#414

backend/Gemfile

@@ -71,5 +71,3 @@ 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"

backend/Gemfile.lock

@@ -1,29 +1,29 @@
 GEM
   remote: https://rubygems.org/
   specs:
-    actioncable (8.0.5.1)
+    actioncable (8.0.2)
-      actionpack (= 8.0.5.1)
+      actionpack (= 8.0.2)
-      activesupport (= 8.0.5.1)
+      activesupport (= 8.0.2)
       nio4r (~> 2.0)
       websocket-driver (>= 0.6.1)
       zeitwerk (~> 2.6)
-    actionmailbox (8.0.5.1)
+    actionmailbox (8.0.2)
-      actionpack (= 8.0.5.1)
+      actionpack (= 8.0.2)
-      activejob (= 8.0.5.1)
+      activejob (= 8.0.2)
-      activerecord (= 8.0.5.1)
+      activerecord (= 8.0.2)
-      activestorage (= 8.0.5.1)
+      activestorage (= 8.0.2)
-      activesupport (= 8.0.5.1)
+      activesupport (= 8.0.2)
       mail (>= 2.8.0)
-    actionmailer (8.0.5.1)
+    actionmailer (8.0.2)
-      actionpack (= 8.0.5.1)
+      actionpack (= 8.0.2)
-      actionview (= 8.0.5.1)
+      actionview (= 8.0.2)
-      activejob (= 8.0.5.1)
+      activejob (= 8.0.2)
-      activesupport (= 8.0.5.1)
+      activesupport (= 8.0.2)
       mail (>= 2.8.0)
       rails-dom-testing (~> 2.2)
-    actionpack (8.0.5.1)
+    actionpack (8.0.2)
-      actionview (= 8.0.5.1)
+      actionview (= 8.0.2)
-      activesupport (= 8.0.5.1)
+      activesupport (= 8.0.2)
       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 (8.0.5.1)
+    actiontext (8.0.2)
-      actionpack (= 8.0.5.1)
+      actionpack (= 8.0.2)
-      activerecord (= 8.0.5.1)
+      activerecord (= 8.0.2)
-      activestorage (= 8.0.5.1)
+      activestorage (= 8.0.2)
-      activesupport (= 8.0.5.1)
+      activesupport (= 8.0.2)
       globalid (>= 0.6.0)
       nokogiri (>= 1.8.5)
-    actionview (8.0.5.1)
+    actionview (8.0.2)
-      activesupport (= 8.0.5.1)
+      activesupport (= 8.0.2)
       builder (~> 3.1)
       erubi (~> 1.11)
       rails-dom-testing (~> 2.2)
       rails-html-sanitizer (~> 1.6)
-    activejob (8.0.5.1)
+    activejob (8.0.2)
-      activesupport (= 8.0.5.1)
+      activesupport (= 8.0.2)
       globalid (>= 0.3.6)
-    activemodel (8.0.5.1)
+    activemodel (8.0.2)
-      activesupport (= 8.0.5.1)
+      activesupport (= 8.0.2)
-    activerecord (8.0.5.1)
+    activerecord (8.0.2)
-      activemodel (= 8.0.5.1)
+      activemodel (= 8.0.2)
-      activesupport (= 8.0.5.1)
+      activesupport (= 8.0.2)
       timeout (>= 0.4.0)
-    activestorage (8.0.5.1)
+    activestorage (8.0.2)
-      actionpack (= 8.0.5.1)
+      actionpack (= 8.0.2)
-      activejob (= 8.0.5.1)
+      activejob (= 8.0.2)
-      activerecord (= 8.0.5.1)
+      activerecord (= 8.0.2)
-      activesupport (= 8.0.5.1)
+      activesupport (= 8.0.2)
       marcel (~> 1.0)
-    activesupport (8.0.5.1)
+    activesupport (8.0.2)
       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 (0.3.0)
+    base64 (0.2.0)
     bcrypt_pbkdf (1.1.1)
     bcrypt_pbkdf (1.1.1-arm64-darwin)
     bcrypt_pbkdf (1.1.1-x86_64-darwin)
-    benchmark (0.5.0)
+    benchmark (0.4.0)
-    bigdecimal (4.1.3)
+    bigdecimal (3.1.9)
     bootsnap (1.18.6)
       msgpack (~> 1.2)
     brakeman (7.0.2)
       racc
     builder (3.3.0)
     chronic (0.10.2)
-    concurrent-ruby (1.3.8)
+    concurrent-ruby (1.3.5)
-    connection_pool (3.0.2)
+    connection_pool (2.5.3)
-    crass (1.0.7)
+    crass (1.0.6)
-    date (3.6.0)
+    date (3.4.1)
     diff-lcs (1.6.2)
     discard (1.4.0)
       activerecord (>= 4.2, < 9.0)
@@ -115,9 +115,8 @@ GEM
     dotenv-rails (3.1.8)
       dotenv (= 3.1.8)
       railties (>= 6.1)
-    drb (2.2.3)
+    drb (2.2.1)
     ed25519 (1.4.0)
-    erb (6.0.7)
     erubi (1.13.1)
     factory_bot (6.5.6)
       activesupport (>= 6.1.0)
@@ -135,7 +134,7 @@ GEM
     gemojione (4.3.3)
       json
     github-markup (4.0.2)
-    globalid (1.4.0)
+    globalid (1.2.1)
       activesupport (>= 6.1)
     gollum (6.1.0)
       gemojione (~> 4.1)
@@ -167,20 +166,19 @@ GEM
     gollum-rugged_adapter (3.0)
       mime-types (~> 3.4)
       rugged (~> 1.5)
-    i18n (1.15.2)
+    i18n (1.14.7)
       concurrent-ruby (~> 1.0)
     image_processing (1.14.0)
       mini_magick (>= 4.9.5, < 6)
       ruby-vips (>= 2.0.17, < 3)
-    io-console (0.9.4)
+    io-console (0.8.0)
-    irb (1.18.0)
+    irb (1.15.2)
       pp (>= 0.6.0)
-      prism (>= 1.3.0)
       rdoc (>= 4.0.0)
       reline (>= 0.4.2)
     jmespath (1.6.2)
-    json (2.19.9)
+    json (2.12.0)
-    jwt (3.3.0)
+    jwt (2.10.1)
       base64
     kamal (2.6.1)
       activesupport (>= 7.0)
@@ -200,16 +198,15 @@ GEM
     language_server-protocol (3.17.0.5)
     lint_roller (1.1.0)
     logger (1.7.0)
-    loofah (2.25.2)
+    loofah (2.24.1)
       crass (~> 1.0.2)
       nokogiri (>= 1.12.0)
-    mail (2.9.1)
+    mail (2.8.1)
-      logger
       mini_mime (>= 0.1.1)
       net-imap
       net-pop
       net-smtp
-    marcel (1.2.1)
+    marcel (1.0.4)
     mime-types (3.7.0)
       logger
       mime-types-data (~> 3.2025, >= 3.2025.0507)
@@ -218,46 +215,45 @@ GEM
       benchmark
       logger
     mini_mime (1.1.5)
-    minitest (6.0.6)
+    minitest (5.25.5)
-      drb (~> 2.0)
+    msgpack (1.8.0)
-      prism (~> 1.5)
+    multi_json (1.15.0)
-    msgpack (1.8.5)
-    multi_json (1.21.2)
     mustache (1.1.1)
     mustache-sinatra (2.0.0)
       mustache (~> 1.0)
-    mustermann (3.1.1)
+    mustermann (3.0.3)
+      ruby2_keywords (~> 0.0.1)
     mysql2 (0.5.6)
-    net-imap (0.6.8)
+    net-imap (0.5.8)
       date
       net-protocol
     net-pop (0.1.2)
       net-protocol
-    net-protocol (0.4.0)
+    net-protocol (0.2.2)
       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 (0.5.2)
+    net-smtp (0.5.1)
       net-protocol
     net-ssh (7.3.0)
-    nio4r (2.7.5)
+    nio4r (2.7.4)
-    nokogiri (1.19.4-aarch64-linux-gnu)
+    nokogiri (1.18.8-aarch64-linux-gnu)
       racc (~> 1.4)
-    nokogiri (1.19.4-aarch64-linux-musl)
+    nokogiri (1.18.8-aarch64-linux-musl)
       racc (~> 1.4)
-    nokogiri (1.19.4-arm-linux-gnu)
+    nokogiri (1.18.8-arm-linux-gnu)
       racc (~> 1.4)
-    nokogiri (1.19.4-arm-linux-musl)
+    nokogiri (1.18.8-arm-linux-musl)
       racc (~> 1.4)
-    nokogiri (1.19.4-arm64-darwin)
+    nokogiri (1.18.8-arm64-darwin)
       racc (~> 1.4)
-    nokogiri (1.19.4-x86_64-darwin)
+    nokogiri (1.18.8-x86_64-darwin)
       racc (~> 1.4)
-    nokogiri (1.19.4-x86_64-linux-gnu)
+    nokogiri (1.18.8-x86_64-linux-gnu)
       racc (~> 1.4)
-    nokogiri (1.19.4-x86_64-linux-musl)
+    nokogiri (1.18.8-x86_64-linux-musl)
       racc (~> 1.4)
     octicons (19.15.2)
     ostruct (0.6.1)
@@ -265,73 +261,70 @@ GEM
     parser (3.3.8.0)
       ast (~> 2.4.1)
       racc
-    pp (0.6.4)
+    pp (0.6.2)
       prettyprint
-    prettyprint (0.2.1)
+    prettyprint (0.2.0)
-    prism (1.9.0)
+    prism (1.4.0)
-    psych (5.5.0)
+    psych (5.2.6)
       date
       stringio
     puma (6.6.0)
       nio4r (~> 2.0)
     racc (1.8.1)
-    rack (3.2.7)
+    rack (3.1.14)
     rack-cors (2.0.2)
       rack (>= 2.0.0)
-    rack-protection (4.2.1)
+    rack-protection (4.1.1)
       base64 (>= 0.1.0)
       logger (>= 1.6.0)
       rack (>= 3.0.0, < 4)
-    rack-session (2.1.2)
+    rack-session (2.1.1)
       base64 (>= 0.1.0)
       rack (>= 3.0.0)
-    rack-test (2.3.0)
+    rack-test (2.2.0)
       rack (>= 1.3)
-    rackup (2.3.1)
+    rackup (2.2.1)
       rack (>= 3)
-    rails (8.0.5.1)
+    rails (8.0.2)
-      actioncable (= 8.0.5.1)
+      actioncable (= 8.0.2)
-      actionmailbox (= 8.0.5.1)
+      actionmailbox (= 8.0.2)
-      actionmailer (= 8.0.5.1)
+      actionmailer (= 8.0.2)
-      actionpack (= 8.0.5.1)
+      actionpack (= 8.0.2)
-      actiontext (= 8.0.5.1)
+      actiontext (= 8.0.2)
-      actionview (= 8.0.5.1)
+      actionview (= 8.0.2)
-      activejob (= 8.0.5.1)
+      activejob (= 8.0.2)
-      activemodel (= 8.0.5.1)
+      activemodel (= 8.0.2)
-      activerecord (= 8.0.5.1)
+      activerecord (= 8.0.2)
-      activestorage (= 8.0.5.1)
+      activestorage (= 8.0.2)
-      activesupport (= 8.0.5.1)
+      activesupport (= 8.0.2)
       bundler (>= 1.15.0)
-      railties (= 8.0.5.1)
+      railties (= 8.0.2)
-    rails-dom-testing (2.3.0)
+    rails-dom-testing (2.2.0)
       activesupport (>= 5.0.0)
       minitest
       nokogiri (>= 1.6)
-    rails-html-sanitizer (1.7.1)
+    rails-html-sanitizer (1.6.2)
-      loofah (~> 2.25, >= 2.25.2)
+      loofah (~> 2.21)
       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 (8.0.5.1)
+    railties (8.0.2)
-      actionpack (= 8.0.5.1)
+      actionpack (= 8.0.2)
-      activesupport (= 8.0.5.1)
+      activesupport (= 8.0.2)
       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 (13.4.2)
+    rake (13.2.1)
-    rdoc (6.17.0)
+    rdoc (6.13.1)
-      erb
       psych (>= 4.0.0)
-      tsort
+    regexp_parser (2.10.0)
-    regexp_parser (2.13.1)
+    reline (0.6.1)
-    reline (0.7.0)
       io-console (~> 0.5)
-    rexml (3.4.4)
+    rexml (3.4.1)
     rouge (3.30.0)
     rspec-core (3.13.6)
       rspec-support (~> 3.13.0)
@@ -352,20 +345,20 @@ GEM
     rspec-support (3.13.6)
     rss (0.3.1)
       rexml
-    rubocop (1.92.0)
+    rubocop (1.75.6)
-      json (>= 2.3)
+      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 (>= 2.11.3, < 3.0)
+      regexp_parser (>= 2.9.3, < 3.0)
-      rubocop-ast (>= 1.49.0, < 2.0)
+      rubocop-ast (>= 1.44.0, < 2.0)
       ruby-progressbar (~> 1.7)
       unicode-display_width (>= 2.4.0, < 4.0)
-    rubocop-ast (1.50.0)
+    rubocop-ast (1.44.1)
       parser (>= 3.3.7.2)
-      prism (~> 1.7)
+      prism (~> 1.4)
     rubocop-performance (1.25.0)
       lint_roller (~> 1.1)
       rubocop (>= 1.75.0, < 2.0)
@@ -384,23 +377,24 @@ GEM
     ruby-vips (2.2.3)
       ffi (~> 1.12)
       logger
+    ruby2_keywords (0.0.5)
     rugged (1.9.0)
     securerandom (0.4.1)
-    sinatra (4.2.1)
+    sinatra (4.1.1)
       logger (>= 1.6.0)
       mustermann (~> 3.0)
       rack (>= 3.0.0, < 4)
-      rack-protection (= 4.2.1)
+      rack-protection (= 4.1.1)
       rack-session (>= 2.0.0, < 3)
       tilt (~> 2.0)
-    sinatra-contrib (4.2.1)
+    sinatra-contrib (4.1.1)
       multi_json (>= 0.0.2)
       mustermann (~> 3.0)
-      rack-protection (= 4.2.1)
+      rack-protection (= 4.1.1)
-      sinatra (= 4.2.1)
+      sinatra (= 4.1.1)
       tilt (~> 2.0)
-    sprockets (4.4.1)
+    sprockets (4.2.2)
-      concurrent-ruby (~> 1.1)
+      concurrent-ruby (~> 1.0)
       logger
       rack (>= 2.2.4, < 4)
     sprockets-helpers (1.4.0)
@@ -409,14 +403,14 @@ GEM
       actionpack (>= 6.1)
       activesupport (>= 6.1)
       sprockets (>= 3.0.0)
-    sqlite3 (2.10.1-aarch64-linux-gnu)
+    sqlite3 (2.6.0-aarch64-linux-gnu)
-    sqlite3 (2.10.1-aarch64-linux-musl)
+    sqlite3 (2.6.0-aarch64-linux-musl)
-    sqlite3 (2.10.1-arm-linux-gnu)
+    sqlite3 (2.6.0-arm-linux-gnu)
-    sqlite3 (2.10.1-arm-linux-musl)
+    sqlite3 (2.6.0-arm-linux-musl)
-    sqlite3 (2.10.1-arm64-darwin)
+    sqlite3 (2.6.0-arm64-darwin)
-    sqlite3 (2.10.1-x86_64-darwin)
+    sqlite3 (2.6.0-x86_64-darwin)
-    sqlite3 (2.10.1-x86_64-linux-gnu)
+    sqlite3 (2.6.0-x86_64-linux-gnu)
-    sqlite3 (2.10.1-x86_64-linux-musl)
+    sqlite3 (2.6.0-x86_64-linux-musl)
     sshkit (1.24.0)
       base64
       logger
@@ -424,19 +418,18 @@ GEM
       net-sftp (>= 2.1.2)
       net-ssh (>= 2.8.0)
       ostruct
-    stringio (3.2.0)
+    stringio (3.1.7)
     therubyrhino (2.1.2)
       therubyrhino_jar (>= 1.7.4, < 1.7.9)
     therubyrhino_jar (1.7.8)
-    thor (1.5.0)
+    thor (1.3.2)
     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 (2.9.0)
+    tilt (2.6.0)
-    timeout (0.6.1)
+    timeout (0.4.3)
-    tsort (0.2.0)
     twitter-text (1.14.7)
       unf (~> 0.1.0)
     tzinfo (2.0.6)
@@ -447,16 +440,16 @@ GEM
     unicode-display_width (3.1.4)
       unicode-emoji (~> 4.0, >= 4.0.4)
     unicode-emoji (4.0.4)
-    uri (1.1.2)
+    uri (1.0.3)
     useragent (0.16.11)
     webrick (1.9.1)
-    websocket-driver (0.8.2)
+    websocket-driver (0.7.7)
       base64
       websocket-extensions (>= 0.1.0)
     websocket-extensions (0.1.5)
     whenever (1.0.0)
       chronic (>= 0.6.3)
-    zeitwerk (2.8.3)
+    zeitwerk (2.7.2)
 
 PLATFORMS
   aarch64-linux
@@ -480,7 +473,6 @@ DEPENDENCIES
   factory_bot_rails
   gollum
   image_processing (~> 1.14)
-  json (~> 2.19.9)
   jwt
   kamal
   mysql2 (~> 0.5.6)

backend/app/controllers/post_versions_controller.rb

@@ -14,9 +14,8 @@ class PostVersionsController < ApplicationController
 
     offset = (page - 1) * limit
 
-    q = HistoryAccess.visible(PostVersion.all)
+    q = HistoryAccess.visible(version_scope)
     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)))
       q = q.where('JSON_CONTAINS(post_versions.tags_json,' +
                   "JSON_OBJECT('external_tag_id', #{ external_tag_id || tag_id })) " +
@@ -29,12 +28,9 @@ class PostVersionsController < ApplicationController
 
     count = q.except(:select, :order, :limit, :offset).count
 
-    ids = q.order(Arel.sql('post_versions.created_at DESC, post_versions.id DESC'))
+    versions = q.order(Arel.sql('post_versions.created_at DESC, post_versions.id DESC'))
                 .limit(limit)
                 .offset(offset)
-                .pluck('post_versions.id')
-    versions = version_scope.merge(q).where(id: ids)
-        .order(Arel.sql('post_versions.created_at DESC, post_versions.id DESC'))
 
     render json: { versions: serialise_versions(versions, locale.language_code), count:, population_count: HistoryAccess.population_count(PostVersion) }
   end

backend/app/controllers/posts_controller.rb

@@ -37,10 +37,20 @@ class PostsController < ApplicationController
 
     offset = (page - 1) * limit
 
-    needs_history_join = order[0] == 'updated_at' || updated_between.any?(&:present?)
+    pt_max_sql =
+        HistoryAccess.visible(PostVersion.all)
+        .select('post_id, MAX(created_at) AS max_updated_at')
+        .group('post_id')
+        .to_sql
+
+    updated_at_all_sql =
+        'GREATEST(posts.updated_at,' +
+        'COALESCE(pt_max.max_updated_at, posts.updated_at))'
 
     q =
         filtered_posts(locale)
+        .joins("LEFT JOIN (#{ pt_max_sql }) pt_max ON pt_max.post_id = posts.id")
+        .reselect('posts.*', Arel.sql("#{ updated_at_all_sql } AS updated_at_all"))
         .preload(:external_tags, :uploaded_user, :parents, :children,
                  post_tags: [:sections, { tag: [:deerjikists, :materials,
                                                 :tag_names, :tag_descriptions] }])
@@ -56,25 +66,12 @@ class PostsController < ApplicationController
     end
     q = q.where('posts.created_at >= ?', created_between[0]) if created_between[0]
     q = q.where('posts.created_at <= ?', created_between[1]) if created_between[1]
-    count_scope = q
-    if needs_history_join
-      history_times = HistoryAccess.visible(PostVersion.all)
-          .select('post_id, MAX(created_at) AS latest_at').group(:post_id)
-      q = q.joins("LEFT JOIN (#{ history_times.to_sql }) history_times " +
-                  'ON history_times.post_id = posts.id')
-      updated_at_all_sql = 'GREATEST(posts.updated_at, ' +
-          'COALESCE(history_times.latest_at, posts.updated_at))'
-    end
     if updated_between[0]
       q = q.where("#{ updated_at_all_sql } >= ?", updated_between[0])
     end
     if updated_between[1]
       q = q.where("#{ updated_at_all_sql } <= ?", updated_between[1])
     end
-    count_scope = q if updated_between.any?(&:present?)
-    if needs_history_join
-      q = q.select('posts.*', "#{ updated_at_all_sql } AS updated_at")
-    end
 
     sort_sql =
         case order[0]
@@ -91,20 +88,12 @@ class PostsController < ApplicationController
              .limit(limit)
              .offset(offset)
              .to_a
-    latest_version_times =
-        if needs_history_join
-          { }
-        else
-          HistoryAccess.visible(PostVersion.where(post_id: posts.map(&:id)))
-              .group(:post_id).maximum(:created_at)
-        end
 
-    count_scope = count_scope.except(:select, :order)
+    q = q.except(:select, :order)
 
     render json: { posts: posts.map { |post|
-      updated_at = [post.updated_at, latest_version_times[post.id]].compact.max
       PostRepr.base(post, language_code: locale.language_code)
-          .merge('updated_at' => updated_at).tap do |json|
+              .merge(updated_at: post.updated_at_all).tap do |json|
         json['thumbnail'] =
             if post.thumbnail.attached?
               rails_storage_proxy_url(post.thumbnail, only_path: false)
@@ -112,7 +101,7 @@ class PostsController < ApplicationController
               nil
             end
       end
-    }, count: count_scope.group_values.present? ? count_scope.count.size : count_scope.count }
+    }, count: q.group_values.present? ? q.count.size : q.count }
   end
 
   def random

backend/app/models/event.rb

@@ -0,0 +1,9 @@
+class Event < ApplicationRecord
+  has_many :post_versions
+  has_many :tag_versions
+  has_many :material_versions
+  has_many :tag_description_versions
+  has_many :tag_group_versions
+
+  belongs_to :created_by_user, class_name: 'User', optional: true
+end

backend/app/models/history_access.rb

@@ -4,7 +4,7 @@ require 'digest'
 class HistoryAccess < ActiveSupport::CurrentAttributes
   attribute :user
   class Forbidden < StandardError; end
-  ARTIFACT_POLICY = 'counts-private-predicates-4'.freeze
+  ARTIFACT_POLICY = 'counts-masked-summary-1'.freeze
 
   KEYS = { 'post_versions' => ['post_id'], 'tag_versions' => ['tag_id'],
            'nico_tag_versions' => ['tag_id'],
@@ -59,21 +59,20 @@ class HistoryAccess < ActiveSupport::CurrentAttributes
   end
 
   def self.json_reference(table, key, document)
-    # A scalar lookup avoids MySQL's semijoin rewrite losing the JSON row correlation.
+    "NOT EXISTS (SELECT 1 FROM JSON_TABLE(COALESCE(#{ document }, JSON_ARRAY()), " +
-    "(SELECT 1 FROM JSON_TABLE(COALESCE(#{ document }, JSON_ARRAY()), " +
         "'$[*]' COLUMNS (reference_id BIGINT PATH '$' NULL ON EMPTY)) reference_entry " +
         "JOIN (#{ discarded_keys(table, key) }) blocked " +
-        "ON reference_entry.reference_id = blocked.#{ key } LIMIT 1) IS NULL"
+        "ON reference_entry.reference_id = blocked.#{ key })"
   end
 
   def self.list_reference(table, key, document)
     # Preserve FIND_IN_SET's exact token semantics, including empty tokens.
     array = "CONCAT('[', REPLACE(JSON_QUOTE(REPLACE(COALESCE(#{ document }, ''), " +
         "' ', ',')), ',', '\",\"'), ']')"
-    "(SELECT 1 FROM JSON_TABLE(#{ array }, '$[*]' " +
+    "NOT EXISTS (SELECT 1 FROM JSON_TABLE(#{ array }, '$[*]' " +
         "COLUMNS (reference_id VARCHAR(255) PATH '$')) reference_entry " +
         "JOIN (#{ discarded_keys(table, key) }) blocked " +
-        "ON reference_entry.reference_id = CAST(blocked.#{ key } AS CHAR) LIMIT 1) IS NULL"
+        "ON reference_entry.reference_id = CAST(blocked.#{ key } AS CHAR))"
   end
 
   def self.snapshot_reference(model, row, external: false)
@@ -92,8 +91,8 @@ class HistoryAccess < ActiveSupport::CurrentAttributes
       match += ' AND reference_version.version_no = tag_reference.version_no'
       latest = ''
     end
-    "(SELECT 1 FROM #{ source } JOIN #{ table } reference_version ON #{ match } " +
+    "NOT EXISTS (SELECT 1 FROM #{ source } JOIN #{ table } reference_version ON #{ match } " +
-        "WHERE NOT (#{ sql(model, 'reference_version') }) #{ latest } LIMIT 1) IS NULL"
+        "WHERE NOT (#{ sql(model, 'reference_version') }) #{ latest })"
   end
 
   def self.reference_sql(table, row)
@@ -110,15 +109,11 @@ class HistoryAccess < ActiveSupport::CurrentAttributes
       # conservatively; never expose a private linked name through an external tag.
       names = "JSON_MERGE_PRESERVE(JSON_ARRAY(private_tag.name), " +
           "COALESCE(JSON_EXTRACT(private_tag.names, '$**.name'), JSON_ARRAY()))"
-      # DISTINCT prevents merging this independent name set into the correlated scan.
+      ["NOT EXISTS (SELECT 1 FROM tag_versions private_tag " +
-      # Keep byte-distinct names even when the column collation considers them equal.
-      private_names = 'SELECT DISTINCT private_name.name, ' +
-          'CAST(private_name.name AS BINARY) AS name_bytes FROM tag_versions private_tag ' +
           "JOIN (#{ discarded_keys('tag_versions', 'tag_id') }) blocked " +
-          'ON blocked.tag_id = private_tag.tag_id ' +
+          "ON blocked.tag_id = private_tag.tag_id " +
           "JOIN JSON_TABLE(#{ names }, '$[*]' COLUMNS (name TEXT PATH '$')) private_name " +
-          "WHERE private_name.name <> ''"
+          "WHERE private_name.name <> '' AND " +
-      ["NOT EXISTS (SELECT 1 FROM (#{ private_names }) private_name WHERE " +
           "LOCATE(CONCAT(' ', private_name.name, ' '), " +
           "CONCAT(' ', COALESCE(#{ row }.linked_tags, ''), ' ')) > 0)"]
     when 'tag_versions'

backend/app/models/material_version.rb

@@ -11,7 +11,5 @@ class MaterialVersion < ApplicationRecord
   belongs_to :parent, class_name: 'Material', optional: true
   belongs_to :updated_by_user, class_name: 'User', optional: true
 
-  def export_paths_hash
+  def export_paths_hash = export_paths_json || { }
-    export_paths_json || {}
-  end
 end

backend/app/models/version_record.rb

@@ -19,6 +19,8 @@ module VersionRecord
 
     belongs_to :created_by_user, class_name: 'User', optional: true
 
+    belongs_to :event
+
     enum :event_type, event_type_map, prefix: true, validate: true
 
     validates :version_no, presence: true, numericality: { only_integer: true, greater_than: 0 }

backend/app/services/counts_axes.rb

@@ -1,41 +1,12 @@
 class CountsAxes
   MAX_AXES = 8
-  MASKED_TEXT = '********'.freeze
   MASKED_VALUE = '__counts_private__'.freeze
-  PUBLIC_FIELDS = ['resource_id', 'version_no', 'event_type', 'user',
+  PUBLIC_FIELDS = ['created_at', 'event_type'].freeze
-                   'created_at'].freeze
   class TooManyAxes < ArgumentError; end
   class PrivateCondition < ArgumentError; end
 
   GRAINS = ['year', 'quarter', 'month', 'week', 'day', 'hour'].freeze
 
-  def self.private_field?(field)
-    !PUBLIC_FIELDS.include?(field) && field != 'user.id'
-  end
-
-  def self.visible_ids_sql(definition)
-    "SELECT counts_visible.id FROM #{ definition.table } counts_visible WHERE " +
-        HistoryAccess.sql(definition.model, 'counts_visible')
-  end
-
-  def self.visibility_sql(definition, field)
-    return 'TRUE' if HistoryAccess.admin?
-
-    source = visible_ids_sql(definition)
-    visible = "v.id IN (#{ source })"
-    return visible unless field == 'changed_field'
-
-    "(#{ visible }) AND (previous.id IS NULL OR previous.id IN (#{ source }))"
-  end
-
-  def self.masked_sql(expression, definition, field)
-    return expression if HistoryAccess.admin? || !private_field?(field)
-
-    visible = visibility_sql(definition, field)
-    quoted = ApplicationRecord.connection.quote(MASKED_VALUE)
-    "CASE WHEN #{ visible } THEN #{ expression } ELSE #{ quoted } END"
-  end
-
   def self.time_expression(expression, grain, timezone)
     raise ArgumentError unless GRAINS.include?(grain)
 
@@ -89,9 +60,13 @@ class CountsAxes
         @definition.fields[field] == :datetime ? self.class.time_expression(
             expression, axis.fetch('grain', 'month'), @population.timezone) : expression
       end
-      if !HistoryAccess.admin? && self.class.private_field?(field)
+      if !HistoryAccess.admin? && !PUBLIC_FIELDS.include?(field)
-        expression = self.class.masked_sql(
+        visible = HistoryAccess.sql(@definition.model, 'v')
-            "CAST((#{ expression }) AS CHAR)", @definition, field)
+        if field == 'changed_field'
+          visible = "(#{ visible }) AND (#{ HistoryAccess.sql(@definition.model, 'previous') })"
+        end
+        expression = "CASE WHEN #{ visible } " +
+            "THEN CAST((#{ expression }) AS CHAR) ELSE '#{ MASKED_VALUE }' END"
       end
       expression
     end
@@ -102,12 +77,10 @@ class CountsAxes
     selected = indexes.map { "#{ expressions[_1] } AS a#{ _1 }" }
     identities = ['v.id']
     if rows.any? { _1['field'] == 'tags' }
-      identities << self.class.masked_sql(
+      # Raw identities stay inside COUNT; masked tag occurrences remain additive.
-          "COALESCE(CONCAT('internal:', tag_entry.tag_id), " +
+      identities << "COALESCE(CONCAT('internal:', tag_entry.tag_id), " +
-              "CONCAT('external:', tag_entry.external_tag_id))", @definition, 'tags')
+          "CONCAT('external:', tag_entry.external_tag_id))"
-      if rows.any? { _1['field'] == 'changed_field' }
+      identities << 'changed.field_key' if rows.any? { _1['field'] == 'changed_field' }
-        identities << self.class.masked_sql('changed.field_key', @definition, 'changed_field')
-      end
     end
     members = identities.each_index.map { "counts_member_#{ _1 }" }
     selected += identities.each_with_index.map { |expression, index|
@@ -125,17 +98,8 @@ class CountsAxes
   def joins(fields = all.map { _1['field'] })
     result = ''
     if fields.include?('tags')
-      document = 'CAST(v.tags_json AS JSON)'
-      unless HistoryAccess.admin?
-        visible = self.class.visible_ids_sql(@definition)
-        result += " LEFT JOIN (#{ visible }) counts_tags_visible " +
-            'ON counts_tags_visible.id = v.id '
-        document = "CASE WHEN counts_tags_visible.id IS NOT NULL " +
-            "THEN #{ document } ELSE JSON_ARRAY(" +
-            "JSON_OBJECT('tag_id', 0)) END"
-      end
       result += <<~SQL.squish
-         JOIN JSON_TABLE(#{ document }, '$[*]' COLUMNS (
+         JOIN JSON_TABLE(CAST(v.tags_json AS JSON), '$[*]' COLUMNS (
           tag_id BIGINT PATH '$.tag_id' NULL ON EMPTY,
           external_tag_id BIGINT PATH '$.external_tag_id' NULL ON EMPTY)) tag_entry
 
@@ -148,13 +112,6 @@ class CountsAxes
       condition = @definition.changes.map do |field|
         "(changed.field_key = '#{ field }' AND #{ @population.changed_sql(field) })"
       end.join(' OR ')
-      unless HistoryAccess.admin?
-        visible = self.class.visibility_sql(@definition, 'changed_field')
-        marker = ApplicationRecord.connection.quote(MASKED_VALUE)
-        fields += " UNION ALL SELECT #{ marker } AS field_key"
-        condition = "((#{ visible }) AND (#{ condition })) OR " +
-            "(NOT (#{ visible }) AND changed.field_key = #{ marker })"
-      end
       result += " JOIN (#{ fields }) changed ON (#{ condition })"
     end
     result

backend/app/services/counts_condition.rb

@@ -82,32 +82,14 @@ class CountsCondition
 
   def apply(scope, entry)
     raise ArgumentError unless entry.is_a?(Hash)
-
     if entry['operator'] == 'axis_eq'
       raise ArgumentError unless (entry.keys - ['field', 'operator', 'grain', 'value']).empty?
       value = entry['value']
-      unless (value.nil? || value.is_a?(String) || value.is_a?(Numeric) ||
+      unless value.nil? || value.is_a?(String) || value.is_a?(Numeric) || [true, false].include?(value)
-          [true, false].include?(value))
         raise ArgumentError
       end
       raise ArgumentError if value.is_a?(String) && value.bytesize > 8192
 
-      if (!HistoryAccess.admin? && CountsAxes.private_field?(entry['field']) &&
-          (value == CountsAxes::MASKED_VALUE ||
-              (value == CountsAxes::MASKED_TEXT &&
-                  (@definition.fields[entry['field']] != :string ||
-                      ['tags', 'changed_field'].include?(entry['field'])))))
-        field = entry.fetch('field')
-        raise ArgumentError unless @definition.axes(@population.history).include?(field)
-        if entry.key?('grain')
-          unless (@definition.fields[field] == :datetime &&
-              CountsAxes::GRAINS.include?(entry['grain']))
-            raise ArgumentError
-          end
-        end
-        return scope.none
-      end
-      scope = @population.condition_scope(scope, entry.fetch('field'))
       return @population.axis_condition(scope, entry)
     end
     allowed = ['field', 'operator', 'value', 'end', 'blank', 'input', 'values']
@@ -129,13 +111,6 @@ class CountsCondition
 
     source, expression = source_for(field[:key])
     type = field[:type]
-    # Preserve typed input compatibility; display markers are never real typed values.
-    if (!HistoryAccess.admin? && CountsAxes.private_field?(field[:key]) &&
-        entry['value'] == CountsAxes::MASKED_TEXT && type != :string && !entry['blank'])
-      return scope.none unless entry['operator'] == 'ne'
-
-      return @population.condition_scope(scope, field[:key])
-    end
     blank = blank_sql(expression, type)
     if entry['blank']
       sql = if source && field[:collection]
@@ -144,7 +119,6 @@ class CountsCondition
               "NOT EXISTS (SELECT 1 FROM #{ source } WHERE NOT (#{ blank }))"
             else blank
             end
-      scope = @population.condition_scope(scope, field[:key])
       return scope.where(Arel.sql(sql))
     end
     if ['in', 'not_in', 'any', 'all', 'none'].include?(entry['operator'])
@@ -157,7 +131,6 @@ class CountsCondition
     validate_enum!(field[:key], parsed.first) if type == :enum
     operator = entry['operator']
     if type == :interval
-      scope = @population.condition_scope(scope, field[:key])
       return interval(scope, source, expression, parsed)
     end
     clauses = []
@@ -185,7 +158,6 @@ class CountsCondition
     elsif operator == 'ne'
       predicate = "(NOT (#{ predicate }) OR #{ blank })"
     end
-    scope = @population.condition_scope(scope, field[:key])
     scope.where(predicate, *binds)
   end
 
@@ -196,13 +168,6 @@ class CountsCondition
 
     values = entry['values']
     raise ArgumentError unless values.is_a?(Array) && values.length <= 100
-    if (!HistoryAccess.admin? && CountsAxes.private_field?(field[:key]) &&
-        values.include?(CountsAxes::MASKED_TEXT) &&
-        (field[:type] != :string || field[:set_type] == 'tag_reference'))
-      return scope.none if entry['operator'] == 'all'
-
-      values = values - [CountsAxes::MASKED_TEXT]
-    end
     raise ArgumentError if [entry['value'], entry['end']].any? { !_1.nil? && _1 != '' }
 
     parsed = values.map do |value|
@@ -226,10 +191,7 @@ class CountsCondition
 
     operator = entry['operator']
     if parsed.empty?
-      return scope.none if ['in', 'any'].include?(operator)
+      return ['in', 'any'].include?(operator) ? scope.none : scope
-      return scope if entry['values'].empty?
-
-      return @population.condition_scope(scope, field[:key])
     end
     source, expression = source_for(field[:key])
     if field[:set_type] == 'tag_reference'
@@ -250,7 +212,6 @@ class CountsCondition
       predicate = source ? "NOT #{ predicate }" :
           "(NOT #{ predicate } OR #{ blank_sql(expression, field[:type]) })"
     end
-    scope = @population.condition_scope(scope, field[:key])
     scope.where(predicate, *parsed)
   end
 

backend/app/services/counts_population.rb

@@ -70,13 +70,6 @@ class CountsPopulation
     @authorisation_flg ? HistoryAccess.sql(model, row) : 'TRUE'
   end
 
-  # Each predicate keeps its own visibility restriction, including OR branches.
-  def condition_scope(scope, field)
-    return scope if HistoryAccess.admin? || !CountsAxes.private_field?(field)
-
-    scope.where(Arel.sql(CountsAxes.visibility_sql(definition, field)))
-  end
-
   def axis_condition(scope, entry)
     raise CountsAxes::PrivateCondition if entry['value'] == CountsAxes::MASKED_VALUE
 
@@ -216,7 +209,6 @@ class CountsPopulation
   def apply_tags
     raise ArgumentError unless definition.resource == 'posts'
 
-    @scope = condition_scope(@scope, 'tags')
     if params['tag'].present?
       @scope = @scope.where(snapshot_membership(
           "#{ params.fetch('kind', 'internal') }:#{ params['tag'] }"))

backend/app/services/counts_table_export.rb

@@ -253,7 +253,7 @@ class CountsTableExport
   end
 
   def summary_value(value, index, page)
-    return CountsAxes::MASKED_TEXT if value == CountsAxes::MASKED_VALUE
+    return '********' if value == CountsAxes::MASKED_VALUE
 
     field = @query.axes.all.fetch(index).fetch('field')
     return @labels.fetch('bot', '') if field == 'user' && value.nil?

backend/app/services/counts_table_query.rb

@@ -220,11 +220,19 @@ class CountsTableQuery
 
   private
 
-  # Private predicates require visibility independently of their operator.
+  # Public timeline predicates may include hidden records. Private predicates must
-  # Ordering/measure state must not select a server-only masked coordinate.
+  # never become a count oracle, even when the selected axes themselves are public.
   def validate_summary_conditions!
     return if mode != 'summary' || HistoryAccess.admin?
 
+    fields = QueryState.records(@params, 'conditions') + QueryState.records(@params, 'drill')
+    private_fields = fields.any? { !CountsAxes::PUBLIC_FIELDS.include?(_1['field']) }
+    keys = ['tags', 'tag', 'kind', 'resource_id', 'user_id']
+    private_parameters = keys.any? do |key|
+      @params.any? { |name, value| (name == key || name.start_with?("#{ key }.")) && value != '' }
+    end
+    raise CountsAxes::PrivateCondition if private_fields || private_parameters
+
     ['column_order', 'measures'].each do |key|
       # Coordinates are compared only to already masked expressions, never raw
       # values. Public coordinates remain sortable; a guessed private ID cannot match.

backend/app/services/material_version_recorder.rb

@@ -1,20 +1,23 @@
 class MaterialVersionRecorder < VersionRecorder
   EVENT_TYPES = ['create', 'update', 'discard', 'restore'].freeze
 
-  def self.record! material:, event_type:, created_by_user:, file_snapshot: nil
+  def self.record! material:, event_type:, event:, created_by_user:, file_snapshot: nil
-    new(material:, event_type:, created_by_user:, file_snapshot:).record!
+    new(material:, event_type:, event:, created_by_user:, file_snapshot:).record!
   end
 
-  def initialize material:, event_type:, created_by_user:, file_snapshot: nil
+  def initialize material:, event_type:, event:, created_by_user:, file_snapshot: nil
     @file_snapshot = file_snapshot
 
-    super(record: material, event_type:, created_by_user:)
+    super(record: material, event_type:, event:, created_by_user:)
   end
 
   def self.ensure_snapshot! material, created_by_user:
     return if material.material_versions.exists?
 
-    record!(material:, event_type: :create,
+    event = Event.create!(event_type: 'materials.create',
+                          created_by_user:,
+                          created_at: material.created_at)
+    record!(material:, event_type: :create, event:,
             created_by_user: material.created_by_user || created_by_user)
   end
 

backend/app/services/post_version_recorder.rb

@@ -1,16 +1,19 @@
 class PostVersionRecorder < VersionRecorder
-  def self.record! post:, event_type:, created_by_user:
+  def self.record! post:, event_type:, event:, created_by_user:
-    new(post:, event_type:, created_by_user:).record!
+    new(post:, event_type:, event:, created_by_user:).record!
   end
 
-  def initialize post:, event_type:, created_by_user:
+  def initialize post:, event_type:, event:, created_by_user:
-    super(record: post, event_type:, created_by_user:)
+    super(record: post, event_type:, event:, created_by_user:)
   end
 
   def self.ensure_snapshot! post, created_by_user:
     return if post.post_versions.exists?
 
-    record!(post:, event_type: :create, created_by_user:)
+    event = Event.create!(event_type: 'posts.create',
+                          created_by_user:,
+                          created_at: post.created_at)
+    record!(post:, event_type: :create, event:, created_by_user:)
   end
 
   private

backend/app/services/tag_version_recorder.rb

@@ -1,13 +1,13 @@
 class TagVersionRecorder < VersionRecorder
-  def self.record! tag:, event_type:, created_by_user:, **_options
+  def self.record! tag:, event_type:, event:, created_by_user:, **_options
     Tag.transaction do
       SharedResourceIdAllocator.lock_space!(Tag, 'tags')
-      new(tag:, event_type:, created_by_user:).record!
+      new(tag:, event_type:, event:, created_by_user:).record!
     end
   end
 
-  def initialize tag:, event_type:, created_by_user:
+  def initialize tag:, event_type:, event:, created_by_user:
-    super(record: tag, event_type:, created_by_user:)
+    super(record: tag, event_type:, event:, created_by_user:)
   end
 
   private

backend/app/services/version_recorder.rb

@@ -1,9 +1,10 @@
 class VersionRecorder
   EVENT_TYPES = ['create', 'update', 'discard', 'restore'].freeze
 
-  def initialize record:, event_type:, created_by_user:
+  def initialize record:, event_type:, event:, created_by_user:
     @record = record
     @event_type = event_type.to_s
+    @event = event
     @created_by_user = created_by_user
 
     validate_event_type!
@@ -42,8 +43,9 @@ class VersionRecorder
   def base_attributes latest
     { version_no: (latest&.version_no || 0) + 1,
       event_type: @event_type,
-      created_at: Time.current,
+      event: @event,
-      created_by_user: @created_by_user }
+      created_by_user: @created_by_user,
+      created_at: Time.current }
   end
 
   def update_record_version_no! version_no

backend/db/migrate/20261102000000_create_events.rb

@@ -0,0 +1,19 @@
+class CreateEvents < ActiveRecord::Migration[8.0]
+  def change
+    create_table :events do |t|
+      t.string :event_type, null: false, index: true
+      t.text :reason
+      t.references :reverted_from_event, foreign_key: { to_table: :events }
+      t.json :metadata
+      t.binary :ip_address, limit: 16, index: true
+      t.references :created_by_user, index: true, foreign_key: false
+      t.datetime :created_at, null: false, index: true
+    end
+
+    add_reference :post_versions, :event, foreign_key: true, after: :original_created_before
+    add_reference :tag_versions, :event, foreign_key: true, after: :deprecated_at
+    add_reference :material_versions, :event, foreign_key: true
+    add_reference :tag_description_versions, :event, foreign_key: true, after: :source_version_no
+    add_reference :tag_group_versions, :event, foreign_key: true, after: :placements
+  end
+end

backend/db/migrate/20261102010000_backfill_events_from_existing_versions.rb

@@ -0,0 +1,207 @@
+class BackfillEventsFromExistingVersions < ActiveRecord::Migration[8.0]
+  class MigrationEvent < ActiveRecord::Base
+    self.table_name = 'events'
+  end
+
+  class MigrationPostVersion < ActiveRecord::Base
+    self.table_name = 'post_versions'
+  end
+
+  class MigrationTagVersion < ActiveRecord::Base
+    self.table_name = 'tag_versions'
+  end
+
+  class MigrationMaterialVersion < ActiveRecord::Base
+    self.table_name = 'material_versions'
+  end
+
+  class MigrationTagDescriptionVersion < ActiveRecord::Base
+    self.table_name = 'tag_description_versions'
+  end
+
+  class MigrationTagGroupVersion < ActiveRecord::Base
+    self.table_name = 'tag_group_versions'
+  end
+
+  class MigrationLocale < ActiveRecord::Base
+    self.table_name = 'locales'
+  end
+
+  def up
+    # create → posts.create
+    # update → posts.update
+    raise if MigrationPostVersion.where.not(event_type: ['create', 'update']).exists?
+
+    # create → materials.create
+    # update → materials.update
+    if MigrationMaterialVersion.where.not(event_type: ['create', 'update']).exists?
+      raise
+    end
+
+    # create → posts.create / posts.update / materials.create / materials.update / unknown
+    # update → tags.update / locales.create
+    # discard → unknown
+    if MigrationTagVersion.where.not(event_type: ['create', 'update', 'discard']).exists?
+      raise
+    end
+
+    # create → tag_descriptions.create
+    # update → tag_descriptions.update
+    if MigrationTagDescriptionVersion.where.not(event_type: ['create', 'update']).exists?
+      raise
+    end
+
+    # create → tag_groups.create
+    # update → tag_groups.update
+    if MigrationTagGroupVersion.where.not(event_type: ['create', 'update']).exists?
+      raise
+    end
+
+    # post_versions の Backfill
+    MigrationPostVersion.find_each do |pv|
+      ev = MigrationEvent.create!(event_type: "posts.#{ pv.event_type }",
+                                  reason: nil,
+                                  reverted_from_event_id: nil,
+                                  metadata: nil,
+                                  ip_address: nil,
+                                  created_by_user_id: pv.created_by_user_id,
+                                  created_at: pv.created_at)
+      pv.update_columns(event_id: ev.id)
+    end
+
+    # material_versions の Backfill
+    MigrationMaterialVersion.find_each do |m|
+      ev = MigrationEvent.create!(event_type: "materials.#{ m.event_type }",
+                                  reason: nil,
+                                  reverted_from_event_id: nil,
+                                  metadata: nil,
+                                  ip_address: nil,
+                                  created_by_user_id: m.created_by_user_id,
+                                  created_at: m.created_at)
+      m.update_columns(event_id: ev.id)
+    end
+
+    # ロカール追加に伴ふ該当語言のタグ名称追加異動のみ分離
+    ids_cause_of_locale_creation = []
+    MigrationLocale.where('created_at > ?', MigrationLocale.minimum(:created_at)).find_each do |l|
+      ev = MigrationEvent.create!(event_type: 'locales.create',
+                                  reason: nil,
+                                  reverted_from_event_id: nil,
+                                  metadata: nil,
+                                  ip_address: nil,
+                                  created_by_user_id: nil,
+                                  created_at: l.created_at)
+
+      MigrationTagVersion
+          .where('created_at > ?', l.created_at)
+          .where(event_type: 'update', event_id: nil)
+          .find_each do |t|
+        next unless t.names.key?(l.language_code)
+
+        prev = MigrationTagVersion.find_by(tag_id: t.tag_id, version_no: t.version_no - 1)
+        next if prev.nil? || prev.names.key?(l.language_code)
+
+        t.update_columns(event_id: ev.id)
+
+        ids_cause_of_locale_creation << t.id
+      end
+
+      ev.destroy! unless MigrationTagVersion.where(event_id: ev.id).exists?
+    end
+
+    # tag_versions の Backfill
+    MigrationTagVersion.where.not(id: ids_cause_of_locale_creation).find_each do |t|
+      ev =
+          case t.event_type
+          when 'create'
+            post =
+                MigrationPostVersion
+                .where('JSON_CONTAINS(tags_json, ?) <> 0', { tag_id: t.tag_id }.to_json)
+                .find_by(created_at: MigrationPostVersion
+                                     .where('JSON_CONTAINS(tags_json, ?) <> 0',
+                                            { tag_id: t.tag_id }.to_json)
+                                     .minimum(:created_at))
+            material =
+                MigrationMaterialVersion
+                .where(tag_id: t.tag_id)
+                .find_by(created_at: MigrationMaterialVersion
+                                     .where(tag_id: t.tag_id)
+                                     .minimum(:created_at))
+            if post
+              if material
+                if post.created_at < material.created_at
+                  MigrationEvent.find(post.event_id)
+                else
+                  MigrationEvent.find(material.event_id)
+                end
+              else
+                MigrationEvent.find(post.event_id)
+              end
+            else
+              if material
+                MigrationEvent.find(material.event_id)
+              else
+                MigrationEvent.create!(event_type: 'unknown',
+                                       reason: nil,
+                                       reverted_from_event_id: nil,
+                                       metadata: nil,
+                                       ip_address: nil,
+                                       created_by_user_id: t.created_by_user_id,
+                                       created_at: t.created_at)
+              end
+            end
+          when 'update'
+            MigrationEvent.create!(event_type: 'tags.update',
+                                   reason: nil,
+                                   reverted_from_event_id: nil,
+                                   metadata: nil,
+                                   ip_address: nil,
+                                   created_by_user_id: t.created_by_user_id,
+                                   created_at: t.created_at)
+          when 'discard'
+            MigrationEvent.create!(event_type: 'unknown',
+                                   reason: nil,
+                                   reverted_from_event_id: nil,
+                                   metadata: nil,
+                                   ip_address: nil,
+                                   created_by_user_id: t.created_by_user_id,
+                                   created_at: t.created_at)
+          end
+      t.update_columns(event_id: ev.id)
+    end
+
+    # tag_description_versions の Backfill
+    MigrationTagDescriptionVersion.find_each do |td|
+      ev = MigrationEvent.create!(event_type: "tag_descriptions.#{ td.event_type }",
+                                  reason: nil,
+                                  reverted_from_event_id: nil,
+                                  metadata: nil,
+                                  ip_address: nil,
+                                  created_by_user_id: td.created_by_user_id,
+                                  created_at: td.created_at)
+      td.update_columns(event_id: ev.id)
+    end
+
+    # tag_group_versions の Backfill
+    MigrationTagGroupVersion.find_each do |tg|
+      ev = MigrationEvent.create!(event_type: "tag_groups.#{ tg.event_type }",
+                                  reason: nil,
+                                  reverted_from_event_id: nil,
+                                  metadata: nil,
+                                  ip_address: nil,
+                                  created_by_user_id: tg.created_by_user_id,
+                                  created_at: tg.created_at)
+      tg.update_columns(event_id: ev.id)
+    end
+
+    change_column_null :post_versions, :event_id, false
+    change_column_null :tag_versions, :event_id, false
+    change_column_null :material_versions, :event_id, false
+    change_column_null :tag_description_versions, :event_id, false
+    change_column_null :tag_group_versions, :event_id, false
+  end
+
+  def down
+    raise ActiveRecord::IrreversibleMigration, '戻せません．'
+  end
+end

backend/db/schema.rb

@@ -10,7 +10,7 @@
 #
 # It's strongly recommended that you check this file into your version control system.
 
-ActiveRecord::Schema[8.0].define(version: 2026_10_15_010000) do
+ActiveRecord::Schema[8.0].define(version: 2026_11_02_010000) do
   create_table "active_storage_attachments", charset: "utf8mb4", collation: "utf8mb4_0900_ai_ci", force: :cascade do |t|
     t.string "name", null: false
     t.string "record_type", null: false
@@ -48,6 +48,21 @@ ActiveRecord::Schema[8.0].define(version: 2026_10_15_010000) do
     t.index ["tag_id"], name: "index_deerjikists_on_tag_id"
   end
 
+  create_table "events", charset: "utf8mb4", collation: "utf8mb4_0900_ai_ci", force: :cascade do |t|
+    t.string "event_type", null: false
+    t.text "reason"
+    t.bigint "reverted_from_event_id"
+    t.json "metadata"
+    t.binary "ip_address", limit: 16
+    t.bigint "created_by_user_id"
+    t.datetime "created_at", null: false
+    t.index ["created_at"], name: "index_events_on_created_at"
+    t.index ["created_by_user_id"], name: "index_events_on_created_by_user_id"
+    t.index ["event_type"], name: "index_events_on_event_type"
+    t.index ["ip_address"], name: "index_events_on_ip_address"
+    t.index ["reverted_from_event_id"], name: "index_events_on_reverted_from_event_id"
+  end
+
   create_table "external_tags", charset: "utf8mb4", collation: "utf8mb4_0900_ai_ci", force: :cascade do |t|
     t.string "platform", limit: 16, null: false
     t.string "name", null: false
@@ -250,8 +265,10 @@ ActiveRecord::Schema[8.0].define(version: 2026_10_15_010000) do
     t.string "source_path"
     t.string "source_file_id"
     t.string "normalized_source_key"
+    t.bigint "event_id", null: false
     t.index ["created_by_user_id"], name: "index_material_versions_on_created_by_user_id"
     t.index ["discarded_at"], name: "index_material_versions_on_discarded_at"
+    t.index ["event_id"], name: "index_material_versions_on_event_id"
     t.index ["file_blob_id"], name: "index_material_versions_on_file_blob_id"
     t.index ["material_id", "version_no"], name: "index_material_versions_on_material_id_and_version_no", unique: true
     t.index ["material_id"], name: "index_material_versions_on_material_id"
@@ -380,10 +397,12 @@ ActiveRecord::Schema[8.0].define(version: 2026_10_15_010000) do
     t.text "parent_post_ids", null: false
     t.datetime "original_created_from"
     t.datetime "original_created_before"
+    t.bigint "event_id", null: false
     t.datetime "created_at", null: false
     t.bigint "created_by_user_id"
     t.integer "video_ms"
     t.index ["created_by_user_id"], name: "index_post_versions_on_created_by_user_id"
+    t.index ["event_id"], name: "index_post_versions_on_event_id"
     t.index ["post_id", "version_no"], name: "index_post_versions_on_post_id_and_version_no", unique: true
     t.index ["post_id"], name: "index_post_versions_on_post_id"
     t.index ["video_ms", "post_id"], name: "idx_post_versions_video_ms_post_id"
@@ -448,9 +467,11 @@ ActiveRecord::Schema[8.0].define(version: 2026_10_15_010000) do
     t.text "body", null: false
     t.string "source_language_code", limit: 16
     t.integer "source_version_no"
+    t.bigint "event_id", null: false
     t.bigint "created_by_user_id"
     t.datetime "created_at", null: false
     t.index ["created_by_user_id"], name: "index_tag_description_versions_on_created_by_user_id"
+    t.index ["event_id"], name: "index_tag_description_versions_on_event_id"
     t.index ["tag_id", "language_code", "version_no"], name: "idx_on_tag_id_language_code_version_no_ced77e57e6", unique: true
     t.index ["tag_id", "source_language_code", "source_version_no"], name: "fk_rails_4f13094dbc"
     t.index ["tag_id"], name: "index_tag_description_versions_on_tag_id"
@@ -533,9 +554,11 @@ ActiveRecord::Schema[8.0].define(version: 2026_10_15_010000) do
     t.text "description"
     t.json "members", null: false
     t.json "placements", null: false
+    t.bigint "event_id", null: false
     t.bigint "created_by_user_id"
     t.datetime "created_at", null: false
     t.index ["created_by_user_id"], name: "index_tag_group_versions_on_created_by_user_id"
+    t.index ["event_id"], name: "index_tag_group_versions_on_event_id"
     t.index ["tag_group_id", "version_no"], name: "index_tag_group_versions_on_tag_group_id_and_version_no", unique: true
     t.index ["tag_group_id"], name: "index_tag_group_versions_on_tag_group_id"
     t.check_constraint "`version_no` > 0", name: "chk_tag_group_versions_version_no_positive"
@@ -611,11 +634,13 @@ ActiveRecord::Schema[8.0].define(version: 2026_10_15_010000) do
     t.text "aliases", null: false
     t.text "parent_tag_ids", null: false
     t.datetime "deprecated_at"
+    t.bigint "event_id", null: false
     t.datetime "created_at", null: false
     t.bigint "created_by_user_id"
     t.json "names", null: false
     t.index ["created_at"], name: "index_tag_versions_on_created_at"
     t.index ["created_by_user_id", "created_at"], name: "index_tag_versions_on_created_by_user_id_and_created_at", order: { created_at: :desc }
+    t.index ["event_id"], name: "index_tag_versions_on_event_id"
     t.index ["tag_id", "created_at"], name: "index_tag_versions_on_tag_id_and_created_at", order: { created_at: :desc }
     t.index ["tag_id", "version_no"], name: "index_tag_versions_on_tag_id_and_version_no", unique: true
     t.check_constraint "`version_no` > 0", name: "tag_versions_version_no_positive"
@@ -771,6 +796,7 @@ ActiveRecord::Schema[8.0].define(version: 2026_10_15_010000) do
 
   add_foreign_key "active_storage_attachments", "active_storage_blobs", column: "blob_id"
   add_foreign_key "active_storage_variant_records", "active_storage_blobs", column: "blob_id"
+  add_foreign_key "events", "events", column: "reverted_from_event_id"
   add_foreign_key "gekanator_ai_runs", "gekanator_question_suggestions"
   add_foreign_key "gekanator_games", "posts", column: "correct_post_id"
   add_foreign_key "gekanator_games", "posts", column: "guessed_post_id"
@@ -792,6 +818,7 @@ ActiveRecord::Schema[8.0].define(version: 2026_10_15_010000) do
   add_foreign_key "material_sync_sources", "users", column: "created_by_user_id"
   add_foreign_key "material_sync_sources", "users", column: "updated_by_user_id"
   add_foreign_key "material_sync_suppressions", "users", column: "created_by_user_id"
+  add_foreign_key "material_versions", "events"
   add_foreign_key "material_versions", "materials"
   add_foreign_key "material_versions", "materials", column: "parent_id"
   add_foreign_key "material_versions", "users", column: "created_by_user_id"
@@ -813,10 +840,12 @@ ActiveRecord::Schema[8.0].define(version: 2026_10_15_010000) do
   add_foreign_key "post_tags", "posts"
   add_foreign_key "post_tags", "tags"
   add_foreign_key "post_tags", "users", column: "created_user_id"
+  add_foreign_key "post_versions", "events"
   add_foreign_key "post_versions", "posts"
   add_foreign_key "post_versions", "users", column: "created_by_user_id"
   add_foreign_key "posts", "users", column: "uploaded_user_id"
   add_foreign_key "settings", "users"
+  add_foreign_key "tag_description_versions", "events"
   add_foreign_key "tag_description_versions", "tag_description_versions", column: ["tag_id", "source_language_code", "source_version_no"], primary_key: ["tag_id", "language_code", "version_no"]
   add_foreign_key "tag_descriptions", "languages", column: "language_code", primary_key: "code"
   add_foreign_key "tag_descriptions", "tag_description_versions", column: ["tag_id", "source_language_code", "source_version_no"], primary_key: ["tag_id", "language_code", "version_no"]
@@ -835,6 +864,7 @@ ActiveRecord::Schema[8.0].define(version: 2026_10_15_010000) do
   add_foreign_key "tag_group_tags", "tag_groups"
   add_foreign_key "tag_group_tags", "tags"
   add_foreign_key "tag_group_tags", "users", column: "created_by_user_id"
+  add_foreign_key "tag_group_versions", "events"
   add_foreign_key "tag_groups", "users", column: "created_by_user_id"
   add_foreign_key "tag_groups", "users", column: "updated_by_user_id"
   add_foreign_key "tag_implications", "tags"
@@ -844,6 +874,7 @@ ActiveRecord::Schema[8.0].define(version: 2026_10_15_010000) do
   add_foreign_key "tag_names", "tags"
   add_foreign_key "tag_similarities", "tags"
   add_foreign_key "tag_similarities", "tags", column: "target_tag_id"
+  add_foreign_key "tag_versions", "events"
   add_foreign_key "tag_versions", "users", column: "created_by_user_id"
   add_foreign_key "theatre_comments", "theatres"
   add_foreign_key "theatre_comments", "users"

backend/db/seeds.rb

@@ -9,21 +9,8 @@
 #   end
 
 ApplicationRecord.transaction do
-  Language.find_or_create_by!(code: 'ja') { _1.name = '日本語' }
+  Language.find_or_create_by!(code: 'ain') { _1.name = 'ain' }
-  Script.find_or_create_by!(code: 'Jpan') { _1.name = '漢字、仮名文字およびラテン文字' }
+  Script.find_or_create_by!(code: 'Kana') { _1.name = 'Kana' }
-  Region.find_or_create_by!(code: 392) do
-    _1.alpha_code = 'JP'
-    _1.name = '日本国'
-  end
-  Locale.find_or_create_by!(code: 'ja') do
-    _1.language_code = 'ja'
-    _1.script_code = 'Jpan'
-    _1.region_code = 392
-    _1.name = '日本語'
-  end
-
-  Language.find_or_create_by!(code: 'ain') { _1.name = 'ヤウンモシルン　アイヌ　イタㇰ' }
-  Script.find_or_create_by!(code: 'Kana') { _1.name = 'カナモジ　オヨビ　ラテンモジ' }
 end
 
 post_url_sanitisation_rules = [

backend/spec/db/tag_group_constraints_spec.rb

@@ -102,6 +102,7 @@ RSpec.describe 'Tag group persistence constraints' do
     6.times { nodes = [{ 'tag_id' => tag.id, 'children' => nodes }] }
     reject_statement do
       insert_group_row('tag_group_versions', {
+          event_id: create_event!(event_type: 'unknown').id,
           tag_group_id: group_id, version_no: 2, event_type: 'update', name: '制約確認',
           members: [{ 'tag_id' => tag.id, 'version_no' => tag.version_no }].to_json,
           placements: nodes.to_json, created_at: Time.current })

backend/spec/db/tag_version_names_spec.rb

@@ -10,6 +10,7 @@ RSpec.describe 'TagVersion names database constraint' do
 
   def insert_snapshot!(snapshot)
     TagVersion.insert_all!([{ tag_id: tag.id, version_no: 1, event_type: 'create',
+                             event_id: create_event!(event_type: 'unknown').id,
                              name: 'snapshot_name', category: 'general',
                              aliases: '', parent_tag_ids: '', names: snapshot,
                              created_at: Time.current }])

backend/spec/models/history_access_spec.rb

@@ -9,7 +9,9 @@ RSpec.describe HistoryAccess do
     locale
     rows = ['ja', 'ain'].flat_map do |language|
       ['create', 'discard', 'restore'].each_with_index.map do |event, index|
-        TagDescriptionVersion.create!(tag_id: tag.id, language_code: language,
+        TagDescriptionVersion.create!(
+            event_id: create_event!(event_type: 'unknown').id,
+            tag_id: tag.id, language_code: language,
             version_no: index + 1, event_type: language == 'ain' ? 'update' : event,
             body: "#{ language } #{ index }", created_at: Time.utc(2024))
       end
@@ -28,7 +30,9 @@ RSpec.describe HistoryAccess do
     public_metadata = described_class.set(user: nil) { described_class.authority }
     admin = create(:user, :admin)
     admin_metadata = described_class.set(user: admin) { described_class.authority }
-    TagVersion.create!(tag:, version_no: 1, event_type: 'discard', name: 'private',
+    TagVersion.create!(
+        event_id: create_event!(event_type: 'unknown').id,
+        tag:, version_no: 1, event_type: 'discard', name: 'private',
         category: 'general',
         names: { ja: { name: 'private', script_code: 'Jpan',
                        auto_generated: false, aliases: [] } },
@@ -52,7 +56,9 @@ RSpec.describe HistoryAccess do
     blob = ActiveStorage::Blob.create_before_direct_upload!(filename: 'private.png',
         byte_size: 1, checksum: Base64.strict_encode64('checksum'), content_type: 'image/png')
     ActiveStorage::Attachment.create!(name: 'thumbnail', record: post, blob:)
-    PostVersion.create!(post:, version_no: 1, event_type: 'discard', url: post.url,
+    PostVersion.create!(
+        event_id: create_event!(event_type: 'unknown').id,
+        post:, version_no: 1, event_type: 'discard', url: post.url,
         title: 'private', tags: '', tags_json: [], parent_post_ids: '', created_at: Time.utc(2024))
     variant = ActiveStorage::VariantRecord.create!(blob:, variation_digest: 'spec-variation')
     derived = ActiveStorage::Blob.create_before_direct_upload!(filename: 'derived.png',
@@ -78,7 +84,9 @@ RSpec.describe 'Counts artifact policy and external references' do
 
   it 'does not expose a private linked tag name through an external history snapshot' do
     tag = create(:tag, primary_name: 'private-linked-name')
-    TagVersion.create!(tag:, version_no: 1, event_type: 'discard', name: 'private-linked-name',
+    TagVersion.create!(
+        event_id: create_event!(event_type: 'unknown').id,
+        tag:, version_no: 1, event_type: 'discard', name: 'private-linked-name',
         category: 'general', aliases: '', parent_tag_ids: '', created_at: Time.utc(2024),
         names: { ja: { name: 'private-linked-name', script_code: 'Jpan',
                        auto_generated: false, aliases: [] } })
@@ -87,7 +95,9 @@ RSpec.describe 'Counts artifact policy and external references' do
         name: 'nico:public-external', linked_tags: 'private-linked-name',
         created_at: Time.utc(2024))
     post = create(:post)
-    snapshot = PostVersion.create!(post:, version_no: 1, event_type: 'create',
+    snapshot = PostVersion.create!(
+        event_id: create_event!(event_type: 'unknown').id,
+        post:, version_no: 1, event_type: 'create',
         title: 'external reference', url: post.url, tags: '',
         tags_json: [{ external_tag_id: external.id }], parent_post_ids: '',
         created_at: Time.utc(2024, 2))
@@ -112,13 +122,17 @@ RSpec.describe 'Counts artifact policy and external references' do
     child = create(:tag, primary_name: 'referencing child')
     [[parent, 'discard', '', 'private parent'],
      [child, 'create', parent.id.to_s, 'referencing child']].each do |tag, event, parents, name|
-      TagVersion.create!(tag:, version_no: 1, event_type: event, name:,
+      TagVersion.create!(
+          event_id: create_event!(event_type: 'unknown').id,
+          tag:, version_no: 1, event_type: event, name:,
           category: 'general', aliases: '', parent_tag_ids: parents, created_at: Time.utc(2023),
           names: { ja: { name:, script_code: 'Jpan',
                          auto_generated: false, aliases: [] } })
     end
     post = create(:post)
-    row = PostVersion.create!(post:, version_no: 1, event_type: 'create', title: 'snapshot',
+    row = PostVersion.create!(
+        event_id: create_event!(event_type: 'unknown').id,
+        post:, version_no: 1, event_type: 'create', title: 'snapshot',
         url: post.url, tags: '', parent_post_ids: '',
         tags_json: [{ tag_id: child.id, version_no: 1, name: 'referencing child', sections: [] }],
         created_at: Time.utc(2024))

backend/spec/models/locale_activation_spec.rb

@@ -23,9 +23,22 @@ RSpec.describe 'Locale activation', type: :model do
         .and_raise('backfill failed')
   end
 
+  it 'groups all tag histories from locale creation into one event' do
+    previous_ids = TagVersion.pluck(:id)
+
+    expect { build_locale.save! }.to change { event_rows.length }.by(1)
+
+    event = event_rows.last
+    expect(event).to include('event_type' => 'locales.create', 'created_by_user_id' => nil)
+    versions = TagVersion.where.not(id: previous_ids)
+    expect(versions.pluck(:tag_id)).to include(first.id, second.id)
+    expect(versions.pluck(:event_id).uniq).to eq([event.fetch('id')])
+  end
+
   it 'rolls back a newly created locale and the preceding generated names' do
     locale = build_locale
     fail_second_generation!
+    events = event_rows
 
     expect { locale.save! }.to raise_error('backfill failed')
 
@@ -33,6 +46,7 @@ RSpec.describe 'Locale activation', type: :model do
     expect(generated_names).to be_empty
     expect(first.reload.name('ja')).to eq('activation_first')
     expect(second.reload.name('ja')).to eq('activation_second')
+    expect(event_rows).to eq(events)
   end
 
   it 'does not backfill while the locale is inactive' do
@@ -45,7 +59,14 @@ RSpec.describe 'Locale activation', type: :model do
     locale = build_locale(deprecated_at: Time.current)
     locale.save!
 
-    locale.update!(deprecated_at: nil)
+    previous_ids = TagVersion.pluck(:id)
+    expect { locale.update!(deprecated_at: nil) }.to change { event_rows.length }.by(1)
+
+    event = event_rows.last
+    expect(event).to include('event_type' => 'locales.restore', 'created_by_user_id' => nil)
+    versions = TagVersion.where.not(id: previous_ids)
+    expect(versions.pluck(:tag_id)).to include(first.id, second.id)
+    expect(versions.pluck(:event_id).uniq).to eq([event.fetch('id')])
 
     expect(generated_names.pluck(:tag_id)).to contain_exactly(first.id, second.id)
     expect(generated_names).to all(have_attributes(
@@ -57,11 +78,13 @@ RSpec.describe 'Locale activation', type: :model do
     locale.save!
     previous_deprecated_at = locale.reload.deprecated_at
     fail_second_generation!
+    events = event_rows
 
     expect { locale.update!(deprecated_at: nil) }.to raise_error('backfill failed')
 
     expect(locale.reload.deprecated_at).to eq(previous_deprecated_at)
     expect(generated_names).to be_empty
+    expect(event_rows).to eq(events)
   end
 
   it 'preserves a human primary through deactivation and repeated activation' do

backend/spec/models/post_version_spec.rb

@@ -12,6 +12,7 @@ RSpec.describe PostVersion, type: :model do
 
   let!(:post_version) do
     PostVersion.create!(
+        event_id: create_event!(event_type: 'unknown').id,
         post: post_record,
         version_no: 1,
         event_type: 'create',
@@ -24,8 +25,7 @@ RSpec.describe PostVersion, type: :model do
         original_created_from: post_record.original_created_from,
         original_created_before: post_record.original_created_before,
         created_at: Time.current,
-      created_by_user: nil
+        created_by_user: nil)
-    )
   end
 
   it 'is read only after create' do

backend/spec/models/tag_name_sanitisation_rule_spec.rb

@@ -34,6 +34,31 @@ RSpec.describe TagNameSanitisationRule, type: :model do
       described_class.create!(priority: 10, source_pattern: 'foo_', replacement: 'foo')
     end
 
+    it 'groups renames, merges and affected post histories into one event' do
+      target = create(:tag, primary_name: 'foobar')
+      source = create(:tag, primary_name: 'temporary_source')
+      renamed = create(:tag, primary_name: 'temporary_rename')
+      source.tag_name('ja').update_columns(name: 'foo_bar')
+      renamed.tag_name('ja').update_columns(name: 'foo_baz')
+      post = create(:post)
+      PostTag.create!(post:, tag: source)
+      previous_tag_ids = TagVersion.pluck(:id)
+      previous_post_ids = PostVersion.pluck(:id)
+
+      expect { described_class.apply! }.to change { event_rows.length }.by(1)
+
+      event = event_rows.last
+      expect(event).to include(
+          'event_type' => 'tag_name_sanitisation_rules.apply', 'created_by_user_id' => nil)
+      tag_versions = TagVersion.where.not(id: previous_tag_ids)
+      expect(tag_versions.pluck(:tag_id).uniq).to contain_exactly(target.id, source.id, renamed.id)
+      expect(tag_versions.pluck(:event_type)).to include('discard', 'update')
+      expect(tag_versions.pluck(:event_id).uniq).to eq([event.fetch('id')])
+      post_versions = PostVersion.where.not(id: previous_post_ids)
+      expect(post_versions.pluck(:post_id).uniq).to eq([post.id])
+      expect(post_versions.pluck(:event_id).uniq).to eq([event.fetch('id')])
+    end
+
     [:primary, :alias].each do |source_kind|
       it "keeps the primary identity when a #{ source_kind } collides within its Tag" do
         tag = create(:tag, primary_name: source_kind == :primary ? 'temporary' : 'foobar')
@@ -83,6 +108,7 @@ RSpec.describe TagNameSanitisationRule, type: :model do
       PostTag.create!(post:, tag: source)
       models = [Tag, TagName, TagVersion, TagDescription, TagDescriptionVersion, PostTag]
       snapshots = models.map { |model| model.order(*Array(model.primary_key)).map(&:attributes) }
+      events = event_rows
 
       expect { described_class.apply! }.to raise_error(ActiveRecord::RecordInvalid)
 
@@ -90,6 +116,7 @@ RSpec.describe TagNameSanitisationRule, type: :model do
         model.order(*Array(model.primary_key)).map(&:attributes)
       end
       expect(after_state).to eq(snapshots)
+      expect(event_rows).to eq(events)
       expect(post.reload.tags).to contain_exactly(source)
       expect(target.reload.name('ja')).to eq('foobar')
     end

backend/spec/models/tag_spec.rb

@@ -665,6 +665,7 @@ RSpec.describe Tag, type: :model do
 
     def create_post_version_for!(post, version_no: 1, event_type: 'create', created_by_user: nil)
       PostVersion.create!(
+          event_id: create_event!(event_type: 'unknown').id,
           post: post,
           version_no: version_no,
           event_type: event_type,
@@ -677,8 +678,7 @@ RSpec.describe Tag, type: :model do
           original_created_from: post.original_created_from,
           original_created_before: post.original_created_before,
           created_at: Time.current,
-        created_by_user: created_by_user
+          created_by_user: created_by_user)
-      )
     end
 
     context 'when post versions are enabled' do

backend/spec/models/version_record_spec.rb

@@ -6,6 +6,7 @@ RSpec.describe VersionRecord, type: :model do
 
   it 'makes TagVersion read only after create' do
     version = TagVersion.create!(
+        event_id: create_event!(event_type: 'unknown').id,
         tag: tag,
         version_no: 1,
         event_type: 'create',
@@ -25,6 +26,7 @@ RSpec.describe VersionRecord, type: :model do
 
   it 'prevents TagVersion destroy' do
     version = TagVersion.create!(
+        event_id: create_event!(event_type: 'unknown').id,
         tag: tag,
         version_no: 1,
         event_type: 'create',

backend/spec/rails_helper.rb

@@ -44,6 +44,7 @@ RSpec.configure do |config|
   end
 
   config.include TestRecords
+  config.include EventRecords
   config.include RakeTaskHelper
 
   # FactoryBot の create / create_list を使へるやぅにする

backend/spec/requests/counts_download_spec.rb

@@ -84,7 +84,9 @@ RSpec.describe 'Counts native GET acknowledgement', type: :request do
     expect(response).to have_http_status(:not_found)
     job, file, attempt = ready_job('json')
     record = create(:post)
-    PostVersion.create!(post: record, version_no: 1, event_type: 'discard', title: 'private',
+    PostVersion.create!(
+        event_id: create_event!(event_type: 'unknown').id,
+        post: record, version_no: 1, event_type: 'discard', title: 'private',
         url: record.url, tags: '', tags_json: [], parent_post_ids: '', created_at: Time.utc(2024))
     get "/counts/export/files/#{ file }", params: { job:, attempt: }
     expect(response).to have_http_status(:not_found)

backend/spec/requests/counts_history_boundaries_spec.rb

@@ -8,7 +8,9 @@ RSpec.describe 'History boundaries shared with Counts', type: :request do
 
   before do
     ['create', 'discard'].each_with_index do |event, index|
-      TagDescriptionVersion.create!(tag_id: tag.id, language_code: 'ja',
+      TagDescriptionVersion.create!(
+          event_id: create_event!(event_type: 'unknown').id,
+          tag_id: tag.id, language_code: 'ja',
           version_no: index + 1, event_type: event, body: 'private body',
           created_at: Time.utc(2024))
     end

backend/spec/requests/counts_masked_search_spec.rb

@@ -1,196 +0,0 @@
-require 'rails_helper'
-
-RSpec.describe 'Counts masked search', type: :request do
-  let!(:tag) { create(:tag, primary_name: '秘密のタグ') }
-  let(:actor) { create(:user, :member) }
-  let(:admin) { create(:user, :admin) }
-  let(:base) do
-    { 'resource' => 'tags', 'definition' => 'history', 'mode' => 'summary',
-      'locale' => 'ja', 'execution_at' => '2025-01-01T00:00:00Z',
-      'timezone' => 'UTC', 'rows' => '', 'cols' => '', 'sort' => '' }
-  end
-
-  before do
-    [1, 2].each do |number|
-      TagVersion.create!(tag:, version_no: number,
-          event_type: number == 1 ? 'create' : 'discard', name: '秘密のタグ',
-          category: 'general', aliases: '秘密の別名', parent_tag_ids: '',
-          names: { ja: { name: '秘密のタグ', script_code: 'Jpan', auto_generated: false,
-                        aliases: [{ name: '秘密の別名', script_code: 'Jpan' }] } },
-          created_by_user: actor, created_at: Time.utc(2023, number))
-    end
-  end
-
-  def query(extra = {})
-    get '/counts/query', params: base.merge(extra)
-    expect(response).to have_http_status(:ok), extra.inspect
-    response.parsed_body
-  end
-
-  def predicate(field, operator, value, index = 0)
-    prefix = "conditions.#{ index }"
-    result = { 'conditions' => '', "#{ prefix }.field" => field,
-               "#{ prefix }.operator" => operator }
-    if ['in', 'any', 'all', 'none', 'not_in'].include?(operator)
-      result.merge!("#{ prefix }.values" => '1', 'condition_values' => '',
-          "condition_values.#{ index }.condition" => index.to_s,
-          "condition_values.#{ index }.value_type" => 'string',
-          "condition_values.#{ index }.value" => value)
-    else
-      result["#{ prefix }.value"] = value
-    end
-    result
-  end
-
-  it 'rejects every name and alias predicate on private history' do
-    ['name', 'name_ja', 'names.name', 'aliases.name', 'names.aliases.name'].each do |field|
-      secret = field.include?('aliases') ? '秘密の別名' : '秘密のタグ'
-      multiple = !['name', 'name_ja'].include?(field)
-      operators = multiple ? ['any', 'all', 'none'] : ['in', 'not_in']
-      ['eq', 'ne', 'like', *operators].each do |operator|
-        [secret, '********', '%', ''].each do |value|
-          expected = (value == '' && ['eq', 'ne', 'like'].include?(operator)) ? 2 : 0
-          expect(query(predicate(field, operator, value))['count']).to eq(expected)
-        end
-      end
-      blank = predicate(field, 'eq', '').merge('conditions.0.blank' => '1')
-      expect(query(blank)['count']).to eq(0)
-    end
-  end
-
-  it 'ignores missing and empty scalar values unless blank is checked' do
-    ['name', 'name_ja', 'names.name', 'aliases.name'].each do |field|
-      ['eq', 'ne', 'like'].each do |operator|
-        condition = predicate(field, operator, '')
-        [condition, condition.except('conditions.0.value')].each do |empty|
-          expect(query(empty)['count']).to eq(2)
-          expect(query(empty.merge('conditions.0.blank' => '0'))['count']).to eq(2)
-          expect(query(empty.merge('conditions.0.blank' => '1'))['count']).to eq(0)
-        end
-      end
-    end
-  end
-
-  it 'keeps details totals unchanged for inactive private predicates' do
-    settings = predicate('name', 'ne', '').merge('mode' => 'details')
-    result = query(settings)
-    expect(result['count']).to eq(0)
-    expect(result['versions']).to be_empty
-    expect(result['output_count']).to eq(2)
-    active = query(settings.merge('conditions.0.blank' => '1'))
-    expect(active['output_count']).to eq(0)
-  end
-
-  it 'ignores missing sets but preserves explicit empty set semantics' do
-    { 'name' => ['in', 'not_in'], 'aliases.name' => ['any', 'all', 'none'] }.each do
-        |field, operators|
-      operators.each do |operator|
-        condition = { 'conditions' => '', 'conditions.0.field' => field,
-                      'conditions.0.operator' => operator }
-        expect(query(condition)['count']).to eq(2)
-        empty = condition.merge('conditions.0.values' => '1', 'condition_values' => '')
-        expected = ['in', 'any'].include?(operator) ? 0 : 2
-        expect(query(empty)['count']).to eq(expected)
-        expect(query(condition.merge('conditions.0.blank' => '1'))['count']).to eq(0)
-        # An explicit empty string element is a real value, not an unspecified set.
-        expect(query(predicate(field, operator, ''))['count']).to eq(0)
-      end
-    end
-  end
-
-  it 'ignores empty private predicates regardless of their position' do
-    first = predicate('name', 'ne', '')
-        .merge(predicate('resource_id', 'eq', tag.id.to_s, 1))
-    last = predicate('resource_id', 'eq', tag.id.to_s)
-        .merge(predicate('aliases.name', 'like', '', 1))
-    expect(query(first)['count']).to eq(2)
-    expect(query(last)['count']).to eq(2)
-    active = predicate('name', 'ne', 'unrelated')
-        .merge(predicate('aliases.name', 'like', '', 1))
-    expect(query(active)['count']).to eq(0)
-  end
-
-  it 'searches public literal markers and treats axis predicates as explicit' do
-    public_tag = create(:tag, primary_name: '********')
-    TagVersion.create!(tag: public_tag, version_no: 1, event_type: 'create',
-        name: '********', category: 'general', aliases: '', parent_tag_ids: '',
-        names: { ja: { name: '********', script_code: 'Jpan', auto_generated: false,
-                      aliases: [] } }, created_at: Time.utc(2023))
-    expect(query['count']).to eq(3)
-    ['eq', 'ne', 'like', 'in', 'not_in'].each do |operator|
-      expected = ['ne', 'not_in'].include?(operator) ? 0 : 1
-      expect(query(predicate('name', operator, '********'))['count']).to eq(expected)
-    end
-    blank = predicate('aliases.name', 'eq', '').merge('conditions.0.blank' => '1')
-    expect(query(blank)['count']).to eq(1)
-    ['********', '', nil].each do |value|
-      condition = { 'conditions' => '', 'conditions.0.field' => 'name',
-                    'conditions.0.operator' => 'axis_eq',
-                    'conditions.0.value_type' => value.nil? ? 'null' : 'string' }
-      condition['conditions.0.value'] = value unless value.nil?
-      expected = value == '********' ? 1 : 0
-      expect(query(condition)['count']).to eq(expected)
-      drill = { 'drill' => '', 'drill.0.field' => 'name',
-                'drill.0.value_type' => value.nil? ? 'null' : 'string' }
-      drill['drill.0.value'] = value unless value.nil?
-      expect(query(drill)['count']).to eq(expected)
-    end
-  end
-
-  it 'keeps public identity and timeline predicates searchable' do
-    expect(query['count']).to eq(2)
-    values = { 'resource_id' => tag.id.to_s, 'version_no' => '2',
-               'event_type' => 'discard', 'user' => actor.id.to_s,
-               'created_at' => '2023-02-01T00:00:00Z' }
-    values.each do |field, value|
-      expected = ['resource_id', 'user'].include?(field) ? 2 : 1
-      expect(query(predicate(field, 'eq', value))['count']).to eq(expected)
-    end
-    condition = predicate('name', 'ne', '秘密のタグ')
-        .merge(predicate('event_type', 'eq', 'discard', 1))
-    expect(query(condition)['count']).to eq(0)
-    expect(query(predicate('category', 'eq', '********'))['count']).to eq(0)
-    expect(query(predicate('category', 'eq', 'general'))['count']).to eq(0)
-  end
-
-  it 'keeps public predicates available after combining multiple conditions' do
-    condition = predicate('resource_id', 'eq', tag.id.to_s)
-        .merge(predicate('event_type', 'eq', 'discard', 1))
-    expect(query(condition)['count']).to eq(1)
-    condition.merge!(predicate('name', 'ne', 'unrelated', 2))
-    expect(query(condition)['count']).to eq(0)
-  end
-
-  it 'keeps real name searches for administrators and excludes private details' do
-    condition = predicate('name', 'eq', '秘密のタグ')
-    details = query(condition.merge('mode' => 'details'))
-    expect(details['versions']).to be_empty
-    expect(details['output_count']).to eq(0)
-    masked = query(predicate('name', 'eq', '********').merge('mode' => 'details'))
-    expect(masked['versions']).to be_empty
-    expect(masked['output_count']).to eq(0)
-    sign_in_as(admin)
-    expect(query(condition)['count']).to eq(2)
-    expect(query(condition.merge('mode' => 'details'))['versions'].length).to eq(2)
-  end
-
-  it 'rejects private names reached through a post tag snapshot' do
-    post = create(:post)
-    PostVersion.create!(post:, version_no: 1, event_type: 'create', title: 'post',
-        url: post.url, tags: '', parent_post_ids: '',
-        tags_json: [{ tag_id: tag.id, version_no: 1, name: '秘密のタグ',
-                     category: 'general', sections: [] }],
-        created_at: Time.utc(2024))
-    ['tags.name', 'tags.names.name', 'tags.name_ja'].each do |field|
-      ['eq', 'ne', 'like', 'any', 'all', 'none'].each do |operator|
-        ['秘密のタグ', '********', '%'].each do |value|
-          settings = predicate(field, operator, value).merge('resource' => 'posts')
-          expect(query(settings)['count']).to eq(0)
-        end
-      end
-      blank = predicate(field, 'eq', '').merge('resource' => 'posts',
-          'conditions.0.blank' => '1')
-      expect(query(blank)['count']).to eq(0)
-    end
-  end
-end

backend/spec/requests/counts_spec.rb

@@ -10,12 +10,16 @@ RSpec.describe 'Legacy Counts API', type: :request do
                  category: 'general', sections: [] }
     [1, 2, 3].each do |number|
       time = Time.utc(2024, number == 3 ? 2 : 1, number, 0, 0)
-      PostVersion.create!(post:, version_no: number,
+      PostVersion.create!(
+          event_id: create_event!(event_type: 'unknown').id,
+          post:, version_no: number,
           event_type: number == 1 ? 'create' : 'update',
           tags: '', url: post.url, title: "Snapshot #{ number }", parent_post_ids: '',
           tags_json: number == 1 ? [snapshot] : [],
           created_by_user: number == 3 ? nil : actor, created_at: time)
-      TagVersion.create!(tag:, version_no: number,
+      TagVersion.create!(
+          event_id: create_event!(event_type: 'unknown').id,
+          tag:, version_no: number,
           event_type: number == 1 ? 'create' : 'update',
           name: 'counts tag', category: 'general', aliases: '', parent_tag_ids: '',
           names: { ja: { name: 'counts tag', script_code: 'Jpan',

backend/spec/requests/counts_table_spec.rb

@@ -14,7 +14,9 @@ RSpec.describe 'Counts table API', type: :request do
   end
 
   before do
-    TagVersion.create!(tag:, version_no: 1, event_type: 'create', name: 'alpha',
+    TagVersion.create!(
+        event_id: create_event!(event_type: 'unknown').id,
+        tag:, version_no: 1, event_type: 'create', name: 'alpha',
         category: 'general', aliases: '', parent_tag_ids: '',
         names: { ja: { name: 'alpha', script_code: 'Jpan', auto_generated: false,  aliases: [] } },
         created_at: Time.utc(2023))
@@ -24,7 +26,9 @@ RSpec.describe 'Counts table API', type: :request do
         { tag_id: tag.id, version_no: 1, name: 'alpha', category: 'general', sections: [] },
         { external_tag_id: external.id }]
     [1, 2, 3].each do |number|
-      PostVersion.create!(post: record, version_no: number,
+      PostVersion.create!(
+          event_id: create_event!(event_type: 'unknown').id,
+          post: record, version_no: number,
           event_type: number == 1 ? 'create' : 'update', url: record.url,
           title: "snapshot #{ number }", tags: '', parent_post_ids: '',
           tags_json: snapshots.first(number == 1 ? 2 : (number == 2 ? 1 : 0)),
@@ -134,7 +138,9 @@ RSpec.describe 'Counts table API', type: :request do
   end
 
   it 'checks the current latest flag beyond the execution timestamp' do
-    PostVersion.create!(post: record, version_no: 4, event_type: 'update',
+    PostVersion.create!(
+        event_id: create_event!(event_type: 'unknown').id,
+        post: record, version_no: 4, event_type: 'update',
         url: record.url, title: 'after execution', tags: '', tags_json: [],
         parent_post_ids: '', created_at: Time.utc(2025, 2, 1))
     result = query
@@ -188,12 +194,16 @@ RSpec.describe 'Counts table API', type: :request do
       tag.tag_names.find_by!(language_code: 'ja', primary_flg: true)
           .update!(name: 'renamed-alpha')
       create(:tag_name, :alias, tag:, name: 'alpha-alias')
-      TagVersion.create!(tag:, version_no: 2, event_type: 'update', name: 'renamed-alpha',
+      TagVersion.create!(
+          event_id: create_event!(event_type: 'unknown').id,
+          tag:, version_no: 2, event_type: 'update', name: 'renamed-alpha',
           category: 'general', aliases: 'alpha-alias', parent_tag_ids: '',
           names: { ja: { name: 'renamed-alpha', script_code: 'Jpan', auto_generated: false,
                          aliases: [{ name: 'alpha-alias', script_code: 'Jpan' }] } },
           created_at: Time.utc(2024, 2, 1))
-      PostVersion.create!(post: record, version_no: 4, event_type: 'update',
+      PostVersion.create!(
+          event_id: create_event!(event_type: 'unknown').id,
+          post: record, version_no: 4, event_type: 'update',
           url: record.url, title: 'after rename', tags: '', parent_post_ids: '',
           tags_json: [{ tag_id: tag.id, version_no: 2, name: 'renamed-alpha',
                         category: 'general', sections: [] }],
@@ -257,7 +267,9 @@ RSpec.describe 'Counts table API', type: :request do
 
   it 'reports column overflow separately from malformed input' do
     101.times do |index|
-      PostVersion.create!(post: record, version_no: index + 4,
+      PostVersion.create!(
+          event_id: create_event!(event_type: 'unknown').id,
+          post: record, version_no: index + 4,
           event_type: 'update', url: record.url, title: "column #{ index }",
           tags: '', tags_json: [], parent_post_ids: '', created_at: Time.utc(2024, 3))
     end
@@ -301,7 +313,9 @@ RSpec.describe 'Counts table API', type: :request do
         sign_in_as(create(:user, role)) if role
         # Equal timestamps deliberately require version ordering, not a date comparison.
         ['discard', 'restore', 'discard', 'restore'].each_with_index do |event, index|
-          PostVersion.create!(post: record, version_no: index + 4, event_type: event,
+          PostVersion.create!(
+              event_id: create_event!(event_type: 'unknown').id,
+              post: record, version_no: index + 4, event_type: event,
               url: record.url, title: event == 'restore' ? 'restored' : 'private snapshot',
               tags: '', tags_json: [], parent_post_ids: '', created_at: Time.utc(2024, 3))
         end
@@ -329,7 +343,9 @@ RSpec.describe 'Counts table API', type: :request do
       end
 
       it 'does not resolve private condition names even when the result set is empty' do
-        TagVersion.create!(tag:, version_no: 2, event_type: 'discard', name: 'secret tag',
+        TagVersion.create!(
+            event_id: create_event!(event_type: 'unknown').id,
+            tag:, version_no: 2, event_type: 'discard', name: 'secret tag',
             category: 'general', aliases: '', parent_tag_ids: '',
             names: { ja: { name: 'secret tag', script_code: 'Jpan', auto_generated: false, aliases: [] } },
             created_at: Time.utc(2024, 2))
@@ -345,7 +361,9 @@ RSpec.describe 'Counts table API', type: :request do
     end
   end
   it 'includes private history in the public timeline without an exclusion count' do
-    PostVersion.create!(post: record, version_no: 4, event_type: 'discard', url: record.url,
+    PostVersion.create!(
+        event_id: create_event!(event_type: 'unknown').id,
+        post: record, version_no: 4, event_type: 'discard', url: record.url,
         title: 'hidden title', tags: '', tags_json: [], parent_post_ids: '',
         created_at: Time.utc(2024, 3))
     result = query(mode: 'summary', rows: 'created_at:month', cols: 'event_type')
@@ -354,25 +372,15 @@ RSpec.describe 'Counts table API', type: :request do
     expect(result['cells'].sum { _1['count'] }).to eq(4)
     expect(response.body).not_to include('hidden title')
     masked = query(mode: 'summary', rows: 'resource_id', cols: '')
-    expect(masked['cells'].map { _1['values'] }).to eq([[record.id]])
+    expect(masked['cells'].map { _1['values'] }).to eq([[CountsAxes::MASKED_VALUE]])
     expect(masked['cells'].first['count']).to eq(4)
     expect(query['versions']).to be_empty
   end
 
-  it 'allows public identity predicates without exposing private snapshot fields' do
+  it 'rejects private summary predicates instead of exposing a count oracle' do
-    PostVersion.create!(post: record, version_no: 4, event_type: 'discard',
+    get '/counts/query', params: base.merge(mode: 'summary', resource_id: record.id.to_s)
-        url: record.url, title: 'hidden title', tags: '', tags_json: [],
+    expect(response).to have_http_status(:forbidden)
-        parent_post_ids: '', created_at: Time.utc(2024, 3))
+    expect(json).to eq('error' => 'private_condition')
-
-    get '/counts/query', params: base.merge(mode: 'summary',
-        resource_id: record.id.to_s, rows: 'resource_id', cols: 'title')
-
-    expect(response).to have_http_status(:ok)
-    expect(json['count']).to eq(4)
-    expect(json['cells'].sum { _1['count'] }).to eq(4)
-    expect(json['cells'].map { _1['values'].last })
-        .to include(CountsAxes::MASKED_VALUE)
-    expect(response.body).not_to include('hidden title')
   end
 
   it 'reports the combined axis limit without replacing it with a generic 400' do

backend/spec/requests/materials_spec.rb

@@ -314,6 +314,7 @@ RSpec.describe 'Materials API', type: :request do
           .and change(Tag, :count).by(1)
           .and change(TagName, :count).by(1)
           .and change(MaterialVersion, :count).by(1)
+          .and change { event_rows.length }.by(1)
 
         expect(response).to have_http_status(:created)
 
@@ -325,6 +326,12 @@ RSpec.describe 'Materials API', type: :request do
         expect(material.file.attached?).to be(true)
         expect(material.version_no).to eq(1)
         expect(material.material_versions.first.event_type).to eq('create')
+        event = event_rows.last
+        expect(event).to include(
+            'event_type' => 'materials.create',
+            'created_by_user_id' => member_user.id)
+        expect(material.material_versions.first.event_id).to eq(event.fetch('id'))
+        expect(material.tag.tag_versions.pluck(:event_id)).to eq([event.fetch('id')])
         expect(material.material_export_items.first.export_path).to eq('伊地知ニジカ/created.png')
         expect(material.material_versions.first.export_paths_json).to eq(
           'legacy_drive' => '伊地知ニジカ/created.png'
@@ -509,6 +516,7 @@ RSpec.describe 'Materials API', type: :request do
             export_paths: { legacy_drive: '伊地知ニジカ/updated.jpg' }
           }
         end.to change(MaterialVersion, :count).by(2)
+            .and change { event_rows.length }.by(1)
 
         expect(response).to have_http_status(:ok)
 
@@ -517,6 +525,12 @@ RSpec.describe 'Materials API', type: :request do
         expect(material.tag.category).to eq('material')
         expect(material.url).to eq('https://example.com/updated-source')
         expect(material.updated_by_user).to eq(member_user)
+        event = event_rows.last
+        expect(event).to include(
+            'event_type' => 'materials.update',
+            'created_by_user_id' => member_user.id)
+        expect(material.material_versions.pluck(:event_id).uniq).to eq([event.fetch('id')])
+        expect(material.tag.tag_versions.pluck(:event_id)).to eq([event.fetch('id')])
         expect(material.file.attached?).to be(true)
         expect(material.file.blob.id).not_to eq(old_blob_id)
         expect(ActiveStorage::Blob.where(id: old_blob_id).exists?).to be(true)
@@ -632,6 +646,7 @@ RSpec.describe 'Materials API', type: :request do
         MaterialVersionRecorder.record!(material:, event_type: :create,
                                         created_by_user: member_user)
         TagVersioning.ensure_snapshot!(tag, created_by_user: member_user)
+        events = event_rows
 
         expect do
           put "/materials/#{ material.id }", params: {
@@ -643,6 +658,7 @@ RSpec.describe 'Materials API', type: :request do
 
         expect(response).to have_http_status(:ok)
         expect(material.reload.version_no).to eq(1)
+        expect(event_rows).to eq(events)
       end
 
       it 'records update version when only export_path changes' do
@@ -807,6 +823,12 @@ RSpec.describe 'Materials API', type: :request do
 
     it 'creates source suppression as member' do
       sign_in_as(member_user)
+      materials = ['a', 'b'].map do |name|
+        Material.create!(
+            source_kind: 'google_drive_file', source_file_id: "blocked-#{ name }",
+            source_path: "伊地知ニジカ/危険素材/#{ name }.png",
+            url: "https://example.com/blocked-#{ name }", created_by_user: member_user)
+      end
 
       expect do
         post '/materials/suppressions', params: {
@@ -815,6 +837,7 @@ RSpec.describe 'Materials API', type: :request do
           reason: 'copyright_high_risk'
         }
       end.to change(MaterialSyncSuppression, :count).by(1)
+          .and change { event_rows.length }.by(1)
 
       expect(response).to have_http_status(:created)
       expect(json).to include(
@@ -822,6 +845,14 @@ RSpec.describe 'Materials API', type: :request do
         'drive_path' => '伊地知ニジカ/危険素材',
         'normalized_source_key' => 'google_drive_path_prefix:伊地知ニジカ/危険素材'
       )
+      event = event_rows.last
+      expect(event).to include(
+          'event_type' => 'materials.block', 'created_by_user_id' => member_user.id)
+      expect(materials.map { _1.reload.discarded? }).to eq([true, true])
+      versions = MaterialVersion.where(material_id: materials.map(&:id))
+      expect(versions.where(event_type: 'discard').pluck(:material_id))
+          .to match_array(materials.map(&:id))
+      expect(versions.pluck(:event_id).uniq).to eq([event.fetch('id')])
     end
   end
 
@@ -860,11 +891,19 @@ RSpec.describe 'Materials API', type: :request do
       end
 
       it 'discards the material and returns 204' do
-        delete "/materials/#{ material.id }"
+        expect { delete "/materials/#{ material.id }" }
+            .to change { event_rows.length }.by(1)
 
         expect(response).to have_http_status(:no_content)
         expect(Material.find_by(id: material.id)).to be_nil
         expect(Material.with_discarded.find(material.id)).to be_discarded
+        event = event_rows.last
+        expect(event).to include(
+            'event_type' => 'materials.destroy',
+            'created_by_user_id' => member_user.id)
+        versions = MaterialVersion.where(material_id: material.id)
+        expect(versions.order(:version_no).last.event_type).to eq('discard')
+        expect(versions.pluck(:event_id).uniq).to eq([event.fetch('id')])
       end
     end
   end

backend/spec/requests/nico_tags_spec.rb

@@ -177,6 +177,7 @@ RSpec.describe 'NicoTags', type: :request do
         }
       }.to change(TagVersion, :count).by(2)
        .and change(NicoTagVersion, :count).by(1)
+       .and change { event_rows.length }.by(1)
 
       expect(response).to have_http_status(:ok)
 
@@ -186,6 +187,10 @@ RSpec.describe 'NicoTags', type: :request do
       linked_versions = TagVersion.where(tag: [linked_a, linked_b]).order(:tag_id)
       expect(linked_versions.map(&:event_type)).to eq(['create', 'create'])
       expect(linked_versions.map(&:created_by_user_id)).to all(eq(admin.id))
+      event = event_rows.last
+      expect(event).to include(
+          'event_type' => 'tags.update', 'created_by_user_id' => admin.id)
+      expect(linked_versions.pluck(:event_id).uniq).to eq([event.fetch('id')])
 
       versions = nico_tag.reload.nico_tag_versions.order(:version_no)
       expect(versions.map(&:event_type)).to eq(['create', 'update'])

backend/spec/requests/post_history_privacy_spec.rb

@@ -1,129 +0,0 @@
-require 'rails_helper'
-
-RSpec.describe 'Post history privacy', type: :request do
-  let(:origin) { Time.utc(2020, 1, 1) }
-  let!(:post_record) do
-    create(:post, title: 'current', created_at: origin, updated_at: origin)
-  end
-  let!(:other_post) do
-    create(:post, created_at: origin, updated_at: origin + 3.days + 1.hour)
-  end
-  let!(:tag) { create(:tag, primary_name: 'private-history-tag') }
-  let!(:external) { create(:external_tag, name: 'external-history-tag') }
-
-  before do
-    ['create', 'discard'].each_with_index do |event, index|
-      TagVersion.create!(tag:, version_no: index + 1, event_type: event,
-          name: 'private-history-tag', category: 'general', aliases: '', parent_tag_ids: '',
-          names: { ja: { name: 'private-history-tag', script_code: 'Jpan',
-                         auto_generated: false, aliases: [] } },
-          created_at: origin + index.hours)
-    end
-    NicoTagVersion.create!(external_tag: external, version_no: 1, event_type: 'create',
-        name: 'nico:external-history-tag', linked_tags: 'private-history-tag',
-        created_at: origin)
-    ['create', 'discard', 'restore', 'update'].each_with_index do |event, index|
-      snapshots =
-          if index < 2
-            [{ tag_id: tag.id, version_no: 1, name: 'private-history-tag', sections: [] }]
-          elsif index == 3
-            [{ external_tag_id: external.id }]
-          else
-            []
-          end
-      PostVersion.create!(post: post_record, version_no: index + 1, event_type: event,
-          title: "version #{ index + 1 }", url: post_record.url, tags: '',
-          tags_json: snapshots, parent_post_ids: '', created_at: origin + (index + 1).days)
-    end
-  end
-
-  it 'evaluates each reference condition against the restored snapshot alone' do
-    HistoryAccess.set(user: nil) do
-      restored = PostVersion.where(post_id: post_record.id, version_no: 3)
-      HistoryAccess.reference_sql('post_versions', 'post_versions').each do |condition|
-        expect(restored.where(Arel.sql(condition)).pluck(:version_no)).to eq([3])
-      end
-      expect(HistoryAccess.visible(PostVersion.where(post_id: post_record.id))
-          .pluck(:version_no)).to eq([3])
-    end
-  end
-
-  it 'keeps every version through a later discard private after another restore' do
-    ['discard', 'restore'].each_with_index do |event, index|
-      PostVersion.create!(post: post_record, version_no: index + 5, event_type: event,
-          title: 'later snapshot', url: post_record.url, tags: '', tags_json: [],
-          parent_post_ids: '', created_at: origin + (index + 5).days)
-    end
-
-    get '/posts/versions', params: { post: post_record.id }
-
-    expect(response).to have_http_status(:ok)
-    expect(response.parsed_body.fetch('versions').pluck('version_no')).to eq([6])
-    expect(response.parsed_body.fetch('count')).to eq(1)
-    expect(response.parsed_body.fetch('versions').first.fetch('title').fetch('prev')).to be_nil
-  end
-
-  ['anonymous', 'member', 'admin'].each do |role|
-    context "as #{ role }" do
-      before do
-        sign_in_as(create(:user, role.to_sym)) unless role == 'anonymous'
-      end
-
-      it 'uses only authorised history timestamps for display' do
-        get '/posts'
-        expect(response).to have_http_status(:ok)
-        row = response.parsed_body.fetch('posts').find { _1.fetch('id') == post_record.id }
-        expected = origin + (role == 'admin' ? 4 : 3).days
-        expect(Time.zone.parse(row.fetch('updated_at'))).to eq(expected)
-      end
-
-      it 'uses the same visibility for date bounds and count' do
-        get '/posts', params: { updated_from: (origin + 4.days).iso8601,
-                                updated_to: (origin + 4.days).iso8601 }
-        expect(response).to have_http_status(:ok)
-        ids = response.parsed_body.fetch('posts').pluck('id')
-        expect(ids).to eq(role == 'admin' ? [post_record.id] : [])
-        expect(response.parsed_body.fetch('count')).to eq(ids.length)
-      end
-
-      it 'sorts using authorised timestamps in both directions' do
-        ['asc', 'desc'].each do |direction|
-          get '/posts', params: { order: "updated_at:#{ direction }" }
-          expect(response).to have_http_status(:ok)
-          expected = role == 'admin' ? [other_post.id, post_record.id] :
-              [post_record.id, other_post.id]
-          expected.reverse! if direction == 'desc'
-          expect(response.parsed_body.fetch('posts').pluck('id')).to eq(expected)
-        end
-      end
-
-      it 'applies authorised timestamp ordering before pagination' do
-        get '/posts', params: { order: 'updated_at:desc', limit: 1 }
-
-        expect(response).to have_http_status(:ok)
-        expected = role == 'admin' ? post_record.id : other_post.id
-        expect(response.parsed_body.fetch('posts').pluck('id')).to eq([expected])
-        expect(response.parsed_body.fetch('count')).to eq(2)
-      end
-
-      it 'counts only visible versions and masks a private previous version' do
-        get '/posts/versions', params: { post: post_record.id }
-        expect(response).to have_http_status(:ok)
-        body = response.parsed_body
-        expected = role == 'admin' ? [4, 3, 2, 1] : [3]
-        expect(body.fetch('count')).to eq(expected.length)
-        expect(body.fetch('versions').pluck('version_no')).to eq(expected)
-        restored = body.fetch('versions').find { _1.fetch('version_no') == 3 }
-        expect(restored.fetch('title').fetch('prev')).to eq(role == 'admin' ? 'version 2' : nil)
-      end
-
-      it 'uses only an authorised previous version for tag filtering' do
-        get '/posts/versions', params: { post: post_record.id, tag: tag.id }
-        expect(response).to have_http_status(:ok)
-        expected = role == 'admin' ? [3, 2, 1] : []
-        expect(response.parsed_body.fetch('versions').pluck('version_no')).to eq(expected)
-        expect(response.parsed_body.fetch('count')).to eq(expected.length)
-      end
-    end
-  end
-end

backend/spec/requests/posts_spec.rb

@@ -50,6 +50,8 @@ RSpec.describe 'Posts API', type: :request do
             post:,
             version_no: 1,
             event_type: 'create',
+            event_id: create_event!(
+                event_type: 'posts.create', created_by_user: post.uploaded_user).id,
             title: post.title,
             url: post.url,
             thumbnail_base: post.thumbnail_base,
@@ -629,37 +631,6 @@ RSpec.describe 'Posts API', type: :request do
         create(:post_tag, post: plain_post, tag:, created_at: t3)
       end
 
-      it 'displays history time after pagination without joining history to posts or count' do
-        queries = []
-        subscriber = ->(event) { queries << event.payload.fetch(:sql) }
-        ActiveSupport::Notifications.subscribed(subscriber, 'sql.active_record') do
-          get '/posts', params: { url: '/version-time/', order: 'url:asc', limit: 1 }
-        end
-
-        expect(response).to have_http_status(:ok)
-        expect(json.fetch('posts').pluck('id')).to eq([history_post.id])
-        expect(Time.zone.parse(json.fetch('posts').first.fetch('updated_at'))).to eq(t2)
-        expect(json.fetch('count')).to eq(3)
-        post_queries = queries.select { _1.include?('FROM `posts`') }
-        expect(post_queries).not_to be_empty
-        expect(post_queries.grep(/post_versions/)).to be_empty
-      end
-
-      it 'omits the history aggregate from count when only sorting by update time' do
-        queries = []
-        subscriber = ->(event) { queries << event.payload.fetch(:sql) }
-        ActiveSupport::Notifications.subscribed(subscriber, 'sql.active_record') do
-          get '/posts', params: { url: '/version-time/', order: 'updated_at:desc', limit: 1 }
-        end
-
-        expect(response).to have_http_status(:ok)
-        expect(json.fetch('posts').pluck('id')).to eq([newer_post.id])
-        expect(json.fetch('count')).to eq(3)
-        count_queries = queries.select { _1.include?('FROM `posts`') && _1.match?(/COUNT\(/i) }
-        expect(count_queries).not_to be_empty
-        expect(count_queries.grep(/post_versions/)).to be_empty
-      end
-
       ['asc', 'desc'].each do |direction|
         it "sorts by the later of post update and latest version time (#{ direction })" do
           get '/posts', params: { url: '/version-time/', order: "updated_at:#{ direction }" }
@@ -689,16 +660,6 @@ RSpec.describe 'Posts API', type: :request do
         expect(json.fetch('posts').map { |item| item.fetch('id') }).to eq([history_post.id])
         expect(json.fetch('count')).to eq(1)
       end
-
-      it 'counts every timestamp match before pagination' do
-        get '/posts', params: { url: '/version-time/', order: 'updated_at:asc',
-                               updated_from: t1.iso8601, updated_to: t3.iso8601,
-                               limit: 1, page: 2 }
-
-        expect(response).to have_http_status(:ok)
-        expect(json.fetch('posts').pluck('id')).to eq([history_post.id])
-        expect(json.fetch('count')).to eq(3)
-      end
     end
 
     context 'when original_created_from/original_created_to are provided' do
@@ -1068,7 +1029,7 @@ RSpec.describe 'Posts API', type: :request do
 
     it 'dry-runs without persisting posts or new tags' do
       sign_in_as(member)
-      counts = [Post.count, Tag.count, TagName.count]
+      counts = [Post.count, Tag.count, TagName.count, event_rows.length]
 
       post '/posts?dry=1', params: post_write_params(
           title: 'dry-run post',
@@ -1084,7 +1045,7 @@ RSpec.describe 'Posts API', type: :request do
           [{ 'name' => 'new_dry_run_tag',
              'category' => 'character',
              'section_literals' => [] }])
-      expect([Post.count, Tag.count, TagName.count]).to eq(counts)
+      expect([Post.count, Tag.count, TagName.count, event_rows.length]).to eq(counts)
     end
 
     it 'dry-runs an existing URL without validating its upload' do
@@ -2259,6 +2220,7 @@ RSpec.describe 'Posts API', type: :request do
 
     def create_post_version! post, version_no:, event_type:, created_by_user:, created_at:
       PostVersion.create!(
+          event_id: create_event!(event_type: 'unknown').id,
           post:,
           version_no:,
           event_type:,
@@ -2271,8 +2233,7 @@ RSpec.describe 'Posts API', type: :request do
           original_created_from: post.original_created_from,
           original_created_before: post.original_created_before,
           created_at:,
-        created_by_user:
+          created_by_user:)
-      )
     end
 
     let!(:v1) do
@@ -2600,6 +2561,7 @@ RSpec.describe 'Posts API', type: :request do
             tags: 'spec_tag',
             thumbnail: dummy_upload)
       end.to change(PostVersion, :count).by(1)
+          .and change { event_rows.length }.by(1)
 
       expect(response).to have_http_status(:created)
 
@@ -2611,6 +2573,13 @@ RSpec.describe 'Posts API', type: :request do
       expect(version.url).to eq('https://example.com/versioned-post')
       expect(version.created_by_user_id).to eq(member.id)
       expect(version.tags).to eq(snapshot_tags(created_post))
+      event = event_rows.last
+      expect(event).to include(
+          'event_type' => 'posts.create', 'created_by_user_id' => member.id)
+      expect(version.event_id).to eq(event.fetch('id'))
+      tag_versions = TagVersion.where(tag_id: created_post.tags.select(:id))
+      expect(tag_versions).not_to be_empty
+      expect(tag_versions.pluck(:event_id).uniq).to eq([event.fetch('id')])
     end
 
     it 'creates next version on PUT /posts/:id when snapshot changes' do
@@ -2626,6 +2595,7 @@ RSpec.describe 'Posts API', type: :request do
             title: 'updated title',
             tags: 'spec_tag_2')
       end.to change(PostVersion, :count).by(1)
+          .and change { event_rows.length }.by(1)
 
       expect(response).to have_http_status(:ok)
 
@@ -2635,6 +2605,12 @@ RSpec.describe 'Posts API', type: :request do
       expect(version.title).to eq('updated title')
       expect(version.created_by_user_id).to eq(member.id)
       expect(version.tags).to eq(snapshot_tags(post_record.reload))
+      event = event_rows.last
+      expect(event).to include(
+          'event_type' => 'posts.update', 'created_by_user_id' => member.id)
+      expect(version.event_id).to eq(event.fetch('id'))
+      tag_version = TagVersion.find_by!(tag_id: tag_name2.reload.tag_id, version_no: 1)
+      expect(tag_version.event_id).to eq(event.fetch('id'))
     end
 
     it 'does not create a new version on PUT /posts/:id when snapshot is unchanged' do
@@ -2643,6 +2619,7 @@ RSpec.describe 'Posts API', type: :request do
       PostTag.create!(post: post_record, tag: Tag.no_deerjikist)
       base_version = create_post_version_for!(post_record.reload)
 
+      events = event_rows
       expect {
         put "/posts/#{post_record.id}", params: post_write_params(
             base_version_no: base_version.version_no,
@@ -2656,10 +2633,12 @@ RSpec.describe 'Posts API', type: :request do
       expect(version.version_no).to eq(1)
       expect(version.event_type).to eq('create')
       expect(version.tags).to eq(snapshot_tags(post_record))
+      expect(event_rows).to eq(events)
     end
 
     it 'does not create a version when POST /posts is invalid' do
       sign_in_as(member)
+      events = event_rows
 
       expect do
         post '/posts', params: post_write_params(
@@ -2670,11 +2649,13 @@ RSpec.describe 'Posts API', type: :request do
       end.not_to change(PostVersion, :count)
 
       expect(response).to have_http_status(:unprocessable_entity)
+      expect(event_rows).to eq(events)
     end
 
     it 'does not create a version when PUT /posts/:id is invalid' do
       sign_in_as(member)
       base_version = create_post_version_for!(post_record)
+      events = event_rows
 
       expect do
         put "/posts/#{post_record.id}", params: post_write_params(
@@ -2686,6 +2667,7 @@ RSpec.describe 'Posts API', type: :request do
       end.not_to change(PostVersion, :count)
 
       expect(response).to have_http_status(:unprocessable_entity)
+      expect(event_rows).to eq(events)
     end
 
     it 'rejects second-bearing original created timestamps on POST /posts' do

backend/spec/requests/sitemap_entries_spec.rb

@@ -119,7 +119,9 @@ RSpec.describe 'Sitemap entries API', type: :request do
       # Legacy empty bodies can exist even though the write service rejects them.
       empty = TagDescription.create!(tag: empty_tag, language_code: 'ain',
                                      body: '', version_no: 1)
-      TagDescriptionVersion.create!(tag_id: empty_tag.id, language_code: 'ain',
+      TagDescriptionVersion.create!(
+          event_id: create_event!(event_type: 'unknown').id,
+          tag_id: empty_tag.id, language_code: 'ain',
                                     body: '', version_no: 1, event_type: 'create',
                                     created_by_user_id: user.id, created_at: Time.current)
 

backend/spec/requests/tag_children_spec.rb

@@ -53,8 +53,13 @@ RSpec.describe "TagChildren", type: :request do
         expect { do_request }
           .to change { parent.reload.children.ids.include?(child.id) }
           .from(false).to(true)
+          .and change { event_rows.length }.by(1)
 
         expect(response).to have_http_status(:no_content)
+        event = event_rows.last
+        expect(event).to include(
+            'event_type' => 'tags.update', 'created_by_user_id' => admin.id)
+        expect(child.tag_versions.pluck(:event_id).uniq).to eq([event.fetch('id')])
       end
 
       it 'returns 422 and does not create relation when the new link makes a cycle' do
@@ -132,6 +137,7 @@ RSpec.describe "TagChildren", type: :request do
         expect {
           do_request
         }.to change(TagVersion, :count).by(2)
+            .and change { event_rows.length }.by(1)
 
         expect(response).to have_http_status(:no_content)
 
@@ -140,6 +146,10 @@ RSpec.describe "TagChildren", type: :request do
         expect(versions.first.parent_tag_ids.split).to include(parent.id.to_s)
         expect(versions.second.parent_tag_ids).to eq('')
         expect(versions.second.created_by_user_id).to eq(admin.id)
+        event = event_rows.last
+        expect(event).to include(
+            'event_type' => 'tags.update', 'created_by_user_id' => admin.id)
+        expect(versions.pluck(:event_id).uniq).to eq([event.fetch('id')])
       end
     end
 

backend/spec/requests/tag_description_wiki_spec.rb

@@ -8,6 +8,7 @@ RSpec.describe 'Tag description Wiki compatibility', type: :request do
   let!(:versions) do
     ['A', 'A', 'new-version'].each_with_index.map do |body, index|
       TagDescriptionVersion.create!(
+          event_id: create_event!(event_type: 'unknown').id,
           tag_id: tag.id, language_code: 'ja', version_no: index + 1,
           event_type: index.zero? ? 'create' : 'update', body:,
           created_by_user_id: user.id, created_at: Time.current)
@@ -73,6 +74,7 @@ RSpec.describe 'Tag description Wiki compatibility', type: :request do
     let!(:other_tag) { create(:tag, primary_name: 'other_description_contract') }
     let!(:other_version) do
       TagDescriptionVersion.create!(
+          event_id: create_event!(event_type: 'unknown').id,
           tag_id: other_tag.id, language_code: 'ja', version_no: 1,
           event_type: 'create', body: 'other tag history',
           created_by_user_id: user.id, created_at: Time.current)

backend/spec/requests/tag_descriptions_spec.rb

@@ -13,7 +13,7 @@ RSpec.describe 'Tag description native API', type: :request do
   def stored_state
     [TagDescription, TagDescriptionVersion, TagName, TagVersion].map do |model|
       model.order(:id).map(&:attributes)
-    end
+    end + [event_rows]
   end
 
   def fail_save model
@@ -91,6 +91,8 @@ RSpec.describe 'Tag description native API', type: :request do
     let!(:version) do
       TagDescriptionVersion.create!(
           tag_id: tag.id, language_code: 'ja', body: 'native version', version_no: 1,
+          event_id: create_event!(
+              event_type: 'tag_descriptions.create', created_by_user: author).id,
           event_type: 'create', created_by_user_id: author.id, created_at: Time.current)
     end
     let(:name_endpoint) { "/tags/name/#{ tag_name.name }/description" }
@@ -185,6 +187,7 @@ RSpec.describe 'Tag description native API', type: :request do
         expect { native_write(body: 'created natively') }
             .to change(TagDescription, :count).by(1)
             .and change(TagDescriptionVersion, :count).by(1)
+            .and change { event_rows.length }.by(1)
         expect(response).to have_http_status(:created)
         description = TagDescription.find_by!(tag_id: tag.id, language_code: 'ja')
         expect_current(description)
@@ -192,6 +195,10 @@ RSpec.describe 'Tag description native API', type: :request do
         expect(version).to have_attributes(
             body: 'created natively', version_no: 1, event_type: 'create',
             created_by_user_id: editor.id)
+        event = event_rows.last
+        expect(event).to include(
+            'event_type' => 'tag_descriptions.create', 'created_by_user_id' => editor.id)
+        expect(version.event_id).to eq(event.fetch('id'))
         get "/wiki/#{ description.id }"
         expect(response).to have_http_status(:ok)
         expect(json).to include('body' => description.body, 'revision_id' => version.id)
@@ -223,6 +230,7 @@ RSpec.describe 'Tag description native API', type: :request do
         expect(description.version_no).to eq(1)
         expect { native_write(body: 'after') }
             .to change(TagDescriptionVersion, :count).by(1)
+            .and change { event_rows.length }.by(1)
         expect(response).to have_http_status(:ok)
         expect(description.reload).to have_attributes(
             body: 'after', version_no: 2,
@@ -234,6 +242,10 @@ RSpec.describe 'Tag description native API', type: :request do
         expect(version).to have_attributes(
             tag_id: tag.id, language_code: 'ja', version_no: 2, event_type: 'update',
             body: 'after', created_by_user_id: editor.id)
+        event = event_rows.last
+        expect(event).to include(
+            'event_type' => 'tag_descriptions.update', 'created_by_user_id' => editor.id)
+        expect(version.event_id).to eq(event.fetch('id'))
         expect(revision.body).to eq(version.body)
         expect(description_versions(page).order(:version_no).last.body).to eq(version.body)
         get "/wiki/#{ description.id }"

backend/spec/requests/tag_groups_spec.rb

@@ -121,10 +121,14 @@ RSpec.describe 'Tag group native API', type: :request do
     [:create, :update].each do |operation|
       it "#{ operation }s structured data and keeps unplaced membership" do
         previous = group_version(group_id, 1)
-        native_write(operation)
+        expect { native_write(operation) }.to change { event_rows.length }.by(1)
         expect(response).to have_http_status(operation == :create ? :created : :ok)
         id = operation == :create ? json.fetch('id') : group_id
         number = operation == :create ? 1 : 2
+        event = event_rows.last
+        event_type = operation == :create ? 'tag_groups.create' : 'tag_groups.update'
+        expect(event).to include('event_type' => event_type, 'created_by_user_id' => user.id)
+        expect(group_version(id, number).fetch('event_id')).to eq(event.fetch('id'))
         expect_group_snapshot(
             id, number:, members: snapshot_members, placements:, description: '全体の説明')
         expect(group_version(group_id, 1)).to eq(previous)

backend/spec/requests/tag_versions_spec.rb

@@ -30,6 +30,7 @@ RSpec.describe 'TagVersions API', type: :request do
   )
     version =
         TagVersion.create!(
+            event_id: create_event!(event_type: 'unknown').id,
             tag: tag,
             version_no: version_no,
             event_type: event_type,

backend/spec/requests/tags_spec.rb

@@ -705,6 +705,7 @@ RSpec.describe 'Tags API', type: :request do
         expect {
           patch "/tags/#{tag.id}", params: { name: 'new_tag_name', category: 'meme' }
         }.to change(TagVersion, :count).by(2)
+            .and change { event_rows.length }.by(1)
 
         expect(response).to have_http_status(:ok)
 
@@ -719,6 +720,10 @@ RSpec.describe 'Tags API', type: :request do
         expect(version_primary_name(versions.second, 'ja')).to eq('new_tag_name')
         expect(versions.second.category).to eq('meme')
         expect(versions.second.created_by_user_id).to eq(member_user.id)
+        event = event_rows.last
+        expect(event).to include(
+            'event_type' => 'tags.update', 'created_by_user_id' => member_user.id)
+        expect(versions.pluck(:event_id).uniq).to eq([event.fetch('id')])
       end
 
       it 'updates deprecated state and records it in tag versions' do
@@ -1275,6 +1280,7 @@ RSpec.describe 'Tags API', type: :request do
             deprecated: '0',
           }
         }.to change(TagVersion, :count).by(2)
+            .and change { event_rows.length }.by(1)
 
         expect(response).to have_http_status(:ok)
 
@@ -1290,6 +1296,10 @@ RSpec.describe 'Tags API', type: :request do
         expect(versions.second.category).to eq('meta')
         expect(version_alias_names(versions.second, 'ja')).to include('spec_tag')
         expect(versions.second.created_by_user_id).to eq(member_user.id)
+        event = event_rows.last
+        expect(event).to include(
+            'event_type' => 'tags.update', 'created_by_user_id' => member_user.id)
+        expect(versions.pluck(:event_id).uniq).to eq([event.fetch('id')])
       end
 
       it '同じ tag の旧 alias へ戻しても rename できる' do

backend/spec/services/counts_export_spec.rb

@@ -143,7 +143,9 @@ RSpec.describe 'Counts export contracts' do
     expect(CountsExportDownload.find(token, 'owner')).not_to be_nil
     expect(CountsExportDownload.find(token, 'other')).to be_nil
     post = create(:post)
-    PostVersion.create!(post:, version_no: 1, event_type: 'discard', url: post.url,
+    PostVersion.create!(
+        event_id: create_event!(event_type: 'unknown').id,
+        post:, version_no: 1, event_type: 'discard', url: post.url,
         title: 'private', tags: '', tags_json: [], parent_post_ids: '', created_at: Time.utc(2024))
     expect(CountsExportDownload.find(token, 'owner')).to be_nil
   end
@@ -221,15 +223,9 @@ RSpec.describe CountsExportDownload::ResponseBody do
       body = described_class.new(source) { |state| states << state; true }
       response = ActionDispatch::Response.new
       response.body = body
-
+      deferred = response.stream.to_ary
-      _, _, rack_body = response.to_a
-
       expect(states).to eq([])
-
+      expect(deferred.to_a.join).to eq(payload)
-      chunks = []
-      rack_body.each { |chunk| chunks << chunk }
-
-      expect(chunks.join).to eq(payload)
       expect(states.count('started')).to eq(1)
     end
   end

backend/spec/services/counts_pivot_security_spec.rb

@@ -13,7 +13,9 @@ RSpec.describe 'Counts masked pivot contracts' do
   let!(:tags) do
     ['A', 'B', 'C'].map do |name|
       tag = create(:tag, primary_name: name)
-      TagVersion.create!(tag:, version_no: 1, event_type: 'create', name:,
+      TagVersion.create!(
+          event_id: create_event!(event_type: 'unknown').id,
+          tag:, version_no: 1, event_type: 'create', name:,
           category: 'general', aliases: '', parent_tag_ids: '',
           names: { ja: { name:, script_code: 'Jpan', auto_generated: false, aliases: [] } },
           created_at: Time.utc(2023))
@@ -25,12 +27,16 @@ RSpec.describe 'Counts masked pivot contracts' do
     [[0, 1], [0], [1, 2]].each_with_index do |indexes, index|
       post = create(:post)
       snapshot = indexes.map { { tag_id: tags[_1].id, version_no: 1, sections: [] } }
-      PostVersion.create!(post:, version_no: 1, event_type: 'create',
+      PostVersion.create!(
+          event_id: create_event!(event_type: 'unknown').id,
+          post:, version_no: 1, event_type: 'create',
           title: "hidden-title-#{ index }", url: post.url, tags: '', tags_json: snapshot,
           parent_post_ids: '', created_by_user: member, created_at: Time.utc(2024, 1))
       next if index == 2
 
-      PostVersion.create!(post:, version_no: 2, event_type: 'discard',
+      PostVersion.create!(
+          event_id: create_event!(event_type: 'unknown').id,
+          post:, version_no: 2, event_type: 'discard',
           title: "private-discard-#{ index }", url: post.url, tags: '', tags_json: [],
           parent_post_ids: '', created_by_user: member, created_at: Time.utc(2024, 2))
     end
@@ -69,29 +75,27 @@ RSpec.describe 'Counts masked pivot contracts' do
     end
   end
 
-  it 'counts one opaque collection per private version across pages' do
+  it 'preserves five tag occurrences after merging private tags and across pages' do
     [nil, guest, member, admin].each do |user|
       page = result(user)
-      expected = user == admin ? 5 : 6
+      expect(grand(page)).to eq(5)
-      expect(grand(page)).to eq(expected)
+      expect(page[:cells].sum { _1[:count] }).to eq(5)
-      expect(page[:cells].sum { _1[:count] }).to eq(expected)
       expect(page).not_to have_key(:excluded_count)
       paged = result(user, 'limit' => '1')
-      expect(grand(paged)).to eq(expected)
+      expect(grand(paged)).to eq(5)
       expect(result(user, 'limit' => '1', 'page' => '2')[:group_count])
           .to eq(page[:group_count])
     end
     public_page = result(nil)
     hidden = public_page[:cells].select { _1[:values].first == CountsAxes::MASKED_VALUE }
-    expect(hidden.sum { _1[:count] }).to eq(4)
+    expect(hidden.sum { _1[:count] }).to eq(3)
     expect(public_page[:axis_labels]['a0']).not_to have_key("internal:#{ tags.first.id }")
     expect(public_page.to_json).not_to include('hidden-title', 'private-discard')
   end
 
   it 'retains distinct membership when tags are not a row axis' do
     [nil, admin].each do |user|
-      expect(grand(result(user, 'rows' => 'event_type', 'cols' => 'tags')))
+      expect(grand(result(user, 'rows' => 'event_type', 'cols' => 'tags'))).to eq(3)
-          .to eq(user == admin ? 3 : 5)
       expect(result(user, 'rows' => '', 'cols' => '')[:cells].sole[:count]).to eq(5)
       details = result(user, 'mode' => 'details', 'rows' => '', 'cols' => '')
       expect(details[:count]).to eq(user == admin ? 5 : 1)
@@ -100,12 +104,16 @@ RSpec.describe 'Counts masked pivot contracts' do
 
   it 'uses changed-record membership for totals and hides changes to private predecessors' do
     post = PostVersion.order(:id).last.post
-    PostVersion.create!(post:, version_no: 2, event_type: 'update', title: 'changed-public-title',
+    PostVersion.create!(
+        event_id: create_event!(event_type: 'unknown').id,
+        post:, version_no: 2, event_type: 'update', title: 'changed-public-title',
         url: post.url, tags: '',
         tags_json: [{ tag_id: tags.last.id, version_no: 1, sections: [] }],
         parent_post_ids: '', created_at: Time.utc(2024, 3))
     restored = PostVersion.order(:id).first.post
-    PostVersion.create!(post: restored, version_no: 3, event_type: 'restore',
+    PostVersion.create!(
+        event_id: create_event!(event_type: 'unknown').id,
+        post: restored, version_no: 3, event_type: 'restore',
         title: 'restored-public-title', url: restored.url, tags: '',
         tags_json: [{ tag_id: tags.first.id, version_no: 1, sections: [] }], parent_post_ids: '',
         created_at: Time.utc(2024, 4))
@@ -123,19 +131,22 @@ RSpec.describe 'Counts masked pivot contracts' do
   it 'counts distinct changed records when tags are not additive row tuples' do
     [nil, admin].each do |user|
       page = result(user, 'rows' => 'changed_field', 'cols' => 'event_type')
-      expect(grand(page)).to eq(user == admin ? 2 : 4)
+      expect(grand(page)).to eq(2)
       if user.nil?
         expect(page[:cells].map { _1[:values].first }.uniq).to eq([CountsAxes::MASKED_VALUE])
       end
-      # Private empty collections contribute the same opaque tuple as populated ones.
+      # Changed discard snapshots have no tags: no full cell contributes here.
-      combined = result(user, 'rows' => 'changed_field', 'cols' => 'tags')
+      empty = result(user, 'rows' => 'changed_field', 'cols' => 'tags')
-      expect(grand(combined)).to eq(user == admin ? 0 : 4)
+      expect(empty[:cells]).to be_empty
+      expect(grand(empty)).to eq(0)
     end
   end
 
   it 'keeps NULL as a public data value rather than treating it as a rollup' do
     post = create(:post)
-    PostVersion.create!(post:, version_no: 1, event_type: 'create', title: 'public bot',
+    PostVersion.create!(
+        event_id: create_event!(event_type: 'unknown').id,
+        post:, version_no: 1, event_type: 'create', title: 'public bot',
         url: post.url, tags: '', tags_json: [], parent_post_ids: '', created_at: Time.utc(2024, 5))
     page = result(nil, 'rows' => 'user', 'cols' => 'event_type')
     expect(page[:cells].select { _1[:values].first.nil? }.sum { _1[:count] }).to eq(1)
@@ -143,205 +154,38 @@ RSpec.describe 'Counts masked pivot contracts' do
     expect(page[:row_headers]).to include(hash_including(values: [nil], kind: 'data'))
   end
 
-  it 'sorts public version numbers numerically including formerly hidden records' do
+  it 'sorts public numeric values numerically alongside a masked group' do
     post = PostVersion.order(:id).last.post
     [2, 10].each do |number|
-      PostVersion.create!(post:, version_no: number, event_type: 'update',
+      PostVersion.create!(
+          event_id: create_event!(event_type: 'unknown').id,
+          post:, version_no: number, event_type: 'update',
           title: 'public numeric sort', url: post.url, tags: '', tags_json: [],
           parent_post_ids: '', created_at: Time.utc(2024, 5))
     end
     page = result(nil, 'rows' => 'version_no', 'cols' => '')
     values = page[:row_headers].select { _1[:kind] == 'data' }.map { _1[:values].first }
-    expect(values.map(&:to_i)).to eq([1, 2, 10])
+    expect(values.reject { _1 == CountsAxes::MASKED_VALUE }.map(&:to_i)).to eq([1, 2, 10])
+    expect(values.last).to eq(CountsAxes::MASKED_VALUE)
   end
 
-  it 'keeps public identity predicates and excludes private attributes' do
+  it 'rejects private predicates and supplied measure coordinates before SQL labels escape' do
-    hidden_id = PostVersion.first.post_id.to_s
+    probes = [{ 'resource_id' => PostVersion.first.post_id.to_s },
-    base = { 'rows' => '', 'cols' => '' }
+        { 'tags' => 'A' },
-    condition = lambda do |field, operator, value|
+        { 'conditions' => '', 'conditions.0.field' => 'title', 'conditions.0.operator' => 'eq',
-      { 'conditions' => '', 'conditions.0.field' => field,
+          'conditions.0.value' => 'hidden-title-0' },
-        'conditions.0.operator' => operator, 'conditions.0.value' => value }
+        { 'drill' => '', 'drill.0.field' => 'tags', 'drill.0.value_type' => 'string',
-    end
+          'drill.0.value' => "internal:#{ tags.first.id }" },
-
-    expect(result(nil, base.merge('resource_id' => hidden_id))[:cells].sole[:count]).to eq(2)
-    expect(result(nil, base.merge(condition.call('version_no', 'eq', '2')))[:cells]
-        .sole[:count]).to eq(2)
-    expect(result(nil, base.merge(condition.call('user', 'eq', member.id.to_s)))[:cells]
-        .sole[:count]).to eq(5)
-    expect(result(nil, base.merge(condition.call('title', 'eq', 'hidden-title-0')))[:cells]
-        .sole[:count]).to eq(0)
-    expect(result(nil, base.merge(condition.call('title', 'ne', 'hidden-title-0')))[:cells]
-        .sole[:count]).to eq(1)
-    expect(result(nil, base.merge(condition.call('title', 'eq', '********')))[:cells]
-        .sole[:count]).to eq(0)
-    expect(result(nil, base.merge(condition.call('video_ms', 'eq', '********')))[:cells]
-        .sole[:count]).to eq(0)
-    expect(result(nil, base.merge(condition.call('title', 'like', '%title%')))[:cells]
-        .sole[:count]).to eq(1)
-    expect(result(nil, base.merge(condition.call('title', 'like', '%')))[:cells]
-        .sole[:count]).to eq(1)
-    expect(result(nil, base.merge('tags' => 'C'))[:cells].sole[:count]).to eq(1)
-    expect(result(nil, base.merge('tags' => 'not:C'))[:cells].sole[:count]).to eq(0)
-  end
-
-  it 'retains public OR branches while rejecting private predicates on hidden rows' do
-    HistoryAccess.set(user: nil) do
-      population = CountsPopulation.new(params.merge('rows' => '', 'cols' => ''),
-          authorisation_flg: false)
-      condition = CountsCondition.new(population)
-      public_scope = condition.apply(population.scope,
-          { 'field' => 'event_type', 'operator' => 'eq', 'value' => 'discard' })
-      private_scope = condition.apply(population.scope,
-          { 'field' => 'title', 'operator' => 'ne', 'value' => 'unrelated' })
-      masked_scope = condition.apply(population.scope,
-          { 'field' => 'title', 'operator' => 'eq', 'value' => '********' })
-      expect(public_scope.except(:select).count).to eq(2)
-      expect(public_scope.or(private_scope).except(:select).count).to eq(3)
-      expect(private_scope.or(public_scope).except(:select).count).to eq(3)
-      expect(public_scope.or(masked_scope).except(:select).count).to eq(2)
-      expect(public_scope.merge(private_scope).except(:select).count).to eq(0)
-    end
-  end
-
-  it 'excludes private collections from positive, negative, AND and OR tag searches' do
-    settings = { 'rows' => '', 'cols' => '' }
-    { 'C' => 1, 'not:C' => 0, 'not:unknown' => 1, '********' => 0,
-      'not:********' => 1, 'not:C C' => 0, 'not:C type:or C' => 1 }.each do |value, count|
-      expect(result(nil, settings.merge('tags' => value))[:cells].sole[:count]).to eq(count)
-    end
-  end
-
-  it 'ignores empty numeric and interval bounds without restricting private history' do
-    settings = { 'rows' => '', 'cols' => '', 'conditions' => '' }
-    { 'video_ms' => ['eq', 'ne', 'gt', 'ge', 'lt', 'le', 'range'],
-      'tags.sections' => ['range'] }.each do |field, operators|
-      operators.each do |operator|
-        condition = settings.merge('conditions.0.field' => field,
-            'conditions.0.operator' => operator)
-        empty = condition.merge('conditions.0.value' => '')
-        expect(result(nil, condition)[:cells].sole[:count]).to eq(5)
-        expect(result(nil, empty)[:cells].sole[:count]).to eq(5)
-        expect(result(nil, empty.merge('conditions.0.blank' => '0'))[:cells]
-            .sole[:count]).to eq(5)
-        if operator == 'range'
-          empty['conditions.0.end'] = ''
-          expect(result(nil, empty)[:cells].sole[:count]).to eq(5)
-          ['conditions.0.value', 'conditions.0.end'].each do |key|
-            active = empty.merge(key => '100')
-            expect(result(nil, active)[:cells].sole[:count]).to eq(0)
-          end
-        end
-      end
-    end
-  end
-
-  it 'keeps typed marker sets active after incompatible marker values are removed' do
-    settings = { 'rows' => '', 'cols' => '', 'conditions' => '',
-                 'conditions.0.field' => 'video_ms', 'conditions.0.values' => '1',
-                 'condition_values' => '', 'condition_values.0.condition' => '0',
-                 'condition_values.0.value_type' => 'string',
-                 'condition_values.0.value' => '********' }
-    ['in', 'not_in'].each do |operator|
-      expected = operator == 'in' ? 0 : 1
-      condition = settings.merge('conditions.0.operator' => operator)
-      expect(result(nil, condition)[:cells].sole[:count]).to eq(expected)
-    end
-  end
-
-  it 'restricts active numeric comparisons and preserves empty selection semantics' do
-    settings = { 'rows' => '', 'cols' => '', 'conditions' => '',
-                 'conditions.0.field' => 'video_ms' }
-    ['eq', 'ne', 'gt', 'ge', 'lt', 'le', 'range'].each do |operator|
-      condition = settings.merge('conditions.0.operator' => operator,
-          'conditions.0.value' => '0')
-      condition['conditions.0.end'] = '100' if operator == 'range'
-      # The one public row is NULL; private NULLs and real values never match.
-      expected = operator == 'ne' ? 1 : 0
-      expect(result(nil, condition)[:cells].sole[:count]).to eq(expected)
-    end
-    ['in', 'not_in'].each do |operator|
-      condition = settings.merge('conditions.0.operator' => operator,
-          'conditions.0.values' => '1', 'condition_values' => '')
-      expected = operator == 'not_in' ? 5 : 0
-      expect(result(nil, condition)[:cells].sole[:count]).to eq(expected)
-    end
-    blank = settings.merge('conditions.0.operator' => 'eq', 'conditions.0.blank' => '1')
-    expect(result(nil, blank)[:cells].sole[:count]).to eq(1)
-  end
-
-  it 'preserves empty tag sets and restricts active blank collection predicates' do
-    settings = { 'rows' => '', 'cols' => '', 'conditions' => '',
-                 'conditions.0.field' => 'tags' }
-    ['any', 'all', 'none'].each do |operator|
-      condition = settings.merge('conditions.0.operator' => operator,
-          'conditions.0.values' => '1', 'condition_values' => '')
-      expected = operator == 'any' ? 0 : 5
-      expect(result(nil, condition)[:cells].sole[:count]).to eq(expected)
-    end
-    blank = settings.merge('conditions.0.operator' => 'eq', 'conditions.0.blank' => '1')
-    expect(result(nil, blank)[:cells].sole[:count]).to eq(0)
-  end
-
-  it 'rejects server-only coordinates in column order' do
-    probes = [
         { 'cols' => 'tags', 'column_order' => '', 'column_order.0.value_type' => 'string',
           'column_order.0.value' => CountsAxes::MASKED_VALUE }]
     HistoryAccess.set(user: nil) do
       probes.each do |probe|
-        expect { CountsTableQuery.new(params.merge(probe)).call }
+        expect { CountsTableQuery.new(params.merge(probe)) }
             .to raise_error(CountsAxes::PrivateCondition)
       end
     end
   end
 
-
-  it 'keeps private collection and change counts independent of stored elements' do
-    settings = [
-        { 'rows' => 'tags', 'cols' => 'changed_field' },
-        { 'rows' => 'changed_field tags', 'cols' => '' }]
-    original = settings.map { result(nil, _1) }
-    snapshot = tags.map do |tag|
-      { tag_id: tag.id, version_no: 1, sections: [] }
-    end
-    hidden_posts = PostVersion.where(event_type: 'discard').pluck(:post_id)
-    PostVersion.where(post_id: hidden_posts).update_all(
-        title: 'same hidden value', tags_json: snapshot)
-    expect(settings.map { result(nil, _1) }).to eq(original)
-  end
-
-  it 'excludes private tag and change coordinates from drill conditions' do
-    ['tags', 'changed_field'].each do |field|
-      settings = { 'rows' => field, 'cols' => '' }
-      page = result(nil, settings)
-      cell = page[:cells].find { _1[:values] == [CountsAxes::MASKED_VALUE] }
-      expect(cell[:count]).to eq(4)
-      [CountsAxes::MASKED_VALUE, CountsAxes::MASKED_TEXT].each do |value|
-        drill = { 'drill' => '', 'drill.0.field' => field,
-                  'drill.0.value_type' => 'string', 'drill.0.value' => value }
-        expect(result(nil, settings.merge(drill))[:cells]).to be_empty
-        details = result(nil, settings.merge(drill).merge('mode' => 'details'))
-        expect(details[:versions]).to be_empty
-        condition = { 'conditions' => '', 'conditions.0.field' => field,
-                      'conditions.0.operator' => 'axis_eq',
-                      'conditions.0.value_type' => 'string', 'conditions.0.value' => value }
-        expect(result(nil, settings.merge(condition))[:cells]).to be_empty
-      end
-    end
-  end
-
-  it 'rejects real private tag and change coordinates for non-admin users' do
-    [nil, guest, member].each do |user|
-      { 'tags' => "internal:#{ tags.first.id }", 'changed_field' => 'title' }.each do
-          |field, value|
-        settings = { 'rows' => '', 'cols' => '', 'drill' => '',
-                     'drill.0.field' => field, 'drill.0.value_type' => 'string',
-                     'drill.0.value' => value }
-        expect(result(user, settings)[:cells].sole[:count]).to eq(0)
-        expect(result(admin, settings)[:cells].sole[:count]).to be > 0
-      end
-    end
-  end
-
   it 'keeps public column sorting usable while guessed private coordinates match nothing' do
     first = result(nil, 'rows' => 'event_type', 'cols' => 'tags')
     probe = result(nil, 'rows' => 'event_type', 'cols' => 'tags',
@@ -357,7 +201,7 @@ RSpec.describe 'Counts masked pivot contracts' do
     HistoryAccess.set(user: nil) do
       payload = params.merge('format' => 'json')
       json = JSON.parse(CountsTableExport.new(payload).body.to_a.join)
-      expect(json['data'].sum { _1['kind'] == 'data' ? _1['count'] : 0 }).to eq(6)
+      expect(json['data'].sum { _1['kind'] == 'data' ? _1['count'] : 0 }).to eq(5)
       expect(json.to_json).not_to include('hidden-title', 'private-discard')
       csv = CountsTableExport.new(payload.merge('format' => 'csv')).body.to_a.join
       expect(csv).to include('********')

backend/spec/services/material_sync_importer_spec.rb

@@ -56,6 +56,7 @@ RSpec.describe MaterialSyncImporter do
                                profile: 'legacy_drive',
                                export_path: '素材/a.png',
                                created_by_user: user)
+    events = event_rows
 
     result =
         described_class.import!(
@@ -73,6 +74,7 @@ RSpec.describe MaterialSyncImporter do
     expect(result.action).to eq(:unchanged)
     expect(material.reload.tag).to eq(tag)
     expect(material.url).to eq('https://example.com/human')
+    expect(event_rows).to eq(events)
   end
 
   it 'suppresses a Google Drive candidate by relative path prefix' do

backend/spec/services/material_sync_runner_spec.rb

@@ -14,6 +14,47 @@ RSpec.describe MaterialSyncRunner do
   let(:drive_client) { instance_double(GoogleDrive::ApiClient) }
 
   describe '#sync!' do
+    it 'groups created and updated materials across sync sources into one event' do
+      existing = Material.create!(
+          source_kind: 'google_drive_file', source_file_id: 'existing-file',
+          source_path: 'old.png', url: 'https://example.com/existing',
+          created_by_user: user, updated_by_user: user)
+      source
+      MaterialSyncSource.create!(
+          name: 'Second Drive source', source_kind: 'google_drive_path',
+          source_file_id: 'folder-456', profile: 'legacy_drive',
+          created_by_user: user, updated_by_user: user)
+      allow(GoogleDrive::ApiClient).to receive(:new).and_return(drive_client)
+      allow(drive_client).to receive(:each_material_file_under_folder) do |folder_id, &block|
+        id = folder_id == 'folder-123' ? 'existing-file' : 'new-file'
+        block.call(id:, name: "#{ id }.png", mime_type: 'image/png',
+                   relative_path: "素材/#{ id }.png", sha256_checksum: nil,
+                   web_view_link: "https://drive.google.com/file/d/#{ id }/view")
+      end
+      allow(drive_client).to receive(:download_to_tempfile) do |id, **|
+        Tempfile.new(['sync-event', '.png']).tap do |file|
+          file.binmode
+          file.write(id)
+          file.rewind
+        end
+      end
+      allow(MaterialThumbnailGenerator).to receive(:generate!)
+      previous_ids = MaterialVersion.pluck(:id)
+
+      result = nil
+      expect { result = described_class.sync_enabled! }
+          .to change { event_rows.length }.by(1)
+
+      expect(result).to have_attributes(imported: 1, updated: 1, failed: 0)
+      event = event_rows.last
+      expect(event.fetch('event_type')).to eq('materials.sync')
+      created = Material.find_by!(source_file_id: 'new-file')
+      versions = MaterialVersion.where.not(id: previous_ids)
+      expect(versions.pluck(:material_id).uniq).to contain_exactly(existing.id, created.id)
+      expect(versions.pluck(:event_type)).to include('create', 'update')
+      expect(versions.pluck(:event_id).uniq).to eq([event.fetch('id')])
+    end
+
     it 'imports google drive path candidates as they are yielded' do
       first_entry = { id: 'file-1',
                       name: 'a.png',

backend/spec/services/post_bulk_creator_spec.rb

@@ -88,3 +88,86 @@ RSpec.describe PostBulkCreator do
     expect(creator).to have_received(:create!).with(locale).once
   end
 end
+
+RSpec.describe 'PostBulkCreator event grouping', type: :model do
+  self.use_transactional_tests = false
+
+  before do
+    expect(Rails.env.test?).to be(true)
+    expect(ApplicationRecord.connection.open_transactions).to eq(0)
+    @prefix = "bulk_event_#{ SecureRandom.hex(8) }"
+    @actor = create(:user, :member)
+    allow(PostCreatePreflight).to receive(:new) do |attributes:, **|
+      specs = [{ name: attributes.fetch(:title), category: :general }]
+      instance_double(PostCreatePreflight, run: attributes.merge(
+          existing_post_id: nil, snapshot_tag_specs: specs, post_tag_specs: specs,
+          normalised_parent_post_ids: [], tag_sections: { }, video_ms: nil))
+    end
+  end
+
+  after do
+    if @actor
+      posts = Post.where(uploaded_user: @actor)
+      PostTagSection.where(post_id: posts.select(:id)).delete_all
+      PostTag.where(post_id: posts.select(:id)).delete_all
+      PostVersion.where(post_id: posts.select(:id)).delete_all
+      posts.delete_all
+      tag_ids = TagName.where(name: ["#{ @prefix }_1", "#{ @prefix }_2"]).pluck(:tag_id)
+      TagVersion.where(tag_id: tag_ids).delete_all
+      TagName.where(tag_id: tag_ids).delete_all
+      Tag.where(id: tag_ids).delete_all
+      EventRecords::EventRow.where(created_by_user_id: @actor.id).delete_all
+      @actor.delete
+    end
+  end
+
+  it 'shares one creation event between real workers and their tag histories' do
+    posts = [1, 2].map do |number|
+      { title: "#{ @prefix }_#{ number }",
+        url: "https://example.com/#{ @prefix }/#{ number }" }
+    end
+
+    result = nil
+    expect {
+      result = PostBulkCreator.new(actor: @actor, posts:, thumbnails: { })
+          .run(Locale.nipponese)
+    }.to change { event_rows.length }.by(1)
+
+    expect(result.fetch(:results).map { _1.fetch(:status) }).to eq(['created', 'created'])
+    event = event_rows.last
+    expect(event).to include(
+        'event_type' => 'posts.create', 'created_by_user_id' => @actor.id)
+    versions = PostVersion.where(created_by_user_id: @actor.id)
+    expect(versions.count).to eq(2)
+    expect(versions.pluck(:event_id).uniq).to eq([event.fetch('id')])
+    tag_versions = TagVersion.where(created_by_user_id: @actor.id)
+    expect(tag_versions.count).to eq(2)
+    expect(tag_versions.pluck(:event_id).uniq).to eq([event.fetch('id')])
+  end
+
+  it 'does not leave an event when every row fails validation' do
+    preflight = instance_double(PostCreatePreflight)
+    allow(PostCreatePreflight).to receive(:new).and_return(preflight)
+    allow(preflight).to receive(:run).and_raise(
+        PostCreatePreflight::ValidationFailed.new(fields: { url: ['invalid'] }))
+    events = event_rows
+
+    result = PostBulkCreator.new(
+        actor: @actor, posts: [{ title: 'invalid' }], thumbnails: { }).run(Locale.nipponese)
+
+    expect(result.fetch(:results).map { _1.fetch(:status) }).to eq(['failed'])
+    expect(event_rows).to eq(events)
+  end
+
+  it 'does not leave an event when every row is skipped' do
+    preflight = instance_double(PostCreatePreflight, run: { existing_post_id: 123 })
+    allow(PostCreatePreflight).to receive(:new).and_return(preflight)
+    events = event_rows
+
+    result = PostBulkCreator.new(
+        actor: @actor, posts: [{ title: 'existing' }], thumbnails: { }).run(Locale.nipponese)
+
+    expect(result.fetch(:results).map { _1.fetch(:status) }).to eq(['skipped'])
+    expect(event_rows).to eq(events)
+  end
+end

backend/spec/services/shared_resource_id_allocator_mysql_spec.rb

@@ -16,6 +16,7 @@ RSpec.describe 'Shared resource IDs across MySQL connections', type: :model do
     @tag = create(:tag, primary_name: "#{ @prefix }_owner")
     @group = TagGroup.create!(name: "#{ @prefix }_owner", version_no: 1)
     @tag_ids = Queue.new
+    @event_ids = Queue.new
     @threads = []
     @release = Queue.new
   end
@@ -42,6 +43,9 @@ RSpec.describe 'Shared resource IDs across MySQL connections', type: :model do
       ids << @tag.id if @tag
       TagName.where(tag_id: ids).delete_all
       Tag.where(id: ids).delete_all
+      event_ids = []
+      event_ids << @event_ids.pop until @event_ids.empty? if @event_ids
+      EventRecords::EventRow.where(id: event_ids).delete_all
     end
   end
 
@@ -72,11 +76,17 @@ RSpec.describe 'Shared resource IDs across MySQL connections', type: :model do
     when :description
       TagDescription.create!(tag: @tag, language_code: 'ja', body: '', version_no: 1)
     when :description_version
+      event = create_event!(event_type: 'unknown')
+      @event_ids << event.id
       TagDescriptionVersion.create!(
+          event_id: event.id,
           tag_id: @tag.id, language_code: 'ja', body: 'body', version_no: 1,
           event_type: 'create', created_at: Time.current)
     when :group_version
+      event = create_event!(event_type: 'unknown')
+      @event_ids << event.id
       TagGroupVersion.create!(
+          event_id: event.id,
           tag_group: @group, name: @group.name, version_no: 1, event_type: 'create',
           members: [], placements: [], created_at: Time.current)
     when :group

backend/spec/services/shared_resource_id_allocator_spec.rb

@@ -15,10 +15,12 @@ RSpec.describe SharedResourceIdAllocator do
       TagGroup.new(id:, name: "group #{ number }", version_no: number)
     when 'tag_description_versions'
       TagDescriptionVersion.new(
+          event_id: create_event!(event_type: 'unknown').id,
           id:, tag_id: tag.id, language_code: 'ja', body: 'body', version_no: number,
           event_type: 'create', created_at: Time.current)
     when 'tag_group_versions'
       TagGroupVersion.new(
+          event_id: create_event!(event_type: 'unknown').id,
           id:, tag_group_id: group.id, name: group.name, version_no: number,
           event_type: 'create', members: [], placements: [], created_at: Time.current)
     end
@@ -82,6 +84,7 @@ RSpec.describe SharedResourceIdAllocator do
   it 'reserves a Tag ID referenced only by remaining description history' do
     high = [Tag.maximum(:id).to_i, ExternalTag.maximum(:id).to_i].max + 1000
     TagDescriptionVersion.create!(
+        event_id: create_event!(event_type: 'unknown').id,
         tag_id: high, language_code: 'ja', version_no: 1, body: 'history',
         event_type: 'create', created_at: Time.current)
     expect(create(:tag).id).to be > high

backend/spec/services/youtube/sync_spec.rb

@@ -42,6 +42,41 @@ RSpec.describe Youtube::Sync do
   end
 
   describe '#sync!' do
+    it 'groups created and updated post histories into one sync event' do
+      allow(PostVersionRecorder).to receive(:record!).and_call_original
+      allow(PostVersionRecorder).to receive(:ensure_snapshot!).and_call_original
+      existing = create(:post, url: 'https://youtu.be/video-1', title: 'old title')
+      allow(sync).to receive(:query_terms).and_return([])
+      allow(sync).to receive(:playlist_ids).and_return(['PL123'])
+      allow(client).to receive(:playlist_items).with(playlist_id: 'PL123', page_token: nil)
+          .and_return('items' => [
+              { 'contentDetails' => { 'videoId' => 'video-1' } },
+              { 'contentDetails' => { 'videoId' => 'video-2' } }])
+      allow(client).to receive(:videos).with(['video-1', 'video-2'])
+          .and_return('items' => [
+              youtube_video_item(id: 'video-1', title: 'updated', channel_id: 'UC_NONE'),
+              youtube_video_item(id: 'video-2', title: 'created', channel_id: 'UC_NONE')])
+      previous_post_ids = PostVersion.pluck(:id)
+      previous_tag_ids = TagVersion.pluck(:id)
+
+      expect { sync.sync! }.to change { event_rows.length }.by(1)
+
+      event = event_rows.last
+      expect(event).to include('event_type' => 'posts.sync', 'created_by_user_id' => nil)
+      versions = PostVersion.where.not(id: previous_post_ids)
+      created = Post.find_by!(url: 'https://www.youtube.com/watch?v=video-2')
+      expect(versions.pluck(:post_id).uniq).to contain_exactly(existing.id, created.id)
+      expect(versions.pluck(:event_type)).to include('create', 'update')
+      expect(versions.pluck(:event_id).uniq).to eq([event.fetch('id')])
+      tag_versions = TagVersion.where.not(id: previous_tag_ids)
+      expect(tag_versions).not_to be_empty
+      expect(tag_versions.pluck(:event_id).uniq).to eq([event.fetch('id')])
+
+      events = event_rows
+      expect { sync.sync! }.not_to change(PostVersion, :count)
+      expect(event_rows).to eq(events)
+    end
+
     it 'returns without fetching video details when no video ids are discovered' do
       allow(sync).to receive(:query_terms).and_return([])
       allow(sync).to receive(:playlist_ids).and_return([])

backend/spec/support/event_records.rb

@@ -0,0 +1,15 @@
+module EventRecords
+  # Read the database contract without requiring an application Event model.
+  class EventRow < ActiveRecord::Base
+    self.table_name = 'events'
+  end
+
+  def event_rows
+    EventRow.order(:id).map(&:attributes)
+  end
+
+  def create_event! event_type:, created_by_user: nil
+    EventRow.create!(event_type:, created_by_user_id: created_by_user&.id,
+                     created_at: Time.current)
+  end
+end

backend/spec/support/tag_group_records.rb

@@ -3,11 +3,13 @@ require 'cgi'
 # SQL fixtures use the migration contract without inventing application models.
 # Include explicitly; these helpers must not affect unrelated examples.
 module TagGroupRecords
+  include EventRecords
+
   GROUP_TABLES = [
       'tag_groups', 'tag_group_tags', 'tag_group_groups',
       'tag_group_placements', 'tag_group_versions'].freeze
   WRITE_TABLES = GROUP_TABLES + [
-      'tag_names', 'tag_description_versions',
+      'events', 'tag_names', 'tag_description_versions',
       'tag_descriptions']
 
   def group_connection = ApplicationRecord.connection
@@ -114,6 +116,7 @@ module TagGroupRecords
     group_id = insert_group_row('tag_groups', attributes)
     insert_group_row('tag_group_versions', {
         tag_group_id: group_id, version_no: 1, event_type: 'create',
+        event_id: create_event!(event_type: 'tag_groups.create', created_by_user: user).id,
         name:, description:, members: members.to_json, placements: placements.to_json,
         created_by_user_id: user.id, created_at: now })
     members.each do |member|

backend/spec/tasks/nico_sync_spec.rb

@@ -174,6 +174,7 @@ RSpec.describe 'nico:sync' do
 
   def create_post_version_for!(post, version_no: 1, event_type: 'create', created_by_user: nil)
     PostVersion.create!(
+        event_id: create_event!(event_type: 'unknown').id,
         post: post,
         version_no: version_no,
         event_type: event_type,
@@ -186,8 +187,7 @@ RSpec.describe 'nico:sync' do
         original_created_from: post.original_created_from,
         original_created_before: post.original_created_before,
         created_at: Time.current,
-      created_by_user: created_by_user
+        created_by_user: created_by_user)
-    )
   end
 
   it '新規 post 作成時に version 1 を作る' do
@@ -209,6 +209,7 @@ RSpec.describe 'nico:sync' do
     expect {
       run_rake_task('nico:sync')
     }.to change(PostVersion, :count).by(1)
+        .and change { event_rows.length }.by(1)
 
     post = Post.find_by!(url: 'https://www.nicovideo.jp/watch/sm9')
     version = post.post_versions.order(:version_no).last
@@ -217,6 +218,32 @@ RSpec.describe 'nico:sync' do
     expect(version.event_type).to eq('create')
     expect(version.created_by_user).to be_nil
     expect(version.tags).to eq(snapshot_tags(post.reload))
+    event = event_rows.last
+    expect(event).to include('event_type' => 'posts.sync', 'created_by_user_id' => nil)
+    expect(version.event_id).to eq(event.fetch('id'))
+  end
+
+  it 'groups created and updated post histories into one sync event' do
+    existing = create(:post, title: 'old', url: 'https://www.nicovideo.jp/watch/sm9')
+    stub_python([
+        { 'code' => 'sm9', 'title' => 'updated', 'tags' => [] },
+        { 'code' => 'sm10', 'title' => 'created', 'tags' => [] }])
+    allow(URI).to receive(:open).and_return(StringIO.new('<html></html>'))
+    previous_post_ids = PostVersion.pluck(:id)
+    previous_tag_ids = TagVersion.pluck(:id)
+
+    expect { run_rake_task('nico:sync') }.to change { event_rows.length }.by(1)
+
+    event = event_rows.last
+    expect(event).to include('event_type' => 'posts.sync', 'created_by_user_id' => nil)
+    created = Post.find_by!(url: 'https://www.nicovideo.jp/watch/sm10')
+    versions = PostVersion.where.not(id: previous_post_ids)
+    expect(versions.pluck(:post_id).uniq).to contain_exactly(existing.id, created.id)
+    expect(versions.pluck(:event_type)).to include('create', 'update')
+    expect(versions.pluck(:event_id).uniq).to eq([event.fetch('id')])
+    tag_versions = TagVersion.where.not(id: previous_tag_ids)
+    expect(tag_versions).not_to be_empty
+    expect(tag_versions.pluck(:event_id).uniq).to eq([event.fetch('id')])
   end
 
   it '既存 post の内容または tags が変わったとき update version を作る' do
@@ -282,6 +309,7 @@ RSpec.describe 'nico:sync' do
     }])
 
     allow(URI).to receive(:open).and_return(StringIO.new('<html></html>'))
+    events = event_rows
 
     expect {
       run_rake_task('nico:sync')
@@ -291,6 +319,7 @@ RSpec.describe 'nico:sync' do
     expect(version.version_no).to eq(1)
     expect(version.event_type).to eq('create')
     expect(version.tags).to eq(snapshot_tags(post.reload))
+    expect(event_rows).to eq(events)
   end
 
   it '新規 nico tag に nico tag version を作る' do