#329

#317

#317

#317

#317

#317

#317

Co-authored-by: miteruzo <miteruzo@naver.com>
Reviewed-on: #333

backend/app/controllers/nico_tags_controller.rb

@@ -30,15 +30,21 @@ class NicoTagsController < ApplicationController
     id = params[:id].to_i
 
     tag = Tag.find(id)
-    return head :bad_request if tag.category != 'nico'
+    return head :bad_request unless tag.nico?
 
-    linked_tag_names = params[:tags].to_s.split(' ')
+    linked_tag_names = params[:tags].to_s.split
     linked_tags = Tag.normalise_tags(linked_tag_names, with_tagme: false,
                                                        with_no_deerjikist: false)
-    return head :bad_request if linked_tags.any? { |t| t.category == 'nico' }
+    return head :bad_request if linked_tags.any? { |t| t.nico? }
 
-    tag.linked_tags = linked_tags
+    ApplicationRecord.transaction do
-    tag.save!
+      TagVersioning.record_tag_snapshots!(linked_tags, created_by_user: current_user)
+
+      tag.linked_tags = linked_tags
+      tag.save!
+
+      NicoTagVersionRecorder.record!(tag:, event_type: :update, created_by_user: current_user)
+    end
 
     render json: tag.linked_tags.map { |t| TagRepr.base(t) }, status: :ok
   end

backend/app/controllers/posts_controller.rb

@@ -128,9 +128,11 @@ class PostsController < ApplicationController
                     original_created_from:, original_created_before:)
     post.thumbnail.attach(thumbnail)
 
-    ActiveRecord::Base.transaction do
+    ApplicationRecord.transaction do
       post.save!
       tags = Tag.normalise_tags(tag_names)
+      TagVersioning.record_tag_snapshots!(tags, created_by_user: current_user)
+
       tags = Tag.expand_parent_tags(tags)
       sync_post_tags!(post, tags)
       post.resized_thumbnail!
@@ -170,10 +172,15 @@ class PostsController < ApplicationController
 
     post = Post.find(params[:id].to_i)
 
-    ActiveRecord::Base.transaction do
+    ApplicationRecord.transaction do
+      PostVersionRecorder.ensure_snapshot!(post, created_by_user: current_user)
+
       post.update!(title:, original_created_from:, original_created_before:)
-      tags = post.tags.where(category: 'nico').to_a +
+
-             Tag.normalise_tags(tag_names, with_tagme: false)
+      normalised_tags = Tag.normalise_tags(tag_names, with_tagme: false)
+      TagVersioning.record_tag_snapshots!(normalised_tags, created_by_user: current_user)
+
+      tags = post.tags.nico.to_a + normalised_tags
       tags = Tag.expand_parent_tags(tags)
       sync_post_tags!(post, tags)
       PostVersionRecorder.record!(post:, event_type: :update, created_by_user: current_user)

backend/app/controllers/tag_children_controller.rb

@@ -7,7 +7,16 @@ class TagChildrenController < ApplicationController
     child_id = params[:child_id]
     return head :bad_request if parent_id.blank? || child_id.blank?
 
-    Tag.find(parent_id).children << Tag.find(child_id) rescue nil
+    parent = Tag.find(parent_id)
+    child = Tag.find(child_id)
+    return head :bad_request if parent.nico? || child.nico?
+
+    ApplicationRecord.transaction do
+      TagVersioning.ensure_snapshot!(child, created_by_user: current_user)
+
+      TagImplication.find_or_create_by!(parent_tag: parent, tag: child)
+      TagVersionRecorder.record!(tag: child, event_type: :update, created_by_user: current_user)
+    end
 
     head :no_content
   end
@@ -20,7 +29,16 @@ class TagChildrenController < ApplicationController
     child_id = params[:child_id]
     return head :bad_request if parent_id.blank? || child_id.blank?
 
-    Tag.find(parent_id).children.delete(Tag.find(child_id)) rescue nil
+    parent = Tag.find(parent_id)
+    child = Tag.find(child_id)
+    return head :bad_request if parent.nico? || child.nico?
+
+    ApplicationRecord.transaction do
+      TagVersioning.ensure_snapshot!(child, created_by_user: current_user)
+
+      TagImplication.find_by(parent_tag: parent, tag: child)&.destroy!
+      TagVersionRecorder.record!(tag: child, event_type: :update, created_by_user: current_user)
+    end
 
     head :no_content
   end

backend/app/controllers/tag_versions_controller.rb

@@ -0,0 +1,92 @@
+class TagVersionsController < ApplicationController
+  def index
+    tag_id = params[:id].presence
+    page = (params[:page].presence || 1).to_i
+    limit = (params[:limit].presence || 20).to_i
+
+    page = 1 if page < 1
+    limit = 1 if limit < 1
+
+    offset = (page - 1) * limit
+
+    q = TagVersion.joins(<<~SQL.squish)
+          LEFT JOIN
+            tag_versions prev
+            ON
+              prev.tag_id = tag_versions.tag_id
+              AND prev.version_no = tag_versions.version_no - 1
+        SQL
+      .select('tag_versions.*', 'prev.name AS prev_name', 'prev.category AS prev_category',
+              'prev.aliases AS prev_aliases', 'prev.parent_tag_ids AS prev_parent_tag_ids')
+    q = q.where('tag_versions.tag_id = ?', tag_id) if tag_id
+
+    count = q.except(:select, :order, :limit, :offset).count
+
+    versions = q.order(Arel.sql('tag_versions.created_at DESC, tag_versions.id DESC'))
+                .limit(limit)
+                .offset(offset)
+
+    render json: { versions: serialise_versions(versions), count: }
+  end
+
+  private
+
+  def serialise_versions rows
+    user_ids = rows.map(&:created_by_user_id).compact.uniq
+    users_by_id = User.where(id: user_ids).pluck(:id, :name).to_h
+
+    rows.map do |row|
+      cur_aliases = split_values(row.aliases)
+      prev_aliases = split_values(row.attributes['prev_aliases'])
+
+      cur_parent_tag_ids = split_parent_tag_ids(row.parent_tag_ids)
+      prev_parent_tag_ids = split_parent_tag_ids(row.attributes['prev_parent_tag_ids'])
+
+      all_parent_tag_ids = (cur_parent_tag_ids | prev_parent_tag_ids)
+
+      tags_by_id =
+          Tag
+          .includes(:tag_name, :materials, { tag_name: :wiki_page })
+          .where(id: all_parent_tag_ids)
+          .index_by(&:id)
+
+      parent_tags =
+          build_version_values(cur_parent_tag_ids, prev_parent_tag_ids, key: :tag_id)
+          .map do |h|
+            { tag: TagRepr.base(tags_by_id[h[:tag_id]]),
+              type: h[:type] }
+          end
+
+      { tag_id: row.tag_id,
+        version_no: row.version_no,
+        event_type: row.event_type,
+        name: { current: row.name, prev: row.attributes['prev_name'] },
+        category: { current: row.category, prev: row.attributes['prev_category'] },
+        aliases: build_version_values(cur_aliases, prev_aliases, key: :name),
+        parent_tags:,
+        created_at: row.created_at.iso8601,
+        created_by_user: row.created_by_user_id &&
+                         { id: row.created_by_user_id,
+                           name: users_by_id[row.created_by_user_id] } }
+    end
+  end
+
+  def build_version_values cur_values, prev_values, key:
+    (cur_values | prev_values).map do |value|
+      type =
+          if cur_values.include?(value) && prev_values.include?(value)
+            'context'
+          elsif cur_values.include?(value)
+            'added'
+          else
+            'removed'
+          end
+
+      { key => value, type: }
+    end
+  end
+
+  def split_values(values) = values.to_s.split(/\s+/).reject(&:blank?)
+
+  def split_parent_tag_ids(values) = split_values(values).map(&:to_i)
+end

backend/app/controllers/tags_controller.rb

@@ -66,7 +66,7 @@ class TagsController < ApplicationController
             .offset(offset)
             .to_a
 
-    render json: { tags: TagRepr.base(tags), count: q.size }
+    render json: { tags: TagRepr.many(tags), count: q.size }
   end
 
   def with_depth
@@ -209,6 +209,60 @@ class TagsController < ApplicationController
     render json: build_tag_children(tag)
   end
 
+  def update_all
+    return head :unauthorized unless current_user
+    return head :forbidden unless current_user.gte_member?
+
+    tag = Tag.find_by(id: params[:id])
+    return head :not_found unless tag
+
+    name = params[:name].to_s.strip
+    category = params[:category].to_s.strip
+    return head :unprocessable_entity if name.blank? || category.blank?
+
+    if name != tag.name &&
+        tag.in?([Tag.tagme, Tag.bot, Tag.no_deerjikist, Tag.video, Tag.niconico])
+      return render json: { error: 'システム・タグの名称は変更できません．' },
+                    status: :unprocessable_entity
+    end
+
+    if tag.nico? || category == 'nico'
+      return render json: { error: 'ニコタグは変更できません．' },
+                    status: :unprocessable_entity
+    end
+
+    alias_names = params[:aliases].to_s.split.uniq
+    parent_names = params[:parent_tags].to_s.split.uniq
+
+    ApplicationRecord.transaction do
+      TagVersioning.ensure_snapshot!(tag, created_by_user: current_user)
+
+      old_name = tag.name
+      name_changed = name != old_name
+      wiki_page = tag.tag_name.wiki_page if name_changed
+
+      tag.update!(category:)
+      tag.tag_name.update!(name:)
+
+      alias_names << old_name if name_changed
+      alias_names.delete(name)
+
+      update_aliases!(tag, alias_names)
+      update_parent_tags!(tag, parent_names)
+
+      tag.reload
+
+      record_tag_version!(
+          tag,
+          event_type: :update,
+          created_by_user: current_user,
+          name_changed:,
+          wiki_page:)
+    end
+
+    render json: TagRepr.base(tag.reload)
+  end
+
   def update
     return head :unauthorized unless current_user
     return head :forbidden unless current_user.gte_member?
@@ -218,20 +272,37 @@ class TagsController < ApplicationController
 
     tag = Tag.find(params[:id])
 
-    if name.present?
+    if tag.nico? || (category.present? && category == 'nico')
-      tag.tag_name.update!(name:)
+      return render json: { error: 'ニコタグは変更できません．' },
+                    status: :unprocessable_entity
     end
 
-    if category.present?
+    ApplicationRecord.transaction do
-      tag.update!(category:)
+      TagVersioning.ensure_snapshot!(tag, created_by_user: current_user)
+
+      old_name = tag.name
+      name_changed = name.present? && name != old_name
+      wiki_page = tag.tag_name.wiki_page if name_changed
+
+      tag.tag_name.update!(name:) if name.present?
+      tag.update!(category:) if category.present?
+
+      tag.reload
+
+      record_tag_version!(
+          tag,
+          event_type: :update,
+          created_by_user: current_user,
+          name_changed:,
+          wiki_page:)
     end
 
-    render json: TagRepr.base(tag)
+    render json: TagRepr.base(tag.reload)
   end
 
   private
 
-  def build_tag_children(tag)
+  def build_tag_children tag
     material = tag.materials.first
     file = nil
     content_type = nil
@@ -244,4 +315,80 @@ class TagsController < ApplicationController
         children: tag.children.sort_by { _1.name }.map { build_tag_children(_1) },
         material: material.as_json&.merge(file:, content_type:))
   end
+
+  def record_tag_version! tag, event_type:, created_by_user:, name_changed: false, wiki_page: nil
+    if tag.nico?
+      NicoTagVersionRecorder.record!(tag:, event_type:, created_by_user:)
+      return
+    end
+
+    TagVersionRecorder.record!(tag:, event_type:, created_by_user:)
+
+    return unless name_changed
+
+    wiki_page ||= tag.tag_name.wiki_page
+    return unless wiki_page&.wiki_versions&.exists?
+
+    WikiVersionRecorder.record!(
+        page: wiki_page,
+        event_type: :update,
+        created_by_user:)
+  end
+
+  def update_aliases! tag, alias_names
+    alias_names = alias_names.uniq
+
+    affected_tags = [tag]
+
+    current_aliases = tag.tag_name.aliases.to_a
+
+    current_aliases.each do |alias_tag_name|
+      next if alias_names.include?(alias_tag_name.name)
+
+      affected_tags << alias_tag_name.canonical&.tag
+    end
+
+    alias_names.each do |alias_name|
+      alias_tag_name = TagName.find_undiscard_or_create_by!(name: alias_name)
+      affected_tags << alias_tag_name.canonical&.tag
+    end
+
+    affected_tags.compact.uniq.each do |affected_tag|
+      TagVersioning.ensure_snapshot!(affected_tag, created_by_user: current_user)
+    end
+
+    current_aliases.each do |alias_tag_name|
+      next if alias_names.include?(alias_tag_name.name)
+
+      alias_tag_name.update!(canonical: nil)
+    end
+
+    alias_names.each do |alias_name|
+      alias_tag_name = TagName.find_undiscard_or_create_by!(name: alias_name)
+      alias_tag_name.update!(canonical: tag.tag_name)
+    end
+
+    affected_tags.compact.uniq.each do |affected_tag|
+      record_tag_version!(affected_tag, event_type: :update, created_by_user: current_user)
+    end
+  end
+
+  def update_parent_tags! tag, parent_names
+    parent_tags = Tag.normalise_tags(parent_names, with_tagme: false,
+                                                   with_no_deerjikist: false,
+                                                   deny_nico: true)
+
+    old_parent_tags = tag.parents.to_a
+
+    TagVersioning.record_tag_snapshots!((old_parent_tags + parent_tags).uniq,
+                                        created_by_user: current_user)
+
+    tag.reversed_tag_implications.destroy_all
+
+    parent_tags.each do |parent_tag|
+      next if parent_tag == tag
+
+      TagImplication.create!(tag:, parent_tag:)
+    end
+  end
 end

backend/app/controllers/users_controller.rb

@@ -1,18 +1,26 @@
 class UsersController < ApplicationController
   def create
-    user = User.create!(inheritance_code: SecureRandom.uuid, role: 'guest')
+    return head :unprocessable_entity if request.remote_ip.blank?
+
+    user = nil
+
+    User.transaction do
+      user = User.create!(inheritance_code: SecureRandom.uuid, role: :guest)
+      attach_ip_address!(user)
+    end
+
     render json: { code: user.inheritance_code,
-                   user: user.slice(:id, :name, :inheritance_code, :role) }
+                   user: user.slice(:id, :name, :inheritance_code, :role) },
+           status: :created
   end
 
   def verify
-    ip_bin = IPAddr.new(request.remote_ip).hton
-    ip_address = IpAddress.find_or_create_by!(ip_address: ip_bin)
-
     user = User.find_by(inheritance_code: params[:code])
     return render json: { valid: false } unless user
 
-    UserIp.find_or_create_by!(user:, ip_address:)
+    return head :unprocessable_entity if request.remote_ip.blank?
+
+    attach_ip_address!(user)
 
     render json: { valid: true, user: user.slice(:id, :name, :inheritance_code, :role) }
   end
@@ -41,9 +49,18 @@ class UsersController < ApplicationController
     return head :bad_request if name.blank?
 
     if user.update(name:)
-      render json: user.slice(:id, :name, :inheritance_code, :role), status: :created
+      render json: user.slice(:id, :name, :inheritance_code, :role), status: :ok
     else
       render json: user.errors, status: :unprocessable_entity
     end
   end
+
+  private
+
+  def attach_ip_address! user
+    ip_bin = IPAddr.new(request.remote_ip).hton
+    ip_address = IpAddress.create_or_find_by!(ip_address: ip_bin)
+
+    UserIp.create_or_find_by!(user:, ip_address:)
+  end
 end

backend/app/controllers/wiki_pages_controller.rb

@@ -85,22 +85,24 @@ class WikiPagesController < ApplicationController
     return head :unauthorized unless current_user
     return head :forbidden unless current_user.gte_member?
 
-    name = params[:title]&.strip
+    title = params[:title].to_s.strip
     body = params[:body].to_s
+    message = params[:message].presence
 
-    return head :unprocessable_entity if name.blank? || body.blank?
+    return head :unprocessable_entity if title.blank? || body.blank?
 
-    tag_name = TagName.find_undiscard_or_create_by!(name:)
+    tag_name = TagName.find_undiscard_or_create_by!(name: title)
-    page = WikiPage.new(tag_name:, created_user: current_user, updated_user: current_user)
-    if page.save
-      message = params[:message].presence
-      Wiki::Commit.content!(page:, body:, created_user: current_user, message:)
 
-      render json: WikiPageRepr.base(page), status: :created
+    page =
-    else
+        Wiki::Commit.create_content!(
-      render json: { errors: page.errors.full_messages },
+            tag_name:,
-             status: :unprocessable_entity
+            body:,
-    end
+            created_by_user: current_user,
+            message:)
+
+    render json: WikiPageRepr.base(page), status: :created
+  rescue ActiveRecord::RecordInvalid, ActiveRecord::RecordNotUnique
+    head :unprocessable_entity
   end
 
   def update
@@ -113,19 +115,34 @@ class WikiPagesController < ApplicationController
     return head :unprocessable_entity if title.blank? || body.blank?
 
     page = WikiPage.find(params[:id])
-    base_revision_id = page.current_revision.id
+    base_revision_id = params[:base_revision_id].presence
 
-    if params[:title].present? && params[:title].strip != page.title
+    ApplicationRecord.transaction do
-      return head :unprocessable_entity
+      page.lock!
+
+      old_title = page.title
+
+      tag = Tag.find_by(tag_name_id: page.tag_name_id)
+
+      if tag && title != old_title
+        TagVersioning.ensure_snapshot!(tag, created_by_user: current_user)
+      end
+
+      page.tag_name.update!(name: title) if title != old_title
+
+      message = params[:message].presence
+      Wiki::Commit.content!(page:,
+                            body:,
+                            created_user: current_user,
+                            message:,
+                            base_revision_id:)
+
+      if tag && title != old_title
+        tag.reload
+        TagVersionRecorder.record!(tag:, event_type: :update, created_by_user: current_user)
+      end
     end
 
-    message = params[:message].presence
-    Wiki::Commit.content!(page:,
-                          body:,
-                          created_user: current_user,
-                          message:,
-                          base_revision_id:)
-
     head :ok
   end
 

backend/app/models/ip_address.rb

@@ -2,5 +2,6 @@ class IpAddress < ApplicationRecord
   validates :ip_address, presence: true, length: { maximum: 16 }
   validates :banned, inclusion: { in: [true, false] }
 
-  has_many :users
+  has_many :user_ips, dependent: :destroy
+  has_many :users, through: :user_ips
 end

backend/app/models/my_discard.rb

@@ -1,7 +1,11 @@
 module MyDiscard
   extend ActiveSupport::Concern
 
-  included { include Discard::Model }
+  included do
+    include Discard::Model
+
+    default_scope -> { kept }
+  end
 
   class_methods do
     def find_undiscard_or_create_by! attrs, &block

backend/app/models/nico_tag_version.rb

@@ -0,0 +1,7 @@
+class NicoTagVersion < ApplicationRecord
+  include VersionRecord
+
+  belongs_to :tag
+
+  validates :name, presence: true
+end

backend/app/models/post_version.rb

@@ -1,29 +1,13 @@
 class PostVersion < ApplicationRecord
-  before_update do
+  include VersionRecord
-    raise ActiveRecord::ReadOnlyRecord, '版は更新できません．'
-  end
-
-  before_destroy do
-    raise ActiveRecord::ReadOnlyRecord, '版は削除できません．'
-  end
 
   belongs_to :post
   belongs_to :parent, class_name: 'Post', optional: true
-  belongs_to :created_by_user, class_name: 'User', optional: true
 
-  enum :event_type, { create: 'create',
-                      update: 'update',
-                      discard: 'discard',
-                      restore: 'restore' }, prefix: true, validate: true
-
-  validates :version_no, presence: true, numericality: { only_integer: true, greater_than: 0 }
-  validates :event_type, presence: true, inclusion: { in: event_types.keys }
   validates :url, presence: true
 
   validate :validate_original_created_range
 
-  scope :chronological, -> { order(:version_no, :id) }
-
   private
 
   def validate_original_created_range

backend/app/models/tag.rb

@@ -8,8 +8,6 @@ class Tag < ApplicationRecord
     ;
   end
 
-  default_scope -> { kept }
-
   has_many :post_tags, inverse_of: :tag
   has_many :active_post_tags, -> { kept }, class_name: 'PostTag', inverse_of: :tag
   has_many :post_tags_with_discarded, -> { with_discarded }, class_name: 'PostTag'
@@ -36,6 +34,9 @@ class Tag < ApplicationRecord
   has_many :deerjikists, dependent: :delete_all
   has_many :materials
 
+  has_many :tag_versions
+  has_many :nico_tag_versions
+
   belongs_to :tag_name
   delegate :wiki_page, to: :tag_name
 
@@ -78,25 +79,11 @@ class Tag < ApplicationRecord
 
   def material_id = materials.first&.id
 
-  def self.tagme
+  def self.tagme = find_or_create_by_tag_name!('タグ希望', category: :meta)
-    @tagme ||= find_or_create_by_tag_name!('タグ希望', category: :meta)
+  def self.bot = find_or_create_by_tag_name!('bot操作', category: :meta)
-  end
+  def self.no_deerjikist = find_or_create_by_tag_name!('ニジラー情報不詳', category: :meta)
-
+  def self.video = find_or_create_by_tag_name!('動画', category: :meta)
-  def self.bot
+  def self.niconico = find_or_create_by_tag_name!('ニコニコ', category: :meta)
-    @bot ||= find_or_create_by_tag_name!('bot操作', category: :meta)
-  end
-
-  def self.no_deerjikist
-    @no_deerjikist ||= find_or_create_by_tag_name!('ニジラー情報不詳', category: :meta)
-  end
-
-  def self.video
-    @video ||= find_or_create_by_tag_name!('動画', category: :meta)
-  end
-
-  def self.niconico
-    @niconico ||= find_or_create_by_tag_name!('ニコニコ', category: :meta)
-  end
 
   def self.normalise_tags tag_names, with_tagme: true,
                                      with_no_deerjikist: true,
@@ -152,21 +139,25 @@ class Tag < ApplicationRecord
     retry
   end
 
-  def self.merge_tags! target_tag, source_tags
+  def self.merge_tags! target_tag, source_tags, created_by_user: nil
     target_tag => Tag
 
     affected_post_ids = Set.new
 
     Tag.transaction do
+      TagVersioning.ensure_snapshot!(target_tag, created_by_user:)
+
       Array(source_tags).compact.uniq.each do |source_tag|
         source_tag => Tag
 
         next if source_tag == target_tag
 
+        TagVersioning.ensure_snapshot!(source_tag, created_by_user:)
+
         source_tag.post_tags.kept.find_each do |source_pt|
           post_id = source_pt.post_id
           affected_post_ids << post_id
-          source_pt.discard_by!(nil)
+          source_pt.discard_by!(created_by_user)
           unless PostTag.kept.exists?(post_id:, tag: target_tag)
             PostTag.create!(post_id:, tag: target_tag)
           end
@@ -178,6 +169,7 @@ class Tag < ApplicationRecord
           raise ActiveRecord::RecordInvalid.new(source_tag_name)
         end
 
+        TagVersioning.record!(source_tag, event_type: :discard, created_by_user:)
         source_tag.discard!
 
         if source_tag.nico?
@@ -186,10 +178,13 @@ class Tag < ApplicationRecord
           source_tag_name.update_columns(canonical_id: target_tag.tag_name_id,
                                          updated_at: Time.current)
         end
+
+        TagVersioning.record!(target_tag, event_type: :update, created_by_user:)
       end
 
       Post.where(id: affected_post_ids.to_a).find_each do |post|
-        PostVersionRecorder.record!(post:, event_type: :update, created_by_user: nil)
+        PostVersionRecorder.ensure_snapshot!(post, created_by_user:)
+        PostVersionRecorder.record!(post:, event_type: :update, created_by_user:)
       end
 
       # 投稿件数を再集計
@@ -199,6 +194,14 @@ class Tag < ApplicationRecord
     target_tag.reload
   end
 
+  def snapshot_aliases = tag_name.aliases.kept.order(:name).pluck(:name)
+
+  def snapshot_parent_tag_ids = parents.order(:id).pluck(:id)
+
+  def snapshot_linked_tag_names
+    linked_tags.joins(:tag_name).order('tag_names.name').pluck('tag_names.name')
+  end
+
   private
 
   def nico_tag_name_must_start_with_nico

backend/app/models/tag_name.rb

@@ -1,8 +1,6 @@
 class TagName < ApplicationRecord
   include MyDiscard
 
-  default_scope -> { kept }
-
   has_one :tag
   has_one :wiki_page
 

backend/app/models/tag_version.rb

@@ -0,0 +1,15 @@
+class TagVersion < ApplicationRecord
+  include VersionRecord
+
+  belongs_to :tag
+
+  enum :category, { deerjikist: 'deerjikist',
+                    meme: 'meme',
+                    character: 'character',
+                    general: 'general',
+                    material: 'material',
+                    meta: 'meta' }, validate: true
+
+  validates :name, presence: true
+  validates :category, presence: true
+end

backend/app/models/version_record.rb

@@ -0,0 +1,19 @@
+module VersionRecord
+  extend ActiveSupport::Concern
+
+  def readonly? = persisted?
+
+  included do
+    belongs_to :created_by_user, class_name: 'User', optional: true
+
+    enum :event_type, { create: 'create',
+                        update: 'update',
+                        discard: 'discard',
+                        restore: 'restore' }, prefix: true, validate: true
+
+    validates :version_no, presence: true, numericality: { only_integer: true, greater_than: 0 }
+    validates :event_type, presence: true
+
+    scope :chronological, -> { order(:version_no, :id) }
+  end
+end

backend/app/models/wiki_page.rb

@@ -4,8 +4,6 @@ require 'set'
 class WikiPage < ApplicationRecord
   include MyDiscard
 
-  default_scope -> { kept }
-
   has_many :wiki_revisions, dependent: :destroy
   belongs_to :created_user, class_name: 'User'
   belongs_to :updated_user, class_name: 'User'
@@ -15,8 +13,11 @@ class WikiPage < ApplicationRecord
            foreign_key: :redirect_page_id,
            dependent: :nullify
 
+  has_many :wiki_versions
+
   belongs_to :tag_name
   validates :tag_name, presence: true
+  validates :body, presence: true
 
   def title = tag_name.name
 
@@ -26,11 +27,6 @@ class WikiPage < ApplicationRecord
 
   def current_revision = wiki_revisions.order(id: :desc).first
 
-  def body
-    rev = current_revision
-    rev.body if rev&.content?
-  end
-
   def resolve_redirect limit: 10
     page = self
     visited = Set.new

backend/app/models/wiki_version.rb

@@ -0,0 +1,8 @@
+class WikiVersion < ApplicationRecord
+  include VersionRecord
+
+  belongs_to :wiki_page
+
+  validates :title, presence: true
+  validates :body, presence: true
+end

backend/app/representations/tag_repr.rb

@@ -8,10 +8,9 @@ module TagRepr
   module_function
 
   def base tag
-    tag.as_json(BASE)
+    tag.as_json(BASE).merge(aliases: tag.snapshot_aliases,
+                            parents: tag.parents.map { _1.as_json(BASE) })
   end
 
-  def many tags
+  def many(tags) = tags.map { |t| base(t) }
-    tags.map { |t| base(t) }
-  end
 end

backend/app/services/nico_tag_version_recorder.rb

@@ -0,0 +1,19 @@
+class NicoTagVersionRecorder < VersionRecorder
+  def self.record! tag:, event_type:, created_by_user:
+    new(tag:, event_type:, created_by_user:).record!
+  end
+
+  def initialize tag:, event_type:, created_by_user:
+    super(record: tag, event_type:, created_by_user:)
+  end
+
+  private
+
+  def version_class = NicoTagVersion
+  def version_association = :nico_tag_versions
+  def record_key = :tag
+
+  def snapshot_attributes
+    { name: @record.name, linked_tags: @record.snapshot_linked_tag_names.join(' ') }
+  end
+end

backend/app/services/post_version_recorder.rb

@@ -1,57 +1,31 @@
-class PostVersionRecorder
+class PostVersionRecorder < VersionRecorder
   def self.record! post:, event_type:, created_by_user:
     new(post:, event_type:, created_by_user:).record!
   end
 
   def initialize post:, event_type:, created_by_user:
-    @post = post
+    super(record: post, event_type:, created_by_user:)
-    @event_type = event_type
-    @created_by_user = created_by_user
   end
 
-  def record!
+  def self.ensure_snapshot! post, created_by_user:
-    @post.with_lock do
+    return if post.post_versions.exists?
-      latest = @post.post_versions.order(version_no: :desc).first
-      attrs = snapshot_attributes
 
-      return latest if @event_type == :update && latest && same_snapshot?(latest, attrs)
+    record!(post:, event_type: :create, created_by_user:)
-
-      PostVersion.create!(
-          post: @post,
-          version_no: (latest&.version_no || 0) + 1,
-          event_type: @event_type,
-          title: attrs[:title],
-          url: attrs[:url],
-          thumbnail_base: attrs[:thumbnail_base],
-          tags: attrs[:tags],
-          parent: attrs[:parent],
-          original_created_from: attrs[:original_created_from],
-          original_created_before: attrs[:original_created_before],
-          created_at: Time.current,
-          created_by_user: @created_by_user)
-    end
   end
 
   private
 
-  def snapshot_attributes
+  def version_class = PostVersion
-    { title: @post.title,
+  def version_association = :post_versions
-      url: @post.url,
+  def record_key = :post
-      thumbnail_base: @post.thumbnail_base,
-      tags: @post.snapshot_tag_names.join(' '),
-      parent: @post.parent,
-      original_created_from: @post.original_created_from,
-      original_created_before: @post.original_created_before }
-  end
 
-  def same_snapshot? version, attrs
+  def snapshot_attributes
-    true &&
+    { title: @record.title,
-        version.title == attrs[:title] &&
+      url: @record.url,
-        version.url == attrs[:url] &&
+      thumbnail_base: @record.thumbnail_base,
-        version.thumbnail_base == attrs[:thumbnail_base] &&
+      tags: @record.snapshot_tag_names.join(' '),
-        version.tags == attrs[:tags] &&
+      parent_id: @record.parent_id,
-        version.parent_id == attrs[:parent]&.id &&
+      original_created_from: @record.original_created_from,
-        version.original_created_from == attrs[:original_created_from] &&
+      original_created_before: @record.original_created_before }
-        version.original_created_before == attrs[:original_created_before]
   end
 end

backend/app/services/tag_version_recorder.rb

@@ -0,0 +1,22 @@
+class TagVersionRecorder < VersionRecorder
+  def self.record! tag:, event_type:, created_by_user:
+    new(tag:, event_type:, created_by_user:).record!
+  end
+
+  def initialize tag:, event_type:, created_by_user:
+    super(record: tag, event_type:, created_by_user:)
+  end
+
+  private
+
+  def version_class = TagVersion
+  def version_association = :tag_versions
+  def record_key = :tag
+
+  def snapshot_attributes
+    { name: @record.name,
+      category: @record.category,
+      aliases: @record.snapshot_aliases.join(' '),
+      parent_tag_ids: @record.snapshot_parent_tag_ids.join(' ') }
+  end
+end

backend/app/services/tag_versioning.rb

@@ -0,0 +1,38 @@
+class TagVersioning
+  def self.record! tag, event_type:, created_by_user:
+    if tag.nico?
+      NicoTagVersionRecorder.record!(tag:, event_type:, created_by_user:)
+    else
+      TagVersionRecorder.record!(tag:, event_type:, created_by_user:)
+    end
+  end
+
+  def self.ensure_snapshot! tag, created_by_user:
+    if tag.nico?
+      return if tag.nico_tag_versions.exists?
+
+      NicoTagVersionRecorder.record!(tag:, event_type: :create, created_by_user:)
+    else
+      return if tag.tag_versions.exists?
+
+      TagVersionRecorder.record!(tag:, event_type: :create, created_by_user:)
+    end
+  end
+
+  def self.record_tag_snapshot! tag, created_by_user:
+    event_type =
+        if tag.nico?
+          tag.nico_tag_versions.exists? ? :update : :create
+        else
+          tag.tag_versions.exists? ? :update : :create
+        end
+
+    record!(tag, event_type:, created_by_user:)
+  end
+
+  def self.record_tag_snapshots! tags, created_by_user:
+    tags.each do |tag|
+      record_tag_snapshot!(tag, created_by_user:)
+    end
+  end
+end

backend/app/services/version_recorder.rb

@@ -0,0 +1,62 @@
+class VersionRecorder
+  EVENT_TYPES = ['create', 'update', 'discard', 'restore'].freeze
+
+  def initialize record:, event_type:, created_by_user:
+    @record = record
+    @event_type = event_type.to_s
+    @created_by_user = created_by_user
+
+    validate_event_type!
+  end
+
+  def record!
+    raise "#{ record_class.name } must be persisted" unless @record.persisted?
+
+    ApplicationRecord.transaction do
+      @record = record_class.unscoped.lock.find(@record.id)
+      latest = latest_version
+
+      if !(latest) && @event_type != 'create'
+        raise "#{ version_class.name } first event must be create"
+      end
+
+      if @event_type == 'create' && latest
+        raise "#{ version_class.name } create event already exists"
+      end
+
+      attrs = snapshot_attributes
+
+      return latest if @event_type == 'update' && latest && same_snapshot?(latest, attrs)
+
+      version_class.create!(base_attributes(latest).merge(record_key => @record).merge(attrs))
+    end
+  end
+
+  private
+
+  def latest_version = versions.order(version_no: :desc).first
+
+  def versions = @record.public_send(version_association)
+
+  def base_attributes latest
+    { version_no: (latest&.version_no || 0) + 1,
+      event_type: @event_type,
+      created_at: Time.current,
+      created_by_user: @created_by_user }
+  end
+
+  def same_snapshot?(version, attrs) = attrs.all? { |k, v| version.public_send(k) == v }
+
+  def validate_event_type!
+    return if EVENT_TYPES.include?(@event_type)
+
+    raise ArgumentError, "Invalid event_type: #{ @event_type }"
+  end
+
+  def version_class = raise NotImplementedError
+  def version_association = raise NotImplementedError
+  def record_key = raise NotImplementedError
+  def snapshot_attributes = raise NotImplementedError
+
+  def record_class = @record.class
+end

backend/app/services/wiki/commit.rb

@@ -7,6 +7,31 @@ module Wiki
       ;
     end
 
+    def self.create_content! tag_name:, body:, created_by_user:, message: nil
+      normalised = normalise_body(body)
+
+      page = WikiPage.new(tag_name:,
+                          body: normalised,
+                          created_user: created_by_user,
+                          updated_user: created_by_user)
+
+      if normalised.blank?
+        page.errors.add(:body, :blank)
+        raise ActiveRecord::RecordInvalid, page
+      end
+
+      ActiveRecord::Base.transaction do
+        page.save!
+
+        new(page:, created_user: created_by_user).content!(
+            body: normalised,
+            message:,
+            base_revision_id: nil)
+
+        page
+      end
+    end
+
     def self.content! page:, body:, created_user:, message: nil, base_revision_id: nil
       new(page:, created_user:).content!(body:, message:, base_revision_id:)
     end
@@ -21,7 +46,12 @@ module Wiki
     end
 
     def content! body:, message:, base_revision_id:
-      normalised = normalise_body(body)
+      normalised = self.class.normalise_body(body)
+      if normalised.blank?
+        @page.errors.add(:body, :blank)
+        raise ActiveRecord::RecordInvalid, @page
+      end
+
       lines = split_lines(normalised)
 
       line_shas = lines.map { |line| Digest::SHA256.hexdigest(line) }
@@ -37,10 +67,19 @@ module Wiki
           current_id = @page.wiki_revisions.maximum(:id)
           if current_id && current_id != base_revision_id.to_i
             raise Conflict,
-                "競合が発生してゐます（現在の Id.：#{ current_id }，ベース Id.：#{ base_revision_id }）．"
+                "競合が発生してゐます" +
+                "（現在の Id.：#{ current_id }，ベース Id.：#{ base_revision_id }）．"
           end
         end
 
+        @page.update!(body: normalised)
+
+        WikiVersionRecorder.record!(
+            page: @page,
+            event_type: @page.wiki_versions.exists? ? :update : :create,
+            reason: message,
+            created_by_user: @created_user)
+
         rev = WikiRevision.create!(
             wiki_page:        @page,
             base_revision_id:,
@@ -54,65 +93,45 @@ module Wiki
         rows = line_ids.each_with_index.map do |line_id, pos|
           { wiki_revision_id: rev.id, wiki_line_id: line_id, position: pos }
         end
-        WikiRevisionLine.insert_all!(rows)
+        WikiRevisionLine.insert_all!(rows) if rows.any?
 
         rev
       end
     end
 
-    def redirect! redirect_page:, message:, base_revision_id:
+    def redirect!(redirect_page:, message:, base_revision_id:) = raise '廃止しました．'
-      ActiveRecord::Base.transaction do
-        @page.lock!
 
-        if base_revision_id.present?
+    def self.normalise_body body
-          current_id = @page.wiki_revisions.maximum(:id)
+      s = body.to_s
-          if current_id && current_id != base_revision_id.to_i
+      s.gsub!(/\r\n?/, "\n")
-            raise Conflict,
+      s.encode('UTF-8', invalid: :replace, undef: :replace, replace: '🖕')
-                "競合が発生してゐます（現在の Id.：#{ current_id }，ベース Id.：#{ base_revision_id }）．"
+      s.gsub(/\n+$/, '')
-          end
-        end
-
-        WikiRevision.create!(
-            wiki_page:        @page,
-            base_revision_id:,
-            created_user:     @created_user,
-            kind:             :redirect,
-            redirect_page:,
-            message:,
-            lines_count:      0,
-            tree_sha256:      nil)
-      end
     end
 
     private
 
-    def normalise_body body
+    def split_lines(body) = body.split("\n")
-      s = body.to_s
-      s.gsub!("\r\n", "\n")
-      s.encode('UTF-8', invalid: :replace, undef: :replace, replace: '🖕')
-    end
-
-    def split_lines body
-      body.split("\n")
-    end
 
     def upsert_lines! lines, line_shas
       now = Time.current
 
       id_by_sha = WikiLine.where(sha256: line_shas).pluck(:sha256, :id).to_h
 
-      missing_rows = []
+      missing_by_sha = { }
+
       line_shas.each_with_index do |sha, i|
         next if id_by_sha.key?(sha)
+        next if missing_by_sha.key?(sha)
 
-        missing_rows << { sha256:     sha,
+        missing_by_sha[sha] = {
-                          body:       lines[i],
+            sha256:     sha,
-                          created_at: now,
+            body:       lines[i],
-                          updated_at: now }
+            created_at: now,
+            updated_at: now }
       end
 
-      if missing_rows.any?
+      if missing_by_sha.any?
-        WikiLine.upsert_all(missing_rows)
+        WikiLine.upsert_all(missing_by_sha.values)
         id_by_sha = WikiLine.where(sha256: line_shas).pluck(:sha256, :id).to_h
       end
 

backend/app/services/wiki_version_recorder.rb

@@ -0,0 +1,21 @@
+class WikiVersionRecorder < VersionRecorder
+  def self.record! page:, event_type:, reason: nil, created_by_user:
+    new(page:, event_type:, reason:, created_by_user:).record!
+  end
+
+  def initialize page:, event_type:, reason: nil, created_by_user:
+    @reason = reason
+    super(record: page, event_type:, created_by_user:)
+  end
+
+  private
+
+  def version_class = WikiVersion
+  def version_association = :wiki_versions
+  def record_key = :wiki_page
+
+  def snapshot_attributes = {
+      title: @record.title,
+      body: @record.body,
+      reason: @reason }
+end

backend/config/routes.rb

@@ -6,10 +6,11 @@ Rails.application.routes.draw do
     delete ':child_id', action: :destroy
   end
 
-  resources :tags, only: [:index, :show, :update] do
+  resources :tags, only: [:index, :show] do
     collection do
       get :autocomplete
       get :'with-depth', action: :with_depth
+      get :versions, to: 'tag_versions#index'
 
       scope :name do
         get ':name/deerjikists', action: :deerjikists_by_name
@@ -19,6 +20,9 @@ Rails.application.routes.draw do
     end
 
     member do
+      put '', action: :update_all
+      patch '', action: :update
+
       get :deerjikists
     end
   end

backend/config/schedule.rb

@@ -1,12 +1,19 @@
 env :PATH, '/root/.rbenv/shims:/root/.rbenv/bin:/usr/local/bin:/usr/bin:/bin'
 
+set :path, '/var/www/btrc-hub/backend'
+set :environment, 'production'
 set :output, standard: '/var/log/btrc_hub_nico_sync.log',
              error:    '/var/log/btrc_hub_nico_sync_err.log'
 
-every 1.day, at: '3:00 pm' do
+job_type :rake,
+         'cd :path && set -a && . /etc/btrc-hub/backend.env && set +a && ' \
+         ':environment_variable=:environment bundle exec rake :task --silent :output'
+
+every 1.day, at: '11:00 am' do
   rake 'nico:sync', environment: 'production'
 end
 
 every 1.day, at: '0:00 am' do
   rake 'post_similarity:calc', environment: 'production'
+  rake 'tag_similarity:calc', environment: 'production'
 end

backend/db/migrate/20260409123700_create_post_versions.rb

@@ -2,15 +2,15 @@ require 'set'
 
 
 class CreatePostVersions < ActiveRecord::Migration[8.0]
-  class Post < ApplicationRecord
+  class Post < ActiveRecord::Base
     self.table_name = 'posts'
   end
 
-  class PostTag < ApplicationRecord
+  class PostTag < ActiveRecord::Base
     self.table_name = 'post_tags'
   end
 
-  class PostVersion < ApplicationRecord
+  class PostVersion < ActiveRecord::Base
     self.table_name = 'post_versions'
   end
 

backend/db/migrate/20260419035400_create_tag_versions.rb

@@ -0,0 +1,156 @@
+class CreateTagVersions < ActiveRecord::Migration[8.0]
+  class Tag < ActiveRecord::Base
+    self.table_name = 'tags'
+  end
+
+  class TagName < ActiveRecord::Base
+    self.table_name = 'tag_names'
+  end
+
+  class TagImplication < ActiveRecord::Base
+    self.table_name = 'tag_implications'
+  end
+
+  class TagVersion < ActiveRecord::Base
+    self.table_name = 'tag_versions'
+  end
+
+  class NicoTagVersion < ActiveRecord::Base
+    self.table_name = 'nico_tag_versions'
+  end
+
+  class NicoTagRelation < ActiveRecord::Base
+    self.table_name = 'nico_tag_relations'
+  end
+
+  def up
+    create_table :tag_versions do |t|
+      t.references :tag, null: false, foreign_key: true, index: false
+      t.integer :version_no, null: false
+      t.string :event_type, null: false
+      t.string :name, null: false
+      t.string :category, null: false
+      t.text :aliases, null: false
+      t.text :parent_tag_ids, null: false
+      t.datetime :created_at, null: false
+      t.references :created_by_user, foreign_key: { to_table: :users }, index: false
+
+      t.index [:tag_id, :version_no], unique: true
+      t.index :created_at
+      t.index [:tag_id, :created_at], order: { created_at: :desc }
+      t.index [:created_by_user_id, :created_at], order: { created_at: :desc }
+      t.check_constraint 'version_no > 0',
+                         name: 'tag_versions_version_no_positive'
+    end
+
+    create_table :nico_tag_versions do |t|
+      t.references :tag, null: false, foreign_key: true, index: false
+      t.integer :version_no, null: false
+      t.string :event_type, null: false
+      t.string :name, null: false
+      t.text :linked_tags, null: false
+      t.datetime :created_at, null: false
+      t.references :created_by_user, foreign_key: { to_table: :users }, index: false
+
+      t.index [:tag_id, :version_no], unique: true
+      t.index :created_at
+      t.index [:tag_id, :created_at], order: { created_at: :desc }
+      t.index [:created_by_user_id, :created_at], order: { created_at: :desc }
+      t.check_constraint 'version_no > 0',
+                         name: 'nico_tag_versions_version_no_positive'
+    end
+
+    TagVersion.reset_column_information
+    say_with_time 'Backfilling tag_versions' do
+      Tag.where(discarded_at: nil)
+         .where.not(category: 'nico')
+         .find_in_batches(batch_size: 500) do |tags|
+        tag_ids = tags.map(&:id)
+
+        tag_implication_rows_by_tag_id =
+            TagImplication
+            .where(tag_id: tag_ids)
+            .pluck(:tag_id, :parent_tag_id)
+            .each_with_object(Hash.new { |h, k| h[k] = [] }) do |row, h|
+              h[row[0]] << row[1]
+            end
+
+        tag_name_rows_by_tag_id =
+            TagName
+            .joins('INNER JOIN tags ON tags.tag_name_id = tag_names.id')
+            .where(tags: { id: tag_ids })
+            .pluck('tags.id', 'tag_names.name')
+            .each_with_object({ }) do |row, h|
+              h[row[0]] = row[1]
+            end
+
+        tag_alias_rows_by_tag_id =
+            TagName
+            .joins('INNER JOIN tags ON tags.tag_name_id = tag_names.canonical_id')
+            .where(tags: { id: tag_ids })
+            .where(tag_names: { discarded_at: nil })
+            .pluck('tags.id', 'tag_names.name')
+            .each_with_object(Hash.new { |h, k| h[k] = [] }) do |row, h|
+              h[row[0]] << row[1]
+            end
+
+        TagVersion.insert_all(tags.map { |tag|
+          { tag_id: tag.id,
+            version_no: 1,
+            event_type: 'create',
+            name: tag_name_rows_by_tag_id[tag.id],
+            category: tag.category,
+            aliases: tag_alias_rows_by_tag_id[tag.id].sort.join(' '),
+            parent_tag_ids: tag_implication_rows_by_tag_id[tag.id].sort.join(' '),
+            created_at: tag.created_at,
+            created_by_user_id: nil }
+        })
+      end
+    end
+
+    NicoTagVersion.reset_column_information
+    say_with_time 'Backfilling nico_tag_versions' do
+      Tag.where(discarded_at: nil, category: 'nico')
+         .find_in_batches(batch_size: 500) do |tags|
+        tag_ids = tags.map(&:id)
+
+        tag_name_rows_by_tag_id =
+            TagName
+            .joins('INNER JOIN tags ON tags.tag_name_id = tag_names.id')
+            .where(tags: { id: tag_ids })
+            .pluck('tags.id', 'tag_names.name')
+            .each_with_object({ }) do |row, h|
+              h[row[0]] = row[1]
+            end
+
+        nico_tag_relation_rows_by_tag_id =
+            NicoTagRelation
+            .joins('INNER JOIN tags nico_tags ON nico_tags.id = nico_tag_relations.nico_tag_id')
+            .joins('INNER JOIN tags linked_tags ON linked_tags.id = nico_tag_relations.tag_id')
+            .joins('INNER JOIN tag_names ON tag_names.id = linked_tags.tag_name_id')
+            .where(nico_tags: { id: tag_ids })
+            .where(linked_tags: { discarded_at: nil })
+            .where(tag_names: { discarded_at: nil })
+            .pluck('nico_tags.id', 'tag_names.name')
+            .each_with_object(Hash.new { |h, k| h[k] = [] }) do |row, h|
+              h[row[0]] << row[1]
+            end
+
+        NicoTagVersion.insert_all(tags.map { |tag|
+          { tag_id: tag.id,
+            version_no: 1,
+            event_type: 'create',
+            name: tag_name_rows_by_tag_id[tag.id],
+            linked_tags: nico_tag_relation_rows_by_tag_id[tag.id].sort.join(' '),
+            created_at: tag.created_at,
+            created_by_user_id: nil }
+        })
+      end
+    end
+  end
+
+  def down
+    drop_table :nico_tag_versions
+    drop_table :tag_versions
+  end
+end

backend/db/migrate/20260426120600_create_wiki_versions.rb

@@ -0,0 +1,91 @@
+class CreateWikiVersions < ActiveRecord::Migration[8.0]
+  class WikiPage < ActiveRecord::Base
+    self.table_name = 'wiki_pages'
+  end
+
+  class WikiRevision < ActiveRecord::Base
+    self.table_name = 'wiki_revisions'
+  end
+
+  class WikiRevisionLine < ActiveRecord::Base
+    self.table_name = 'wiki_revision_lines'
+  end
+
+  class WikiLine < ActiveRecord::Base
+    self.table_name = 'wiki_lines'
+  end
+
+  class WikiVersion < ActiveRecord::Base
+    self.table_name = 'wiki_versions'
+  end
+
+  class TagName < ActiveRecord::Base
+    self.table_name = 'tag_names'
+  end
+
+  def up
+    add_column :wiki_pages, :body, :text, after: :tag_name_id
+
+    create_table :wiki_versions do |t|
+      t.references :wiki_page, null: false, foreign_key: true
+      t.integer :version_no, null: false
+      t.string :event_type, null: false
+      t.string :title, null: false
+      t.text :body, null: false
+      t.text :reason
+      t.datetime :created_at, null: false
+      t.references :created_by_user, foreign_key: { to_table: :users }
+
+      t.index [:wiki_page_id, :version_no], unique: true
+      t.check_constraint 'version_no > 0',
+                         name: 'wiki_versions_version_no_positive'
+      t.check_constraint "event_type IN ('create', 'update', 'discard', 'restore')",
+                         name: 'wiki_versions_event_type_valid'
+    end
+
+    WikiPage.reset_column_information
+    WikiVersion.reset_column_information
+
+    say_with_time 'Backfilling wiki_versions' do
+      WikiPage.find_each do |page|
+        base_revision_id = nil
+        version_no = 1
+        title = TagName.find(page.tag_name_id).name
+        body = nil
+        loop do
+          rev = WikiRevision.where(wiki_page_id: page.id).find_by(base_revision_id:)
+          break unless rev
+
+          body = WikiRevisionLine.where(wiki_revision_id: rev.id).order(:position).map { |wrl|
+            WikiLine.find(wrl.wiki_line_id).body
+          }.join("\n")
+
+          WikiVersion.create!(
+              wiki_page_id: page.id,
+              version_no:,
+              event_type: version_no == 1 ? 'create' : 'update',
+              title:,
+              body:,
+              reason: rev.message,
+              created_at: rev.created_at,
+              created_by_user_id: rev.created_user_id)
+
+          version_no += 1
+          base_revision_id = rev.id
+        end
+        if body
+          page.update!(body:)
+        else
+          page.destroy!
+        end
+      end
+    end
+
+    change_column_null :wiki_pages, :body, false
+  end
+
+  def down
+    drop_table :wiki_versions
+    remove_column :wiki_pages, :body
+  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_04_09_123700) do
+ActiveRecord::Schema[8.0].define(version: 2026_04_26_120600) 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
@@ -104,6 +104,21 @@ ActiveRecord::Schema[8.0].define(version: 2026_04_09_123700) do
     t.index ["tag_id"], name: "index_nico_tag_relations_on_tag_id"
   end
 
+  create_table "nico_tag_versions", charset: "utf8mb4", collation: "utf8mb4_0900_ai_ci", force: :cascade do |t|
+    t.bigint "tag_id", null: false
+    t.integer "version_no", null: false
+    t.string "event_type", null: false
+    t.string "name", null: false
+    t.text "linked_tags", null: false
+    t.datetime "created_at", null: false
+    t.bigint "created_by_user_id"
+    t.index ["created_at"], name: "index_nico_tag_versions_on_created_at"
+    t.index ["created_by_user_id", "created_at"], name: "index_nico_tag_versions_on_created_by_user_id_and_created_at", order: { created_at: :desc }
+    t.index ["tag_id", "created_at"], name: "index_nico_tag_versions_on_tag_id_and_created_at", order: { created_at: :desc }
+    t.index ["tag_id", "version_no"], name: "index_nico_tag_versions_on_tag_id_and_version_no", unique: true
+    t.check_constraint "`version_no` > 0", name: "nico_tag_versions_version_no_positive"
+  end
+
   create_table "post_similarities", primary_key: ["post_id", "target_post_id"], charset: "utf8mb4", collation: "utf8mb4_0900_ai_ci", force: :cascade do |t|
     t.bigint "post_id", null: false
     t.bigint "target_post_id", null: false
@@ -216,6 +231,23 @@ ActiveRecord::Schema[8.0].define(version: 2026_04_09_123700) do
     t.index ["target_tag_id"], name: "index_tag_similarities_on_target_tag_id"
   end
 
+  create_table "tag_versions", charset: "utf8mb4", collation: "utf8mb4_0900_ai_ci", force: :cascade do |t|
+    t.bigint "tag_id", null: false
+    t.integer "version_no", null: false
+    t.string "event_type", null: false
+    t.string "name", null: false
+    t.string "category", null: false
+    t.text "aliases", null: false
+    t.text "parent_tag_ids", null: false
+    t.datetime "created_at", null: false
+    t.bigint "created_by_user_id"
+    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 ["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"
+  end
+
   create_table "tags", charset: "utf8mb4", collation: "utf8mb4_0900_ai_ci", force: :cascade do |t|
     t.bigint "tag_name_id", null: false
     t.string "category", default: "general", null: false
@@ -322,6 +354,7 @@ ActiveRecord::Schema[8.0].define(version: 2026_04_09_123700) do
 
   create_table "wiki_pages", charset: "utf8mb4", collation: "utf8mb4_0900_ai_ci", force: :cascade do |t|
     t.bigint "tag_name_id", null: false
+    t.text "body", null: false
     t.bigint "created_user_id", null: false
     t.bigint "updated_user_id", null: false
     t.datetime "created_at", null: false
@@ -364,6 +397,22 @@ ActiveRecord::Schema[8.0].define(version: 2026_04_09_123700) do
     t.index ["wiki_page_id"], name: "index_wiki_revisions_on_wiki_page_id"
   end
 
+  create_table "wiki_versions", charset: "utf8mb4", collation: "utf8mb4_0900_ai_ci", force: :cascade do |t|
+    t.bigint "wiki_page_id", null: false
+    t.integer "version_no", null: false
+    t.string "event_type", null: false
+    t.string "title", null: false
+    t.text "body", null: false
+    t.text "reason"
+    t.datetime "created_at", null: false
+    t.bigint "created_by_user_id"
+    t.index ["created_by_user_id"], name: "index_wiki_versions_on_created_by_user_id"
+    t.index ["wiki_page_id", "version_no"], name: "index_wiki_versions_on_wiki_page_id_and_version_no", unique: true
+    t.index ["wiki_page_id"], name: "index_wiki_versions_on_wiki_page_id"
+    t.check_constraint "`event_type` in (_utf8mb4'create',_utf8mb4'update',_utf8mb4'discard',_utf8mb4'restore')", name: "wiki_versions_event_type_valid"
+    t.check_constraint "`version_no` > 0", name: "wiki_versions_version_no_positive"
+  end
+
   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 "material_versions", "materials"
@@ -377,6 +426,8 @@ ActiveRecord::Schema[8.0].define(version: 2026_04_09_123700) do
   add_foreign_key "materials", "users", column: "updated_by_user_id"
   add_foreign_key "nico_tag_relations", "tags"
   add_foreign_key "nico_tag_relations", "tags", column: "nico_tag_id"
+  add_foreign_key "nico_tag_versions", "tags"
+  add_foreign_key "nico_tag_versions", "users", column: "created_by_user_id"
   add_foreign_key "post_similarities", "posts"
   add_foreign_key "post_similarities", "posts", column: "target_post_id"
   add_foreign_key "post_tags", "posts"
@@ -394,6 +445,8 @@ ActiveRecord::Schema[8.0].define(version: 2026_04_09_123700) do
   add_foreign_key "tag_names", "tag_names", column: "canonical_id"
   add_foreign_key "tag_similarities", "tags"
   add_foreign_key "tag_similarities", "tags", column: "target_tag_id"
+  add_foreign_key "tag_versions", "tags"
+  add_foreign_key "tag_versions", "users", column: "created_by_user_id"
   add_foreign_key "tags", "tag_names"
   add_foreign_key "theatre_comments", "theatres"
   add_foreign_key "theatre_comments", "users"
@@ -417,4 +470,6 @@ ActiveRecord::Schema[8.0].define(version: 2026_04_09_123700) do
   add_foreign_key "wiki_revisions", "wiki_pages"
   add_foreign_key "wiki_revisions", "wiki_pages", column: "redirect_page_id"
   add_foreign_key "wiki_revisions", "wiki_revisions", column: "base_revision_id"
+  add_foreign_key "wiki_versions", "users", column: "created_by_user_id"
+  add_foreign_key "wiki_versions", "wiki_pages"
 end

backend/lib/tasks/export_nico.rake

@@ -0,0 +1,23 @@
+namespace :nico do
+  desc 'ニコニコ DB 逆連携'
+  task export: :environment do
+    require 'open3'
+
+    mysql_user = ENV.fetch('MYSQL_USER')
+    mysql_pass = ENV.fetch('MYSQL_PASS')
+    nizika_nico_path = ENV.fetch('NIZIKA_NICO_PATH')
+
+    videos = Post.where('url LIKE ?', '%nicovideo.jp/watch/%').pluck(:url).filter_map {
+      _1[%r{nicovideo\.jp/watch/([^/?#]+)}, 1]
+    }.uniq
+
+    next if videos.empty?
+
+    _, stderr, status = Open3.capture3(
+        { 'MYSQL_USER' => mysql_user, 'MYSQL_PASS' => mysql_pass },
+        'python3', '-m', 'tracked_videos.put_bulk_upsert', *videos,
+        chdir: nizika_nico_path)
+
+    raise stderr unless status.success?
+  end
+end

backend/lib/tasks/sync_nico.rake

@@ -115,6 +115,10 @@ namespace :nico do
       datum['tags'].each do |raw|
         name = TagNameSanitisationRule.sanitise("nico:#{ raw }")
         tag = Tag.find_or_create_by_tag_name!(name, category: :nico)
+
+        event_type = tag.nico_tag_versions.exists? ? :update : :create
+        NicoTagVersionRecorder.record!(tag:, event_type:, created_by_user: nil)
+
         desired_nico_tag_based_ids << tag.id
 
         # 新たに記載される外部タグと連携される内部タグを記載
@@ -149,6 +153,7 @@ namespace :nico do
       if post_created
         PostVersionRecorder.record!(post:, event_type: :create, created_by_user: nil)
       elsif post_changed || kept_tag_ids != desired_all_tag_ids.to_set
+        PostVersionRecorder.ensure_snapshot!(post, created_by_user: nil)
         PostVersionRecorder.record!(post:, event_type: :update, created_by_user: nil)
       end
     end

backend/spec/factories/wiki_pages.rb

@@ -3,5 +3,7 @@ FactoryBot.define do
     title { "TestPage" }
     association :created_user, factory: :user
     association :updated_user, factory: :user
+
+    body { ' ' }
   end
 end

backend/spec/models/tag_spec.rb

@@ -107,11 +107,13 @@ RSpec.describe Tag, type: :model do
     context 'when the source tag_name has a wiki_page' do
       let!(:source_post_tag) { PostTag.create!(post: post_record, tag: source_tag) }
       let!(:wiki_page) do
-        WikiPage.create!(
+        admin = create_admin_user!
-          tag_name: source_tag_name,
+
-          created_user: create_admin_user!,
+        Wiki::Commit.create_content!(
-          updated_user: create_admin_user!
+            tag_name: source_tag_name,
-        )
+            body: 'source wiki body',
+            created_by_user: admin,
+            message: 'init')
       end
 
       it 'rolls back the transaction' do

backend/spec/models/version_record_spec.rb

@@ -0,0 +1,74 @@
+require 'rails_helper'
+
+RSpec.describe VersionRecord, type: :model do
+  let!(:tag) { create(:tag, name: 'version_record_tag') }
+  let!(:nico_tag) { create(:tag, :nico, name: 'nico:version_record_tag') }
+
+  it 'makes TagVersion read only after create' do
+    version = TagVersion.create!(
+      tag: tag,
+      version_no: 1,
+      event_type: 'create',
+      name: tag.name,
+      category: tag.category,
+      aliases: '',
+      parent_tag_ids: '',
+      created_at: Time.current,
+      created_by_user: nil
+    )
+
+    expect {
+      version.update!(name: 'changed')
+    }.to raise_error(ActiveRecord::ReadOnlyRecord)
+  end
+
+  it 'prevents TagVersion destroy' do
+    version = TagVersion.create!(
+      tag: tag,
+      version_no: 1,
+      event_type: 'create',
+      name: tag.name,
+      category: tag.category,
+      aliases: '',
+      parent_tag_ids: '',
+      created_at: Time.current,
+      created_by_user: nil
+    )
+
+    expect {
+      version.destroy!
+    }.to raise_error(ActiveRecord::ReadOnlyRecord)
+  end
+
+  it 'makes NicoTagVersion read only after create' do
+    version = NicoTagVersion.create!(
+      tag: nico_tag,
+      version_no: 1,
+      event_type: 'create',
+      name: nico_tag.name,
+      linked_tags: '',
+      created_at: Time.current,
+      created_by_user: nil
+    )
+
+    expect {
+      version.update!(name: 'nico:changed')
+    }.to raise_error(ActiveRecord::ReadOnlyRecord)
+  end
+
+  it 'prevents NicoTagVersion destroy' do
+    version = NicoTagVersion.create!(
+      tag: nico_tag,
+      version_no: 1,
+      event_type: 'create',
+      name: nico_tag.name,
+      linked_tags: '',
+      created_at: Time.current,
+      created_by_user: nil
+    )
+
+    expect {
+      version.destroy!
+    }.to raise_error(ActiveRecord::ReadOnlyRecord)
+  end
+end

backend/spec/requests/nico_tags_spec.rb

@@ -14,6 +14,7 @@ RSpec.describe 'NicoTags', type: :request do
 
   describe 'PATCH /tags/nico/:id' do
     let(:member) { create(:user, :member) }
+    let(:admin) { create(:user, :admin) }
     let(:nico_tag) { create(:tag, :nico) }
 
     it '401 when not logged in' do
@@ -34,5 +35,59 @@ RSpec.describe 'NicoTags', type: :request do
       patch "/tags/nico/#{non_nico.id}", params: { tags: 'a b' }
       expect(response).to have_http_status(:bad_request)
     end
+
+    it '200 and updates linked tags while recording tag versions' do
+      sign_in_as(admin)
+
+      nico_tag_name = TagName.create!(name: 'nico:nico_tags_spec_source')
+      nico_tag = Tag.create!(tag_name: nico_tag_name, category: :nico)
+
+      linked_a_name = TagName.create!(name: 'nico_linked_a')
+      linked_a = Tag.create!(tag_name: linked_a_name, category: :general)
+
+      linked_b_name = TagName.create!(name: 'nico_linked_b')
+      linked_b = Tag.create!(tag_name: linked_b_name, category: :general)
+
+      TagVersioning.ensure_snapshot!(nico_tag, created_by_user: admin)
+
+      expect {
+        patch "/tags/nico/#{nico_tag.id}", params: {
+          tags: "  #{linked_a.name}\n#{linked_b.name}  "
+        }
+      }.to change(TagVersion, :count).by(2)
+       .and change(NicoTagVersion, :count).by(1)
+
+      expect(response).to have_http_status(:ok)
+
+      names = json.map { |t| t['name'] }
+      expect(names).to match_array(['nico_linked_a', 'nico_linked_b'])
+
+      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))
+
+      versions = nico_tag.reload.nico_tag_versions.order(:version_no)
+      expect(versions.map(&:event_type)).to eq(['create', 'update'])
+      expect(versions.last.linked_tags.split).to match_array([
+        'nico_linked_a',
+        'nico_linked_b'
+      ])
+      expect(versions.last.created_by_user_id).to eq(admin.id)
+    end
+
+    it '400 when linked tag normalises to nico tag' do
+      sign_in_as(member)
+
+      other_nico = create(:tag, :nico, name: 'nico:linked_ng')
+      TagName.create!(name: 'linked_ng_alias', canonical: other_nico.tag_name)
+
+      TagVersioning.ensure_snapshot!(nico_tag, created_by_user: member)
+
+      expect {
+        patch "/tags/nico/#{nico_tag.id}", params: { tags: 'linked_ng_alias' }
+      }.not_to change(NicoTagVersion, :count)
+
+      expect(response).to have_http_status(:bad_request)
+    end
   end
 end

backend/spec/requests/posts_spec.rb

@@ -1,8 +1,8 @@
-include ActiveSupport::Testing::TimeHelpers
-
 require 'rails_helper'
 require 'set'
 
+include ActiveSupport::Testing::TimeHelpers
+
 RSpec.describe 'Posts API', type: :request do
   # create / update で thumbnail.attach は走るが、
   # resized_thumbnail! が MiniMagick 依存でコケやすいので request spec ではスタブしとくのが無難。
@@ -1082,15 +1082,16 @@ RSpec.describe 'Posts API', type: :request do
 
     it 'does not create a new version on PUT /posts/:id when snapshot is unchanged' do
       sign_in_as(member)
-      create_post_version_for!(post_record)
 
-      expect do
+      PostTag.create!(post: post_record, tag: Tag.no_deerjikist)
+      create_post_version_for!(post_record.reload)
+
+      expect {
         put "/posts/#{post_record.id}", params: {
           title: post_record.title,
           tags: 'spec_tag'
         }
-      end.not_to change(PostVersion, :count)
+      }.not_to change(PostVersion, :count)
-
       expect(response).to have_http_status(:ok)
 
       version = post_record.reload.post_versions.order(:version_no).last
@@ -1130,4 +1131,52 @@ RSpec.describe 'Posts API', type: :request do
       expect(response).to have_http_status(:unprocessable_entity)
     end
   end
+
+  describe 'tag versioning from post write actions' do
+    let(:member) { create(:user, :member) }
+
+    it 'creates tag snapshot for normalised tags on POST /posts' do
+      sign_in_as(member)
+
+      expect {
+        post '/posts', params: {
+          title: 'tag versioned post',
+          url: 'https://example.com/tag-versioned-post',
+          tags: 'spec_tag',
+          thumbnail: dummy_upload
+        }
+      }.to change { tag.reload.tag_versions.count }.by(1)
+
+      expect(response).to have_http_status(:created)
+
+      version = tag.reload.tag_versions.order(:version_no).last
+      expect(version.version_no).to eq(1)
+      expect(version.event_type).to eq('create')
+      expect(version.name).to eq('spec_tag')
+      expect(version.category).to eq('general')
+      expect(version.created_by_user_id).to eq(member.id)
+    end
+
+    it 'creates tag snapshot for normalised tags on PUT /posts/:id' do
+      sign_in_as(member)
+
+      tag_name2 = TagName.create!(name: 'spec_tag_2')
+      tag2 = Tag.create!(tag_name: tag_name2, category: :general)
+
+      expect {
+        put "/posts/#{post_record.id}", params: {
+          title: 'updated title',
+          tags: 'spec_tag_2'
+        }
+      }.to change { tag2.reload.tag_versions.count }.by(1)
+
+      expect(response).to have_http_status(:ok)
+
+      version = tag2.reload.tag_versions.order(:version_no).last
+      expect(version.version_no).to eq(1)
+      expect(version.event_type).to eq('create')
+      expect(version.name).to eq('spec_tag_2')
+      expect(version.created_by_user_id).to eq(member.id)
+    end
+  end
 end

backend/spec/requests/tag_children_spec.rb

@@ -58,15 +58,47 @@ RSpec.describe "TagChildren", type: :request do
       end
     end
 
-    context "when Tag.find raises (invalid ids) it still returns 204" do
+    context "when Tag.find raises (invalid ids)" do
       before { stub_current_user(admin) }
 
       let(:parent_id) { -1 }
       let(:child_id) { -1 }
 
-      it "returns 204 (rescue nil)" do
+      it "returns 404" do
         do_request
-        expect(response).to have_http_status(:no_content)
+        expect(response).to have_http_status(:not_found)
+      end
+    end
+
+    context 'when parent is nico' do
+      before { stub_current_user(admin) }
+
+      let!(:parent) { create(:tag, :nico, name: 'nico:parent_ng') }
+      let(:parent_id) { parent.id }
+      let(:child_id) { child.id }
+
+      it 'returns 400 and does not create relation' do
+        expect {
+          do_request
+        }.not_to change(TagImplication, :count)
+
+        expect(response).to have_http_status(:bad_request)
+      end
+    end
+
+    context 'when child is nico' do
+      before { stub_current_user(admin) }
+
+      let!(:child) { create(:tag, :nico, name: 'nico:child_ng') }
+      let(:parent_id) { parent.id }
+      let(:child_id) { child.id }
+
+      it 'returns 400 and does not create relation' do
+        expect {
+          do_request
+        }.not_to change(TagImplication, :count)
+
+        expect(response).to have_http_status(:bad_request)
       end
     end
   end
@@ -116,17 +148,57 @@ RSpec.describe "TagChildren", type: :request do
 
         expect(response).to have_http_status(:no_content)
       end
+
+      it 'records create and update versions for child tag' do
+        expect {
+          do_request
+        }.to change(TagVersion, :count).by(2)
+
+        expect(response).to have_http_status(:no_content)
+
+        versions = child.reload.tag_versions.order(:version_no)
+        expect(versions.map(&:event_type)).to eq(['create', 'update'])
+        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)
+      end
     end
 
-    context "when Tag.find raises (invalid ids) it still returns 204" do
+    context "when Tag.find raises (invalid ids)" do
       before { stub_current_user(admin) }
 
       let(:parent_id) { -1 }
       let(:child_id) { -1 }
 
-      it "returns 204 (rescue nil)" do
+      it "returns 404" do
         do_request
-        expect(response).to have_http_status(:no_content)
+        expect(response).to have_http_status(:not_found)
+      end
+    end
+
+    context 'when parent is nico' do
+      before { stub_current_user(admin) }
+
+      let!(:parent) { create(:tag, :nico, name: 'nico:parent_ng_delete') }
+      let(:parent_id) { parent.id }
+      let(:child_id) { child.id }
+
+      it 'returns 400' do
+        do_request
+        expect(response).to have_http_status(:bad_request)
+      end
+    end
+
+    context 'when child is nico' do
+      before { stub_current_user(admin) }
+
+      let!(:child) { create(:tag, :nico, name: 'nico:child_ng_delete') }
+      let(:parent_id) { parent.id }
+      let(:child_id) { child.id }
+
+      it 'returns 400' do
+        do_request
+        expect(response).to have_http_status(:bad_request)
       end
     end
   end

backend/spec/requests/tag_versions_spec.rb

@@ -0,0 +1,243 @@
+require 'rails_helper'
+
+RSpec.describe 'TagVersions API', type: :request do
+  let(:member) { create(:user, :member, name: 'version member') }
+
+  let!(:tag) { create(:tag, name: 'tag_versions_target', category: :general) }
+  let!(:other_tag) { create(:tag, name: 'tag_versions_other', category: :general) }
+
+  let!(:parent_shared) { create(:tag, name: 'parent_shared', category: :general) }
+  let!(:parent_old) { create(:tag, name: 'parent_old', category: :general) }
+  let!(:parent_new) { create(:tag, name: 'parent_new', category: :general) }
+  let!(:other_parent) { create(:tag, name: 'other_parent', category: :general) }
+
+  let(:t_v1) { Time.zone.local(2020, 1, 1, 12, 0, 0) }
+  let(:t_v2) { Time.zone.local(2020, 1, 2, 12, 0, 0) }
+  let(:t_other) { Time.zone.local(2020, 1, 3, 12, 0, 0) }
+
+  def create_tag_version!(
+    tag:,
+    version_no:,
+    event_type:,
+    name:,
+    category:,
+    aliases: [],
+    parent_tags: [],
+    created_by_user:,
+    created_at:
+  )
+    TagVersion.create!(
+      tag: tag,
+      version_no: version_no,
+      event_type: event_type,
+      name: name,
+      category: category,
+      aliases: Array(aliases).join(' '),
+      parent_tag_ids: Array(parent_tags).map(&:id).join(' '),
+      created_by_user: created_by_user,
+      created_at: created_at
+    )
+  end
+
+  let!(:v1) do
+    create_tag_version!(
+      tag: tag,
+      version_no: 1,
+      event_type: 'create',
+      name: 'old_tag_name',
+      category: 'general',
+      aliases: ['alias_shared', 'alias_old'],
+      parent_tags: [parent_shared, parent_old],
+      created_by_user: member,
+      created_at: t_v1
+    )
+  end
+
+  let!(:v2) do
+    create_tag_version!(
+      tag: tag,
+      version_no: 2,
+      event_type: 'update',
+      name: 'new_tag_name',
+      category: 'meme',
+      aliases: ['alias_shared', 'alias_new'],
+      parent_tags: [parent_shared, parent_new],
+      created_by_user: member,
+      created_at: t_v2
+    )
+  end
+
+  let!(:other_v1) do
+    create_tag_version!(
+      tag: other_tag,
+      version_no: 1,
+      event_type: 'create',
+      name: 'other_tag_name',
+      category: 'general',
+      aliases: ['other_alias'],
+      parent_tags: [other_parent],
+      created_by_user: member,
+      created_at: t_other
+    )
+  end
+
+  describe 'GET /tags/versions' do
+    it 'returns all versions in reverse chronological order when id is omitted' do
+      get '/tags/versions'
+
+      expect(response).to have_http_status(:ok)
+      expect(json).to include('versions', 'count')
+      expect(json.fetch('count')).to eq(3)
+
+      versions = json.fetch('versions')
+
+      expect(versions.map { |v| [v['tag_id'], v['version_no']] }).to eq([
+        [other_tag.id, 1],
+        [tag.id, 2],
+        [tag.id, 1]
+      ])
+    end
+
+    it 'returns versions for the specified tag with diffs' do
+      get '/tags/versions', params: { id: tag.id }
+
+      expect(response).to have_http_status(:ok)
+      expect(json).to include('versions', 'count')
+      expect(json.fetch('count')).to eq(2)
+
+      versions = json.fetch('versions')
+      expect(versions.map { |v| v['tag_id'] }.uniq).to eq([tag.id])
+      expect(versions.map { |v| v['version_no'] }).to eq([2, 1])
+
+      latest = versions.first
+      expect(latest).to include(
+        'tag_id' => tag.id,
+        'version_no' => 2,
+        'event_type' => 'update',
+        'created_by_user' => {
+          'id' => member.id,
+          'name' => member.name
+        }
+      )
+
+      expect(latest.fetch('name')).to eq(
+        'current' => 'new_tag_name',
+        'prev' => 'old_tag_name'
+      )
+      expect(latest.fetch('category')).to eq(
+        'current' => 'meme',
+        'prev' => 'general'
+      )
+      expect(latest.fetch('aliases')).to include(
+        { 'name' => 'alias_shared', 'type' => 'context' },
+        { 'name' => 'alias_new', 'type' => 'added' },
+        { 'name' => 'alias_old', 'type' => 'removed' }
+      )
+      expect(latest.fetch('parent_tags')).to include(
+        a_hash_including(
+          'type' => 'context',
+          'tag' => a_hash_including(
+            'id' => parent_shared.id
+          )
+        ),
+        a_hash_including(
+          'type' => 'added',
+          'tag' => a_hash_including(
+            'id' => parent_new.id
+          )
+        ),
+        a_hash_including(
+          'type' => 'removed',
+          'tag' => a_hash_including(
+            'id' => parent_old.id
+          )
+        )
+      )
+      expect(latest.fetch('created_at')).to eq(t_v2.iso8601)
+
+      first = versions.second
+      expect(first).to include(
+        'tag_id' => tag.id,
+        'version_no' => 1,
+        'event_type' => 'create',
+        'created_by_user' => {
+          'id' => member.id,
+          'name' => member.name
+        }
+      )
+      expect(first.fetch('name')).to eq(
+        'current' => 'old_tag_name',
+        'prev' => nil
+      )
+      expect(first.fetch('category')).to eq(
+        'current' => 'general',
+        'prev' => nil
+      )
+      expect(first.fetch('aliases')).to include(
+        { 'name' => 'alias_shared', 'type' => 'added' },
+        { 'name' => 'alias_old', 'type' => 'added' }
+      )
+      expect(first.fetch('parent_tags')).to include(
+        a_hash_including(
+          'type' => 'added',
+          'tag' => a_hash_including(
+            'id' => parent_shared.id
+          )
+        ),
+        a_hash_including(
+          'type' => 'added',
+          'tag' => a_hash_including(
+            'id' => parent_old.id
+          )
+        )
+      )
+      expect(first.fetch('created_at')).to eq(t_v1.iso8601)
+    end
+
+    it 'returns empty when the specified tag has no versions' do
+      fresh_tag = create(:tag, name: 'no_versions_tag', category: :general)
+
+      get '/tags/versions', params: { id: fresh_tag.id }
+
+      expect(response).to have_http_status(:ok)
+      expect(json.fetch('versions')).to eq([])
+      expect(json.fetch('count')).to eq(0)
+    end
+
+    it 'clamps page and limit to at least 1' do
+      get '/tags/versions', params: { id: tag.id, page: 0, limit: 0 }
+
+      expect(response).to have_http_status(:ok)
+      expect(json.fetch('count')).to eq(2)
+
+      versions = json.fetch('versions')
+      expect(versions.size).to eq(1)
+      expect(versions.first['version_no']).to eq(2)
+    end
+
+    it 'does not create tag versions by wiki updates when tag has no versions yet' do
+      wiki_tag_name = TagName.create!(name: 'tag_versions_from_wiki')
+      wiki_tag = Tag.create!(tag_name: wiki_tag_name, category: :general)
+
+      wiki_page =
+          Wiki::Commit.create_content!(
+              tag_name: wiki_tag_name,
+              body: 'before',
+              created_by_user: member,
+              message: 'init')
+
+      Wiki::Commit.content!(
+          page: wiki_page,
+          body: 'after',
+          created_user: member,
+          message: 'edit',
+          base_revision_id: wiki_page.current_revision.id)
+
+      get '/tags/versions', params: { id: wiki_tag.id }
+
+      expect(response).to have_http_status(:ok)
+      expect(json.fetch('versions')).to eq([])
+      expect(json.fetch('count')).to eq(0)
+    end
+  end
+end

backend/spec/requests/tag_wiki_history_integrity_spec.rb

@@ -0,0 +1,160 @@
+require 'rails_helper'
+
+RSpec.describe 'Tag and wiki history integrity', type: :request do
+  let(:member_user) { create(:user, role: 'member') }
+
+  def stub_current_user user
+    allow_any_instance_of(ApplicationController).to receive(:current_user).and_return(user)
+  end
+
+  def create_tag! name:, category: :general
+    tag_name = TagName.create!(name:)
+    Tag.create!(tag_name:, category:)
+  end
+
+  def create_wiki_for_tag! tag:, body: 'wiki body', user: member_user
+    Wiki::Commit.create_content!(
+        tag_name: tag.tag_name,
+        body:,
+        created_by_user: user,
+        message: 'init')
+  end
+
+  before do
+    stub_current_user(member_user)
+  end
+
+  describe 'PATCH /tags/:id' do
+    it 'records wiki_version when tag name changes and tag has wiki' do
+      tag = create_tag!(name: 'patch_tag_wiki_before')
+      wiki_page = create_wiki_for_tag!(tag:, body: 'wiki body before')
+
+      expect {
+        patch "/tags/#{ tag.id }", params: {
+          name: 'patch_tag_wiki_after',
+        }
+      }
+          .to change(TagVersion, :count).by(2)
+          .and change(WikiVersion, :count).by(1)
+
+      expect(response).to have_http_status(:ok)
+
+      tag.reload
+      wiki_page.reload
+      version = wiki_page.wiki_versions.order(:version_no).last
+
+      expect(tag.name).to eq('patch_tag_wiki_after')
+      expect(wiki_page.title).to eq('patch_tag_wiki_after')
+
+      expect(version).to have_attributes(
+        event_type: 'update',
+        title: 'patch_tag_wiki_after',
+        body: 'wiki body before',
+        created_by_user_id: member_user.id
+      )
+    end
+
+    it 'does not record wiki_version when only category changes' do
+      tag = create_tag!(name: 'patch_tag_category_only')
+      wiki_page = create_wiki_for_tag!(tag:, body: 'wiki body before')
+
+      before_wiki_versions = wiki_page.wiki_versions.count
+
+      expect {
+        patch "/tags/#{ tag.id }", params: {
+          category: 'meme',
+        }
+      }
+          .to change(TagVersion, :count).by(2)
+
+      expect(response).to have_http_status(:ok)
+
+      tag.reload
+      wiki_page.reload
+
+      expect(tag.name).to eq('patch_tag_category_only')
+      expect(tag.category).to eq('meme')
+      expect(wiki_page.wiki_versions.count).to eq(before_wiki_versions)
+    end
+  end
+
+  describe 'PUT /tags/:id' do
+    it 'records wiki_version when tag name changes and tag has wiki' do
+      tag = create_tag!(name: 'put_tag_wiki_before')
+      wiki_page = create_wiki_for_tag!(tag:, body: 'wiki body before')
+
+      expect {
+        put "/tags/#{ tag.id }", params: {
+          name: 'put_tag_wiki_after',
+          category: 'general',
+          aliases: '',
+          parent_tags: '',
+        }
+      }
+          .to change(TagVersion, :count).by(2)
+          .and change(WikiVersion, :count).by(1)
+
+      expect(response).to have_http_status(:ok)
+
+      tag.reload
+      wiki_page.reload
+      version = wiki_page.wiki_versions.order(:version_no).last
+
+      expect(tag.name).to eq('put_tag_wiki_after')
+      expect(wiki_page.title).to eq('put_tag_wiki_after')
+
+      expect(version).to have_attributes(
+        event_type: 'update',
+        title: 'put_tag_wiki_after',
+        body: 'wiki body before',
+        created_by_user_id: member_user.id
+      )
+    end
+
+    it 'does not record wiki_version when only category changes' do
+      tag = create_tag!(name: 'put_tag_category_only')
+      wiki_page = create_wiki_for_tag!(tag:, body: 'wiki body before')
+
+      before_wiki_versions = wiki_page.wiki_versions.count
+
+      expect {
+        put "/tags/#{ tag.id }", params: {
+          name: 'put_tag_category_only',
+          category: 'meme',
+          aliases: '',
+          parent_tags: '',
+        }
+      }
+          .to change(TagVersion, :count).by(2)
+
+      expect(response).to have_http_status(:ok)
+
+      tag.reload
+      wiki_page.reload
+
+      expect(tag.name).to eq('put_tag_category_only')
+      expect(tag.category).to eq('meme')
+      expect(wiki_page.wiki_versions.count).to eq(before_wiki_versions)
+    end
+
+    it 'does not record wiki_version when only aliases change' do
+      tag = create_tag!(name: 'put_tag_alias_only')
+      wiki_page = create_wiki_for_tag!(tag:, body: 'wiki body before')
+
+      before_wiki_versions = wiki_page.wiki_versions.count
+
+      expect {
+        put "/tags/#{ tag.id }", params: {
+          name: 'put_tag_alias_only',
+          category: 'general',
+          aliases: 'put_tag_alias_only_alias',
+          parent_tags: '',
+        }
+      }
+          .to change(TagVersion, :count).by(2)
+
+      expect(response).to have_http_status(:ok)
+      expect(wiki_page.reload.wiki_versions.count).to eq(before_wiki_versions)
+    end
+  end
+end

backend/spec/requests/tags_spec.rb

@@ -1,7 +1,6 @@
 require 'cgi'
 require 'rails_helper'
 
-
 RSpec.describe 'Tags API', type: :request do
   let!(:tn) { TagName.create!(name: 'spec_tag') }
   let!(:tag) { Tag.create!(tag_name: tn, category: :general) }
@@ -197,6 +196,30 @@ RSpec.describe 'Tags API', type: :request do
       expect(response_tags.size).to eq(1)
       expect(response_names).to eq(['norm_a'])
     end
+
+    it 'returns aliases and parent tags' do
+      parent_tag = Tag.create!(
+        tag_name: TagName.create!(name: 'index_parent_tag'),
+        category: :meme
+      )
+      TagImplication.create!(tag:, parent_tag:)
+
+      get '/tags', params: { name: 'spec_tag' }
+
+      expect(response).to have_http_status(:ok)
+
+      row = response_tags.find { |t| t['name'] == 'spec_tag' }
+
+      expect(row['aliases']).to include('unko')
+      expect(row['parents'].map { |t| t['name'] }).to include('index_parent_tag')
+
+      parent = row['parents'].find { |t| t['name'] == 'index_parent_tag' }
+      expect(parent).to include(
+        'id' => parent_tag.id,
+        'name' => 'index_parent_tag',
+        'category' => 'meme'
+      )
+    end
   end
 
   describe 'GET /tags/:id' do
@@ -220,6 +243,28 @@ RSpec.describe 'Tags API', type: :request do
         expect(json).to have_key('created_at')
         expect(json).to have_key('updated_at')
       end
+
+      it 'returns aliases and parent tags' do
+        parent_tag = Tag.create!(
+          tag_name: TagName.create!(name: 'show_parent_tag'),
+          category: :character
+        )
+        TagImplication.create!(tag:, parent_tag:)
+
+        request
+
+        expect(response).to have_http_status(:ok)
+
+        expect(json['aliases']).to include('unko')
+        expect(json['parents'].map { |t| t['name'] }).to include('show_parent_tag')
+
+        parent = json['parents'].find { |t| t['name'] == 'show_parent_tag' }
+        expect(parent).to include(
+          'id' => parent_tag.id,
+          'name' => 'show_parent_tag',
+          'category' => 'character'
+        )
+      end
     end
 
     context 'when tag does not exist' do
@@ -359,14 +404,120 @@ RSpec.describe 'Tags API', type: :request do
         expect(tag.category).to eq('meta')
       end
 
-      it '存在しない id だと RecordNotFound になる（通常は 404）' do
+      it '存在しない id なら 404 を返す' do
         patch '/tags/999999999', params: { name: 'x' }
-        expect(response.status).to be_in([404, 500])
+        expect(response).to have_http_status(:not_found)
       end
 
-      it 'バリデーションで update! が失敗したら（通常は 422 か 500）' do
+      it 'nico category への変更は 422 を返す' do
-        patch "/tags/#{ tag.id }", params: { name: 'new', category: 'nico' }
+        patch "/tags/#{tag.id}", params: { name: 'new', category: 'nico' }
-        expect(response.status).to be_in([422, 500])
+
+        expect(response).to have_http_status(:unprocessable_entity)
+        expect(tag.reload.name).to eq('spec_tag')
+        expect(tag.category).to eq('general')
+      end
+
+      it 'creates initial and update tag versions when name and category change' do
+        expect {
+          patch "/tags/#{tag.id}", params: { name: 'new_tag_name', category: 'meme' }
+        }.to change(TagVersion, :count).by(2)
+
+        expect(response).to have_http_status(:ok)
+
+        versions = tag.reload.tag_versions.order(:version_no)
+
+        expect(versions.map(&:event_type)).to eq(['create', 'update'])
+
+        expect(versions.first.name).to eq('spec_tag')
+        expect(versions.first.category).to eq('general')
+        expect(versions.first.aliases.split).to include('unko')
+
+        expect(versions.second.name).to eq('new_tag_name')
+        expect(versions.second.category).to eq('meme')
+        expect(versions.second.created_by_user_id).to eq(member_user.id)
+      end
+
+      it 'returns 422 when changing normal tag category to nico' do
+        expect {
+          patch "/tags/#{tag.id}", params: { category: 'nico' }
+        }.not_to change(TagVersion, :count)
+
+        expect(response).to have_http_status(:unprocessable_entity)
+        expect(tag.reload.category).to eq('general')
+      end
+
+      it 'returns 422 when updating nico tag name' do
+        nico_tag_name = TagName.create!(name: 'nico:tags_spec_source')
+        nico_tag = Tag.create!(tag_name: nico_tag_name, category: :nico)
+
+        expect {
+          patch "/tags/#{ nico_tag.id }", params: { name: 'nico:tags_spec_renamed' }
+        }.not_to change(NicoTagVersion, :count)
+
+        expect(response).to have_http_status(:unprocessable_entity)
+
+        expect(nico_tag.reload.name).to eq('nico:tags_spec_source')
+        expect(nico_tag.category).to eq('nico')
+      end
+
+      it 'returns 422 when changing nico tag category to normal category' do
+        nico_tag_name = TagName.create!(name: 'nico:category_change_ng')
+        nico_tag = Tag.create!(tag_name: nico_tag_name, category: :nico)
+
+        expect {
+          patch "/tags/#{nico_tag.id}", params: { category: 'general' }
+        }.not_to change(NicoTagVersion, :count)
+
+        expect(response).to have_http_status(:unprocessable_entity)
+        expect(nico_tag.reload.category).to eq('nico')
+      end
+
+      it 'PATCH で tag の name を変更すると対応する wiki version を作成する' do
+        wiki_page =
+            Wiki::Commit.create_content!(
+                tag_name: tag.tag_name,
+                body: 'wiki body before',
+                created_by_user: member_user,
+                message: 'init')
+
+        expect {
+          patch "/tags/#{ tag.id }", params: {
+            name: 'patch_wiki_renamed_tag',
+          }
+        }
+            .to change(TagVersion, :count).by(2)
+            .and change(WikiVersion, :count).by(1)
+
+        expect(response).to have_http_status(:ok)
+
+        version = wiki_page.reload.wiki_versions.order(:version_no).last
+
+        expect(version).to have_attributes(
+          event_type: 'update',
+          title: 'patch_wiki_renamed_tag',
+          body: 'wiki body before',
+          created_by_user_id: member_user.id
+        )
+      end
+
+      it 'tag の category だけを変更しても wiki version は作成しない' do
+        wiki_page =
+            Wiki::Commit.create_content!(
+                tag_name: tag.tag_name,
+                body: 'wiki body before',
+                created_by_user: member_user,
+                message: 'init')
+
+        before_wiki_version_count = wiki_page.reload.wiki_versions.count
+
+        expect {
+          patch "/tags/#{ tag.id }", params: {
+            category: 'meme',
+          }
+        }.to change(TagVersion, :count).by(2)
+
+        expect(response).to have_http_status(:ok)
+        expect(wiki_page.reload.wiki_versions.count).to eq(before_wiki_version_count)
       end
     end
   end
@@ -510,4 +661,397 @@ RSpec.describe 'Tags API', type: :request do
       expect(response).to have_http_status(:not_found)
     end
   end
+
+  describe 'PUT /tags/:id' do
+    context '未ログイン' do
+      before { stub_current_user(nil) }
+
+      it '401 を返す' do
+        put "/tags/#{ tag.id }", params: {
+          name: 'new',
+          category: 'general',
+          aliases: '',
+          parent_tags: '',
+        }
+
+        expect(response).to have_http_status(:unauthorized)
+      end
+    end
+
+    context 'ログインしてゐるが member でない' do
+      before { stub_current_user(non_member_user) }
+
+      it '403 を返す' do
+        put "/tags/#{ tag.id }", params: {
+          name: 'new',
+          category: 'general',
+          aliases: '',
+          parent_tags: '',
+        }
+
+        expect(response).to have_http_status(:forbidden)
+      end
+    end
+
+    context 'member' do
+      before { stub_current_user(member_user) }
+
+      it '存在しない id なら 404 を返す' do
+        put '/tags/999999999', params: {
+          name: 'new',
+          category: 'general',
+          aliases: '',
+          parent_tags: '',
+        }
+
+        expect(response).to have_http_status(:not_found)
+      end
+
+      it 'name が空なら 422 を返す' do
+        put "/tags/#{ tag.id }", params: {
+          name: '',
+          category: 'general',
+          aliases: '',
+          parent_tags: '',
+        }
+
+        expect(response).to have_http_status(:unprocessable_entity)
+        expect(tag.reload.name).to eq('spec_tag')
+      end
+
+      it 'category が空なら 422 を返す' do
+        put "/tags/#{ tag.id }", params: {
+          name: 'new',
+          category: '',
+          aliases: '',
+          parent_tags: '',
+        }
+
+        expect(response).to have_http_status(:unprocessable_entity)
+        expect(tag.reload.name).to eq('spec_tag')
+        expect(tag.category).to eq('general')
+      end
+
+      it 'name, category, aliases, parent tags をまとめて更新できる' do
+        old_parent = Tag.create!(
+          tag_name: TagName.create!(name: 'put_old_parent'),
+          category: :general
+        )
+        kept_parent = Tag.create!(
+          tag_name: TagName.create!(name: 'put_kept_parent'),
+          category: :general
+        )
+        TagImplication.create!(tag:, parent_tag: old_parent)
+        TagImplication.create!(tag:, parent_tag: kept_parent)
+
+        put "/tags/#{ tag.id }", params: {
+          name: 'put_renamed_tag',
+          category: 'meme',
+          aliases: 'put_alias_a put_alias_b put_alias_a',
+          parent_tags: 'put_kept_parent put_new_parent',
+        }
+
+        expect(response).to have_http_status(:ok)
+
+        tag.reload
+
+        expect(tag.name).to eq('put_renamed_tag')
+        expect(tag.category).to eq('meme')
+
+        expect(TagName.find_by(name: 'put_alias_a').canonical).to eq(tag.tag_name)
+        expect(TagName.find_by(name: 'put_alias_b').canonical).to eq(tag.tag_name)
+
+        old_name_alias = TagName.find_by(name: 'spec_tag')
+        expect(old_name_alias).to be_present
+        expect(old_name_alias.canonical).to eq(tag.tag_name)
+
+        expect(alias_tn.reload.canonical).to be_nil
+
+        expect(tag.parents.map(&:name)).to contain_exactly(
+          'put_kept_parent',
+          'put_new_parent'
+        )
+
+        expect(TagImplication.where(tag:, parent_tag: old_parent)).not_to exist
+
+        expect(json['name']).to eq('put_renamed_tag')
+        expect(json['category']).to eq('meme')
+        expect(json['aliases']).to contain_exactly(
+          'put_alias_a',
+          'put_alias_b',
+          'spec_tag'
+        )
+        expect(json['parents'].map { |t| t['name'] }).to contain_exactly(
+          'put_kept_parent',
+          'put_new_parent'
+        )
+      end
+
+      it 'aliases に現在名を指定しても alias には残さない' do
+        put "/tags/#{ tag.id }", params: {
+          name: 'spec_tag',
+          category: 'general',
+          aliases: 'spec_tag put_alias_self_test',
+          parent_tags: '',
+        }
+
+        expect(response).to have_http_status(:ok)
+
+        tag.reload
+
+        expect(TagName.find_by(name: 'put_alias_self_test').canonical).to eq(tag.tag_name)
+        expect(json['aliases']).to include('put_alias_self_test')
+        expect(json['aliases']).not_to include('spec_tag')
+      end
+
+      it 'parent_tags に自分自身を指定しても自己参照は作らない' do
+        put "/tags/#{ tag.id }", params: {
+          name: 'spec_tag',
+          category: 'general',
+          aliases: 'unko',
+          parent_tags: 'spec_tag',
+        }
+
+        expect(response).to have_http_status(:ok)
+
+        expect(TagImplication.where(tag:, parent_tag: tag)).not_to exist
+        expect(tag.reload.parents).to eq([])
+      end
+
+      it 'initial and update tag versions を作成する' do
+        expect {
+          put "/tags/#{ tag.id }", params: {
+            name: 'put_versioned_tag',
+            category: 'meta',
+            aliases: '',
+            parent_tags: '',
+          }
+        }.to change(TagVersion, :count).by(2)
+
+        expect(response).to have_http_status(:ok)
+
+        versions = tag.reload.tag_versions.order(:version_no)
+
+        expect(versions.map(&:event_type)).to eq(['create', 'update'])
+
+        expect(versions.first.name).to eq('spec_tag')
+        expect(versions.first.category).to eq('general')
+        expect(versions.first.aliases.split).to include('unko')
+
+        expect(versions.second.name).to eq('put_versioned_tag')
+        expect(versions.second.category).to eq('meta')
+        expect(versions.second.aliases.split).to include('spec_tag')
+        expect(versions.second.created_by_user_id).to eq(member_user.id)
+      end
+
+      it 'parent tag の snapshot も作成する' do
+        old_parent = Tag.create!(
+          tag_name: TagName.create!(name: 'put_snapshot_old_parent'),
+          category: :general
+        )
+        new_parent = Tag.create!(
+          tag_name: TagName.create!(name: 'put_snapshot_new_parent'),
+          category: :general
+        )
+        TagImplication.create!(tag:, parent_tag: old_parent)
+
+        put "/tags/#{ tag.id }", params: {
+          name: 'spec_tag',
+          category: 'general',
+          aliases: 'unko',
+          parent_tags: new_parent.name,
+        }
+
+        expect(response).to have_http_status(:ok)
+
+        expect(old_parent.reload.tag_versions.map(&:event_type)).to include('create')
+        expect(new_parent.reload.tag_versions.map(&:event_type)).to include('create')
+      end
+
+      it 'normal tag を nico category には変更できない' do
+        expect {
+          put "/tags/#{ tag.id }", params: {
+            name: 'spec_tag',
+            category: 'nico',
+            aliases: '',
+            parent_tags: '',
+          }
+        }.not_to change(TagVersion, :count)
+
+        expect(response).to have_http_status(:unprocessable_entity)
+
+        expect(tag.reload.name).to eq('spec_tag')
+        expect(tag.category).to eq('general')
+      end
+
+      it 'nico tag は更新できない' do
+        nico_tag = Tag.create!(
+          tag_name: TagName.create!(name: 'nico:put_update_all_ng'),
+          category: :nico
+        )
+
+        expect {
+          put "/tags/#{ nico_tag.id }", params: {
+            name: 'nico:put_update_all_renamed',
+            category: 'nico',
+            aliases: '',
+            parent_tags: '',
+          }
+        }.not_to change(NicoTagVersion, :count)
+
+        expect(response).to have_http_status(:unprocessable_entity)
+
+        expect(nico_tag.reload.name).to eq('nico:put_update_all_ng')
+        expect(nico_tag.category).to eq('nico')
+      end
+
+      it 'system tag の name は変更できない' do
+        system_tag = Tag.tagme
+        old_name = system_tag.name
+        old_category = system_tag.category
+
+        expect {
+          put "/tags/#{ system_tag.id }", params: {
+            name: 'put_system_tag_renamed',
+            category: old_category,
+            aliases: '',
+            parent_tags: '',
+          }
+        }.not_to change(TagVersion, :count)
+
+        expect(response).to have_http_status(:unprocessable_entity)
+
+        expect(system_tag.reload.name).to eq(old_name)
+        expect(system_tag.category).to eq(old_category)
+      end
+
+      it 'wiki を持つ tag を更新すると wiki version も作成する' do
+        wiki_page =
+            Wiki::Commit.create_content!(
+                tag_name: tag.tag_name,
+                body: 'wiki body before',
+                created_by_user: member_user,
+                message: 'init')
+
+        Wiki::Commit.content!(
+          page: wiki_page,
+          body: 'wiki body before',
+          created_user: member_user,
+          message: 'init'
+        )
+
+        expect {
+          put "/tags/#{ tag.id }", params: {
+            name: 'put_wiki_version_tag',
+            category: 'meme',
+            aliases: 'unko',
+            parent_tags: '',
+          }
+        }
+            .to change(TagVersion, :count).by(2)
+            .and change(WikiVersion, :count).by(1)
+
+        expect(response).to have_http_status(:ok)
+
+        version = wiki_page.reload.wiki_versions.order(:version_no).last
+
+        expect(version).to have_attributes(
+          event_type: 'update',
+          title: 'put_wiki_version_tag',
+          body: 'wiki body before',
+          created_by_user_id: member_user.id
+        )
+      end
+
+      it '別名を他 tag から奪った場合、奪はれた側の tag version も作成する' do
+        old_owner = Tag.create!(
+          tag_name: TagName.create!(name: 'put_alias_old_owner'),
+          category: :general
+        )
+        stolen_alias = TagName.create!(
+          name: 'put_stolen_alias',
+          canonical: old_owner.tag_name
+        )
+
+        expect(old_owner.tag_name.aliases.map(&:name)).to include('put_stolen_alias')
+
+        expect {
+          put "/tags/#{ tag.id }", params: {
+            name: 'spec_tag',
+            category: 'general',
+            aliases: 'unko put_stolen_alias',
+            parent_tags: '',
+          }
+        }
+            .to change { tag.reload.tag_versions.count }.by(2)
+            .and change { old_owner.reload.tag_versions.count }.by(2)
+
+        expect(response).to have_http_status(:ok)
+
+        expect(stolen_alias.reload.canonical).to eq(tag.tag_name)
+        expect(old_owner.reload.tag_name.aliases.map(&:name)).not_to include('put_stolen_alias')
+
+        old_owner_versions = old_owner.tag_versions.order(:version_no)
+
+        expect(old_owner_versions.first.event_type).to eq('create')
+        expect(old_owner_versions.first.aliases.split).to include('put_stolen_alias')
+
+        expect(old_owner_versions.second.event_type).to eq('update')
+        expect(old_owner_versions.second.aliases.split).not_to include('put_stolen_alias')
+      end
+
+      it 'parent_tags に指定すると循環する tag は 422 にする' do
+        pending '#332 で対応予定'
+
+        child = Tag.create!(
+          tag_name: TagName.create!(name: 'put_cycle_child'),
+          category: :general
+        )
+
+        TagImplication.create!(tag: child, parent_tag: tag)
+
+        put "/tags/#{ tag.id }", params: {
+          name: 'spec_tag',
+          category: 'general',
+          aliases: 'unko',
+          parent_tags: child.name,
+        }
+
+        expect(response).to have_http_status(:unprocessable_entity)
+
+        expect(TagImplication.where(tag:, parent_tag: child)).not_to exist
+      end
+
+      it 'tag の name を変更すると対応する wiki version を作成する' do
+        wiki_page =
+            Wiki::Commit.create_content!(
+                tag_name: tag.tag_name,
+                body: 'wiki body before',
+                created_by_user: member_user,
+                message: 'init')
+
+        expect {
+          put "/tags/#{ tag.id }", params: {
+            name: 'put_wiki_renamed_tag',
+            category: 'general',
+            aliases: 'unko',
+            parent_tags: '',
+          }
+        }
+            .to change(TagVersion, :count).by(2)
+            .and change(WikiVersion, :count).by(1)
+
+        expect(response).to have_http_status(:ok)
+
+        version = wiki_page.reload.wiki_versions.order(:version_no).last
+
+        expect(version).to have_attributes(
+          event_type: 'update',
+          title: 'put_wiki_renamed_tag',
+          body: 'wiki body before',
+          created_by_user_id: member_user.id
+        )
+      end
+    end
+  end
 end

backend/spec/requests/users_spec.rb

@@ -1,11 +1,10 @@
 require "rails_helper"
 
-
 RSpec.describe "Users", type: :request do
   describe "POST /users" do
     it "creates guest user and returns code" do
       post "/users"
-      expect(response).to have_http_status(:ok)
+      expect(response).to have_http_status(:created)
       expect(json["code"]).to be_present
       expect(json["user"]["role"]).to eq("guest")
     end
@@ -38,7 +37,7 @@ RSpec.describe "Users", type: :request do
       sign_in_as(user)
       put "/users/#{user.id}", params: { name: "new-name" }
 
-      expect(response).to have_http_status(:created)
+      expect(response).to have_http_status(:ok)
       expect(json["id"]).to eq(user.id)
       expect(json["name"]).to eq("new-name")
 

backend/spec/requests/wiki_body_search_pending_spec.rb

@@ -0,0 +1,27 @@
+require 'rails_helper'
+
+RSpec.describe 'Wiki body search', type: :request do
+  let!(:user) { create_member_user! }
+
+  it 'searches wiki pages by body text' do
+    pending '#336 で対応予定'
+
+    Wiki::Commit.create_content!(
+        tag_name: TagName.create!(name: 'wiki_body_search_hit'),
+        body: 'unique body keyword for wiki search',
+        created_by_user: user,
+        message: 'init')
+
+    Wiki::Commit.create_content!(
+        tag_name: TagName.create!(name: 'wiki_body_search_miss'),
+        body: 'ordinary body',
+        created_by_user: user,
+        message: 'init')
+
+    get '/wiki/search', params: { body: 'unique body keyword' }
+
+    expect(response).to have_http_status(:ok)
+    expect(json.map { |page| page['title'] }).to include('wiki_body_search_hit')
+    expect(json.map { |page| page['title'] }).not_to include('wiki_body_search_miss')
+  end
+end

backend/spec/requests/wiki_conflict_spec.rb

@@ -0,0 +1,42 @@
+require 'rails_helper'
+
+RSpec.describe 'Wiki conflict handling', type: :request do
+  let!(:user) { create_member_user! }
+
+  def auth_headers user
+    { 'X-Transfer-Code' => user.inheritance_code }
+  end
+
+  it 'returns 409 when base_revision_id is stale' do
+    page =
+        Wiki::Commit.create_content!(
+            tag_name: TagName.create!(name: 'wiki_conflict_request'),
+            body: 'first',
+            created_by_user: user,
+            message: 'init')
+
+    stale_id = page.current_revision.id
+
+    Wiki::Commit.content!(
+        page:,
+        body: 'second',
+        created_user: user,
+        message: 'other edit',
+        base_revision_id: stale_id)
+
+    put "/wiki/#{ page.id }",
+        params: {
+          title: 'wiki_conflict_request',
+          body: 'third',
+          message: 'stale',
+          base_revision_id: stale_id,
+        },
+        headers: auth_headers(user)
+
+    expect(response).to have_http_status(:conflict)
+
+    page.reload
+    expect(page.body).to eq('second')
+    expect(page.current_revision.message).to eq('other edit')
+  end
+end

backend/spec/requests/wiki_history_integrity_spec.rb

@@ -0,0 +1,196 @@
+require 'cgi'
+require 'rails_helper'
+
+RSpec.describe 'Wiki history integrity', type: :request do
+  let!(:user) { create_member_user! }
+
+  def auth_headers user
+    { 'X-Transfer-Code' => user.inheritance_code }
+  end
+
+  def create_wiki_page title:, body: 'body', message: 'init', user: self.user
+    Wiki::Commit.create_content!(
+        tag_name: TagName.create!(name: title),
+        body:,
+        created_by_user: user,
+        message:)
+  end
+
+  describe 'POST /wiki' do
+    it 'creates wiki_page, wiki_revision, and wiki_version atomically' do
+      expect {
+        post '/wiki',
+             params: {
+               title: 'wiki_history_create_atomic',
+               body: "a\nb\nc",
+               message: 'initial commit',
+             },
+             headers: auth_headers(user)
+      }
+          .to change(WikiPage, :count).by(1)
+          .and change(WikiRevision, :count).by(1)
+          .and change(WikiVersion, :count).by(1)
+
+      expect(response).to have_http_status(:created)
+
+      page = WikiPage.find(json.fetch('id'))
+      revision = page.current_revision
+      version = page.wiki_versions.order(:version_no).last
+
+      expect(page.title).to eq('wiki_history_create_atomic')
+      expect(page.body).to eq("a\nb\nc")
+
+      expect(revision).to be_content
+      expect(revision.message).to eq('initial commit')
+      expect(revision.lines_count).to eq(3)
+
+      expect(version).to have_attributes(
+        version_no: 1,
+        event_type: 'create',
+        title: 'wiki_history_create_atomic',
+        body: "a\nb\nc",
+        reason: 'initial commit',
+        created_by_user_id: user.id
+      )
+    end
+
+    it 'returns 422 and creates nothing when normalised body is blank' do
+      expect {
+        post '/wiki',
+             params: {
+               title: 'wiki_history_blank_body',
+               body: "\r\n\r\n",
+               message: 'blank',
+             },
+             headers: auth_headers(user)
+      }
+          .not_to change(WikiPage, :count)
+
+      expect(response).to have_http_status(:unprocessable_entity)
+      expect(WikiPage.joins(:tag_name).where(tag_names: { name: 'wiki_history_blank_body' })).not_to exist
+    end
+
+    it 'returns 422 and creates no partial page when title already exists' do
+      create_wiki_page(title: 'wiki_history_duplicate_title', body: 'first')
+
+      expect {
+        post '/wiki',
+             params: {
+               title: 'wiki_history_duplicate_title',
+               body: 'second',
+               message: 'duplicate',
+             },
+             headers: auth_headers(user)
+      }
+          .not_to change(WikiPage, :count)
+
+      expect(response).to have_http_status(:unprocessable_entity)
+      expect(WikiPage.joins(:tag_name).where(tag_names: { name: 'wiki_history_duplicate_title' }).count).to eq(1)
+    end
+  end
+
+  describe 'PUT /wiki/:id' do
+    it 'updates body and records wiki_revision and wiki_version' do
+      page = create_wiki_page(title: 'wiki_history_update_body', body: 'before')
+      current_id = page.current_revision.id
+
+      expect {
+        put "/wiki/#{ page.id }",
+            params: {
+              title: 'wiki_history_update_body',
+              body: 'after',
+              message: 'edit body',
+              base_revision_id: current_id,
+            },
+            headers: auth_headers(user)
+      }
+          .to change(WikiRevision, :count).by(1)
+          .and change(WikiVersion, :count).by(1)
+
+      expect(response).to have_http_status(:ok)
+
+      page.reload
+      version = page.wiki_versions.order(:version_no).last
+
+      expect(page.title).to eq('wiki_history_update_body')
+      expect(page.body).to eq('after')
+
+      expect(version).to have_attributes(
+        event_type: 'update',
+        title: 'wiki_history_update_body',
+        body: 'after',
+        reason: 'edit body',
+        created_by_user_id: user.id
+      )
+    end
+
+    it 'renames title and records wiki_version with new title' do
+      page = create_wiki_page(title: 'wiki_history_rename_before', body: 'before')
+      current_id = page.current_revision.id
+
+      expect {
+        put "/wiki/#{ page.id }",
+            params: {
+              title: 'wiki_history_rename_after',
+              body: 'after',
+              message: 'rename',
+              base_revision_id: current_id,
+            },
+            headers: auth_headers(user)
+      }
+          .to change(WikiRevision, :count).by(1)
+          .and change(WikiVersion, :count).by(1)
+
+      expect(response).to have_http_status(:ok)
+
+      page.reload
+      version = page.wiki_versions.order(:version_no).last
+
+      expect(page.title).to eq('wiki_history_rename_after')
+      expect(page.body).to eq('after')
+
+      expect(version).to have_attributes(
+        event_type: 'update',
+        title: 'wiki_history_rename_after',
+        body: 'after',
+        reason: 'rename',
+        created_by_user_id: user.id
+      )
+    end
+
+    it 'does not change title, body, revision, or version on stale base_revision_id' do
+      page = create_wiki_page(title: 'wiki_history_conflict_page', body: 'first')
+      stale_id = page.current_revision.id
+
+      Wiki::Commit.content!(
+          page:,
+          body: 'second',
+          created_user: user,
+          message: 'other edit',
+          base_revision_id: stale_id)
+
+      page.reload
+      current_title = page.title
+      current_body = page.body
+      revision_count = page.wiki_revisions.count
+      version_count = page.wiki_versions.count
+
+      put "/wiki/#{ page.id }",
+          params: {
+            title: 'wiki_history_conflict_renamed',
+            body: 'third',
+            message: 'stale edit',
+            base_revision_id: stale_id,
+          },
+          headers: auth_headers(user)
+
+      expect(response).to have_http_status(:conflict)
+
+      page.reload
+      expect(page.title).to eq(current_title)
+      expect(page.body).to eq(current_body)
+      expect(page.wiki_revisions.count).to eq(revision_count)
+      expect(page.wiki_versions.count).to eq(version_count)
+    end
+  end
+end

backend/spec/requests/wiki_restore_pending_spec.rb

@@ -0,0 +1,37 @@
+require 'rails_helper'
+
+RSpec.describe 'Wiki restore', type: :request do
+  let!(:user) { create_member_user! }
+
+  def auth_headers user
+    { 'X-Transfer-Code' => user.inheritance_code }
+  end
+
+  it 'restores wiki page to previous version' do
+    pending '#337 で対応予定'
+
+    page =
+        Wiki::Commit.create_content!(
+            tag_name: TagName.create!(name: 'wiki_restore_page'),
+            body: 'v1',
+            created_by_user: user,
+            message: 'init')
+
+    v1 = page.wiki_versions.order(:version_no).last
+
+    Wiki::Commit.content!(
+        page:,
+        body: 'v2',
+        created_user: user,
+        message: 'edit',
+        base_revision_id: page.current_revision.id)
+
+    post "/wiki/#{ page.id }/restore",
+         params: { version_no: v1.version_no },
+         headers: auth_headers(user)
+
+    expect(response).to have_http_status(:ok)
+    expect(page.reload.body).to eq('v1')
+    expect(page.wiki_versions.order(:version_no).last.event_type).to eq('restore')
+  end
+end

backend/spec/requests/wiki_spec.rb

@@ -4,13 +4,19 @@ require 'securerandom'
 
 
 RSpec.describe 'Wiki API', type: :request do
+  def auth_headers(user)
+    { 'X-Transfer-Code' => user.inheritance_code }
+  end
+
   let!(:user) { create_member_user! }
 
   let!(:tn) { TagName.create!(name: 'spec_wiki_title') }
   let!(:page) do
-    WikiPage.create!(tag_name: tn, created_user: user, updated_user: user).tap do |p|
+    Wiki::Commit.create_content!(
-      Wiki::Commit.content!(page: p, body: 'init', created_user: user, message: 'init')
+        tag_name: tn,
-    end
+        body: 'init',
+        created_by_user: user,
+        message: 'init')
   end
 
   describe 'GET /wiki' do
@@ -37,11 +43,12 @@ RSpec.describe 'Wiki API', type: :request do
     context 'when wiki page exists' do
       it 'returns wiki page with title' do
         request
+
         expect(response).to have_http_status(:ok)
 
         expect(json).to include(
-            'id'        => page.id,
+            'id' => page.id,
-            'title'     => 'spec_wiki_title')
+            'title' => 'spec_wiki_title')
       end
     end
 
@@ -50,6 +57,7 @@ RSpec.describe 'Wiki API', type: :request do
 
       it 'returns 404' do
         request
+
         expect(response).to have_http_status(:not_found)
       end
     end
@@ -99,25 +107,34 @@ RSpec.describe 'Wiki API', type: :request do
         end
             .to change(WikiPage, :count).by(1)
             .and change(WikiRevision, :count).by(1)
+            .and change(WikiVersion, :count).by(1)
 
         expect(response).to have_http_status(:created)
 
         page_id = json.fetch('id')
         expect(json.fetch('title')).to eq('TestPage')
 
-        page = WikiPage.find(page_id)
+        created_page = WikiPage.find(page_id)
-        rev = page.current_revision
+        version = created_page.wiki_versions.order(:version_no).last
+
+        expect(version).to have_attributes(
+          version_no: 1,
+          event_type: 'create',
+          title: 'TestPage',
+          body: "a\nb\nc",
+          created_by_user_id: member.id
+        )
+
+        rev = created_page.current_revision
         expect(rev).to be_present
         expect(rev).to be_content
         expect(rev.message).to eq('init')
 
-        # body が復元できること
+        expect(created_page.body).to eq("a\nb\nc")
-        expect(page.body).to eq("a\nb\nc")
 
-        # 行数とリレーションの整合
         expect(rev.lines_count).to eq(3)
         expect(rev.wiki_revision_lines.order(:position).pluck(:position)).to eq([0, 1, 2])
-        expect(rev.wiki_lines.pluck(:body)).to match_array(%w[a b c])
+        expect(rev.wiki_lines.pluck(:body)).to match_array(['a', 'b', 'c'])
       end
 
       it 'reuses existing WikiLine rows by sha256' do
@@ -135,6 +152,41 @@ RSpec.describe 'Wiki API', type: :request do
         # "a" の WikiLine が増殖しない（1行のはず）
         expect(WikiLine.where(body: 'a').count).to eq(1)
       end
+
+      it 'deduplicates duplicated new lines before upsert' do
+        duplicated = 'duplicated_line_for_wiki_line_upsert_spec'
+
+        post endpoint,
+             params: { title: 'DuplicateNewLine', body: "#{ duplicated }\n#{ duplicated }" },
+             headers: auth_headers(member)
+
+        expect(response).to have_http_status(:created)
+
+        page = WikiPage.find(json.fetch('id'))
+        rev = page.current_revision
+
+        expect(rev.lines_count).to eq(2)
+        expect(WikiLine.where(body: duplicated).count).to eq(1)
+        expect(rev.wiki_revision_lines.count).to eq(2)
+        expect(rev.wiki_revision_lines.pluck(:wiki_line_id).uniq.size).to eq(1)
+      end
+
+      it 'normalises CRLF and strips trailing newlines' do
+        post endpoint,
+             params: { title: 'NormalisedBody', body: "a\r\nb\r\n\r\n", message: 'normalise' },
+             headers: auth_headers(member)
+
+        expect(response).to have_http_status(:created)
+
+        page = WikiPage.find(json.fetch('id'))
+        rev = page.current_revision
+        version = page.wiki_versions.order(:version_no).last
+
+        expect(page.body).to eq("a\nb")
+        expect(version.body).to eq("a\nb")
+        expect(rev.lines_count).to eq(2)
+        expect(rev.wiki_lines.order('wiki_revision_lines.position').map(&:body)).to eq(['a', 'b'])
+      end
     end
   end
 
@@ -146,17 +198,14 @@ RSpec.describe 'Wiki API', type: :request do
       { 'X-Transfer-Code' => user.inheritance_code }
     end
 
-    #let!(:page) { create(:wiki_page, title: 'TestPage') }
+    let!(:test_tag_name) { TagName.create!(name: 'TestPage') }
-    let!(:page) do
-      build(:wiki_page, title: 'TestPage').tap do |p|
-        puts p.errors.full_messages unless p.valid?
-        p.save!
-      end
-    end
 
-    before do
+    let!(:page) do
-      # 初期版を 1 つ作っておく（更新が“2版目”になるように）
+      Wiki::Commit.create_content!(
-      Wiki::Commit.content!(page: page, body: "a\nb", created_user: member, message: 'init')
+          tag_name: test_tag_name,
+          body: "a\nb",
+          created_by_user: member,
+          message: 'init')
     end
 
     context 'when not logged in' do
@@ -182,14 +231,6 @@ RSpec.describe 'Wiki API', type: :request do
             headers: auth_headers(member)
         expect(response).to have_http_status(:unprocessable_entity)
       end
-
-      it 'returns 422 when title mismatched (if you forbid rename here)' do
-        put "/wiki/#{page.id}",
-            params: { title: 'OtherTitle', body: 'x' },
-            headers: auth_headers(member)
-        # 君の controller 例だと title 変更は 422 にしてた
-        expect(response).to have_http_status(:unprocessable_entity)
-      end
     end
 
     context 'when success' do
@@ -200,7 +241,18 @@ RSpec.describe 'Wiki API', type: :request do
           put "/wiki/#{page.id}",
               params: { title: 'TestPage', body: "x\ny", message: 'edit', base_revision_id: current_id },
               headers: auth_headers(member)
-        end.to change(WikiRevision, :count).by(1)
+        end
+            .to change(WikiRevision, :count).by(1)
+            .and change(WikiVersion, :count).by(1)
+
+        version = page.wiki_versions.order(:version_no).last
+
+        expect(version).to have_attributes(
+          event_type: 'update',
+          title: 'TestPage',
+          body: "x\ny",
+          created_by_user_id: member.id
+        )
 
         expect(response).to have_http_status(:ok)
 
@@ -211,25 +263,60 @@ RSpec.describe 'Wiki API', type: :request do
         expect(page.body).to eq("x\ny")
         expect(rev.base_revision_id).to eq(current_id)
       end
+
+      it 'wiki body だけを変更しても tag version は作成しない' do
+        linked_tag_name = TagName.create!(name: 'wiki_body_only_tag')
+        linked_tag = Tag.create!(tag_name: linked_tag_name, category: :general)
+
+        TagVersionRecorder.record!(
+            tag: linked_tag,
+            event_type: :create,
+            created_by_user: member)
+
+        linked_page =
+            Wiki::Commit.create_content!(
+                tag_name: linked_tag_name,
+                body: 'before',
+                created_by_user: member,
+                message: 'init')
+
+        current_id = linked_page.current_revision.id
+        before_count = linked_tag.reload.tag_versions.count
+
+        expect {
+          put "/wiki/#{ linked_page.id }",
+              params: {
+                title: 'wiki_body_only_tag',
+                body: 'after',
+                message: 'edit',
+                base_revision_id: current_id,
+              },
+              headers: auth_headers(member)
+        }
+            .to change(WikiRevision, :count).by(1)
+            .and change(WikiVersion, :count).by(1)
+
+        expect(response).to have_http_status(:ok)
+        expect(linked_tag.reload.tag_versions.count).to eq(before_count)
+      end
     end
 
-    # TODO: コンフリクト未実装のため，実装したらコメント外す．
+    context 'when conflict' do
-    # context 'when conflict' do
+      it 'returns 409 when base_revision_id mismatches' do
-    #   it 'returns 409 when base_revision_id mismatches' do
+        # 先に別ユーザ（同じ member でもOK）が 1 回更新して先頭を進める
-    #     # 先に別ユーザ（同じ member でもOK）が 1 回更新して先頭を進める
+        Wiki::Commit.content!(page: page, body: "zzz", created_user: member, message: 'other edit')
-    #     Wiki::Commit.content!(page: page, body: "zzz", created_user: member, message: 'other edit')
+        page.reload
-    #     page.reload
 
-    #     stale_id = page.wiki_revisions.order(:id).first.id # わざと古い id
+        stale_id = page.wiki_revisions.order(:id).first.id # わざと古い id
-    #     put "/wiki/#{page.id}",
+        put "/wiki/#{page.id}",
-    #         params: { title: 'TestPage', body: 'x', base_revision_id: stale_id },
+            params: { title: 'TestPage', body: 'x', base_revision_id: stale_id },
-    #         headers: auth_headers(member)
+            headers: auth_headers(member)
 
-    #     expect(response).to have_http_status(:conflict)
+        expect(response).to have_http_status(:conflict)
-    #     json = JSON.parse(response.body)
+        json = JSON.parse(response.body)
-    #     expect(json['error']).to eq('conflict')
+        expect(json['error']).to eq('conflict')
-    #   end
+      end
-    # end
+    end
 
     context 'when page not found' do
       it 'returns 404' do
@@ -261,14 +348,17 @@ RSpec.describe 'Wiki API', type: :request do
 
   describe 'GET /wiki/search' do
     before do
-      # 追加で検索ヒット用
+      Wiki::Commit.create_content!(
-      TagName.create!(name: 'spec_wiki_title_2')
+          tag_name: TagName.create!(name: 'spec_wiki_title_2'),
-      WikiPage.create!(tag_name: TagName.find_by!(name: 'spec_wiki_title_2'),
+          body: 'search body 2',
-                       created_user: user, updated_user: user)
+          created_by_user: user,
+          message: 'init')
 
-      TagName.create!(name: 'unrelated_title')
+      Wiki::Commit.create_content!(
-      WikiPage.create!(tag_name: TagName.find_by!(name: 'unrelated_title'),
+          tag_name: TagName.create!(name: 'unrelated_title'),
-                       created_user: user, updated_user: user)
+          body: 'unrelated body',
+          created_by_user: user,
+          message: 'init')
     end
 
     it 'returns up to 20 pages filtered by title like' do
@@ -278,7 +368,9 @@ RSpec.describe 'Wiki API', type: :request do
       expect(json).to be_an(Array)
 
       titles = json.map { |p| p['title'] }
-      expect(titles).to include('spec_wiki_title', 'spec_wiki_title_2')
+
+      expect(titles).to include('spec_wiki_title')
+      expect(titles).to include('spec_wiki_title_2')
       expect(titles).not_to include('unrelated_title')
     end
 
@@ -329,7 +421,12 @@ RSpec.describe 'Wiki API', type: :request do
     it 'returns empty array when page has no revisions and filtered by id' do
       # 別ページを作って revision 無し
       tn2 = TagName.create!(name: 'spec_no_rev')
-      p2 = WikiPage.create!(tag_name: tn2, created_user: user, updated_user: user)
+      # 異常データ: revision 無し WikiPage を直接作る
+      p2 = WikiPage.create!(
+          tag_name: tn2,
+          body: 'init',
+          created_user: user,
+          updated_user: user)
 
       get "/wiki/changes?id=#{p2.id}"
       expect(response).to have_http_status(:ok)
@@ -398,29 +495,68 @@ RSpec.describe 'Wiki API', type: :request do
       expect(json['older_revision_id']).to eq(rev_a.id)
       expect(json['newer_revision_id']).to eq(page.current_revision.id)
     end
+  end
 
-    it 'returns 422 when "to" is redirect revision' do
+  describe 'Wiki::Commit.redirect!' do
-      # redirect revision を作る
+    it 'raises because redirect revisions are deprecated' do
-      tn2 = TagName.create!(name: 'redirect_target')
+      target_tag_name = TagName.create!(name: 'redirect_deprecated_target')
-      target = WikiPage.create!(tag_name: tn2, created_user: user, updated_user: user)
+      target =
+          Wiki::Commit.create_content!(
+              tag_name: target_tag_name,
+              body: 'target',
+              created_by_user: user,
+              message: 'init')
 
-      Wiki::Commit.redirect!(page: page, redirect_page: target, created_user: user, message: 'redir')
+      expect {
-      redirect_rev = page.current_revision
+        Wiki::Commit.redirect!(
-      expect(redirect_rev).to be_redirect
+          page: page,
-
+          redirect_page: target,
-      get "/wiki/#{page.id}/diff?from=#{rev_a.id}&to=#{redirect_rev.id}"
+          created_user: user,
-      expect(response).to have_http_status(:unprocessable_entity)
+          message: 'redirect',
-    end
+          base_revision_id: page.current_revision.id
-
+        )
-    it 'returns 422 when "from" is redirect revision' do
+      }.to raise_error(RuntimeError, '廃止しました．')
-      tn2 = TagName.create!(name: 'redirect_target2')
-      target = WikiPage.create!(tag_name: tn2, created_user: user, updated_user: user)
-
-      Wiki::Commit.redirect!(page: page, redirect_page: target, created_user: user, message: 'redir2')
-      redirect_rev = page.current_revision
-
-      get "/wiki/#{page.id}/diff?from=#{redirect_rev.id}&to=#{rev_b.id}"
-      expect(response).to have_http_status(:unprocessable_entity)
     end
   end
+
+  it 'wiki title を変更すると対応する tag の version を作成する' do
+    linked_tag_name = TagName.create!(name: 'wiki_linked_tag_for_version')
+    linked_tag = Tag.create!(tag_name: linked_tag_name, category: :general)
+
+    linked_page =
+        Wiki::Commit.create_content!(
+            tag_name: linked_tag_name,
+            body: 'before',
+            created_by_user: user,
+            message: 'init')
+
+    current_id = linked_page.current_revision.id
+
+    expect {
+      put "/wiki/#{ linked_page.id }",
+          params: {
+            title: 'wiki_linked_tag_for_version_renamed',
+            body: 'after',
+            message: 'rename',
+            base_revision_id: current_id,
+          },
+          headers: auth_headers(user)
+    }
+        .to change(WikiRevision, :count).by(1)
+        .and change(WikiVersion, :count).by(1)
+        .and change { linked_tag.reload.tag_versions.count }.by(2)
+
+    expect(response).to have_http_status(:ok)
+
+    linked_tag.reload
+    expect(linked_tag.name).to eq('wiki_linked_tag_for_version_renamed')
+
+    versions = linked_tag.tag_versions.order(:version_no)
+
+    expect(versions.first.event_type).to eq('create')
+    expect(versions.first.name).to eq('wiki_linked_tag_for_version')
+
+    expect(versions.second.event_type).to eq('update')
+    expect(versions.second.name).to eq('wiki_linked_tag_for_version_renamed')
+  end
 end

backend/spec/requests/wiki_title_collision_spec.rb

@@ -0,0 +1,62 @@
+require 'rails_helper'
+
+RSpec.describe 'Wiki title collision', type: :request do
+  let!(:user) { create_member_user! }
+
+  def auth_headers user
+    { 'X-Transfer-Code' => user.inheritance_code }
+  end
+
+  def create_wiki_page title:, body:
+    Wiki::Commit.create_content!(
+        tag_name: TagName.create!(name: title),
+        body:,
+        created_by_user: user,
+        message: 'init')
+  end
+
+  it 'returns 422 when renaming wiki title to existing title' do
+    source = create_wiki_page(title: 'wiki_collision_source', body: 'source body')
+    create_wiki_page(title: 'wiki_collision_target', body: 'target body')
+
+    source_revision_count = source.wiki_revisions.count
+    source_version_count = source.wiki_versions.count
+    old_title = source.title
+    old_body = source.body
+
+    put "/wiki/#{ source.id }",
+        params: {
+          title: 'wiki_collision_target',
+          body: 'new body',
+          message: 'rename collision',
+          base_revision_id: source.current_revision.id,
+        },
+        headers: auth_headers(user)
+
+    expect(response).to have_http_status(:unprocessable_entity)
+
+    source.reload
+
+    expect(source.title).to eq(old_title)
+    expect(source.body).to eq(old_body)
+    expect(source.wiki_revisions.count).to eq(source_revision_count)
+    expect(source.wiki_versions.count).to eq(source_version_count)
+  end
+
+  it 'returns 422 when creating wiki with existing title' do
+    create_wiki_page(title: 'wiki_collision_create', body: 'already exists')
+
+    expect {
+      post '/wiki',
+           params: {
+             title: 'wiki_collision_create',
+             body: 'new body',
+             message: 'duplicate create',
+           },
+           headers: auth_headers(user)
+    }
+        .not_to change(WikiPage, :count)
+
+    expect(response).to have_http_status(:unprocessable_entity)
+  end
+end

backend/spec/services/wiki/commit_integrity_spec.rb

@@ -0,0 +1,173 @@
+require 'digest'
+require 'rails_helper'
+
+RSpec.describe Wiki::Commit do
+  let(:user) { create_member_user! }
+
+  def create_page title:, body: 'initial body'
+    described_class.create_content!(
+        tag_name: TagName.create!(name: title),
+        body:,
+        created_by_user: user,
+        message: 'init')
+  end
+
+  describe '.create_content!' do
+    it 'creates page, revision, and version with normalised body' do
+      expect {
+        described_class.create_content!(
+            tag_name: TagName.create!(name: 'commit_integrity_create'),
+            body: "a\r\nb\r\n\r\n",
+            created_by_user: user,
+            message: 'init')
+      }
+          .to change(WikiPage, :count).by(1)
+          .and change(WikiRevision, :count).by(1)
+          .and change(WikiVersion, :count).by(1)
+
+      page = WikiPage.joins(:tag_name).find_by!(tag_names: { name: 'commit_integrity_create' })
+      revision = page.current_revision
+      version = page.wiki_versions.order(:version_no).last
+
+      expect(page.body).to eq("a\nb")
+      expect(revision.lines_count).to eq(2)
+      expect(version.body).to eq("a\nb")
+      expect(version.reason).to eq('init')
+    end
+
+    it 'rejects body that becomes blank after normalisation' do
+      tag_name = TagName.create!(name: 'commit_integrity_blank')
+
+      expect {
+        described_class.create_content!(
+            tag_name:,
+            body: "\r\n\r\n",
+            created_by_user: user,
+            message: 'blank')
+      }
+          .to raise_error(ActiveRecord::RecordInvalid)
+
+      expect(WikiPage.where(tag_name:)).not_to exist
+    end
+  end
+
+  describe '.content!' do
+    it 'updates page body, revision, and version' do
+      page = create_page(title: 'commit_integrity_update', body: 'before')
+      current_id = page.current_revision.id
+
+      expect {
+        described_class.content!(
+            page:,
+            body: 'after',
+            created_user: user,
+            message: 'edit',
+            base_revision_id: current_id)
+      }
+          .to change(WikiRevision, :count).by(1)
+          .and change(WikiVersion, :count).by(1)
+
+      page.reload
+      version = page.wiki_versions.order(:version_no).last
+
+      expect(page.body).to eq('after')
+      expect(version.body).to eq('after')
+      expect(version.reason).to eq('edit')
+    end
+
+    it 'does not record tag_version on body-only wiki update' do
+      tag_name = TagName.create!(name: 'commit_integrity_linked_tag')
+      tag = Tag.create!(tag_name:, category: :general)
+
+      page =
+          described_class.create_content!(
+              tag_name:,
+              body: 'before',
+              created_by_user: user,
+              message: 'init')
+
+      TagVersionRecorder.record!(
+          tag:,
+          event_type: :create,
+          created_by_user: user)
+
+      before_count = tag.reload.tag_versions.count
+
+      described_class.content!(
+          page:,
+          body: 'after',
+          created_user: user,
+          message: 'edit',
+          base_revision_id: page.current_revision.id)
+
+      expect(tag.reload.tag_versions.count).to eq(before_count)
+    end
+
+    it 'raises conflict and leaves page, revision, and version unchanged' do
+      page = create_page(title: 'commit_integrity_conflict', body: 'first')
+      stale_id = page.current_revision.id
+
+      described_class.content!(
+          page:,
+          body: 'second',
+          created_user: user,
+          message: 'second',
+          base_revision_id: stale_id)
+
+      page.reload
+      before_body = page.body
+      before_revision_count = page.wiki_revisions.count
+      before_version_count = page.wiki_versions.count
+
+      expect {
+        described_class.content!(
+            page:,
+            body: 'third',
+            created_user: user,
+            message: 'stale',
+            base_revision_id: stale_id)
+      }
+          .to raise_error(Wiki::Commit::Conflict)
+
+      page.reload
+      expect(page.body).to eq(before_body)
+      expect(page.wiki_revisions.count).to eq(before_revision_count)
+      expect(page.wiki_versions.count).to eq(before_version_count)
+    end
+
+    it 'deduplicates duplicated missing wiki lines' do
+      page = create_page(title: 'commit_integrity_dedup', body: 'before')
+      duplicated = 'commit_integrity_duplicate_line'
+
+      described_class.content!(
+          page:,
+          body: "#{ duplicated }\n#{ duplicated }",
+          created_user: user,
+          message: 'dedup',
+          base_revision_id: page.current_revision.id)
+
+      revision = page.reload.current_revision
+
+      expect(WikiLine.where(body: duplicated).count).to eq(1)
+      expect(revision.wiki_revision_lines.count).to eq(2)
+      expect(revision.wiki_revision_lines.pluck(:wiki_line_id).uniq.size).to eq(1)
+    end
+  end
+
+  describe '.redirect!' do
+    it 'raises because redirect revisions are deprecated' do
+      page = create_page(title: 'commit_integrity_redirect_source', body: 'source')
+      target = create_page(title: 'commit_integrity_redirect_target', body: 'target')
+
+      expect {
+        described_class.redirect!(
+            page:,
+            redirect_page: target,
+            created_user: user,
+            message: 'redirect',
+            base_revision_id: page.current_revision.id)
+      }
+          .to raise_error(RuntimeError, '廃止しました．')
+    end
+  end
+end

backend/spec/services/wiki/commit_spec.rb

@@ -0,0 +1,150 @@
+require 'rails_helper'
+
+RSpec.describe Wiki::Commit do
+  let(:user) { create_member_user! }
+
+  def create_page(title: 'commit_spec_page', body: 'initial body')
+    tag_name = TagName.create!(name: title)
+
+    Wiki::Commit.create_content!(
+        tag_name:,
+        body:,
+        created_by_user: user,
+        message: 'init')
+  end
+
+  describe '.content!' do
+    it 'stores normalised body in wiki_pages and wiki_versions' do
+      page = create_page(title: 'commit_normalised_page')
+
+      described_class.content!(
+        page:,
+        body: "a\r\nb\r\n\r\n",
+        created_user: user,
+        message: 'init'
+      )
+
+      page.reload
+      version = page.wiki_versions.order(:version_no).last
+
+      expect(page.body).to eq("a\nb")
+      expect(version.body).to eq("a\nb")
+      expect(page.current_revision.lines_count).to eq(2)
+    end
+
+    it 'deduplicates duplicated missing wiki lines before upsert' do
+      page = create_page(title: 'commit_duplicate_line_page')
+      duplicated = 'commit_duplicate_line'
+
+      described_class.content!(
+        page:,
+        body: "#{ duplicated }\n#{ duplicated }",
+        created_user: user,
+        message: 'init'
+      )
+
+      page.reload
+
+      expect(WikiLine.where(body: duplicated).count).to eq(1)
+      expect(page.current_revision.lines_count).to eq(2)
+      expect(page.current_revision.wiki_revision_lines.count).to eq(2)
+    end
+
+    it 'raises conflict when base_revision_id is stale' do
+      page = create_page(title: 'commit_conflict_page')
+
+      first = described_class.content!(
+        page:,
+        body: 'first',
+        created_user: user,
+        message: 'first'
+      )
+
+      described_class.content!(
+        page:,
+        body: 'second',
+        created_user: user,
+        message: 'second',
+        base_revision_id: first.id
+      )
+
+      expect {
+        described_class.content!(
+          page:,
+          body: 'third',
+          created_user: user,
+          message: 'third',
+          base_revision_id: first.id
+        )
+      }.to raise_error(Wiki::Commit::Conflict)
+    end
+
+    it 'does not record tag version when corresponding tag has no versions' do
+      tag_name = TagName.create!(name: 'commit_linked_tag_without_versions')
+      tag = Tag.create!(tag_name:, category: :general)
+
+      page =
+          described_class.create_content!(
+              tag_name:,
+              body: 'before',
+              created_by_user: user,
+              message: 'init')
+
+      expect(tag.reload.tag_versions.count).to eq(0)
+
+      current_revision_id = page.current_revision.id
+
+      expect {
+        described_class.content!(
+            page:,
+            body: 'after',
+            created_user: user,
+            message: 'edit',
+            base_revision_id: current_revision_id)
+      }.to change(WikiVersion, :count).by(1)
+
+      expect(tag.reload.tag_versions.count).to eq(0)
+    end
+
+    it 'does not record tag version when corresponding tag has no versions' do
+      tag_name = TagName.create!(name: 'commit_linked_tag_without_versions')
+      tag = Tag.create!(tag_name:, category: :general)
+
+      page =
+          described_class.create_content!(
+              tag_name:,
+              body: 'before',
+              created_by_user: user,
+              message: 'init')
+
+      current_revision_id = page.current_revision.id
+
+      expect {
+        described_class.content!(
+            page:,
+            body: 'after',
+            created_user: user,
+            message: 'edit',
+            base_revision_id: current_revision_id)
+      }.to change(WikiVersion, :count).by(1)
+
+      expect(tag.reload.tag_versions.count).to eq(0)
+    end
+  end
+
+  describe '.redirect!' do
+    it 'raises because redirect revisions are deprecated' do
+      page = create_page(title: 'commit_redirect_source')
+      target = create_page(title: 'commit_redirect_target')
+
+      expect {
+        described_class.redirect!(
+          page:,
+          redirect_page: target,
+          created_user: user,
+          message: 'redirect'
+        )
+      }.to raise_error(RuntimeError, '廃止しました．')
+    end
+  end
+end

backend/spec/services/wiki_version_recorder_spec.rb

@@ -0,0 +1,99 @@
+require 'rails_helper'
+
+RSpec.describe WikiVersionRecorder do
+  let(:user) { create_member_user! }
+
+  def create_page title:, body: 'body'
+    Wiki::Commit.create_content!(
+        tag_name: TagName.create!(name: title),
+        body:,
+        created_by_user: user,
+        message: 'init')
+  end
+
+  describe '.record!' do
+    it 'records title, body, reason, user, and version number' do
+      page = create_page(title: 'wiki_version_recorder_basic', body: 'body')
+
+      expect {
+        described_class.record!(
+            page:,
+            event_type: :update,
+            reason: 'manual reason',
+            created_by_user: user)
+      }
+          .to change { page.reload.wiki_versions.count }.by(1)
+
+      version = page.wiki_versions.order(:version_no).last
+
+      expect(version).to have_attributes(
+        version_no: 2,
+        event_type: 'update',
+        title: 'wiki_version_recorder_basic',
+        body: 'body',
+        reason: 'manual reason',
+        created_by_user_id: user.id
+      )
+    end
+
+    it 'does not create duplicated update version for identical snapshot' do
+      page = create_page(title: 'wiki_version_recorder_duplicate', body: 'body')
+
+      described_class.record!(
+          page:,
+          event_type: :update,
+          reason: nil,
+          created_by_user: user)
+
+      before_count = page.reload.wiki_versions.count
+
+      described_class.record!(
+          page:,
+          event_type: :update,
+          reason: nil,
+          created_by_user: user)
+
+      expect(page.reload.wiki_versions.count).to eq(before_count)
+    end
+
+    it 'creates update version when title changes' do
+      page = create_page(title: 'wiki_version_recorder_title_before', body: 'body')
+      page.tag_name.update!(name: 'wiki_version_recorder_title_after')
+
+      expect {
+        described_class.record!(
+            page:,
+            event_type: :update,
+            reason: 'rename',
+            created_by_user: user)
+      }
+          .to change { page.reload.wiki_versions.count }.by(1)
+
+      version = page.wiki_versions.order(:version_no).last
+
+      expect(version.title).to eq('wiki_version_recorder_title_after')
+      expect(version.body).to eq('body')
+      expect(version.reason).to eq('rename')
+    end
+
+    it 'creates update version when body changes' do
+      page = create_page(title: 'wiki_version_recorder_body', body: 'before')
+      page.update!(body: 'after')
+
+      expect {
+        described_class.record!(
+            page:,
+            event_type: :update,
+            reason: 'body',
+            created_by_user: user)
+      }
+          .to change { page.reload.wiki_versions.count }.by(1)
+
+      version = page.wiki_versions.order(:version_no).last
+
+      expect(version.title).to eq('wiki_version_recorder_body')
+      expect(version.body).to eq('after')
+      expect(version.reason).to eq('body')
+    end
+  end
+end

backend/spec/tasks/nico_export_spec.rb

@@ -0,0 +1,100 @@
+require 'rails_helper'
+require 'rake'
+require 'open3'
+
+RSpec.describe 'nico:export' do
+  let(:task) { Rake::Task['nico:export'] }
+  let(:success_status) { instance_double(Process::Status, success?: true) }
+  let(:failure_status) { instance_double(Process::Status, success?: false) }
+
+  def create_post(url)
+    Post.create!(url:)
+  end
+
+  before(:all) do
+    Rails.application.load_tasks unless Rake::Task.task_defined?('nico:export')
+  end
+
+  before do
+    task.reenable
+
+    allow(ENV).to receive(:fetch).with('MYSQL_USER').and_return('mysql-user')
+    allow(ENV).to receive(:fetch).with('MYSQL_PASS').and_return('mysql-pass')
+    allow(ENV).to receive(:fetch).with('NIZIKA_NICO_PATH').and_return('/srv/nizika-nico')
+  end
+
+  describe 'export' do
+    it 'exports nicovideo ids to shared nico DB' do
+      create_post('https://www.nicovideo.jp/watch/sm12345?ref=foo')
+      create_post('https://www.nicovideo.jp/watch/so67890#comments')
+      create_post('https://www.nicovideo.jp/watch/nm24680')
+      create_post('https://example.com/watch/sm99999')
+
+      expect(Open3).to receive(:capture3) do |env, *args, **kwargs|
+        expect(env).to eq(
+          {
+            'MYSQL_USER' => 'mysql-user',
+            'MYSQL_PASS' => 'mysql-pass',
+          },
+        )
+
+        expect(args.take(3)).to eq(
+          [
+            'python3',
+            '-m',
+            'tracked_videos.put_bulk_upsert',
+          ],
+        )
+
+        expect(args.drop(3)).to contain_exactly(
+          'sm12345',
+          'so67890',
+          'nm24680',
+        )
+
+        expect(kwargs).to eq(chdir: '/srv/nizika-nico')
+
+        ['', '', success_status]
+      end
+
+      task.invoke
+    end
+
+    it 'deduplicates video ids' do
+      create_post('https://www.nicovideo.jp/watch/sm12345')
+      create_post('https://www.nicovideo.jp/watch/sm12345?from=1')
+
+      expect(Open3).to receive(:capture3) do |_env, *args, **_kwargs|
+        expect(args.drop(3)).to eq(['sm12345'])
+
+        ['', '', success_status]
+      end
+
+      task.invoke
+    end
+
+    it 'does not call python when there are no nicovideo posts' do
+      create_post('https://example.com/watch/sm12345')
+
+      expect(Open3).not_to receive(:capture3)
+
+      task.invoke
+    end
+
+    it 'raises stderr when python command fails' do
+      create_post('https://www.nicovideo.jp/watch/sm12345')
+
+      allow(Open3).to receive(:capture3).and_return(
+        [
+          '',
+          'bulk upsert failed',
+          failure_status,
+        ],
+      )
+
+      expect {
+        task.invoke
+      }.to raise_error(RuntimeError, 'bulk upsert failed')
+    end
+  end
+end

backend/spec/tasks/nico_sync_spec.rb

@@ -214,4 +214,108 @@ RSpec.describe "nico:sync" do
     expect(version.event_type).to eq('create')
     expect(version.tags).to eq(snapshot_tags(post.reload))
   end
+
+  it '新規 nico tag に nico tag version を作る' do
+    Tag.bot
+    Tag.tagme
+    Tag.niconico
+    Tag.video
+    Tag.no_deerjikist
+
+    stub_python([{
+      'code' => 'sm9',
+      'title' => 't',
+      'tags' => ['AAA'],
+      'uploaded_at' => '2026-01-01 12:34:56'
+    }])
+
+    allow(URI).to receive(:open).and_return(StringIO.new('<html></html>'))
+
+    expect {
+      run_rake_task('nico:sync')
+    }.to change(NicoTagVersion, :count).by(1)
+
+    nico_tag = Tag.joins(:tag_name).find_by!(tag_names: { name: 'nico:AAA' })
+    version = nico_tag.nico_tag_versions.order(:version_no).last
+
+    expect(version.version_no).to eq(1)
+    expect(version.event_type).to eq('create')
+    expect(version.name).to eq('nico:AAA')
+    expect(version.created_by_user).to be_nil
+  end
+
+  it '既存 post に version が無い場合は create snapshot を補う' do
+    post = Post.create!(
+      title: 'old',
+      url: 'https://www.nicovideo.jp/watch/sm9',
+      uploaded_user: nil
+    )
+
+    kept_general = create_tag!('spec_kept_without_version', category: 'general')
+    PostTag.create!(post: post, tag: kept_general)
+
+    Tag.bot
+    Tag.tagme
+    Tag.no_deerjikist
+
+    stub_python([{
+      'code' => 'sm9',
+      'title' => 'changed title',
+      'tags' => ['AAA'],
+      'uploaded_at' => '2026-01-01 12:34:56'
+    }])
+
+    allow(URI).to receive(:open).and_return(StringIO.new('<html></html>'))
+
+    expect {
+      run_rake_task('nico:sync')
+    }.to change { post.reload.post_versions.count }.by(1)
+
+    versions = post.reload.post_versions.order(:version_no)
+
+    expect(versions.map(&:event_type)).to eq(['create'])
+    expect(versions.first.title).to eq('changed title')
+    expect(versions.first.tags).to eq(snapshot_tags(post.reload))
+  end
+
+  it '既存 version がある post には update version を作る' do
+    post = Post.create!(
+      title: 'old',
+      url: 'https://www.nicovideo.jp/watch/sm9',
+      uploaded_user: nil
+    )
+
+    kept_general = create_tag!('spec_kept_with_version', category: 'general')
+    PostTag.create!(post: post, tag: kept_general)
+
+    PostVersionRecorder.record!(
+      post: post,
+      event_type: :create,
+      created_by_user: nil
+    )
+
+    Tag.bot
+    Tag.tagme
+    Tag.no_deerjikist
+
+    stub_python([{
+      'code' => 'sm9',
+      'title' => 'changed title',
+      'tags' => ['AAA'],
+      'uploaded_at' => '2026-01-01 12:34:56'
+    }])
+
+    allow(URI).to receive(:open).and_return(StringIO.new('<html></html>'))
+
+    expect {
+      run_rake_task('nico:sync')
+    }.to change { post.reload.post_versions.count }.by(1)
+
+    versions = post.reload.post_versions.order(:version_no)
+
+    expect(versions.map(&:event_type)).to eq(['create', 'update'])
+    expect(versions.first.title).to eq('old')
+    expect(versions.second.title).to eq('changed title')
+    expect(versions.second.tags).to eq(snapshot_tags(post.reload))
+  end
 end

frontend/src/App.tsx

@@ -26,6 +26,8 @@ import PostNewPage from '@/pages/posts/PostNewPage'
 import PostSearchPage from '@/pages/posts/PostSearchPage'
 import ServiceUnavailable from '@/pages/ServiceUnavailable'
 import SettingPage from '@/pages/users/SettingPage'
+import TagDetailPage from '@/pages/tags/TagDetailPage'
+import TagHistoryPage from '@/pages/tags/TagHistoryPage'
 import TagListPage from '@/pages/tags/TagListPage'
 import TheatreDetailPage from '@/pages/theatres/TheatreDetailPage'
 import WikiDetailPage from '@/pages/wiki/WikiDetailPage'
@@ -55,7 +57,9 @@ const RouteTransitionWrapper = ({ user, setUser }: {
 	  <Route path="/posts/:id" element={<PostDetailRoute user={user}/>}/>
 	  <Route path="/posts/changes" element={<PostHistoryPage/>}/>
 	  <Route path="/tags" element={<TagListPage/>}/>
+	  <Route path="/tags/:id" element={<TagDetailPage/>}/>
 	  <Route path="/tags/nico" element={<NicoTagListPage user={user}/>}/>
+	  <Route path="/tags/changes" element={<TagHistoryPage/>}/>
 	  <Route path="/theatres/:id" element={<TheatreDetailPage/>}/>
 	  <Route path="/materials" element={<MaterialBasePage/>}>
 	    <Route index element={<MaterialListPage/>}/>

frontend/src/components/TopNav.tsx

@@ -8,7 +8,7 @@ import PrefetchLink from '@/components/PrefetchLink'
 import TopNavUser from '@/components/TopNavUser'
 import { WikiIdBus } from '@/lib/eventBus/WikiIdBus'
 import { tagsKeys, wikiKeys } from '@/lib/queryKeys'
-import { fetchTagByName } from '@/lib/tags'
+import { fetchTag, fetchTagByName } from '@/lib/tags'
 import { cn } from '@/lib/utils'
 import { fetchWikiPage } from '@/lib/wiki'
 
@@ -29,6 +29,8 @@ export const menuOutline = ({ tag, wikiId, user, pathName }: {
   const wikiPageFlg = Boolean (/^\/wiki\/(?!new|changes)[^\/]+/.test (pathName) && wikiId)
   const wikiTitle = pathName.split ('/')[2] ?? ''
 
+  const tagFlg = /^\/tags\/\d+/.test (pathName)
+
   return [
       { name: '広場', to: '/posts', subMenu: [
 	  { name: '一覧', to: '/posts' },
@@ -38,10 +40,15 @@ export const menuOutline = ({ tag, wikiId, user, pathName }: {
 	  { name: 'ヘルプ', to: '/wiki/ヘルプ:広場' }] },
       { name: 'タグ', to: '/tags', subMenu: [
 	  { name: 'マスタ', to: '/tags' },
-	  { name: '別名タグ', to: '/tags/aliases', visible: false },
-	  { name: '上位タグ', to: '/tags/implications', visible: false },
 	  { name: 'ニコニコ連携', to: '/tags/nico' },
-	  { name: 'ヘルプ', to: '/wiki/ヘルプ:タグ' }] },
+	  { name: '履歴', to: '/tags/changes' },
+	  { name: 'ヘルプ', to: '/wiki/ヘルプ:タグ' },
+	  { component: <Separator/>, visible: tagFlg },
+	  { name: `広場 (${ postCount || 0 })`,
+	    to: `/posts?tags=${ encodeURIComponent (tag?.name ?? '') }`,
+	    visible: tagFlg },
+	  { name: '履歴', to: `/tags/changes?id=${ tag?.id }`,
+	    visible: tagFlg && tag?.category !== 'nico' }] },
       { name: '素材', to: '/materials', visible: false, subMenu: [
 	  { name: '一覧', to: '/materials' },
 	  { name: '検索', to: '/materials/search', visible: false }, 
@@ -114,12 +121,14 @@ export default (({ user }: Props) => {
       queryKey: wikiKeys.show (wikiIdStr, { }),
       queryFn: () => fetchWikiPage (wikiIdStr, { }) })
 
-  const effectiveTitle = wikiPage?.title ?? ''
+  const tagFlg = /^\/tags\/\d+/.test (location.pathname)
+  const effectiveTitle = (tagFlg ? location.pathname.split ('/')[2] : wikiPage?.title) ?? ''
 
   const { data: tag } = useQuery ({
       enabled: Boolean (effectiveTitle),
       queryKey: tagsKeys.show (effectiveTitle),
-      queryFn: () => fetchTagByName (effectiveTitle) })
+      queryFn: () => (tagFlg ? fetchTag : fetchTagByName) (effectiveTitle) })
+
 
   const menu = menuOutline ({ tag, wikiId, user, pathName: location.pathname })
   const visibleMenu = menu.filter ((item): item is MenuVisibleItem => item.visible ?? true)

frontend/src/lib/prefetchers.ts

@@ -3,7 +3,7 @@ import { match } from 'path-to-regexp'
 
 import { fetchPost, fetchPosts, fetchPostChanges } from '@/lib/posts'
 import { postsKeys, tagsKeys, wikiKeys } from '@/lib/queryKeys'
-import { fetchTagByName, fetchTag, fetchTags } from '@/lib/tags'
+import { fetchTagByName, fetchTag, fetchTagChanges, fetchTags } from '@/lib/tags'
 import { fetchWikiPage,
 	 fetchWikiPageByTitle,
 	 fetchWikiPages } from '@/lib/wiki'
@@ -14,6 +14,7 @@ type Prefetcher = (qc: QueryClient, url: URL) => Promise<void>
 
 const mPost = match<{ id: string }> ('/posts/:id')
 const mWiki = match<{ title: string }> ('/wiki/:title')
+const mTag = match<{ id: string }> ('/tags/:id')
 
 
 const prefetchWikiPagesIndex: Prefetcher = async (qc, url) => {
@@ -169,6 +170,30 @@ const prefetchTagsIndex: Prefetcher = async (qc, url) => {
 }
 
 
+const prefetchTagShow: Prefetcher = async (qc, url) => {
+  const m = mTag (url.pathname)
+  if (!(m))
+    return
+
+  const { id } = m.params
+
+  await qc.prefetchQuery ({
+      queryKey: tagsKeys.show (id),
+      queryFn:  () => fetchTag (id) })
+}
+
+
+const prefetchTagChanges: Prefetcher = async (qc, url) => {
+  const id = url.searchParams.get ('id')
+  const page = Number (url.searchParams.get ('page') || 1)
+  const limit = Number (url.searchParams.get ('limit') || 20)
+
+  await qc.prefetchQuery ({
+      queryKey: tagsKeys.changes ({ ...(id && { id }), page, limit }),
+      queryFn: () => fetchTagChanges ({ ...(id && { id }), page, limit }) })
+}
+
+
 export const routePrefetchers: { test: (u: URL) => boolean; run: Prefetcher }[] = [
     { test: u => ['/', '/posts', '/posts/search'].includes (u.pathname),
       run: prefetchPostsIndex },
@@ -180,7 +205,11 @@ export const routePrefetchers: { test: (u: URL) => boolean; run: Prefetcher }[]
     { test: u => (!(['/wiki/new', '/wiki/changes'].includes (u.pathname))
 		  && Boolean (mWiki (u.pathname))),
       run: prefetchWikiPageShow },
-    { test: u => u.pathname === '/tags', run: prefetchTagsIndex }]
+    { test: u => u.pathname === '/tags', run: prefetchTagsIndex },
+    { test: u => (!(['/tags/nico', '/tags/changes'].includes (u.pathname))
+		  && Boolean (mTag (u.pathname))),
+      run: prefetchTagShow },
+    { test: u => u.pathname === '/tags/changes', run: prefetchTagChanges }]
 
 
 export const prefetchForURL = async (qc: QueryClient, urlLike: string): Promise<void> => {

frontend/src/lib/queryKeys.ts

@@ -9,9 +9,11 @@ export const postsKeys = {
 		  ['posts', 'changes', p] as const }
 
 export const tagsKeys = {
-    root:   ['tags'] as const,
+    root:     ['tags'] as const,
-    index:  (p: FetchTagsParams) => ['tags', 'index', p] as const,
+    index:    (p: FetchTagsParams) => ['tags', 'index', p] as const,
-    show:   (name: string) => ['tags', name] as const }
+    show:     (name: string) => ['tags', name] as const,
+    changes:  (p: { id?: string; page: number; limit: number }) =>
+		  ['tags', 'changes', p] as const }
 
 export const wikiKeys = {
     root:   ['wiki'] as const,

frontend/src/lib/tags.ts

@@ -1,6 +1,6 @@
 import { apiGet } from '@/lib/api'
 
-import type { FetchTagsParams, Tag } from '@/types'
+import type { FetchTagsParams, Tag, TagVersion } from '@/types'
 
 
 export const fetchTags = async (
@@ -45,3 +45,14 @@ export const fetchTagByName = async (name: string): Promise<Tag | null> => {
     return null
   }
 }
+
+
+export const fetchTagChanges = async (
+    { id, page, limit }: {
+	id?:    string
+	page:   number
+	limit:  number },
+): Promise<{
+    versions: TagVersion[]
+    count:    number }> =>
+	await apiGet ('/tags/versions', { params: { ...(id && { id }), page, limit } })

frontend/src/pages/tags/TagDetailPage.tsx

@@ -0,0 +1,158 @@
+import { useQuery, useQueryClient } from '@tanstack/react-query'
+import { useEffect, useState } from 'react'
+import { useParams } from 'react-router-dom'
+
+import TagLink from '@/components/TagLink'
+import Label from '@/components/common/Label'
+import PageTitle from '@/components/common/PageTitle'
+import MainArea from '@/components/layout/MainArea'
+import { toast } from '@/components/ui/use-toast'
+import { CATEGORIES, CATEGORY_NAMES } from '@/consts'
+import { apiPut } from '@/lib/api'
+import { postsKeys, tagsKeys } from '@/lib/queryKeys'
+import { fetchTag } from '@/lib/tags'
+import { cn } from '@/lib/utils'
+
+import type { FC, FormEvent } from 'react'
+
+import type { Category, Tag } from '@/types'
+
+
+export default (() => {
+  const { id } = useParams ()
+  const tagId = String (id ?? '')
+  const tagKey = tagsKeys.show (tagId)
+
+  const { data: tag, isLoading: loading } = useQuery ({
+      queryKey: tagKey,
+      queryFn: () => fetchTag (tagId) })
+
+  const [name, setName] = useState ('')
+  const [category, setCategory] = useState<Category> ('general')
+  const [aliases, setAliases] = useState ('')
+  const [parentTags, setParentTags] = useState ('')
+  const [disabled, setDisabled] = useState (true)
+
+  const qc = useQueryClient ()
+
+  const handleSubmit = async (e: FormEvent) => {
+    e.preventDefault ()
+
+    const formData = new FormData
+    formData.append ('name', name)
+    formData.append ('category', category)
+    formData.append ('aliases', aliases)
+    formData.append ('parent_tags', parentTags)
+
+    try
+    {
+      const data = await apiPut<Tag> (`/tags/${ id }`, formData)
+
+      setName (data.name)
+      setCategory (data.category as Category)
+      setAliases (data.aliases.join (' '))
+      setParentTags (data.parents.map (t => t.name).join (' '))
+
+      qc.invalidateQueries ({ queryKey: postsKeys.root })
+      qc.invalidateQueries ({ queryKey: tagsKeys.root })
+      toast ({ description: '更新しました．' })
+    }
+    catch
+    {
+      toast ({ description: '更新に失敗しました．' })
+    }
+  }
+
+  useEffect (() => {
+    if (!(tag))
+      {
+	setDisabled (true)
+	return
+      }
+
+    setName (tag.name)
+    setCategory (tag.category as Category)
+    setAliases (tag.aliases.join (' '))
+    setParentTags (tag.parents.map (t => t.name).join (' '))
+    setDisabled (tag.category === 'nico')
+  }, [tag])
+
+  return (
+      <MainArea>
+	{(loading || !(tag)) ? 'Loading...' : (
+	    <div className="max-w-xl">
+	      <PageTitle>
+		<TagLink
+		    tag={tag}
+		    withWiki={false}
+		    withCount={false}/>
+	      </PageTitle>
+
+	      <form onSubmit={handleSubmit} className="my-4 space-y-2">
+		{/* 名称 */}
+		<div>
+		  <Label>名称</Label>
+		  {/* TODO: 補完に対応させる */}
+		  <input
+		      type="text"
+		      disabled={disabled}
+		      value={name}
+		      onChange={e => setName (e.target.value)}
+		      className="w-full border p-2 rounded"/>
+		</div>
+
+		{/* カテゴリ */}
+		<div>
+		  <Label>カテゴリ</Label>
+		  <select
+		      disabled={disabled}
+		      value={category ?? ''}
+		      onChange={e => setCategory(e.target.value as Category)}
+		      className="w-full border p-2 rounded">
+		    {CATEGORIES.filter (cat => tag.category === 'nico' || cat !== 'nico')
+			       .map (cat => (
+			<option key={cat} value={cat}>
+			  {CATEGORY_NAMES[cat]}
+			</option>))}
+		  </select>
+		</div>
+
+		{/* 別名 */}
+		<div>
+		  <Label>別名</Label>
+		  {/* TODO: 補完に対応させる */}
+		  <input
+		      type="text"
+		      disabled={disabled}
+		      value={aliases}
+		      onChange={e => setAliases (e.target.value)}
+		      className="w-full border p-2 rounded"/>
+		</div>
+
+		{/* 上位タグ */}
+		<div>
+		  <Label>上位タグ</Label>
+		  {/* TODO: 補完に対応させる */}
+		  <input
+		      type="text"
+		      disabled={disabled}
+		      value={parentTags}
+		      onChange={e => setParentTags (e.target.value)}
+		      className="w-full border p-2 rounded"/>
+		</div>
+
+		<div className="py-3">
+		  <button
+		      type="submit"
+		      disabled={disabled}
+		      className={cn ('px-4 py-2 rounded',
+				     (disabled
+				      ? 'text-gray-300 bg-gray-500'
+				      : 'text-white bg-blue-500'))}>
+		    更新
+		  </button>
+		</div>
+	      </form>
+	    </div>)}
+      </MainArea>)
+}) satisfies FC

frontend/src/pages/tags/TagHistoryPage.tsx

@@ -0,0 +1,212 @@
+import { useQuery, useQueryClient } from '@tanstack/react-query'
+import { useEffect } from 'react'
+import { Helmet } from 'react-helmet-async'
+import { useLocation } from 'react-router-dom'
+
+import PrefetchLink from '@/components/PrefetchLink'
+import PageTitle from '@/components/common/PageTitle'
+import Pagination from '@/components/common/Pagination'
+import MainArea from '@/components/layout/MainArea'
+import { toast } from '@/components/ui/use-toast'
+import { SITE_TITLE } from '@/config'
+import { CATEGORY_NAMES } from '@/consts'
+import { apiPut } from '@/lib/api'
+import { postsKeys, tagsKeys } from '@/lib/queryKeys'
+import { fetchTagChanges } from '@/lib/tags'
+import { cn, dateString } from '@/lib/utils'
+
+import type { FC } from 'react'
+
+
+const renderDiff = (diff: { current: string | null; prev: string | null }) => (
+    <>
+      {(diff.prev && diff.prev !== diff.current) && (
+	  <>
+	    <del className="text-red-600 dark:text-red-400">
+	      {diff.prev}
+	    </del>
+	    {diff.current && <br/>}
+	  </>)}
+      {diff.current}
+    </>)
+
+
+export default (() => {
+  const location = useLocation ()
+  const query = new URLSearchParams (location.search)
+  const id = query.get ('id')
+  const page = Number (query.get ('page') ?? 1)
+  const limit = Number (query.get ('limit') ?? 20)
+
+  const { data, isLoading: loading } = useQuery ({
+      queryKey: tagsKeys.changes ({ ...(id && { id }), page, limit }),
+      queryFn:  () => fetchTagChanges ({ ...(id && { id }), page, limit }) })
+  const changes = data?.versions ?? []
+  const totalPages = data ? Math.ceil (data.count / limit) : 0
+
+  const qc = useQueryClient ()
+
+  useEffect (() => {
+    document.querySelector ('table')?.scrollIntoView ({ behavior: 'smooth' })
+  }, [location.search])
+
+  return (
+      <MainArea>
+	<Helmet>
+	  <title>{`タグ定義変更履歴 | ${ SITE_TITLE }`}</title>
+	</Helmet>
+
+	<PageTitle>
+	  タグ定義変更履歴
+	  {id && <>: タグ {<PrefetchLink to={`/tags/${ id }`}>#{id}</PrefetchLink>}</>}
+	</PageTitle>
+
+	{loading ? 'Loading...' : (
+	    <>
+	      <div className="overflow-x-auto">
+		<table className="w-full min-w-[1200px] table-fixed border-collapse">
+		  <colgroup>
+		    {/* 版 */}
+		    <col className="w-40"/>
+		    {/* 名称 */}
+		    <col className="w-96"/>
+		    {/* カテゴリ */}
+		    <col className="w-96"/>
+		    {/* 別名 */}
+		    <col className="w-[48rem]"/>
+		    {/* 上位タグ */}
+		    <col className="w-96"/>
+		    {/* 更新日時 */}
+		    <col className="w-64"/>
+		    {/* (差戻ボタン) */}
+		    <col className="w-20"/>
+		  </colgroup>
+
+		  <thead className="border-b-2 border-black dark:border-white">
+		    <tr>
+		      <th className="p-2 text-left">版</th>
+		      <th className="p-2 text-left">名称</th>
+		      <th className="p-2 text-left">カテゴリ</th>
+		      <th className="p-2 text-left">別名</th>
+		      <th className="p-2 text-left">上位タグ</th>
+		      <th className="p-2 text-left">更新日時</th>
+		      <th className="p-2"/>
+		    </tr>
+		  </thead>
+
+		  <tbody>
+		    {changes.map (change => (
+			<tr key={`${ change.tagId }.${ change.versionNo }`}
+			    className={cn ('even:bg-gray-100 dark:even:bg-gray-700')}>
+			  <td className="p-2">{change.tagId}.{change.versionNo}</td>
+			  <td className="p-2 break-all">{renderDiff (change.name)}</td>
+			  <td className="p-2 break-all">
+			    {renderDiff ({
+				current: CATEGORY_NAMES[change.category.current],
+				prev: (change.category.prev
+				       && CATEGORY_NAMES[change.category.prev]) })}
+			  </td>
+			  <td className="p-2">
+			    {change.aliases.map ((tag, i) => (
+				tag.type === 'added'
+				? (
+				    <ins
+					key={i}
+					className="mr-2 text-green-600 dark:text-green-400">
+				      {tag.name}
+				    </ins>)
+				: (
+				    tag.type === 'removed'
+				    ? (
+					<del
+					    key={i}
+					    className="mr-2 text-red-600 dark:text-red-400">
+					  {tag.name}
+					</del>)
+				    : (
+					<span key={i} className="mr-2">
+					  {tag.name}
+					</span>))))}
+			  </td>
+			  <td className="p-2">
+			    {change.parentTags.map ((tag, i) => (
+				tag.type === 'added'
+				? (
+				    <ins
+					key={i}
+					className="mr-2 text-green-600 dark:text-green-400">
+				      {tag.tag.name}
+				    </ins>)
+				: (
+				    tag.type === 'removed'
+				    ? (
+					<del
+					    key={i}
+					    className="mr-2 text-red-600 dark:text-red-400">
+					  {tag.tag.name}
+					</del>)
+				    : (
+					<span key={i} className="mr-2">
+					  {tag.tag.name}
+					</span>))))}
+			  </td>
+			  <td className="p-2">
+			    {change.createdByUser
+			     ? (
+				<PrefetchLink to={`/users/${ change.createdByUser.id }`}>
+				  {change.createdByUser.name
+				   || `名もなきニジラー（#${ change.createdByUser.id }）`}
+				</PrefetchLink>)
+			     : 'bot 操作'}
+			    <br/>
+			    {dateString (change.createdAt)}
+			  </td>
+			  <td className="p-2">
+			    <a
+				href="#"
+				onClick={async e => {
+				  e.preventDefault ()
+
+				  if (!(confirm (
+				      `タグ『${ change.name.current }』を版 ${
+				      change.versionNo } に差戻します．\nよろしいですか?`)))
+				    return
+
+				  try
+				  {
+				    await apiPut (
+					`/tags/${ change.tagId }`,
+					{ name: change.name.current,
+					  category: change.category.current,
+					  aliases:
+					      change.aliases
+					      .filter (t => t.type !== 'removed')
+					      .map (t => t.name)
+					      .join (' '),
+					  parent_tags:
+					      change.parentTags
+					      .filter (t => t.type !== 'removed')
+					      .map (t => t.tag.name)
+					      .join (' ') })
+
+				    qc.invalidateQueries ({ queryKey: postsKeys.root })
+				    qc.invalidateQueries ({ queryKey: tagsKeys.root })
+				    toast ({ description: '差戻しました．' })
+				  }
+				  catch
+				  {
+				    toast ({ description: '差戻に失敗……' })
+				  }
+				}}>
+			      復元
+			    </a>
+			  </td>
+			</tr>))}
+		  </tbody>
+		</table>
+	      </div>
+
+	      <Pagination page={page} totalPages={totalPages}/>
+	    </>)}
+      </MainArea>)
+}) satisfies FC

frontend/src/pages/tags/TagListPage.tsx

@@ -205,13 +205,15 @@ export default (() => {
 	{loading ? 'Loading...' : (results.length > 0 ? (
 	    <div className="mt-4">
 	      <div className="overflow-x-auto">
-		<table className="w-full min-w-[1200px] table-fixed border-collapse">
+		<table className="w-full min-w-[2000px] table-fixed border-collapse">
 		  <colgroup>
 		    <col className="w-72"/>
-		    <col className="w-48"/>
 		    <col className="w-16"/>
-		    <col className="w-44"/>
+		    <col className="w-48"/>
-		    <col className="w-44"/>
+		    <col className="w-72"/>
+		    <col className="w-48"/>
+		    <col className="w-56"/>
+		    <col className="w-56"/>
 		    <col className="w-16"/>
 		  </colgroup>
 
@@ -224,13 +226,6 @@ export default (() => {
 			    currentOrder={order}
 			    defaultDirection={defaultDirection}/>
 		      </th>
-		      <th className="p-2 text-left whitespace-nowrap">
-			<SortHeader<FetchTagsOrderField>
-			    by="category"
-			    label="カテゴリ"
-			    currentOrder={order}
-			    defaultDirection={defaultDirection}/>
-		      </th>
 		      <th className="p-2 text-left whitespace-nowrap">
 			<SortHeader<FetchTagsOrderField>
 			    by="post_count"
@@ -238,6 +233,15 @@ export default (() => {
 			    currentOrder={order}
 			    defaultDirection={defaultDirection}/>
 		      </th>
+		      <th className="p-2 text-left whitespace-nowrap">
+			<SortHeader<FetchTagsOrderField>
+			    by="category"
+			    label="カテゴリ"
+			    currentOrder={order}
+			    defaultDirection={defaultDirection}/>
+		      </th>
+		      <th className="p-2 text-left whitespace-nowrap">別名</th>
+		      <th className="p-2 text-left whitespace-nowrap">上位タグ</th>
 		      <th className="p-2 text-left whitespace-nowrap">
 			<SortHeader<FetchTagsOrderField>
 			    by="created_at"
@@ -260,10 +264,23 @@ export default (() => {
 		    {results.map (row => (
 			<tr key={row.id} className="even:bg-gray-100 dark:even:bg-gray-700">
 			  <td className="p-2">
-			    <TagLink tag={row} withCount={false}/>
+			    <TagLink
+				tag={row}
+				to={`/tags/${ encodeURIComponent (row.id) }`}
+				withCount={false}/>
 			  </td>
-			  <td className="p-2">{CATEGORY_NAMES[row.category]}</td>
 			  <td className="p-2 text-right">{row.postCount}</td>
+			  <td className="p-2">{CATEGORY_NAMES[row.category]}</td>
+			  <td className="p-2">{row.aliases.join (' ')}</td>
+			  <td className="p-2">
+			    {row.parents.map (t => (
+				<span key={t.id} className="mr-2">
+				  <TagLink
+				      tag={t}
+				      withWiki={false}
+				      withCount={false}/>
+				</span>))}
+			  </td>
 			  <td className="p-2">{dateString (row.createdAt)}</td>
 			  <td className="p-2">{dateString (row.updatedAt)}</td>
 			  <td className="p-2">

frontend/src/pages/wiki/WikiDetailPage.tsx

@@ -114,13 +114,15 @@ export default () => {
 		     {...(version && { to: `/wiki/${ encodeURIComponent (title) }` })}/>
 	  </h1>
 	  {loading ? <div>Loading...</div> : <WikiBody title={title} body={wikiPage?.body}/>}
-	</article>
 
-	{(!(version) && posts.length > 0) && (
+	  {(!(version) && posts.length > 0) && (
-	    <TabGroup>
+	      <div className="not-prose">
-	      <Tab name="広場">
+		<TabGroup>
-		<PostList posts={posts}/>
+		  <Tab name="広場">
-	      </Tab>
+		    <PostList posts={posts}/>
-	    </TabGroup>)}
+		  </Tab>
+		</TabGroup>
+	      </div>)}
+	</article>
       </MainArea>)
 }

frontend/src/types.ts

@@ -165,6 +165,8 @@ export type Tag = {
     id:             number
     name:           string
     category:       Category
+    aliases:        string[]
+    parents:        Tag[]
     postCount:      number
     createdAt:      string
     updatedAt:      string
@@ -173,6 +175,17 @@ export type Tag = {
     children?:      Tag[]
     matchedAlias?:  string | null }
 
+export type TagVersion = {
+    tagId:                  number
+    versionNo:              number
+    eventType:              'create' | 'update' | 'discard' | 'restore'
+    name:                   { current: string; prev: string | null }
+    category:               { current: Category; prev: Category | null }
+    aliases:                { name: string; type: 'context' | 'added' | 'removed' }[]
+    parentTags:             { tag: Tag; type: 'context' | 'added' | 'removed' }[]
+    createdAt:              string
+    createdByUser:          { id: number; name: string | null } | null }
+
 export type Theatre = {
     id:             number
     name:           string | null