fix(files): lock the markdown round-trip verdict on opened content, never strand dirty edits

The round-trip-safety verdict now gates editability only at open time — computed once, on the exact
content the editor mounts with, and locked for its lifetime. A dirty document is round-trip-safe by
construction (the editor only emits safe markdown), so the verdict must never flip off mid-edit:
doing so disabled autosave, ⌘S, the toolbar Save and the unmount flush, stranding unsaved edits.
Locking on the opened (reconciled) content also fixes the stale post-stream empty-buffer snapshot,
and lets the redundant MarkdownFileEditor gate (plus its duplicate content fetch) be deleted.

Author: waleedlatif1

apps/sim/app/workspace/[workspaceId]/files/components/file-viewer/file-viewer.tsx

@@ -32,8 +32,8 @@ const PdfViewerCore = dynamic(() => import('./pdf-viewer').then((m) => m.PdfView
   ssr: false,
 })
 
-const MarkdownFileEditor = dynamic(
-  () => import('./rich-markdown-editor/markdown-file-editor').then((m) => m.MarkdownFileEditor),
+const RichMarkdownEditor = dynamic(
+  () => import('./rich-markdown-editor/rich-markdown-editor').then((m) => m.RichMarkdownEditor),
   { ssr: false, loading: () => <PreviewLoadingFrame className='flex flex-1 flex-col' /> }
 )
 
@@ -130,7 +130,7 @@ export function FileViewer({
       // the bubble menu, and every other editing affordance.
       if (isMarkdownFile(file)) {
         return (
-          <MarkdownFileEditor key={file.id} file={file} workspaceId={workspaceId} canEdit={false} />
+          <RichMarkdownEditor key={file.id} file={file} workspaceId={workspaceId} canEdit={false} />
         )
       }
       return <ReadOnlyTextPreview file={file} workspaceId={workspaceId} />
@@ -143,7 +143,7 @@ export function FileViewer({
 
     if (isMarkdownFile(file)) {
       return (
-        <MarkdownFileEditor
+        <RichMarkdownEditor
           key={file.id}
           file={file}
           workspaceId={workspaceId}

apps/sim/app/workspace/[workspaceId]/files/components/file-viewer/rich-markdown-editor/markdown-file-editor.tsx

@@ -20,6 +20,7 @@ import {
   splitFrontmatter,
 } from './markdown-fidelity'
 import { EditorBubbleMenu } from './menus/bubble-menu'
+import { isRoundTripSafe } from './round-trip-safety'
 import '@/components/emcn/components/code/code.css'
 import './rich-markdown-editor.css'
 
@@ -116,7 +117,7 @@ export const RichMarkdownEditor = memo(function RichMarkdownEditor({
       file={file}
       workspaceId={workspaceId}
       initialContent={content}
-      isEditable={canEdit}
+      canEdit={canEdit}
       autoFocus={autoFocus}
       onChange={setDraftContent}
       onSaveShortcut={saveImmediately}
@@ -128,7 +129,7 @@ interface LoadedRichMarkdownEditorProps {
   file: WorkspaceFileRecord
   workspaceId: string
   initialContent: string
-  isEditable: boolean
+  canEdit: boolean
   autoFocus?: boolean
   onChange: (markdown: string) => void
   onSaveShortcut: () => Promise<void>
@@ -144,11 +145,24 @@ function LoadedRichMarkdownEditor({
   file,
   workspaceId,
   initialContent,
-  isEditable,
+  canEdit,
   autoFocus,
   onChange,
   onSaveShortcut,
 }: LoadedRichMarkdownEditorProps) {
+  // Whether the opened content round-trips losslessly through the editor — computed once, on the
+  // exact content the editor opens with (keyed by file id, so it remounts per file), and locked for
+  // the editor's lifetime. A round-trip-unsafe document (raw HTML, footnotes, >128KB, …) opens
+  // read-only so an edit can't corrupt it; a safe one stays editable. It is never re-derived: a
+  // dirty document is round-trip-safe by construction (the editor only emits safe markdown), so
+  // flipping editability off mid-edit would only strand unsaved edits (autosave, ⌘S, the toolbar
+  // Save, and the unmount flush all gate on it).
+  const roundTripSafeRef = useRef<boolean | null>(null)
+  if (roundTripSafeRef.current === null) {
+    roundTripSafeRef.current = isRoundTripSafe(initialContent)
+  }
+  const isEditable = canEdit && roundTripSafeRef.current
+
   const { frontmatter, body } = useMemo(() => splitFrontmatter(initialContent), [initialContent])
   const frontmatterRef = useRef(frontmatter)
   frontmatterRef.current = frontmatter