diff --git a/memento-note/app/api/ai/convert-markdown/route.ts b/memento-note/app/api/ai/convert-markdown/route.ts
new file mode 100644
index 0000000..0e8e5b6
--- /dev/null
+++ b/memento-note/app/api/ai/convert-markdown/route.ts
@@ -0,0 +1,22 @@
+import { NextRequest, NextResponse } from 'next/server'
+import { auth } from '@/auth'
+import { markdownToHtml } from '@/lib/markdown-to-html'
+
+export async function POST(request: NextRequest) {
+  try {
+    const session = await auth()
+    if (!session?.user?.id) {
+      return NextResponse.json({ error: 'Unauthorized' }, { status: 401 })
+    }
+
+    const { content } = await request.json()
+    if (!content || typeof content !== 'string') {
+      return NextResponse.json({ error: 'Content is required' }, { status: 400 })
+    }
+
+    const html = markdownToHtml(content)
+    return NextResponse.json({ html })
+  } catch (error: any) {
+    return NextResponse.json({ error: error.message || 'Conversion failed' }, { status: 500 })
+  }
+}
diff --git a/memento-note/components/note-inline-editor.tsx b/memento-note/components/note-inline-editor.tsx
index 79f051a..b09c4e8 100644
--- a/memento-note/components/note-inline-editor.tsx
+++ b/memento-note/components/note-inline-editor.tsx
@@ -495,10 +495,36 @@ export function NoteInlineEditor({
 
           <NoteTypeSelector
             value={noteType}
-            onChange={(newType) => {
+            onChange={async (newType) => {
+              const oldType = noteType
               setNoteType(newType)
               if (newType === 'markdown') setShowMarkdownPreview(true)
               else setShowMarkdownPreview(false)
+
+              // When switching from markdown to richtext, convert content to HTML
+              if (oldType === 'markdown' && newType === 'richtext') {
+                try {
+                  const res = await fetch('/api/ai/convert-markdown', {
+                    method: 'POST',
+                    headers: { 'Content-Type': 'application/json' },
+                    body: JSON.stringify({ content }),
+                  })
+                  if (res.ok) {
+                    const { html } = await res.json()
+                    setContent(html)
+                    saveInline(note.id, {
+                      type: 'richtext',
+                      isMarkdown: false,
+                      content: html,
+                    }).catch(() => {})
+                    onChange?.(note.id, { type: 'richtext', isMarkdown: false, content: html })
+                    return
+                  }
+                } catch {
+                  // Fall through to save without conversion
+                }
+              }
+
               // Persist both type and isMarkdown immediately
               saveInline(note.id, {
                 type: newType,
diff --git a/memento-note/lib/ai/services/agent-executor.service.ts b/memento-note/lib/ai/services/agent-executor.service.ts
index 02122ef..0ffe7eb 100644
--- a/memento-note/lib/ai/services/agent-executor.service.ts
+++ b/memento-note/lib/ai/services/agent-executor.service.ts
@@ -43,13 +43,12 @@ async function createAgentNote(data: {
   notebookId: string | null
   autoGenerated?: boolean
 }) {
-  const htmlContent = markdownToHtml(data.content)
   return prisma.note.create({
     data: {
       title: data.title,
-      content: htmlContent,
-      type: 'richtext',
-      isMarkdown: false,
+      content: data.content,
+      type: 'markdown',
+      isMarkdown: true,
       autoGenerated: data.autoGenerated ?? true,
       userId: data.userId,
       notebookId: data.notebookId,
diff --git a/memento-note/lib/ai/tools/note-crud.tool.ts b/memento-note/lib/ai/tools/note-crud.tool.ts
index 9bfd450..3bffc71 100644
--- a/memento-note/lib/ai/tools/note-crud.tool.ts
+++ b/memento-note/lib/ai/tools/note-crud.tool.ts
@@ -51,13 +51,12 @@ toolRegistry.register({
       }),
       execute: async ({ title, content, notebookId, images }) => {
         try {
-          const htmlContent = markdownToHtml(content)
           const note = await prisma.note.create({
             data: {
               title,
-              content: htmlContent,
-              type: 'richtext',
-              isMarkdown: false,
+              content,
+              type: 'markdown',
+              isMarkdown: true,
               autoGenerated: true,
               userId: ctx.userId,
               notebookId: notebookId || null,