId: string | null | undefined
+  filePath: string
+  relativePath: string
+  worktreeId: string | null | undefined
+  connectionId: string | undefined
+  expectedExternalSshTargetId?: string
+}): ReturnType<typeof readRuntimeFileContent> {
+  const key = [
+    args.runtimeEnvironmentId ?? '',
+    args.connectionId ?? '',
+    args.expectedExternalSshTargetId ?? '',
+    args.filePath
+  ].join('::')
+  let pending = inFlightEchoVerificationReads.get(key)
+  if (!pending) {
+    pending = readRuntimeFileContent({
+      settings: args.runtimeEnvironmentId
+        ? { activeRuntimeEnvironmentId: args.runtimeEnvironmentId }
+        : null,
+      filePath: args.filePath,
+      relativePath: args.relativePath,
+      worktreeId: args.worktreeId ?? undefined,
+      connectionId: args.connectionId,
+      expectedExternalSshTargetId: args.expectedExternalSshTargetId
+    })
+    inFlightEchoVerificationReads.set(key, pending)
+    const release = (): void => {
+      if (inFlightEchoVerificationReads.get(key) === pending) {
+        inFlightEchoVerificationReads.delete(key)
+      }
+    }
+    pending.then(release, release)
+  }
+  return pending
+}
+
+function markTabsChangedOnDisk(fileIds: string[], connectionId: string | undefined): void {
+  const state = useAppStore.getState()
+  for (const fileId of fileIds) {
+    const file = state.openFiles.find((candidate) => candidate.id === fileId)
+    // Why: echo verification resolves async — the tab may have been closed since, so only mark files still open.
+    if (file) {
+      markFileChangedOnDisk(state, file, { connectionId, origin: 'live' })
+    }
+  }
+}
+
+export function scheduleEditorChangedOnDiskMark(
+  target: EditorExternalWatchTarget,
+  notification: EditorExternalWatchNotification,
+  fileIds: string[]
+): void {
+  if (fileIds.length === 0) {
+    return
+  }
+  const absolutePath = joinPath(notification.worktreePath, notification.relativePath)
+  const recentSelfWrite = getRecentSelfWrite(absolutePath, target.runtimeEnvironmentId)
+  // Why: the fs event may be the echo of Orca's own save — verify disk really differs from our last write before showing a "changed on disk" banner.
+  if (!recentSelfWrite || recentSelfWrite.content === null) {
+    markTabsChangedOnDisk(fileIds, target.connectionId)
+    return
+  }
+  void readFileForEchoVerification({
+    runtimeEnvironmentId: target.runtimeEnvironmentId,
+    filePath: absolutePath,
+    relativePath: notification.relativePath,
+    worktreeId: notification.worktreeId,
+    connectionId: target.connectionId
+  })
+    .then((result) => {
+      if (result.isBinary || result.content !== recentSelfWrite.content) {
+        markTabsChangedOnDisk(fileIds, target.connectionId)
+      }
+    })
+    .catch(() => {
+      // Why: unreadable disk state can't disprove an external change — keep the conflict visible rather than risk a silent overwrite.
+      markTabsChangedOnDisk(fileIds, target.connectionId)
+    })
+}
+
+// Per-file generation so a newer echo-verify read supersedes an older one — overlapping reads can't clear each other's autosave gate or apply a stale verdict.
+const liveMoveVerifyGeneration = new Map<string, number>()
+let liveMoveVerifyCounter = 0
+
+type LiveMoveVerifyCandidate = {
+  fileId: string
+  baseline: string | undefined
+  generation: number
+  /** The move that installed the provenance; a newer move re-homing the tab supersedes this verification, even across a rekey. */
+  operationId?: string
+}
+
+// Fails closed: anything but a proven baseline match surfaces the conflict, so a real external write is never swallowed.
+function resolveLiveMoveVerification(
+  candidate: LiveMoveVerifyCandidate,
+  diskSignature: string | null,
+  connectionId: string | undefined,
+  consumeProvenance: boolean
+): void {
+  const { fileId, baseline, generation, operationId } = candidate
+  if (liveMoveVerifyGeneration.get(fileId) !== generation) {
+    return
+  }
+  liveMoveVerifyGeneration.delete(fileId)
+  const state = useAppStore.getState()
+  state.setPendingLiveDiskVerification(fileId, false)
+  const file = state.openFiles.find((candidateFile) => candidateFile.id === fileId)
+  if (
+    !file ||
+    !file.isDirty ||
+    file.externalMutation === 'changed' ||
+    file.lastKnownDiskSignature !== baseline ||
+    (operationId !== undefined && file.pendingSelfMoveEcho?.operationId !== operationId)
+  ) {
+    return
+  }
+  // Why: proactive post-commit verification leaves provenance for a later destination watcher event; a watcher-driven check consumes it.
+  if (consumeProvenance) {
+    state.clearSelfMoveEcho(fileId)
+  }
+  const isMoveEcho = baseline !== undefined && diskSignature === baseline
+  if (!isMoveEcho) {
+    markFileChangedOnDisk(state, file, { connectionId, origin: 'live' })
+  }
+}
+
+/** Verifies destination echoes latched before a completed editor path rekey. */
+export function verifyLatchedEditorMoveDestinations(
+  worktreePath: string,
+  connectionId: string | undefined,
+  fileIds: readonly string[]
+): void {
+  const state = useAppStore.getState()
+  const gated = fileIds.filter(
+    (id) => state.openFiles.find((file) => file.id === id)?.pendingSelfMoveEcho
+  )
+  if (gated.length === 0) {
+    return
+  }
+  scheduleEditorSelfMoveEchoVerification(
+    { worktreeId: '', worktreePath, connectionId, runtimeEnvironmentId: null },
+    gated,
+    false
+  )
+}
+
+// Autosave is suspended synchronously first so a write landing mid-read can't be overwritten before verification settles.
+export function scheduleEditorSelfMoveEchoVerification(
+  target: EditorExternalWatchTarget,
+  fileIds: string[],
+  consumeProvenance: boolean
+): void {
+  if (fileIds.length === 0) {
+    return
+  }
+  const state = useAppStore.getState()
+  for (const fileId of fileIds) {
+    const file = state.openFiles.find((candidate) => candidate.id === fileId)
+    if (!file || !file.isDirty || file.externalMutation === 'changed') {
+      continue
+    }
+    const generation = ++liveMoveVerifyCounter
+    liveMoveVerifyGeneration.set(fileId, generation)
+    state.setPendingLiveDiskVerification(fileId, true)
+    const candidate: LiveMoveVerifyCandidate = {
+      fileId,
+      baseline: file.lastKnownDiskSignature,
+      generation,
+      operationId: file.pendingSelfMoveEcho?.operationId
+    }
+    // Why: cross-worktree tabs must read their own absolute path; joining their relative path to the initiating worktree can address the wrong host path.
+    void readFileForEchoVerification({
+      runtimeEnvironmentId: file.runtimeEnvironmentId?.trim() || target.runtimeEnvironmentId,
+      filePath: file.filePath,
+      relativePath: file.relativePath,
+      worktreeId: file.worktreeId,
+      connectionId: target.connectionId,
+      expectedExternalSshTargetId: file.externalSshTargetId
+    })
+      .then((result) => {
+        const diskSignature = result.isBinary ? null : getDiskBaselineSignature(result.content)
+        resolveLiveMoveVerification(
+          candidate,
+          diskSignature,
+          target.connectionId,
+          consumeProvenance
+        )
+      })
+      .catch(() =>
+        resolveLiveMoveVerification(candidate, null, target.connectionId, consumeProvenance)
+      )
+  }
+}
+
+export function scheduleSelfWriteAwareEditorExternalReload(
+  target: EditorExternalWatchTarget,
+  notification: EditorExternalWatchNotification,
+  file: OpenFile,
+  recentSelfWrite: RecentSelfWrite
+): void {
+  if (recentSelfWrite.content === null) {
+    scheduleDebouncedEditorExternalReload(notification)
+    return
+  }
+  const runtimeEnvironmentId = file.runtimeEnvironmentId ?? target.runtimeEnvironmentId
+  // Why: a self-write stamp only proves recent change; compare disk content so it suppresses only Orca's echo, not a newer agent write in the same TTL.
+  void readFileForEchoVerification({
+    runtimeEnvironmentId,
+    filePath: file.filePath,
+    relativePath: file.relativePath,
+    worktreeId: file.worktreeId,
+    connectionId: target.connectionId,
+    expectedExternalSshTargetId: file.externalSshTargetId
+  })
+    .then((result) => {
+      if (
+        (result.isBinary || result.content !== recentSelfWrite.content) &&
+        hasCleanExternalReloadTarget(notification)
+      ) {
+        clearSelfWrite(file.filePath, runtimeEnvironmentId)
+        scheduleDebouncedEditorExternalReload(notification)
+      }
+    })
+    .catch(() => {
+      if (hasCleanExternalReloadTarget(notification)) {
+        clearSelfWrite(file.filePath, runtimeEnvironmentId)
+        scheduleDebouncedEditorExternalReload(notification)
+      }
+    })
+}
+
+function hasCleanExternalReloadTarget(notification: EditorExternalWatchNotification): boolean {
+  const matching = getOpenFilesForExternalFileChange(useAppStore.getState().openFiles, notification)
+  return matching.some((file) => !file.isDirty)
+}
diff --git a/src/renderer/src/hooks/editor-external-watch-event-reconciliation.ts b/src/renderer/src/hooks/editor-external-watch-event-reconciliation.ts
new file mode 100644
index 00000000000..1cb0e3e130b
--- /dev/null
+++ b/src/renderer/src/hooks/editor-external-watch-event-reconciliation.ts
@@ -0,0 +1,300 @@
+import { useAppStore } from '@/store'
+import type { OpenFile } from '@/store/slices/editor'
+import { basename } from '@/lib/path'
+import {
+  canAutoSaveOpenFile,
+  isExternalReloadableEditorTab
+} from '@/components/editor/editor-autosave'
+import { indexEditorExternalWatchBatchPaths } from '@/components/editor/editor-external-watch-path-index'
+import { getRecentSelfWrite } from '@/components/editor/editor-self-write-registry'
+import {
+  hasActiveEditorPathMoves,
+  isActiveMoveSourcePath
+} from '@/components/editor/editor-path-move-inflight'
+import { normalizeRuntimePathForComparison } from '../../../shared/cross-platform-path'
+import type { FsChangedPayload } from '../../../shared/filesystem-entry-types'
+import {
+  ORCA_WORKTREE_FILE_CHANGE_EVENT,
+  type WorktreeFileChangeEventDetail
+} from './worktree-file-change-event'
+import {
+  getLocalWindowsWslAliasOption,
+  getOpenFileRuntimeOwner,
+  type EditorExternalWatchTarget
+} from './editor-external-watch-targets'
+import {
+  scheduleDebouncedEditorExternalReload,
+  scheduleEditorChangedOnDiskMark,
+  scheduleEditorSelfMoveEchoVerification,
+  scheduleSelfWriteAwareEditorExternalReload,
+  type EditorExternalWatchNotification
+} from './editor-external-watch-disk-verification'
+
+// Why: macOS atomic writes split delete→create across payloads; debounce deletion so a same-path create cancels the tombstone before it paints.
+const EXTERNAL_MUTATION_DEBOUNCE_MS = 75
+
+type PendingDeleteTimer = {
+  fileId: string
+  timer: ReturnType<typeof setTimeout>
+}
+
+export function buildEditorExternalWatchEventHandler(
+  findTarget: (
+    worktreePath: string,
+    runtimeEnvironmentId: string | null
+  ) => EditorExternalWatchTarget | undefined
+): {
+  handleFsChanged: (payload: FsChangedPayload, runtimeEnvironmentId?: string | null) => void
+  dispose: () => void
+} {
+  const pendingDeletes = new Map<string, PendingDeleteTimer>()
+  const pendingKey = (
+    worktreeId: string,
+    runtimeEnvironmentId: string | null,
+    absolutePath: string
+  ): string => `${worktreeId}::${runtimeEnvironmentId ?? 'client'}::${absolutePath}`
+
+  const handleFsChanged = (
+    payload: FsChangedPayload,
+    runtimeEnvironmentId: string | null = null
+  ): void => {
+    const target = findTarget(payload.worktreePath, runtimeEnvironmentId)
+    if (!target) {
+      return
+    }
+    // Why: this app-level hook owns watcher subscriptions; other consumers listen here so they don't fight over watch/unwatch ownership.
+    if (typeof window !== 'undefined' && typeof window.dispatchEvent === 'function') {
+      window.dispatchEvent(
+        new CustomEvent<WorktreeFileChangeEventDetail>(ORCA_WORKTREE_FILE_CHANGE_EVENT, {
+          detail: { payload, runtimeEnvironmentId: target.runtimeEnvironmentId }
+        })
+      )
+    }
+
+    // Why: one batch index keeps local WSL alias normalization out of event×tab loops.
+    const openFilesAtStart = useAppStore.getState().openFiles
+    const batchPaths = indexEditorExternalWatchBatchPaths(payload, openFilesAtStart, {
+      worktreeId: target.worktreeId,
+      worktreePath: target.worktreePath,
+      runtimeEnvironmentId: target.runtimeEnvironmentId,
+      ...getLocalWindowsWslAliasOption(target)
+    })
+    const createOrUpdatePaths = batchPaths.createOrUpdatePaths
+    for (const createdPath of createOrUpdatePaths.keys()) {
+      const key = pendingKey(target.worktreeId, target.runtimeEnvironmentId, createdPath)
+      const existing = pendingDeletes.get(key)
+      if (existing) {
+        clearTimeout(existing.timer)
+        pendingDeletes.delete(key)
+      }
+    }
+
+    const deletedOpenEditorsRaw = batchPaths.deletedOpenEditors
+    // Only pay the per-id lookup to suppress a move's own source-delete while a move is live; otherwise the batch stays O(deletes).
+    const deletedOpenEditors = hasActiveEditorPathMoves()
+      ? deletedOpenEditorsRaw.filter(
+          ({ file }) =>
+            !isActiveMoveSourcePath(target.worktreeId, target.runtimeEnvironmentId, file.filePath)
+        )
+      : deletedOpenEditorsRaw
+    const deletedOpenEditorIds = deletedOpenEditors.map(({ file }) => file.id)
+    const hasPairedCreate =
+      deletedOpenEditorIds.length > 0 &&
+      hasRenameCorrelatedCreate(payload, target.worktreeId, deletedOpenEditorIds, openFilesAtStart)
+    if (deletedOpenEditorIds.length > 0) {
+      if (hasPairedCreate) {
+        const setExternalMutation = useAppStore.getState().setExternalMutation
+        for (const fileId of deletedOpenEditorIds) {
+          setExternalMutation(fileId, 'renamed')
+        }
+      } else {
+        for (const { file, normalizedDeletePath } of deletedOpenEditors) {
+          const key = pendingKey(
+            target.worktreeId,
+            target.runtimeEnvironmentId,
+            normalizedDeletePath
+          )
+          const existing = pendingDeletes.get(key)
+          if (existing) {
+            clearTimeout(existing.timer)
+            pendingDeletes.delete(key)
+          }
+          const timer = setTimeout(() => {
+            pendingDeletes.delete(key)
+            // Why: the debounce window lets the tab close or leave edit mode, so re-check before writing to avoid tombstoning a stale tab.
+            const state = useAppStore.getState()
+            const stillEditing = state.openFiles.some(
+              (candidate) => candidate.id === file.id && candidate.mode === 'edit'
+            )
+            if (stillEditing) {
+              state.setExternalMutation(file.id, 'deleted')
+            }
+          }, EXTERNAL_MUTATION_DEBOUNCE_MS)
+          pendingDeletes.set(key, { fileId: file.id, timer })
+        }
+      }
+    }
+
+    // Why: a reappearing file clears deleted/renamed tombstones, but a changed mark resolves only through reload/save.
+    if (createOrUpdatePaths.size > 0) {
+      const state = useAppStore.getState()
+      for (const file of state.openFiles) {
+        if (
+          file.worktreeId === target.worktreeId &&
+          getOpenFileRuntimeOwner(file) === target.runtimeEnvironmentId &&
+          (file.mode === 'edit' || file.mode === 'markdown-preview') &&
+          (file.externalMutation === 'deleted' || file.externalMutation === 'renamed') &&
+          batchPaths.matchesCreateOrUpdate(file)
+        ) {
+          state.setExternalMutation(file.id, null)
+        }
+      }
+    }
+
+    if (payload.events.some((event) => event.kind === 'overflow')) {
+      // Why: overflow omits paths, so reload clean tabs and clear tombstones that may have been resurrected during the overrun.
+      for (const notification of collectOverflowEditorExternalReloadTargets(target)) {
+        scheduleDebouncedEditorExternalReload(notification)
+      }
+      return
+    }
+    if (batchPaths.changes.length === 0) {
+      return
+    }
+
+    for (const change of batchPaths.changes) {
+      const matching = batchPaths.matchingOpenFiles(change)
+      const notification: EditorExternalWatchNotification = {
+        worktreeId: target.worktreeId,
+        worktreePath: target.worktreePath,
+        relativePath: change.relativePath,
+        runtimeEnvironmentId: target.runtimeEnvironmentId,
+        ...getLocalWindowsWslAliasOption(target)
+      }
+      Object.defineProperty(notification, 'indexedOpenFiles', {
+        value: {
+          matches: (openFiles: OpenFile[]) => batchPaths.matchingOpenFiles(change, openFiles)
+        }
+      })
+      if (matching.length === 0) {
+        if (batchPaths.hasCombinedDiffConsumer) {
+          scheduleDebouncedEditorExternalReload(notification)
+        }
+        continue
+      }
+      const dirtyMatches = matching.filter((file) => file.isDirty)
+      if (dirtyMatches.length > 0) {
+        const dirtyIds = dirtyMatches
+          .filter((file) => canAutoSaveOpenFile(file))
+          .map((file) => file.id)
+        let isSelfMoveEcho = false
+        if (dirtyMatches.some((file) => file.pendingSelfMoveEcho)) {
+          const normalizedAbsolutePath = normalizeRuntimePathForComparison(change.absolutePath)
+          isSelfMoveEcho = dirtyMatches.some(
+            (file) =>
+              file.pendingSelfMoveEcho &&
+              normalizeRuntimePathForComparison(file.pendingSelfMoveEcho.targetPath) ===
+                normalizedAbsolutePath
+          )
+        }
+        if (isSelfMoveEcho) {
+          scheduleEditorSelfMoveEchoVerification(target, dirtyIds, true)
+        } else {
+          scheduleEditorChangedOnDiskMark(target, notification, dirtyIds)
+        }
+        if (dirtyMatches.length === matching.length) {
+          if (batchPaths.hasCombinedDiffConsumer) {
+            scheduleDebouncedEditorExternalReload(notification)
+          }
+          continue
+        }
+      }
+      const recentSelfWrite = getRecentSelfWrite(change.absolutePath, target.runtimeEnvironmentId)
+      if (recentSelfWrite) {
+        scheduleSelfWriteAwareEditorExternalReload(
+          target,
+          notification,
+          matching[0],
+          recentSelfWrite
+        )
+        continue
+      }
+      scheduleDebouncedEditorExternalReload(notification)
+    }
+  }
+
+  const dispose = (): void => {
+    for (const pending of pendingDeletes.values()) {
+      clearTimeout(pending.timer)
+    }
+    pendingDeletes.clear()
+  }
+
+  return { handleFsChanged, dispose }
+}
+
+export function collectOverflowEditorExternalReloadTargets(
+  target: Pick<EditorExternalWatchTarget, 'worktreeId' | 'worktreePath'> &
+    Partial<
+      Pick<
+        EditorExternalWatchTarget,
+        'connectionId' | 'runtimeEnvironmentId' | 'allowLocalWindowsWslAliases'
+      >
+    >
+): EditorExternalWatchNotification[] {
+  const state = useAppStore.getState()
+  const notifications: EditorExternalWatchNotification[] = []
+  for (const file of state.openFiles) {
+    if (
+      file.worktreeId !== target.worktreeId ||
+      getOpenFileRuntimeOwner(file) !== (target.runtimeEnvironmentId ?? null) ||
+      !isExternalReloadableEditorTab(file) ||
+      file.isDirty
+    ) {
+      continue
+    }
+    if (file.externalMutation) {
+      state.setExternalMutation(file.id, null)
+    }
+    notifications.push({
+      worktreeId: target.worktreeId,
+      worktreePath: target.worktreePath,
+      relativePath: file.relativePath,
+      runtimeEnvironmentId: target.runtimeEnvironmentId ?? null,
+      ...getLocalWindowsWslAliasOption(target)
+    })
+  }
+  return notifications
+}
+
+function hasRenameCorrelatedCreate(
+  payload: FsChangedPayload,
+  worktreeId: string,
+  deletedOpenEditorIds: string[],
+  openFiles: OpenFile[]
+): boolean {
+  if (deletedOpenEditorIds.length === 0) {
+    return false
+  }
+  const deletedIdSet = new Set(deletedOpenEditorIds)
+  const deletedBasenames = new Set<string>()
+  for (const file of openFiles) {
+    if (
+      file.worktreeId !== worktreeId ||
+      (file.mode !== 'edit' && file.mode !== 'markdown-preview') ||
+      !deletedIdSet.has(file.id)
+    ) {
+      continue
+    }
+    deletedBasenames.add(basename(file.filePath))
+  }
+  if (deletedBasenames.size === 0) {
+    return false
+  }
+  return payload.events.some(
+    (event) =>
+      event.kind === 'create' &&
+      event.isDirectory !== true &&
+      deletedBasenames.has(basename(event.absolutePath))
+  )
+}
diff --git a/src/renderer/src/hooks/editor-external-watch-targets.ts b/src/renderer/src/hooks/editor-external-watch-targets.ts
new file mode 100644
index 00000000000..715d64e10ce
--- /dev/null
+++ b/src/renderer/src/hooks/editor-external-watch-targets.ts
@@ -0,0 +1,260 @@
+import type { AppState } from '@/store'
+import type { OpenFile } from '@/store/slices/editor'
+import { findWorktreeById } from '@/store/slices/worktree-helpers'
+import { findRepoForHost } from '@/store/slices/repo-host-identity'
+import { getFolderWorkspaceConnectionId } from '@/lib/folder-workspace-connection'
+import { isLocalWindowsDesktopClient } from '@/lib/desktop-window-chrome'
+import { getRuntimeEnvironmentIdForWorktree } from '@/lib/worktree-runtime-owner'
+import { isWindowsAbsolutePathLike } from '../../../shared/cross-platform-path'
+import { parseExecutionHostId } from '../../../shared/execution-host'
+import { isGitRepoKind } from '../../../shared/repo-kind'
+import { parseWorkspaceKey } from '../../../shared/workspace-scope'
+
+export type EditorExternalWatchTarget = {
+  worktreeId: string
+  worktreePath: string
+  connectionId: string | undefined
+  runtimeEnvironmentId: string | null
+  allowLocalWindowsWslAliases?: true
+}
+
+export type EditorExternalWatchTargetState = Pick<
+  AppState,
+  | 'openFiles'
+  | 'worktreesByRepo'
+  | 'repos'
+  | 'activeWorktreeId'
+  | 'settings'
+  | 'rightSidebarOpen'
+  | 'rightSidebarTab'
+  | 'rightSidebarExplorerView'
+  | 'gitStatusHugeByWorktree'
+  | 'sshConnectionStates'
+  | 'folderWorkspaces'
+  | 'projectGroups'
+>
+
+type WatchedTargetsSnapshot = {
+  targets: EditorExternalWatchTarget[]
+  targetsKey: string
+}
+
+let cachedOpenFiles: AppState['openFiles'] | null = null
+let cachedWorktreesByRepo: AppState['worktreesByRepo'] | null = null
+let cachedRepos: AppState['repos'] | null = null
+let cachedActiveWorktreeId: string | null = null
+let cachedRuntimeEnvironmentId: string | undefined
+let cachedRightSidebarOpen: boolean | null = null
+let cachedRightSidebarTab: AppState['rightSidebarTab'] | null = null
+let cachedRightSidebarExplorerView: AppState['rightSidebarExplorerView'] | null = null
+let cachedGitStatusHugeByWorktree: AppState['gitStatusHugeByWorktree'] | null = null
+let cachedSshConnectionStates: AppState['sshConnectionStates'] | null = null
+let cachedFolderWorkspaces: AppState['folderWorkspaces'] | null = null
+let cachedProjectGroups: AppState['projectGroups'] | null = null
+let cachedWatchedTargetsSnapshot: WatchedTargetsSnapshot = { targets: [], targetsKey: '' }
+
+export function getEditorExternalWatchTargetKey(target: EditorExternalWatchTarget): string {
+  // Why: include connectionId so a local placeholder watch is replaced by the real SSH watch once an SSH worktree's provider metadata hydrates.
+  return `${target.worktreeId}::${target.worktreePath}::${target.connectionId ?? 'local'}::${target.runtimeEnvironmentId ?? 'client'}::${target.allowLocalWindowsWslAliases === true ? 'wsl-aliases' : 'literal'}`
+}
+
+export function getOpenFileRuntimeOwner(
+  file: Pick<OpenFile, 'runtimeEnvironmentId'>
+): string | null {
+  return file.runtimeEnvironmentId?.trim() || null
+}
+
+export function getLocalWindowsWslAliasOption(
+  target: Pick<EditorExternalWatchTarget, 'allowLocalWindowsWslAliases'>
+): Pick<EditorExternalWatchTarget, 'allowLocalWindowsWslAliases'> {
+  return isLocalWindowsDesktopClient() && target.allowLocalWindowsWslAliases === true
+    ? { allowLocalWindowsWslAliases: true }
+    : {}
+}
+
+function isLocalHostStamp(value: string | null | undefined): boolean {
+  return parseExecutionHostId(value)?.kind === 'local'
+}
+
+function canWatchLocalWindowsWslAliases(args: {
+  worktreePath: string
+  runtimeEnvironmentId: string | null
+  connectionId: string | null | undefined
+  worktree: AppState['worktreesByRepo'][string][number] | undefined
+  repo: AppState['repos'][number] | undefined
+  folderWorkspace: AppState['folderWorkspaces'][number] | undefined
+  projectGroup: AppState['projectGroups'][number] | undefined
+}): boolean {
+  if (
+    args.runtimeEnvironmentId !== null ||
+    args.connectionId !== null ||
+    !isWindowsAbsolutePathLike(args.worktreePath)
+  ) {
+    return false
+  }
+  if (args.worktree) {
+    return (
+      !!args.repo &&
+      !args.worktree.runtimeOwnerEnvironmentId?.trim() &&
+      isLocalHostStamp(args.worktree.hostId) &&
+      isLocalHostStamp(args.repo.executionHostId)
+    )
+  }
+  return (
+    !!args.folderWorkspace &&
+    isLocalHostStamp(args.folderWorkspace.executionHostId) &&
+    isLocalHostStamp(args.projectGroup?.executionHostId)
+  )
+}
+
+export function selectEditorExternalWatchTargets(
+  state: EditorExternalWatchTargetState
+): WatchedTargetsSnapshot {
+  const runtimeEnvironmentId = state.settings?.activeRuntimeEnvironmentId?.trim() || undefined
+  if (
+    cachedOpenFiles === state.openFiles &&
+    cachedWorktreesByRepo === state.worktreesByRepo &&
+    cachedRepos === state.repos &&
+    cachedActiveWorktreeId === state.activeWorktreeId &&
+    cachedRuntimeEnvironmentId === runtimeEnvironmentId &&
+    cachedRightSidebarOpen === state.rightSidebarOpen &&
+    cachedRightSidebarTab === state.rightSidebarTab &&
+    cachedRightSidebarExplorerView === state.rightSidebarExplorerView &&
+    cachedGitStatusHugeByWorktree === state.gitStatusHugeByWorktree &&
+    cachedSshConnectionStates === state.sshConnectionStates &&
+    cachedFolderWorkspaces === state.folderWorkspaces &&
+    cachedProjectGroups === state.projectGroups
+  ) {
+    return cachedWatchedTargetsSnapshot
+  }
+
+  const targetOwnersByWorktreeId = new Map<string, Set<string | null>>()
+  // Why: watcher ownership is scoped by worktree + runtime owner — the same path can be open locally and in a runtime workspace, and reads/saves already route per owner.
+  for (const file of state.openFiles) {
+    let owners = targetOwnersByWorktreeId.get(file.worktreeId)
+    if (!owners) {
+      owners = new Set()
+      targetOwnersByWorktreeId.set(file.worktreeId, owners)
+    }
+    // Why: persisted/restored tabs may have runtimeEnvironmentId undefined; new openFile calls resolve inheritance before storing, so an ownerless tab stays local.
+    owners.add(getOpenFileRuntimeOwner(file))
+  }
+  const activeWorktreeId = state.activeWorktreeId
+  const activeWorktree = activeWorktreeId
+    ? findWorktreeById(state.worktreesByRepo, activeWorktreeId)
+    : undefined
+  const activeWorktreeHost = parseExecutionHostId(activeWorktree?.hostId)
+  const activeRepo = activeWorktree
+    ? activeWorktreeHost?.kind === 'local'
+      ? (findRepoForHost(state.repos, activeWorktree.repoId, {
+          hostId: activeWorktreeHost.id
+        }) ?? undefined)
+      : state.repos.find((repo) => repo.id === activeWorktree.repoId)
+    : undefined
+  const sourceControlCanConsumeWatch =
+    !!activeWorktreeId &&
+    !!activeRepo &&
+    isGitRepoKind(activeRepo) &&
+    !state.gitStatusHugeByWorktree[activeWorktreeId] &&
+    (!activeRepo.connectionId ||
+      state.sshConnectionStates.get(activeRepo.connectionId)?.status === 'connected')
+  const activeWorktreeNeedsSidebarWatch =
+    activeWorktreeId !== null &&
+    state.rightSidebarOpen &&
+    ((state.rightSidebarTab === 'explorer' && state.rightSidebarExplorerView === 'files') ||
+      (state.rightSidebarTab === 'source-control' && sourceControlCanConsumeWatch))
+  if (activeWorktreeNeedsSidebarWatch) {
+    // Why: this app-level watcher owns Explorer/Source-Control subscriptions so downstream consumers don't fight over watch/unwatch IPC.
+    let owners = targetOwnersByWorktreeId.get(activeWorktreeId)
+    if (!owners) {
+      owners = new Set()
+      targetOwnersByWorktreeId.set(activeWorktreeId, owners)
+    }
+    // Why: sidebar watcher must follow the selected worktree's host owner, not the host currently focused in the UI.
+    owners.add(getRuntimeEnvironmentIdForWorktree(state, activeWorktreeId))
+  }
+
+  const nextTargets: EditorExternalWatchTarget[] = []
+  const parts: string[] = []
+  const sortedWorktreeIds = Array.from(targetOwnersByWorktreeId.keys()).sort()
+  for (const id of sortedWorktreeIds) {
+    const worktree = findWorktreeById(state.worktreesByRepo, id)
+    const workspaceScope = parseWorkspaceKey(id)
+    const folderWorkspace =
+      workspaceScope?.type === 'folder'
+        ? state.folderWorkspaces.find(
+            (workspace) => workspace.id === workspaceScope.folderWorkspaceId
+          )
+        : undefined
+    if (!worktree && !folderWorkspace) {
+      continue
+    }
+    const worktreeHost = parseExecutionHostId(worktree?.hostId)
+    const repo = worktree
+      ? worktreeHost?.kind === 'local'
+        ? (findRepoForHost(state.repos, worktree.repoId, { hostId: worktreeHost.id }) ?? undefined)
+        : state.repos.find((candidate) => candidate.id === worktree.repoId)
+      : undefined
+    const folderHostId = parseExecutionHostId(folderWorkspace?.executionHostId)?.id
+    const projectGroup = folderWorkspace
+      ? state.projectGroups.find(
+          (group) =>
+            group.id === folderWorkspace.projectGroupId &&
+            parseExecutionHostId(group.executionHostId)?.id === folderHostId
+        )
+      : undefined
+    const connectionId = folderWorkspace
+      ? getFolderWorkspaceConnectionId(state, folderWorkspace.id)
+      : repo
+        ? (repo.connectionId ?? null)
+        : undefined
+    if (connectionId === undefined && folderWorkspace) {
+      continue
+    }
+    const owners = Array.from(targetOwnersByWorktreeId.get(id) ?? []).sort((left, right) =>
+      (left ?? '').localeCompare(right ?? '')
+    )
+    for (const owner of owners) {
+      const target = {
+        worktreeId: id,
+        worktreePath: worktree?.path ?? folderWorkspace!.folderPath,
+        connectionId: connectionId ?? undefined,
+        runtimeEnvironmentId: owner,
+        ...(canWatchLocalWindowsWslAliases({
+          worktreePath: worktree?.path ?? folderWorkspace!.folderPath,
+          runtimeEnvironmentId: owner,
+          connectionId,
+          worktree,
+          repo,
+          folderWorkspace,
+          projectGroup
+        })
+          ? { allowLocalWindowsWslAliases: true as const }
+          : {})
+      }
+      nextTargets.push(target)
+      parts.push(getEditorExternalWatchTargetKey(target))
+    }
+  }
+
+  const targetsKey = parts.join('|')
+  cachedOpenFiles = state.openFiles
+  cachedWorktreesByRepo = state.worktreesByRepo
+  cachedRepos = state.repos
+  cachedActiveWorktreeId = state.activeWorktreeId
+  cachedRuntimeEnvironmentId = runtimeEnvironmentId
+  cachedRightSidebarOpen = state.rightSidebarOpen
+  cachedRightSidebarTab = state.rightSidebarTab
+  cachedRightSidebarExplorerView = state.rightSidebarExplorerView
+  cachedGitStatusHugeByWorktree = state.gitStatusHugeByWorktree
+  cachedSshConnectionStates = state.sshConnectionStates
+  cachedFolderWorkspaces = state.folderWorkspaces
+  cachedProjectGroups = state.projectGroups
+
+  if (targetsKey === cachedWatchedTargetsSnapshot.targetsKey) {
+    return cachedWatchedTargetsSnapshot
+  }
+
+  cachedWatchedTargetsSnapshot = { targets: nextTargets, targetsKey }
+  return cachedWatchedTargetsSnapshot
+}
diff --git a/src/renderer/src/hooks/useEditorExternalWatch-subscriptions.test.tsx b/src/renderer/src/hooks/useEditorExternalWatch-subscriptions.test.tsx
new file mode 100644
index 00000000000..ad0ee0a09d9
--- /dev/null
+++ b/src/renderer/src/hooks/useEditorExternalWatch-subscriptions.test.tsx
@@ -0,0 +1,187 @@
+// @vitest-environment happy-dom
+
+import { afterEach, beforeEach, describe, expect, it, vi } from 'vitest'
+import { act, createElement } from 'react'
+import { createRoot, type Root } from 'react-dom/client'
+
+type TestWatchTarget = {
+  worktreeId: string
+  worktreePath: string
+  connectionId: string | undefined
+  runtimeEnvironmentId: string | null
+  allowLocalWindowsWslAliases?: true
+}
+
+const subscriptionState = vi.hoisted(() => ({
+  snapshot: { targets: [] as TestWatchTarget[], targetsKey: '' },
+  subscribeRuntimeFileChanges: vi.fn(),
+  disposeEventHandler: vi.fn()
+}))
+
+vi.mock('@/store', () => ({
+  useAppStore: (selector: (state: unknown) => unknown) => selector({})
+}))
+vi.mock('@/runtime/runtime-file-client', () => ({
+  subscribeRuntimeFileChanges: subscriptionState.subscribeRuntimeFileChanges
+}))
+vi.mock('./editor-external-watch-targets', () => ({
+  selectEditorExternalWatchTargets: () => subscriptionState.snapshot,
+  getEditorExternalWatchTargetKey: (target: TestWatchTarget) =>
+    [
+      target.worktreeId,
+      target.worktreePath,
+      target.connectionId ?? 'local',
+      target.runtimeEnvironmentId ?? 'client',
+      target.allowLocalWindowsWslAliases ? 'wsl-aliases' : 'literal'
+    ].join('::')
+}))
+vi.mock('./editor-external-watch-event-reconciliation', () => ({
+  buildEditorExternalWatchEventHandler: vi.fn(() => ({
+    handleFsChanged: vi.fn(),
+    dispose: subscriptionState.disposeEventHandler
+  })),
+  collectOverflowEditorExternalReloadTargets: vi.fn()
+}))
+vi.mock('./editor-external-watch-disk-verification', () => ({
+  verifyLatchedEditorMoveDestinations: vi.fn()
+}))
+
+import { useEditorExternalWatch } from './useEditorExternalWatch'
+
+function WatchProbe(): null {
+  useEditorExternalWatch()
+  return null
+}
+
+function runtimeTarget(): TestWatchTarget {
+  return {
+    worktreeId: 'wt-runtime',
+    worktreePath: '/runtime/repo',
+    connectionId: 'nested-ssh',
+    runtimeEnvironmentId: 'runtime-1'
+  }
+}
+
+function deferredRuntimeSubscription(): {
+  promise: Promise<() => void>
+  resolve: (unsubscribe: () => void) => void
+} {
+  let resolve!: (unsubscribe: () => void) => void
+  const promise = new Promise<() => void>((settle) => {
+    resolve = settle
+  })
+  return { promise, resolve }
+}
+
+describe('useEditorExternalWatch subscriptions', () => {
+  let previousApi: unknown
+  let container: HTMLDivElement
+  let root: Root
+  let watchWorktree: ReturnType<typeof vi.fn>
+  let unwatchWorktree: ReturnType<typeof vi.fn>
+  let unsubscribeFsEvents: ReturnType<typeof vi.fn>
+
+  beforeEach(() => {
+    vi.clearAllMocks()
+    subscriptionState.snapshot = { targets: [], targetsKey: '' }
+    watchWorktree = vi.fn().mockResolvedValue(undefined)
+    unwatchWorktree = vi.fn().mockResolvedValue(undefined)
+    unsubscribeFsEvents = vi.fn()
+    previousApi = (window as unknown as { api?: unknown }).api
+    ;(window as unknown as { api: unknown }).api = {
+      fs: {
+        watchWorktree,
+        unwatchWorktree,
+        onFsChanged: vi.fn(() => unsubscribeFsEvents)
+      }
+    }
+    container = document.body.appendChild(document.createElement('div'))
+    root = createRoot(container)
+  })
+
+  afterEach(async () => {
+    await act(async () => root.unmount())
+    container.remove()
+    ;(window as unknown as { api?: unknown }).api = previousApi
+  })
+
+  it('unsubscribes an SSH watch and the shared event listener exactly once on unmount', async () => {
+    subscriptionState.snapshot = {
+      targets: [
+        {
+          worktreeId: 'wt-ssh',
+          worktreePath: '/remote/repo',
+          connectionId: 'ssh-1',
+          runtimeEnvironmentId: null
+        }
+      ],
+      targetsKey: 'ssh-watch'
+    }
+    await act(async () => root.render(createElement(WatchProbe)))
+
+    expect(watchWorktree).toHaveBeenCalledWith({
+      worktreePath: '/remote/repo',
+      connectionId: 'ssh-1'
+    })
+    await act(async () => root.unmount())
+
+    expect(unwatchWorktree).toHaveBeenCalledTimes(1)
+    expect(unwatchWorktree).toHaveBeenCalledWith({
+      worktreePath: '/remote/repo',
+      connectionId: 'ssh-1'
+    })
+    expect(unsubscribeFsEvents).toHaveBeenCalledTimes(1)
+    expect(subscriptionState.disposeEventHandler).toHaveBeenCalledTimes(1)
+  })
+
+  it('disposes a runtime subscription that resolves after unmount', async () => {
+    const pending = deferredRuntimeSubscription()
+    const unsubscribeRuntime = vi.fn()
+    subscriptionState.subscribeRuntimeFileChanges.mockReturnValueOnce(pending.promise)
+    subscriptionState.snapshot = {
+      targets: [runtimeTarget()],
+      targetsKey: 'runtime-watch'
+    }
+    await act(async () => root.render(createElement(WatchProbe)))
+    await act(async () => root.unmount())
+
+    pending.resolve(unsubscribeRuntime)
+    await act(async () => pending.promise)
+
+    expect(unsubscribeRuntime).toHaveBeenCalledTimes(1)
+    expect(unwatchWorktree).not.toHaveBeenCalled()
+  })
+
+  it('cannot let an old runtime subscribe resolution replace a re-added watch', async () => {
+    const stalePending = deferredRuntimeSubscription()
+    const currentPending = deferredRuntimeSubscription()
+    const unsubscribeStale = vi.fn()
+    const unsubscribeCurrent = vi.fn()
+    subscriptionState.subscribeRuntimeFileChanges
+      .mockReturnValueOnce(stalePending.promise)
+      .mockReturnValueOnce(currentPending.promise)
+    subscriptionState.snapshot = {
+      targets: [runtimeTarget()],
+      targetsKey: 'runtime-watch-1'
+    }
+    await act(async () => root.render(createElement(WatchProbe)))
+
+    subscriptionState.snapshot = { targets: [], targetsKey: 'no-runtime-watch' }
+    await act(async () => root.render(createElement(WatchProbe)))
+    subscriptionState.snapshot = {
+      targets: [runtimeTarget()],
+      targetsKey: 'runtime-watch-2'
+    }
+    await act(async () => root.render(createElement(WatchProbe)))
+
+    currentPending.resolve(unsubscribeCurrent)
+    await act(async () => currentPending.promise)
+    stalePending.resolve(unsubscribeStale)
+    await act(async () => stalePending.promise)
+    expect(unsubscribeStale).toHaveBeenCalledTimes(1)
+    expect(unsubscribeCurrent).not.toHaveBeenCalled()
+
+    await act(async () => root.unmount())
+    expect(unsubscribeCurrent).toHaveBeenCalledTimes(1)
+  })
+})
diff --git a/src/renderer/src/hooks/useEditorExternalWatch.ts b/src/renderer/src/hooks/useEditorExternalWatch.ts
index 304390a6b42..20f02e719d5 100644
--- a/src/renderer/src/hooks/useEditorExternalWatch.ts
+++ b/src/renderer/src/hooks/useEditorExternalWatch.ts
@@ -1,50 +1,23 @@
-/* eslint-disable max-lines -- co-locates target diffing, fs:changed dispatch, tombstone coalescing, and rename correlation so the event-to-store contract stays in one file. */
 import { useEffect, useRef } from 'react'
-import { useAppStore, type AppState } from '@/store'
-import { basename, joinPath } from '@/lib/path'
-import {
-  isWindowsAbsolutePathLike,
-  normalizeRuntimePathForComparison
-} from '../../../shared/cross-platform-path'
-import {
-  canAutoSaveOpenFile,
-  getOpenFilesForExternalFileChange,
-  isExternalReloadableEditorTab,
-  notifyEditorExternalFileChange
-} from '@/components/editor/editor-autosave'
-import { indexEditorExternalWatchBatchPaths } from '@/components/editor/editor-external-watch-path-index'
-import {
-  clearSelfWrite,
-  getRecentSelfWrite,
-  type RecentSelfWrite
-} from '@/components/editor/editor-self-write-registry'
-import {
-  hasActiveEditorPathMoves,
-  isActiveMoveSourcePath
-} from '@/components/editor/editor-path-move-inflight'
+import { useAppStore } from '@/store'
+import { subscribeRuntimeFileChanges } from '@/runtime/runtime-file-client'
+import { normalizeRuntimePathForComparison } from '../../../shared/cross-platform-path'
 import type { FsChangedPayload } from '../../../shared/filesystem-entry-types'
-import { findWorktreeById } from '@/store/slices/worktree-helpers'
-import type { OpenFile } from '@/store/slices/editor'
-import { readRuntimeFileContent, subscribeRuntimeFileChanges } from '@/runtime/runtime-file-client'
-import { getRuntimeEnvironmentIdForWorktree } from '@/lib/worktree-runtime-owner'
 import {
-  ORCA_WORKTREE_FILE_CHANGE_EVENT,
-  type WorktreeFileChangeEventDetail
-} from './worktree-file-change-event'
-import { isGitRepoKind } from '../../../shared/repo-kind'
-import { markFileChangedOnDisk } from '@/components/editor/editor-changed-on-disk-mark'
-import { getDiskBaselineSignature } from '@/components/editor/diff-content-signature'
-import { parseWorkspaceKey } from '../../../shared/workspace-scope'
-import { getFolderWorkspaceConnectionId } from '@/lib/folder-workspace-connection'
-import { isLocalWindowsDesktopClient } from '@/lib/desktop-window-chrome'
-import { parseExecutionHostId } from '../../../shared/execution-host'
-import { findRepoForHost } from '@/store/slices/repo-host-identity'
+  getEditorExternalWatchTargetKey,
+  selectEditorExternalWatchTargets,
+  type EditorExternalWatchTarget,
+  type EditorExternalWatchTargetState as EditorExternalWatchTargetStateShape
+} from './editor-external-watch-targets'
+import {
+  buildEditorExternalWatchEventHandler,
+  collectOverflowEditorExternalReloadTargets
+} from './editor-external-watch-event-reconciliation'
+import { verifyLatchedEditorMoveDestinations } from './editor-external-watch-disk-verification'
 
-// Why: atomic writes burst same-path events; one reload dispatch each fans out into N EditorPanel rebuilds that can wedge the renderer (issue #826), so debounce per (worktreeId+path).
-const EXTERNAL_RELOAD_DEBOUNCE_MS = 75
-const pendingExternalReloadTimers = new Map<string, ReturnType<typeof setTimeout>>()
+export type EditorExternalWatchTargetState = EditorExternalWatchTargetStateShape
 
-function warnExternalWatchFailure(target: WatchedTarget, err: unknown): void {
+function warnExternalWatchFailure(target: EditorExternalWatchTarget, err: unknown): void {
   console.warn('[filesystem-watch] failed to watch worktree', {
     worktreeId: target.worktreeId,
     worktreePath: target.worktreePath,
@@ -53,319 +26,32 @@ function warnExternalWatchFailure(target: WatchedTarget, err: unknown): void {
   })
 }
 
-function scheduleDebouncedExternalReload(notification: {
-  worktreeId: string
-  worktreePath: string
-  relativePath: string
-  runtimeEnvironmentId: string | null
-}): void {
-  const key = `${notification.worktreeId}::${notification.runtimeEnvironmentId ?? 'client'}::${notification.relativePath}`
-  const existing = pendingExternalReloadTimers.get(key)
-  if (existing !== undefined) {
-    globalThis.clearTimeout(existing)
-  }
-  const handle = globalThis.setTimeout(() => {
-    pendingExternalReloadTimers.delete(key)
-    notifyEditorExternalFileChange(notification)
-  }, EXTERNAL_RELOAD_DEBOUNCE_MS)
-  pendingExternalReloadTimers.set(key, handle)
-}
-
-type WatchedTarget = {
-  worktreeId: string
-  worktreePath: string
-  connectionId: string | undefined
-  runtimeEnvironmentId: string | null
-  allowLocalWindowsWslAliases?: true
-}
-
-type ExternalWatchNotification = {
-  worktreeId: string
-  worktreePath: string
-  relativePath: string
-  runtimeEnvironmentId: string | null
-  allowLocalWindowsWslAliases?: true
-  indexedOpenFiles?: {
-    matches: (openFiles: OpenFile[]) => OpenFile[]
-  }
-}
-
-function localWslAliasOption(
-  target: Pick<WatchedTarget, 'allowLocalWindowsWslAliases'>
-): Pick<ExternalWatchNotification, 'allowLocalWindowsWslAliases'> {
-  return isLocalWindowsDesktopClient() && target.allowLocalWindowsWslAliases === true
-    ? { allowLocalWindowsWslAliases: true }
-    : {}
-}
-
-function isLocalHostStamp(value: string | null | undefined): boolean {
-  return parseExecutionHostId(value)?.kind === 'local'
-}
-
-function canWatchLocalWindowsWslAliases(args: {
-  worktreePath: string
-  runtimeEnvironmentId: string | null
-  connectionId: string | null | undefined
-  worktree: AppState['worktreesByRepo'][string][number] | undefined
-  repo: AppState['repos'][number] | undefined
-  folderWorkspace: AppState['folderWorkspaces'][number] | undefined
-  projectGroup: AppState['projectGroups'][number] | undefined
-}): boolean {
-  if (
-    args.runtimeEnvironmentId !== null ||
-    args.connectionId !== null ||
-    !isWindowsAbsolutePathLike(args.worktreePath)
-  ) {
-    return false
-  }
-  if (args.worktree) {
-    return (
-      !!args.repo &&
-      !args.worktree.runtimeOwnerEnvironmentId?.trim() &&
-      isLocalHostStamp(args.worktree.hostId) &&
-      isLocalHostStamp(args.repo.executionHostId)
-    )
-  }
-  return (
-    !!args.folderWorkspace &&
-    isLocalHostStamp(args.folderWorkspace.executionHostId) &&
-    isLocalHostStamp(args.projectGroup?.executionHostId)
-  )
-}
-
-type WatchedTargetsSnapshot = {
-  targets: WatchedTarget[]
-  targetsKey: string
-}
-
-export type EditorExternalWatchTargetState = Pick<
-  AppState,
-  | 'openFiles'
-  | 'worktreesByRepo'
-  | 'repos'
-  | 'activeWorktreeId'
-  | 'settings'
-  | 'rightSidebarOpen'
-  | 'rightSidebarTab'
-  | 'rightSidebarExplorerView'
-  | 'gitStatusHugeByWorktree'
-  | 'sshConnectionStates'
-  | 'folderWorkspaces'
-  | 'projectGroups'
->
-
-let cachedOpenFiles: AppState['openFiles'] | null = null
-let cachedWorktreesByRepo: AppState['worktreesByRepo'] | null = null
-let cachedRepos: AppState['repos'] | null = null
-let cachedActiveWorktreeId: string | null = null
-let cachedRuntimeEnvironmentId: string | undefined
-let cachedRightSidebarOpen: boolean | null = null
-let cachedRightSidebarTab: AppState['rightSidebarTab'] | null = null
-let cachedRightSidebarExplorerView: AppState['rightSidebarExplorerView'] | null = null
-let cachedGitStatusHugeByWorktree: AppState['gitStatusHugeByWorktree'] | null = null
-let cachedSshConnectionStates: AppState['sshConnectionStates'] | null = null
-let cachedFolderWorkspaces: AppState['folderWorkspaces'] | null = null
-let cachedProjectGroups: AppState['projectGroups'] | null = null
-let cachedWatchedTargetsSnapshot: WatchedTargetsSnapshot = { targets: [], targetsKey: '' }
-
-export function getWatchedTargetKey(target: WatchedTarget): string {
-  // Why: include connectionId so a local placeholder watch is replaced by the real SSH watch once an SSH worktree's provider metadata hydrates.
-  return `${target.worktreeId}::${target.worktreePath}::${target.connectionId ?? 'local'}::${target.runtimeEnvironmentId ?? 'client'}::${target.allowLocalWindowsWslAliases === true ? 'wsl-aliases' : 'literal'}`
-}
-
-function openFileRuntimeOwner(file: Pick<OpenFile, 'runtimeEnvironmentId'>): string | null {
-  return file.runtimeEnvironmentId?.trim() || null
-}
-
-export function getEditorExternalWatchTargets(
-  state: EditorExternalWatchTargetState
-): WatchedTargetsSnapshot {
-  const runtimeEnvironmentId = state.settings?.activeRuntimeEnvironmentId?.trim() || undefined
-  if (
-    cachedOpenFiles === state.openFiles &&
-    cachedWorktreesByRepo === state.worktreesByRepo &&
-    cachedRepos === state.repos &&
-    cachedActiveWorktreeId === state.activeWorktreeId &&
-    cachedRuntimeEnvironmentId === runtimeEnvironmentId &&
-    cachedRightSidebarOpen === state.rightSidebarOpen &&
-    cachedRightSidebarTab === state.rightSidebarTab &&
-    cachedRightSidebarExplorerView === state.rightSidebarExplorerView &&
-    cachedGitStatusHugeByWorktree === state.gitStatusHugeByWorktree &&
-    cachedSshConnectionStates === state.sshConnectionStates &&
-    cachedFolderWorkspaces === state.folderWorkspaces &&
-    cachedProjectGroups === state.projectGroups
-  ) {
-    return cachedWatchedTargetsSnapshot
-  }
-
-  const targetOwnersByWorktreeId = new Map<string, Set<string | null>>()
-  // Why: watcher ownership is scoped by worktree + runtime owner — the same path can be open locally and in a runtime workspace, and reads/saves already route per owner.
-  for (const f of state.openFiles) {
-    let owners = targetOwnersByWorktreeId.get(f.worktreeId)
-    if (!owners) {
-      owners = new Set()
-      targetOwnersByWorktreeId.set(f.worktreeId, owners)
-    }
-    // Why: persisted/restored tabs may have runtimeEnvironmentId undefined; new openFile calls resolve inheritance before storing, so an ownerless tab stays local.
-    owners.add(openFileRuntimeOwner(f))
-  }
-  const activeWorktreeId = state.activeWorktreeId
-  const activeWorktree = activeWorktreeId
-    ? findWorktreeById(state.worktreesByRepo, activeWorktreeId)
-    : undefined
-  const activeWorktreeHost = parseExecutionHostId(activeWorktree?.hostId)
-  const activeRepo = activeWorktree
-    ? activeWorktreeHost?.kind === 'local'
-      ? (findRepoForHost(state.repos, activeWorktree.repoId, {
-          hostId: activeWorktreeHost.id
-        }) ?? undefined)
-      : state.repos.find((repo) => repo.id === activeWorktree.repoId)
-    : undefined
-  const sourceControlCanConsumeWatch =
-    !!activeWorktreeId &&
-    !!activeRepo &&
-    isGitRepoKind(activeRepo) &&
-    !state.gitStatusHugeByWorktree[activeWorktreeId] &&
-    (!activeRepo.connectionId ||
-      state.sshConnectionStates.get(activeRepo.connectionId)?.status === 'connected')
-  const activeWorktreeNeedsSidebarWatch =
-    activeWorktreeId !== null &&
-    state.rightSidebarOpen &&
-    ((state.rightSidebarTab === 'explorer' && state.rightSidebarExplorerView === 'files') ||
-      (state.rightSidebarTab === 'source-control' && sourceControlCanConsumeWatch))
-  if (activeWorktreeNeedsSidebarWatch) {
-    // Why: this app-level watcher owns Explorer/Source-Control subscriptions so downstream consumers don't fight over watch/unwatch IPC.
-    let owners = targetOwnersByWorktreeId.get(activeWorktreeId)
-    if (!owners) {
-      owners = new Set()
-      targetOwnersByWorktreeId.set(activeWorktreeId, owners)
-    }
-    // Why: sidebar watcher must follow the selected worktree's host owner, not the host currently focused in the UI.
-    owners.add(getRuntimeEnvironmentIdForWorktree(state, activeWorktreeId))
-  }
-
-  const nextTargets: WatchedTarget[] = []
-  const parts: string[] = []
-  const sortedWorktreeIds = Array.from(targetOwnersByWorktreeId.keys()).sort()
-  for (const id of sortedWorktreeIds) {
-    const wt = findWorktreeById(state.worktreesByRepo, id)
-    const workspaceScope = parseWorkspaceKey(id)
-    const folderWorkspace =
-      workspaceScope?.type === 'folder'
-        ? state.folderWorkspaces.find(
-            (workspace) => workspace.id === workspaceScope.folderWorkspaceId
-          )
-        : undefined
-    if (!wt && !folderWorkspace) {
-      continue
-    }
-    const worktreeHost = parseExecutionHostId(wt?.hostId)
-    const repo = wt
-      ? worktreeHost?.kind === 'local'
-        ? (findRepoForHost(state.repos, wt.repoId, { hostId: worktreeHost.id }) ?? undefined)
-        : state.repos.find((r) => r.id === wt.repoId)
-      : undefined
-    const folderHostId = parseExecutionHostId(folderWorkspace?.executionHostId)?.id
-    const projectGroup = folderWorkspace
-      ? state.projectGroups.find(
-          (group) =>
-            group.id === folderWorkspace.projectGroupId &&
-            parseExecutionHostId(group.executionHostId)?.id === folderHostId
-        )
-      : undefined
-    const connectionId = folderWorkspace
-      ? getFolderWorkspaceConnectionId(state, folderWorkspace.id)
-      : repo
-        ? (repo.connectionId ?? null)
-        : undefined
-    if (connectionId === undefined && folderWorkspace) {
-      continue
-    }
-    const owners = Array.from(targetOwnersByWorktreeId.get(id) ?? []).sort((a, b) =>
-      (a ?? '').localeCompare(b ?? '')
-    )
-    for (const owner of owners) {
-      const target = {
-        worktreeId: id,
-        worktreePath: wt?.path ?? folderWorkspace!.folderPath,
-        connectionId: connectionId ?? undefined,
-        runtimeEnvironmentId: owner,
-        ...(canWatchLocalWindowsWslAliases({
-          worktreePath: wt?.path ?? folderWorkspace!.folderPath,
-          runtimeEnvironmentId: owner,
-          connectionId,
-          worktree: wt,
-          repo,
-          folderWorkspace,
-          projectGroup
-        })
-          ? { allowLocalWindowsWslAliases: true as const }
-          : {})
-      }
-      nextTargets.push(target)
-      parts.push(getWatchedTargetKey(target))
-    }
-  }
-
-  const targetsKey = parts.join('|')
-  cachedOpenFiles = state.openFiles
-  cachedWorktreesByRepo = state.worktreesByRepo
-  cachedRepos = state.repos
-  cachedActiveWorktreeId = state.activeWorktreeId
-  cachedRuntimeEnvironmentId = runtimeEnvironmentId
-  cachedRightSidebarOpen = state.rightSidebarOpen
-  cachedRightSidebarTab = state.rightSidebarTab
-  cachedRightSidebarExplorerView = state.rightSidebarExplorerView
-  cachedGitStatusHugeByWorktree = state.gitStatusHugeByWorktree
-  cachedSshConnectionStates = state.sshConnectionStates
-  cachedFolderWorkspaces = state.folderWorkspaces
-  cachedProjectGroups = state.projectGroups
-
-  if (targetsKey === cachedWatchedTargetsSnapshot.targetsKey) {
-    return cachedWatchedTargetsSnapshot
-  }
-
-  cachedWatchedTargetsSnapshot = { targets: nextTargets, targetsKey }
-  return cachedWatchedTargetsSnapshot
-}
-
-// Why: macOS atomic writes split delete→create across payloads; debounce the 'deleted' signal so a same-path create cancels the tombstone before it paints. Key by owner+path so a local and runtime tab for the same file can't cancel each other's tombstones.
-const EXTERNAL_MUTATION_DEBOUNCE_MS = 75
-
-type PendingDeleteTimer = {
-  fileId: string
-  timer: ReturnType<typeof setTimeout>
-}
-
-/**
- * Subscribes to filesystem watcher events for every worktree that currently
- * has an editor tab open, and notifies the editor to reload clean tabs when
- * their on-disk contents change.
- *
- * Why: the File Explorer watcher unmounts when the sidebar leaves Explorer, so lifting this to an always-mounted hook keeps terminal edits noticed everywhere.
- */
+/** Keeps editor filesystem subscriptions alive beyond any individual editor surface. */
 export function useEditorExternalWatch(): void {
-  const { targets, targetsKey } = useAppStore(getEditorExternalWatchTargets)
-
-  const targetsRef = useRef<WatchedTarget[]>([])
-  const latestTargetsRef = useRef<WatchedTarget[]>(targets)
+  const { targets, targetsKey } = useAppStore(selectEditorExternalWatchTargets)
+  const targetsRef = useRef<EditorExternalWatchTarget[]>([])
+  const latestTargetsRef = useRef<EditorExternalWatchTarget[]>(targets)
   latestTargetsRef.current = targets
   const remoteWatchUnsubsRef = useRef(new Map<string, () => void>())
   const fsChangedHandlerRef = useRef<
     ((payload: FsChangedPayload, runtimeEnvironmentId?: string | null) => void) | null
   >(null)
 
-  // Why: diff prev vs next targets so unchanged worktrees keep their subscription; tearing down all on every targetsKey change churns watchers and drops events in the gap.
+  // Why: diff targets so unchanged worktrees keep their subscription; full teardown on every store change drops events in the gap.
   useEffect(() => {
     const nextTargets = latestTargetsRef.current
-    const prev = targetsRef.current
-    const prevKeys = new Set(prev.map(getWatchedTargetKey))
-    const nextKeys = new Set(nextTargets.map(getWatchedTargetKey))
-    const removed = prev.filter((t) => !nextKeys.has(getWatchedTargetKey(t)))
-    const added = nextTargets.filter((t) => !prevKeys.has(getWatchedTargetKey(t)))
+    const previousTargets = targetsRef.current
+    const previousKeys = new Set(previousTargets.map(getEditorExternalWatchTargetKey))
+    const nextKeys = new Set(nextTargets.map(getEditorExternalWatchTargetKey))
+    const removed = previousTargets.filter(
+      (target) => !nextKeys.has(getEditorExternalWatchTargetKey(target))
+    )
+    const added = nextTargets.filter(
+      (target) => !previousKeys.has(getEditorExternalWatchTargetKey(target))
+    )
 
     for (const target of removed) {
-      const key = getWatchedTargetKey(target)
+      const key = getEditorExternalWatchTargetKey(target)
       const remoteUnsubscribe = remoteWatchUnsubsRef.current.get(key)
       if (remoteUnsubscribe) {
         remoteUnsubscribe()
@@ -379,39 +65,7 @@ export function useEditorExternalWatch(): void {
     }
     for (const target of added) {
       if (target.runtimeEnvironmentId) {
-        const key = getWatchedTargetKey(target)
-        let cancelled = false
-        const pendingUnsubscribe = (): void => {
-          cancelled = true
-        }
-        remoteWatchUnsubsRef.current.set(key, pendingUnsubscribe)
-        void subscribeRuntimeFileChanges(
-          {
-            settings: { activeRuntimeEnvironmentId: target.runtimeEnvironmentId },
-            worktreeId: target.worktreeId,
-            worktreePath: target.worktreePath,
-            connectionId: target.connectionId
-          },
-          (payload) => fsChangedHandlerRef.current?.(payload, target.runtimeEnvironmentId),
-          (err) => warnExternalWatchFailure(target, err)
-        )
-          .then((unsubscribe) => {
-            if (cancelled) {
-              unsubscribe()
-              return
-            }
-            if (remoteWatchUnsubsRef.current.get(key) === pendingUnsubscribe) {
-              remoteWatchUnsubsRef.current.set(key, unsubscribe)
-            } else {
-              unsubscribe()
-            }
-          })
-          .catch((err) => {
-            if (remoteWatchUnsubsRef.current.get(key) === pendingUnsubscribe) {
-              remoteWatchUnsubsRef.current.delete(key)
-            }
-            warnExternalWatchFailure(target, err)
-          })
+        subscribeRuntimeTarget(target, remoteWatchUnsubsRef.current, fsChangedHandlerRef)
         continue
       }
       void window.api.fs
@@ -420,24 +74,24 @@ export function useEditorExternalWatch(): void {
           connectionId: target.connectionId
         })
         .catch((err) => {
-          // Why: remote SSH providers can disappear while tabs still reference the worktree; degrade to a diagnostic, not an uncaught renderer promise.
+          // Why: SSH providers can disappear while tabs still reference the worktree; report the failure without an uncaught renderer promise.
           warnExternalWatchFailure(target, err)
         })
     }
     targetsRef.current = nextTargets
-    // Why: intentionally differential — no unwatch on cleanup; final unmount unwatching lives in the [] effect below so targetsKey changes don't tear down everything.
+    // Why: final unmount cleanup owns teardown so target changes remain differential.
   }, [targetsKey])
 
-  // Why: keep the fs:changed subscription in an always-mounted [] effect so it doesn't re-subscribe on every targetsKey change and miss events fired during the gap.
+  // Why: one stable fs:changed listener prevents target-key changes from opening an event-loss gap.
   useEffect(() => {
     const remoteWatchUnsubs = remoteWatchUnsubsRef.current
-    const { handleFsChanged, dispose } = createExternalWatchEventHandler(
+    const { handleFsChanged, dispose } = buildEditorExternalWatchEventHandler(
       (worktreePath, runtimeEnvironmentId) =>
         targetsRef.current.find(
-          (t) =>
-            normalizeRuntimePathForComparison(t.worktreePath) ===
+          (target) =>
+            normalizeRuntimePathForComparison(target.worktreePath) ===
               normalizeRuntimePathForComparison(worktreePath) &&
-            t.runtimeEnvironmentId === runtimeEnvironmentId
+            target.runtimeEnvironmentId === runtimeEnvironmentId
         )
     )
     const unsubscribe = window.api.fs.onFsChanged((payload) => handleFsChanged(payload, null))
@@ -447,9 +101,8 @@ export function useEditorExternalWatch(): void {
       unsubscribe()
       dispose()
       fsChangedHandlerRef.current = null
-      // Why: the differential watch effect never unwatches on cleanup, so final unmount is the only place that tears down every subscription.
       for (const target of targetsRef.current) {
-        const key = getWatchedTargetKey(target)
+        const key = getEditorExternalWatchTargetKey(target)
         const remoteUnsubscribe = remoteWatchUnsubs.get(key)
         if (remoteUnsubscribe) {
           remoteUnsubscribe()
@@ -462,549 +115,78 @@ export function useEditorExternalWatch(): void {
       }
       remoteWatchUnsubs.clear()
       targetsRef.current = []
-      // Why: don't clear the module-scoped pendingExternalReloadTimers — StrictMode's first-mount cleanup would drop the second mount's timers; a late dispatch is harmless.
+      // Why: module-scoped reload timers survive StrictMode's synthetic cleanup; a late reload dispatch is harmless.
     }
   }, [])
 }
 
-/**
- * Builds the fs:changed handler used by `useEditorExternalWatch`. Exported so
- * tests can drive the full event pipeline (including the tombstone coalescer)
- * without mounting the hook.
- */
-export function createExternalWatchEventHandler(
-  findTarget: (
-    worktreePath: string,
-    runtimeEnvironmentId: string | null
-  ) => WatchedTarget | undefined
-): {
-  handleFsChanged: (payload: FsChangedPayload, runtimeEnvironmentId?: string | null) => void
-  dispose: () => void
-} {
-  // Why: coalesce 'deleted' tombstones so a same-path create cancels them before the tab flashes (macOS atomic write). See EXTERNAL_MUTATION_DEBOUNCE_MS.
-  const pendingDeletes = new Map<string, PendingDeleteTimer>()
-  const pendingKey = (
-    worktreeId: string,
-    runtimeEnvironmentId: string | null,
-    absolutePath: string
-  ): string => `${worktreeId}::${runtimeEnvironmentId ?? 'client'}::${absolutePath}`
-
-  const handleFsChanged = (
-    payload: FsChangedPayload,
-    runtimeEnvironmentId: string | null = null
-  ): void => {
-    const target = findTarget(payload.worktreePath, runtimeEnvironmentId)
-    if (!target) {
-      return
-    }
-    // Why: this app-level hook owns watcher subscriptions; other consumers listen here so they don't fight over watch/unwatch ownership.
-    if (typeof window !== 'undefined' && typeof window.dispatchEvent === 'function') {
-      window.dispatchEvent(
-        new CustomEvent<WorktreeFileChangeEventDetail>(ORCA_WORKTREE_FILE_CHANGE_EVENT, {
-          detail: { payload, runtimeEnvironmentId: target.runtimeEnvironmentId }
-        })
-      )
-    }
-
-    // Why: one batch index keeps local WSL alias normalization out of event×tab loops.
-    const openFilesAtStart = useAppStore.getState().openFiles
-    const batchPaths = indexEditorExternalWatchBatchPaths(payload, openFilesAtStart, {
+function subscribeRuntimeTarget(
+  target: EditorExternalWatchTarget,
+  remoteWatchUnsubs: Map<string, () => void>,
+  fsChangedHandlerRef: {
+    current: ((payload: FsChangedPayload, runtimeEnvironmentId?: string | null) => void) | null
+  }
+): void {
+  const key = getEditorExternalWatchTargetKey(target)
+  let cancelled = false
+  const pendingUnsubscribe = (): void => {
+    cancelled = true
+  }
+  remoteWatchUnsubs.set(key, pendingUnsubscribe)
+  void subscribeRuntimeFileChanges(
+    {
+      settings: { activeRuntimeEnvironmentId: target.runtimeEnvironmentId! },
       worktreeId: target.worktreeId,
       worktreePath: target.worktreePath,
-      runtimeEnvironmentId: target.runtimeEnvironmentId,
-      ...localWslAliasOption(target)
-    })
-    const createOrUpdatePaths = batchPaths.createOrUpdatePaths
-    for (const createdPath of createOrUpdatePaths.keys()) {
-      const key = pendingKey(target.worktreeId, target.runtimeEnvironmentId, createdPath)
-      const existing = pendingDeletes.get(key)
-      if (existing) {
-        clearTimeout(existing.timer)
-        pendingDeletes.delete(key)
+      connectionId: target.connectionId
+    },
+    (payload) => fsChangedHandlerRef.current?.(payload, target.runtimeEnvironmentId),
+    (err) => warnExternalWatchFailure(target, err)
+  )
+    .then((unsubscribe) => {
+      if (cancelled) {
+        unsubscribe()
+        return
       }
-    }
-
-    // Why: mark editor tabs deleted/renamed instead of closing them so the user keeps in-memory content; a paired create means rename, a lone delete is hard.
-    // Why: snapshot openFiles once so delete, rename, and update matching share one indexed view.
-    const deletedOpenEditorsRaw = batchPaths.deletedOpenEditors
-    // Only pay the per-id lookup to suppress a move's own source-delete while a move is live; else the batch stays O(deletes).
-    const deletedOpenEditors = hasActiveEditorPathMoves()
-      ? deletedOpenEditorsRaw.filter(
-          ({ file }) =>
-            !isActiveMoveSourcePath(target.worktreeId, target.runtimeEnvironmentId, file.filePath)
-        )
-      : deletedOpenEditorsRaw
-    const deletedOpenEditorIds = deletedOpenEditors.map(({ file }) => file.id)
-    // Why: correlate creates to deletes by basename to avoid mislabelling unrelated create+delete pairs as "renamed"; default to 'deleted' when we can't correlate.
-    const hasPairedCreate =
-      deletedOpenEditorIds.length > 0 &&
-      hasRenameCorrelatedCreate(payload, target.worktreeId, deletedOpenEditorIds, openFilesAtStart)
-    if (deletedOpenEditorIds.length > 0) {
-      if (hasPairedCreate) {
-        // Why: single-payload delete+create is already correct in one render tick, so no debounce needed.
-        const setExternalMutation = useAppStore.getState().setExternalMutation
-        for (const fileId of deletedOpenEditorIds) {
-          setExternalMutation(fileId, 'renamed')
-        }
+      if (remoteWatchUnsubs.get(key) === pendingUnsubscribe) {
+        remoteWatchUnsubs.set(key, unsubscribe)
       } else {
-        // Why: defer the 'deleted' tombstone so a follow-up same-path create in the next payload can cancel it (macOS atomic write).
-        for (const { file, normalizedDeletePath } of deletedOpenEditors) {
-          const fileId = file.id
-          const absolutePath = normalizedDeletePath
-          const key = pendingKey(target.worktreeId, target.runtimeEnvironmentId, absolutePath)
-          const existing = pendingDeletes.get(key)
-          if (existing) {
-            clearTimeout(existing.timer)
-            pendingDeletes.delete(key)
-          }
-          const timer = setTimeout(() => {
-            pendingDeletes.delete(key)
-            // Why: the debounce window lets the tab close or leave edit mode, so re-check before writing to avoid tombstoning a dropped or non-edit tab.
-            const state = useAppStore.getState()
-            const stillEditing = state.openFiles.some((f) => f.id === fileId && f.mode === 'edit')
-            if (stillEditing) {
-              state.setExternalMutation(fileId, 'deleted')
-            }
-          }, EXTERNAL_MUTATION_DEBOUNCE_MS)
-          pendingDeletes.set(key, { fileId, timer })
-        }
-      }
-    }
-
-    // Why: a reappearing file (e.g. `git checkout`) clears its deleted/renamed tombstone — but not a 'changed' mark, which resolves via reload/save instead.
-    if (createOrUpdatePaths.size > 0) {
-      const state = useAppStore.getState()
-      for (const file of state.openFiles) {
-        if (
-          file.worktreeId === target.worktreeId &&
-          openFileRuntimeOwner(file) === target.runtimeEnvironmentId &&
-          (file.mode === 'edit' || file.mode === 'markdown-preview') &&
-          (file.externalMutation === 'deleted' || file.externalMutation === 'renamed') &&
-          batchPaths.matchesCreateOrUpdate(file)
-        ) {
-          state.setExternalMutation(file.id, null)
-        }
-      }
-    }
-
-    let overflowed = false
-    for (const evt of payload.events) {
-      if (evt.kind === 'overflow') {
-        // Why: overflow omits per-path info, so conservatively clear stale tombstones or a file that reappeared during the overrun stays struck through.
-        for (const notification of getOverflowExternalReloadTargets(target)) {
-          scheduleDebouncedExternalReload(notification)
-        }
-        overflowed = true
-        break
-      }
-    }
-
-    if (overflowed || batchPaths.changes.length === 0) {
-      return
-    }
-
-    for (const change of batchPaths.changes) {
-      const relativePath = change.relativePath
-      const matching = batchPaths.matchingOpenFiles(change)
-      const notification = {
-        worktreeId: target.worktreeId,
-        worktreePath: target.worktreePath,
-        relativePath,
-        runtimeEnvironmentId: target.runtimeEnvironmentId,
-        ...localWslAliasOption(target)
-      }
-      Object.defineProperty(notification, 'indexedOpenFiles', {
-        value: {
-          matches: (openFiles: OpenFile[]) => batchPaths.matchingOpenFiles(change, openFiles)
-        }
-      })
-      const absolutePath = change.absolutePath
-      if (matching.length === 0) {
-        // Why: combined-diff tab has no in-memory content to clobber and guards its own reload, so notify it directly without self-write suppression.
-        if (batchPaths.hasCombinedDiffConsumer) {
-          scheduleDebouncedExternalReload(notification)
-        }
-        continue
-      }
-      const dirtyMatches = matching.filter((f) => f.isDirty)
-      if (dirtyMatches.length > 0) {
-        // canAutoSaveOpenFile is the set of tabs that can hold unsaved edits — the tabs the banner serves.
-        const dirtyIds = dirtyMatches.filter((f) => canAutoSaveOpenFile(f)).map((f) => f.id)
-        // A tab carrying move-echo provenance for this path may just be seeing the move's own echo; settle by
-        // disk identity below. Only a provenance-carrying tab can match, so skip the normalize when none has it.
-        let isSelfMoveEcho = false
-        if (dirtyMatches.some((f) => f.pendingSelfMoveEcho)) {
-          const normalizedAbsolutePath = normalizeRuntimePathForComparison(absolutePath)
-          isSelfMoveEcho = dirtyMatches.some(
-            (f) =>
-              f.pendingSelfMoveEcho &&
-              normalizeRuntimePathForComparison(f.pendingSelfMoveEcho.targetPath) ===
-                normalizedAbsolutePath
-          )
-        }
-        if (isSelfMoveEcho) {
-          // Real destination fs event confirms the echo — consume the provenance so a later genuine write takes the normal path.
-          scheduleSelfMoveEchoVerification(target, dirtyIds, true)
-        } else {
-          // An external write on a dirty tab must not vanish silently (issue #7265); mark it for the reload banner.
-          scheduleChangedOnDiskMark(target, notification, dirtyIds)
-        }
-        if (dirtyMatches.length === matching.length) {
-          if (batchPaths.hasCombinedDiffConsumer) {
-            scheduleDebouncedExternalReload(notification)
-          }
-          continue
-        }
-        // Clean sibling tabs (e.g. an unstaged diff of the same path) still reload below; consumers skip dirty files.
-      }
-      const recentSelfWrite = getRecentSelfWrite(absolutePath, target.runtimeEnvironmentId)
-      if (recentSelfWrite) {
-        scheduleSelfWriteAwareExternalReload(target, notification, matching[0], recentSelfWrite)
-        continue
-      }
-      scheduleDebouncedExternalReload(notification)
-    }
-  }
-
-  const dispose = (): void => {
-    // Why: clear in-flight tombstone timers so they don't fire after disposal and touch a stale store.
-    for (const pending of pendingDeletes.values()) {
-      clearTimeout(pending.timer)
-    }
-    pendingDeletes.clear()
-  }
-
-  return { handleFsChanged, dispose }
-}
-
-const inFlightEchoVerificationReads = new Map<string, ReturnType<typeof readRuntimeFileContent>>()
-
-// Why: one save echo can arrive as a burst of payloads; share the in-flight full-file read so concurrent payloads for the same file don't stack duplicate reads.
-function readFileForEchoVerification(args: {
-  runtimeEnvironmentId: string | null | undefined
-  filePath: string
-  relativePath: string
-  worktreeId: string | null | undefined
-  connectionId: string | undefined
-  expectedExternalSshTargetId?: string
-}): ReturnType<typeof readRuntimeFileContent> {
-  const key = [
-    args.runtimeEnvironmentId ?? '',
-    args.connectionId ?? '',
-    args.expectedExternalSshTargetId ?? '',
-    args.filePath
-  ].join('::')
-  let pending = inFlightEchoVerificationReads.get(key)
-  if (!pending) {
-    pending = readRuntimeFileContent({
-      settings: args.runtimeEnvironmentId
-        ? { activeRuntimeEnvironmentId: args.runtimeEnvironmentId }
-        : null,
-      filePath: args.filePath,
-      relativePath: args.relativePath,
-      worktreeId: args.worktreeId ?? undefined,
-      connectionId: args.connectionId,
-      expectedExternalSshTargetId: args.expectedExternalSshTargetId
-    })
-    inFlightEchoVerificationReads.set(key, pending)
-    const release = (): void => {
-      if (inFlightEchoVerificationReads.get(key) === pending) {
-        inFlightEchoVerificationReads.delete(key)
-      }
-    }
-    pending.then(release, release)
-  }
-  return pending
-}
-
-function markTabsChangedOnDisk(fileIds: string[], connectionId: string | undefined): void {
-  const state = useAppStore.getState()
-  for (const fileId of fileIds) {
-    const file = state.openFiles.find((f) => f.id === fileId)
-    // Why: echo verification resolves async — the tab may have been closed since, so only mark files still open.
-    if (file) {
-      markFileChangedOnDisk(state, file, { connectionId, origin: 'live' })
-    }
-  }
-}
-
-function scheduleChangedOnDiskMark(
-  target: WatchedTarget,
-  notification: ExternalWatchNotification,
-  fileIds: string[]
-): void {
-  if (fileIds.length === 0) {
-    return
-  }
-  const absolutePath = joinPath(notification.worktreePath, notification.relativePath)
-  const recentSelfWrite = getRecentSelfWrite(absolutePath, target.runtimeEnvironmentId)
-  // Why: the fs event may be the echo of Orca's own save — verify disk really differs from our last write before showing a "changed on disk" banner.
-  if (!recentSelfWrite || recentSelfWrite.content === null) {
-    markTabsChangedOnDisk(fileIds, target.connectionId)
-    return
-  }
-  void readFileForEchoVerification({
-    runtimeEnvironmentId: target.runtimeEnvironmentId,
-    filePath: absolutePath,
-    relativePath: notification.relativePath,
-    worktreeId: notification.worktreeId,
-    connectionId: target.connectionId
-  })
-    .then((result) => {
-      if (result.isBinary || result.content !== recentSelfWrite.content) {
-        markTabsChangedOnDisk(fileIds, target.connectionId)
+        unsubscribe()
       }
     })
-    .catch(() => {
-      // Why: unreadable disk state can't disprove an external change — keep the conflict visible rather than risk a silent overwrite.
-      markTabsChangedOnDisk(fileIds, target.connectionId)
+    .catch((err) => {
+      if (remoteWatchUnsubs.get(key) === pendingUnsubscribe) {
+        remoteWatchUnsubs.delete(key)
+      }
+      warnExternalWatchFailure(target, err)
     })
 }
 
-// Per-file generation so a newer echo-verify read supersedes an older one — overlapping reads can't clear each other's autosave gate or apply a stale verdict.
-const liveMoveVerifyGeneration = new Map<string, number>()
-let liveMoveVerifyCounter = 0
-
-type LiveMoveVerifyCandidate = {
-  fileId: string
-  baseline: string | undefined
-  generation: number
-  /** The move that installed the provenance; a newer move re-homing the tab supersedes this verification, even across a rekey. */
-  operationId?: string
+// Compatibility delegates keep existing direct imports stable without turning this module into an export barrel.
+export function getWatchedTargetKey(target: EditorExternalWatchTarget): string {
+  return getEditorExternalWatchTargetKey(target)
 }
 
-// Resolve one candidate against the disk read (`diskSignature` null = binary/unreadable).
-// Fails CLOSED: anything but a proven baseline match surfaces the conflict, so a real external write is never swallowed.
-function resolveLiveMoveVerification(
-  candidate: LiveMoveVerifyCandidate,
-  diskSignature: string | null,
-  connectionId: string | undefined,
-  consumeProvenance: boolean
-): void {
-  const { fileId, baseline, generation, operationId } = candidate
-  if (liveMoveVerifyGeneration.get(fileId) !== generation) {
-    return // a newer verification owns this tab and its autosave gate
-  }
-  liveMoveVerifyGeneration.delete(fileId)
-  const state = useAppStore.getState()
-  state.setPendingLiveDiskVerification(fileId, false)
-  const file = state.openFiles.find((f) => f.id === fileId)
-  // Skip if the interim moved on: tab resolved, baseline advanced, or a different move replaced the provenance we captured.
-  if (
-    !file ||
-    !file.isDirty ||
-    file.externalMutation === 'changed' ||
-    file.lastKnownDiskSignature !== baseline ||
-    (operationId !== undefined && file.pendingSelfMoveEcho?.operationId !== operationId)
-  ) {
-    return
-  }
-  // Consume only when a real watcher event drove this check. The proactive post-commit verify must LEAVE the provenance,
-  // else the destination fs event (on FSEvents/SSH it lands after the faster local read) would raise a false conflict banner.
-  if (consumeProvenance) {
-    state.clearSelfMoveEcho(fileId)
-  }
-  const isMoveEcho = baseline !== undefined && diskSignature === baseline
-  if (!isMoveEcho) {
-    markFileChangedOnDisk(state, file, { connectionId, origin: 'live' })
-  }
+export function getEditorExternalWatchTargets(
+  state: EditorExternalWatchTargetState
+): ReturnType<typeof selectEditorExternalWatchTargets> {
+  return selectEditorExternalWatchTargets(state)
+}
+
+export function createExternalWatchEventHandler(
+  ...args: Parameters<typeof buildEditorExternalWatchEventHandler>
+): ReturnType<typeof buildEditorExternalWatchEventHandler> {
+  return buildEditorExternalWatchEventHandler(...args)
 }
 
-/**
- * Verify tabs whose destination echo was LATCHED before the rekey installed them: the coordinator calls this
- * after a successful move so a pre-rekey event isn't lost and the autosave gate can't strand.
- */
 export function verifyLatchedMoveDestinations(
-  worktreePath: string,
-  connectionId: string | undefined,
-  fileIds: readonly string[]
+  ...args: Parameters<typeof verifyLatchedEditorMoveDestinations>
 ): void {
-  const state = useAppStore.getState()
-  const gated = fileIds.filter(
-    (id) => state.openFiles.find((f) => f.id === id)?.pendingSelfMoveEcho
-  )
-  if (gated.length === 0) {
-    return
-  }
-  // consumeProvenance:false — safety net; leave the provenance so a destination watcher event after this read still reads as an echo.
-  // (Owner/worktree are resolved per-tab inside the read; worktreePath is unused, each tab reads at its own filePath.)
-  scheduleSelfMoveEchoVerification(
-    { worktreeId: '', worktreePath, connectionId, runtimeEnvironmentId: null },
-    gated,
-    false
-  )
-}
-
-// Settle each dirty tab by content identity: the move's own echo leaves disk == the tab's baseline, a genuine external write does not.
-// Autosave is suspended synchronously first so a write landing mid-read can't be overwritten before we decide.
-function scheduleSelfMoveEchoVerification(
-  target: WatchedTarget,
-  fileIds: string[],
-  consumeProvenance: boolean
-): void {
-  if (fileIds.length === 0) {
-    return
-  }
-  const state = useAppStore.getState()
-  for (const fileId of fileIds) {
-    const file = state.openFiles.find((f) => f.id === fileId)
-    if (!file || !file.isDirty || file.externalMutation === 'changed') {
-      continue
-    }
-    const generation = ++liveMoveVerifyCounter
-    liveMoveVerifyGeneration.set(fileId, generation)
-    state.setPendingLiveDiskVerification(fileId, true)
-    const candidate: LiveMoveVerifyCandidate = {
-      fileId,
-      baseline: file.lastKnownDiskSignature,
-      generation,
-      operationId: file.pendingSelfMoveEcho?.operationId
-    }
-    // Read the tab's OWN absolute path: a cross-worktree/floating tab's relativePath is relative to its own root (can be `../…`),
-    // never join it onto another worktree's path. readFileForEchoVerification dedups concurrent same-path reads, so siblings share one.
-    void readFileForEchoVerification({
-      runtimeEnvironmentId: file.runtimeEnvironmentId?.trim() || target.runtimeEnvironmentId,
-      filePath: file.filePath,
-      relativePath: file.relativePath,
-      worktreeId: file.worktreeId,
-      connectionId: target.connectionId,
-      expectedExternalSshTargetId: file.externalSshTargetId
-    })
-      .then((result) => {
-        const diskSignature = result.isBinary ? null : getDiskBaselineSignature(result.content)
-        resolveLiveMoveVerification(
-          candidate,
-          diskSignature,
-          target.connectionId,
-          consumeProvenance
-        )
-      })
-      .catch(() =>
-        resolveLiveMoveVerification(candidate, null, target.connectionId, consumeProvenance)
-      )
-  }
-}
-
-function scheduleSelfWriteAwareExternalReload(
-  target: WatchedTarget,
-  notification: ExternalWatchNotification,
-  file: OpenFile,
-  recentSelfWrite: RecentSelfWrite
-): void {
-  if (recentSelfWrite.content === null) {
-    scheduleDebouncedExternalReload(notification)
-    return
-  }
-
-  const runtimeEnvironmentId = file.runtimeEnvironmentId ?? target.runtimeEnvironmentId
-  // Why: a self-write stamp only proves recent change; compare disk content so we suppress only Orca's own echo, not a newer agent write in the same TTL.
-  void readFileForEchoVerification({
-    runtimeEnvironmentId,
-    filePath: file.filePath,
-    relativePath: file.relativePath,
-    worktreeId: file.worktreeId,
-    connectionId: target.connectionId,
-    expectedExternalSshTargetId: file.externalSshTargetId
-  })
-    .then((result) => {
-      if (
-        (result.isBinary || result.content !== recentSelfWrite.content) &&
-        hasCleanExternalReloadTarget(notification)
-      ) {
-        clearSelfWrite(file.filePath, runtimeEnvironmentId)
-        scheduleDebouncedExternalReload(notification)
-      }
-    })
-    .catch(() => {
-      if (hasCleanExternalReloadTarget(notification)) {
-        clearSelfWrite(file.filePath, runtimeEnvironmentId)
-        scheduleDebouncedExternalReload(notification)
-      }
-    })
-}
-
-function hasCleanExternalReloadTarget(notification: ExternalWatchNotification): boolean {
-  const matching = getOpenFilesForExternalFileChange(useAppStore.getState().openFiles, notification)
-  // Why: one clean target is enough — consumers skip dirty files per-file, so a dirty sibling doesn't veto the reload.
-  return matching.some((file) => !file.isDirty)
+  verifyLatchedEditorMoveDestinations(...args)
 }
 
 export function getOverflowExternalReloadTargets(
-  target: Pick<WatchedTarget, 'worktreeId' | 'worktreePath'> & {
-    connectionId?: string
-    runtimeEnvironmentId?: string | null
-    allowLocalWindowsWslAliases?: true
-  }
-): ExternalWatchNotification[] {
-  const state = useAppStore.getState()
-  const notifications: ExternalWatchNotification[] = []
-
-  for (const file of state.openFiles) {
-    if (
-      file.worktreeId !== target.worktreeId ||
-      openFileRuntimeOwner(file) !== (target.runtimeEnvironmentId ?? null) ||
-      !isExternalReloadableEditorTab(file) ||
-      file.isDirty
-    ) {
-      continue
-    }
-    if (file.externalMutation) {
-      // Why: overflow gives no per-path resurrection signal, so clear the tombstone and let a still-missing file surface as a read failure.
-      state.setExternalMutation(file.id, null)
-    }
-    notifications.push({
-      worktreeId: target.worktreeId,
-      worktreePath: target.worktreePath,
-      relativePath: file.relativePath,
-      runtimeEnvironmentId: target.runtimeEnvironmentId ?? null,
-      ...localWslAliasOption({
-        allowLocalWindowsWslAliases: target.allowLocalWindowsWslAliases
-      })
-    })
-  }
-
-  return notifications
-}
-
-/**
- * Returns true if the batched payload contains at least one file-create event
- * whose basename matches a deleted open editor file.
- *
- * Why: correlate by basename only, not parent dir — save-as-temp patterns (`rm foo.md && touch foo.md.new`) put unrelated creates in the same dir and would mislabel deletes as renames.
- */
-function hasRenameCorrelatedCreate(
-  payload: FsChangedPayload,
-  worktreeId: string,
-  deletedOpenEditorIds: string[],
-  openFiles: OpenFile[]
-): boolean {
-  if (deletedOpenEditorIds.length === 0) {
-    return false
-  }
-  const deletedIdSet = new Set(deletedOpenEditorIds)
-  const deletedBasenames = new Set<string>()
-  for (const file of openFiles) {
-    if (
-      file.worktreeId !== worktreeId ||
-      (file.mode !== 'edit' && file.mode !== 'markdown-preview')
-    ) {
-      continue
-    }
-    if (!deletedIdSet.has(file.id)) {
-      continue
-    }
-    deletedBasenames.add(basename(file.filePath))
-  }
-  if (deletedBasenames.size === 0) {
-    return false
-  }
-  for (const evt of payload.events) {
-    if (evt.kind !== 'create' || evt.isDirectory === true) {
-      continue
-    }
-    if (deletedBasenames.has(basename(evt.absolutePath))) {
-      return true
-    }
-  }
-  return false
+  ...args: Parameters<typeof collectOverflowEditorExternalReloadTargets>
+): ReturnType<typeof collectOverflowEditorExternalReloadTargets> {
+  return collectOverflowEditorExternalReloadTargets(...args)
 }