diff --git a/backend/Gemfile b/backend/Gemfile
index 7b44641..ba2bbb1 100644
--- a/backend/Gemfile
+++ b/backend/Gemfile
@@ -71,3 +71,5 @@ gem "rspec-rails", "~> 8.0", :groups => [:development, :test]
 gem 'aws-sdk-s3', require: false
 
 gem 'rails-i18n', '~> 8.0.0'
+
+gem "json", "~> 2.19.9"
diff --git a/backend/Gemfile.lock b/backend/Gemfile.lock
index 555f867..c130664 100644
--- a/backend/Gemfile.lock
+++ b/backend/Gemfile.lock
@@ -1,29 +1,29 @@
 GEM
   remote: https://rubygems.org/
   specs:
-    actioncable (8.0.2)
-      actionpack (= 8.0.2)
-      activesupport (= 8.0.2)
+    actioncable (8.0.5.1)
+      actionpack (= 8.0.5.1)
+      activesupport (= 8.0.5.1)
       nio4r (~> 2.0)
       websocket-driver (>= 0.6.1)
       zeitwerk (~> 2.6)
-    actionmailbox (8.0.2)
-      actionpack (= 8.0.2)
-      activejob (= 8.0.2)
-      activerecord (= 8.0.2)
-      activestorage (= 8.0.2)
-      activesupport (= 8.0.2)
+    actionmailbox (8.0.5.1)
+      actionpack (= 8.0.5.1)
+      activejob (= 8.0.5.1)
+      activerecord (= 8.0.5.1)
+      activestorage (= 8.0.5.1)
+      activesupport (= 8.0.5.1)
       mail (>= 2.8.0)
-    actionmailer (8.0.2)
-      actionpack (= 8.0.2)
-      actionview (= 8.0.2)
-      activejob (= 8.0.2)
-      activesupport (= 8.0.2)
+    actionmailer (8.0.5.1)
+      actionpack (= 8.0.5.1)
+      actionview (= 8.0.5.1)
+      activejob (= 8.0.5.1)
+      activesupport (= 8.0.5.1)
       mail (>= 2.8.0)
       rails-dom-testing (~> 2.2)
-    actionpack (8.0.2)
-      actionview (= 8.0.2)
-      activesupport (= 8.0.2)
+    actionpack (8.0.5.1)
+      actionview (= 8.0.5.1)
+      activesupport (= 8.0.5.1)
       nokogiri (>= 1.8.5)
       rack (>= 2.2.4)
       rack-session (>= 1.0.1)
@@ -31,35 +31,35 @@ GEM
       rails-dom-testing (~> 2.2)
       rails-html-sanitizer (~> 1.6)
       useragent (~> 0.16)
-    actiontext (8.0.2)
-      actionpack (= 8.0.2)
-      activerecord (= 8.0.2)
-      activestorage (= 8.0.2)
-      activesupport (= 8.0.2)
+    actiontext (8.0.5.1)
+      actionpack (= 8.0.5.1)
+      activerecord (= 8.0.5.1)
+      activestorage (= 8.0.5.1)
+      activesupport (= 8.0.5.1)
       globalid (>= 0.6.0)
       nokogiri (>= 1.8.5)
-    actionview (8.0.2)
-      activesupport (= 8.0.2)
+    actionview (8.0.5.1)
+      activesupport (= 8.0.5.1)
       builder (~> 3.1)
       erubi (~> 1.11)
       rails-dom-testing (~> 2.2)
       rails-html-sanitizer (~> 1.6)
-    activejob (8.0.2)
-      activesupport (= 8.0.2)
+    activejob (8.0.5.1)
+      activesupport (= 8.0.5.1)
       globalid (>= 0.3.6)
-    activemodel (8.0.2)
-      activesupport (= 8.0.2)
-    activerecord (8.0.2)
-      activemodel (= 8.0.2)
-      activesupport (= 8.0.2)
+    activemodel (8.0.5.1)
+      activesupport (= 8.0.5.1)
+    activerecord (8.0.5.1)
+      activemodel (= 8.0.5.1)
+      activesupport (= 8.0.5.1)
       timeout (>= 0.4.0)
-    activestorage (8.0.2)
-      actionpack (= 8.0.2)
-      activejob (= 8.0.2)
-      activerecord (= 8.0.2)
-      activesupport (= 8.0.2)
+    activestorage (8.0.5.1)
+      actionpack (= 8.0.5.1)
+      activejob (= 8.0.5.1)
+      activerecord (= 8.0.5.1)
+      activesupport (= 8.0.5.1)
       marcel (~> 1.0)
-    activesupport (8.0.2)
+    activesupport (8.0.5.1)
       base64
       benchmark (>= 0.3)
       bigdecimal
@@ -92,22 +92,22 @@ GEM
       aws-sigv4 (~> 1.5)
     aws-sigv4 (1.12.1)
       aws-eventstream (~> 1, >= 1.0.2)
-    base64 (0.2.0)
+    base64 (0.3.0)
     bcrypt_pbkdf (1.1.1)
     bcrypt_pbkdf (1.1.1-arm64-darwin)
     bcrypt_pbkdf (1.1.1-x86_64-darwin)
-    benchmark (0.4.0)
-    bigdecimal (3.1.9)
+    benchmark (0.5.0)
+    bigdecimal (4.1.3)
     bootsnap (1.18.6)
       msgpack (~> 1.2)
     brakeman (7.0.2)
       racc
     builder (3.3.0)
     chronic (0.10.2)
-    concurrent-ruby (1.3.5)
-    connection_pool (2.5.3)
-    crass (1.0.6)
-    date (3.4.1)
+    concurrent-ruby (1.3.8)
+    connection_pool (3.0.2)
+    crass (1.0.7)
+    date (3.6.0)
     diff-lcs (1.6.2)
     discard (1.4.0)
       activerecord (>= 4.2, < 9.0)
@@ -115,8 +115,9 @@ GEM
     dotenv-rails (3.1.8)
       dotenv (= 3.1.8)
       railties (>= 6.1)
-    drb (2.2.1)
+    drb (2.2.3)
     ed25519 (1.4.0)
+    erb (6.0.7)
     erubi (1.13.1)
     factory_bot (6.5.6)
       activesupport (>= 6.1.0)
@@ -134,7 +135,7 @@ GEM
     gemojione (4.3.3)
       json
     github-markup (4.0.2)
-    globalid (1.2.1)
+    globalid (1.4.0)
       activesupport (>= 6.1)
     gollum (6.1.0)
       gemojione (~> 4.1)
@@ -166,19 +167,20 @@ GEM
     gollum-rugged_adapter (3.0)
       mime-types (~> 3.4)
       rugged (~> 1.5)
-    i18n (1.14.7)
+    i18n (1.15.2)
       concurrent-ruby (~> 1.0)
     image_processing (1.14.0)
       mini_magick (>= 4.9.5, < 6)
       ruby-vips (>= 2.0.17, < 3)
-    io-console (0.8.0)
-    irb (1.15.2)
+    io-console (0.9.4)
+    irb (1.18.0)
       pp (>= 0.6.0)
+      prism (>= 1.3.0)
       rdoc (>= 4.0.0)
       reline (>= 0.4.2)
     jmespath (1.6.2)
-    json (2.12.0)
-    jwt (2.10.1)
+    json (2.19.9)
+    jwt (3.3.0)
       base64
     kamal (2.6.1)
       activesupport (>= 7.0)
@@ -198,15 +200,16 @@ GEM
     language_server-protocol (3.17.0.5)
     lint_roller (1.1.0)
     logger (1.7.0)
-    loofah (2.24.1)
+    loofah (2.25.2)
       crass (~> 1.0.2)
       nokogiri (>= 1.12.0)
-    mail (2.8.1)
+    mail (2.9.1)
+      logger
       mini_mime (>= 0.1.1)
       net-imap
       net-pop
       net-smtp
-    marcel (1.0.4)
+    marcel (1.2.1)
     mime-types (3.7.0)
       logger
       mime-types-data (~> 3.2025, >= 3.2025.0507)
@@ -215,45 +218,46 @@ GEM
       benchmark
       logger
     mini_mime (1.1.5)
-    minitest (5.25.5)
-    msgpack (1.8.0)
-    multi_json (1.15.0)
+    minitest (6.0.6)
+      drb (~> 2.0)
+      prism (~> 1.5)
+    msgpack (1.8.5)
+    multi_json (1.21.2)
     mustache (1.1.1)
     mustache-sinatra (2.0.0)
       mustache (~> 1.0)
-    mustermann (3.0.3)
-      ruby2_keywords (~> 0.0.1)
+    mustermann (3.1.1)
     mysql2 (0.5.6)
-    net-imap (0.5.8)
+    net-imap (0.6.8)
       date
       net-protocol
     net-pop (0.1.2)
       net-protocol
-    net-protocol (0.2.2)
+    net-protocol (0.4.0)
       timeout
     net-scp (4.1.0)
       net-ssh (>= 2.6.5, < 8.0.0)
     net-sftp (4.0.0)
       net-ssh (>= 5.0.0, < 8.0.0)
-    net-smtp (0.5.1)
+    net-smtp (0.5.2)
       net-protocol
     net-ssh (7.3.0)
-    nio4r (2.7.4)
-    nokogiri (1.18.8-aarch64-linux-gnu)
+    nio4r (2.7.5)
+    nokogiri (1.19.4-aarch64-linux-gnu)
       racc (~> 1.4)
-    nokogiri (1.18.8-aarch64-linux-musl)
+    nokogiri (1.19.4-aarch64-linux-musl)
       racc (~> 1.4)
-    nokogiri (1.18.8-arm-linux-gnu)
+    nokogiri (1.19.4-arm-linux-gnu)
       racc (~> 1.4)
-    nokogiri (1.18.8-arm-linux-musl)
+    nokogiri (1.19.4-arm-linux-musl)
       racc (~> 1.4)
-    nokogiri (1.18.8-arm64-darwin)
+    nokogiri (1.19.4-arm64-darwin)
       racc (~> 1.4)
-    nokogiri (1.18.8-x86_64-darwin)
+    nokogiri (1.19.4-x86_64-darwin)
       racc (~> 1.4)
-    nokogiri (1.18.8-x86_64-linux-gnu)
+    nokogiri (1.19.4-x86_64-linux-gnu)
       racc (~> 1.4)
-    nokogiri (1.18.8-x86_64-linux-musl)
+    nokogiri (1.19.4-x86_64-linux-musl)
       racc (~> 1.4)
     octicons (19.15.2)
     ostruct (0.6.1)
@@ -261,70 +265,73 @@ GEM
     parser (3.3.8.0)
       ast (~> 2.4.1)
       racc
-    pp (0.6.2)
+    pp (0.6.4)
       prettyprint
-    prettyprint (0.2.0)
-    prism (1.4.0)
-    psych (5.2.6)
+    prettyprint (0.2.1)
+    prism (1.9.0)
+    psych (5.5.0)
       date
       stringio
     puma (6.6.0)
       nio4r (~> 2.0)
     racc (1.8.1)
-    rack (3.1.14)
+    rack (3.2.7)
     rack-cors (2.0.2)
       rack (>= 2.0.0)
-    rack-protection (4.1.1)
+    rack-protection (4.2.1)
       base64 (>= 0.1.0)
       logger (>= 1.6.0)
       rack (>= 3.0.0, < 4)
-    rack-session (2.1.1)
+    rack-session (2.1.2)
       base64 (>= 0.1.0)
       rack (>= 3.0.0)
-    rack-test (2.2.0)
+    rack-test (2.3.0)
       rack (>= 1.3)
-    rackup (2.2.1)
+    rackup (2.3.1)
       rack (>= 3)
-    rails (8.0.2)
-      actioncable (= 8.0.2)
-      actionmailbox (= 8.0.2)
-      actionmailer (= 8.0.2)
-      actionpack (= 8.0.2)
-      actiontext (= 8.0.2)
-      actionview (= 8.0.2)
-      activejob (= 8.0.2)
-      activemodel (= 8.0.2)
-      activerecord (= 8.0.2)
-      activestorage (= 8.0.2)
-      activesupport (= 8.0.2)
+    rails (8.0.5.1)
+      actioncable (= 8.0.5.1)
+      actionmailbox (= 8.0.5.1)
+      actionmailer (= 8.0.5.1)
+      actionpack (= 8.0.5.1)
+      actiontext (= 8.0.5.1)
+      actionview (= 8.0.5.1)
+      activejob (= 8.0.5.1)
+      activemodel (= 8.0.5.1)
+      activerecord (= 8.0.5.1)
+      activestorage (= 8.0.5.1)
+      activesupport (= 8.0.5.1)
       bundler (>= 1.15.0)
-      railties (= 8.0.2)
-    rails-dom-testing (2.2.0)
+      railties (= 8.0.5.1)
+    rails-dom-testing (2.3.0)
       activesupport (>= 5.0.0)
       minitest
       nokogiri (>= 1.6)
-    rails-html-sanitizer (1.6.2)
-      loofah (~> 2.21)
+    rails-html-sanitizer (1.7.1)
+      loofah (~> 2.25, >= 2.25.2)
       nokogiri (>= 1.15.7, != 1.16.7, != 1.16.6, != 1.16.5, != 1.16.4, != 1.16.3, != 1.16.2, != 1.16.1, != 1.16.0.rc1, != 1.16.0)
     rails-i18n (8.0.2)
       i18n (>= 0.7, < 2)
       railties (>= 8.0.0, < 9)
-    railties (8.0.2)
-      actionpack (= 8.0.2)
-      activesupport (= 8.0.2)
+    railties (8.0.5.1)
+      actionpack (= 8.0.5.1)
+      activesupport (= 8.0.5.1)
       irb (~> 1.13)
       rackup (>= 1.0.0)
       rake (>= 12.2)
       thor (~> 1.0, >= 1.2.2)
+      tsort (>= 0.2)
       zeitwerk (~> 2.6)
     rainbow (3.1.1)
-    rake (13.2.1)
-    rdoc (6.13.1)
+    rake (13.4.2)
+    rdoc (6.17.0)
+      erb
       psych (>= 4.0.0)
-    regexp_parser (2.10.0)
-    reline (0.6.1)
+      tsort
+    regexp_parser (2.13.1)
+    reline (0.7.0)
       io-console (~> 0.5)
-    rexml (3.4.1)
+    rexml (3.4.4)
     rouge (3.30.0)
     rspec-core (3.13.6)
       rspec-support (~> 3.13.0)
@@ -345,20 +352,20 @@ GEM
     rspec-support (3.13.6)
     rss (0.3.1)
       rexml
-    rubocop (1.75.6)
-      json (~> 2.3)
+    rubocop (1.92.0)
+      json (>= 2.3)
       language_server-protocol (~> 3.17.0.2)
       lint_roller (~> 1.1.0)
-      parallel (~> 1.10)
+      parallel (>= 1.10)
       parser (>= 3.3.0.2)
       rainbow (>= 2.2.2, < 4.0)
-      regexp_parser (>= 2.9.3, < 3.0)
-      rubocop-ast (>= 1.44.0, < 2.0)
+      regexp_parser (>= 2.11.3, < 3.0)
+      rubocop-ast (>= 1.49.0, < 2.0)
       ruby-progressbar (~> 1.7)
       unicode-display_width (>= 2.4.0, < 4.0)
-    rubocop-ast (1.44.1)
+    rubocop-ast (1.50.0)
       parser (>= 3.3.7.2)
-      prism (~> 1.4)
+      prism (~> 1.7)
     rubocop-performance (1.25.0)
       lint_roller (~> 1.1)
       rubocop (>= 1.75.0, < 2.0)
@@ -377,24 +384,23 @@ GEM
     ruby-vips (2.2.3)
       ffi (~> 1.12)
       logger
-    ruby2_keywords (0.0.5)
     rugged (1.9.0)
     securerandom (0.4.1)
-    sinatra (4.1.1)
+    sinatra (4.2.1)
       logger (>= 1.6.0)
       mustermann (~> 3.0)
       rack (>= 3.0.0, < 4)
-      rack-protection (= 4.1.1)
+      rack-protection (= 4.2.1)
       rack-session (>= 2.0.0, < 3)
       tilt (~> 2.0)
-    sinatra-contrib (4.1.1)
+    sinatra-contrib (4.2.1)
       multi_json (>= 0.0.2)
       mustermann (~> 3.0)
-      rack-protection (= 4.1.1)
-      sinatra (= 4.1.1)
+      rack-protection (= 4.2.1)
+      sinatra (= 4.2.1)
       tilt (~> 2.0)
-    sprockets (4.2.2)
-      concurrent-ruby (~> 1.0)
+    sprockets (4.4.1)
+      concurrent-ruby (~> 1.1)
       logger
       rack (>= 2.2.4, < 4)
     sprockets-helpers (1.4.0)
@@ -403,14 +409,14 @@ GEM
       actionpack (>= 6.1)
       activesupport (>= 6.1)
       sprockets (>= 3.0.0)
-    sqlite3 (2.6.0-aarch64-linux-gnu)
-    sqlite3 (2.6.0-aarch64-linux-musl)
-    sqlite3 (2.6.0-arm-linux-gnu)
-    sqlite3 (2.6.0-arm-linux-musl)
-    sqlite3 (2.6.0-arm64-darwin)
-    sqlite3 (2.6.0-x86_64-darwin)
-    sqlite3 (2.6.0-x86_64-linux-gnu)
-    sqlite3 (2.6.0-x86_64-linux-musl)
+    sqlite3 (2.10.1-aarch64-linux-gnu)
+    sqlite3 (2.10.1-aarch64-linux-musl)
+    sqlite3 (2.10.1-arm-linux-gnu)
+    sqlite3 (2.10.1-arm-linux-musl)
+    sqlite3 (2.10.1-arm64-darwin)
+    sqlite3 (2.10.1-x86_64-darwin)
+    sqlite3 (2.10.1-x86_64-linux-gnu)
+    sqlite3 (2.10.1-x86_64-linux-musl)
     sshkit (1.24.0)
       base64
       logger
@@ -418,18 +424,19 @@ GEM
       net-sftp (>= 2.1.2)
       net-ssh (>= 2.8.0)
       ostruct
-    stringio (3.1.7)
+    stringio (3.2.0)
     therubyrhino (2.1.2)
       therubyrhino_jar (>= 1.7.4, < 1.7.9)
     therubyrhino_jar (1.7.8)
-    thor (1.3.2)
+    thor (1.5.0)
     thruster (0.1.13)
     thruster (0.1.13-aarch64-linux)
     thruster (0.1.13-arm64-darwin)
     thruster (0.1.13-x86_64-darwin)
     thruster (0.1.13-x86_64-linux)
-    tilt (2.6.0)
-    timeout (0.4.3)
+    tilt (2.9.0)
+    timeout (0.6.1)
+    tsort (0.2.0)
     twitter-text (1.14.7)
       unf (~> 0.1.0)
     tzinfo (2.0.6)
@@ -440,16 +447,16 @@ GEM
     unicode-display_width (3.1.4)
       unicode-emoji (~> 4.0, >= 4.0.4)
     unicode-emoji (4.0.4)
-    uri (1.0.3)
+    uri (1.1.2)
     useragent (0.16.11)
     webrick (1.9.1)
-    websocket-driver (0.7.7)
+    websocket-driver (0.8.2)
       base64
       websocket-extensions (>= 0.1.0)
     websocket-extensions (0.1.5)
     whenever (1.0.0)
       chronic (>= 0.6.3)
-    zeitwerk (2.7.2)
+    zeitwerk (2.8.3)
 
 PLATFORMS
   aarch64-linux
@@ -473,6 +480,7 @@ DEPENDENCIES
   factory_bot_rails
   gollum
   image_processing (~> 1.14)
+  json (~> 2.19.9)
   jwt
   kamal
   mysql2 (~> 0.5.6)
diff --git a/backend/app/controllers/post_versions_controller.rb b/backend/app/controllers/post_versions_controller.rb
index 9c86c93..92b35c7 100644
--- a/backend/app/controllers/post_versions_controller.rb
+++ b/backend/app/controllers/post_versions_controller.rb
@@ -15,6 +15,7 @@ class PostVersionsController < ApplicationController
     offset = (page - 1) * limit
 
     q = HistoryAccess.visible(PostVersion.all)
+    q = q.with_previous_version if tag_id || external_tag_id
     q = q.where('post_versions.post_id = ?', post_id) if post_id
     q = q.with_previous_version if tag_id || external_tag_id
     if external_tag_id || (tag_id && !(Tag.exists?(id: tag_id)))
diff --git a/backend/app/controllers/posts_controller.rb b/backend/app/controllers/posts_controller.rb
index 38c74ca..4d96673 100644
--- a/backend/app/controllers/posts_controller.rb
+++ b/backend/app/controllers/posts_controller.rb
@@ -37,15 +37,7 @@ class PostsController < ApplicationController
 
     offset = (page - 1) * limit
 
-    pt_max_sql =
-        HistoryAccess.visible(PostVersion.all)
-        .where('post_versions.post_id = posts.id')
-        .select('MAX(post_versions.created_at)')
-        .to_sql
-
-    updated_at_all_sql =
-        'GREATEST(posts.updated_at,' +
-        "COALESCE((#{ pt_max_sql }), posts.updated_at))"
+    updated_at_all_sql = 'posts.updated_at'
 
     q =
         filtered_posts(locale)
@@ -93,8 +85,7 @@ class PostsController < ApplicationController
 
     render json: { posts: posts.map { |post|
       PostRepr.base(post, language_code: locale.language_code)
-              .merge(updated_at: [post.updated_at, latest_version_times[post.id]].compact.max)
-              .tap do |json|
+              .merge(updated_at: post.updated_at).tap do |json|
         json['thumbnail'] =
             if post.thumbnail.attached?
               rails_storage_proxy_url(post.thumbnail, only_path: false)
diff --git a/backend/app/models/history_access.rb b/backend/app/models/history_access.rb
index ced5f98..5745e73 100644
--- a/backend/app/models/history_access.rb
+++ b/backend/app/models/history_access.rb
@@ -114,7 +114,7 @@ class HistoryAccess < ActiveSupport::CurrentAttributes
       private_names = 'SELECT DISTINCT private_name.name, ' +
           'CAST(private_name.name AS BINARY) AS name_bytes FROM tag_versions private_tag ' +
           "JOIN (#{ discarded_keys('tag_versions', 'tag_id') }) blocked " +
-          "ON blocked.tag_id = private_tag.tag_id " +
+          'ON blocked.tag_id = private_tag.tag_id ' +
           "JOIN JSON_TABLE(#{ names }, '$[*]' COLUMNS (name TEXT PATH '$')) private_name " +
           "WHERE private_name.name <> ''"
       ["NOT EXISTS (SELECT 1 FROM (#{ private_names }) private_name WHERE " +