diff --git a/src/web/components/browser.ts b/src/web/components/browser.ts
index 21567f0..d9452d7 100644
--- a/src/web/components/browser.ts
+++ b/src/web/components/browser.ts
@@ -175,6 +175,24 @@ export function renderRecordList(
   `
 }
 
+// Check if a record needs migration to new format
+function needsMigration(value: unknown, collection: string): boolean {
+  if (!value || typeof value !== 'object') return false
+  const v = value as Record<string, unknown>
+
+  // Only for ai.syui.log.post and ai.syui.log.chat
+  if (!collection.startsWith('ai.syui.log.')) return false
+
+  // Check: content is a string (old) instead of object (new)
+  if (typeof v.content === 'string') return true
+  // Check: has createdAt but no publishedAt
+  if (v.createdAt && !v.publishedAt) return true
+  // Check: missing site field
+  if (!v.site) return true
+
+  return false
+}
+
 // Render single record detail
 export function renderRecordDetail(
   record: { uri: string; cid: string; value: unknown },
@@ -186,12 +204,18 @@ export function renderRecordDetail(
     <button type="button" class="record-delete-btn" id="record-delete-btn" data-collection="${collection}" data-rkey="${rkey}">Delete</button>
   ` : ''
 
+  const showMerge = isOwner && needsMigration(record.value, collection)
+  const mergeBtn = showMerge ? `
+    <button type="button" class="record-merge-btn" id="record-merge-btn" data-collection="${collection}" data-rkey="${rkey}">Merge</button>
+  ` : ''
+
   return `
     <article class="record-detail">
       <header class="record-header">
         <div class="record-header-top">
           <h3>${collection}</h3>
           <button type="button" class="validate-btn" id="validate-btn" data-collection="${collection}">Validate</button>
+          ${mergeBtn}
         </div>
         <p class="record-uri">URI: ${record.uri}</p>
         <p class="record-cid">CID: ${record.cid}</p>
diff --git a/src/web/components/posts.ts b/src/web/components/posts.ts
index 50da3be..1ff5882 100644
--- a/src/web/components/posts.ts
+++ b/src/web/components/posts.ts
@@ -3,6 +3,17 @@ import { renderMarkdown } from '../lib/markdown'
 import { renderDiscussion, loadDiscussionPosts } from './discussion'
 import { getCurrentLang } from './mode-tabs'
 
+// Extract text content from post content (handles both string and object formats)
+function getContentText(content: unknown): string {
+  if (!content) return ''
+  if (typeof content === 'string') return content
+  if (typeof content === 'object' && content !== null) {
+    const obj = content as Record<string, unknown>
+    if (typeof obj.text === 'string') return obj.text
+  }
+  return ''
+}
+
 // Format date as yyyy/mm/dd
 function formatDate(dateStr: string): string {
   const d = new Date(dateStr)
@@ -61,6 +72,8 @@ export function renderPostDetail(
   // Build post URL for discussion search
   const postUrl = siteUrl ? `${siteUrl}/@${handle}/${rkey}` : `${window.location.origin}/@${handle}/${rkey}`
 
+  const rawContent = getContentText(post.value.content)
+
   const editBtn = isOwner ? `<button type="button" class="post-edit-btn" id="post-edit-btn">Edit</button>` : ''
 
   // Get current language and show appropriate content
@@ -68,22 +81,22 @@ export function renderPostDetail(
   const translations = post.value.translations
   const originalLang = post.value.langs?.[0] || 'ja'
 
-  let displayTitle = post.value.title
-  let displayContent = post.value.content.text
+  let displayTitle = post.value.title || ''
+  let displayContent = rawContent
 
   // Use translation if available and not original language
   if (translations && currentLang !== originalLang && translations[currentLang]) {
     const trans = translations[currentLang]
-    displayTitle = trans.title || post.value.title
-    displayContent = trans.content
+    displayTitle = trans.title || post.value.title || ''
+    displayContent = trans.content || rawContent
   }
 
-  const content = renderMarkdown(displayContent)
+  const content = displayContent ? renderMarkdown(displayContent) : ''
 
   const editForm = isOwner ? `
     <div class="post-edit-form" id="post-edit-form" style="display: none;">
-      <input type="text" class="post-edit-title" id="post-edit-title" value="${escapeHtml(post.value.title)}" placeholder="Title">
-      <textarea class="post-edit-content" id="post-edit-content" rows="15">${escapeHtml(post.value.content.text)}</textarea>
+      <input type="text" class="post-edit-title" id="post-edit-title" value="${escapeHtml(post.value.title || '')}" placeholder="Title">
+      <textarea class="post-edit-content" id="post-edit-content" rows="15">${escapeHtml(rawContent)}</textarea>
       <div class="post-edit-actions">
         <button type="button" class="post-edit-cancel" id="post-edit-cancel">Cancel</button>
         <button type="button" class="post-edit-save" id="post-edit-save" data-collection="${collection}" data-rkey="${rkey}">Save</button>
diff --git a/src/web/main.ts b/src/web/main.ts
index af17184..ed92e69 100644
--- a/src/web/main.ts
+++ b/src/web/main.ts
@@ -3,7 +3,7 @@ import './styles/card.css'
 import './styles/card-migrate.css'
 import { getConfig, resolveHandle, getProfile, getPosts, getPost, describeRepo, listRecords, getRecord, getPds, getNetworks, getChatMessages, getCards, getCardAdmin, getRse, getRseAdmin, getLinks } from './lib/api'
 import { parseRoute, onRouteChange, navigate, type Route } from './lib/router'
-import { login, logout, handleCallback, restoreSession, isLoggedIn, getLoggedInHandle, getLoggedInDid, deleteRecord, updatePost, updateChat, updateLinks } from './lib/auth'
+import { login, logout, handleCallback, restoreSession, isLoggedIn, getLoggedInHandle, getLoggedInDid, deleteRecord, updatePost, updateChat, updateLinks, getAgent } from './lib/auth'
 import { validateRecord } from './lib/lexicon'
 import { renderHeader } from './components/header'
 import { renderProfile } from './components/profile'
@@ -446,6 +446,11 @@ async function render(route: Route): Promise<void> {
       }
     }
 
+    // Setup merge button for AT-Browser record detail
+    if (route.type === 'record' && isOwner) {
+      setupRecordMerge()
+    }
+
     // Setup card migration button
     if (route.type === 'card-old' && cardMigrationState?.oldApiUser && cardMigrationState?.oldApiCards) {
       setupMigrationButton(
@@ -629,6 +634,94 @@ function setupPostEdit(collection: string): void {
   })
 }
 
+// Setup merge button for AT-Browser record detail (convert old format to new)
+function setupRecordMerge(): void {
+  const mergeBtn = document.getElementById('record-merge-btn')
+  if (!mergeBtn) return
+
+  mergeBtn.addEventListener('click', async () => {
+    const collection = mergeBtn.getAttribute('data-collection') || ''
+    const rkey = mergeBtn.getAttribute('data-rkey') || ''
+    if (!collection || !rkey) return
+
+    const agent = getAgent()
+    if (!agent) return
+
+    try {
+      // Fetch current record
+      const existing = await agent.com.atproto.repo.getRecord({
+        repo: agent.assertDid,
+        collection,
+        rkey,
+      })
+
+      const oldValue = existing.data.value as Record<string, unknown>
+
+      // Build new format record
+      const newRecord: Record<string, unknown> = {
+        $type: collection,
+        site: (typeof oldValue.site === 'string' && oldValue.site) || window.location.origin,
+        title: (typeof oldValue.title === 'string' ? oldValue.title : '') || '',
+        publishedAt: (typeof oldValue.publishedAt === 'string' && oldValue.publishedAt)
+          || (typeof oldValue.createdAt === 'string' && oldValue.createdAt)
+          || new Date().toISOString(),
+      }
+
+      // Convert content to open union format
+      const oldContent = oldValue.content
+      if (oldContent && typeof oldContent === 'object' && (oldContent as Record<string, unknown>).$type) {
+        // Already new format
+        newRecord.content = oldContent
+      } else if (typeof oldContent === 'string') {
+        // Old string format -> convert to union
+        newRecord.content = {
+          $type: `${collection}#markdown`,
+          text: oldContent,
+        }
+      } else {
+        newRecord.content = {
+          $type: `${collection}#markdown`,
+          text: '',
+        }
+      }
+
+      // Preserve optional fields
+      if (oldValue.description) newRecord.description = oldValue.description
+      if (oldValue.tags) newRecord.tags = oldValue.tags
+      if (oldValue.langs) newRecord.langs = oldValue.langs
+      if (oldValue.translations) newRecord.translations = oldValue.translations
+      if (oldValue.path) newRecord.path = oldValue.path
+      if (oldValue.root) newRecord.root = oldValue.root
+      if (oldValue.parent) newRecord.parent = oldValue.parent
+      if (oldValue.updatedAt) newRecord.updatedAt = oldValue.updatedAt
+
+      if (!confirm(`Merge record to new format?\n\nCollection: ${collection}\nRkey: ${rkey}`)) return
+
+      mergeBtn.textContent = 'Merging...'
+      ;(mergeBtn as HTMLButtonElement).disabled = true
+
+      await agent.com.atproto.repo.putRecord({
+        repo: agent.assertDid,
+        collection,
+        rkey,
+        record: newRecord,
+      })
+
+      mergeBtn.textContent = 'Merged!'
+
+      // Refresh page after short delay
+      setTimeout(() => {
+        render(parseRoute())
+      }, 1000)
+    } catch (err) {
+      console.error('Merge failed:', err)
+      alert('Merge failed: ' + err)
+      mergeBtn.textContent = 'Merge'
+      ;(mergeBtn as HTMLButtonElement).disabled = false
+    }
+  })
+}
+
 // Setup chat edit form
 function setupChatEdit(collection: string, handle: string): void {
   const form = document.getElementById('chat-edit-form') as HTMLFormElement
diff --git a/src/web/styles/main.css b/src/web/styles/main.css
index 723de43..4431766 100644
--- a/src/web/styles/main.css
+++ b/src/web/styles/main.css
@@ -684,6 +684,30 @@ body {
   opacity: 0.85;
 }
 
+.record-merge-btn {
+  display: inline-flex;
+  align-items: center;
+  justify-content: center;
+  padding: 4px 10px;
+  margin-left: 8px;
+  background: var(--btn-color);
+  color: #fff;
+  border: none;
+  border-radius: 4px;
+  font-size: 12px;
+  cursor: pointer;
+  transition: opacity 0.2s;
+}
+
+.record-merge-btn:hover {
+  opacity: 0.85;
+}
+
+.record-merge-btn:disabled {
+  opacity: 0.5;
+  cursor: not-allowed;
+}
+
 /* Post Edit Form */
 .post-edit-form {
   margin-top: 16px;