#434

Reviewed-on: #433
Co-authored-by: miteruzo <miteruzo@naver.com>

AGENTS.md

@@ -573,10 +573,10 @@ and layout reuse, follow `frontend/AGENTS.md`.
 - When new user-facing wording appears necessary, ask the user for the exact
   wording and placement before implementing it.
 - Do not invent replacement copy when removing unrequested wording.
-- Do not create, modify, or run tests unless the user explicitly asks for
-  test work. When the user asks for tests, keep working within the permitted
-  test-file scope and rerun them until they pass or the remaining failure is
-  clearly blocked.
+- 明示的な個別指示がない限り、テストの追加・修正・削除・実行を一切行わない。
+  fixture、mock、snapshot、テスト補助コードも対象とする。
+  既存のテスト差分を勝手に修正・差戻ししない。
+  この規約はディレクトリ固有の自動的なテスト実行推奨より優先する。
 - Test-only work includes adding, updating, deleting, reorganising, or fixing
   SyntaxError in tests. During test-only work, do not modify production code.
 - During test-only work, do not change production constants, behaviour, API
@@ -631,6 +631,19 @@ and layout reuse, follow `frontend/AGENTS.md`.
 
 ## Frontend rules
 
+- 原則として、ユーザ向け UI 文言を TSX / TypeScript に直接記述しない。
+  新しい文言は既存の i18n システムで管理し、適切な既存キーを先に確認する。
+  不必要な重複定義を避け、新規機能固有の文言は適切な namespace にまとめる。
+- 対応 locale の辞書を整合させる。未翻訳項目には既存の日本語 fallback と
+  `_untranslated` 規約を使い、language metadata を維持する。
+  翻訳を捏造せず、未翻訳文字列を正式な翻訳として登録しない。
+- UI 文言の追加・変更時はビルド、静的検査、実画面の確認等で、辞書と
+  SSR / hydration の整合及び翻訳キーの非露出を検証する。
+  i18n の検証を理由にテスト関連作業を開始しない。
+- API の内部識別子、パラメータ、ユーザ入力データ、外部 URL は機械的に
+  翻訳しない。ボタン、項目名、CSV ヘッダ、エラー、空状態、ツールチップ、
+  アクセシビリティ用ラベルも UI 文言として扱う。
+
 - Use `frontend/src/lib/api.ts` for API calls so headers and camelCase conversion stay consistent.
 - Add or reuse TanStack Query keys through `frontend/src/lib/queryKeys.ts`;
   avoid ad hoc query key arrays.

backend/app/controllers/application_controller.rb

@@ -1,22 +1,52 @@
 class ApplicationController < ActionController::API
+  include ActionController::Cookies
+  include ActionController::RequestForgeryProtection
+
+  class UnsupportedLocale < StandardError
+    ;
+  end
+
   rescue_from ActiveRecord::RecordInvalid, with: :render_record_invalid
   rescue_from ActiveRecord::RecordNotUnique, with: :render_record_not_unique
+  rescue_from(UnsupportedLocale) { head :not_found }
 
   before_action :reject_banned_ip_address!
   before_action :authenticate_user
   before_action :reject_banned_user!
+  before_action :validate_explicit_locale!
+  protect_from_forgery with: :exception
+  self.forgery_protection_origin_check = true
+  rescue_from ActionController::InvalidAuthenticityToken, with: :reject_invalid_csrf
+  after_action :prevent_authenticated_caching
 
   def current_user = @current_user
 
   private
 
+  def reject_invalid_csrf
+    response.headers['X-CSRF-Invalid'] = '1'
+    response.headers['Cache-Control'] = 'private, no-store'
+    head :forbidden
+  end
+
   def authenticate_user
-    code = request.headers['X-Transfer-Code'] || request.headers['HTTP_X_TRANSFER_CODE']
+    code = session[:inheritance_code]
     return if code.blank?
 
     @current_user = User.find_by(inheritance_code: code)
   end
 
+  def prevent_authenticated_caching
+    response.headers['Cache-Control'] = 'private, no-store' if current_user
+  end
+
+  def establish_user_session user
+    reset_session
+    session[:inheritance_code] = user.inheritance_code
+    @current_user = user
+    response.headers['Cache-Control'] = 'private, no-store'
+  end
+
   def bool? key, default: false
     return default if params[key].nil?
 
@@ -93,5 +123,21 @@ class ApplicationController < ActionController::API
     value
   end
 
-  def resolve_locale! = Locale.find_by(code: params[:locale]) || Locale.nipponese
+  def resolve_locale!
+    return @resolved_locale if defined?(@resolved_locale)
+
+    code = params.fetch(:locale, 'ja')
+    unless code.is_a?(String) && Locale.codes.value?(code)
+      raise UnsupportedLocale
+    end
+
+    locale = Locale.find_by(code:)
+    raise UnsupportedLocale unless locale && locale.deprecated_at.nil?
+
+    @resolved_locale = locale
+  end
+
+  def validate_explicit_locale!
+    resolve_locale! if params.key?(:locale)
+  end
 end

backend/app/controllers/concerns/counts_listing.rb

@@ -0,0 +1,21 @@
+module CountsListing
+  extend ActiveSupport::Concern
+
+  def index
+    locale = resolve_locale!
+    resource = is_a?(CountsPostsController) ? 'posts' : 'tags'
+    query = CountsQuery.new(version_scope, resource, request.query_parameters.except('locale')
+        .merge('locale' => locale.code))
+    result = { count: query.count, page: query.page, limit: query.limit,
+               at: request.query_parameters['at'].presence || Time.current.utc.iso8601(6) }
+    if query.mode == 'summary'
+      result.merge!(query.summary)
+    else
+      result[:versions] = CountsVersionRepr.many(
+          query.details, resource:, language_code: locale.language_code)
+    end
+    render json: result
+  rescue ArgumentError, TypeError
+    head :bad_request
+  end
+end

backend/app/controllers/counts_exports_controller.rb

@@ -0,0 +1,20 @@
+class CountsExportsController < ApplicationController
+  wrap_parameters false
+
+  def index
+    locale = resolve_locale!
+    exporter = CountsExporter.new(request.request_parameters.merge(request.query_parameters),
+                                  language_code: locale.language_code)
+    response.headers['Content-Type'] = exporter.format == 'json' ?
+        'application/json; charset=utf-8' : 'text/csv; charset=utf-8'
+    response.headers['Content-Disposition'] =
+        "attachment; filename=\"counts-#{ exporter.resource }.#{ exporter.format }\""
+    response.headers['Cache-Control'] = 'private, no-store'
+    response.headers['X-Accel-Buffering'] = 'no'
+    # Rack::ETag otherwise materialises the response to calculate a digest.
+    response.headers['Last-Modified'] = Time.current.httpdate
+    self.response_body = exporter.body
+  rescue ArgumentError, TypeError, JSON::ParserError
+    head :bad_request
+  end
+end

backend/app/controllers/counts_posts_controller.rb

@@ -0,0 +1,3 @@
+class CountsPostsController < PostVersionsController
+  include CountsListing
+end

backend/app/controllers/counts_states_controller.rb

@@ -0,0 +1,10 @@
+class CountsStatesController < ApplicationController
+  def index
+    locale = resolve_locale!
+    result = CountsStateQuery.new(request.query_parameters,
+                                  language_code: locale.language_code).call
+    render json: result
+  rescue ArgumentError, TypeError
+    head :bad_request
+  end
+end

backend/app/controllers/counts_tags_controller.rb

@@ -0,0 +1,3 @@
+class CountsTagsController < TagVersionsController
+  include CountsListing
+end

backend/app/controllers/locales_controller.rb

@@ -0,0 +1,10 @@
+class LocalesController < ApplicationController
+  def index
+    locales = Locale.where(deprecated_at: nil).order(:created_at).map do |locale|
+      { code: locale.code_before_type_cast, name: locale.name }
+    end
+
+    response.headers['Cache-Control'] = 'no-store'
+    render json: { locales: }
+  end
+end

backend/app/controllers/materials_controller.rb

@@ -255,7 +255,8 @@ class MaterialsController < ApplicationController
   end
 
   def resolve_material_tag! locale, tag_name_raw
-    Tag.find_or_create_by_tag_name!(locale, tag_name_raw, category: :material)
+    Tag.find_or_create_by_tag_name!(locale, tag_name_raw, category: :material,
+                                   created_by_user: current_user)
   end
 
   def material_index_needs_tag_name? filters

backend/app/controllers/nico_tags_controller.rb

@@ -24,7 +24,7 @@ class NicoTagsController < ApplicationController
 
     q =
         ExternalTag
-        .joins("LEFT JOIN (#{ post_tag_max_sql }) post_tag_max " \
+        .joins("LEFT JOIN (#{ post_tag_max_sql }) post_tag_max " +
                'ON post_tag_max.external_tag_id = external_tags.id')
         .includes(linked_tags: [:tag_names, :tag_descriptions])
     if name
@@ -37,7 +37,7 @@ class NicoTagsController < ApplicationController
       linked_tag_ids =
           Tag
           .joins(:tag_names)
-          .where(tag_names: { language_code: 'ja', primary_flg: true })
+          .where(tag_names: { language_code: locale.language_code, primary_flg: true })
           .where('tag_names.name LIKE ?', "%#{ linked_tag }%")
           .pluck(:id)
       linked_nico_tag_ids = NicoTagRelation.where(tag_id: linked_tag_ids).pluck(:nico_tag_id)
@@ -45,7 +45,7 @@ class NicoTagsController < ApplicationController
     end
     if link_status.in?(['linked', 'unlinked'])
       exists_sql =
-          'EXISTS (SELECT 1 FROM nico_tag_relations ' \
+          'EXISTS (SELECT 1 FROM nico_tag_relations ' +
           'WHERE nico_tag_relations.nico_tag_id = external_tags.id)'
       q = link_status == 'linked' ? q.where(exists_sql) : q.where("NOT #{ exists_sql }")
     end
@@ -98,7 +98,8 @@ class NicoTagsController < ApplicationController
     ApplicationRecord.transaction do
       linked_tags = Tag.normalise_tags!(locale, linked_tag_names,
                                         with_tagme: false,
-                                        with_no_deerjikist: false)
+                                        with_no_deerjikist: false,
+                                        created_by_user: current_user)
 
       TagVersioning.record_tag_snapshots!(
           linked_tags,
@@ -140,10 +141,23 @@ class NicoTagsController < ApplicationController
   end
 
   def render_nico_tag_form_record_invalid record
-    if record.is_a?(TagName) || record.is_a?(Tag)
-      render_validation_error fields: { tags: record.errors.full_messages.map { |message|
-        "タグ名 “#{ record.name }”: #{ message }"
-      } }
+    names =
+        case record
+        when TagName
+          [record]
+        when Tag
+          record.tag_names.to_a
+        else
+          []
+        end
+    messages = names.flat_map do |tag_name|
+      tag_name.errors.full_messages.map do |message|
+        "タグ名 “#{ tag_name.name }”: #{ message }"
+      end
+    end
+
+    if messages.any?
+      render_validation_error fields: { tags: messages }
     else
       render_validation_error record
     end

backend/app/controllers/post_versions_controller.rb

@@ -1,5 +1,6 @@
 class PostVersionsController < ApplicationController
   def index
+    locale = resolve_locale!
     post_id = params[:post].presence
     tag_id = params[:tag].presence&.to_i
     external_tag_id = params[:external_tag].presence&.to_i
@@ -13,21 +14,7 @@ class PostVersionsController < ApplicationController
 
     offset = (page - 1) * limit
 
-    q = PostVersion.joins(<<~SQL.squish)
-          LEFT JOIN
-            post_versions prev
-            ON
-              prev.post_id = post_versions.post_id
-              AND prev.version_no = post_versions.version_no - 1
-        SQL
-        .select('post_versions.*',
-                'prev.title AS prev_title',
-                'prev.url AS prev_url',
-                'prev.thumbnail_base AS prev_thumbnail_base',
-                'prev.tags_json AS prev_tags_json',
-                'prev.video_ms AS prev_video_ms',
-                'prev.original_created_from AS prev_original_created_from',
-                'prev.original_created_before AS prev_original_created_before')
+    q = version_scope
     q = q.where('post_versions.post_id = ?', post_id) if post_id
     if external_tag_id || (tag_id && !(Tag.exists?(id: tag_id)))
       q = q.where('JSON_CONTAINS(post_versions.tags_json,' +
@@ -45,12 +32,24 @@ class PostVersionsController < ApplicationController
                 .limit(limit)
                 .offset(offset)
 
-    render json: { versions: serialise_versions(versions), count: }
+    render json: { versions: serialise_versions(versions, locale.language_code), count: }
   end
 
   private
 
-  def serialise_versions rows
+  def version_scope
+    PostVersion.with_previous_version
+        .select('post_versions.*',
+                'prev.title AS prev_title',
+                'prev.url AS prev_url',
+                'prev.thumbnail_base AS prev_thumbnail_base',
+                'prev.tags_json AS prev_tags_json',
+                'prev.video_ms AS prev_video_ms',
+                'prev.original_created_from AS prev_original_created_from',
+                'prev.original_created_before AS prev_original_created_before')
+  end
+
+  def serialise_versions rows, language_code
     rows = rows.to_a
     user_ids = rows.map(&:created_by_user_id).compact.uniq
     users_by_id = User.where(id: user_ids).pluck(:id, :name).to_h
@@ -58,12 +57,16 @@ class PostVersionsController < ApplicationController
       [normalise_json(row.tags_json),
        normalise_json(row.attributes['prev_tags_json']) || []]
     }
+    tag_ids = snapshots.flatten.filter_map { _1['tag_id'] }.uniq
+    tag_names = TagName.where(tag_id: tag_ids, language_code:, primary_flg: true)
+                       .pluck(:tag_id, :name).to_h
     external_tag_names = external_tag_names_for(snapshots)
 
     rows.map do |row|
-      cur_tags = snapshot_tag_literals(normalise_json(row.tags_json), external_tag_names)
+      cur_tags = snapshot_tag_literals(
+          normalise_json(row.tags_json), tag_names, external_tag_names)
       prev_tags = snapshot_tag_literals(
-          normalise_json(row.attributes['prev_tags_json']) || [], external_tag_names)
+          normalise_json(row.attributes['prev_tags_json']) || [], tag_names, external_tag_names)
 
       { post_id: row.post_id,
         version_no: row.version_no,
@@ -75,6 +78,7 @@ class PostVersionsController < ApplicationController
                           prev: row.attributes['prev_thumbnail_base'] },
         video_ms: { current: row.video_ms, prev: row.attributes['prev_video_ms'] },
         tags: build_version_tags(cur_tags, prev_tags),
+        parent_post_ids: row.parent_post_ids,
         original_created_from: {
             current: row.original_created_from&.iso8601,
             prev: row.attributes['prev_original_created_from']&.iso8601 },
@@ -106,17 +110,27 @@ class PostVersionsController < ApplicationController
     names
   end
 
-  def snapshot_tag_literals snapshots, external_tag_names
+  def snapshot_tag_literals snapshots, tag_names, external_tag_names
     snapshots
         .filter_map { |snapshot|
           if snapshot.key?('tag_id')
+            sections = snapshot.fetch('sections', []).map { |section|
+              [section.fetch('begin_ms'), section['end_ms']]
+            }.sort_by { |begin_ms, end_ms| [begin_ms, end_ms || Float::INFINITY] }
+            name = tag_names[snapshot['tag_id']] || snapshot.fetch('name')
             [tag_category_order(snapshot['category']),
-             Post.tag_snapshot_literal(snapshot)]
+             { identity: [:tag, snapshot['tag_id'], sections],
+               name: Post.tag_snapshot_literal(snapshot.merge('name' => name)),
+               restore_name: tag_names[snapshot['tag_id']] &&
+                   Post.tag_snapshot_literal(snapshot.merge('name' => name)),
+               external: false }]
           elsif external_tag_names[snapshot['external_tag_id']]
-            [6, external_tag_names[snapshot['external_tag_id']]]
+            [6, { identity: [:external_tag, snapshot['external_tag_id']],
+                  name: external_tag_names[snapshot['external_tag_id']],
+                  restore_name: nil, external: true }]
           end
         }
-        .sort_by { |order, name| [order, name.downcase] }
+        .sort_by { |order, tag| [order, tag[:name].downcase] }
         .map(&:second)
   end
 
@@ -125,17 +139,22 @@ class PostVersionsController < ApplicationController
   end
 
   def build_version_tags cur_tags, prev_tags
-    (cur_tags | prev_tags).map do |name|
+    current = cur_tags.index_by { _1[:identity] }
+    previous = prev_tags.index_by { _1[:identity] }
+
+    (current.keys | previous.keys).map do |identity|
       type =
-          if cur_tags.include?(name) && prev_tags.include?(name)
+          if current.key?(identity) && previous.key?(identity)
             'context'
-          elsif cur_tags.include?(name)
+          elsif current.key?(identity)
             'added'
           else
             'removed'
           end
 
-      { name:, type: }
+      entry = current[identity] || previous[identity]
+      { name: entry[:name], restore_name: entry[:restore_name],
+        external: entry[:external], type: }
     end
   end
 end

backend/app/controllers/posts_controller.rb

@@ -400,8 +400,76 @@ class PostsController < ApplicationController
     render_post_form_record_invalid e.record
   end
 
+  def tag_filters
+    source = resolve_locale!
+    code = params[:target_locale]
+    return head :not_found unless code.is_a?(String) && Locale.codes.value?(code)
+
+    target = Locale.find_by(code:, deprecated_at: nil)
+    return head :not_found unless target
+
+    literals = params[:tags].to_s.split
+    references = tag_filter_references(literals)
+    names = literals.each_with_index.map do |literal, index|
+      reference = references&.[](index)
+      (reference && reference['negative'] == false) ? literal : literal.sub(/\Anot:/i, '')
+    end
+    internal = references ? {} : TagName.where(
+        language_code: source.language_code, name: names).pluck(:name, :tag_id).to_h
+    canonical = references ? {} : TagName.where(
+        language_code: source.language_code, primary_flg: true,
+        tag_id: internal.values).pluck(:tag_id, :name).to_h
+    external_names = names.map { canonical[internal[_1]] || _1 }
+    external = references ? {} : ExternalTag.where(
+        "CONCAT(platform, ':', name) IN (?)", external_names).pluck(
+        Arel.sql("CONCAT(platform, ':', name)"), :id).to_h
+    ids = references ? references.filter_map { _1['tag_id'] } : internal.values
+    translated = TagName.where(language_code: target.language_code,
+                               primary_flg: true, tag_id: ids).pluck(:tag_id, :name).to_h
+
+    filters = literals.each_with_index.map do |literal, index|
+      name = names[index]
+      reference = if references
+                    references[index].except('name')
+                  else
+                    matches = {}
+                    matches['tag_id'] = internal[name] if internal[name]
+                    external_id = external[external_names[index]]
+                    matches['external_tag_id'] = external_id if external_id
+                    matches.empty? ? { 'missing' => true } : matches
+                  end
+      name = translated[reference['tag_id']] || name
+      negative = reference.fetch('negative', literal.downcase.start_with?('not:'))
+      prefix = negative ? literal[/\Anot:/i] || 'not:' : ''
+      reference.merge('name' => "#{ prefix }#{ name }", 'negative' => negative)
+    end
+    render json: { references: filters }
+  end
+
   private
 
+  def tag_filter_references literals
+    raw = params[:tag_refs]
+    return nil if raw.blank?
+
+    references = JSON.parse(raw)
+    valid = references.is_a?(Array) && references.all? do |reference|
+      next false unless reference.is_a?(Hash) && reference['name'].is_a?(String)
+
+      ids = [reference['tag_id'], reference['external_tag_id']].compact
+      ((ids.any? || reference['missing'] == true) &&
+          ids.all? { _1.is_a?(Integer) && _1.positive? } &&
+          (!reference.key?('missing') || (reference['missing'] == true && ids.empty?)) &&
+          (!reference.key?('negative') || [true, false].include?(reference['negative'])))
+    end
+    raise ActionController::BadRequest unless valid
+    return nil unless references.map { _1['name'] } == literals
+
+    references
+  rescue JSON::ParserError, TypeError
+    raise ActionController::BadRequest
+  end
+
   def filtered_posts locale
     tag_names = params[:tags].to_s.split
     match_type = params[:match]
@@ -413,20 +481,29 @@ class PostsController < ApplicationController
   end
 
   def filter_posts_by_tags locale, tag_names, match_type
-    literals = tag_names.map do |raw_name|
-      { name: TagName.canonicalise(locale, raw_name.sub(/\Anot:/i, '')).first,
-        negative: raw_name.downcase.start_with?('not:') }
+    references = tag_filter_references(tag_names)
+    literals = tag_names.each_with_index.map do |raw_name, index|
+      name = raw_name.sub(/\Anot:/i, '')
+      name = TagName.canonicalise(locale, name).first unless references
+      reference = references&.[](index)
+      negative = if reference&.key?('negative')
+                   reference['negative']
+                 else
+                   raw_name.downcase.start_with?('not:')
+                 end
+      { name:, negative:, reference: }
     end
 
     return Post.all if literals.empty?
 
     if match_type == 'any'
       literals.reduce(Post.none) do |posts, literal|
-        posts.or(tag_literal_relation(locale, literal[:name], negative: literal[:negative]))
+        posts.or(tag_literal_relation(locale, literal[:name], negative: literal[:negative],
+                                      reference: literal[:reference]))
       end
     else
       literals.reduce(Post.all) do |posts, literal|
-        ids = tagged_post_ids_for(locale, literal[:name])
+        ids = tagged_post_ids_for(locale, literal[:name], reference: literal[:reference])
         if literal[:negative]
           posts.where.not(id: ids)
         else
@@ -436,8 +513,8 @@ class PostsController < ApplicationController
     end
   end
 
-  def tag_literal_relation locale, name, negative:
-    ids = tagged_post_ids_for(locale, name)
+  def tag_literal_relation locale, name, negative:, reference: nil
+    ids = tagged_post_ids_for(locale, name, reference:)
     if negative
       Post.where.not(id: ids)
     else
@@ -445,7 +522,20 @@ class PostsController < ApplicationController
     end
   end
 
-  def tagged_post_ids_for locale, name
+  def tagged_post_ids_for locale, name, reference: nil
+    if reference
+      matches = Post.none
+      if reference['tag_id']
+        matches = matches.or(Post.where(id: PostTag.where(
+            tag_id: reference['tag_id']).select(:post_id)))
+      end
+      if reference['external_tag_id']
+        matches = matches.or(Post.where(id: PostExternalTag.where(
+            external_tag_id: reference['external_tag_id']).select(:post_id)))
+      end
+      return matches.select(:id)
+    end
+
     posts_by_internal_tags =
         Post
         .joins(tags: :tag_names)
@@ -728,7 +818,8 @@ class PostsController < ApplicationController
                         with_tagme: false,
                         with_no_deerjikist: false,
                         deny_deprecated: true,
-                        with_sections: true) => { tags:, sections: }
+                        with_sections: true,
+                        created_by_user: current_user) => { tags:, sections: }
 
     tags = Tag.expand_parent_tags(tags).reject(&:deprecated?)
     video_ms = normalise_video_ms(tags, video_ms_param:, duration_param:)
@@ -874,7 +965,8 @@ class PostsController < ApplicationController
     Tag.normalise_tags!(locale, snapshot[:tag_names],
                         with_tagme: false,
                         deny_deprecated: true,
-                        with_sections: true) => { tags:, sections: }
+                        with_sections: true,
+                        created_by_user: current_user) => { tags:, sections: }
     TagVersioning.record_tag_snapshots!(tags, created_by_user: current_user,
                                         language_code: locale.language_code)
 

backend/app/controllers/sitemap_entries_controller.rb

@@ -0,0 +1,57 @@
+class SitemapEntriesController < ApplicationController
+  PAGE_SIZE = 1_000
+  RESOURCES = [
+      'posts', 'tags', 'deerjikists', 'materials',
+      'descriptions', 'tag_groups', 'theatres'].freeze
+
+  def index
+    locale = resolve_locale!
+    resources = RESOURCES.map { |resource| { resource:, count: entries(resource, locale).count } }
+    render json: { resources:, page_size: PAGE_SIZE }
+  end
+
+  def show
+    locale = resolve_locale!
+    resource = params[:resource]
+    return head :not_found unless RESOURCES.include?(resource)
+
+    page = Integer(params.fetch(:page, '1'), exception: false)
+    return head :bad_request unless page && page.positive?
+
+    scope = entries(resource, locale)
+    return head :not_found if page > [(scope.count.to_f / PAGE_SIZE).ceil, 1].max
+
+    ids = scope.order(:id).offset((page - 1) * PAGE_SIZE).limit(PAGE_SIZE).pluck(:id)
+    render json: { ids: }
+  end
+
+  private
+
+  def entries resource, locale
+    named_tags = TagName.where(language_code: locale.language_code, primary_flg: true)
+        .select(:tag_id)
+    case resource
+    when 'posts'
+      Post.all
+    when 'tags'
+      Tag.where(id: named_tags)
+    when 'deerjikists'
+      Tag.where(id: named_tags).where(id: Deerjikist.select(:tag_id))
+    when 'materials'
+      Material.all
+    when 'descriptions'
+      TagDescription.where(language_code: locale.language_code, tag_id: named_tags)
+          .where.not(body: [nil, ''])
+          .where(TagDescriptionVersion
+              .where('tag_description_versions.tag_id = tag_descriptions.tag_id')
+              .where('tag_description_versions.language_code = tag_descriptions.language_code')
+              .where('tag_description_versions.version_no = tag_descriptions.version_no')
+              .arel.exists)
+    when 'tag_groups'
+      TagGroup.joins(:versions)
+          .where('tag_group_versions.version_no = tag_groups.version_no')
+    when 'theatres'
+      Theatre.kept
+    end
+  end
+end

backend/app/controllers/tag_versions_controller.rb

@@ -10,17 +10,7 @@ class TagVersionsController < ApplicationController
 
     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.deprecated_at AS prev_deprecated_at',
-              'prev.aliases AS prev_aliases', 'prev.names AS prev_names',
-              'prev.parent_tag_ids AS prev_parent_tag_ids')
+    q = version_scope
     q = q.where('tag_versions.tag_id = ?', tag_id) if tag_id
 
     count = q.except(:select, :order, :limit, :offset).count
@@ -34,9 +24,38 @@ class TagVersionsController < ApplicationController
 
   private
 
+  def version_scope
+    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.deprecated_at AS prev_deprecated_at',
+              'prev.aliases AS prev_aliases', 'prev.names AS prev_names',
+              'prev.parent_tag_ids AS prev_parent_tag_ids')
+  end
+
   def serialise_versions rows, language_code
+    rows = rows.to_a
+    tag_ids = rows.map(&:tag_id).uniq
+    current_names_by_tag_id = TagName.where(tag_id: tag_ids, language_code:, primary_flg: true)
+        .pluck(:tag_id, :name, :auto_generated).to_h do |id, name, automatic|
+      [id, { name:, auto_generated: automatic }]
+    end
     user_ids = rows.map(&:created_by_user_id).compact.uniq
     users_by_id = User.where(id: user_ids).pluck(:id, :name).to_h
+    parent_ids = rows.flat_map do |row|
+      split_parent_tag_ids(row.parent_tag_ids) +
+          split_parent_tag_ids(row.attributes['prev_parent_tag_ids'])
+    end.uniq
+    parents_by_id = Tag.includes(
+        :tag_names, :materials, :deerjikists, :tag_descriptions,
+        parents: [:tag_names, :materials, :deerjikists, :tag_descriptions])
+        .where(id: parent_ids).index_by(&:id)
+    parent_json = parents_by_id.transform_values { TagRepr.base(_1, language_code:) }
 
     rows.map do |row|
       current_names = names_for_locale(row.names, language_code)
@@ -47,18 +66,10 @@ class TagVersionsController < ApplicationController
       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_names, :materials, :tag_descriptions, parents: :tag_descriptions)
-          .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]], language_code:),
+            { tag: parent_json.fetch(h[:tag_id]),
               type: h[:type] }
           end
 
@@ -66,6 +77,8 @@ class TagVersionsController < ApplicationController
         version_no: row.version_no,
         event_type: row.event_type,
         names: row.names,
+        name_changes: name_changes(row.names, row.attributes['prev_names']),
+        current_name_reference: current_names_by_tag_id[row.tag_id],
         name: { current: current_names['name'], prev: previous_names['name'] },
         category: { current: row.category, prev: row.attributes['prev_category'] },
         deprecated_at: { current: row.deprecated_at&.iso8601,
@@ -97,11 +110,44 @@ class TagVersionsController < ApplicationController
   def split_values(values) = values.to_s.split(/\s+/).reject(&:blank?)
 
   def names_for_locale names, language_code
+    values = snapshot_names(names)[language_code]
+    values.is_a?(Hash) ? values : {}
+  end
+
+  def snapshot_names names
     values = names.is_a?(String) ? JSON.parse(names) : names
-    values&.fetch(language_code, {}) || {}
+    values.is_a?(Hash) ? values : {}
   rescue JSON::ParserError
     {}
   end
 
+  def name_changes current_names, previous_names
+    current = snapshot_names(current_names)
+    previous = snapshot_names(previous_names)
+    (current.keys | previous.keys).sort.filter_map do |language|
+      current_name = language_snapshot(current[language])
+      previous_name = language_snapshot(previous[language])
+      next if current_name == previous_name
+
+      { language_code: language, current: current_name, prev: previous_name }
+    end
+  end
+
+  def language_snapshot entry
+    return nil unless entry.is_a?(Hash)
+
+    aliases = Array(entry['aliases']).filter_map do |value|
+      value = { 'name' => value } if value.is_a?(String)
+      next unless value.is_a?(Hash) && value['name'].is_a?(String)
+
+      { name: value['name'], script_code: value['script_code'] }
+    end
+    aliases = aliases.uniq.sort_by { [_1[:name], _1[:script_code].to_s] }
+    { name: entry['name'],
+      script_code: entry['script_code'],
+      auto_generated: entry['auto_generated'],
+      aliases: }
+  end
+
   def split_parent_tag_ids(values) = split_values(values).map(&:to_i)
 end

backend/app/controllers/tags_controller.rb

@@ -175,7 +175,8 @@ class TagsController < ApplicationController
     tags_by_id =
         Tag
         .joins(:tag_names)
-        .includes(:tag_names, :materials, :tag_descriptions, parents: :tag_descriptions)
+        .preload(:tag_names, :materials, :deerjikists, :tag_descriptions,
+                 parents: [:tag_names, :materials, :deerjikists, :tag_descriptions])
         .where(tag_names: { language_code: locale.language_code, primary_flg: true },
                id: tag_ids)
         .index_by(&:id)
@@ -238,7 +239,8 @@ class TagsController < ApplicationController
     base =
         Tag
         .joins(:tag_names)
-        .includes(:tag_names, :materials, :tag_descriptions, parents: :tag_descriptions)
+        .preload(:tag_names, :materials, :deerjikists, :tag_descriptions,
+                 parents: [:tag_names, :materials, :deerjikists, :tag_descriptions])
         .where(tag_names: { language_code: locale.language_code, primary_flg: true },
                deprecated_at: nil)
     base = base.where('tags.post_count > 0') if present_only
@@ -282,7 +284,8 @@ class TagsController < ApplicationController
     tag =
         Tag
         .joins(:tag_names)
-        .includes(:tag_names, :materials, :tag_descriptions, parents: :tag_descriptions)
+        .preload(:tag_names, :materials, :deerjikists, :tag_descriptions,
+                 parents: [:tag_names, :materials, :deerjikists, :tag_descriptions])
         .find_by(id: params[:id],
                  tag_names: { language_code: locale.language_code, primary_flg: true })
     return render json: TagRepr.base(tag, language_code: locale.language_code) if tag
@@ -302,8 +305,9 @@ class TagsController < ApplicationController
     tag =
         Tag
         .joins(:tag_names)
-        .includes(:tag_names, :materials, :tag_descriptions, parents: :tag_descriptions)
-        .find_by(tag_names: { name:, language_code: locale.language_code, primary_flg: true })
+        .preload(:tag_names, :materials, :deerjikists, :tag_descriptions,
+                 parents: [:tag_names, :materials, :deerjikists, :tag_descriptions])
+        .find_by(tag_names: { name:, language_code: locale.language_code })
     return render json: TagRepr.base(tag, language_code: locale.language_code) if tag
 
     platform, external_name = name.split(':', 2)
@@ -320,7 +324,8 @@ class TagsController < ApplicationController
 
     tag = 
         Tag.joins(:tag_names)
-        .includes(:tag_names, :tag_descriptions, parents: :tag_descriptions)
+        .preload(:tag_names, :materials, :deerjikists, :tag_descriptions,
+                 parents: [:tag_names, :materials, :deerjikists, :tag_descriptions])
         .find_by(id: params[:id],
                  tag_names: { language_code: locale.language_code, primary_flg: true })
     return head :not_found unless tag
@@ -340,7 +345,8 @@ class TagsController < ApplicationController
     tag =
         Tag
         .joins(:tag_names)
-        .includes(:tag_names, :tag_descriptions, parents: :tag_descriptions)
+        .preload(:tag_names, :materials, :deerjikists, :tag_descriptions,
+                 parents: [:tag_names, :materials, :deerjikists, :tag_descriptions])
         .find_by(tag_names: { name:, language_code: locale.language_code, primary_flg: true })
     return head :not_found unless tag
 
@@ -359,7 +365,8 @@ class TagsController < ApplicationController
     tag =
         Tag
         .joins(:tag_names)
-        .includes(:tag_names, :tag_descriptions, parents: :tag_descriptions)
+        .preload(:tag_names, :materials, :deerjikists, :tag_descriptions,
+                 parents: [:tag_names, :materials, :deerjikists, :tag_descriptions])
         .find_by(id: params[:id],
                  tag_names: { language_code: locale.language_code, primary_flg: true })
     return head :not_found unless tag
@@ -368,6 +375,7 @@ class TagsController < ApplicationController
     return if performed?
 
     ApplicationRecord.transaction do
+      SharedResourceIdAllocator.lock_space!(Tag, 'tags')
       tag.lock!
 
       requested_keys = rows.map { |row| [row[:platform], row[:code]] }.uniq
@@ -424,7 +432,8 @@ class TagsController < ApplicationController
     tag =
         Tag
         .joins(:tag_names)
-        .includes(:tag_names, :materials, :tag_descriptions, parents: :tag_descriptions)
+        .preload(:tag_names, :materials, :deerjikists, :tag_descriptions,
+                 parents: [:tag_names, :materials, :deerjikists, :tag_descriptions])
         .find_by(tag_names: { name:, language_code: locale.language_code, primary_flg: true })
     return head :not_found unless tag
 
@@ -835,7 +844,8 @@ class TagsController < ApplicationController
   def update_parent_tags! locale, tag, parent_names
     parent_tags = Tag.normalise_tags!(locale, parent_names,
                                       with_tagme: false,
-                                      with_no_deerjikist: false)
+                                      with_no_deerjikist: false,
+                                      created_by_user: current_user)
 
     old_parent_tags = tag.parents.to_a
 

backend/app/controllers/users_controller.rb

@@ -1,39 +1,69 @@
 class UsersController < ApplicationController
   def create
+    if current_user
+      return render json: { code: current_user.inheritance_code,
+                            user: current_user.slice(:id, :name, :inheritance_code, :role) }
+    end
+
     user = nil
     User.transaction do
       user = User.create!(inheritance_code: SecureRandom.uuid, role: :guest)
       attach_ip_address!(user)
     end
 
+    establish_user_session(user)
     render json: { code: user.inheritance_code,
                    user: user.slice(:id, :name, :inheritance_code, :role) },
            status: :created
   end
 
   def verify
-    user = User.find_by(inheritance_code: params[:code])
+    user = if bool?(:restore) && current_user
+             current_user
+           else
+             User.find_by(inheritance_code: params[:code])
+           end
     return render json: { valid: false } unless user
     return head :forbidden if user.banned?
 
     attach_ip_address!(user)
+    establish_user_session(user)
 
     render json: { valid: true, user: user.slice(:id, :name, :inheritance_code, :role) }
   end
 
+  def show_session
+    return head :unauthorized unless current_user
+
+    render json: current_user.slice(:id, :name, :role)
+  end
+
+  def csrf
+    response.headers['Cache-Control'] = 'private, no-store'
+    render json: { token: form_authenticity_token }
+  end
+
+  def destroy_session
+    reset_session
+    response.headers['Cache-Control'] = 'private, no-store'
+    head :no_content
+  end
+
   def renew
     return head :unauthorized unless current_user
 
     user = current_user
     user.inheritance_code = SecureRandom.uuid
     user.save!
+    establish_user_session(user)
     render json: { code: user.inheritance_code }
   end
 
   def me
-    user = User.find_by(inheritance_code: params[:code])
-    return head :not_found unless user
+    user = current_user
+    return head :unauthorized unless user
 
+    attach_ip_address!(user)
     render json: user.slice(:id, :name, :inheritance_code, :role)
   end
 

backend/app/controllers/wiki_pages_controller.rb

@@ -34,11 +34,33 @@ class WikiPagesController < ApplicationController
     render json:
   end
 
+  def autolink_candidates
+    locale = resolve_locale!
+    language = params.fetch(:language, locale.language_code)
+    language = 'ja' if language == 'und'
+    return head :not_found unless language.is_a?(String)
+    return head :not_found unless Language.exists?(code: language)
+
+    names = TagDescription.joins(tag: :tag_names)
+        .where(language_code: locale.language_code, tag_names: { language_code: language })
+        .pluck('tag_descriptions.tag_id', 'tag_descriptions.id', 'tag_names.name')
+    candidates = names.map do |tag_id, description_id, name|
+      WikiPageRepr.autolink_tag(locale, tag_id:, description_id:, name:, language:)
+    end
+    candidates.concat(TagGroup.order(:id).pluck(:id, :name).map do |id, name|
+      WikiPageRepr.autolink_group(locale, id:, name:, language:)
+    end)
+    render json: candidates
+  end
+
   def show
     locale = resolve_locale!
-    tag_description = TagDescription.find_by(id: params[:id], language_code: locale.language_code)
+    reference = TagDescription.find_by(id: params[:id])
+    tag_description = reference && TagDescription.find_by(
+        tag_id: reference.tag_id, language_code: locale.language_code)
 
     return render_wiki_page_by_tag_description locale, tag_description if tag_description
+    return head :not_found if reference
 
     tag_group = TagGroup.find_by(id: params[:id])
     return render_tag_group locale, tag_group if tag_group
@@ -63,6 +85,17 @@ class WikiPagesController < ApplicationController
     head :not_found
   end
 
+  def tag_reference
+    locale = resolve_locale!
+    description = TagDescription.find_by(id: params[:id])
+    return head :not_found unless description
+
+    tag = Tag.preload(:tag_names, :materials, :deerjikists, :tag_descriptions,
+                      parents: [:tag_names, :materials, :deerjikists, :tag_descriptions])
+        .find(description.tag_id)
+    render json: TagRepr.base(tag, language_code: locale.language_code)
+  end
+
   def exists
     locale = resolve_locale!
     if TagDescription.exists?(id: params[:id], language_code: locale.language_code)
@@ -214,6 +247,7 @@ class WikiPagesController < ApplicationController
     base_revision_id = params[:base_revision_id].presence
 
     ApplicationRecord.transaction do
+      SharedResourceIdAllocator.lock_space!(Tag, 'tags')
       tag.lock!
       old_title = tag_name.name
       if title != old_title

backend/app/models/language.rb

@@ -1,5 +1,5 @@
 class Language < ApplicationRecord
   has_many :locales, foreign_key: :language_code, primary_key: :code
 
-  enum :code, ja: 'ja'
+  enum :code, ja: 'ja', ain: 'ain'
 end

backend/app/models/locale.rb

@@ -1,26 +1,38 @@
 class Locale < ApplicationRecord
-  after_create_commit :generate_tag_names!
+  attr_accessor :certified_tag_names_path
+
+  around_save :save_with_tag_names!, if: :will_generate_tag_names?
 
   belongs_to :language, foreign_key: :language_code, primary_key: :code
   belongs_to :script, foreign_key: :script_code, primary_key: :code
 
-  enum :code, ja: 'ja', en: 'en', fr: 'fr'
+  # Enum deserialisation uses the first key for each stored value.
+  # Keep the legacy key for existing predicates, scopes and query arguments.
+  enum :code, { ja: 'ja', 'ain-Kana' => 'ain-Kana', ain_kana: 'ain-Kana' }
+
+  def code= value
+    super(self.class.codes.fetch(value.to_s, value))
+  end
 
   def self.nipponese = Locale.find('ja')
 
   private
 
-  def generate_tag_names!
-    ApplicationRecord.transaction do
-      tag_ids = TagName.where(language_code:, primary_flg: true).pluck(:tag_id)
-      Tag.where.not(id: tag_ids).includes(:tag_names).find_each do
-        TagName.create!(tag_id: _1.id,
-                        language_code:,
-                        name: TagName.generate_name(self, _1, _1.tag_name('ja')),
-                        script_code:,
-                        primary_flg: true,
-                        auto_generated: true)
-      end
+  def will_generate_tag_names?
+    deprecated_at.nil? && (will_save_change_to_code? || will_save_change_to_deprecated_at?)
+  end
+
+  def save_with_tag_names!
+    completed = self.class.transaction(requires_new: true) do
+      SharedResourceIdAllocator.lock_space!(Tag, 'tags')
+      saved = yield
+      raise ActiveRecord::RecordNotSaved, 'Locale save was halted' unless saved
+
+      TagNameCompletion.for_locale!(self)
+      true
+    end
+    unless completed
+      raise ActiveRecord::RecordNotSaved, 'Locale tag completion was rolled back'
     end
   end
 end

backend/app/models/post_version.rb

@@ -1,6 +1,11 @@
 class PostVersion < ApplicationRecord
   include VersionRecord
 
+  scope :with_previous_version, -> {
+    joins('LEFT JOIN post_versions prev ON prev.post_id = post_versions.post_id ' +
+          'AND prev.version_no = post_versions.version_no - 1')
+  }
+
   belongs_to :post
   belongs_to :parent, class_name: 'Post', optional: true
 

backend/app/models/script.rb

@@ -1,5 +1,11 @@
 class Script < ApplicationRecord
   has_many :locales, foreign_key: :script_code, primary_key: :code
 
-  enum :code, Jpan: 'Jpan'
+  # Canonical keys come first so reads and plucks retain ISO 15924 spelling.
+  # Legacy keys preserve the existing enum predicates, scopes and queries.
+  enum :code, { 'Jpan' => 'Jpan', 'Kana' => 'Kana', jpan: 'Jpan', kana: 'Kana' }
+
+  def code= value
+    super(self.class.codes.fetch(value.to_s, value))
+  end
 end

backend/app/models/tag.rb

@@ -110,7 +110,12 @@ class Tag < ApplicationRecord
 
   def has_deerjikists = deerjikists.loaded? ? deerjikists.any? : deerjikists.exists?
 
-  def snapshot_aliases(language_code)
+  def snapshot_aliases language_code
+    if tag_names.loaded?
+      return tag_names.select { _1.language_code == language_code && !_1.primary? }
+          .sort_by(&:name).map(&:name)
+    end
+
     tag_names.where(language_code:, primary_flg: false).order(:name).pluck(:name)
   end
 
@@ -137,7 +142,8 @@ class Tag < ApplicationRecord
                              with_tagme: true,
                              with_no_deerjikist: true,
                              deny_deprecated: false,
-                             with_sections: false
+                             with_sections: false,
+                             created_by_user: nil
       if tag_names.any? { |n| n.downcase.start_with?('nico:') }
         raise NicoTagNormalisationError
       end
@@ -166,7 +172,8 @@ class Tag < ApplicationRecord
 
         name = TagName.canonicalise(locale, name).first
 
-        find_or_create_by_tag_name!(locale, name, category: (cat || :general)).tap do |tag|
+        find_or_create_by_tag_name!(locale, name, category: (cat || :general),
+                                   created_by_user:).tap do |tag|
           if deny_deprecated && tag.deprecated?
             raise DeprecatedTagNormalisationError, [tag.name(locale.language_code)]
           end
@@ -254,25 +261,28 @@ class Tag < ApplicationRecord
       [left_end_ms, right_end_ms].max
     end
 
-    def find_or_create_by_tag_name! locale, name, category:
+    def find_or_create_by_tag_name! locale, name, category:, created_by_user: nil
       language_code = locale.language_code
       name = name.to_s.strip
 
       ApplicationRecord.transaction do
-        tn = TagName.find_by(language_code:, name:)
+        SharedResourceIdAllocator.lock_space!(Tag, 'tags')
+        tn = TagName.lock.find_by(language_code:, name:)
         next tn.tag if tn
 
-        tag = Tag.create!(category:)
-        tn = TagName.create!(tag:, language_code:, name:,
-                             script_code: locale.script_code, primary_flg: true,
-                             auto_generated: false)
-        generate_tag_names!(locale, tag, tn)
+        tag = Tag.new(category:)
+        tag.tag_names.build(language_code:, name:, script_code: locale.script_code,
+                            primary_flg: true, auto_generated: false)
+        TagNameCompletion.for_tag!(tag, created_by_user:)
         tag.association(:tag_names).reset
 
         tag
       end
     rescue ActiveRecord::RecordNotUnique
-      retry
+      existing = TagName.find_by(language_code:, name:)
+      raise unless existing
+
+      existing.tag
     end
 
     def merge_tags! target_tag, source_tags, created_by_user: nil
@@ -352,28 +362,6 @@ class Tag < ApplicationRecord
       total_s * 1_000 + match[:ms].to_s.ljust(3, '0')[0, 3].to_i
     end
 
-    private
-
-    def generate_tag_names! locale, tag, base_tag_name
-      ApplicationRecord.transaction do
-        locales =
-            Locale
-            .where(deprecated_at: nil)
-            .where.not(language_code: locale.language_code)
-            .order(:language_code, :created_at, :script_code)
-            .uniq { _1.language_code }
-        locales.each do |locale|
-          language_code = locale.language_code
-          script_code = locale.script_code
-          TagName.create!(tag_id: tag.id,
-                          language_code:,
-                          name: TagName.generate_name(locale, tag, base_tag_name),
-                          script_code:,
-                          primary_flg: true,
-                          auto_generated: true)
-        end
-      end
-    end
   end
 
   private

backend/app/models/tag_name.rb

@@ -34,9 +34,22 @@ class TagName < ApplicationRecord
   end
 
   def self.generate_name locale, tag, base_tag_name
-    # TODO: 言語ごとの自動命名ロジック完成したら書く．
-
-    "Tag_##{ tag.id }"
+    fallback = "Tag_##{ tag.id }"
+    name =
+        case [locale.language_code, base_tag_name&.language_code]
+        when ['ain', 'ja']
+          TagNameTranscription.ainu(base_tag_name.name)
+        when ['ja', 'ain']
+          base_tag_name.name
+        else
+          return fallback
+        end
+    candidate = new(tag:, name:, language_code: locale.language_code,
+                    script_code: locale.script_code,
+                    primary_flg: true, auto_generated: true)
+    candidate.valid? ? name : fallback
+  rescue TagNameTranscription::Unconvertible
+    fallback
   end
 
   private
@@ -54,6 +67,8 @@ class TagName < ApplicationRecord
   end
 
   def name_must_be_sanitised
+    return if auto_generated && name == "Tag_##{ tag_id }"
+
     if name? && name != TagNameSanitisationRule.sanitise(name)
       errors.add :name, '名前に使用できない文字が含まれてゐます．'
     end

backend/app/representations/counts_version_repr.rb

@@ -0,0 +1,103 @@
+# Counts uses recorded values only; history/diff endpoints retain their own contract.
+class CountsVersionRepr
+  def self.many(rows, resource:, language_code:, at: nil, inclusive: true)
+    new(rows.to_a, resource:, language_code:, at:, inclusive:).serialise
+  end
+
+  def initialize(rows, resource:, language_code:, at:, inclusive:)
+    @rows = rows
+    @at = at
+    @inclusive = inclusive
+    @resource = resource
+    @language = language_code
+    @users = User.where(id: rows.map(&:created_by_user_id).compact).pluck(:id, :name).to_h
+    @languages = master_names(Language)
+    @scripts = master_names(Script)
+    @tag_versions = {}
+    load_tag_versions if resource == 'posts'
+  end
+
+  def serialise
+    @rows.map do |row|
+      resource_id = row.public_send(@resource == 'posts' ? :post_id : :tag_id)
+      common = { id: row.id, resource_id:,
+                 version_no: row.version_no, is_latest: row.attributes['counts_latest'].to_i == 1,
+                 created_at: row.created_at.iso8601,
+                 created_by_user: row.created_by_user_id &&
+                     { id: row.created_by_user_id, name: @users[row.created_by_user_id] } }
+      common.merge(@resource == 'posts' ? post(row) : tag(row))
+    end
+  end
+
+  private
+
+  def master_names(model)
+    model.select('code AS counts_code', :name).to_h do |record|
+      [record.attributes['counts_code'], record.name]
+    end
+  end
+
+  def json(value)
+    value.is_a?(String) ? JSON.parse(value) : value
+  end
+
+  def load_tag_versions
+    pairs = @rows.flat_map { Array(json(_1.tags_json)) }
+        .filter_map { |entry| [entry['tag_id'], entry['version_no']] if entry['tag_id'] }
+        .uniq
+    pairs.each_slice(500) do |batch|
+      placeholders = batch.map { '(?, ?)' }.join(', ')
+      scope = TagVersion.all
+      if @at
+        scope = scope.where("created_at #{ @inclusive ? '<=' : '<' } ?", @at)
+      end
+      scope.where(["(tag_id, version_no) IN (#{ placeholders })", *batch.flatten])
+          .select(:tag_id, :version_no, :name, :category, :names).each do |version|
+        @tag_versions[[version.tag_id, version.version_no]] = version
+      end
+    end
+  end
+
+  def names(value)
+    (json(value) || {}).sort.map do |language, entry|
+      aliases = entry.fetch('aliases', []).map do |alias_entry|
+        alias_entry.merge('script_name' => @scripts[alias_entry['script_code']])
+      end
+      { language_code: language, language_name: @languages[language],
+        script_code: entry['script_code'], script_name: @scripts[entry['script_code']],
+        name: entry['name'], auto_generated: entry['auto_generated'], aliases: }
+    end
+  end
+
+  def post(row)
+    snapshots = Array(json(row.tags_json)).map do |entry|
+      version = @tag_versions[[entry['tag_id'], entry['version_no']]]
+      { id: entry['tag_id'] || entry['external_tag_id'],
+        kind: entry['tag_id'] ? 'internal' : 'external',
+        tag_id: entry['tag_id'], external_tag_id: entry['external_tag_id'],
+        version_no: entry['version_no'], name: entry['name'] || version&.name,
+        category: entry['category'] || version&.category,
+        sections: entry.fetch('sections', []), names: version ? names(version.names) : [] }
+    end
+    { title: row.title, url: row.url, thumbnail_base: row.thumbnail_base,
+      tags: snapshots, parents: row.parent_post_ids.to_s.split.map { { id: _1.to_i } },
+      video_ms: row.video_ms,
+      original_created_from: row.original_created_from&.iso8601,
+      original_created_before: row.original_created_before&.iso8601 }
+  end
+
+  def tag(row)
+    recorded_names = names(row.names)
+    selected = recorded_names.find { _1[:language_code] == @language }
+    aliases = recorded_names.flat_map do |entry|
+      entry[:aliases].map {
+        _1.merge('language_code' => entry[:language_code],
+                 'language_name' => entry[:language_name])
+      }
+    end
+    { name: selected&.fetch(:name) || row.name, names: recorded_names,
+      category: row.category, aliases:,
+      parents: row.parent_tag_ids.to_s.split.map { { id: _1.to_i } },
+      deprecated: row.deprecated_at&.iso8601 }
+  end
+end

backend/app/representations/wiki_page_repr.rb

@@ -9,6 +9,8 @@ module WikiPageRepr
 
     { 'id' => description.id,
       'resource_type' => 'tag_description',
+      'tag_id' => tag.id,
+      'language_code' => description.language_code,
       'tag_name_id' => tag.tag_name(locale.language_code)&.id,
       'body' => description.body,
       'created_user_id' => description.created_by_user_id,
@@ -24,4 +26,24 @@ module WikiPageRepr
   def tag_group tag_group
     TagGroupRepr.tag_group(tag_group).merge('resource_type' => 'tag_group')
   end
+
+  def autolink_tag locale, tag_id:, description_id:, name:, language:
+    { resource_type: 'tag_description',
+      resource_id: description_id,
+      tag_id:,
+      tag_description_id: description_id,
+      name:,
+      language_code: language,
+      locale_code: locale.code_before_type_cast }
+  end
+
+  def autolink_group locale, id:, name:, language:
+    { resource_type: 'tag_group',
+      resource_id: id,
+      tag_id: nil,
+      tag_description_id: nil,
+      name: "#{ TagGroupRepr::PREFIX }#{ name }",
+      language_code: language,
+      locale_code: locale.code_before_type_cast }
+  end
 end

backend/app/services/certified_tag_name_translations.rb

@@ -0,0 +1,105 @@
+require 'json'
+require 'pathname'
+
+
+class CertifiedTagNameTranslations
+  FORMAT = 'btrc-hub.certified-tag-name-translations.v1'.freeze
+
+  class Error < ArgumentError
+    ;
+  end
+
+  def self.load! path, locale:
+    new(path, locale:).load!
+  end
+
+  def initialize path, locale:
+    @path = path
+    @locale = locale
+  end
+
+  def load!
+    document = read_document
+    unless document.is_a?(Hash) && document['format'] == FORMAT
+      fail!('invalid format or version')
+    end
+
+    source_code = document['source_locale']
+    target_code = document['target_locale']
+    unless target_code.is_a?(String) && target_code == Locale.codes.fetch(@locale.code)
+      fail!("target_locale #{ target_code.inspect } does not match the new Locale")
+    end
+    unless source_code.is_a?(String) && Locale.codes.value?(source_code)
+      fail!("invalid source_locale #{ source_code.inspect }")
+    end
+    source_locale = Locale.find_by(code: source_code)
+    fail!("source Locale #{ source_code.inspect } does not exist") unless source_locale
+    fail!('source_locale and target_locale must differ') if source_code == target_code
+
+    entries = validate_entries(document['entries'], source_code, target_code)
+    resolve_tags(entries, source_locale.language_code)
+  end
+
+  private
+
+  def read_document
+    unless (@path.is_a?(String) && !@path.include?("\0") &&
+            Pathname.new(@path).absolute?)
+      fail!('certified_tag_names_path must be an absolute file path')
+    end
+    fail!('JSON file does not exist or is not a regular file') unless File.file?(@path)
+
+    text = File.read(@path, encoding: Encoding::UTF_8)
+    fail!('JSON file is not valid UTF-8') unless text.valid_encoding?
+    JSON.parse(text)
+  rescue JSON::ParserError, SystemCallError, IOError, EncodingError => error
+    fail!("cannot read JSON: #{ error.message }")
+  end
+
+  def validate_entries entries, source_code, target_code
+    fail!('entries must be an array') unless entries.is_a?(Array)
+
+    sources = {}
+    targets = {}
+    entries.each_with_index.map do |entry, index|
+      fail!("entry #{ index + 1 } must be an object") unless entry.is_a?(Hash)
+      source = entry[source_code]
+      target = entry[target_code]
+      unless source.is_a?(String) && source.present? && target.is_a?(String) && target.present?
+        fail!("entry #{ index + 1 }: missing or empty #{ source_code }/#{ target_code } name")
+      end
+      fail!("duplicate source name #{ source.inspect }") if sources.key?(source)
+      fail!("duplicate target name #{ target.inspect }") if targets.key?(target)
+
+      sources[source] = true
+      targets[target] = true
+      [source, target]
+    end
+  end
+
+  def resolve_tags entries, source_language
+    source_names = entries.map(&:first)
+    # SQL may use a case/accent-insensitive collation; the Ruby keys are exact.
+    matches = TagName.where(language_code: source_language, primary_flg: true,
+                            name: source_names).pluck(:name, :tag_id).group_by(&:first)
+    translations = {}
+    entries.each do |source, target|
+      rows = matches.fetch(source, [])
+      next if rows.empty?
+
+      unless rows.length == 1
+        fail!("source primary name #{ source.inspect } must match exactly one tag")
+      end
+      tag_id = rows.first.last
+      if translations.key?(tag_id)
+        fail!("multiple source primary names resolve to Tag##{ tag_id }: #{ source.inspect }")
+      end
+      translations[tag_id] = target
+    end
+    translations
+  end
+
+  def fail! message
+    raise Error, "Certified tag names #{@path.inspect}: #{ message }"
+  end
+end

backend/app/services/counts_export_projection.rb

@@ -0,0 +1,229 @@
+require 'set'
+
+# Export identifiers are stable; UI translations are supplied separately as column labels.
+class CountsExportProjection
+  ROOT_KEYS = { 'resource_id' => 'resource_id', 'version_no' => 'version_no',
+                'is_latest' => 'is_latest', 'thumbnail' => 'thumbnail_url',
+                'thumbnail_base' => 'thumbnail_base', 'title' => 'title', 'url' => 'url',
+                'tags' => 'tags', 'parents' => 'parents', 'video_ms' => 'video_ms',
+                'original_created_at' => 'original_created_at',
+                'original_created_from' => 'original_created_from',
+                'original_created_before' => 'original_created_before',
+                'user' => 'created_by_user', 'created_at' => 'created_at',
+                'name' => 'name', 'names' => 'names', 'category' => 'category',
+                'aliases' => 'aliases', 'deprecated' => 'deprecated' }.freeze
+  CHILD_KEYS = { 'id' => 'id', 'versionNo' => 'version_no', 'kind' => 'kind',
+                 'name' => 'name', 'category' => 'category', 'sections' => 'sections',
+                 'names' => 'names', 'aliases' => 'aliases',
+                 'languageCode' => 'language', 'scriptCode' => 'script',
+                 'autoGenerated' => 'auto_generated' }.freeze
+  NAME_FIELDS = ['languageCode', 'scriptCode', 'name', 'aliases', 'autoGenerated'].freeze
+  CHILDREN = {
+      'tags' => ['id', 'versionNo', 'kind', 'name', 'category', 'sections', 'names'],
+      'names' => NAME_FIELDS,
+      'aliases' => ['languageCode', 'name', 'scriptCode'],
+      'parents' => ['id'] }.freeze
+
+  attr_reader :columns, :headers
+
+  def initialize(params, resource:, summary:, tags:)
+    @params = params
+    @labels = JSON.parse(params.fetch('labels', '{}'))
+    raise ArgumentError unless @labels.is_a?(Hash) && @labels.length <= 100
+    raise ArgumentError unless @labels.all? { |key, value| valid_label?(key, value) }
+    @summary = summary
+    allowed = if summary
+                tags ? ['kind', 'tag_id', 'name', 'deprecated', 'count'] : ['group', 'count']
+              else
+                CountsQuery::COLUMNS.fetch(resource)
+              end
+    @columns = params.fetch('columns', allowed.join(',')).split(',')
+    raise ArgumentError if (@columns - allowed).any? || @columns.uniq != @columns
+
+    @headers = JSON.parse(params.fetch('headers', JSON.generate(@columns)))
+    unless (@headers.is_a?(Array) && @headers.length == @columns.length &&
+        @headers.all? { _1.is_a?(String) && _1.length <= 200 })
+      raise ArgumentError
+    end
+    @order = params.fetch('order', '').split(',')
+    @sorts = params.fetch('child_sort', '').split(',').map do |entry|
+      parts = entry.split(':', -1)
+      raise ArgumentError unless parts.length == 2
+
+      path, direction = parts
+      raise ArgumentError unless ['asc', 'desc'].include?(direction)
+
+      [path, direction]
+    end
+    @selected = params.key?('children') ? params['children'].split(',').to_set : nil
+    valid = CHILDREN.flat_map do |key, fields|
+      paths(fields, key)
+    end
+    raise ArgumentError if @selected && (@selected.to_a - valid).any?
+    allowed_sorts = valid.map do |path|
+      parts = path.split('.')
+      field = parts.pop
+      "#{ parts.join('.') }/#{ field }"
+    end
+    if ((@sorts.map(&:first) - allowed_sorts).any? ||
+        @sorts.map(&:first).uniq.length != @sorts.length)
+      raise ArgumentError
+    end
+  end
+
+  def metadata
+    @columns.each_with_index.map do |key, index|
+      { key: @summary ? key : ROOT_KEYS.fetch(key), label: @headers[index] }
+    end
+  end
+
+  def project(row)
+    @columns.to_h do |key|
+      if @summary
+        value = key == 'group' ? { key: row[:key], name: row[:name] } : row[key.to_sym]
+        [key, value]
+      else
+        value = case key
+                when 'thumbnail' then row[:thumbnail_base]
+                when 'original_created_at'
+                  { from: row[:original_created_from], before: row[:original_created_before] }
+                else row[ROOT_KEYS.fetch(key).to_sym]
+                end
+        value = nested(value || [], CHILDREN.fetch(key), key) if CHILDREN.key?(key)
+        [ROOT_KEYS.fetch(key), value]
+      end
+    end
+  end
+
+  def csv_record(record, row)
+    record.map do |key, value|
+      key == 'group' ? row[:name] || row[:key] : csv_display(value, key)
+    end
+  end
+
+  private
+
+  def valid_label?(key, value)
+    key.is_a?(String) && value.is_a?(String) && key.length <= 100 && value.length <= 300
+  end
+
+  def csv_display(value, key)
+    return value ? @labels.fetch('latest', 'true') : '' if key == 'is_latest'
+    return @labels.fetch("kind:#{ value }", value) if key == 'kind'
+    return @labels.fetch("category:#{ value }", value) if key == 'category'
+    if ['language', 'script'].include?(key) && value.is_a?(Hash)
+      return @labels.fetch("#{ key }:#{ value[:code] }",
+                           value[:name] || @labels.fetch('notRegistered', ''))
+    end
+    return @labels.fetch("boolean:#{ value }", value) if value == true || value == false
+    return value.map { csv_display(_1, key) } if value.is_a?(Array)
+    if value.is_a?(Hash)
+      return value.to_h do |field, item|
+        [@labels.fetch(field.to_s, field), csv_display(item, field.to_s)]
+      end
+    end
+
+    value
+  end
+
+  def fields_for(key)
+    return NAME_FIELDS if key == 'names'
+    return ['name', 'scriptCode'] if key == 'aliases'
+
+    []
+  end
+
+  def paths(fields, prefix)
+    fields.flat_map do |key|
+      path = "#{ prefix }.#{ key }"
+      [path, *paths(fields_for(key), path)]
+    end
+  end
+
+  def fetch(row, key) = row.key?(key) ? row[key] : row[key.to_sym]
+
+  def named_code(row, kind)
+    code = fetch(row, "#{ kind }_code")
+    name = fetch(row, "#{ kind }_name")
+    { code:, name: name.present? && name.to_s.downcase != code.to_s.downcase ? name : nil }
+  end
+
+  def stable(value)
+    case value
+    when Hash
+      value.stringify_keys.sort.to_h.transform_values { stable(_1) }
+    when Array
+      value.map { stable(_1) }
+    else
+      value
+    end
+  end
+
+  def sort_value(row, key)
+    if key == 'languageCode'
+      language = named_code(row, 'language')
+      return @labels.fetch("language:#{ language[:code] }", language[:name])
+    end
+    return named_code(row, 'script')[:name] if key == 'scriptCode'
+
+    fetch(row, CHILD_KEYS.fetch(key))
+  end
+
+  def comparison(left, right)
+    if left.is_a?(Array) && right.is_a?(Array) && left.length != right.length
+      return left.length <=> right.length
+    end
+    return left <=> right if left.is_a?(Numeric) && right.is_a?(Numeric)
+    if [true, false].include?(left) && [true, false].include?(right)
+      return (left ? 1 : 0) <=> (right ? 1 : 0)
+    end
+
+    a = left.is_a?(Hash) || left.is_a?(Array) ? JSON.generate(stable(left)) : left.to_s
+    b = right.is_a?(Hash) || right.is_a?(Array) ? JSON.generate(stable(right)) : right.to_s
+    a <=> b
+  end
+
+  def sorted(rows, prefix, fields)
+    sorts = @sorts.filter_map do |path, direction|
+      parent, key = path.split('/', 2)
+      next unless parent == prefix
+      raise ArgumentError unless fields.include?(key)
+
+      [key, direction]
+    end
+    rows.each_with_index.sort do |(left, a), (right, b)|
+      result = 0
+      sorts.each do |key, direction|
+        first = sort_value(left, key)
+        last = sort_value(right, key)
+        result = if first.nil? || last.nil?
+                   first.nil? == last.nil? ? 0 : (first.nil? ? 1 : -1)
+                 else
+                   comparison(first, last) * (direction == 'asc' ? 1 : -1)
+                 end
+        break unless result.zero?
+      end
+      result.zero? ? a <=> b : result
+    end.map(&:first)
+  end
+
+  def nested(rows, fields, prefix)
+    keys = fields.select { !@selected || @selected.include?("#{ prefix }.#{ _1 }") }
+    ordered = (@order + keys.map { "#{ prefix }.#{ _1 }" }).uniq
+        .filter_map { |path| keys.find { "#{ prefix }.#{ _1 }" == path } }
+    sorted(rows, prefix, fields).map do |row|
+      ordered.to_h do |key|
+        stable = CHILD_KEYS.fetch(key)
+        value = case key
+                when 'languageCode' then named_code(row, 'language')
+                when 'scriptCode' then named_code(row, 'script')
+                else fetch(row, stable)
+                end
+        if fields_for(key).any?
+          value = nested(value || [], fields_for(key), "#{ prefix }.#{ key }")
+        end
+        [stable, value]
+      end
+    end
+  end
+end

backend/app/services/counts_exporter.rb

@@ -0,0 +1,138 @@
+require 'csv'
+
+# One read view and a fixed point for the entire download; only one page is held in memory.
+class CountsExporter
+  EXTRA_KEYS = ['basis', 'format', 'resource', 'headers', 'children', 'order',
+                'summary_columns', 'nested_json', 'child_sort', 'labels'].freeze
+  attr_reader :format, :resource
+
+  def initialize(params, language_code:)
+    allowed = (CountsQuery::KEYS + CountsStateQuery::KEYS + EXTRA_KEYS).uniq
+    raise ArgumentError if (params.keys - allowed).any?
+    raise ArgumentError unless params.values.all? { _1.is_a?(String) }
+
+    @params = params
+    @language = language_code
+    @format = params.fetch('format', 'json')
+    @resource = params.fetch('resource', 'posts')
+    @mode = params.fetch('mode', 'summary')
+    @history = params.fetch('basis', 'state') == 'history'
+    raise ArgumentError unless ['json', 'csv'].include?(format)
+    raise ArgumentError unless ['posts', 'tags'].include?(resource)
+    raise ArgumentError unless ['summary', 'details'].include?(@mode)
+    raise ArgumentError unless ['state', 'history'].include?(params.fetch('basis', 'state'))
+
+    @query_params = params.except(*EXTRA_KEYS, 'columns', 'page', 'limit')
+        .merge('mode' => @mode, 'page' => '1', 'limit' => '100')
+    point = CountsStateQuery.new(@query_params.slice('at').merge('resource' => resource),
+                                 language_code: @language).at
+    @query_params['at'] = point.iso8601(6)
+    @query_params['axis'] ||= !@history && resource == 'posts' ? 'tags' : 'month'
+    @projection = CountsExportProjection.new(params, resource:,
+                                             summary: @mode == 'summary',
+                                             tags: !@history && @query_params['axis'] == 'tags')
+    if @history
+      @query_params.delete('kind')
+      history_query
+    else
+      @query_params.delete('latest')
+      @state_query = CountsStateQuery.new(@query_params.merge('resource' => resource),
+                                          language_code: @language).validate_query!
+    end
+  end
+
+  def body
+    Enumerator.new do |output|
+      ApplicationRecord.transaction(isolation: :repeatable_read) do
+        first_row = true
+        started = false
+        pages do |page|
+          unless started
+            meta = { resource:, mode: @mode, basis: @history ? 'history' : 'state',
+                     at: @query_params['at'], boundary: 'inclusive',
+                     filters: @query_params.except('sort', 'page', 'limit', 'mode'),
+                     sort: export_sort,
+                     child_sort: sort_metadata(@params.fetch('child_sort', '')),
+                     columns: @projection.metadata,
+                     children: @params['children']&.split(','),
+                     field_order: @params.fetch('order', '').split(','), timezone: 'UTC',
+                     count: @mode == 'summary' ? page[:group_count] : page[:count],
+                     totals: page[:totals], coverage: page[:coverage] }
+            output << (format == 'json' ? "{\"metadata\":#{ meta.to_json },\"data\":[" : "\uFEFF")
+            if format == 'csv'
+              output << CSV.generate_line(
+                  @projection.headers.map { csv_value(_1) }, row_sep: "\r\n")
+            end
+            started = true
+          end
+          (page[:versions] || page[:state_rows] || page[:groups] || []).each do |row|
+            record = @projection.project(row)
+            if format == 'json'
+              output << ',' unless first_row
+              output << record.to_json
+            else
+              values = @projection.csv_record(record, row).map { csv_value(_1) }
+              output << CSV.generate_line(values, row_sep: "\r\n")
+            end
+            first_row = false
+          end
+        end
+        output << ']}' if format == 'json'
+      end
+    end
+  end
+
+  private
+
+  def export_sort
+    sort_metadata(@query_params.fetch('sort', default_sort))
+  end
+
+  def sort_metadata(value)
+    value.split(',').map do |entry|
+      key, direction = entry.split(':', 2)
+      { key:, direction: }
+    end
+  end
+
+  def default_sort
+    return 'created_at:desc' if @mode == 'details'
+
+    !@history && @query_params['axis'] == 'tags' ? 'count:desc' : 'group:asc'
+  end
+
+  def history_query
+    scope = resource == 'posts' ? PostVersion.with_previous_version : TagVersion.all
+    CountsQuery.new(scope, resource, @query_params)
+  end
+
+  def pages
+    unless @history
+      @state_query.each_page { yield _1 }
+      return
+    end
+    query = history_query
+    total = @mode == 'summary' ? nil : query.count
+    loop do
+      result = if @mode == 'summary'
+                 query.summary(include_count: @query_params['page'] == '1')
+               else
+                 { count: total,
+                   versions: CountsVersionRepr.many(query.details, resource:,
+                                                   language_code: @language,
+                                                   at: Time.iso8601(@query_params['at'])) }
+               end
+      total ||= result[:group_count]
+      yield result
+      break if @query_params['page'].to_i * 100 >= total
+
+      @query_params['page'] = (@query_params['page'].to_i + 1).to_s
+      query = history_query
+    end
+  end
+
+  def csv_value(value)
+    text = value.is_a?(Hash) || value.is_a?(Array) ? JSON.generate(value) : value.to_s
+    text.match?(/\A\s*[=+@-]/) ? "'#{ text }" : text
+  end
+end

backend/app/services/counts_query.rb

@@ -0,0 +1,208 @@
+# Read-only history queries. SQL identifiers and expressions are server-owned.
+class CountsQuery
+  AXES = ['month', 'user'].freeze
+  COMMON_COLUMNS = ['resource_id', 'version_no', 'is_latest', 'user', 'created_at'].freeze
+  COLUMNS = {
+      'posts' => COMMON_COLUMNS + [
+          'thumbnail', 'thumbnail_base', 'title', 'url', 'tags', 'parents', 'video_ms',
+          'original_created_at', 'original_created_from', 'original_created_before'],
+      'tags' => COMMON_COLUMNS + [
+          'name', 'names', 'category', 'aliases', 'parents', 'deprecated'] }.freeze
+  KEYS = [
+      'locale', 'mode', 'axis', 'page', 'limit', 'from', 'before', 'latest',
+      'user_id', 'resource_id', 'tag', 'columns', 'sort', 'at'].freeze
+
+  attr_reader :page, :limit, :mode, :axis
+
+  def initialize(scope, resource, params, latest_expression: nil)
+    @table = scope.klass.table_name
+    @resource = resource
+    @id_column = resource == 'posts' ? 'post_id' : 'tag_id'
+    @params = params
+    @latest_expression = latest_expression
+    @scope = scope.except(:select, :order).joins(
+        "LEFT JOIN users counts_actor ON counts_actor.id = #{ @table }.created_by_user_id")
+    raise ArgumentError unless (params.keys - KEYS).empty?
+    raise ArgumentError unless params.values.all? { _1.is_a?(String) }
+
+    @mode = params.fetch('mode', 'summary')
+    @axis = params.fetch('axis', 'month')
+    raise ArgumentError unless ['summary', 'details'].include?(mode) && AXES.include?(axis)
+
+    @page = integer('page', 1)
+    @limit = integer('limit', 20)
+    raise ArgumentError if limit > 100 || page > 1_000_000
+
+    columns = params.fetch('columns', COLUMNS.fetch(resource).join(',')).split(',')
+    if columns.empty? || columns.uniq != columns || (columns - COLUMNS.fetch(resource)).any?
+      raise ArgumentError
+    end
+    @sort = parse_sort
+    apply_filters
+  end
+
+  def relation = @scope
+
+  def count = @scope.count
+
+  def latest_expression
+    return @latest_expression if @latest_expression
+
+    at = timestamp('at')
+    cutoff = at ? "AND newer.created_at <= #{ @scope.klass.connection.quote(at) }" : ''
+    <<~SQL.squish
+      NOT EXISTS (SELECT 1 FROM #{ @table } newer
+        WHERE newer.#{ @id_column } = #{ @table }.#{ @id_column }
+          AND newer.version_no > #{ @table }.version_no #{ cutoff })
+    SQL
+  end
+
+  def details
+    @scope.select("#{ @table }.*", Arel.sql("(#{ latest_expression }) AS counts_latest"))
+        .order(Arel.sql(order_sql(detail_expressions, ["#{ @table }.id DESC"])))
+        .limit(limit).offset((page - 1) * limit)
+  end
+
+  def summary(include_count: true)
+    expression = axis == 'month' ? "DATE_FORMAT(#{ @table }.created_at, '%Y-%m')" :
+                                  "#{ @table }.created_by_user_id"
+    group_order = axis == 'user' ? 'MAX(counts_actor.name)' : expression
+    sql = @scope.group(Arel.sql(expression)).select(Arel.sql(
+        "#{ expression } AS group_key, COUNT(*) AS record_count, " +
+        "#{ group_order } AS group_name")).to_sql
+    connection = @scope.klass.connection
+    source = "FROM (#{ sql }) counts_groups"
+    groups = include_count ? connection.select_value("SELECT COUNT(*) #{ source }") : nil
+    expressions = { 'group' => ['group_name'], 'count' => ['record_count'] }
+    order = order_sql(expressions, ['group_key IS NULL ASC', 'group_key ASC'])
+    rows = connection.select_all(
+        "SELECT group_key, group_name, record_count #{ source } " +
+        "ORDER BY #{ order } LIMIT #{ limit } OFFSET #{ (page - 1) * limit }")
+    { group_count: groups&.to_i,
+      groups: rows.map do |row|
+        { key: row['group_key'],
+          name: axis == 'user' ? row['group_name'] : nil,
+          count: row['record_count'].to_i }
+      end }
+  end
+
+  private
+
+  def parse_sort
+    value = @params.fetch('sort', mode == 'details' ? 'created_at:desc' : 'group:asc')
+    return [] if value.empty?
+
+    values = value.split(',', -1).map { _1.split(':', -1) }
+    allowed = mode == 'details' ? COLUMNS.fetch(@resource) - ['thumbnail'] : ['group', 'count']
+    invalid = values.any? do |key, direction, *extra|
+      extra.any? || !allowed.include?(key) || !['asc', 'desc'].include?(direction)
+    end
+    if (values.empty? || values.length > allowed.length || invalid ||
+        values.map(&:first).uniq.length != values.length)
+      raise ArgumentError
+    end
+    values
+  end
+
+  # NULL always sorts last, including descending keys. The final key is unique.
+  def order_sql(expressions, final)
+    (@sort.flat_map do |key, direction|
+      expressions.fetch(key).flat_map do |expression|
+        ["(#{ expression }) IS NULL ASC", "#{ expression } #{ direction.upcase }"]
+      end
+    end + final).join(', ')
+  end
+
+  def detail_expressions
+    common = { 'resource_id' => ["#{ @table }.#{ @id_column }"],
+               'version_no' => ["#{ @table }.version_no"],
+               'is_latest' => ["(#{ latest_expression })"],
+               'user' => ['counts_actor.name', "#{ @table }.created_by_user_id"],
+               'created_at' => ["#{ @table }.created_at"] }
+    if @resource == 'posts'
+      fields = [
+          'title', 'url', 'thumbnail_base', 'video_ms',
+          'original_created_from', 'original_created_before']
+      common.merge(fields.to_h { [_1, ["#{ @table }.#{ _1 }"]] }).merge(
+          'original_created_at' => [
+              'post_versions.original_created_from', 'post_versions.original_created_before'],
+          'tags' => json_order('post_versions.tags_json'),
+          'parents' => list_order('post_versions.parent_post_ids'))
+    else
+      name = "JSON_UNQUOTE(JSON_EXTRACT(tag_versions.names, #{ locale_name_path }))"
+      common.merge(
+          'name' => ["COALESCE(#{ name }, tag_versions.name)"],
+          'names' => json_order('tag_versions.names'),
+          'category' => ['tag_versions.category'],
+          'aliases' => json_order(
+              "JSON_EXTRACT(tag_versions.names, '$.*.aliases[*]')"),
+          'parents' => list_order('tag_versions.parent_tag_ids'),
+          'deprecated' => ['tag_versions.deprecated_at'])
+    end
+  end
+
+  def locale_name_path
+    language = Locale.find_by(code: @params.fetch('locale', 'ja'))&.language_code || 'ja'
+    path = "$.#{ JSON.generate(language) }.name"
+    @scope.klass.connection.quote(path)
+  end
+
+  # Multi-valued parent cells sort by cardinality, then binary snapshot text.
+  def json_order(column)
+    [
+        "COALESCE(JSON_LENGTH(#{ column }), 0)",
+        "COALESCE(CAST(#{ column } AS CHAR), '[]') COLLATE utf8mb4_bin"]
+  end
+
+  def list_order(column)
+    [
+        "CASE WHEN #{ column } = '' THEN 0 ELSE " +
+            "1 + LENGTH(#{ column }) - LENGTH(REPLACE(#{ column }, ' ', '')) END",
+        "#{ column } COLLATE utf8mb4_bin"]
+  end
+
+  def integer(key, default = nil)
+    value = @params[key].presence
+    return default if value.nil? && !default.nil?
+    raise ArgumentError unless value&.match?(/\A[1-9][0-9]{0,9}\z/)
+
+    value.to_i
+  end
+
+  def timestamp(key)
+    value = @params[key].presence
+    return nil unless value
+    pattern = /\A\d{4}-\d{2}-\d{2}T\d{2}:\d{2}(?::\d{2}(?:\.\d{1,6})?)?Z\z/
+    raise ArgumentError unless value.match?(pattern)
+
+    Date.iso8601(value.first(10))
+    Time.iso8601(value.length == 17 ? value.sub(/Z\z/, ':00Z') : value)
+  end
+
+  def apply_filters
+    at = timestamp('at')
+    first = timestamp('from')
+    last = timestamp('before')
+    raise ArgumentError if first && last && first >= last
+    raise ArgumentError unless ['0', '1'].include?(@params.fetch('latest', '1'))
+
+    @scope = @scope.where("#{ @table }.created_at <= ?", at) if at
+    @scope = @scope.where(Arel.sql(latest_expression)) unless @params['latest'] == '0'
+    @scope = @scope.where("#{ @table }.created_at >= ?", first) if first
+    @scope = @scope.where("#{ @table }.created_at < ?", last) if last
+    if @params['resource_id'].present?
+      @scope = @scope.where(@table => { @id_column => integer('resource_id') })
+    end
+    if @params['user_id'].present?
+      user = @params['user_id'] == 'none' ? nil : integer('user_id')
+      @scope = @scope.where(@table => { created_by_user_id: user })
+    end
+    return unless @params['tag'].present?
+    raise ArgumentError unless @resource == 'posts'
+
+    id = integer('tag')
+    @scope = @scope.where(
+        "JSON_CONTAINS(post_versions.tags_json, JSON_OBJECT('tag_id', CAST(? AS UNSIGNED))) OR " +
+        "JSON_CONTAINS(prev.tags_json, JSON_OBJECT('tag_id', CAST(? AS UNSIGNED)))", id, id)
+  end
+end

backend/app/services/counts_state_query.rb

@@ -0,0 +1,366 @@
+# Restores one recorded version per resource before applying record filters.
+class CountsStateQuery
+  KEYS = ['locale', 'resource', 'mode', 'at', 'from', 'before', 'grain',
+          'kind', 'tag', 'page', 'limit', 'sort', 'axis', 'user_id', 'resource_id'].freeze
+  MAX_PERIODS = 366
+
+  attr_reader :at
+
+  def initialize(params, language_code:)
+    raise ArgumentError unless (params.keys - KEYS).empty?
+    raise ArgumentError unless params.values.all? { _1.is_a?(String) }
+
+    @params = params
+    @connection = ApplicationRecord.connection
+    @language = language_code
+    @resource = params.fetch('resource', 'posts')
+    @mode = params.fetch('mode', 'summary')
+    @inclusive = ['summary', 'details'].include?(@mode)
+    @axis = params.fetch('axis', @resource == 'posts' ? 'tags' : 'month')
+    @kind = params.fetch('kind', 'internal')
+    @grain = params.fetch('grain', 'month')
+    raise ArgumentError unless ['posts', 'tags'].include?(@resource)
+    raise ArgumentError unless ['summary', 'details', 'state', 'trend', 'snapshot'].include?(@mode)
+    raise ArgumentError unless ['internal', 'external', 'all'].include?(@kind)
+    raise ArgumentError unless ['day', 'month', 'year'].include?(@grain)
+
+    raise ArgumentError unless ['tags', 'month', 'user'].include?(@axis)
+    if @mode == 'summary' && @axis == 'tags' && @resource != 'posts'
+      raise ArgumentError
+    end
+
+    @page = integer('page', 1)
+    @limit = integer('limit', 20)
+    @tag = integer('tag') if params['tag'].present?
+    raise ArgumentError if @limit > 100 || @page > 1_000_000
+    raise ArgumentError if @tag && @kind == 'all'
+    raise ArgumentError if @mode == 'trend' && !@tag
+
+    @now = Time.current.utc
+    @at = timestamp('at') || @now
+    raise ArgumentError if @at > @now
+  end
+
+  def call(metadata: true)
+    @metadata = metadata
+    # Keep totals, rows, and detail pages on one repeatable-read database snapshot.
+    ApplicationRecord.transaction do
+      unless @history_loaded
+        @post_start = PostVersion.minimum(:created_at)
+        @tag_start = TagVersion.minimum(:created_at)
+        @history_loaded = true
+      end
+      result = { page: @page, limit: @limit, at: @at.iso8601(6),
+                 coverage: { basis: 'recorded_snapshots', exact: false,
+                             post_history_from: @post_start&.iso8601(6),
+                             tag_history_from: @tag_start&.iso8601(6) } }
+      case @mode
+      when 'trend'
+        result.merge(trend)
+      when 'summary'
+        result.merge(metadata ? { totals: totals } : {}).merge(summary)
+      when 'details', 'snapshot'
+        result.merge(metadata ? { totals: totals } : {}).merge(details)
+      else
+        result.merge(metadata ? { totals: totals } : {}).merge(listing)
+      end
+    end
+  end
+
+  def each_page
+    return enum_for(:each_page) unless block_given?
+
+    @page = 1
+    first = call
+    yield first
+    total = ['summary', 'state', 'trend'].include?(@mode) ? first[:group_count] : first[:count]
+    while @page * @limit < total
+      @page += 1
+      yield call(metadata: false)
+    end
+  end
+
+  def validate_query!
+    filtered_scope(@resource)
+    case @mode
+    when 'summary'
+      if @axis == 'tags'
+        order_sql({ 'name' => 'name', 'count' => 'post_count', 'tag_id' => 'tag_id',
+                    'kind' => 'kind', 'deprecated' => 'deprecated_at' }, 'count:desc', [])
+      else
+        record_query('summary')
+      end
+    when 'details', 'snapshot'
+      record_query('details')
+    end
+    self
+  end
+
+  private
+
+  def quote(value) = @connection.quote(value)
+
+  def integer(key, default = nil)
+    value = @params[key]
+    return default if value.blank? && default
+    raise ArgumentError unless value&.match?(/\A[1-9][0-9]{0,9}\z/)
+
+    value.to_i
+  end
+
+  def timestamp(key)
+    value = @params[key].presence
+    return nil unless value
+    pattern = /\A\d{4}-\d{2}-\d{2}T\d{2}:\d{2}(?::\d{2}(?:\.\d{1,6})?)?Z\z/
+    raise ArgumentError unless value.match?(pattern)
+
+    Date.iso8601(value.first(10))
+    Time.iso8601(value.length == 17 ? value.sub(/Z\z/, ':00Z') : value).utc
+  end
+
+  # Version numbers order equal-timestamp writes. Do not filter tags before this selection.
+  def latest_condition(table, row, boundary)
+    key = table == 'post_versions' ? 'post_id' : 'tag_id'
+    <<~SQL.squish
+      #{ row }.created_at #{ @inclusive ? '<=' : '<' } #{ boundary } AND NOT EXISTS (
+        SELECT 1 FROM #{ table } newer
+        WHERE newer.#{ key } = #{ row }.#{ key }
+          AND newer.created_at #{ @inclusive ? '<=' : '<' } #{ boundary }
+          AND newer.version_no > #{ row }.version_no)
+    SQL
+  end
+
+  def state_sql(table, boundary, live: false)
+    sql = "SELECT v.* FROM #{ table } v WHERE #{ latest_condition(table, 'v', boundary) }"
+    live ? "#{ sql } AND v.event_type <> 'discard'" : sql
+  end
+
+  def membership(row)
+    key = @kind == 'external' ? 'external_tag_id' : 'tag_id'
+    "JSON_CONTAINS(#{ row }.tags_json, JSON_OBJECT('#{ key }', #{ @tag }))"
+  end
+
+  # Deprecation keeps a tag in existence. Only an explicit discard removes it.
+  def tag_visible(boundary)
+    return '1 = 1' if @kind == 'external'
+
+    <<~SQL.squish
+      NOT EXISTS (SELECT 1 FROM tag_versions t
+        WHERE t.tag_id = #{ @tag } AND t.event_type = 'discard'
+          AND #{ latest_condition('tag_versions', 't', boundary) })
+    SQL
+  end
+
+  def ctes
+    boundary = quote(@at)
+    <<~SQL
+      WITH post_at AS (#{ filtered_scope('posts').to_sql }),
+      tag_at AS (#{ state_sql('tag_versions', boundary) }),
+      nico_at AS (#{ state_sql('nico_tag_versions', boundary) }),
+      pairs AS (
+        SELECT DISTINCT p.post_id,
+          CASE WHEN entry.tag_id IS NULL THEN 'external' ELSE 'internal' END AS kind,
+          COALESCE(entry.tag_id, entry.external_tag_id) AS tag_id
+        FROM post_at p
+        JOIN JSON_TABLE(CAST(p.tags_json AS JSON), '$[*]' COLUMNS (
+          tag_id BIGINT PATH '$.tag_id' NULL ON EMPTY ERROR ON ERROR,
+          external_tag_id BIGINT PATH '$.external_tag_id' NULL ON EMPTY ERROR ON ERROR
+        )) entry
+        LEFT JOIN tag_at t ON t.tag_id = entry.tag_id
+        WHERE COALESCE(entry.tag_id, entry.external_tag_id) IS NOT NULL
+          AND (t.event_type IS NULL OR t.event_type <> 'discard')
+      )
+    SQL
+  end
+
+  def totals
+    row = @connection.select_one(<<~SQL)
+      #{ ctes }
+      SELECT (SELECT COUNT(*) FROM post_at) AS posts,
+        (SELECT COUNT(*) FROM (#{ filtered_scope('tags').to_sql }) counted_tags) AS tags,
+        (SELECT COUNT(*) FROM tag_at WHERE event_type <> 'discard'
+          AND deprecated_at IS NOT NULL) AS deprecated_tags,
+        (SELECT COUNT(*) FROM pairs) AS assignments,
+        (SELECT COUNT(*) FROM pairs WHERE kind = 'external') AS external_assignments
+    SQL
+    row.transform_values!(&:to_i)
+    row.merge('posts' => available?(@post_start, @at) ? row['posts'] : nil,
+              'assignments' => available?(@post_start, @at) ? row['assignments'] : nil,
+              'external_assignments' => available?(@post_start, @at) ?
+                  row['external_assignments'] : nil,
+              'tags' => available?(@tag_start, @at) ? row['tags'] : nil,
+              'deprecated_tags' => available?(@tag_start, @at) ? row['deprecated_tags'] : nil)
+  end
+
+  def available?(first, boundary)
+    first && (@inclusive ? first <= boundary : first < boundary)
+  end
+
+  def listing
+    path = quote("$.#{ JSON.generate(@language) }.name")
+    catalog = <<~SQL
+      , tag_counts AS (
+        SELECT membership.kind, membership.tag_id, COUNT(*) AS post_count
+        FROM pairs membership GROUP BY membership.kind, membership.tag_id
+      ), catalog AS (
+        SELECT 'internal' AS kind, tag_id,
+          COALESCE(JSON_UNQUOTE(JSON_EXTRACT(names, #{ path })), name) AS name,
+          deprecated_at FROM tag_at WHERE event_type <> 'discard'
+        UNION ALL
+        SELECT tc.kind, tc.tag_id, external_version.name, NULL AS deprecated_at
+        FROM tag_counts tc
+        LEFT JOIN tag_at internal_version
+          ON tc.kind = 'internal' AND internal_version.tag_id = tc.tag_id
+        LEFT JOIN nico_at external_version
+          ON tc.kind = 'external' AND external_version.tag_id = tc.tag_id
+        WHERE tc.kind = 'external' OR internal_version.tag_id IS NULL
+      )
+    SQL
+    filters = []
+    filters << "c.kind = #{ quote(@kind) }" unless @kind == 'all'
+    filters << "c.tag_id = #{ @tag }" if @tag
+    where = filters.any? ? "WHERE #{ filters.join(' AND ') }" : ''
+    source = 'FROM catalog c LEFT JOIN tag_counts n ON n.kind = c.kind AND n.tag_id = c.tag_id'
+    prefix = "#{ ctes } #{ catalog }"
+    total = if @metadata
+              @connection.select_value("#{ prefix } SELECT COUNT(*) #{ source } #{ where }").to_i
+            end
+    order = order_sql({ 'name' => 'c.name', 'count' => 'COALESCE(n.post_count, 0)',
+                        'tag_id' => 'c.tag_id', 'kind' => 'c.kind',
+                        'deprecated' => 'c.deprecated_at' }, 'count:desc',
+                      ['c.kind ASC', 'c.tag_id ASC'])
+    rows = @connection.select_all(<<~SQL)
+      #{ prefix }
+      SELECT c.kind, c.tag_id, c.name, c.deprecated_at,
+        COALESCE(n.post_count, 0) AS post_count #{ source } #{ where }
+      ORDER BY #{ order } LIMIT #{ @limit } OFFSET #{ (@page - 1) * @limit }
+    SQL
+    { count: total, group_count: total, state_rows: rows.map do |row|
+        { kind: row['kind'], tag_id: row['tag_id'], name: row['name'],
+          deprecated: row['deprecated_at']&.iso8601,
+          count: available?(@post_start, @at) ? row['post_count'].to_i : nil,
+          at: @at.iso8601(6) }
+      end }
+  end
+
+  # All record filters apply after selecting the latest recorded version at the point.
+  def restored_scope(resource)
+    model = resource == 'posts' ? PostVersion : TagVersion
+    table = model.table_name
+    scope = model.where(Arel.sql(latest_condition(table, table, quote(@at))))
+        .where.not(event_type: 'discard')
+    if @tag
+      scope = if resource == 'posts'
+                scope.where("#{ membership(table) } AND #{ tag_visible(quote(@at)) }")
+              elsif @kind == 'internal'
+                scope.where(tag_id: @tag)
+              else
+                scope.none
+              end
+    end
+    scope
+  end
+
+  def filtered_scope(resource)
+    params = @params.slice('from', 'before', 'user_id', 'resource_id')
+        .merge('mode' => 'details', 'latest' => '0', 'sort' => '')
+    CountsQuery.new(restored_scope(resource), resource, params,
+                    latest_expression: '1').relation
+  end
+
+  def record_query(mode)
+    params = @params.slice('locale', 'sort', 'page', 'limit')
+        .merge('mode' => mode, 'latest' => '0', 'axis' => @axis == 'tags' ? 'month' : @axis,
+               'page' => @page.to_s, 'limit' => @limit.to_s)
+    CountsQuery.new(filtered_scope(@resource), @resource, params, latest_expression: '1')
+  end
+
+  def summary
+    return listing if @axis == 'tags'
+
+    query = record_query('summary')
+    { count: @metadata ? query.count : nil }.merge(query.summary(include_count: @metadata))
+  end
+
+  def details
+    query = record_query('details')
+    { count: @metadata ? query.count : nil,
+      versions: CountsVersionRepr.many(query.details, resource: @resource,
+                                      language_code: @language, at: @at,
+                                      inclusive: @inclusive) }
+  end
+
+  def next_boundary(time)
+    case @grain
+    when 'day' then time.beginning_of_day + 1.day
+    when 'month' then time.beginning_of_month.next_month
+    else time.beginning_of_year.next_year
+    end
+  end
+
+  def periods
+    @before = timestamp('before') || @now.beginning_of_month
+    @from = timestamp('from') || @before.prev_year
+    raise ArgumentError if @from >= @before || @before > @now
+
+    rows = []
+    boundary = next_boundary(@from)
+    while boundary <= @before
+      raise ArgumentError if rows.length >= MAX_PERIODS
+
+      format = { 'day' => '%Y-%m-%d', 'month' => '%Y-%m', 'year' => '%Y' }.fetch(@grain)
+      rows << [boundary, (boundary - 1.second).strftime(format)]
+      boundary = next_boundary(boundary)
+    end
+    rows
+  end
+
+  def trend
+    points = periods
+    metadata = { count: points.length, group_count: points.length, state_rows: [],
+                 from: @from.iso8601, before: @before.iso8601, grain: @grain }
+    return metadata if points.empty?
+
+    values = points.map do |boundary, period|
+      "SELECT CAST(#{ quote(boundary) } AS DATETIME(6)) AS boundary, " +
+          "#{ quote(period) } AS period"
+    end.join(' UNION ALL ')
+    order = order_sql({ 'period' => 'boundary', 'count' => 'post_count' },
+                      'period:asc', ['boundary ASC'])
+    known = @post_start ? "periods.boundary > #{ quote(@post_start) }" : 'FALSE'
+    rows = @connection.select_all(<<~SQL)
+      WITH periods AS (#{ values }), series AS (
+        SELECT periods.boundary, periods.period,
+          CASE WHEN #{ known } THEN COUNT(DISTINCT p.post_id) ELSE NULL END AS post_count
+        FROM periods
+        LEFT JOIN post_versions p ON p.event_type <> 'discard'
+          AND #{ membership('p') }
+          AND #{ latest_condition('post_versions', 'p', 'periods.boundary') }
+          AND #{ tag_visible('periods.boundary') }
+        GROUP BY periods.boundary, periods.period
+      )
+      SELECT * FROM series ORDER BY #{ order }
+      LIMIT #{ @limit } OFFSET #{ (@page - 1) * @limit }
+    SQL
+    metadata.merge(state_rows: rows.map do |row|
+      { kind: @kind, tag_id: @tag, name: nil, period: row['period'],
+        at: row['boundary'].utc.iso8601(6), count: row['post_count']&.to_i }
+    end)
+  end
+
+  def order_sql(expressions, default, final)
+    raw = @params.fetch('sort', default)
+    sorts = raw.empty? ? [] : raw.split(',', -1).map { _1.split(':', -1) }
+    raise ArgumentError if sorts.map(&:first).uniq.length != sorts.length
+    raise ArgumentError if sorts.length > expressions.length
+
+    order = sorts.flat_map do |key, direction, *extra|
+      if extra.any? || !expressions.key?(key) || !['asc', 'desc'].include?(direction)
+        raise ArgumentError
+      end
+      expression = expressions.fetch(key)
+      ["(#{ expression }) IS NULL ASC", "#{ expression } #{ direction.upcase }"]
+    end
+    (order + final).join(', ')
+  end
+end

backend/app/services/post_creator.rb

@@ -105,7 +105,7 @@ class PostCreator
       category = spec[:category] || spec['category']
       next if name.blank? || category.blank?
 
-      tag = Tag.find_or_create_by_tag_name!(locale, name, category:)
+      tag = Tag.find_or_create_by_tag_name!(locale, name, category:, created_by_user: @actor)
       tag.update!(category:) if tag.category.to_sym != category.to_sym
       tags[name] ||= tag
     end.values

backend/app/services/shared_resource_id_allocator.rb

@@ -13,42 +13,26 @@ class SharedResourceIdAllocator
           ['tag_description_versions', 'tag_id']],
       'wiki' => [['tag_group_versions', 'tag_group_id']] }.freeze
   LOCK_TIMEOUT = 10
+  CONNECTION_LOCKS = ObjectSpace::WeakMap.new
+
+  class LockCleanup
+    def initialize &finish
+      @finish = finish
+    end
+
+    def trigger_transactional_callbacks? = false
+    def before_committed! = nil
+    def committed!(**) = @finish.call(self)
+    def rolledback!(**) = @finish.call(self)
+  end
+  private_constant :LockCleanup
 
   def self.assign! record
     space, tables = SPACES.find { |_name, names| names.include?(record.class.table_name) }
     raise ArgumentError, 'Unknown shared ID resource' unless tables
 
     connection = record.class.connection
-    transaction = record.class.current_transaction
-    unless transaction.open?
-      raise ActiveRecord::ActiveRecordError, 'Shared ID requires a transaction'
-    end
-
-    database = connection.pool.db_config.database
-    name = "btrc:ids:#{ Digest::SHA256.hexdigest(database)[0, 16] }:#{ space }"
-    quoted_name = connection.quote(name)
-    acquired = record.class.uncached do
-      connection.select_value("SELECT GET_LOCK(#{ quoted_name }, #{ LOCK_TIMEOUT })")
-    end
-    unless acquired.to_i == 1
-      raise ActiveRecord::LockWaitTimeout, "Shared ID lock unavailable: #{ space }"
-    end
-
-    release = lambda do
-      result = record.class.uncached do
-        connection.select_value("SELECT RELEASE_LOCK(#{ quoted_name })")
-      end
-      unless result.to_i == 1
-        raise ActiveRecord::ActiveRecordError, "Shared ID lock release failed: #{ space }"
-      end
-    end
-    begin
-      transaction.after_commit(&release)
-      transaction.after_rollback(&release)
-    rescue StandardError
-      release.call
-      raise
-    end
+    lock_space!(record.class, space)
 
     # 明示-tic な Id. 指定は許可する．
     return if record.id.present?
@@ -66,6 +50,68 @@ class SharedResourceIdAllocator
     record.id = next_id
   end
 
+  def self.lock_space! record_class, space
+    raise ArgumentError, 'Unknown shared ID resource' unless SPACES.key?(space)
+
+    connection = record_class.connection
+    transaction = connection.current_transaction
+    unless transaction.open?
+      raise ActiveRecord::ActiveRecordError, 'Shared ID requires a transaction'
+    end
+
+    database = connection.pool.db_config.database
+    name = "btrc:ids:#{ Digest::SHA256.hexdigest(database)[0, 16] }:#{ space }"
+    held_locks = CONNECTION_LOCKS[connection] ||= {}
+    return if held_locks.key?(name)
+
+    quoted_name = connection.quote(name)
+    acquired = record_class.uncached do
+      connection.select_value("SELECT GET_LOCK(#{ quoted_name }, #{ LOCK_TIMEOUT })")
+    end
+    unless acquired.to_i == 1
+      raise ActiveRecord::LockWaitTimeout, "Shared ID lock unavailable: #{ space }"
+    end
+    held_locks[name] = true
+
+    finish = lambda do |cleanup|
+      next unless held_locks.key?(name)
+
+      # Savepoint callbacks may run before the outer transaction ends.
+      # Keep one session lock and transfer its cleanup to the remaining parent.
+      parent = connection.current_transaction
+      if parent.open?
+        connection.add_transaction_record(cleanup)
+        next
+      end
+      result = record_class.uncached do
+        connection.select_value("SELECT RELEASE_LOCK(#{ quoted_name })")
+      end
+      unless result.to_i == 1
+        raise ActiveRecord::ActiveRecordError, "Shared ID lock release failed: #{ space }"
+      end
+      held_locks.delete(name)
+    rescue StandardError
+      # Never return a session with an untracked advisory lock to the pool.
+      begin
+        connection.disconnect!
+      ensure
+        held_locks.clear
+      end
+      raise
+    end
+    begin
+      # Rails finalises remaining records in ensure if another callback raises.
+      connection.add_transaction_record(LockCleanup.new(&finish))
+    rescue StandardError
+      begin
+        connection.disconnect!
+      ensure
+        held_locks.clear
+      end
+      raise
+    end
+  end
+
   def self.next_ids connection, tables
     expiry = connection.select_value('SELECT @@SESSION.information_schema_stats_expiry').to_i
     begin

backend/app/services/tag_description_operation.rb

@@ -5,6 +5,7 @@ class TagDescriptionOperation
 
   def self.create! locale, tag:, body:, created_by_user:, message: nil
     ApplicationRecord.transaction do
+      SharedResourceIdAllocator.lock_space!(Tag, 'tags')
       tag.lock!
       raise ActiveRecord::RecordNotUnique if TagDescription.exists?(
           tag_id: tag.id, language_code: locale.language_code)
@@ -19,6 +20,7 @@ class TagDescriptionOperation
 
   def self.update! locale, tag:, body:, updated_by_user:, message: nil, base_revision_id: nil
     ApplicationRecord.transaction do
+      SharedResourceIdAllocator.lock_space!(Tag, 'tags')
       tag.lock!
       description = TagDescription.lock.find_by!(
           tag_id: tag.id, language_code: locale.language_code)

backend/app/services/tag_name_completion.rb

@@ -0,0 +1,122 @@
+class TagNameCompletion
+  class << self
+    def for_locale! locale
+      completed = Tag.transaction do
+        SharedResourceIdAllocator.lock_space!(Tag, 'tags')
+        certified_names =
+            if locale.certified_tag_names_path.nil?
+              { }
+            else
+              CertifiedTagNameTranslations.load!(locale.certified_tag_names_path, locale:)
+            end
+        Tag.where(id: certified_names.keys).lock.find_each(order: :asc) do |tag|
+          for_tag!(tag, locales: [locale],
+                   certified_names: { locale.language_code => certified_names.fetch(tag.id) },
+                   created_by_user: nil)
+        end
+        named_tags =
+            TagName.where(language_code: locale.language_code, primary_flg: true)
+            .select(:tag_id)
+        Tag.where.not(id: named_tags).lock.find_each(order: :asc) do |tag|
+          for_tag!(tag, locales: [locale], created_by_user: nil)
+        end
+        true
+      end
+      unless completed
+        raise ActiveRecord::RecordNotSaved, 'Locale tag completion was rolled back'
+      end
+    end
+
+    def for_tag! tag, locales: nil, certified_names: { }, created_by_user: nil
+      locales ||=
+          Locale.where(deprecated_at: nil)
+          .order(:language_code, :created_at, :script_code).lock
+      Tag.transaction do
+        SharedResourceIdAllocator.lock_space!(Tag, 'tags')
+        # Creation includes every language in its first snapshot.
+        creating = tag.new_record?
+        tag.save! if creating
+        completed = tag.with_lock do
+          primary_names = tag.tag_names.where(primary_flg: true).lock.index_by(&:language_code)
+          certified_names.each do |language, name|
+            primary = primary_names[language]
+            next unless primary
+            next if primary.name == name && !primary.auto_generated
+
+            raise CertifiedTagNameTranslations::Error,
+                  "Tag##{ tag.id } already has a primary #{ language } name; " +
+                      "cannot register certified name #{ name.inspect }"
+          end
+          missing_locales = locales.to_a.uniq(&:language_code).reject { |locale|
+            primary_names.key?(locale.language_code)
+          }
+          next true if missing_locales.empty? && !creating
+
+          TagVersioning.ensure_snapshot!(tag, created_by_user:) unless creating
+          missing_locales.each do |locale|
+            primary_names[locale.language_code] =
+                if certified_names.key?(locale.language_code)
+                  create_certified_name!(locale, tag, certified_names.fetch(locale.language_code))
+                else
+                  source_language = locale.language_code == 'ja' ? 'ain' : 'ja'
+                  name = TagName.generate_name(locale, tag, primary_names[source_language])
+                  create_name!(locale, tag, name)
+                end
+          end
+          tag.association(:tag_names).reset
+          event_type = creating ? :create : :update
+          version = TagVersioning.record!(tag, event_type:, created_by_user:)
+          unless version&.persisted?
+            raise ActiveRecord::RecordNotSaved, 'Tag version was not persisted'
+          end
+          true
+        end
+        unless completed
+          raise ActiveRecord::RecordNotSaved, 'Tag completion was rolled back'
+        end
+      end
+    end
+
+    private
+
+    def create_certified_name! locale, tag, name
+      persist_name!(locale, tag, name, auto_generated: false)
+    rescue ActiveRecord::RecordInvalid => error
+      raise unless error.record.is_a?(TagName)
+
+      raise CertifiedTagNameTranslations::Error,
+            "Tag##{ tag.id } certified name #{ name.inspect }: " +
+                error.record.errors.full_messages.join(', ')
+    rescue ActiveRecord::RecordNotUnique => error
+      raise CertifiedTagNameTranslations::Error,
+            "Tag##{ tag.id } certified name #{ name.inspect } conflicts: #{ error.message }"
+    end
+
+    def create_name! locale, tag, name
+      persist_name!(locale, tag, name, auto_generated: true)
+    rescue ActiveRecord::RecordNotUnique, ActiveRecord::RecordInvalid => error
+      fallback = "Tag_##{ tag.id }"
+      invalid_name =
+          if error.is_a?(ActiveRecord::RecordNotUnique)
+            TagName.where(language_code: locale.language_code, name:).lock.exists?
+          else
+            error.record.errors[:name].present? &&
+                error.record.errors.attribute_names.all? { _1 == :name }
+          end
+      raise if name == fallback || !(invalid_name)
+
+      persist_name!(locale, tag, fallback, auto_generated: true)
+    end
+
+    def persist_name! locale, tag, name, auto_generated:
+      tag_name = TagName.transaction(requires_new: true) do
+        TagName.create!(tag:, name:, language_code: locale.language_code,
+                        script_code: locale.script_code, primary_flg: true, auto_generated:)
+      end
+      unless tag_name&.persisted?
+        raise ActiveRecord::RecordNotSaved, 'Generated tag name was not persisted'
+      end
+      tag_name
+    end
+  end
+end

backend/app/services/tag_name_transcription.rb

@@ -0,0 +1,56 @@
+module TagNameTranscription
+  class Unconvertible < StandardError
+    ;
+  end
+
+  def self.ainu name
+    previous_script = nil
+    parts = []
+    NipponeseSegments.split(name).each do |script, text|
+      output = transcribe_segment(script, text)
+      if (parts.last && output.first && previous_script && script != previous_script &&
+          NipponeseSegments.nipponese?(previous_script) && NipponeseSegments.nipponese?(script))
+        parts << '_'
+      end
+
+      parts.concat(output)
+      previous_script = script
+    end
+
+    replace_unconvertible(parts)
+  end
+
+  def self.transcribe_segment script, text
+    return [text] if script == :literal
+    return [nil] if script == :unconvertible
+    return transcribe_reading(text) unless script == :kanzi
+
+    text.each_char.flat_map do |character|
+      transcribe_reading(JisReadings.read(character))
+    rescue Unconvertible
+      [nil]
+    end
+  end
+
+  def self.transcribe_reading reading
+    Phonology.adapt(reading).map do |sound|
+      sound && Katakana.render([sound])
+    rescue Unconvertible
+      nil
+    end
+  end
+
+  def self.replace_unconvertible parts
+    grouped = parts.chunk { _1.nil? }.flat_map { |unconvertible, group|
+      unconvertible ? [nil] : group
+    }
+    first = grouped.index { _1&.match?(/[^_]/) }
+    last = grouped.rindex { _1&.match?(/[^_]/) }
+
+    grouped.each_with_index.map { |part, index|
+      part || (first && first < index && index < last ? '_' : '')
+    }.join
+  end
+
+  private_class_method :transcribe_segment, :transcribe_reading, :replace_unconvertible
+end

backend/app/services/tag_name_transcription/jis_readings.rb

@@ -0,0 +1,13 @@
+module TagNameTranscription
+  module JisReadings
+    SOURCE = Rails.root.join('config/tag_name_readings/jis_level_one.tsv')
+    READINGS = File.foreach(SOURCE, chomp: true).reject { _1.start_with?('#') }.to_h { |line|
+      character, reading, = line.split("\t")
+      [character, reading]
+    }.freeze
+
+    def self.read text
+      text.each_char.map { READINGS.fetch(_1) { raise Unconvertible } }.join
+    end
+  end
+end

backend/app/services/tag_name_transcription/katakana.rb

@@ -0,0 +1,26 @@
+module TagNameTranscription
+  module Katakana
+    ROWS = {
+        '' => 'アイウエオ',
+        'k' => 'カキクケコ',
+        's' => 'サシスセソ',
+        'c' => ['チャ', 'チ', 'チュ', 'チェ', 'チョ'],
+        't' => ['タ', 'ティ', 'トゥ', 'テ', 'ト'],
+        'n' => 'ナニヌネノ',
+        'h' => 'ハヒフヘホ',
+        'p' => 'パピプペポ',
+        'm' => 'マミムメモ',
+        'r' => 'ラリルレロ' }.freeze
+    SYLLABLES = ROWS.flat_map { |onset, letters|
+      kana = letters.is_a?(String) ? letters.chars : letters
+      ['a', 'i', 'u', 'e', 'o'].zip(kana).map { |vowel, letter| [onset + vowel, letter] }
+    }.to_h.merge(
+        'ya' => 'ヤ', 'yu' => 'ユ', 'yo' => 'ヨ', 'wa' => 'ワ',
+        'k' => 'ㇰ', 's' => 'ㇱ', 't' => 'ッ', 'n' => 'ン', 'm' => 'ㇺ', 'p' => 'ㇷ゚',
+        'r:a' => 'ㇻ', 'r:i' => 'ㇼ', 'r:u' => 'ㇽ', 'r:e' => 'ㇾ', 'r:o' => 'ㇿ').freeze
+
+    def self.render sounds
+      sounds.map { SYLLABLES.fetch(_1) { raise Unconvertible } }.join
+    end
+  end
+end

backend/app/services/tag_name_transcription/nipponese_segments.rb

@@ -0,0 +1,30 @@
+module TagNameTranscription
+  module NipponeseSegments
+    NIPPONESE_SCRIPTS = [:kanzi, :xiragana, :katakana].freeze
+
+    def self.nipponese?(script) = NIPPONESE_SCRIPTS.include?(script)
+
+    def self.split name
+      segments = []
+      name.to_s.scan(/\X/).each do |character|
+        script = classify(character, segments.last&.first)
+        if segments.last&.first == script
+          segments.last[1] << character
+        else
+          segments << [script, character.dup]
+        end
+      end
+      segments
+    end
+
+    def self.classify character, previous_script
+      return previous_script if character == 'ー' && nipponese?(previous_script)
+      return :kanzi if character.match?(/\A\p{Han}\z/)
+      return :xiragana if character.match?(/\A\p{Hiragana}\p{M}*\z/)
+      return :katakana if character.match?(/\A\p{Katakana}\p{M}*\z/)
+      return :literal if character.match?(/\A(?:\p{Latin}\p{M}*|[!-~])\z/)
+
+      :unconvertible
+    end
+  end
+end

backend/app/services/tag_name_transcription/phonology.rb

@@ -0,0 +1,59 @@
+module TagNameTranscription
+  module Phonology
+    ROWS = {
+        'アイウエオ' => ['a', 'i', 'u', 'e', 'o'],
+        'カキクケコ' => ['ka', 'ki', 'ku', 'ke', 'ko'],
+        'ガギグゲゴ' => ['ka', 'ki', 'ku', 'ke', 'ko'],
+        'サシスセソ' => ['sa', 'si', 'su', 'se', 'so'],
+        'ザジズゼゾ' => ['ca', 'ci', 'cu', 'ce', 'co'],
+        'タチツテト' => ['ta', 'ci', 'cu', 'te', 'to'],
+        'ダヂヅデド' => ['ta', 'ci', 'cu', 'te', 'to'],
+        'ナニヌネノ' => ['na', 'ni', 'nu', 'ne', 'no'],
+        'ハヒフヘホ' => ['ha', 'hi', 'hu', 'he', 'ho'],
+        'バビブベボ' => ['pa', 'pi', 'pu', 'pe', 'po'],
+        'パピプペポ' => ['pa', 'pi', 'pu', 'pe', 'po'],
+        'マミムメモ' => ['ma', 'mi', 'mu', 'me', 'mo'],
+        'ヤユヨ' => ['ya', 'yu', 'yo'],
+        'ラリルレロ' => ['ra', 'ri', 'ru', 're', 'ro'],
+        'ワ' => ['wa'],
+        'ン' => ['n'],
+        'ッ' => ['t'],
+        'ㇰ' => ['k'],
+        'ㇱㇲ' => ['s', 's'],
+        'ㇳ' => ['t'],
+        'ㇴ' => ['n'],
+        'ㇺ' => ['m'],
+        'ㇻㇼㇽㇾㇿ' => ['r:a', 'r:i', 'r:u', 'r:e', 'r:o'] }.freeze
+
+    SOUNDS = ROWS.flat_map { |characters, sounds| characters.chars.zip(sounds) }.to_h.freeze
+
+    DIGRAPHS = {
+        'シャ' => 'sa', 'シュ' => 'su', 'シェ' => 'se', 'ショ' => 'so',
+        'チャ' => 'ca', 'チュ' => 'cu', 'チェ' => 'ce', 'チョ' => 'co',
+        'ジャ' => 'ca', 'ジュ' => 'cu', 'ジェ' => 'ce', 'ジョ' => 'co',
+        'ヂャ' => 'ca', 'ヂュ' => 'cu', 'ヂェ' => 'ce', 'ヂョ' => 'co' }.freeze
+
+    def self.adapt reading
+      kana = reading.unicode_normalize(:nfc).tr('ぁ-ゖ', 'ァ-ヶ').delete('ー')
+      characters = kana.scan(/\X/)
+      sounds = []
+      index = 0
+
+      while index < characters.length
+        pair = characters[index, 2].join
+
+        if DIGRAPHS.key?(pair)
+          sounds << DIGRAPHS.fetch(pair)
+          index += 2
+          next
+        end
+
+        character = characters[index].tr('ャュョ', 'ヤユヨ')
+        sounds << (character == 'ㇷ゚' ? 'p' : SOUNDS[character])
+        index += 1
+      end
+
+      sounds
+    end
+  end
+end

backend/app/services/tag_version_recorder.rb

@@ -1,6 +1,9 @@
 class TagVersionRecorder < VersionRecorder
   def self.record! tag:, event_type:, created_by_user:, **_options
-    new(tag:, event_type:, created_by_user:).record!
+    Tag.transaction do
+      SharedResourceIdAllocator.lock_space!(Tag, 'tags')
+      new(tag:, event_type:, created_by_user:).record!
+    end
   end
 
   def initialize tag:, event_type:, created_by_user:
@@ -15,26 +18,39 @@ class TagVersionRecorder < VersionRecorder
 
   def snapshot_attributes
     names = snapshot_names
-    compatibility_names = names.fetch('ja')
+    compatibility_names = names['ja'] || names['ain'] || names.values.first
+    unless compatibility_names
+      @record.errors.add(:tag_names, :invalid)
+      raise ActiveRecord::RecordInvalid, @record
+    end
+    parent_ids =
+        TagImplication.where(tag_id: @record.id).order(:parent_tag_id)
+        .lock.pluck(:parent_tag_id)
 
     { name: compatibility_names.fetch('name'),
       category: @record.category,
       deprecated_at: @record.deprecated_at,
       aliases: compatibility_names.fetch('aliases').map { _1.fetch('name') }.join(' '),
       names:,
-      parent_tag_ids: @record.snapshot_parent_tag_ids.join(' ') }
+      parent_tag_ids: parent_ids.join(' ') }
   end
 
   def snapshot_names
-    @record.tag_names.order(:language_code, :name).group_by(&:language_code)
+    @record.tag_names.order(:language_code, :name).lock.group_by(&:language_code)
         .transform_values do |tag_names|
       primary = tag_names.find(&:primary?)
+      unless primary
+        @record.errors.add(:tag_names, :invalid,
+                           language_code: tag_names.first.language_code)
+        raise ActiveRecord::RecordInvalid, @record
+      end
       aliases = tag_names.reject(&:primary?).sort_by(&:name).map { |tag_name|
-        { 'name' => tag_name.name, 'script_code' => tag_name.script_code }
+        { 'name' => tag_name.name,
+          'script_code' => Script.codes.fetch(tag_name.script_code, tag_name.script_code) }
       }
 
       { 'name' => primary.name,
-        'script_code' => primary.script_code,
+        'script_code' => Script.codes.fetch(primary.script_code, primary.script_code),
         'auto_generated' => primary.auto_generated,
         'aliases' => aliases }
     end

backend/app/services/tag_versioning.rb

@@ -4,14 +4,23 @@ class TagVersioning
   end
 
   def self.ensure_snapshot! tag, created_by_user:, language_code: 'ja'
-    return if tag.tag_versions.exists?
+    Tag.transaction do
+      SharedResourceIdAllocator.lock_space!(Tag, 'tags')
+      locked_tag = Tag.unscoped.lock.find(tag.id)
+      next if locked_tag.tag_versions.lock.exists?
 
-    TagVersionRecorder.record!(tag:, event_type: :create, created_by_user:, language_code:)
+      TagVersionRecorder.record!(
+          tag: locked_tag, event_type: :create, created_by_user:, language_code:)
+    end
   end
 
   def self.record_tag_snapshot! tag, created_by_user:, language_code: 'ja'
-    event_type = tag.tag_versions.exists? ? :update : :create
-    record!(tag, event_type:, created_by_user:, language_code:)
+    Tag.transaction do
+      SharedResourceIdAllocator.lock_space!(Tag, 'tags')
+      locked_tag = Tag.unscoped.lock.find(tag.id)
+      event_type = locked_tag.tag_versions.lock.exists? ? :update : :create
+      record!(locked_tag, event_type:, created_by_user:, language_code:)
+    end
   end
 
   def self.record_tag_snapshots! tags, created_by_user:, language_code: 'ja'

backend/app/services/version_recorder.rb

@@ -35,7 +35,7 @@ class VersionRecorder
 
   private
 
-  def latest_version = versions.order(version_no: :desc).first
+  def latest_version = versions.order(version_no: :desc).lock.first
 
   def versions = @record.public_send(version_association)
 

backend/config/application.rb

@@ -31,5 +31,14 @@ module Backend
     # Middleware like session, flash, cookies can be added back manually.
     # Skip views, helpers and assets when generating a new resource.
     config.api_only = true
+    config.middleware.use ActionDispatch::Cookies
+    config.session_store :cookie_store,
+                         key: Rails.env.production? ? '__Host-btrc-session' : 'btrc-session',
+                         path: '/',
+                         secure: Rails.env.production?,
+                         httponly: true,
+                         same_site: :lax,
+                         expire_after: 20.years
+    config.middleware.use ActionDispatch::Session::CookieStore, config.session_options
   end
 end

backend/config/initializers/filter_parameter_logging.rb

@@ -4,5 +4,5 @@
 # Use this to limit dissemination of sensitive information.
 # See the ActiveSupport::ParameterFilter documentation for supported notations and behaviors.
 Rails.application.config.filter_parameters += [
-  :passw, :email, :secret, :token, :_key, :crypt, :salt, :certificate, :otp, :ssn, :cvv, :cvc
-]
+    :passw, :email, :secret, :token, :_key, :crypt, :salt, :certificate,
+    :otp, :ssn, :cvv, :cvc, :code, :inheritance_code]

backend/config/routes.rb

@@ -1,4 +1,13 @@
 Rails.application.routes.draw do
+  get 'counts/export', to: 'counts_exports#index'
+  post 'counts/export', to: 'counts_exports#index'
+  get 'counts/state', to: 'counts_states#index'
+  get 'counts/posts', to: 'counts_posts#index'
+  get 'counts/tags', to: 'counts_tags#index'
+
+  resources :locales, only: [:index]
+  resources :sitemap_entries, only: [:index, :show], param: :resource
+
   resources :tag_groups, only: [:index, :show, :create, :update]
 
   resources :nico_tags, path: 'tags/nico', only: [:index, :show, :update]
@@ -43,6 +52,7 @@ Rails.application.routes.draw do
     collection do
       get :search, action: :index
       get :changes
+      get :autolink_candidates
 
       scope :title do
         get ':title/exists', action: :exists_by_title
@@ -53,12 +63,14 @@ Rails.application.routes.draw do
     member do
       get :exists
       get :diff
+      get :tag, action: :tag_reference
     end
   end
 
   resources :posts, only: [:index, :show, :create, :update] do
     collection do
       get :metadata
+      get :tag_filters
       post :bulk
       get :random
       get :versions, to: 'post_versions#index'
@@ -97,6 +109,9 @@ Rails.application.routes.draw do
     collection do
       post :verify
       get :me
+      get :session, action: :show_session
+      get :csrf
+      delete :session, action: :destroy_session
       post 'code/renew', action: :renew
     end
   end

backend/db/seeds.rb

@@ -8,6 +8,11 @@
 #     MovieGenre.find_or_create_by!(name: genre_name)
 #   end
 
+ApplicationRecord.transaction do
+  Language.find_or_create_by!(code: 'ain') { _1.name = 'ain' }
+  Script.find_or_create_by!(code: 'Kana') { _1.name = 'Kana' }
+end
+
 post_url_sanitisation_rules = [
   { priority: 10,
     source_pattern: '\Ahttps?://youtu\.be/([^/?#]+)(?:[?#].*)?\z',

backend/spec/factories/tags.rb

@@ -24,17 +24,7 @@ FactoryBot.define do
 
       evaluator.primary_tag_name.update!(tag:, primary_flg: true)
 
-      Locale.where(deprecated_at: nil).order(:language_code, :created_at, :script_code).to_a
-          .uniq(&:language_code).each do |locale|
-        next if tag.tag_names.exists?(language_code: locale.language_code,
-                                      primary_flg: true)
-
-        create(:tag_name,
-            tag:, language_code: locale.language_code,
-            script_code: locale.script_code,
-            name: TagName.generate_name(locale, tag, evaluator.primary_tag_name),
-            primary_flg: true, auto_generated: true)
-      end
+      TagNameCompletion.for_tag!(tag)
     end
   end
 end

backend/spec/models/language_spec.rb

@@ -6,9 +6,8 @@ RSpec.describe Language, type: :model do
     expect(described_class.where(deprecated_at: nil).pluck(:code)).to eq(['ja'])
   end
 
-  it 'accepts English when multilingual support is enabled' do
-    pending '日本語以外の Language 有効化は別課題で実装する'
-    expect { described_class.create!(code: 'en', name: 'English') }
+  it 'accepts Ainu when multilingual support is enabled' do
+    expect { described_class.create!(code: 'ain', name: 'ain') }
         .to change(described_class, :count).by(1)
   end
 

backend/spec/models/locale_activation_spec.rb

@@ -0,0 +1,82 @@
+require 'rails_helper'
+
+RSpec.describe 'Locale activation', type: :model do
+  let!(:language) { Language.create!(code: 'ain', name: 'ain') }
+  let!(:script) { Script.create!(code: 'Kana', name: 'Kana') }
+  let!(:first) { create(:tag, primary_name: 'activation_first') }
+  let!(:second) { create(:tag, primary_name: 'activation_second') }
+
+  def build_locale deprecated_at: nil
+    Locale.new(code: 'ain-Kana', language_code: language.code,
+               script_code: script.code, region_code: 392, variants: '',
+               name: 'ain-Kana', deprecated_at:)
+  end
+
+  def generated_names
+    TagName.where(language_code: 'ain', primary_flg: true)
+  end
+
+  def fail_second_generation!
+    allow(TagName).to receive(:generate_name).and_call_original
+    allow(TagName).to receive(:generate_name)
+        .with(kind_of(Locale), second, second.tag_name('ja'))
+        .and_raise('backfill failed')
+  end
+
+  it 'rolls back a newly created locale and the preceding generated names' do
+    locale = build_locale
+    fail_second_generation!
+
+    expect { locale.save! }.to raise_error('backfill failed')
+
+    expect(Locale.exists?(code: 'ain-Kana')).to be(false)
+    expect(generated_names).to be_empty
+    expect(first.reload.name('ja')).to eq('activation_first')
+    expect(second.reload.name('ja')).to eq('activation_second')
+  end
+
+  it 'does not backfill while the locale is inactive' do
+    build_locale(deprecated_at: Time.current).save!
+
+    expect(generated_names).to be_empty
+  end
+
+  it 'backfills missing primary names when the locale becomes active' do
+    locale = build_locale(deprecated_at: Time.current)
+    locale.save!
+
+    locale.update!(deprecated_at: nil)
+
+    expect(generated_names.pluck(:tag_id)).to contain_exactly(first.id, second.id)
+    expect(generated_names).to all(have_attributes(
+        script_code: 'Kana', primary_flg: true, auto_generated: true))
+  end
+
+  it 'rolls back activation and all generated names when backfill fails' do
+    locale = build_locale(deprecated_at: Time.current)
+    locale.save!
+    previous_deprecated_at = locale.reload.deprecated_at
+    fail_second_generation!
+
+    expect { locale.update!(deprecated_at: nil) }.to raise_error('backfill failed')
+
+    expect(locale.reload.deprecated_at).to eq(previous_deprecated_at)
+    expect(generated_names).to be_empty
+  end
+
+  it 'preserves a human primary through deactivation and repeated activation' do
+    locale = build_locale
+    locale.save!
+    primary = generated_names.find_by!(tag: first)
+    primary.update!(name: 'human_confirmed', auto_generated: false)
+    snapshot = generated_names.order(:id).map(&:attributes)
+
+    2.times do
+      locale.update!(deprecated_at: Time.current)
+      locale.update!(deprecated_at: nil)
+    end
+
+    expect(generated_names.order(:id).map(&:attributes)).to eq(snapshot)
+    expect(primary.reload).to have_attributes(name: 'human_confirmed', auto_generated: false)
+  end
+end

backend/spec/models/locale_spec.rb

@@ -1,13 +1,13 @@
 require 'rails_helper'
 
 RSpec.describe Locale, type: :model do
-  include_context 'English locale'
+  include_context 'Ainu locale'
 
-  def create_english_locale!
-    prepare_english_reference!
-    described_class.create!(code: 'en', language_code: 'en',
-                            script_code: 'Latn', region_code: 826,
-                            variants: '', name: 'English')
+  def create_ainu_locale!
+    prepare_ainu_reference!
+    described_class.create!(code: 'ain-Kana', language_code: 'ain',
+                            script_code: 'Kana', region_code: 392,
+                            variants: '', name: 'Ainu')
   end
 
   it 'keeps the active Nipponese locale consistent with its identity tuple' do
@@ -27,7 +27,6 @@ RSpec.describe Locale, type: :model do
   end
 
   it 'generates a primary name for every existing tag using the name generator' do
-    pending '日本語以外の Locale 有効化は別課題で実装する'
     first = create(:tag, primary_name: 'first_existing_tag')
     second = create(:tag, primary_name: 'second_existing_tag')
     allow(TagName).to receive(:generate_name).and_call_original
@@ -35,95 +34,152 @@ RSpec.describe Locale, type: :model do
         .with(kind_of(described_class), first, primary_tag_name_for(first, 'ja'))
         .and_return('name_from_generator')
 
-    locale = create_english_locale!
+    locale = create_ainu_locale!
 
     expect(TagName).to have_received(:generate_name)
         .with(locale, first, primary_tag_name_for(first, 'ja'))
     expect(TagName).to have_received(:generate_name)
         .with(locale, second, primary_tag_name_for(second, 'ja'))
-    expect(first.tag_names.find_by!(language_code: 'en', primary_flg: true))
+    expect(first.tag_names.find_by!(language_code: 'ain', primary_flg: true))
         .to have_attributes(name: 'name_from_generator', tag_id: first.id,
-                            language_code: 'en', script_code: 'Latn',
+                            language_code: 'ain', script_code: 'Kana',
                             primary_flg: true, auto_generated: true)
-    expect(second.tag_names.find_by!(language_code: 'en', primary_flg: true))
-        .to have_attributes(tag_id: second.id, language_code: 'en',
-                            script_code: 'Latn', primary_flg: true,
+    expect(second.tag_names.find_by!(language_code: 'ain', primary_flg: true))
+        .to have_attributes(tag_id: second.id, language_code: 'ain',
+                            script_code: 'Kana', primary_flg: true,
                             auto_generated: true)
-    expect(TagName.where(language_code: 'en', primary_flg: true,
+    expect(TagName.where(language_code: 'ain', primary_flg: true,
                          tag_id: [first.id, second.id]).count).to eq(2)
   end
 
   it 'does not duplicate an existing primary name in the new language' do
-    pending '日本語以外の Locale 有効化は別課題で実装する'
-    prepare_english_reference!
+    prepare_ainu_reference!
     tag = create(:tag, primary_name: 'already_named')
-    existing = create(:tag_name, name: 'existing_english', tag:,
-                                 language_code: 'en', script_code: 'Latn')
+    existing = create(:tag_name, name: 'existing_ainu', tag:,
+                                 language_code: 'ain', script_code: 'Kana')
+    versions_before = tag.tag_versions.order(:version_no).map(&:attributes)
 
-    create_english_locale!
+    create_ainu_locale!
 
-    expect(TagName.where(tag_id: tag.id, language_code: 'en', primary_flg: true))
+    expect(TagName.where(tag_id: tag.id, language_code: 'ain', primary_flg: true))
         .to contain_exactly(existing)
     expect(existing.reload).to have_attributes(
-        tag_id: tag.id, language_code: 'en', script_code: 'Latn',
+        tag_id: tag.id, language_code: 'ain', script_code: 'Kana',
         primary_flg: true, auto_generated: false)
+    expect(tag.tag_versions.order(:version_no).map(&:attributes)).to eq(versions_before)
   end
 
-  it 'creates a primary name when the language has only an alias' do
-    pending '日本語以外の Locale 有効化は別課題で実装する'
-    prepare_english_reference!
-    tag = create(:tag, primary_name: 'alias_only_tag')
-    alias_name = create(:tag_name, :alias, name: 'alias_en',
-                                          tag:,
-                                          language_code: 'en', script_code: 'Latn')
+  it 'adds the new language primary while preserving existing names and aliases' do
+    tag = create(:tag, primary_name: 'named_tag')
+    create(:tag_name, :alias, name: 'existing_alias', tag:,
+                              language_code: 'ja', script_code: 'Jpan')
+    original_names = tag.tag_names.order(:id).map(&:attributes)
 
-    create_english_locale!
+    create_ainu_locale!
 
-    expect(alias_name.reload).to have_attributes(
-        tag_id: tag.id,
-        language_code: 'en', script_code: 'Latn', primary_flg: false)
-    generated = TagName.find_by!(tag_id: tag.id, language_code: 'en', primary_flg: true)
-    expect(generated).to have_attributes(tag_id: tag.id, language_code: 'en',
-                                         script_code: 'Latn', primary_flg: true,
+    expect(tag.tag_names.where(language_code: 'ja').order(:id).map(&:attributes))
+        .to eq(original_names)
+    generated = TagName.find_by!(tag_id: tag.id, language_code: 'ain', primary_flg: true)
+    expect(generated).to have_attributes(name: 'named_tag', tag_id: tag.id, language_code: 'ain',
+                                         script_code: 'Kana', primary_flg: true,
                                          auto_generated: true)
-    expect(TagName.where(tag_id: tag.id, language_code: 'en', primary_flg: true).count).to eq(1)
+    expect(TagName.where(tag_id: tag.id, language_code: 'ain', primary_flg: true).count).to eq(1)
   end
 
   it 'rolls back the locale and all generated names when backfill fails' do
-    pending '日本語以外の Locale 有効化は別課題で実装する'
-    prepare_english_reference!
+    prepare_ainu_reference!
     first = create(:tag, primary_name: 'atomic_first')
     second = create(:tag, primary_name: 'atomic_second')
+    versions_before = TagVersion.order(:id).map(&:attributes)
     allow(TagName).to receive(:generate_name).and_call_original
     allow(TagName).to receive(:generate_name)
         .with(kind_of(described_class), second, primary_tag_name_for(second, 'ja'))
         .and_raise('backfill failed')
 
-    expect { create_english_locale! }.to raise_error('backfill failed')
+    expect { create_ainu_locale! }.to raise_error('backfill failed')
 
-    expect(described_class.exists?(code: 'en')).to be(false)
-    expect(TagName.where(language_code: 'en', tag_id: [first.id, second.id])).to be_empty
+    expect(described_class.exists?(code: 'ain-Kana')).to be(false)
+    expect(TagName.where(language_code: 'ain', tag_id: [first.id, second.id])).to be_empty
+    expect(TagVersion.order(:id).map(&:attributes)).to eq(versions_before)
   end
 
-  it 'accepts a stable locale code outside the historical enum values' do
-    pending '日本語以外の Locale 有効化は別課題で実装する'
-    prepare_english_reference!
+  it 'records a separate automatic update for each tag without changing its authored create' do
+    author = create(:user, :admin)
+    tags = ['locale_history_first', 'locale_history_second'].map do |name|
+      Tag.find_or_create_by_tag_name!(Locale.nipponese, name, category: :general,
+                                     created_by_user: author)
+    end
+    originals = tags.map { |tag| tag.tag_versions.sole.attributes }
 
-    locale = described_class.create!(
-        code: 'en-x-rspec', language_code: 'en',
-        script_code: 'Latn', region_code: 826,
-        variants: 'x-rspec', name: 'English')
+    expect { create_ainu_locale! }.to change(TagVersion, :count).by(2)
 
-    expect(locale.reload).to have_attributes(
-        code: 'en-x-rspec', language_code: 'en', script_code: 'Latn',
-        region_code: 826, variants: 'x-rspec')
+    tags.zip(originals).each do |tag, original|
+      versions = tag.tag_versions.order(:version_no).to_a
+      expect(versions.map(&:event_type)).to eq(['create', 'update'])
+      expect(versions.first.attributes).to eq(original)
+      expect(versions.first.created_by_user_id).to eq(author.id)
+      expect(versions.last).to have_attributes(version_no: 2, created_by_user_id: nil)
+      expect(versions.last.names.fetch('ain')).to eq(
+          'name' => tag.name('ja'), 'script_code' => 'Kana',
+          'auto_generated' => true, 'aliases' => [])
+      expect(versions.first.names.keys).to eq(['ja'])
+      expect(tag.reload.version_no).to eq(2)
+    end
+
+    expect { TagNameCompletion.for_locale!(Locale.find('ain-Kana')) }
+        .not_to change(TagVersion, :count)
   end
 
-  it 'registers the future British English locale tuple' do
-    pending '日本語以外の Locale 有効化は別課題で実装する'
+  it 'records automatic before and after snapshots for a tag without any history' do
+    tag = create(:tag, primary_name: 'legacy_before_locale')
+    expect(tag.tag_versions).to be_empty
 
-    expect(locale).to have_attributes(code: 'en', language_code: 'en',
-                                    script_code: 'Latn', region_code: 826,
+    create_ainu_locale!
+
+    versions = tag.tag_versions.order(:version_no).to_a
+    expect(versions.map(&:event_type)).to eq(['create', 'update'])
+    expect(versions.map(&:created_by_user_id)).to eq([nil, nil])
+    expect(versions.first.names.keys).to eq(['ja'])
+    expect(versions.last.names.keys).to match_array(['ja', 'ain'])
+    expect(versions.last.names.fetch('ja')).to eq(versions.first.names.fetch('ja'))
+  end
+
+  it 'rolls back earlier tag names and histories when a later history fails' do
+    first = create(:tag, primary_name: 'history_atomic_first')
+    second = create(:tag, primary_name: 'history_atomic_second')
+    names_before = TagName.order(:id).map(&:attributes)
+    versions_before = TagVersion.order(:id).map(&:attributes)
+    allow(TagVersioning).to receive(:record!).and_wrap_original do |original, tag, **options|
+      if tag.id == second.id && options[:event_type] == :update
+        raise ActiveRecord::RecordNotSaved, 'history failed'
+      end
+      original.call(tag, **options)
+    end
+
+    expect { create_ainu_locale! }
+        .to raise_error(ActiveRecord::RecordNotSaved, 'history failed')
+
+    expect(described_class.exists?(code: 'ain-Kana')).to be(false)
+    expect(TagName.order(:id).map(&:attributes)).to eq(names_before)
+    expect(TagVersion.order(:id).map(&:attributes)).to eq(versions_before)
+    expect([first.reload.version_no, second.reload.version_no]).to eq([1, 1])
+  end
+
+  it 'rejects a private locale code outside the supported locale set' do
+    prepare_ainu_reference!
+
+    expect {
+      described_class.create!(
+          code: 'ain-Kana-x-rspec', language_code: 'ain',
+          script_code: 'Kana', region_code: 392,
+          variants: 'x-rspec', name: 'Ainu')
+    }.to raise_error(ArgumentError)
+  end
+
+  it 'registers the supported Ainu locale tuple' do
+
+    expect(locale).to have_attributes(code: 'ain-Kana', language_code: 'ain',
+                                    script_code: 'Kana', region_code: 392,
                                     variants: '')
   end
 end

backend/spec/models/script_spec.rb

@@ -1,7 +1,7 @@
 require 'rails_helper'
 
 RSpec.describe Script, type: :model do
-  include_context 'English locale'
+  include_context 'Ainu locale'
 
   it 'selects locales by script code, not language code' do
     expect(described_class.find('Jpan').locales).to contain_exactly(Locale.nipponese)
@@ -25,11 +25,10 @@ RSpec.describe Script, type: :model do
     }
   end
 
-  it 'selects Latin locales when multilingual support is enabled' do
-    pending '日本語以外の Locale 有効化は別課題で実装する'
+  it 'selects Kana locales when multilingual support is enabled' do
     locale
 
-    expect(described_class.find('Latn').locales).to contain_exactly(locale)
+    expect(described_class.find('Kana').locales).to contain_exactly(locale)
     expect(described_class.find('Jpan').locales).not_to include(locale)
   end
 end

backend/spec/models/tag_name_sanitisation_rule_spec.rb

@@ -95,38 +95,38 @@ RSpec.describe TagNameSanitisationRule, type: :model do
     end
 
     context 'when only another language has the sanitised name' do
-      include_context 'English locale'
+      include_context 'Ainu locale'
 
       it 'keeps both names when sanitisation produces a cross-language match' do
-        pending '日本語以外の Locale 有効化は別課題で実装する'
         locale
         nipponese = create(:tag_name, name: 'foobar')
-        english = create(:tag_name, name: 'temporary',
-                                   language_code: 'en', script_code: 'Latn')
-        english.update_columns(name: 'foo_bar')
+        ainu = create(:tag_name, name: 'temporary',
+                                   language_code: 'ain', script_code: 'Kana')
+        ainu.update_columns(name: 'foo_bar')
 
         expect { described_class.apply! }.not_to change(TagName, :count)
 
-        expect(english.reload).to have_attributes(name: 'foobar', language_code: 'en')
+        expect(ainu.reload).to have_attributes(name: 'foobar', language_code: 'ain')
         expect(nipponese.reload).to have_attributes(name: 'foobar', language_code: 'ja')
       end
 
       it 'renames without merging tags or deleting either language identity' do
-        pending '日本語以外の Locale 有効化は別課題で実装する'
         locale
         nipponese = create(:tag, primary_name: 'foobar')
-        english_name = create(:tag_name, name: 'temporary',
-                                        language_code: 'en', script_code: 'Latn')
-        english = create(:tag, primary_tag_name: english_name)
-        english_name.update_columns(name: 'foo_bar')
+        primary_tag_name_for(nipponese, 'ain').update!(
+            name: 'different_ainu_name', auto_generated: false)
+        ainu_name = create(:tag_name, name: 'temporary',
+                                        language_code: 'ain', script_code: 'Kana')
+        ainu = create(:tag, primary_tag_name: ainu_name)
+        ainu_name.update_columns(name: 'foo_bar')
 
         described_class.apply!
 
-        expect(english_name.reload).to have_attributes(
-            name: 'foobar', language_code: 'en', tag_id: english.id)
+        expect(ainu_name.reload).to have_attributes(
+            name: 'foobar', language_code: 'ain', tag_id: ainu.id)
         expect(primary_tag_name_for(nipponese.reload, 'ja')).to have_attributes(
             name: 'foobar', language_code: 'ja', tag_id: nipponese.id)
-        expect(primary_tag_name_for(english.reload, 'en')).to eq(english_name)
+        expect(primary_tag_name_for(ainu.reload, 'ain')).to eq(ainu_name)
       end
     end
 

backend/spec/models/tag_name_spec.rb

@@ -1,17 +1,16 @@
 require 'rails_helper'
 
 RSpec.describe TagName, type: :model do
-  include_context 'English locale'
+  include_context 'Ainu locale'
 
   it 'allows the same name in different languages' do
-    pending '日本語以外の Locale 有効化は別課題で実装する'
     locale
     create(:tag_name, name: 'shared_name')
-    english = build(:tag_name, name: 'shared_name',
-                              language_code: 'en', script_code: 'Latn')
+    ainu = build(:tag_name, name: 'shared_name',
+                              language_code: 'ain', script_code: 'Kana')
 
-    expect(english).to be_valid
-    expect { english.save! }.to change(described_class, :count).by(1)
+    expect(ainu).to be_valid
+    expect { ainu.save! }.to change(described_class, :count).by(1)
   end
 
   it 'rejects a duplicate name within the same language' do
@@ -67,11 +66,10 @@ RSpec.describe TagName, type: :model do
   end
 
   it 'completes an ordinary tag factory under future active languages' do
-    pending '日本語以外の Locale 有効化は別課題で実装する'
     locale
     tag = create(:tag, primary_name: 'future_factory')
 
-    expect(TagName.where(tag:, language_code: 'en', primary_flg: true))
+    expect(TagName.where(tag:, language_code: 'ain', primary_flg: true))
         .to contain_exactly(have_attributes(auto_generated: true))
   end
 
@@ -114,46 +112,44 @@ RSpec.describe TagName, type: :model do
     end
 
     it 'resolves the primary name of the alias language on the same tag' do
-      pending '日本語以外の Locale 有効化は別課題で実装する'
       locale
       tag = create(:tag, primary_name: '日本語正本')
-      english_primary = primary_tag_name_for(tag, 'en')
-      english_primary.update!(name: 'english_primary', auto_generated: false)
-      english_alias = create(:tag_name, :alias, tag:, name: 'english_alias',
-                                                 language_code: 'en', script_code: 'Latn')
+      ainu_primary = primary_tag_name_for(tag, 'ain')
+      ainu_primary.update!(name: 'ainu_primary', auto_generated: false)
+      ainu_alias = create(:tag_name, :alias, tag:, name: 'ainu_alias',
+                                                 language_code: 'ain', script_code: 'Kana')
       representative_id = tag.tag_name('ja')&.id
 
-      primary = described_class.find_by!(tag_id: english_alias.tag_id,
-                                         language_code: english_alias.language_code,
+      primary = described_class.find_by!(tag_id: ainu_alias.tag_id,
+                                         language_code: ainu_alias.language_code,
                                          primary_flg: true)
 
-      expect(primary).to eq(english_primary)
-      expect(described_class.canonicalise(locale, [english_alias.name]))
-          .to eq([english_primary.name])
+      expect(primary).to eq(ainu_primary)
+      expect(described_class.canonicalise(locale, [ainu_alias.name]))
+          .to eq([ainu_primary.name])
       expect(tag.reload.tag_name('ja')&.id).to eq(representative_id)
     end
 
     it 'resolves only aliases in the requested language' do
-      pending '日本語以外の Locale 有効化は別課題で実装する'
       locale
       nipponese = create(:tag, primary_name: 'nipponese_canonical')
-      english_name = create(:tag_name, name: 'english_canonical',
-                                      language_code: 'en', script_code: 'Latn')
-      english = create(:tag, primary_tag_name: english_name)
+      ainu_name = create(:tag_name, name: 'ainu_canonical',
+                                      language_code: 'ain', script_code: 'Kana')
+      ainu = create(:tag, primary_tag_name: ainu_name)
       nipponese_alias = create(:tag_name, :alias, name: 'shared_alias',
                                                   tag: nipponese)
-      english_alias = create(:tag_name, :alias, name: 'shared_alias',
-                                                tag: english,
-                                                language_code: 'en', script_code: 'Latn')
+      ainu_alias = create(:tag_name, :alias, name: 'shared_alias',
+                                                tag: ainu,
+                                                language_code: 'ain', script_code: 'Kana')
 
       expect(nipponese_alias.reload).to have_attributes(
           tag_id: nipponese.id,
           primary_flg: false, language_code: 'ja')
-      expect(english_alias.reload).to have_attributes(
-          tag_id: english.id,
-          primary_flg: false, language_code: 'en')
+      expect(ainu_alias.reload).to have_attributes(
+          tag_id: ainu.id,
+          primary_flg: false, language_code: 'ain')
       expect(described_class.canonicalise(locale, ['shared_alias']))
-          .to eq(['english_canonical'])
+          .to eq(['ainu_canonical'])
       expect(described_class.canonicalise(Locale.nipponese, ['shared_alias']))
           .to eq(['nipponese_canonical'])
     end

backend/spec/models/tag_spec.rb

@@ -8,7 +8,7 @@ RSpec.describe Tag, type: :model do
     it 'checks the requested language and treats an empty description as present' do
       TagDescription.create!(tag:, language_code: 'ja', body: '', version_no: 1)
       expect(tag.has_description?(language_code: 'ja')).to be(true)
-      expect(tag.has_description?(language_code: 'en')).to be(false)
+      expect(tag.has_description?(language_code: 'ain')).to be(false)
     end
 
     it 'returns false without a description' do
@@ -23,16 +23,16 @@ RSpec.describe Tag, type: :model do
       subscriber = ->(*args) { queries << args.last.fetch(:sql) }
       ActiveSupport::Notifications.subscribed(subscriber, 'sql.active_record') do
         expect(loaded.has_description?(language_code: 'ja')).to be(true)
-        expect(loaded.has_description?(language_code: 'en')).to be(false)
+        expect(loaded.has_description?(language_code: 'ain')).to be(false)
       end
       expect(queries).to be_empty
     end
 
     it 'keeps language selection generic without enabling another Language record' do
       tag.association(:tag_descriptions).target = [
-          TagDescription.new(tag:, language_code: 'en', body: '', version_no: 1)]
+          TagDescription.new(tag:, language_code: 'ain', body: '', version_no: 1)]
       tag.association(:tag_descriptions).loaded!
-      expect(tag.has_description?(language_code: 'en')).to be(true)
+      expect(tag.has_description?(language_code: 'ain')).to be(true)
       expect(tag.has_description?(language_code: 'ja')).to be(false)
     end
   end
@@ -61,33 +61,32 @@ RSpec.describe Tag, type: :model do
   end
 
   describe '.normalise_tags!' do
-    include_context 'English locale'
+    include_context 'Ainu locale'
 
     it 'canonicalises aliases in the supplied language only' do
-      pending '日本語以外の Locale 有効化は別課題で実装する'
-      prepare_english_reference!
+      prepare_ainu_reference!
       nipponese = create(:tag, primary_name: 'nipponese_canonical')
-      english_name = create(:tag_name, name: 'english_canonical',
-                                      language_code: 'en', script_code: 'Latn')
-      english = create(:tag, primary_tag_name: english_name)
-      primary_tag_name_for(english, 'ja').update!(
-          name: 'english_in_nipponese', auto_generated: false)
-      english_locale = locale
+      ainu_name = build(:tag_name, tag: nil, name: 'ainu_canonical',
+                                      language_code: 'ain', script_code: 'Kana')
+      ainu = create(:tag, primary_tag_name: ainu_name)
+      primary_tag_name_for(ainu, 'ja').update!(
+          name: 'ainu_in_nipponese', auto_generated: false)
+      ainu_locale = locale
       nipponese_alias = create(:tag_name, :alias, name: 'shared_alias',
                                                   tag: nipponese)
-      english_alias = create(:tag_name, :alias, name: 'shared_alias',
-                                                tag: english,
-                                                language_code: 'en', script_code: 'Latn')
+      ainu_alias = create(:tag_name, :alias, name: 'shared_alias',
+                                                tag: ainu,
+                                                language_code: 'ain', script_code: 'Kana')
 
       expect(nipponese_alias.reload).to have_attributes(
           tag_id: nipponese.id,
           primary_flg: false, language_code: 'ja')
-      expect(english_alias.reload).to have_attributes(
-          tag_id: english.id,
-          primary_flg: false, language_code: 'en')
+      expect(ainu_alias.reload).to have_attributes(
+          tag_id: ainu.id,
+          primary_flg: false, language_code: 'ain')
       expect(described_class.normalise_tags!(
-          english_locale, ['shared_alias'],
-          with_tagme: false, with_no_deerjikist: false)).to eq([english])
+          ainu_locale, ['shared_alias'],
+          with_tagme: false, with_no_deerjikist: false)).to eq([ainu])
       expect(described_class.normalise_tags!(
           Locale.nipponese, ['shared_alias'],
           with_tagme: false, with_no_deerjikist: false)).to eq([nipponese])
@@ -253,129 +252,120 @@ RSpec.describe Tag, type: :model do
 
   describe '.find_or_create_by_tag_name!' do
     context 'with an explicit locale' do
-      include_context 'English locale'
+      include_context 'Ainu locale'
 
       it 'creates the representative name with locale attributes and ownership' do
-        pending '日本語以外の Locale 有効化は別課題で実装する'
         locale
         tag = described_class.find_or_create_by_tag_name!(
-            locale, 'english_name', category: :character)
+            locale, 'ainu_name', category: :character)
 
-        expect(primary_tag_name_for(tag, 'en')).to have_attributes(
-            language_code: 'en', script_code: 'Latn',
+        expect(primary_tag_name_for(tag, 'ain')).to have_attributes(
+            language_code: 'ain', script_code: 'Kana',
             primary_flg: true, tag_id: tag.id)
         expect(tag.category).to eq('character')
       end
 
-      it 'uses the English primary as the source for a generated Nipponese name' do
-        pending '日本語以外の Locale 有効化は別課題で実装する'
+      it 'copies an Ainu-origin name to Japanese without reverse transcription' do
         locale
-        allow(TagName).to receive(:generate_name).and_return('generated_nipponese')
+        allow(TagName).to receive(:generate_name).and_call_original
 
         tag = described_class.find_or_create_by_tag_name!(
-            locale, 'english_origin', category: :general)
+            locale, 'ainu_origin', category: :general)
 
-        expect(TagName.where(tag:, language_code: 'en', primary_flg: true))
+        expect(TagName.where(tag:, language_code: 'ain', primary_flg: true))
             .to contain_exactly(have_attributes(
-                name: 'english_origin', auto_generated: false))
+                name: 'ainu_origin', auto_generated: false))
         expect(TagName.where(tag:, language_code: 'ja', primary_flg: true))
             .to contain_exactly(have_attributes(
-                name: 'generated_nipponese', auto_generated: true))
-        source_tag_name = TagName.find_by!(tag:, language_code: 'en', primary_flg: true)
+                name: 'ainu_origin', auto_generated: true))
         expect(TagName).to have_received(:generate_name)
-            .with(Locale.nipponese, tag, source_tag_name)
+            .with(Locale.nipponese, tag, tag.tag_name('ain'))
       end
 
       it 'gives a new tag one primary name for every active language' do
-        pending '日本語以外の Locale 有効化は別課題で実装する'
         locale
         tag = described_class.find_or_create_by_tag_name!(
             Locale.nipponese, 'new_multilingual_tag', category: :general)
 
         expect(TagName.where(tag:, language_code: 'ja', primary_flg: true).count).to eq(1)
-        expect(TagName.where(tag:, language_code: 'en', primary_flg: true).count).to eq(1)
+        expect(TagName.where(tag:, language_code: 'ain', primary_flg: true).count).to eq(1)
       end
 
-      it 'creates one primary per language when multiple locales use English' do
-        pending '日本語以外の Locale 有効化は別課題で実装する'
+      it 'creates one primary per language when multiple locales use Ainu' do
         locale
         described_class.find_or_create_by_tag_name!(
-            locale, 'before_second_english_locale', category: :general)
-        Locale.create!(code: 'en-x-rspec', language_code: 'en',
-                       script_code: 'Latn', region_code: 826,
-                       variants: 'x-rspec', name: 'English')
+            locale, 'before_second_ainu_locale', category: :general)
 
         tag = described_class.find_or_create_by_tag_name!(
-            locale, 'one_english_primary', category: :general)
+            locale, 'one_ainu_primary', category: :general)
+        TagNameCompletion.for_tag!(tag, locales: [locale, locale.dup, Locale.nipponese])
 
-        expect(TagName.where(tag:, language_code: 'en', primary_flg: true).count).to eq(1)
+        expect(TagName.where(tag:, language_code: 'ain', primary_flg: true).count).to eq(1)
         expect(TagName.where(tag:, language_code: 'ja', primary_flg: true).count).to eq(1)
       end
 
       it 'rolls back a new tag and requested name if name generation fails' do
-        pending '日本語以外の Locale 有効化は別課題で実装する'
         locale
         original_tag_count = described_class.count
         allow(TagName).to receive(:generate_name).and_raise('generation failed')
 
         expect {
           described_class.find_or_create_by_tag_name!(
-              locale, 'atomic_english_name', category: :general)
+              locale, 'atomic_ainu_name', category: :general)
         }.to raise_error('generation failed')
 
         expect(described_class.count).to eq(original_tag_count)
-        expect(TagName.where(language_code: 'en', name: 'atomic_english_name')).to be_empty
+        expect(TagName.where(language_code: 'ain', name: 'atomic_ainu_name')).to be_empty
         expect(described_class.joins(:tag_names)
-            .where(tag_names: { name: 'atomic_english_name' })).to be_empty
+            .where(tag_names: { name: 'atomic_ainu_name' })).to be_empty
       end
 
 
 
       it 'creates separate tag identities for the same name in different languages' do
-        pending '日本語以外の Locale 有効化は別課題で実装する'
         locale
         nipponese = described_class.find_or_create_by_tag_name!(
             Locale.nipponese, 'same_name', category: :general)
-        english = described_class.find_or_create_by_tag_name!(
+        primary_tag_name_for(nipponese, 'ain').update!(
+            name: 'other_ainu_name', auto_generated: false)
+        ainu = described_class.find_or_create_by_tag_name!(
             locale, 'same_name', category: :character)
 
-        expect(english).not_to eq(nipponese)
-        expect(primary_tag_name_for(english, 'en')).to have_attributes(
-            name: 'same_name', tag_id: english.id, language_code: 'en', primary_flg: true)
+        expect(ainu).not_to eq(nipponese)
+        expect(primary_tag_name_for(ainu, 'ain')).to have_attributes(
+            name: 'same_name', tag_id: ainu.id, language_code: 'ain', primary_flg: true)
         expect(primary_tag_name_for(nipponese, 'ja')).to have_attributes(
             name: 'same_name', tag_id: nipponese.id, language_code: 'ja', primary_flg: true)
         expect(described_class.find_or_create_by_tag_name!(
-            locale, 'same_name', category: :general)).to eq(english)
+            locale, 'same_name', category: :general)).to eq(ainu)
         expect(described_class.find_or_create_by_tag_name!(
             Locale.nipponese, 'same_name', category: :general)).to eq(nipponese)
       end
 
       it 'preserves the V1 representative when looking up another primary language' do
-        pending '日本語以外の Locale 有効化は別課題で実装する'
         locale
         tag = create(:tag, primary_name: '日本語代表名')
         representative_id = tag.tag_name('ja')&.id
-        english = primary_tag_name_for(tag, 'en')
-        english.update!(name: 'english_primary', auto_generated: false)
+        ainu = primary_tag_name_for(tag, 'ain')
+        ainu.update!(name: 'ainu_primary', auto_generated: false)
 
         found = described_class.find_or_create_by_tag_name!(
-            locale, english.name, category: :general)
+            locale, ainu.name, category: :general)
 
         expect(found).to eq(tag)
         expect(tag.reload.tag_name('ja')&.id).to eq(representative_id)
-        expect(english.reload.tag_id).to eq(tag.id)
+        expect(ainu.reload.tag_id).to eq(tag.id)
       end
 
       it 'normalises names using the supplied locale' do
-        pending '日本語以外の Locale 有効化は別課題で実装する'
         locale
         tags = described_class.normalise_tags!(
-            locale, ['character:normalised_english'],
+            locale, ['character:normalised_ainu'],
             with_tagme: false, with_no_deerjikist: false)
 
         expect(tags.length).to eq(1)
-        expect(primary_tag_name_for(tags.first, 'en')).to have_attributes(
-            name: 'normalised_english', language_code: 'en', script_code: 'Latn',
+        expect(primary_tag_name_for(tags.first, 'ain')).to have_attributes(
+            name: 'normalised_ainu', language_code: 'ain', script_code: 'Kana',
             primary_flg: true, tag_id: tags.first.id)
       end
     end
@@ -444,26 +434,25 @@ RSpec.describe Tag, type: :model do
     end
 
     context 'with names in multiple languages' do
-      include_context 'English locale'
+      include_context 'Ainu locale'
 
       it 'keeps the target primary and moves source names as aliases' do
-        pending '日本語以外の Locale 有効化は別課題で実装する'
         locale
-        english_primary = primary_tag_name_for(target_tag, 'en')
-        source_primary = primary_tag_name_for(source_tag, 'en')
+        ainu_primary = primary_tag_name_for(target_tag, 'ain')
+        source_primary = primary_tag_name_for(source_tag, 'ain')
         source_alias = create(:tag_name, :alias, tag: source_tag,
-            name: 'source_english_alias', language_code: 'en', script_code: 'Latn')
+            name: 'source_ainu_alias', language_code: 'ain', script_code: 'Kana')
 
-        expect([english_primary, source_primary]).to all(have_attributes(
+        expect([ainu_primary, source_primary]).to all(have_attributes(
             primary_flg: true, auto_generated: true))
 
         described_class.merge_tags!(target_tag, [source_tag])
 
-        expect(primary_tag_name_for(target_tag.reload, 'en')).to eq(english_primary)
-        expect(TagName.where(tag: target_tag, language_code: 'en', primary_flg: true))
-            .to contain_exactly(english_primary)
+        expect(primary_tag_name_for(target_tag.reload, 'ain')).to eq(ainu_primary)
+        expect(TagName.where(tag: target_tag, language_code: 'ain', primary_flg: true))
+            .to contain_exactly(ainu_primary)
         expect([source_primary.reload, source_alias.reload]).to all(have_attributes(
-            tag_id: target_tag.id, language_code: 'en', primary_flg: false))
+            tag_id: target_tag.id, language_code: 'ain', primary_flg: false))
         expect(TagName.where(tag: target_tag, language_code: 'ja', primary_flg: true))
             .to contain_exactly(primary_tag_name_for(target_tag, 'ja'))
         expect(source_tag_name.reload).to have_attributes(

backend/spec/rails_helper.rb

@@ -53,6 +53,14 @@ RSpec.configure do |config|
   config.include AuthHelper, type: :request
   config.include JsonHelper, type: :request
 
+  config.around(:each, type: :request) do |example|
+    previous = ApplicationController.allow_forgery_protection
+    ApplicationController.allow_forgery_protection = example.metadata.fetch(:csrf, false)
+    example.run
+  ensure
+    ApplicationController.allow_forgery_protection = previous
+  end
+
   # Remove this line if you're not using ActiveRecord or ActiveRecord fixtures
   config.fixture_paths = [
     Rails.root.join('spec/fixtures')

backend/spec/requests/counts_spec.rb

@@ -0,0 +1,96 @@
+require 'rails_helper'
+
+RSpec.describe 'Counts API', type: :request do
+  let!(:actor) { create(:user, :member) }
+  let!(:post) { create(:post) }
+  let!(:tag) { create(:tag, primary_name: 'counts tag', category: :general) }
+
+  before do
+    snapshot = { tag_id: tag.id, version_no: 1, name: 'counts tag',
+                 category: 'general', sections: [] }
+    [1, 2, 3].each do |number|
+      time = Time.utc(2024, number == 3 ? 2 : 1, number, 0, 0)
+      PostVersion.create!(post:, version_no: number,
+          event_type: number == 1 ? 'create' : 'update',
+          tags: '', url: post.url, title: "Snapshot #{ number }", parent_post_ids: '',
+          tags_json: number == 1 ? [snapshot] : [],
+          created_by_user: number == 3 ? nil : actor, created_at: time)
+      TagVersion.create!(tag:, version_no: number,
+          event_type: number == 1 ? 'create' : 'update',
+          name: 'counts tag', category: 'general', aliases: '', parent_tag_ids: '',
+          names: { ja: { name: 'counts tag', script_code: 'Jpan',
+                         auto_generated: false, aliases: [] } },
+          created_by_user: number == 3 ? nil : actor, created_at: time)
+    end
+  end
+
+  ['posts', 'tags'].each do |resource|
+    context resource do
+      let(:path) { "/counts/#{ resource }" }
+      let(:id) { resource == 'posts' ? post.id : tag.id }
+      let(:filters) { { resource_id: id, user_id: actor.id,
+                       from: '2024-01-01T00:00Z', before: '2024-02-01T00:00Z' } }
+
+      it 'uses the same AND filters for SQL totals, groups and details' do
+        get path, params: filters.merge(axis: 'event_type')
+        expect(response).to have_http_status(:ok)
+        summary = response.parsed_body
+        expect(summary['count']).to eq(2)
+        expect(summary['groups'].sum { _1['count'] }).to eq(2)
+        expect(summary['groups'].map { _1['key'] }).to eq(['create', 'update'])
+
+        get path, params: filters.merge(mode: 'details')
+        expect(response.parsed_body['count']).to eq(2)
+        expect(response.parsed_body['versions'].map { _1['version_no'] }).to eq([2, 1])
+      end
+
+      it 'paginates details and groups independently from totals' do
+        get path, params: { resource_id: id, mode: 'details', limit: 1, page: 2 }
+        expect(response.parsed_body['count']).to eq(3)
+        expect(response.parsed_body['versions'].sole['version_no']).to eq(2)
+        get path, params: { resource_id: id, axis: 'month', limit: 1, page: 2 }
+        expect(response.parsed_body['group_count']).to eq(2)
+        expect(response.parsed_body['groups'].sole).to include('key' => '2024-02', 'count' => 1)
+      end
+
+      it 'groups null actors and supports their drill-down filter' do
+        get path, params: { resource_id: id, axis: 'user' }
+        expect(response.parsed_body['groups']).to include(
+            { 'key' => nil, 'name' => nil, 'count' => 1 })
+        get path, params: { resource_id: id, mode: 'details', user_id: 'none' }
+        expect(response.parsed_body['count']).to eq(1)
+      end
+
+      it 'uses an inclusive start and exclusive end' do
+        get path, params: { resource_id: id,
+                            from: '2024-01-01T00:00Z', before: '2024-01-02T00:00Z' }
+        expect(response.parsed_body['count']).to eq(1)
+      end
+
+      it 'rejects unsupported or malformed query values' do
+        [
+            { axis: 'SQL' }, { limit: 101 }, { page: '1x' }, { user_id: '-1' },
+            { event_type: 'invalid' }, { columns: 'password' }, { order: 'id' },
+            { from: '2024-02-30T00:00Z' }, { from: '2024-01-01' },
+            { user_id: ['1'] }, { mode: 'invalid' }].each do |invalid|
+          get path, params: invalid
+          expect(response).to have_http_status(:bad_request)
+        end
+      end
+
+      it 'retains the existing banned-user boundary' do
+        actor.update!(banned_at: Time.current)
+        sign_in_as(actor)
+        get path
+        expect(response).to have_http_status(:forbidden)
+      end
+    end
+  end
+
+  it 'matches removed tags from the previous snapshot, not current post_tags' do
+    get '/counts/posts', params: { tag: tag.id, mode: 'details' }
+    expect(response.parsed_body['count']).to eq(2)
+    expect(response.parsed_body['versions'].map { _1['version_no'] }).to eq([2, 1])
+    expect(response.parsed_body['versions'].first['tags'].sole['type']).to eq('removed')
+  end
+end

backend/spec/requests/locale_resolution_spec.rb

@@ -0,0 +1,54 @@
+require 'rails_helper'
+
+RSpec.describe 'API locale resolution', type: :request do
+  let!(:tag) { create(:tag, primary_name: '日本語正本') }
+
+  it 'defaults an omitted locale to Japanese' do
+    get "/tags/#{ tag.id }"
+
+    expect(response).to have_http_status(:ok)
+    expect(json.fetch('name')).to eq('日本語正本')
+  end
+
+  it 'accepts an explicitly requested active Japanese locale' do
+    get "/tags/#{ tag.id }", params: { locale: 'ja' }
+
+    expect(response).to have_http_status(:ok)
+    expect(json.fetch('name')).to eq('日本語正本')
+  end
+
+  ['', 'en', 'ain', 'Jpan', 'JA', 'unknown', ['ja']].each do |code|
+    it "rejects invalid locale #{ code.inspect } instead of defaulting to Japanese" do
+      get "/tags/#{ tag.id }", params: { locale: code }
+
+      expect(response).to have_http_status(:not_found)
+      expect(response.body).not_to include('日本語正本')
+    end
+  end
+
+  it 'rejects a supported locale that has not been registered' do
+    get "/tags/#{ tag.id }", params: { locale: 'ain-Kana' }
+
+    expect(response).to have_http_status(:not_found)
+  end
+
+  it 'rejects an inactive locale' do
+    Locale.nipponese.update!(deprecated_at: Time.current)
+
+    get "/tags/#{ tag.id }", params: { locale: 'ja' }
+
+    expect(response).to have_http_status(:not_found)
+  end
+
+  it 'does not write posts or tag names under an invalid locale' do
+    sign_in_as(create_member_user!)
+
+    expect do
+      post '/posts', params: {
+          locale: 'en', title: 'invalid locale', url: 'https://example.com/invalid-locale',
+          tags: 'unwritten_tag' }
+    end.to change(Post, :count).by(0).and change(TagName, :count).by(0)
+
+    expect(response).to have_http_status(:not_found)
+  end
+end

backend/spec/requests/locale_write_paths_spec.rb

@@ -1,7 +1,7 @@
 require 'rails_helper'
 
 RSpec.describe 'Locale propagation on write paths', type: :request do
-  include_context 'English locale'
+  include_context 'Ainu locale'
 
   let(:member) { create(:user, :member) }
 
@@ -14,7 +14,19 @@ RSpec.describe 'Locale propagation on write paths', type: :request do
     expect(tag_name).to have_attributes(
         script_code: expected_locale.script_code, primary_flg: true)
     expect(tag_name.tag_id).to be_present
-    tag_name.tag
+    tag = tag_name.tag
+    version = tag.tag_versions.sole
+    expect(version).to have_attributes(
+        event_type: 'create', version_no: 1, created_by_user_id: member.id)
+    expect(tag.reload.version_no).to eq(1)
+    expect(version.names.keys).to match_array(
+        Locale.where(deprecated_at: nil).distinct.pluck(:language_code))
+    tag.tag_names.where(primary_flg: true).each do |primary|
+      expect(version.names.fetch(primary.language_code)).to include(
+          'name' => primary.name, 'script_code' => primary.script_code,
+          'auto_generated' => primary.auto_generated, 'aliases' => [])
+    end
+    tag
   end
 
   it 'confirms a generated Nipponese primary when a human renames it' do
@@ -54,13 +66,12 @@ RSpec.describe 'Locale propagation on write paths', type: :request do
     end
   end
 
-  ['en', nil].each do |requested_locale|
+  ['ain-Kana', nil].each do |requested_locale|
     context "with locale #{ requested_locale.inspect }" do
       let(:locale_params) { requested_locale ? { locale: requested_locale } : { } }
       let(:expected_locale) { requested_locale ? locale : Locale.nipponese }
 
       it 'creates post tags in the requested language or Nipponese fallback' do
-        pending '日本語以外の Locale 有効化は別課題で実装する' if requested_locale
         locale if requested_locale
         post '/posts', params: locale_params.merge(
             title: 'Locale post', url: 'https://example.com/locale-post',
@@ -72,7 +83,6 @@ RSpec.describe 'Locale propagation on write paths', type: :request do
       end
 
       it 'updates post tags in the requested language or Nipponese fallback' do
-        pending '日本語以外の Locale 有効化は別課題で実装する' if requested_locale
         locale if requested_locale
         record = create(:post)
         PostVersionRecorder.record!(post: record, event_type: :create, created_by_user: member)
@@ -87,7 +97,6 @@ RSpec.describe 'Locale propagation on write paths', type: :request do
       end
 
       it 'passes the resolved locale to bulk creation' do
-        pending '日本語以外の Locale 有効化は別課題で実装する' if requested_locale
         locale if requested_locale
         # Worker propagation is exercised in post_bulk_creator_spec.
         expect_any_instance_of(PostBulkCreator).to receive(:run)
@@ -102,7 +111,6 @@ RSpec.describe 'Locale propagation on write paths', type: :request do
       end
 
       it 'creates materials with tags in the resolved locale' do
-        pending '日本語以外の Locale 有効化は別課題で実装する' if requested_locale
         locale if requested_locale
         post '/materials', params: locale_params.merge(
             tag: 'locale_material', url: 'https://example.com/material')
@@ -113,7 +121,6 @@ RSpec.describe 'Locale propagation on write paths', type: :request do
       end
 
       it 'updates materials with tags in the resolved locale' do
-        pending '日本語以外の Locale 有効化は別課題で実装する' if requested_locale
         locale if requested_locale
         tag = create(:tag, category: :material)
         material = Material.create!(tag:, url: 'https://example.com/material')
@@ -127,7 +134,6 @@ RSpec.describe 'Locale propagation on write paths', type: :request do
       end
 
       it 'links Nico external tags to internal tags in the resolved locale' do
-        pending '日本語以外の Locale 有効化は別課題で実装する' if requested_locale
         locale if requested_locale
         external = create(:external_tag)
         NicoTagVersionRecorder.record!(
@@ -141,7 +147,6 @@ RSpec.describe 'Locale propagation on write paths', type: :request do
       end
 
       it 'creates parent tags in the resolved locale' do
-        pending '日本語以外の Locale 有効化は別課題で実装する' if requested_locale
         locale if requested_locale
         tag = create(:tag)
 
@@ -157,184 +162,179 @@ RSpec.describe 'Locale propagation on write paths', type: :request do
   end
 
   context 'with existing names in both languages' do
-    let(:english_name) do
-      create(:tag_name, name: 'shared_name', language_code: 'en', script_code: 'Latn')
+    let(:ainu_name) do
+      create(:tag_name, name: 'shared_name', language_code: 'ain', script_code: 'Kana')
+    end
+    let(:ainu_tag) do
+      create(:tag, primary_tag_name: ainu_name, category: :material).tap do |tag|
+        primary_tag_name_for(tag, 'ja').update!(name: 'ainu_in_japanese', auto_generated: false)
+      end
     end
-    let(:english_tag) { create(:tag, primary_tag_name: english_name, category: :material) }
     let(:nipponese_tag) do
       create(:tag, primary_name: 'temporary_nipponese', category: :general).tap do |tag|
-        # Isolate lookup from the separately tested uniqueness validation.
-        primary_tag_name_for(tag, 'ja').update_columns(name: 'shared_name')
+        primary_tag_name_for(tag, 'ja').update!(name: 'shared_name')
       end
     end
 
-    it 'plans and creates the post using the English identity and category' do
-      pending '日本語以外の Locale 有効化は別課題で実装する'
+    it 'plans and creates the post using the Ainu identity and category' do
       locale
-      english_tag
+      ainu_tag
       nipponese_tag
       post '/posts', params: {
-          locale: 'en', title: 'English identity',
-          url: 'https://example.com/english-identity', tags: 'shared_name', parent_post_ids: '' }
+          locale: 'ain-Kana', title: 'Ainu identity',
+          url: 'https://example.com/ainu-identity', tags: 'shared_name', parent_post_ids: '' }
 
       expect(response).to have_http_status(:created), response.body
       record = Post.find(json.fetch('id'))
-      expect(record.tags).to include(english_tag)
+      expect(record.tags).to include(ainu_tag)
       expect(record.tags).not_to include(nipponese_tag)
-      expect(english_tag.reload.category).to eq('material')
+      expect(ainu_tag.reload.category).to eq('material')
       expect(nipponese_tag.reload.category).to eq('general')
     end
 
-    it 'updates the post using the English identity' do
-      pending '日本語以外の Locale 有効化は別課題で実装する'
+    it 'updates the post using the Ainu identity' do
       locale
-      english_tag
+      ainu_tag
       nipponese_tag
       record = create(:post)
       PostVersionRecorder.record!(post: record, event_type: :create, created_by_user: member)
 
       put "/posts/#{ record.id }", params: {
-          locale: 'en', title: record.title, tags: 'shared_name', parent_post_ids: '',
+          locale: 'ain-Kana', title: record.title, tags: 'shared_name', parent_post_ids: '',
           base_version_no: record.reload.version_no }
 
       expect(response).to have_http_status(:ok), response.body
-      expect(record.reload.tags).to include(english_tag)
+      expect(record.reload.tags).to include(ainu_tag)
       expect(record.tags).not_to include(nipponese_tag)
     end
 
-    it 'resolves the English material tag' do
-      pending '日本語以外の Locale 有効化は別課題で実装する'
+    it 'resolves the Ainu material tag' do
       locale
-      english_tag
+      ainu_tag
       nipponese_tag
       post '/materials', params: {
-          locale: 'en', tag: 'shared_name', url: 'https://example.com/english-material' }
+          locale: 'ain-Kana', tag: 'shared_name', url: 'https://example.com/ainu-material' }
 
       expect(response).to have_http_status(:created), response.body
-      expect(Material.find(json.fetch('id')).tag).to eq(english_tag)
+      expect(Material.find(json.fetch('id')).tag).to eq(ainu_tag)
       expect(Material.where(tag: nipponese_tag)).to be_empty
     end
 
-    it 'resolves the English parent tag' do
-      pending '日本語以外の Locale 有効化は別課題で実装する'
+    it 'resolves the Ainu parent tag' do
       locale
-      english_tag
+      ainu_tag
       nipponese_tag
       child = create(:tag)
 
       put "/tags/#{ child.id }", params: {
-          locale: 'en', name: primary_tag_name_for(child, 'ja').name,
+          locale: 'ain-Kana', name: primary_tag_name_for(child, 'ja').name,
           category: child.category, deprecated: false,
           aliases: '', parent_tags: 'shared_name' }
 
       expect(response).to have_http_status(:ok), response.body
-      expect(TagImplication.where(tag: child).pluck(:parent_tag_id)).to eq([english_tag.id])
+      expect(TagImplication.where(tag: child).pluck(:parent_tag_id)).to eq([ainu_tag.id])
     end
 
-    it 'resolves the English internal tag for a Nico link' do
-      pending '日本語以外の Locale 有効化は別課題で実装する'
+    it 'resolves the Ainu internal tag for a Nico link' do
       locale
-      english_tag
+      ainu_tag
       nipponese_tag
       external = create(:external_tag)
       NicoTagVersionRecorder.record!(
           external_tag: external, event_type: :create, created_by_user: member)
 
-      put "/tags/nico/#{ external.id }", params: { locale: 'en', tags: 'shared_name' }
+      put "/tags/nico/#{ external.id }", params: { locale: 'ain-Kana', tags: 'shared_name' }
 
       expect(response).to have_http_status(:ok), response.body
-      expect(external.reload.linked_tags).to contain_exactly(english_tag)
+      expect(external.reload.linked_tags).to contain_exactly(ainu_tag)
     end
   end
 
-  context 'when renaming or updating aliases in English' do
-    let(:english_name) do
-      create(:tag_name, name: 'english_original', language_code: 'en', script_code: 'Latn')
+  context 'when renaming or updating aliases in Ainu' do
+    let(:ainu_name) do
+      create(:tag_name, name: 'ainu_original', language_code: 'ain', script_code: 'Kana')
     end
-    let(:tag) { create(:tag, primary_tag_name: english_name) }
+    let(:tag) { create(:tag, primary_tag_name: ainu_name) }
 
     it 'marks a human-renamed generated primary as no longer auto-generated' do
-      pending '日本語以外の Locale 有効化は別課題で実装する'
       locale
       generated_tag = create(:tag, primary_name: 'rename_generated_source')
-      generated_name = primary_tag_name_for(generated_tag, 'en')
+      generated_name = primary_tag_name_for(generated_tag, 'ain')
       expect(generated_name.auto_generated).to be(true)
 
       patch "/tags/#{ generated_tag.id }", params: {
-          locale: 'en', name: 'human_english_name' }
+          locale: 'ain-Kana', name: 'human_ainu_name' }
 
       expect(response).to have_http_status(:ok), response.body
       expect(generated_name.reload).to have_attributes(
-          name: 'human_english_name', auto_generated: false)
+          name: 'human_ainu_name', auto_generated: false)
     end
 
     it 'does not steal another tag primary for an alias' do
-      pending '日本語以外の Locale 有効化は別課題で実装する'
       locale
       other_tag = create(:tag, primary_name: 'other_nipponese')
-      other_primary = primary_tag_name_for(other_tag, 'en')
-      other_primary.update!(name: 'other_english_primary', auto_generated: false)
-      create(:tag_name, :alias, tag:, name: 'existing_english_alias',
-                                language_code: 'en', script_code: 'Latn')
-      primary_name_before = primary_tag_name_for(tag, 'en').name
+      other_primary = primary_tag_name_for(other_tag, 'ain')
+      other_primary.update!(name: 'other_ainu_primary', auto_generated: false)
+      create(:tag_name, :alias, tag:, name: 'existing_ainu_alias',
+                                language_code: 'ain', script_code: 'Kana')
+      primary_name_before = primary_tag_name_for(tag, 'ain').name
       aliases_before =
-          tag.tag_names.where(language_code: 'en', primary_flg: false)
+          tag.tag_names.where(language_code: 'ain', primary_flg: false)
               .order(:name).pluck(:name)
       category_before = tag.category
 
       put "/tags/#{ tag.id }", params: {
-          locale: 'en', name: 'renamed_before_alias_collision',
+          locale: 'ain-Kana', name: 'renamed_before_alias_collision',
           category: 'character', deprecated: false,
-          aliases: 'other_english_primary', parent_tags: '' }
+          aliases: 'other_ainu_primary', parent_tags: '' }
 
       aggregate_failures do
         expect(response).to have_http_status(:unprocessable_entity)
         expect(other_primary.reload).to have_attributes(
-            tag_id: other_tag.id, language_code: 'en', primary_flg: true)
-        expect(TagName.where(tag: other_tag, language_code: 'en', primary_flg: true))
+            tag_id: other_tag.id, language_code: 'ain', primary_flg: true)
+        expect(TagName.where(tag: other_tag, language_code: 'ain', primary_flg: true))
             .to contain_exactly(other_primary)
-        expect(primary_tag_name_for(tag.reload, 'en').name).to eq(primary_name_before)
+        expect(primary_tag_name_for(tag.reload, 'ain').name).to eq(primary_name_before)
         expect(tag.category).to eq(category_before)
         aliases_after =
-            tag.tag_names.where(language_code: 'en', primary_flg: false)
+            tag.tag_names.where(language_code: 'ain', primary_flg: false)
                 .order(:name).pluck(:name)
         expect(aliases_after).to eq(aliases_before)
       end
     end
 
     it 'allows a rename to a name already used in Nipponese' do
-      pending '日本語以外の Locale 有効化は別課題で実装する'
       locale
       nipponese = create(:tag, primary_name: 'rename_target')
+      primary_tag_name_for(nipponese, 'ain').update!(
+          name: 'different_ainu_target', auto_generated: false)
 
-      patch "/tags/#{ tag.id }", params: { locale: 'en', name: 'rename_target' }
+      patch "/tags/#{ tag.id }", params: { locale: 'ain-Kana', name: 'rename_target' }
 
       expect(response).to have_http_status(:ok), response.body
-      expect(primary_tag_name_for(tag.reload, 'en')).to have_attributes(
-          name: 'rename_target', language_code: 'en', tag_id: tag.id)
+      expect(primary_tag_name_for(tag.reload, 'ain')).to have_attributes(
+          name: 'rename_target', language_code: 'ain', tag_id: tag.id)
       expect(primary_tag_name_for(nipponese.reload, 'ja')).to have_attributes(
           name: 'rename_target', language_code: 'ja', tag_id: nipponese.id)
     end
 
     it 'creates aliases in the requested language' do
-      pending '日本語以外の Locale 有効化は別課題で実装する'
       locale
       put "/tags/#{ tag.id }", params: {
-          locale: 'en', name: english_name.name,
+          locale: 'ain-Kana', name: ainu_name.name,
           category: tag.category, deprecated: false,
-          aliases: 'english_alias', parent_tags: '' }
+          aliases: 'ainu_alias', parent_tags: '' }
 
       expect(response).to have_http_status(:ok), response.body
-      expect(TagName.find_by!(language_code: 'en', name: 'english_alias'))
+      expect(TagName.find_by!(language_code: 'ain', name: 'ainu_alias'))
           .to have_attributes(
-              script_code: 'Latn',
-              tag_id: tag.id, primary_flg: false, language_code: 'en')
-      primary = TagName.find_by!(tag_id: tag.id, language_code: 'en', primary_flg: true)
-      expect(primary).to have_attributes(name: 'english_original', script_code: 'Latn')
+              script_code: 'Kana',
+              tag_id: tag.id, primary_flg: false, language_code: 'ain')
+      primary = TagName.find_by!(tag_id: tag.id, language_code: 'ain', primary_flg: true)
+      expect(primary).to have_attributes(name: 'ainu_original', script_code: 'Kana')
     end
 
     it 'does not take an alias from another language' do
-      pending '日本語以外の Locale 有効化は別課題で実装する'
       locale
       nipponese = create(:tag, primary_name: 'nipponese_owner')
       nipponese_alias = create(:tag_name, :alias, name: 'shared_alias',
@@ -344,7 +344,7 @@ RSpec.describe 'Locale propagation on write paths', type: :request do
           primary_flg: false, language_code: 'ja')
 
       put "/tags/#{ tag.id }", params: {
-          locale: 'en', name: english_name.name,
+          locale: 'ain-Kana', name: ainu_name.name,
           category: tag.category, deprecated: false,
           aliases: 'shared_alias', parent_tags: '' }
 
@@ -352,12 +352,12 @@ RSpec.describe 'Locale propagation on write paths', type: :request do
       expect(nipponese_alias.reload).to have_attributes(
           tag_id: nipponese.id,
           primary_flg: false, language_code: 'ja')
-      expect(TagName.find_by!(language_code: 'en', name: 'shared_alias'))
+      expect(TagName.find_by!(language_code: 'ain', name: 'shared_alias'))
           .to have_attributes(
-              tag_id: tag.id, script_code: 'Latn',
-              primary_flg: false, language_code: 'en')
+              tag_id: tag.id, script_code: 'Kana',
+              primary_flg: false, language_code: 'ain')
       expect(TagName.where(name: 'shared_alias').pluck(:language_code, :tag_id))
-          .to contain_exactly(['ja', nipponese.id], ['en', tag.id])
+          .to contain_exactly(['ja', nipponese.id], ['ain', tag.id])
     end
   end
 end

backend/spec/requests/nico_tags_spec.rb

@@ -231,11 +231,14 @@ RSpec.describe 'NicoTags', type: :request do
         replacement: 'valid'
       )
       nico_tag
+      before_counts = [Tag.count, TagName.count, TagVersion.count]
 
       expect {
         patch "/tags/nico/#{nico_tag.id}", params: { tags: 'created_first invalid' }
       }.not_to change(TagName, :count)
 
+      expect([Tag.count, TagName.count, TagVersion.count]).to eq(before_counts)
+
       expect(response).to have_http_status(:unprocessable_entity)
       expect(json.fetch('errors').fetch('tags')).to include(
           a_string_including('タグ名 “invalid”:', '名前に使用できない文字が含まれてゐます．'))

backend/spec/requests/post_locale_filter_identity_spec.rb

@@ -0,0 +1,44 @@
+require 'rails_helper'
+
+RSpec.describe 'Post filter identity across locales', type: :request do
+  include_context 'Ainu locale'
+
+  let!(:activated_locale) { locale }
+  let!(:tag) { create(:tag, primary_name: 'legacy_union_source') }
+  let!(:external) { create(:external_tag, name: 'shared') }
+  let!(:internal_post) { create(:post) }
+  let!(:external_post) { create(:post) }
+  let!(:other_post) { create(:post) }
+
+  before do
+    # Legacy data can predate the current prohibition on internal nico: names.
+    primary_tag_name_for(tag, 'ja').update_columns(name: 'nico:shared')
+    primary_tag_name_for(tag, 'ain').update!(name: 'シロシ', auto_generated: false)
+    create(:tag_name, :alias, tag:, name: 'union_alias', language_code: 'ja')
+    PostTag.create!(post: internal_post, tag:)
+    PostExternalTag.create!(post: external_post, external_tag: external)
+  end
+
+  ['nico:shared', 'union_alias', 'not:nico:shared'].each do |literal|
+    it "preserves the complete match set for #{ literal }" do
+      get '/posts', params: { locale: 'ja', tags: literal }
+      expect(response).to have_http_status(:ok)
+      original_ids = json.fetch('posts').map { _1.fetch('id') }
+      expected = literal.start_with?('not:') ? [other_post.id] :
+          [internal_post.id, external_post.id]
+      expect(original_ids).to match_array(expected)
+
+      get '/posts/tag_filters', params: {
+          locale: 'ja', target_locale: 'ain-Kana', tags: literal }
+      expect(response).to have_http_status(:ok)
+      references = json.fetch('references')
+      expect(references.first).to include('tag_id' => tag.id, 'external_tag_id' => external.id)
+
+      get '/posts', params: {
+          locale: 'ain-Kana', tags: references.map { _1.fetch('name') }.join(' '),
+          tag_refs: references.to_json }
+      expect(response).to have_http_status(:ok)
+      expect(json.fetch('posts').map { _1.fetch('id') }).to match_array(original_ids)
+    end
+  end
+end

backend/spec/requests/posts_spec.rb

@@ -900,7 +900,7 @@ RSpec.describe 'Posts API', type: :request do
         query_count =
             count_sql_queries do
               get "/posts/#{ post_record.id }",
-                  headers: { 'X-Transfer-Code' => user.inheritance_code }
+                  headers: cookie_headers(user)
             end
 
         expect(response).to have_http_status(:ok)
@@ -2323,8 +2323,10 @@ RSpec.describe 'Posts API', type: :request do
         'prev' => nil
       )
       expect(latest.fetch('tags')).to include(
-        { 'name' => 'spec_tag_2', 'type' => 'added' },
-        { 'name' => 'spec_tag', 'type' => 'removed' }
+        { 'name' => 'spec_tag_2', 'restore_name' => 'spec_tag_2',
+          'external' => false, 'type' => 'added' },
+        { 'name' => 'spec_tag', 'restore_name' => 'spec_tag',
+          'external' => false, 'type' => 'removed' }
       )
       expect(latest.fetch('original_created_from')).to eq(
         'current' => oc_from.iso8601,
@@ -2351,7 +2353,8 @@ RSpec.describe 'Posts API', type: :request do
         'prev' => nil
       )
       expect(first.fetch('tags')).to include(
-        { 'name' => 'spec_tag', 'type' => 'added' }
+        { 'name' => 'spec_tag', 'restore_name' => 'spec_tag',
+          'external' => false, 'type' => 'added' }
       )
       expect(first.fetch('created_at')).to eq(t_v1.iso8601)
     end
@@ -2435,7 +2438,9 @@ RSpec.describe 'Posts API', type: :request do
       expect(response).to have_http_status(:ok)
       expect(json.fetch('count')).to eq(3)
       expect(json.fetch('versions').first.fetch('tags')).to include(
-          'name' => primary_tag_name_for(tag2, 'ja').name, 'type' => 'context')
+          'name' => primary_tag_name_for(tag2, 'ja').name,
+          'restore_name' => primary_tag_name_for(tag2, 'ja').name,
+          'external' => false, 'type' => 'context')
     end
 
     it 'filters versions by tag when the current snapshot includes the tag' do
@@ -2449,7 +2454,8 @@ RSpec.describe 'Posts API', type: :request do
       expect(versions[0]['post_id']).to eq(post_record.id)
       expect(versions[0]['version_no']).to eq(2)
       expect(versions[0]['tags']).to include(
-        { 'name' => 'spec_tag_2', 'type' => 'added' }
+        { 'name' => 'spec_tag_2', 'restore_name' => 'spec_tag_2',
+          'external' => false, 'type' => 'added' }
       )
     end
 
@@ -2467,10 +2473,12 @@ RSpec.describe 'Posts API', type: :request do
       first = versions[1]
 
       expect(latest['tags']).to include(
-        { 'name' => 'spec_tag', 'type' => 'removed' }
+        { 'name' => 'spec_tag', 'restore_name' => 'spec_tag',
+          'external' => false, 'type' => 'removed' }
       )
       expect(first['tags']).to include(
-        { 'name' => 'spec_tag', 'type' => 'added' }
+        { 'name' => 'spec_tag', 'restore_name' => 'spec_tag',
+          'external' => false, 'type' => 'added' }
       )
     end
 

backend/spec/requests/sitemap_entries_spec.rb

@@ -0,0 +1,155 @@
+require 'rails_helper'
+
+RSpec.describe 'Sitemap entries API', type: :request do
+  include_context 'Ainu locale'
+
+  let(:user) { create(:user, :member) }
+
+  it 'serves public resource counts with the default locale and page size' do
+    create(:post)
+    create(:tag, primary_name: 'sitemap_count_tag')
+
+    get '/sitemap_entries'
+
+    expect(response).to have_http_status(:ok)
+    expect(json.fetch('page_size')).to eq(1_000)
+    counts = json.fetch('resources').to_h { |entry|
+      [entry.fetch('resource'), entry.fetch('count')]
+    }
+    expect(counts).to eq(
+        'posts' => Post.count, 'tags' => Tag.count, 'deerjikists' => 0,
+        'materials' => 0, 'descriptions' => 0, 'tag_groups' => 0, 'theatres' => 0)
+  end
+
+  it 'paginates public post IDs in ascending order without exposing post contents' do
+    stub_const('SitemapEntriesController::PAGE_SIZE', 2)
+    posts = create_list(:post, 3)
+
+    get '/sitemap_entries/posts'
+    expect(response).to have_http_status(:ok)
+    expect(json).to eq('ids' => posts.first(2).map(&:id))
+
+    get '/sitemap_entries/posts', params: { page: 2 }
+    expect(response).to have_http_status(:ok)
+    expect(json).to eq('ids' => [posts.last.id])
+
+    get '/sitemap_entries/posts', params: { page: 3 }
+    expect(response).to have_http_status(:not_found)
+  end
+
+  ['0', '-1', 'invalid', '1.5'].each do |page|
+    it "rejects invalid sitemap page #{ page.inspect }" do
+      get '/sitemap_entries/posts', params: { page: }
+
+      expect(response).to have_http_status(:bad_request)
+    end
+  end
+
+  it 'rejects unsupported resource names' do
+    get '/sitemap_entries/users'
+
+    expect(response).to have_http_status(:not_found)
+  end
+
+  it 'returns an empty first page for a resource without entries' do
+    get '/sitemap_entries/posts'
+
+    expect(response).to have_http_status(:ok)
+    expect(json).to eq('ids' => [])
+  end
+
+  it 'rejects unregistered, deprecated and unsupported locales' do
+    get '/sitemap_entries', params: { locale: 'ain-Kana' }
+    expect(response).to have_http_status(:not_found)
+
+    locale.update!(deprecated_at: Time.current)
+    ['/sitemap_entries', '/sitemap_entries/posts'].each do |path|
+      get path, params: { locale: 'ain-Kana' }
+      expect(response).to have_http_status(:not_found)
+
+      get path, params: { locale: 'en' }
+      expect(response).to have_http_status(:not_found)
+    end
+  end
+
+  it 'only lists live materials and theatres' do
+    material = Material.create!(url: 'https://example.com/sitemap-material')
+    discarded_material = Material.create!(url: 'https://example.com/sitemap-discarded')
+    discarded_material.discard!
+    theatre = create(:theatre)
+    create(:theatre).discard!
+
+    get '/sitemap_entries/materials'
+    expect(response).to have_http_status(:ok)
+    expect(json).to eq('ids' => [material.id])
+
+    get '/sitemap_entries/theatres'
+    expect(response).to have_http_status(:ok)
+    expect(json).to eq('ids' => [theatre.id])
+  end
+
+  context 'with an active Ainu locale' do
+    before { locale }
+
+    it 'uses tag IDs and only includes deerjikists with linked accounts' do
+      tagged = create(:tag, primary_name: 'sitemap_deer', category: :deerjikist)
+      unlinked = create(:tag, primary_name: 'sitemap_unlinked', category: :deerjikist)
+      Deerjikist.create!(tag: tagged, platform: 'youtube', code: 'sitemap-channel')
+      Deerjikist.create!(tag: tagged, platform: 'nico', code: 'sitemap-nico')
+
+      get '/sitemap_entries/tags', params: { locale: 'ain-Kana' }
+      expect(response).to have_http_status(:ok)
+      expect(json.fetch('ids')).to contain_exactly(tagged.id, unlinked.id)
+
+      get '/sitemap_entries/deerjikists', params: { locale: 'ain-Kana' }
+      expect(response).to have_http_status(:ok)
+      expect(json).to eq('ids' => [tagged.id])
+    end
+
+    it 'lists description IDs for the requested language with a nonempty current version' do
+      tag = create(:tag, primary_name: 'sitemap_description')
+      japanese = TagDescriptionOperation.create!(
+          Locale.nipponese, tag:, body: 'Japanese sitemap body', created_by_user: user)
+      ainu = TagDescriptionOperation.create!(
+          locale, tag:, body: 'Ainu sitemap body', created_by_user: user)
+      unversioned_tag = create(:tag, primary_name: 'sitemap_unversioned')
+      TagDescription.create!(tag: unversioned_tag, language_code: 'ain',
+                             body: 'No revision', version_no: 1)
+      empty_tag = create(:tag, primary_name: 'sitemap_empty')
+      # Legacy empty bodies can exist even though the write service rejects them.
+      empty = TagDescription.create!(tag: empty_tag, language_code: 'ain',
+                                     body: '', version_no: 1)
+      TagDescriptionVersion.create!(tag_id: empty_tag.id, language_code: 'ain',
+                                    body: '', version_no: 1, event_type: 'create',
+                                    created_by_user_id: user.id, created_at: Time.current)
+
+      get '/sitemap_entries/descriptions', params: { locale: 'ain-Kana' }
+      expect(response).to have_http_status(:ok)
+      expect(json).to eq('ids' => [ainu.id])
+      expect(json.fetch('ids')).not_to include(japanese.id, empty.id)
+
+      get '/sitemap_entries/descriptions', params: { locale: 'ja' }
+      expect(response).to have_http_status(:ok)
+      expect(json).to eq('ids' => [japanese.id])
+
+      get '/sitemap_entries', params: { locale: 'ain-Kana' }
+      expect(response).to have_http_status(:ok)
+      descriptions = json.fetch('resources').find { |entry|
+        entry.fetch('resource') == 'descriptions'
+      }
+      expect(descriptions.fetch('count')).to eq(1)
+    end
+
+    it 'excludes groups without a revision matching the current version' do
+      group = TagGroupOperation.create!(
+          Locale.nipponese, name: 'Sitemap group', description: 'Group description',
+          members: [], placements: [], actor: user)
+      TagGroup.create!(name: 'Unversioned sitemap group', version_no: 1)
+
+      get '/sitemap_entries/tag_groups', params: { locale: 'ain-Kana' }
+
+      expect(response).to have_http_status(:ok)
+      expect(json).to eq('ids' => [group.id])
+    end
+  end
+end

backend/spec/requests/tag_description_wiki_write_spec.rb

@@ -4,7 +4,7 @@ RSpec.describe 'Tag description Wiki facade writes', type: :request do
   include WikiRecords
   let!(:user) { create_member_user! }
   let!(:tag) { create(:tag, primary_name: 'description_write') }
-  let(:headers) { { 'X-Transfer-Code' => user.inheritance_code } }
+  let(:headers) { cookie_headers(user) }
 
   def stored_state
     [Tag, TagName, TagVersion, TagDescription, TagDescriptionVersion].map do |model|

backend/spec/requests/tag_descriptions_spec.rb

@@ -7,7 +7,7 @@ RSpec.describe 'Tag description native API', type: :request do
   let(:editor) { create(:user, :member, name: 'description editor') }
   let(:tag_name) { create(:tag_name, name: 'native_description') }
   let(:tag) { create(:tag, primary_tag_name: tag_name) }
-  let(:headers) { { 'X-Transfer-Code' => editor.inheritance_code } }
+  let(:headers) { cookie_headers(editor) }
   let(:endpoint) { "/tags/#{ tag.id }/description" }
 
   def stored_state
@@ -285,7 +285,7 @@ RSpec.describe 'Tag description native API', type: :request do
       guest = create(:user, :guest)
       before_state = stored_state
       native_write(body: 'forbidden',
-                   request_headers: { 'X-Transfer-Code' => guest.inheritance_code })
+                   request_headers: cookie_headers(guest))
       expect(response).to have_http_status(:forbidden)
       expect(stored_state).to eq(before_state)
     end
@@ -294,7 +294,7 @@ RSpec.describe 'Tag description native API', type: :request do
       banned = create(:user, :member, :banned)
       before_state = stored_state
       native_write(body: 'forbidden',
-                   request_headers: { 'X-Transfer-Code' => banned.inheritance_code })
+                   request_headers: cookie_headers(banned))
       expect(response).to have_http_status(:forbidden)
       expect(stored_state).to eq(before_state)
     end

backend/spec/requests/tag_group_locale_spec.rb

@@ -7,7 +7,7 @@ RSpec.describe 'Tag group locale contracts', type: :request do
   let!(:user) { create_member_user! }
   let!(:tag) { create(:tag, primary_name: 'japanese_member') }
   let!(:ainu_name) { add_ainu_name(tag, 'ainu_member') }
-  let(:headers) { { 'X-Transfer-Code' => user.inheritance_code } }
+  let(:headers) { cookie_headers(user) }
   let(:members) { [{ 'tag_id' => tag.id }] }
   let(:placements) do
     [{ 'section_name' => 'section', 'description' => nil, 'children' => [
@@ -22,7 +22,7 @@ RSpec.describe 'Tag group locale contracts', type: :request do
 
   it 'uses selected-language names in native collection and nested placements' do
     ["/tag_groups/#{ group.id }", '/tag_groups'].each do |path|
-      get path, params: { locale: 'ain' }
+      get path, params: { locale: 'ain-Kana' }
       expect(response).to have_http_status(:ok)
       representation = json.is_a?(Array) ? json.sole : json
       expect(representation.fetch('members').sole.fetch('tag').fetch('name'))
@@ -37,14 +37,14 @@ RSpec.describe 'Tag group locale contracts', type: :request do
   it 'uses snapshot names recursively for history and current names for the latest view' do
     version = group.versions.sole
     ainu_name.update!(name: 'renamed_ainu')
-    get "/wiki/#{ group.id }", params: { locale: 'ain' }
+    get "/wiki/#{ group.id }", params: { locale: 'ain-Kana' }
     expect(response).to have_http_status(:ok)
     expect(json.fetch('body')).to include('renamed_ainu')
-    get "/wiki/#{ group.id }", params: { locale: 'ain', version: version.id }
+    get "/wiki/#{ group.id }", params: { locale: 'ain-Kana', version: version.id }
     expect(response).to have_http_status(:ok)
     expect(json.fetch('body').scan('ainu_member').length).to eq(2)
     expect(json.fetch('body')).not_to include('renamed_ainu', 'japanese_member')
-    get "/wiki/#{ group.id }/diff", params: { locale: 'ain', from: version.id }
+    get "/wiki/#{ group.id }/diff", params: { locale: 'ain-Kana', from: version.id }
     expect(response).to have_http_status(:ok)
     expect(json.fetch('diff').map { _1.fetch('type') }.uniq).to eq(['context'])
   end
@@ -52,23 +52,24 @@ RSpec.describe 'Tag group locale contracts', type: :request do
   ['タググループ:', 'tag_group:', 'TAG_GROUP:'].each do |prefix|
     it "round trips #{ prefix } through create, lookup, search and update" do
       post '/wiki', params: {
-          locale: 'ain', title: "#{ prefix }parent", body: '- tag_group:locale group' },
+          locale: 'ain-Kana', title: "#{ prefix }parent", body: '- tag_group:locale group' },
           headers: headers
       expect(response).to have_http_status(:created)
       id = json.fetch('id')
       expect(json.fetch('body')).to include('タググループ:locale group')
       path = "/wiki/title/#{ CGI.escapeURIComponent("#{ prefix }parent") }"
-      get path, params: { locale: 'ain' }
+      get path, params: { locale: 'ain-Kana' }
       expect(response).to have_http_status(:ok)
       expect(json.fetch('id')).to eq(id)
-      get "#{ path }/exists", params: { locale: 'ain' }
+      get "#{ path }/exists", params: { locale: 'ain-Kana' }
       expect(response).to have_http_status(:no_content)
-      get '/wiki/search', params: { locale: 'ain', title: "#{ prefix }parent" }
+      get '/wiki/search', params: { locale: 'ain-Kana', title: "#{ prefix }parent" }
       expect(json.map { _1.fetch('id') }).to eq([id])
       put "/wiki/#{ id }", params: {
-          locale: 'ain', title: "#{ prefix }renamed", body: '- ainu_member' }, headers: headers
+          locale: 'ain-Kana', title: "#{ prefix }renamed", body: '- ainu_member' },
+          headers: headers
       expect(response).to have_http_status(:ok)
-      get "/tag_groups/#{ id }", params: { locale: 'ain' }
+      get "/tag_groups/#{ id }", params: { locale: 'ain-Kana' }
       expect(json.fetch('members').sole.fetch('tag').fetch('name')).to eq('ainu_member')
     end
   end
@@ -81,7 +82,7 @@ RSpec.describe 'Tag group locale contracts', type: :request do
     end.to raise_error(TagGroupMarkdownParser::InvalidDocument)
     before_state = group_state
     put "/wiki/#{ group.id }", params: {
-        locale: 'ain', title: 'タググループ:partial rename', body: '- japanese_member' },
+        locale: 'ain-Kana', title: 'タググループ:partial rename', body: '- japanese_member' },
         headers: headers
     expect(response).to have_http_status(:unprocessable_entity)
     expect(group_state).to eq(before_state)
@@ -89,15 +90,15 @@ RSpec.describe 'Tag group locale contracts', type: :request do
 
   it 'passes locale into native validation and facade compatibility checks' do
     post '/tag_groups', params: {
-        locale: 'ain', name: 'native', description: nil, members:, placements: },
+        locale: 'ain-Kana', name: 'native', description: nil, members:, placements: },
         headers:, as: :json
     expect(response).to have_http_status(:created)
     id = json.fetch('id')
     expect(json.fetch('members').sole.fetch('tag').fetch('name')).to eq('ainu_member')
-    get "/wiki/#{ id }", params: { locale: 'ain' }
+    get "/wiki/#{ id }", params: { locale: 'ain-Kana' }
     expect(response).to have_http_status(:ok)
     body = json.fetch('body')
-    put "/wiki/#{ id }", params: { locale: 'ain', title: 'tag_group:native', body: },
+    put "/wiki/#{ id }", params: { locale: 'ain-Kana', title: 'tag_group:native', body: },
         headers: headers
     expect(response).to have_http_status(:ok)
     expect(TagGroup.find(id).version_no).to eq(1)
@@ -115,7 +116,7 @@ RSpec.describe 'Tag group locale contracts', type: :request do
     representation = TagGroupRepr.historical(ainu_locale, version)
     expect(representation.fetch('members').sole.fetch('tag').fetch('name')).to be_nil
     expect(representation.fetch('placements').sole.fetch('tag').fetch('name')).to be_nil
-    get "/wiki/#{ old_group.id }", params: { locale: 'ain', version: version.id }
+    get "/wiki/#{ old_group.id }", params: { locale: 'ain-Kana', version: version.id }
     expect(response).to have_http_status(:unprocessable_entity)
     expect(response.body).not_to include('historical_japanese', 'current_ainu')
   end

backend/spec/requests/tag_group_markdown_spec.rb

@@ -37,7 +37,7 @@ RSpec.describe 'Tag group Markdown round trips through the Wiki facade', type: :
         markdown.lines.map(&:chomp).reject(&:empty?))
 
     post '/wiki', params: { title: 'タググループ:再解析', body: },
-         headers: { 'X-Transfer-Code' => user.inheritance_code }
+         headers: cookie_headers(user)
     expect(response).to have_http_status(:created)
     parsed = group_rows('tag_groups', name: '再解析').sole
     expect_group_snapshot(parsed.fetch('id'), number: 1, placements:, members:, description:)

backend/spec/requests/tag_group_wiki_write_spec.rb

@@ -7,7 +7,7 @@ RSpec.describe 'Tag group Wiki facade writes', type: :request do
   let!(:user) { create_member_user! }
   let!(:tag) { group_tag('洗澡鹿') }
   let!(:other_tag) { group_tag('伊地知ニジカ') }
-  let(:headers) { { 'X-Transfer-Code' => user.inheritance_code } }
+  let(:headers) { cookie_headers(user) }
   let(:members) { [{ 'tag_id' => tag.id, 'version_no' => tag.version_no }] }
   let(:placements) { [{ 'tag_id' => tag.id, 'children' => [] }] }
 
@@ -148,7 +148,7 @@ RSpec.describe 'Tag group Wiki facade writes', type: :request do
       body = group_markdown(page)
       travel_to(1.hour.from_now) do
         expect_noop_group_update(group_id: page.id) do
-          update_group(body:, request_headers: { 'X-Transfer-Code' => editor.inheritance_code })
+          update_group(body:, request_headers: cookie_headers(editor))
         end
       end
     end
@@ -212,7 +212,7 @@ RSpec.describe 'Tag group Wiki facade writes', type: :request do
     it 'records the editor and update time' do
       editor = create(:user, :member, name: '編輯者')
       travel_to(Time.current + 1.hour) do
-        update_group(request_headers: { 'X-Transfer-Code' => editor.inheritance_code })
+        update_group(request_headers: cookie_headers(editor))
         expect(response).to have_http_status(:ok)
         current = group_rows('tag_groups', id: page.id).sole
         version = group_version(page.id, 2)
@@ -271,7 +271,7 @@ RSpec.describe 'Tag group Wiki facade writes', type: :request do
           when :guest then create(:user, :guest)
           when :banned then create(:user, :member, :banned)
           end
-          request_headers = actor ? { 'X-Transfer-Code' => actor.inheritance_code } : { }
+          request_headers = actor ? cookie_headers(actor) : { }
           before_state = group_state
           write_group(operation, request_headers)
           expect(response).to have_http_status(role ? :forbidden : :unauthorized)

backend/spec/requests/tag_group_write_integrity_spec.rb

@@ -8,7 +8,7 @@ RSpec.describe 'Tag group write integrity', type: :request do
   let!(:user) { create_member_user! }
   let!(:tag) { group_tag('洗澡鹿') }
   let!(:other_tag) { group_tag('伊地知ニジカ') }
-  let(:headers) { { 'X-Transfer-Code' => user.inheritance_code } }
+  let(:headers) { cookie_headers(user) }
   let(:members) { [{ 'tag_id' => tag.id, 'version_no' => tag.version_no }] }
   let(:placements) { [{ 'tag_id' => tag.id, 'children' => [] }] }
 
@@ -141,7 +141,7 @@ RSpec.describe 'Tag group write integrity', type: :request do
     end
     let!(:id) { seed_group(name: '更新', members:, placements:) }
     let!(:editor) { create(:user, :member) }
-    let(:headers) { { 'X-Transfer-Code' => editor.inheritance_code } }
+    let(:headers) { cookie_headers(editor) }
 
     it 'keeps all membership and placement audit fields on a name-only edit' do
       before_rows = group_state.slice('tag_group_tags', 'tag_group_groups', 'tag_group_placements')

backend/spec/requests/tag_groups_spec.rb

@@ -47,7 +47,7 @@ RSpec.describe 'Tag group native API', type: :request do
         when :guest then create(:user, :guest)
         when :banned then create(:user, :member, :banned)
         end
-        headers = actor ? { 'X-Transfer-Code' => actor.inheritance_code } : { }
+        headers = actor ? cookie_headers(actor) : { }
         before_state = group_state
         if operation == :create
           post '/tag_groups', params: { }, headers:, as: :json
@@ -61,7 +61,7 @@ RSpec.describe 'Tag group native API', type: :request do
 
     it "rejects a banned IP for native #{ operation }" do
       IpAddress.create!(ip_address: IPAddr.new('127.0.0.1').hton, banned_at: Time.current)
-      headers = { 'X-Transfer-Code' => user.inheritance_code }
+      headers = cookie_headers(user)
       before_state = group_state
       if operation == :create
         post '/tag_groups', params: { }, headers:, as: :json
@@ -77,7 +77,7 @@ RSpec.describe 'Tag group native API', type: :request do
     let!(:tag) { group_tag('掲載タグ') }
     let!(:unplaced) { group_tag('未掲載タグ') }
     let!(:child_id) { seed_group(name: '子', description: '子の説明') }
-    let(:headers) { { 'X-Transfer-Code' => user.inheritance_code } }
+    let(:headers) { cookie_headers(user) }
     let(:members) do
       [{ 'tag_id' => tag.id }, { 'tag_group_id' => child_id }, { 'tag_id' => unplaced.id }]
     end
@@ -300,7 +300,7 @@ RSpec.describe 'Tag group native API', type: :request do
           travel_to(1.hour.from_now) do
             expect_noop_group_update(group_id:) do
               put "/tag_groups/#{ group_id }", params: synchronised_payload,
-                  headers: { 'X-Transfer-Code' => editor.inheritance_code }, as: :json
+                  headers: cookie_headers(editor), as: :json
             end
           end
         end

backend/spec/requests/tag_resource_ids_spec.rb

@@ -3,7 +3,7 @@ require 'rails_helper'
 RSpec.describe 'Tag resource ID allocation', type: :request do
   include WikiRecords
   let!(:user) { create_member_user! }
-  let(:headers) { { 'X-Transfer-Code' => user.inheritance_code } }
+  let(:headers) { cookie_headers(user) }
 
   def create_description name
     tag = create(:tag, primary_name: name)

backend/spec/requests/users_spec.rb

@@ -10,7 +10,31 @@ RSpec.describe 'Users', type: :request do
   end
 
   def auth_headers(user)
-    { 'X-Transfer-Code' => user.inheritance_code }
+    cookie_headers(user)
+  end
+
+  describe 'GET /users/session' do
+    it 'does not accept the retired transfer-code header' do
+      user = create(:user)
+      get '/users/session', headers: { 'X-Transfer-Code' => user.inheritance_code }
+      expect(response).to have_http_status(:unauthorized)
+    end
+
+    it 'requires authentication' do
+      get '/users/session'
+      expect(response).to have_http_status(:unauthorized)
+    end
+
+    it 'returns public user fields without recording a visit' do
+      user = create(:user, name: 'SSR user')
+      expect {
+        get '/users/session', headers: auth_headers(user)
+      }.not_to change(UserIp, :count)
+
+      expect(response).to have_http_status(:ok)
+      expect(json).to eq('id' => user.id, 'name' => user.name, 'role' => user.role)
+      expect(response.body).not_to include(user.inheritance_code)
+    end
   end
 
   describe 'POST /users' do
@@ -233,17 +257,102 @@ RSpec.describe 'Users', type: :request do
     end
   end
 
+  describe 'Cookie sessions with CSRF enabled', csrf: true do
+    def csrf_headers
+      get '/users/csrf'
+      expect(response).to have_http_status(:ok)
+      { 'X-CSRF-Token' => json.fetch('token'), 'Origin' => 'http://www.example.com' }
+    end
+
+    def establish_session(user)
+      post '/users/verify', params: { code: user.inheritance_code }, headers: csrf_headers
+      expect(response).to have_http_status(:ok)
+      expect(json.fetch('valid')).to be(true)
+    end
+
+    it 'rejects a write without a token before creating an account' do
+      expect { post '/users' }.not_to change(User, :count)
+      expect(response).to have_http_status(:forbidden)
+      expect(response.headers['X-CSRF-Invalid']).to eq('1')
+    end
+
+    it 'uses the encrypted persistent Cookie for CSR and SSR session reads' do
+      user = create(:user)
+      establish_session(user)
+      cookie = Array(response.headers['set-cookie']).join
+      expect(cookie).to include('httponly', 'samesite=lax')
+      expect(cookie).not_to include(user.inheritance_code)
+      expires = Time.httpdate(cookie.match(/expires=([^;]+)/i)[1])
+      expect(expires).to be > 19.years.from_now
+      get '/users/session'
+      expect(json.fetch('id')).to eq(user.id)
+      expect(response.body).not_to include(user.inheritance_code)
+      get '/users/me'
+      expect(json.fetch('inheritance_code')).to eq(user.inheritance_code)
+      expect(response.headers['Cache-Control']).to include('no-store')
+    end
+
+    it 'rejects a cross-origin write with an otherwise valid token' do
+      headers = csrf_headers.merge('Origin' => 'https://other.invalid')
+      expect { post '/users', headers: }.not_to change(User, :count)
+      expect(response).to have_http_status(:forbidden)
+    end
+
+    it 'does not replace an existing Cookie identity during recovery' do
+      current = create(:user)
+      old = create(:user)
+      establish_session(current)
+      post '/users/verify', params: { code: old.inheritance_code, restore: true },
+                           headers: csrf_headers
+      expect(json.fetch('user').fetch('id')).to eq(current.id)
+      get '/users/session'
+      expect(json.fetch('id')).to eq(current.id)
+    end
+
+    it 'allows explicit transfer and refreshes the active session' do
+      first = create(:user)
+      second = create(:user)
+      establish_session(first)
+      establish_session(second)
+      get '/users/session'
+      expect(json.fetch('id')).to eq(second.id)
+    end
+
+    it 'keeps the renewed session and rejects the previous credential' do
+      user = create(:user)
+      establish_session(user)
+      old_cookie = Array(response.headers['set-cookie']).first.split(';').first
+      old_code = user.inheritance_code
+      post '/users/code/renew', headers: csrf_headers
+      expect(response).to have_http_status(:ok)
+      expect(json.fetch('code')).not_to eq(old_code)
+      get '/users/session'
+      expect(json.fetch('id')).to eq(user.id)
+      other_browser = ActionDispatch::Integration::Session.new(Rails.application)
+      other_browser.get('/users/session', headers: { 'Cookie' => old_cookie })
+      expect(other_browser.response).to have_http_status(:unauthorized)
+    end
+
+    it 'clears browser authentication on session deletion' do
+      establish_session(create(:user))
+      delete '/users/session', headers: csrf_headers
+      expect(response).to have_http_status(:no_content)
+      get '/users/session'
+      expect(response).to have_http_status(:unauthorized)
+    end
+  end
+
   describe 'GET /users/me' do
-    it 'returns 404 when code not found' do
+    it 'requires a session even when a code is supplied in the query' do
       get '/users/me', params: { code: 'nope' }
 
-      expect(response).to have_http_status(:not_found)
+      expect(response).to have_http_status(:unauthorized)
     end
 
     it 'returns user slice when found' do
       user = create(:user, inheritance_code: SecureRandom.uuid, name: 'me', role: 'guest')
 
-      get '/users/me', params: { code: user.inheritance_code }
+      get '/users/me', headers: cookie_headers(user)
 
       expect(response).to have_http_status(:ok)
       expect(json['id']).to eq(user.id)

backend/spec/requests/wiki_conflict_spec.rb

@@ -5,7 +5,7 @@ RSpec.describe 'Wiki conflict handling', type: :request do
   let!(:user) { create_member_user! }
 
   def auth_headers user
-    { 'X-Transfer-Code' => user.inheritance_code }
+    cookie_headers(user)
   end
 
   it 'returns 409 when base_revision_id is stale' do

backend/spec/requests/wiki_creation_freeze_spec.rb

@@ -5,7 +5,7 @@ RSpec.describe 'Wiki creation freeze', type: :request do
   include WikiRecords
 
   let!(:user) { create_member_user! }
-  let(:headers) { { 'X-Transfer-Code' => user.inheritance_code } }
+  let(:headers) { cookie_headers(user) }
 
 
   context 'existing description write protection' do
@@ -18,7 +18,7 @@ RSpec.describe 'Wiki creation freeze', type: :request do
       it "rejects #{ role || 'anonymous' } without changing either history" do
         actor = role && create(:user, role == :banned ? :member : role)
         actor.update!(banned_at: Time.current) if role == :banned
-        request_headers = actor ? { 'X-Transfer-Code' => actor.inheritance_code } : { }
+        request_headers = actor ? cookie_headers(actor) : { }
         before_state = group_state
         put "/wiki/#{ page.id }", params: { title: tag.name('ja'), body: 'after' },
             headers: request_headers

backend/spec/requests/wiki_locale_spec.rb

@@ -8,7 +8,7 @@ RSpec.describe 'Wiki and native API locale contracts', type: :request do
   let!(:user) { create_member_user! }
   let!(:tag) { create(:tag, primary_name: 'japanese_title') }
   let!(:ainu_name) { add_ainu_name(tag, 'ainu_title') }
-  let(:headers) { { 'X-Transfer-Code' => user.inheritance_code } }
+  let(:headers) { cookie_headers(user) }
   let!(:japanese) do
     TagDescriptionOperation.create!(
         Locale.nipponese, tag:, body: 'Japanese body', created_by_user: user)
@@ -20,12 +20,12 @@ RSpec.describe 'Wiki and native API locale contracts', type: :request do
 
   ['/wiki', '/wiki/search'].each do |path|
     it "filters #{ path } by the selected language" do
-      get path, params: { locale: 'ain' }
+      get path, params: { locale: 'ain-Kana' }
       expect(response).to have_http_status(:ok)
       expect(json.map { _1.fetch('id') }).to eq([ainu.id])
       expect(json.sole).to include('title' => 'ainu_title', 'body' => 'Ainu body')
 
-      get path, params: { locale: 'ain', title: 'japanese' }
+      get path, params: { locale: 'ain-Kana', title: 'japanese' }
       expect(response).to have_http_status(:ok)
       expect(json).to eq([])
     end
@@ -39,32 +39,50 @@ RSpec.describe 'Wiki and native API locale contracts', type: :request do
 
   it 'resolves titles and aliases only in the selected language in both APIs' do
     ['/wiki/title/japanese_title', '/tags/name/japanese_title/description'].each do |path|
-      get path, params: { locale: 'ain' }
+      get path, params: { locale: 'ain-Kana' }
       expect(response).to have_http_status(:not_found)
     end
     ['/wiki/title/ainu_title', '/tags/name/ainu_title/description'].each do |path|
-      get path, params: { locale: 'ain' }
+      get path, params: { locale: 'ain-Kana' }
       expect(response).to have_http_status(:ok)
       expect(json.fetch('body')).to eq('Ainu body')
     end
-    get '/wiki/title/ainu_title/exists', params: { locale: 'ain' }
+    get '/wiki/title/ainu_title/exists', params: { locale: 'ain-Kana' }
     expect(response).to have_http_status(:no_content)
-    get '/wiki/title/japanese_title/exists', params: { locale: 'ain' }
+    get '/wiki/title/japanese_title/exists', params: { locale: 'ain-Kana' }
     expect(response).to have_http_status(:not_found)
   end
 
-  it 'does not disclose another language through ID, existence, diff or history' do
+  it 'resolves a foreign description ID to only the requested language body' do
+    get "/wiki/#{ japanese.id }", params: { locale: 'ain-Kana' }
+    expect(response).to have_http_status(:ok)
+    expect(json).to include('id' => ainu.id, 'body' => 'Ainu body')
+    expect(response.body).not_to include('Japanese body')
+  end
+
+  it 'does not reuse foreign revision IDs when resolving a description' do
+    get "/wiki/#{ japanese.id }", params: {
+        locale: 'ain-Kana', version: current_description_version(japanese).id }
+    expect(response).to have_http_status(:not_found)
+    expect(response.body).not_to include('Japanese body')
+  end
+
+  it 'keeps existence and diff scoped to the specified language and description ID' do
     revision = current_description_version(japanese)
-    ["/wiki/#{ japanese.id }", "/wiki/#{ japanese.id }/exists",
-     "/wiki/#{ japanese.id }/diff"].each do |path|
-      get path, params: { locale: 'ain', from: revision.id }
+    ["/wiki/#{ japanese.id }/exists", "/wiki/#{ japanese.id }/diff"].each do |path|
+      get path, params: { locale: 'ain-Kana', from: revision.id }
       expect(response).to have_http_status(:not_found)
       expect(response.body).not_to include('Japanese body')
     end
-    get '/wiki/changes', params: { locale: 'ain', id: japanese.id }
+    get "/wiki/#{ ainu.id }/exists", params: { locale: 'ain-Kana' }
+    expect(response).to have_http_status(:no_content)
+  end
+
+  it 'keeps history scoped to the requested language without foreign revisions' do
+    get '/wiki/changes', params: { locale: 'ain-Kana', id: japanese.id }
     expect(response).to have_http_status(:ok)
     expect(json).to eq([])
-    get '/wiki/changes', params: { locale: 'ain' }
+    get '/wiki/changes', params: { locale: 'ain-Kana' }
     expect(json.map { _1.fetch('revision_id') })
         .to eq([current_description_version(ainu).id])
   end
@@ -73,7 +91,7 @@ RSpec.describe 'Wiki and native API locale contracts', type: :request do
     snapshot = [japanese.attributes, ainu.attributes, ainu_name.attributes]
     expect do
       put "/wiki/#{ japanese.id }", params: {
-          locale: 'ain', title: 'renamed', body: 'wrong target' }, headers: headers
+          locale: 'ain-Kana', title: 'renamed', body: 'wrong target' }, headers: headers
     end.not_to change(TagDescriptionVersion, :count)
     expect(response).to have_http_status(:not_found)
     expect([japanese.reload.attributes, ainu.reload.attributes, ainu_name.reload.attributes])
@@ -89,10 +107,10 @@ RSpec.describe 'Wiki and native API locale contracts', type: :request do
       snapshot = original.attributes
       expect do
         if api == :wiki
-          post '/wiki', params: { locale: 'ain', title: 'other_ainu', body: 'created' },
+          post '/wiki', params: { locale: 'ain-Kana', title: 'other_ainu', body: 'created' },
                headers: headers
         else
-          put "/tags/#{ other.id }/description", params: { locale: 'ain', body: 'created' },
+          put "/tags/#{ other.id }/description", params: { locale: 'ain-Kana', body: 'created' },
               headers: headers
         end
       end.to change(TagDescription, :count).by(1)
@@ -108,20 +126,20 @@ RSpec.describe 'Wiki and native API locale contracts', type: :request do
   it 'shares selected-language edits and revision identity across both APIs' do
     snapshot = japanese.attributes
     first = current_description_version(ainu)
-    put "/tags/#{ tag.id }/description", params: { locale: 'ain', body: 'native edit' },
+    put "/tags/#{ tag.id }/description", params: { locale: 'ain-Kana', body: 'native edit' },
         headers: headers
     expect(response).to have_http_status(:ok)
     second = current_description_version(ainu)
     expect(second).to have_attributes(language_code: 'ain', version_no: 2)
     expect(second.id).not_to eq(first.id)
-    get "/wiki/#{ ainu.id }", params: { locale: 'ain' }
+    get "/wiki/#{ ainu.id }", params: { locale: 'ain-Kana' }
     expect(json).to include('body' => 'native edit', 'revision_id' => second.id)
 
     put "/wiki/#{ ainu.id }", params: {
-        locale: 'ain', title: 'ainu_title', body: 'facade edit',
+        locale: 'ain-Kana', title: 'ainu_title', body: 'facade edit',
         base_revision_id: second.id }, headers: headers
     expect(response).to have_http_status(:ok)
-    get "/tags/#{ tag.id }/description", params: { locale: 'ain' }
+    get "/tags/#{ tag.id }/description", params: { locale: 'ain-Kana' }
     expect(json).to include('body' => 'facade edit', 'language_code' => 'ain', 'version_no' => 3)
     expect(japanese.reload.attributes).to eq(snapshot)
   end
@@ -133,7 +151,7 @@ RSpec.describe 'Wiki and native API locale contracts', type: :request do
     snapshot = [ainu.reload.attributes, ainu_name.attributes, japanese.attributes]
     expect do
       put "/wiki/#{ ainu.id }", params: {
-          locale: 'ain', title: 'conflicting_name', body: 'current',
+          locale: 'ain-Kana', title: 'conflicting_name', body: 'current',
           base_revision_id: stale.id }, headers: headers
     end.to change(TagDescriptionVersion, :count).by(0).and change(TagVersion, :count).by(0)
     expect(response).to have_http_status(:conflict)
@@ -145,14 +163,14 @@ RSpec.describe 'Wiki and native API locale contracts', type: :request do
     first = current_description_version(ainu)
     TagDescriptionOperation.update!(
         ainu_locale, tag:, body: 'later', updated_by_user: user)
-    get "/wiki/#{ ainu.id }", params: { locale: 'ain', version: first.id }
+    get "/wiki/#{ ainu.id }", params: { locale: 'ain-Kana', version: first.id }
     expect(response).to have_http_status(:ok)
     expect(json).to include('body' => 'Ainu body', 'revision_id' => first.id)
-    get "/wiki/#{ ainu.id }/diff", params: { locale: 'ain', from: first.id }
+    get "/wiki/#{ ainu.id }/diff", params: { locale: 'ain-Kana', from: first.id }
     expect(response).to have_http_status(:ok)
     expect(json.fetch('newer_revision_id')).to eq(current_description_version(ainu).id)
     get "/wiki/#{ ainu.id }/diff", params: {
-        locale: 'ain', from: current_description_version(japanese).id }
+        locale: 'ain-Kana', from: current_description_version(japanese).id }
     expect(response).to have_http_status(:not_found)
   end
 end

backend/spec/requests/wiki_spec.rb

@@ -6,7 +6,7 @@ require 'securerandom'
 RSpec.describe 'Wiki API', type: :request do
   include WikiRecords
   def auth_headers(user)
-    { 'X-Transfer-Code' => user.inheritance_code }
+    cookie_headers(user)
   end
 
   let!(:user) { create_member_user! }
@@ -80,7 +80,7 @@ RSpec.describe 'Wiki API', type: :request do
     let(:guest) { create(:user, role: 'guest') }
 
     def auth_headers(user)
-      { 'X-Transfer-Code' => user.inheritance_code }
+      cookie_headers(user)
     end
 
     context 'when not logged in' do
@@ -126,7 +126,7 @@ RSpec.describe 'Wiki API', type: :request do
     let(:guest)  { create(:user, role: 'guest',  inheritance_code: SecureRandom.hex(16)) }
 
     def auth_headers(user)
-      { 'X-Transfer-Code' => user.inheritance_code }
+      cookie_headers(user)
     end
 
     let!(:test_tag_name) { create(:tag, primary_name: 'TestPage').tag_name('ja') }

backend/spec/requests/wiki_title_collision_spec.rb

@@ -5,7 +5,7 @@ RSpec.describe 'Wiki title collision', type: :request do
   let!(:user) { create_member_user! }
 
   def auth_headers user
-    { 'X-Transfer-Code' => user.inheritance_code }
+    cookie_headers(user)
   end
 
   def create_wiki_page title:, body:

backend/spec/requests/wiki_unmigrated_contract_spec.rb

@@ -17,7 +17,7 @@ RSpec.describe 'Removed standalone Wiki resources', type: :request do
       user
       before_state = group_state
       post '/wiki', params: { title:, body: 'body' },
-           headers: { 'X-Transfer-Code' => user.inheritance_code }
+           headers: cookie_headers(user)
       expect(response).to have_http_status(:unprocessable_entity)
       expect(group_state).to eq(before_state)
     end

backend/spec/services/certified_tag_name_translations_spec.rb

@@ -0,0 +1,116 @@
+require 'rails_helper'
+require 'tempfile'
+
+RSpec.describe CertifiedTagNameTranslations do
+  let!(:language) { Language.create!(code: 'ain', name: 'ain') }
+  let!(:script) { Script.create!(code: 'Kana', name: 'Kana') }
+  let!(:tag) { create(:tag, primary_name: 'source') }
+  let(:entries) { [{ 'ja' => 'source', 'ain-Kana' => 'レ_ハイタ' }] }
+  let(:document) do
+    { 'format' => described_class::FORMAT,
+      'source_locale' => 'ja', 'target_locale' => 'ain-Kana', 'entries' => entries }
+  end
+  let(:locale) do
+    Locale.new(code: 'ain-Kana', language_code: 'ain', script_code: 'Kana',
+               region_code: 392, variants: '', name: 'Ainu')
+  end
+
+  around do |example|
+    Tempfile.create(['certified-names', '.json']) do |file|
+      @path = file.path
+      example.run
+    end
+  end
+
+  def write_document
+    File.write(@path, JSON.generate(document))
+    locale.certified_tag_names_path = @path
+  end
+
+  it 'registers certified names before automatic names and records their provenance' do
+    other = create(:tag, primary_name: 'レ_ハイタ')
+    write_document
+
+    locale.save!
+
+    expect(tag.reload.tag_name('ain')).to have_attributes(
+        name: 'レ_ハイタ', primary_flg: true, auto_generated: false)
+    expect(other.reload.tag_name('ain')).to have_attributes(
+        name: "Tag_##{ other.id }", auto_generated: true)
+    version = tag.tag_versions.order(:version_no).last
+    expect(version.created_by_user_id).to be_nil
+    expect(version.names.fetch('ain')).to include(
+        'name' => 'レ_ハイタ', 'auto_generated' => false)
+  end
+
+  it 'skips missing sources without rolling back the locale or matching entries' do
+    entries.unshift({ 'ja' => 'missing', 'ain-Kana' => 'unused' })
+    write_document
+
+    locale.save!
+
+    expect(locale).to be_persisted
+    expect(tag.reload.name('ain')).to eq('レ_ハイタ')
+    expect(TagName.exists?(language_code: 'ain', name: 'unused')).to be(false)
+  end
+
+  it 'matches source names exactly rather than using a case-insensitive collation' do
+    entries.first['ja'] = 'SOURCE'
+    write_document
+
+    expect(described_class.load!(@path, locale:)).to eq({})
+  end
+
+  it 'rejects ambiguous primary matches' do
+    write_document
+    relation = instance_double(ActiveRecord::Relation)
+    allow(TagName).to receive(:where).with(
+        language_code: 'ja', primary_flg: true, name: ['source']).and_return(relation)
+    allow(relation).to receive(:pluck).with(:name, :tag_id)
+        .and_return([['source', tag.id], ['source', tag.id + 1]])
+
+    expect { described_class.load!(@path, locale:) }
+        .to raise_error(described_class::Error, /source.*exactly one tag/)
+  end
+
+  it 'rejects duplicate sources and identifies the offending name' do
+    entries.push({ 'ja' => 'source', 'ain-Kana' => 'another' })
+    write_document
+
+    expect { locale.save! }.to raise_error(described_class::Error, /duplicate source.*source/)
+    expect(Locale.exists?(code: 'ain-Kana')).to be(false)
+  end
+
+  it 'rejects duplicate targets even when a source is missing' do
+    entries.push({ 'ja' => 'missing', 'ain-Kana' => 'レ_ハイタ' })
+    write_document
+
+    expect { locale.save! }.to raise_error(described_class::Error, /duplicate target.*レ_ハイタ/)
+    expect(Locale.exists?(code: 'ain-Kana')).to be(false)
+  end
+
+  it 'rolls back names and histories if a later certified name is invalid' do
+    create(:tag, primary_name: 'second')
+    entries.push({ 'ja' => 'second', 'ain-Kana' => 'nico:invalid' })
+    write_document
+    original_versions = TagVersion.order(:id).map(&:attributes)
+
+    expect { locale.save! }.to raise_error(described_class::Error, /nico:invalid/)
+
+    expect(Locale.exists?(code: 'ain-Kana')).to be(false)
+    expect(TagName.where(language_code: 'ain')).to be_empty
+    expect(TagVersion.order(:id).map(&:attributes)).to eq(original_versions)
+  end
+
+  it 'does not add names or versions on repeated completion' do
+    write_document
+    locale.save!
+    original_names = TagName.order(:id).map(&:attributes)
+    original_versions = TagVersion.order(:id).map(&:attributes)
+
+    TagNameCompletion.for_locale!(locale)
+
+    expect(TagName.order(:id).map(&:attributes)).to eq(original_names)
+    expect(TagVersion.order(:id).map(&:attributes)).to eq(original_versions)
+  end
+end

backend/spec/services/post_bulk_creator_spec.rb

@@ -1,7 +1,7 @@
 require 'rails_helper'
 
 RSpec.describe PostBulkCreator do
-  include_context 'English locale'
+  include_context 'Ainu locale'
 
   it 'limits workers to two and keeps failures in their request slots' do
     locale = Locale.nipponese
@@ -67,8 +67,7 @@ RSpec.describe PostBulkCreator do
     expect(results[3].dig(:post, :id)).to eq(4)
   end
 
-  it 'passes a future English locale to preflight and creation in every worker' do
-    pending '日本語以外の Locale 有効化は別課題で実装する'
+  it 'passes a future Ainu locale to preflight and creation in every worker' do
     locale
     actor = instance_double(User, id: 123)
     allow(User).to receive(:find).with(123).and_return(actor)

backend/spec/services/post_create_plan_spec.rb

@@ -11,23 +11,22 @@ RSpec.describe PostCreatePlan do
   end
 
   context 'with an explicit locale' do
-    include_context 'English locale'
+    include_context 'Ainu locale'
 
     it 'resolves the matching language identity and its parents' do
-      pending '日本語以外の Locale 有効化は別課題で実装する'
       locale
-      english_name = create(:tag_name, name: 'shared_name',
-                                      language_code: 'en', script_code: 'Latn')
-      english = create(:tag, primary_tag_name: english_name, category: :character)
+      ainu_name = create(:tag_name, name: 'shared_name',
+                                      language_code: 'ain', script_code: 'Kana')
+      ainu = create(:tag, primary_tag_name: ainu_name, category: :character)
+      primary_tag_name_for(ainu, 'ja').update!(name: 'ainu_in_japanese', auto_generated: false)
       nipponese = create(:tag, primary_name: 'temporary_nipponese', category: :general)
-      # The DB permits this identity; validation has its own contract spec.
-      primary_tag_name_for(nipponese, 'ja').update_columns(name: 'shared_name')
-      english_parent_name = create(:tag_name, name: 'english_parent',
-                                            language_code: 'en', script_code: 'Latn')
-      english_parent = create(:tag, primary_tag_name: english_parent_name,
+      primary_tag_name_for(nipponese, 'ja').update!(name: 'shared_name')
+      ainu_parent_name = create(:tag_name, name: 'ainu_parent',
+                                            language_code: 'ain', script_code: 'Kana')
+      ainu_parent = create(:tag, primary_tag_name: ainu_parent_name,
                                     category: :material)
       nipponese_parent = create(:tag, primary_name: 'nipponese_parent', category: :general)
-      TagImplication.create!(tag: english, parent_tag: english_parent)
+      TagImplication.create!(tag: ainu, parent_tag: ainu_parent)
       TagImplication.create!(tag: nipponese, parent_tag: nipponese_parent)
 
       plan = described_class.new(attributes: { tags: 'shared_name' }).build!(locale)
@@ -35,35 +34,34 @@ RSpec.describe PostCreatePlan do
       expect(plan[:direct_tag_specs]).to eq(
           [{ name: 'shared_name', category: :character }])
       expect(plan[:post_tag_specs]).to include(
-          { name: primary_tag_name_for(english_parent, 'en').name, category: :material })
+          { name: primary_tag_name_for(ainu_parent, 'ain').name, category: :material })
       expect(plan[:post_tag_specs].pluck(:name))
           .not_to include(primary_tag_name_for(nipponese_parent, 'ja').name)
     end
 
     it 'resolves aliases within the requested language' do
-      pending '日本語以外の Locale 有効化は別課題で実装する'
       locale
       nipponese = create(:tag, primary_name: 'nipponese_canonical')
-      english_name = create(:tag_name, name: 'english_canonical',
-                                      language_code: 'en', script_code: 'Latn')
-      english = create(:tag, primary_tag_name: english_name, category: :character)
+      ainu_name = create(:tag_name, name: 'ainu_canonical',
+                                      language_code: 'ain', script_code: 'Kana')
+      ainu = create(:tag, primary_tag_name: ainu_name, category: :character)
       nipponese_alias = create(:tag_name, :alias, name: 'shared_alias',
                                                   tag: nipponese)
-      english_alias = create(:tag_name, :alias, name: 'shared_alias',
-                                               tag: english,
-                                               language_code: 'en', script_code: 'Latn')
+      ainu_alias = create(:tag_name, :alias, name: 'shared_alias',
+                                               tag: ainu,
+                                               language_code: 'ain', script_code: 'Kana')
 
       expect(nipponese_alias.reload).to have_attributes(
           tag_id: nipponese.id,
           primary_flg: false, language_code: 'ja')
-      expect(english_alias.reload).to have_attributes(
-          tag_id: english.id,
-          primary_flg: false, language_code: 'en')
+      expect(ainu_alias.reload).to have_attributes(
+          tag_id: ainu.id,
+          primary_flg: false, language_code: 'ain')
 
       plan = described_class.new(attributes: { tags: 'shared_alias' }).build!(locale)
 
       expect(plan[:direct_tag_specs]).to eq(
-          [{ name: english_name.name, category: :character }])
+          [{ name: ainu_name.name, category: :character }])
     end
   end
 

backend/spec/services/post_creator_spec.rb

@@ -77,11 +77,10 @@ RSpec.describe PostCreator do
   end
 
   context 'with an explicit locale' do
-    include_context 'English locale'
+    include_context 'Ainu locale'
 
     [false, true].each do |planned|
       it "passes locale to tag creation with planned attributes: #{ planned }" do
-        pending '日本語以外の Locale 有効化は別課題で実装する'
         locale
         attributes = {
             title: 'Locale propagation',
@@ -96,9 +95,10 @@ RSpec.describe PostCreator do
         post = described_class.new(actor:, attributes:).create!(locale)
 
         expect(Tag).to have_received(:find_or_create_by_tag_name!)
-            .with(locale, 'locale_character', category: :character).at_least(:once)
-        tag_name = TagName.find_by!(language_code: 'en', name: 'locale_character')
-        expect(tag_name).to have_attributes(script_code: 'Latn', primary_flg: true)
+            .with(locale, 'locale_character', category: :character,
+                  created_by_user: actor).at_least(:once)
+        tag_name = TagName.find_by!(language_code: 'ain', name: 'locale_character')
+        expect(tag_name).to have_attributes(script_code: 'Kana', primary_flg: true)
         expect(post.tags).to include(tag_name.tag)
       end
     end

backend/spec/services/shared_resource_id_allocator_mysql_spec.rb

@@ -141,6 +141,40 @@ RSpec.describe 'Shared resource IDs across MySQL connections', type: :model do
     result(first)
   end
 
+  [false, true].each do |inner_rollback|
+    [false, true].each do |outer_rollback|
+      it "keeps savepoint=#{ inner_rollback } lock through outer rollback=#{ outer_rollback }" do
+        connection = ApplicationRecord.connection
+        database = connection.pool.db_config.database
+        lock_name = "btrc:ids:#{ Digest::SHA256.hexdigest(database)[0, 16] }:tags"
+        quoted_lock = connection.quote(lock_name)
+        owner = connection.select_value('SELECT CONNECTION_ID()').to_i
+
+        connection.transaction do
+          connection.transaction(requires_new: true) do
+            create_resource(:external)
+            raise ActiveRecord::Rollback if inner_rollback
+          end
+
+          expect(connection.select_value("SELECT IS_USED_LOCK(#{ quoted_lock })").to_i)
+              .to eq(owner)
+          contender = worker do |other|
+            other.select_value("SELECT GET_LOCK(#{ quoted_lock }, 0)").to_i
+          end
+          expect(result(contender)).to eq(0)
+
+          SharedResourceIdAllocator.lock_space!(ExternalTag, 'tags')
+          raise ActiveRecord::Rollback if outer_rollback
+        end
+
+        expect(connection.select_value("SELECT IS_FREE_LOCK(#{ quoted_lock })").to_i)
+            .to eq(1)
+        expect(ExternalTag.exists?(name: "#{ @prefix }_external"))
+            .to eq(!inner_rollback && !outer_rollback)
+      end
+    end
+  end
+
   it 'raises on a real lock acquisition failure without inserting a record' do
     first, (_id, _connection_id, lock_name) = hold_creation(:external, rollback: true)
     stub_const('SharedResourceIdAllocator::LOCK_TIMEOUT', 0)

backend/spec/services/shared_resource_id_allocator_spec.rb

@@ -101,7 +101,7 @@ RSpec.describe SharedResourceIdAllocator, 'lock lifecycle' do
   let(:record) { build(:external_tag) }
   let(:connection) { double('connection') }
   let(:transaction) { double('transaction', open?: true) }
-  let(:callbacks) { { } }
+  let(:callbacks) { [] }
   let(:sql) { [] }
 
   before do
@@ -128,19 +128,24 @@ RSpec.describe SharedResourceIdAllocator, 'lock lifecycle' do
       end
     end
     allow(ExternalTag).to receive(:connection).and_return(connection)
-    allow(ExternalTag).to receive(:current_transaction).and_return(transaction)
+    allow(connection).to receive(:current_transaction).and_return(transaction)
+    allow(connection).to receive(:add_transaction_record) { callbacks << _1 }
+    allow(connection).to receive(:disconnect!)
     allow(ExternalTag).to receive(:uncached).and_yield
-    [:after_commit, :after_rollback].each do |event|
-      allow(transaction).to receive(event) { |&callback| callbacks[event] = callback }
-    end
   end
 
-  [:after_commit, :after_rollback].each do |event|
+  def finish_transaction event
+    allow(transaction).to receive(:open?).and_return(false)
+    callbacks.shift.public_send(event)
+    allow(transaction).to receive(:open?).and_return(true)
+  end
+
+  [:committed!, :rolledback!].each do |event|
     it "holds the shared lock until #{ event }" do
       described_class.assign!(record)
       expect(record.id).to eq(9)
       expect(sql.grep(/RELEASE_LOCK/)).to be_empty
-      callbacks.fetch(event).call
+      finish_transaction(event)
       expect(sql.grep(/RELEASE_LOCK/).size).to eq(1)
     end
   end
@@ -155,7 +160,7 @@ RSpec.describe SharedResourceIdAllocator, 'lock lifecycle' do
   it 'releases a successfully acquired lock when allocation fails and rolls back' do
     allow(connection).to receive(:select_all).and_raise('query failed')
     expect { described_class.assign!(record) }.to raise_error(RuntimeError, 'query failed')
-    callbacks.fetch(:after_rollback).call
+    finish_transaction(:rolledback!)
     expect(sql.grep(/RELEASE_LOCK/).size).to eq(1)
   end
 
@@ -164,18 +169,17 @@ RSpec.describe SharedResourceIdAllocator, 'lock lifecycle' do
     described_class.assign!(record)
     expect(record.id).to eq(50)
     expect(sql.grep(/FOR UPDATE/)).to be_empty
-    callbacks.fetch(:after_commit).call
+    finish_transaction(:committed!)
   end
 
   it 'uses the same named lock within each space and different locks between spaces' do
     locks = [Tag, ExternalTag, TagDescription, TagGroup, TagDescriptionVersion, TagGroupVersion].map do |model|
       allow(model).to receive(:connection).and_return(connection)
-      allow(model).to receive(:current_transaction).and_return(transaction)
       allow(model).to receive(:uncached).and_yield
       record = model.new(id: 50)
       described_class.assign!(record)
       statement = sql.grep(/GET_LOCK/).last
-      callbacks.fetch(:after_commit).call
+      finish_transaction(:committed!)
       statement
     end
     expect(locks[0]).to eq(locks[1])
@@ -187,7 +191,21 @@ RSpec.describe SharedResourceIdAllocator, 'lock lifecycle' do
   it 'reports lock release failures' do
     described_class.assign!(record)
     allow(connection).to receive(:select_value).with(/RELEASE_LOCK/).and_return(nil)
-    expect { callbacks.fetch(:after_commit).call }
+    expect { finish_transaction(:committed!) }
         .to raise_error(ActiveRecord::ActiveRecordError, /lock release failed/)
+    expect(connection).to have_received(:disconnect!)
+  end
+
+  it 'keeps the lock and transfers cleanup when a savepoint rolls back' do
+    described_class.assign!(record)
+    callbacks.shift.rolledback!
+
+    expect(callbacks.size).to eq(1)
+    expect(sql.grep(/RELEASE_LOCK/)).to be_empty
+    described_class.assign!(record)
+    expect(sql.grep(/GET_LOCK/).size).to eq(1)
+
+    finish_transaction(:committed!)
+    expect(sql.grep(/RELEASE_LOCK/).size).to eq(1)
   end
 end

backend/spec/services/tag_name_completion_spec.rb

@@ -0,0 +1,127 @@
+require 'rails_helper'
+
+RSpec.describe TagNameCompletion do
+  let(:author) { create(:user, :member) }
+  let!(:language) { Language.create!(code: 'ain', name: 'ain') }
+  let!(:script) { Script.create!(code: 'Kana', name: 'Kana') }
+  let(:locale) do
+    Locale.create!(code: 'ain-Kana', language_code: 'ain', script_code: 'Kana',
+                   region_code: 392, variants: '', name: 'ain-Kana')
+  end
+
+  it 'generates a phonetic primary with the required identity and provenance' do
+    tag = create(:tag, primary_name: '漢字あカ')
+
+    locale
+
+    expect(tag.reload.tag_name('ain')).to have_attributes(
+        name: 'カンチ_ア_カ', language_code: 'ain', script_code: 'Kana',
+        primary_flg: true, auto_generated: true, tag_id: tag.id)
+  end
+
+  it 'uses the exact fallback when the input cannot be converted' do
+    tag = create(:tag, primary_name: '😀')
+
+    locale
+
+    expect(tag.reload.name('ain')).to eq("Tag_##{ tag.id }")
+  end
+
+  it 'uses the exact fallback when a generated name collides with a human name' do
+    other = create(:tag, primary_name: 'other')
+    create(:tag_name, tag: other, name: 'AbC', language_code: 'ain', script_code: 'Kana')
+    tag = create(:tag, primary_name: 'AbC')
+
+    locale
+
+    expect(tag.reload.name('ain')).to eq("Tag_##{ tag.id }")
+    expect(other.reload.name('ain')).to eq('AbC')
+  end
+
+  it 'uses the exact fallback for a transcription that fails name validation' do
+    tag = create(:tag, primary_name: 'base')
+    source = TagName.new(name: 'nico:invalid', language_code: 'ja')
+
+    expect(TagName.generate_name(locale, tag, source)).to eq("Tag_##{ tag.id }")
+  end
+
+  it 'preserves human confirmation and is idempotent across repeated completion' do
+    locale
+    tag = Tag.find_or_create_by_tag_name!(Locale.nipponese, 'あいぬ', category: :general)
+    primary = tag.tag_name('ain')
+    primary.update!(name: 'human_confirmed', auto_generated: false)
+    snapshot = tag.tag_names.order(:id).map(&:attributes)
+
+    2.times { described_class.for_tag!(tag) }
+
+    expect(tag.tag_names.order(:id).map(&:attributes)).to eq(snapshot)
+  end
+
+  it 'creates one primary per active language through the production creation path' do
+    locale
+
+    tag = Tag.find_or_create_by_tag_name!(Locale.nipponese, 'アイヌ', category: :general)
+
+    expect(tag.tag_names.where(primary_flg: true).pluck(:language_code, :name))
+        .to contain_exactly(['ja', 'アイヌ'], ['ain', 'アイヌ'])
+    expect(Tag.find_or_create_by_tag_name!(locale, 'アイヌ', category: :general)).to eq(tag)
+  end
+
+  ['ja', 'ain'].each do |language|
+    it "records one authored create with all names for a #{ language } origin" do
+      ainu_locale = locale
+      origin = language == 'ja' ? Locale.nipponese : ainu_locale
+      tag = nil
+
+      expect {
+        tag = Tag.find_or_create_by_tag_name!(origin, 'アイヌ', category: :general,
+                                             created_by_user: author)
+      }.to change(TagVersion, :count).by(1)
+
+      version = tag.tag_versions.sole
+      expect(version).to have_attributes(
+          event_type: 'create', version_no: 1, created_by_user_id: author.id)
+      expect(tag.reload.version_no).to eq(1)
+      expect(version.names).to eq(
+          'ja' => { 'name' => 'アイヌ', 'script_code' => 'Jpan',
+                    'auto_generated' => language != 'ja', 'aliases' => [] },
+          'ain' => { 'name' => 'アイヌ', 'script_code' => 'Kana',
+                     'auto_generated' => language != 'ain', 'aliases' => [] })
+
+      expect {
+        described_class.for_tag!(tag, created_by_user: author)
+        found = Tag.find_or_create_by_tag_name!(origin, 'アイヌ', category: :general,
+                                               created_by_user: author)
+        expect(found).to eq(tag)
+        TagVersioning.record_tag_snapshot!(tag, created_by_user: author)
+      }.not_to change(TagVersion, :count)
+      expect(version.reload.created_by_user_id).to eq(author.id)
+    end
+  end
+
+  it 'records the author even when no additional language needs completion' do
+    tag = build(:tag, primary_name: 'single_language_creation')
+
+    described_class.for_tag!(tag, created_by_user: author)
+
+    expect(tag).to be_persisted
+    expect(tag.tag_versions.sole).to have_attributes(
+        event_type: 'create', version_no: 1, created_by_user_id: author.id)
+    expect(tag.tag_versions.sole.names.keys).to eq(['ja'])
+  end
+
+  it 'rolls back a new tag and all names when its create history fails' do
+    locale
+    author
+    before_counts = [Tag.count, TagName.count, TagVersion.count]
+    allow(TagVersioning).to receive(:record!).and_raise('history failed')
+
+    expect {
+      Tag.find_or_create_by_tag_name!(Locale.nipponese, 'atomic_new_history',
+                                     category: :general, created_by_user: author)
+    }.to raise_error('history failed')
+
+    expect([Tag.count, TagName.count, TagVersion.count]).to eq(before_counts)
+    expect(TagName.where(name: 'atomic_new_history')).to be_empty
+  end
+end

backend/spec/services/tag_name_transcription_spec.rb

@@ -0,0 +1,37 @@
+require 'rails_helper'
+
+RSpec.describe TagNameTranscription do
+  {
+      'AbCdXYZ' => 'AbCdXYZ',
+      'あいぬ' => 'アイヌ',
+      'アイヌ' => 'アイヌ',
+      '日本語' => 'ニチホンコ',
+      '漢字' => 'カンチ',
+      '漢あカ' => 'カン_ア_カ',
+      '漢字あいうカナ' => 'カンチ_アイウ_カナ',
+      'Ab漢あカZ' => 'Abカン_ア_カZ',
+      'りゃリュリョ' => 'リヤ_リユリヨ',
+      'キャット' => 'キヤット',
+      'コーヒー' => 'コヒ',
+      'コウコオケイケエカア' => 'コウコオケイケエカア',
+      'ガギグゲゴダヂヅデド' => 'カキクケコタチチュテト',
+      'バビブベボパピプペポ' => 'パピプペポパピプペポ',
+      'ザジズゼゾ' => 'チャチチュチェチョ',
+      'ジャジュジョ' => 'チャチュチョ',
+      'アㇰアㇱアッアンアㇺアㇷ゚' => 'アㇰアㇱアッアンアㇺアㇷ゚',
+      'アㇻイㇼウㇽエㇾオㇿ' => 'アㇻイㇼウㇽエㇾオㇿ',
+      '漢Aあ' => 'カンAア' }.each do |source, expected|
+    it "transcribes #{ source } as #{ expected }" do
+      expect(described_class.ainu(source)).to eq(expected)
+    end
+  end
+
+  { '😀' => '', 'ヴ' => '', 'ティ' => 'テ', 'ㇵ' => '',
+    '魑' => '', '𠮷' => '', 'ー' => '', '々' => '',
+    'ア😀😀イ' => 'ア_イ', '😀アイ😀' => 'アイ',
+    '_😀_' => '__', 'ア_😀_イ' => 'ア___イ', '漢魑字' => 'カン_チ' }.each do |source, expected|
+    it "preserves convertible portions of #{ source }" do
+      expect(described_class.ainu(source)).to eq(expected)
+    end
+  end
+end

backend/spec/services/tag_version_recorder_spec.rb

@@ -1,7 +1,7 @@
 require 'rails_helper'
 
 RSpec.describe TagVersionRecorder do
-  include_context 'English locale'
+  include_context 'Ainu locale'
 
   let(:user) { create_member_user! }
   let!(:tag) { create(:tag, primary_name: '日本語名') }
@@ -17,11 +17,11 @@ RSpec.describe TagVersionRecorder do
                     { 'name' => 'alias_z', 'script_code' => 'Jpan' }] }
   end
 
-  def prepare_english_names!
+  def prepare_ainu_names!
     locale
-    primary_tag_name_for(tag, 'en').update!(name: 'English name', auto_generated: false)
-    create(:tag_name, :alias, tag:, language_code: 'en', script_code: 'Latn',
-                              name: 'English alias')
+    primary_tag_name_for(tag, 'ain').update!(name: 'Ainu name', auto_generated: false)
+    create(:tag_name, :alias, tag:, language_code: 'ain', script_code: 'Kana',
+                              name: 'Ainu alias')
   end
 
   it 'snapshots the Nipponese primary and sorted aliases in grouped names' do
@@ -62,40 +62,37 @@ RSpec.describe TagVersionRecorder do
   end
 
   it 'snapshots future languages together without a request locale argument' do
-    pending '日本語以外の Locale 有効化は別課題で実装する'
-    prepare_english_names!
+    prepare_ainu_names!
 
-    version = described_class.record!(tag:, event_type: :create, created_by_user: user)
+    version = described_class.record!(tag:, event_type: :update, created_by_user: user)
 
     expect(version.names).to eq(
         'ja' => nipponese_snapshot,
-        'en' => { 'name' => 'English name', 'script_code' => 'Latn',
+        'ain' => { 'name' => 'Ainu name', 'script_code' => 'Kana',
                   'auto_generated' => false,
-                  'aliases' => [{ 'name' => 'English alias', 'script_code' => 'Latn' }] })
+                  'aliases' => [{ 'name' => 'Ainu alias', 'script_code' => 'Kana' }] })
   end
 
-  it 'creates a version for an English-only change and preserves prior names' do
-    pending '日本語以外の Locale 有効化は別課題で実装する'
-    prepare_english_names!
-    original = described_class.record!(tag:, event_type: :create, created_by_user: user)
-    primary_tag_name_for(tag, 'en').update!(name: 'Renamed')
+  it 'creates a version for an Ainu-only change and preserves prior names' do
+    prepare_ainu_names!
+    original = described_class.record!(tag:, event_type: :update, created_by_user: user)
+    primary_tag_name_for(tag, 'ain').update!(name: 'Renamed')
 
     updated = described_class.record!(tag:, event_type: :update, created_by_user: user)
 
-    expect(updated.version_no).to eq(2)
-    expect(original.reload.names.fetch('en')).to include('name' => 'English name')
-    expect(updated.names.fetch('en')).to include('name' => 'Renamed')
+    expect(updated.version_no).to eq(original.version_no + 1)
+    expect(original.reload.names.fetch('ain')).to include('name' => 'Ainu name')
+    expect(updated.names.fetch('ain')).to include('name' => 'Renamed')
     expect(updated.names.fetch('ja')).to eq(nipponese_snapshot)
   end
 
   it 'does not create a version for an unchanged multilingual snapshot' do
-    pending '日本語以外の Locale 有効化は別課題で実装する'
-    prepare_english_names!
-    described_class.record!(tag:, event_type: :create, created_by_user: user)
+    prepare_ainu_names!
+    original = described_class.record!(tag:, event_type: :update, created_by_user: user)
 
     unchanged = described_class.record!(tag:, event_type: :update, created_by_user: user)
 
-    expect(unchanged.version_no).to eq(1)
-    expect(tag.reload.tag_versions.count).to eq(1)
+    expect(unchanged.version_no).to eq(original.version_no)
+    expect(tag.reload.tag_versions.count).to eq(original.version_no)
   end
 end

backend/spec/support/ainu_locale_contract.rb

@@ -1,19 +1,22 @@
 RSpec.shared_context 'Ainu locale contract' do
-  let(:ainu_locale) { instance_double(Locale, language_code: 'ain', script_code: 'Jpan') }
+  let(:ainu_locale) do
+    instance_double(Locale, language_code: 'ain', script_code: 'Kana', deprecated_at: nil)
+  end
 
   before do
-    # Only the foreign-key reference is seeded; no Locale or enum is enabled.
+    # Keep description contracts independent of locale activation and backfill.
     Language.connection.execute(<<~SQL)
       INSERT IGNORE INTO languages (code, name, created_at)
       VALUES ('ain', 'Ainu', CURRENT_TIMESTAMP)
     SQL
+    Script.find_or_create_by!(code: 'Kana') { _1.name = 'Kana' }
     allow(Locale).to receive(:find_by).and_call_original
-    allow(Locale).to receive(:find_by).with(code: 'ain').and_return(ainu_locale)
+    allow(Locale).to receive(:find_by).with(code: 'ain-Kana').and_return(ainu_locale)
   end
 
   def add_ainu_name tag, name
     TagName.insert_all!([{
-        tag_id: tag.id, language_code: 'ain', script_code: 'Jpan', name:,
+        tag_id: tag.id, language_code: 'ain', script_code: 'Kana', name:,
         primary_flg: true, auto_generated: false,
         created_at: Time.current, updated_at: Time.current }])
     tag.tag_names.reset

backend/spec/support/auth_helper.rb

@@ -1,4 +1,16 @@
 module AuthHelper
+  def cookie_headers(user)
+    env = Rails.application.env_config.merge(Rack::MockRequest.env_for('/'))
+    endpoint = lambda do |request_env|
+      ActionDispatch::Request.new(request_env).session[:inheritance_code] = user.inheritance_code
+      [200, {}, []]
+    end
+    store = ActionDispatch::Session::CookieStore.new(
+        endpoint, Rails.application.config.session_options)
+    headers = ActionDispatch::Cookies.new(store).call(env)[1]
+    { 'Cookie' => Array(headers['set-cookie']).map { _1.split(';').first }.join('; ') }
+  end
+
   def sign_in_as(user)
     allow_any_instance_of(ApplicationController)
       .to receive(:current_user).and_return(user)

backend/spec/support/locale_context.rb

@@ -1,22 +1,17 @@
-RSpec.shared_context 'English locale' do
-  def prepare_english_reference!
-    Language.find_or_create_by!(code: 'en') { _1.name = 'English' }
-    Script.find_or_create_by!(code: 'Latn') { _1.name = 'Latin' }
-    region_class = Class.new(ApplicationRecord) { self.table_name = 'regions' }
-    region_class.find_or_create_by!(code: 826) do |record|
-      record.alpha_code = 'GB'
-      record.name = 'United Kingdom'
-    end
+RSpec.shared_context 'Ainu locale' do
+  def prepare_ainu_reference!
+    Language.find_or_create_by!(code: 'ain') { _1.name = 'ain' }
+    Script.find_or_create_by!(code: 'Kana') { _1.name = 'Kana' }
   end
 
   let(:locale) do
-    prepare_english_reference!
-    Locale.find_or_create_by!(code: 'en') do |record|
-      record.language_code = 'en'
-      record.script_code = 'Latn'
-      record.region_code = 826
+    prepare_ainu_reference!
+    Locale.find_or_create_by!(code: 'ain-Kana') do |record|
+      record.language_code = 'ain'
+      record.script_code = 'Kana'
+      record.region_code = 392
       record.variants = ''
-      record.name = 'English'
+      record.name = 'Ainu'
     end
   end
 end

docs/commands.md

@@ -37,3 +37,56 @@ npm run test:run
 cd backend && bundle exec rspec
 cd ../frontend && npm run test:run && npm run build && npm run lint
 ```
+
+### Help SSR in production
+
+Build both `dist/client` and `dist/server` with `npm run build`, deploy them
+together, and restart the Node process. `npm run dev` and `npm run preview`
+remain CSR servers; use `npm start` for SSR. The old sitemap generator is not
+part of this build.
+
+The following environment is a deployment proposal, not an applied VPS change:
+
+```sh
+cd frontend
+export NODE_ENV=production
+export HOST=127.0.0.1
+export PORT=5174
+export PUBLIC_ORIGIN=https://hub.nizika.monster
+export SSR_API_BASE_URL=http://127.0.0.1:3002
+npm start
+```
+
+Run this command through the VPS's process supervisor. Port 5174 avoids the
+Vite development port 5173. Rails remains on 127.0.0.1:3002. `PUBLIC_ORIGIN`
+must match the public HTTPS origin, including any non-default port; redirect
+alternate hostnames to that origin. `SSR_API_BASE_URL` configures server-side
+public API requests only. Keep the browser's existing API configuration pointed
+at the public `/api` endpoint.
+
+Inside the existing Apache HTTPS virtual host, with `proxy`, `proxy_http` and
+`headers` enabled, preserve the API rules before the catch-all frontend rule:
+
+```apache
+ProxyPreserveHost On
+RequestHeader set X-Forwarded-Proto "https"
+
+ProxyPass        "/api/" "http://127.0.0.1:3002/"
+ProxyPassReverse "/api/" "http://127.0.0.1:3002/"
+
+ProxyPass        "/" "http://127.0.0.1:5174/"
+ProxyPassReverse "/" "http://127.0.0.1:5174/"
+```
+
+Retain existing TLS, authentication-header handling and any exact `/api` rule.
+Replace the previous SPA catch-all rewrite instead of rewriting Help or missing
+URLs to `index.html` before they reach Node. Do not override Node's 404/503
+responses with an SPA fallback or cache its HTML. Hashed assets may be cached;
+deployments must keep old hashed files available for already-open clients.
+
+Only Help detail pages are server-rendered. Known CSR routes remain client
+rendered, old known routes redirect to Japanese URLs, and unknown routes/assets
+return 404. A failed Help preload keeps the readable server HTML, retries on
+online/focus/pageshow, and permits one automatic reload per bundle and URL in
+session storage. If storage is unavailable or the failure persists, the HTML
+remains intact; native links and manual reload remain available.

frontend/AGENTS.md

@@ -33,9 +33,9 @@ npm run lint
 
 If either command cannot be run or fails, report the exact command and failure.
 
-Do not create, modify, or run tests unless the user explicitly asks for test
-work. When the user asks for tests, keep working and rerun them until they
-pass or the remaining failure is clearly blocked.
+明示的な個別指示がない限り、テストの追加・修正・削除・実行を一切行わない。
+fixture、mock、snapshot、テスト補助コード及び既存のテスト差分にも触れない。
+ビルド・lint・静的確認を使い、未確認事項はそのまま報告する。
 
 ## TypeScript
 
@@ -128,6 +128,19 @@ pass or the remaining failure is clearly blocked.
 
 ## Tailwind and UI
 
+- 原則として、ユーザ向け UI 文言を TSX / TypeScript に直接記述しない。
+  新しい文言は既存の i18n システムで管理し、適切な既存キーを先に確認する。
+  不必要な重複定義を避け、新規機能固有の文言は適切な namespace にまとめる。
+- 対応 locale の辞書を整合させる。未翻訳項目には既存の日本語 fallback と
+  `_untranslated` 規約を使い、language metadata を維持する。
+  翻訳を捏造せず、未翻訳文字列を正式な翻訳として登録しない。
+- UI 文言の追加・変更時はビルド、静的検査、実画面の確認等で、辞書と
+  SSR / hydration の整合及び翻訳キーの非露出を検証する。
+  i18n の検証を理由にテスト関連作業を開始しない。
+- API の内部識別子、パラメータ、ユーザ入力データ、外部 URL は機械的に
+  翻訳しない。ボタン、項目名、CSV ヘッダ、エラー、空状態、ツールチップ、
+  アクセシビリティ用ラベルも UI 文言として扱う。
+
 - Tailwind scans `src/**/*.{html,js,ts,jsx,tsx,mdx}`.
 - Use `cn` from `src/lib/utils.ts` for conditional class names and class merging.
 - In JavaScript, JSX, TypeScript, and TSX, use `cn` from `@/lib/utils`
@@ -144,7 +157,7 @@ pass or the remaining failure is clearly blocked.
   heavy borders, or nested panel decoration unless the surrounding screen
   already uses them.
 - Keep operational screens dense and direct; trim explanatory copy and use
-  short Japanese labels that fit the control.
+  short localised labels that fit the control.
 - Preserve existing Japanese tone and orthography in nearby UI text, including
   old-kana wording where the file already uses it.
 - Do not add user-facing copy, helper text, descriptions, notes, tooltips,

frontend/index.html

@@ -4,35 +4,13 @@
     <meta charset="UTF-8" />
     <link rel="icon" href="/favicon.ico" />
     <meta name="viewport" content="width=device-width, initial-scale=1.0" />
-    <meta name="description" content="ぼざクリ ぼざろクリーチャーシリーズ 伊地知ニジカ リンク集 Wiki ニコニコ" />
+    <meta name="description" lang="ja" data-rh="true" content="ぼざクリ ぼざろクリーチャーシリーズ 伊地知ニジカ リンク集 Wiki ニコニコ" />
     <title>ぼざクリ タグ広場　〜 ぼざろクリーチャーシリーズ綜合リンク集</title>
     <!-- helmet -->
   </head>
   <body>
-    <div id="root">
-      <div class="flex flex-col h-screen w-screen">
-        <nav class="px-3 flex justify-between items-center w-full min-h-[48px]
-                    bg-yellow-200 dark:bg-red-975 md:bg-yellow-50">
-          <div class="flex items-center gap-2 h-full">
-            <a class="mx-4 text-xl font-bold text-pink-600 hover:text-pink-400
-                      dark:text-pink-300 dark:hover:text-pink-100"
-               href="/">
-              ぼざクリ タグ広場
-            </a>
-            <a class="hidden md:flex h-full items-center px-2" href="/posts">広場</a>
-            <a class="hidden md:flex h-full items-center px-2" href="/tags">タグ</a>
-            <a class="hidden md:flex h-full items-center px-2" href="/wiki/ヘルプ:ホーム">Wiki</a>
-            <a class="hidden md:flex h-full items-center px-2" href="/users">ユーザ</a>
-          </div>
-          <a href="#" class="md:hidden ml-auto pr-4
-                             text-pink-600 hover:text-pink-400
-                             dark:text-pink-300 dark:hover:text-pink-100">
-            Menu
-          </a>
-        </nav>
-      </div>
-      <!-- outlet -->
-    </div>
+    <div id="root"><!-- outlet --></div>
+    <!-- ssr-state -->
     <script type="module" src="/src/main.tsx"></script>
   </body>
 </html>

frontend/package-lock.json

@@ -25,12 +25,14 @@
         "clsx": "^2.1.1",
         "framer-motion": "^12.23.26",
         "humps": "^2.0.1",
+        "i18next": "^26.4.7",
         "lucide-react": "^0.511.0",
         "markdown-it": "^14.1.0",
         "path-to-regexp": "^8.3.0",
         "react": "^19.1.0",
         "react-dom": "^19.1.0",
         "react-helmet-async": "^2.0.5",
+        "react-i18next": "^17.0.20",
         "react-markdown": "^10.1.0",
         "react-markdown-editor-lite": "^1.3.4",
         "react-router-dom": "^6.30.1",
@@ -350,9 +352,9 @@
       }
     },
     "node_modules/@babel/runtime": {
-      "version": "7.27.6",
-      "resolved": "https://registry.npmjs.org/@babel/runtime/-/runtime-7.27.6.tgz",
-      "integrity": "sha512-vbavdySgbTTrmFE+EsiqUTzlOr5bzlnJtUv9PynGCAKvfQqjIXbvFdumPM/GxMDfyuGMJaJAU6TO4zc1Jf1i8Q==",
+      "version": "7.29.10",
+      "resolved": "https://registry.npmjs.org/@babel/runtime/-/runtime-7.29.10.tgz",
+      "integrity": "sha512-NpugTzbKgGrNe45Ui32cN8vCFFMxVtP/9rtfwv0nP5FRDAjvYBxJcLVpYA9mr1jxP6cnIT7x9LUzuDTbWYYNRA==",
       "license": "MIT",
       "engines": {
         "node": ">=6.9.0"
@@ -4872,6 +4874,15 @@
         "node": ">=18"
       }
     },
+    "node_modules/html-parse-stringify": {
+      "version": "4.0.1",
+      "resolved": "https://registry.npmjs.org/html-parse-stringify/-/html-parse-stringify-4.0.1.tgz",
+      "integrity": "sha512-0zHsZJrK7S3K2aucXWL6ycoYJ/iNtIcFHC/nYQgFklPtrv5LpJctIiSCroWZWeuoXvuyFdzp6KzjJQ+OT5MfFw==",
+      "license": "MIT",
+      "funding": {
+        "url": "https://locize.com"
+      }
+    },
     "node_modules/html-url-attributes": {
       "version": "3.0.1",
       "resolved": "https://registry.npmjs.org/html-url-attributes/-/html-url-attributes-3.0.1.tgz",
@@ -4916,6 +4927,34 @@
       "integrity": "sha512-E0eIbrFWUhwfXJmsbdjRQFQPrl5pTEoKlz163j1mTqqUnU9PgR4AgB8AIITzuB3vLBdxZXyZ9TDIrwB2OASz4g==",
       "license": "MIT"
     },
+    "node_modules/i18next": {
+      "version": "26.4.7",
+      "resolved": "https://registry.npmjs.org/i18next/-/i18next-26.4.7.tgz",
+      "integrity": "sha512-p/3hqy6EcuqRs6wNwBYwGGC1fzBJSMxV9zMuN814ab/7QjdZbXfjXwuPZdQbngX6KDOTxM01uUiZyqmMB8ghZg==",
+      "funding": [
+        {
+          "type": "individual",
+          "url": "https://www.locize.com/i18next"
+        },
+        {
+          "type": "individual",
+          "url": "https://www.i18next.com/how-to/faq#i18next-is-awesome.-how-can-i-support-the-project"
+        },
+        {
+          "type": "individual",
+          "url": "https://www.locize.com"
+        }
+      ],
+      "license": "MIT",
+      "peerDependencies": {
+        "typescript": "^5 || ^6 || ^7"
+      },
+      "peerDependenciesMeta": {
+        "typescript": {
+          "optional": true
+        }
+      }
+    },
     "node_modules/iconv-lite": {
       "version": "0.6.3",
       "resolved": "https://registry.npmjs.org/iconv-lite/-/iconv-lite-0.6.3.tgz",
@@ -7258,6 +7297,33 @@
         "react": "^16.6.0 || ^17.0.0 || ^18.0.0"
       }
     },
+    "node_modules/react-i18next": {
+      "version": "17.0.20",
+      "resolved": "https://registry.npmjs.org/react-i18next/-/react-i18next-17.0.20.tgz",
+      "integrity": "sha512-rzSSirf0NP9vfcUXHZAksIuyMWl7L/T/7nm8S+sSIFuIzku54qcyyVAOZXbawPNpUxGkDx/eosSv4DrpzcxuOQ==",
+      "license": "MIT",
+      "dependencies": {
+        "@babel/runtime": "^7.29.7",
+        "html-parse-stringify": "^4.0.1",
+        "use-sync-external-store": "^1.6.0"
+      },
+      "peerDependencies": {
+        "i18next": ">= 26.2.0",
+        "react": ">= 16.8.0",
+        "typescript": "^5 || ^6 || ^7"
+      },
+      "peerDependenciesMeta": {
+        "react-dom": {
+          "optional": true
+        },
+        "react-native": {
+          "optional": true
+        },
+        "typescript": {
+          "optional": true
+        }
+      }
+    },
     "node_modules/react-is": {
       "version": "16.13.1",
       "resolved": "https://registry.npmjs.org/react-is/-/react-is-16.13.1.tgz",
@@ -8595,6 +8661,15 @@
         }
       }
     },
+    "node_modules/use-sync-external-store": {
+      "version": "1.7.0",
+      "resolved": "https://registry.npmjs.org/use-sync-external-store/-/use-sync-external-store-1.7.0.tgz",
+      "integrity": "sha512-6L+EeigHMQhdaIPNIFUKwfWJSwWFQ8gJbJ2DLOs5sDIegTwR9fRxvnM3uciHKjIZhFz+KAv2emhWMRvDmMcY8A==",
+      "license": "MIT",
+      "peerDependencies": {
+        "react": "^16.8.0 || ^17.0.0 || ^18.0.0 || ^19.0.0"
+      }
+    },
     "node_modules/util-deprecate": {
       "version": "1.0.2",
       "resolved": "https://registry.npmjs.org/util-deprecate/-/util-deprecate-1.0.2.tgz",

frontend/package.json

@@ -5,12 +5,15 @@
   "type": "module",
   "scripts": {
     "dev": "vite",
-    "build": "tsc -b && vite build",
-    "postbuild": "node scripts/generate-sitemap.js",
+    "build": "tsc -b && npm run build:client && npm run build:server",
+    "build:client": "vite build --outDir dist/client",
+    "build:server": "vite build --ssr src/entry-server.tsx --outDir dist/server",
+    "start": "node server.mjs",
     "lint": "eslint .",
     "test": "vitest",
     "test:run": "vitest run",
-    "preview": "vite preview"
+    "test:ssr": "node --test server.ssr.test.mjs",
+    "preview": "vite preview --outDir dist/client"
   },
   "dependencies": {
     "@dnd-kit/core": "^6.3.1",
@@ -29,12 +32,14 @@
     "clsx": "^2.1.1",
     "framer-motion": "^12.23.26",
     "humps": "^2.0.1",
+    "i18next": "^26.4.7",
     "lucide-react": "^0.511.0",
     "markdown-it": "^14.1.0",
     "path-to-regexp": "^8.3.0",
     "react": "^19.1.0",
     "react-dom": "^19.1.0",
     "react-helmet-async": "^2.0.5",
+    "react-i18next": "^17.0.20",
     "react-markdown": "^10.1.0",
     "react-markdown-editor-lite": "^1.3.4",
     "react-router-dom": "^6.30.1",

frontend/scripts/generate-sitemap.js

@@ -11,7 +11,8 @@ const formatDate = (date = new Date) => {
   return `${ year }-${ month }-${ day }`
 }
 
-const SITE_TITLE = 'ぼざクリ タグ広場'
+const SITE_TITLE = JSON.parse (fs.readFileSync (
+    new URL ('../src/locales/ja/shared.json', import.meta.url), 'utf8')).labels.brand
 const DOMAIN = 'https://hub.nizika.monster'
 const API_BASE_URL = 'https://hub.nizika.monster/api'
 

frontend/server.mjs

@@ -0,0 +1,136 @@
+import { createReadStream } from 'node:fs'
+import { readFile, stat } from 'node:fs/promises'
+import { createServer, request as requestHTTP } from 'node:http'
+import { request as requestHTTPS } from 'node:https'
+import path from 'node:path'
+import { fileURLToPath } from 'node:url'
+
+import { render, renderSitemap } from './dist/server/entry-server.js'
+
+const root = fileURLToPath (new URL ('./dist/client/', import.meta.url))
+const template = await readFile (path.join (root, 'index.html'), 'utf8')
+const origin = new URL (process.env.PUBLIC_ORIGIN ?? 'http://localhost:5173').origin
+const apiBaseURL = process.env.SSR_API_BASE_URL ?? 'http://127.0.0.1:3002'
+const types = {
+    '.js': 'text/javascript', '.css': 'text/css', '.json': 'application/json',
+    '.png': 'image/png', '.gif': 'image/gif', '.jpg': 'image/jpeg',
+    '.svg': 'image/svg+xml', '.ico': 'image/x-icon', '.webp': 'image/webp',
+    '.woff': 'font/woff', '.woff2': 'font/woff2', '.otf': 'font/otf',
+    '.mp4': 'video/mp4', '.mp3': 'audio/mpeg', '.txt': 'text/plain' }
+
+if (process.env.NODE_ENV === 'production' && !process.env.PUBLIC_ORIGIN)
+  throw new Error ('PUBLIC_ORIGIN is required in production')
+
+const server = createServer (async (request, response) => {
+  response.setHeader ('Cache-Control', 'private, no-store')
+  const forwardedFor = request.headers['x-forwarded-for'] ?? request.socket.remoteAddress
+  if (request.url === '/api' || request.url.startsWith ('/api/'))
+  {
+    const address = new URL (request.url, origin)
+    const target = new URL (apiBaseURL)
+    target.pathname = target.pathname.replace (/\/$/, '') + address.pathname.slice (4)
+    target.search = address.search
+    const send = target.protocol === 'https:' ? requestHTTPS : requestHTTP
+    const upstream = send (target, {
+      method: request.method,
+      headers: { ...request.headers, host: target.host,
+	'x-forwarded-host': new URL (origin).host,
+	'x-forwarded-proto': new URL (origin).protocol.replace (':', ''),
+	'x-forwarded-for': forwardedFor } }, result => {
+      response.writeHead (result.statusCode ?? 502, result.headers)
+      result.on ('error', () => response.destroy ())
+      result.pipe (response)
+    })
+    upstream.setTimeout (10_000, () => upstream.destroy (new Error ('API timeout')))
+    upstream.on ('error', () => {
+      if (response.headersSent)
+	response.destroy ()
+      else
+	response.writeHead (503).end ()
+    })
+    request.on ('aborted', () => upstream.destroy ())
+    request.pipe (upstream)
+    return
+  }
+  if (!['GET', 'HEAD'].includes (request.method))
+  {
+    response.writeHead (405, { Allow: 'GET, HEAD' }).end ()
+    return
+  }
+  try
+  {
+    const url = new URL (request.url, origin)
+    const pathname = decodeURIComponent (url.pathname)
+    if (pathname === '/sitemap.xml' || pathname.startsWith ('/sitemap-'))
+    {
+      const result = await renderSitemap (url.pathname, origin, apiBaseURL)
+      response.writeHead (result.status, { 'Content-Type': 'application/xml; charset=utf-8' })
+      response.end (request.method === 'HEAD' ? undefined : result.body)
+      return
+    }
+    if (pathname === '/robots.txt')
+    {
+      response.writeHead (200, { 'Content-Type': 'text/plain; charset=utf-8' })
+      response.end (request.method === 'HEAD'
+	  ? undefined : `Sitemap: ${new URL ('/sitemap.xml', origin).href}\n`)
+      return
+    }
+    const file = path.resolve (root, '.' + pathname)
+    const allowed = file.startsWith (root)
+        && !pathname.split ('/').some (segment => segment.startsWith ('.'))
+        && pathname !== '/index.html'
+    const info = allowed ? await stat (file).catch (() => null) : null
+    if (info?.isFile ())
+    {
+      response.writeHead (200, {
+	'Content-Type': types[path.extname (file)] ?? 'application/octet-stream',
+	'Content-Length': info.size,
+	'Cache-Control': /\/[^/]+-[\w-]{8}\.[^.]+$/.test (pathname)
+	    ? 'public, max-age=31536000, immutable' : 'public, max-age=3600' })
+      if (request.method === 'HEAD')
+	response.end ()
+      else
+	createReadStream (file).on ('error', () => response.destroy ()).pipe (response)
+      return
+    }
+    if (pathname.startsWith ('/assets/'))
+    {
+      response.writeHead (404).end ()
+      return
+    }
+    const result = await render (url.pathname + url.search, origin, apiBaseURL, {
+      cookie: request.headers.cookie, forwardedFor })
+    if (result?.setCookies?.length > 0)
+      response.setHeader ('Set-Cookie', result.setCookies)
+    if (result?.location != null)
+    {
+      response.writeHead (result.status, { Location: result.location }).end ()
+      return
+    }
+    const html = result?.html == null
+        ? template.replace ('<!-- helmet -->', result?.status === 404
+            ? '<meta name="robots" content="noindex" data-rh="true">' : '')
+        : template
+	.replace ('lang="ja"', `lang="${result.locale}"`)
+	.replace (/<title>[\s\S]*?<\/title>/, '')
+	.replace (/<meta name="description"[^>]*>/, '')
+	.replace ('<!-- helmet -->', () => result.head)
+	.replace ('<!-- outlet -->', () => result.html)
+	.replace ('<!-- ssr-state -->',
+	    () => `<script id="ssr-state" type="application/json">${result.bootstrap}</script>`)
+    response.writeHead (result?.status ?? 200, {
+	'Content-Type': 'text/html; charset=utf-8' })
+    response.end (request.method === 'HEAD' ? undefined : html)
+  }
+  catch (error)
+  {
+    console.error ('[SSR]', error instanceof Error ? error.message : 'Rendering failed')
+    const denied = error?.response?.status === 401 || error?.response?.status === 403
+    response.writeHead (error instanceof URIError ? 400
+      : (denied ? error.response.status : 503)).end ()
+  }
+})
+
+server.listen (Number (process.env.PORT ?? 5173), process.env.HOST ?? '127.0.0.1', () => {
+  console.info ('[SSR] listening on', server.address ().port)
+})

frontend/server.ssr.test.mjs

@@ -0,0 +1,750 @@
+import assert from 'node:assert/strict'
+import { createServer } from 'node:http'
+import { spawn } from 'node:child_process'
+import { after, before, test } from 'node:test'
+import { createServer as createViteServer } from 'vite'
+
+import { render } from './dist/server/entry-server.js'
+
+const origin = 'https://ssr.example.invalid'
+const date = '2026-09-15T00:00:00+09:00'
+let api, apiURL, routes, vite, node, httpOrigin
+let failAPI = false
+const requests = []
+// Rails owns encryption and verification; this upstream fixture tests Node's forwarding contract.
+const recoveryCode = 'test-recovery-secret'
+const users = new Map ([
+  [recoveryCode, { id: 1, name: 'SSR account', role: 'admin' }],
+  ['second-recovery-secret', { id: 2, name: 'Second account', role: 'member' }]])
+const sessions = new Map ()
+let sessionSequence = 0
+const cookieName = '__Host-btrc-session'
+const cookieFor = value => `${cookieName}=${value}`
+const sessionValue = request => request.headers.cookie?.split (';')
+  .map (part => part.trim ()).find (part => part.startsWith (`${cookieName}=`))
+  ?.slice (cookieName.length + 1)
+const issueSession = (response, code = null) => {
+  const value = `opaque-rails-session-${++sessionSequence}`
+  sessions.set (value, { code, token: `csrf-${sessionSequence}` })
+  refreshCookie (response, value)
+  return value
+}
+const refreshCookie = (response, value) => response.setHeader ('Set-Cookie',
+  `${cookieFor (value)}; Path=/; Max-Age=630720000; HttpOnly; Secure; SameSite=Lax`)
+const tag = locale => ({
+    id: 1, name: locale === 'ja' ? 'SSR タグ' : 'SSR　シロシ', category: 'general',
+    deprecated_at: null, aliases: [], parents: [], children: [], post_count: 1,
+    created_at: date, updated_at: date, has_wiki: true, material_id: null,
+    has_deerjikists: false, sections: [] })
+const post = locale => ({
+    id: 1, version_no: 1, title: `SSR post ${locale}`, url: 'https://example.invalid/post',
+    thumbnail: null, thumbnail_base: null, video_ms: null, tags: [tag (locale)],
+    parent_posts: [], child_posts: [], sibling_posts: {}, viewed: false, related: [],
+    original_created_from: date, original_created_before: date,
+    created_at: date, updated_at: date, uploaded_user: null })
+const wiki = locale => ({
+    id: 1, tag_id: 1, resource_type: 'tag_description', language_code: locale === 'ja'
+    ? 'ja' : 'ain', title: tag (locale).name, body: `SSR wiki body ${locale}`,
+    created_at: date, updated_at: date, revision_id: 1, pred: null, succ: null,
+    deprecated_at: null })
+const material = locale => ({
+    id: 1, version_no: 1, tag: tag (locale), file: null, url: 'https://example.invalid',
+    thumbnail: null, thumbnail_fallback_text: 'SSR material',
+    thumbnail_fallback_kind: 'tag_name', media_kind: 'url_only', content_type: null,
+    file_byte_size: null, export_paths: {}, export_items: [], created_at: date,
+    updated_at: date, created_by_user: { id: 1, name: 'SSR' },
+    updated_by_user: { id: 1, name: 'SSR' } })
+
+const responseFor = url => {
+  const locale = url.searchParams.get ('locale') ?? 'ja'
+  const path = url.pathname
+  if (path === '/locales')
+    return { locales: [{ code: 'ja', name: '日本語' }, { code: 'ain-Kana', name: 'アイヌ' }] }
+  if (path === '/users/settings') return { theme: 'system', wiki_editor_mode: 'split' }
+  if (path === '/users/theme_slots') return []
+  if (path === '/counts/posts' || path === '/counts/tags') {
+    const resource = path.endsWith ('posts') ? 'posts' : 'tags'
+    return { count: 1, page: 1, limit: 20, group_count: 1,
+      groups: [{ key: url.searchParams.get ('axis') === 'user' ? 1 : '2024-01',
+        name: null, count: 1 }],
+      versions: resource === 'posts'
+      ? [{ post_id: 1, version_no: 1, title: { current: `SSR count ${locale}` } }]
+      : [{ tag_id: 1, version_no: 1, name: { current: `SSR count ${locale}` } }] }
+  }
+  if (path === '/posts') return { posts: [post (locale)], count: 1 }
+  if (path === '/gekanator/posts') return { posts: [post (locale)] }
+  if (path === '/gekanator/questions') return { questions: [] }
+  if (path === '/posts/1') return post (locale)
+  if (path === '/posts/2')
+    return { ...post (locale), id: 2,
+      url: 'https://www.youtube.com/watch?v=dQw4w9WgXcQ' }
+  if (path === '/tags') return { tags: [tag (locale)], count: 1 }
+  if (path === '/tags/1' || path.startsWith ('/tags/name/')) return tag (locale)
+  if (path === '/tags/1/deerjikists') return { tag: tag (locale), deerjikists: [] }
+  if (path === '/tags/with-depth') return []
+  if (path === '/tags/nico' || path === '/nico/tags') return { tags: [], count: 0 }
+  if (path.endsWith ('/versions')) return { versions: [], count: 0 }
+  if (path === '/wiki') return [wiki (locale)]
+  if (path === '/wiki/changes') return []
+  if (path.includes ('autolink')) return []
+  if (path === '/wiki/1/diff') return { title: 'SSR wiki diff', diff: [] }
+  if (path.startsWith ('/wiki/')) return wiki (locale)
+  if (path === '/materials') return { materials: [material (locale)], count: 1 }
+  if (path === '/materials/1') return material (locale)
+  if (path.includes ('suppressions')) return { suppressions: [] }
+  if (path === '/theatres/1') return { id: 1, name: 'SSR theatre', created_at: date }
+  if (path === '/theatres/1/programmes') return []
+  if (path === '/theatres/1/comments') return []
+  if (path === '/theatres/1/post_selection_weights')
+    return { tag_penalties: [], lightest_posts: [], heaviest_posts: [] }
+  if (path === '/theatres/1/watching')
+    return { host_flg: false, post_id: null, post_started_at: null, post_elapsed_ms: null,
+      watching_users: [], skip_vote: {
+        votes_count: 0, required_count: 1, watching_users_count: 0, voted: false } }
+  return null
+}
+
+// Give startup failures a bounded, visible error instead of waiting indefinitely.
+const withTimeout = async (label, promise, milliseconds) => {
+  let timer
+  try {
+    return await Promise.race ([promise, new Promise ((_, reject) => {
+      timer = setTimeout (() => reject (new Error (
+        `[SSR TEST] ${label} timed out after ${milliseconds}ms`)), milliseconds)
+    })])
+  } finally {
+    clearTimeout (timer)
+  }
+}
+
+before (async () => {
+  console.error('[SSR TEST] setup started')
+
+  api = createServer (async (request, response) => {
+    requests.push ({ method: request.method, url: request.url,
+      cookie: request.headers.cookie, csrf: request.headers['x-csrf-token'],
+      transferCode: request.headers['x-transfer-code'] })
+    const url = new URL (request.url, 'http://localhost')
+    response.setHeader ('Content-Type', 'application/json')
+    response.setHeader ('Cache-Control', 'private, no-store')
+    if (failAPI) {
+      response.writeHead (503).end ()
+      return
+    }
+    if (url.pathname.startsWith ('/users')) {
+      const value = sessionValue (request)
+      const session = sessions.get (value)
+      const user = users.get (session?.code)
+      if (request.method === 'GET') {
+        if (url.pathname === '/users/csrf') {
+          const id = session != null ? value : issueSession (response)
+          response.end (JSON.stringify ({ token: sessions.get (id).token }))
+          return
+        }
+        if (user == null) {
+          response.writeHead (401).end ()
+          return
+        }
+        refreshCookie (response, value)
+        const data = url.pathname === '/users/session' ? user
+          : (url.pathname === '/users/me' ? { ...user, inheritance_code: session.code }
+            : responseFor (url))
+        response.writeHead (data == null ? 404 : 200)
+        response.end (JSON.stringify (data))
+        return
+      }
+      if (![origin, httpOrigin].includes (request.headers.origin)
+          || session == null || request.headers['x-csrf-token'] !== session.token) {
+        response.writeHead (403, { 'X-CSRF-Invalid': '1' }).end ()
+        return
+      }
+      let body = ''
+      for await (const chunk of request) body += chunk
+      const params = JSON.parse (body || '{}')
+      if (request.method === 'POST' && url.pathname === '/users/verify') {
+        const code = params.restore && user != null ? session.code : params.code
+        const verified = users.get (code)
+        if (verified == null) {
+          response.end (JSON.stringify ({ valid: false }))
+          return
+        }
+        sessions.delete (value)
+        issueSession (response, code)
+        response.end (JSON.stringify ({ valid: true,
+          user: { ...verified, inheritance_code: code } }))
+        return
+      }
+      if (request.method === 'DELETE' && url.pathname === '/users/session') {
+        sessions.delete (value)
+        response.writeHead (204, { 'Set-Cookie':
+          `${cookieName}=; Path=/; Max-Age=0; HttpOnly; Secure; SameSite=Lax` }).end ()
+        return
+      }
+      if (request.method === 'POST' && url.pathname === '/users/code/renew' && user != null) {
+        const code = `rotated-recovery-${sessionSequence}`
+        users.delete (session.code)
+        users.set (code, user)
+        sessions.delete (value)
+        issueSession (response, code)
+        response.end (JSON.stringify ({ code }))
+        return
+      }
+      response.writeHead (404).end ()
+      return
+    }
+    const data = responseFor (url)
+    response.writeHead (data == null ? 404 : 200)
+    response.end (JSON.stringify (data))
+  })
+  console.error ('[SSR TEST] API created')
+  await withTimeout ('mock API listen', new Promise ((resolve, reject) => {
+    api.once ('error', reject)
+    api.listen (0, '127.0.0.1', () => {
+      api.off ('error', reject)
+      resolve ()
+    })
+  }), 15_000)
+  apiURL = `http://127.0.0.1:${api.address ().port}`
+  console.error ('[SSR TEST] API ready:', apiURL)
+
+  node = spawn (process.execPath, ['server.mjs'], { env: {
+    ...process.env, NODE_ENV: 'production', PORT: '0', HOST: '127.0.0.1',
+    PUBLIC_ORIGIN: origin, SSR_API_BASE_URL: apiURL },
+    stdio: ['ignore', 'pipe', 'pipe'] })
+  console.error ('[SSR TEST] SSR process spawned:', node.pid ?? '(no PID)')
+
+  let childOutput = ''
+  let childError = ''
+  node.stderr.on ('data', data => {
+    const text = data.toString ()
+    childError = (childError + text).slice (-8_192)
+    process.stderr.write (`[SSR CHILD] ${text}`)
+  })
+  httpOrigin = await withTimeout ('SSR server readiness', new Promise ((resolve, reject) => {
+    const onData = data => {
+      childOutput = (childOutput + data.toString()).slice(-8192)
+
+      // ANSI カラーコードを取り除いてから解析する
+      const output = childOutput.replace(/\x1b\[[0-9;]*m/g, '')
+
+      const match = output.match(/\[SSR\]\s+listening on\s+(\d+)/)
+      if (!match) return
+
+      console.error('[SSR TEST] detected SSR port:', match[1])
+      resolve(`http://127.0.0.1:${match[1]}`)
+    }
+    node.stdout.on ('data', onData)
+    node.once ('error', reject)
+    node.once ('exit', (code, signal) => reject (new Error (
+      `SSR process exited before readiness (code=${code}, signal=${signal})` +
+      `\nstdout: ${childOutput}\nstderr: ${childError}`)))
+  }), 30_000).catch (error => {
+    throw new Error (`${error.message}\nSSR stdout: ${childOutput}\nSSR stderr: ${childError}`,
+      { cause: error })
+  })
+  console.error ('[SSR TEST] SSR server ready:', httpOrigin)
+
+  console.error ('[SSR TEST] starting Vite')
+  vite = await withTimeout ('Vite initialization',
+    createViteServer ({ server: { middlewareMode: true }, appType: 'custom' }), 90_000)
+  console.error ('[SSR TEST] Vite ready')
+
+  const { pageRoutes } = await withTimeout ('App.tsx module loading',
+    vite.ssrLoadModule ('/src/App.tsx'), 90_000)
+  console.error ('[SSR TEST] App loaded')
+  const flatten = (entries, parent = '') => entries.flatMap (route => {
+    const path = [parent, route.path].filter (Boolean).join ('/')
+    return route.children ? flatten (route.children, path) : [{ ...route, path }]
+  })
+  routes = flatten (pageRoutes (null, () => {}))
+  console.error (`[SSR TEST] setup complete (${routes.length} routes)`)
+})
+
+// Report the route on which server-side rendering stalls or fails.
+const renderPage = async (url, ...args) => {
+  console.error (`[SSR TEST] rendering: ${url}`)
+  const result = await withTimeout (`render ${url}`, render (url, ...args), 60_000)
+  console.error (`[SSR TEST] rendered: ${url}`)
+  return result
+}
+
+const authenticatedCookie = async (code = recoveryCode) => {
+  const csrf = await fetch (`${httpOrigin}/api/users/csrf`)
+  assert.equal (csrf.status, 200)
+  const { token } = await csrf.json ()
+  const verified = await fetch (`${httpOrigin}/api/users/verify`, {
+    method: 'POST', headers: { Origin: origin, 'Content-Type': 'application/json',
+      Cookie: csrf.headers.get ('set-cookie').split (';')[0], 'X-CSRF-Token': token },
+    body: JSON.stringify ({ code, restore: true }) })
+  assert.equal (verified.status, 200)
+  assert.equal ((await verified.json ()).valid, true)
+  const cookie = verified.headers.get ('set-cookie')
+  assert.match (cookie, /HttpOnly; Secure; SameSite=Lax/)
+  assert.doesNotMatch (cookie, new RegExp (code))
+  return cookie.split (';')[0]
+}
+
+after (async () => {
+  console.error ('[SSR TEST] teardown started')
+  const errors = []
+  if (vite) {
+    try {
+      await withTimeout ('Vite shutdown', vite.close (), 30_000)
+    } catch (error) {
+      errors.push (error)
+    }
+  }
+  if (node && node.exitCode == null && node.signalCode == null) node.kill ()
+  if (api?.listening) {
+    api.closeAllConnections ()
+    try {
+      await withTimeout ('mock API shutdown', new Promise ((resolve, reject) => {
+        api.close (error => error ? reject (error) : resolve ())
+      }), 10_000)
+    } catch (error) {
+      errors.push (error)
+    }
+  }
+  console.error ('[SSR TEST] teardown finished')
+  if (errors.length) throw new AggregateError (errors, 'SSR teardown failed')
+})
+
+test ('counts SSR renders history data and retains URL query state', async () => {
+  for (const locale of ['ja', 'ain-Kana']) {
+    for (const resource of ['posts', 'tags']) {
+      const column = resource === 'posts' ? 'title' : 'name'
+      const query = `mode=details&columns=${column}&user_id=4`
+      const result = await renderPage (`/${locale}/counts/${resource}?${query}`, origin, apiURL)
+      assert.equal (result.status, 200)
+      assert.match (result.html, new RegExp (`SSR count ${locale}`))
+      assert.match (result.html, new RegExp (`/${locale}/${resource}/1`))
+      assert.doesNotMatch (result.html, /counts:|columns\.changedAt|fields\.actor/)
+      assert.match (result.html, /aria-expanded="false"/)
+      if (locale === 'ain-Kana')
+        assert.match (result.html, /lang="ja"[^>]*>集計実行/)
+      assert.ok (requests.some (request => request.url.includes (`/counts/${resource}`)
+        && request.url.includes ('user_id=4') && request.url.includes (`locale=${locale}`)))
+    }
+  }
+})
+
+test ('every canonical screen route returns page HTML without JavaScript', async t => {
+  const cookie = await authenticatedCookie ()
+  for (const route of routes) {
+    for (const locale of ['ja', 'ain-Kana']) {
+      const path = route.path.replace (':identifier', 'home').replace (/:id|:title/g, '1')
+        .replace ('*', 'unknown-screen')
+      const url = `/${locale}/${path}?from=2026-09-15&to=2026-09-15`
+      await t.test (`${locale} ${route.path}`, async () => {
+        const result = await renderPage (url, origin, apiURL, { cookie })
+        assert.ok (result != null)
+        if (route.handle?.redirectTo) {
+          assert.equal (result.status, 308)
+          return
+        }
+        assert.ok (result.html?.length > 300, 'actual page HTML is required')
+        assert.equal (result.status, route.path === '*' ? 404 : 200)
+        assert.match (result.head, /<title/)
+        assert.match (result.head, /rel="canonical"/)
+        assert.equal (result.locale, locale)
+        assert.doesNotMatch (result.html + result.bootstrap, /test-recovery-secret|opaque-rails/)
+        if (route.path === 'wiki/:id/edit') assert.match (result.html, /<textarea/)
+        if (route.path === 'users/settings') assert.match (result.html, /SSR account/)
+        if (route.path === 'posts')
+          assert.match (result.html, new RegExp (`SSR post ${locale}`))
+        if (route.path === 'posts/:id')
+          assert.match (result.head, new RegExp (`SSR post ${locale}`))
+        if (route.path === 'theatres/:id')
+          assert.match (result.html.replace (/<[^>]*>/g, ''), /SSR[ 　]theatre/)
+        if (route.path === 'wiki' || route.path === 'wiki/:title')
+          assert.match (result.html, new RegExp (`SSR wiki body ${locale}|SSR`))
+        assert.doesNotMatch (result.html, /Switched to client rendering|template id="B:/)
+      })
+    }
+  }
+})
+
+test ('YouTube posts return HTTP 200 with the embed rendered by SSR', async t => {
+  for (const locale of ['ja', 'ain-Kana']) {
+    await t.test (locale, async () => {
+      const response = await fetch (`${httpOrigin}/${locale}/posts/2`)
+      assert.equal (response.status, 200)
+      const html = await response.text ()
+      assert.match (html, new RegExp (`<html lang="${locale}"`))
+      assert.match (html, new RegExp (`SSR post ${locale}`))
+      assert.match (html, /https:\/\/www\.youtube\.com\/watch\?v=dQw4w9WgXcQ/)
+      // react-youtube renders its player container before mounting the iframe.
+      assert.match (html, /<div class=""><div id="" class=""><\/div><\/div>/)
+      assert.doesNotMatch (html, /Switched to client rendering|template id="B:/)
+    })
+  }
+})
+
+test ('parallel localized requests keep list data isolated', async () => {
+  const start = requests.length
+  const pages = await Promise.all (['ja', 'ain-Kana', 'ja', 'ain-Kana'].map (locale =>
+    renderPage (`/${locale}/posts?limit=50&page=2`, origin, apiURL)))
+  for (const [index, page] of pages.entries ()) {
+    const locale = index % 2 === 0 ? 'ja' : 'ain-Kana'
+    assert.match (page.html, new RegExp (`SSR post ${locale}`))
+    assert.equal (page.status, 200)
+    const state = JSON.parse (page.bootstrap)
+    assert.equal (state.locale, locale)
+  }
+  assert.ok (requests.some (request => request.url.includes ('page=2')))
+  assert.ok (requests.slice (start).every (request => request.method === 'GET'))
+})
+
+test ('unknown resources and legacy URLs have correct status', async () => {
+  assert.equal ((await renderPage ('/ja/unknown', origin, apiURL)).status, 404)
+  assert.equal ((await renderPage ('/ja/help/unknown', origin, apiURL)).status, 404)
+  assert.equal ((await renderPage ('/ja/posts/999', origin, apiURL)).status, 404)
+  const redirect = await renderPage ('/help/home?edition=2026-09-15', origin, apiURL)
+  assert.equal (redirect.status, 308)
+  assert.equal (redirect.location, '/ja/help/home?edition=2026-09-15')
+})
+
+test ('HTTP forwards Rails cookies, CSRF, expiration and upstream errors', async () => {
+  const cookie = await authenticatedCookie ()
+  const settings = await fetch (`${httpOrigin}/ja/users/settings`, { headers: { Cookie: cookie } })
+  assert.equal (settings.status, 200)
+  const html = await settings.text ()
+  assert.match (html, /SSR account/)
+  assert.doesNotMatch (html, /test-recovery-secret|opaque-rails-session/)
+  assert.match (settings.headers.get ('cache-control'), /private, no-store/)
+  assert.match (settings.headers.get ('set-cookie'), /Max-Age=630720000/)
+  assert.ok (requests.some (request => request.url === '/users/session'
+    && request.cookie === cookie))
+  assert.ok (requests.every (request => request.transferCode == null))
+  assert.equal ((await fetch (`${httpOrigin}/ja/users/settings`)).status, 401)
+  const invalid = cookie.replace ('=', '=invalid')
+  assert.equal ((await fetch (`${httpOrigin}/ja/users/settings`, {
+    headers: { Cookie: invalid } })).status, 401)
+  const publicPage = await fetch (`${httpOrigin}/ain-Kana/posts`)
+  assert.equal (publicPage.status, 200)
+  assert.match (await publicPage.text (), /SSR post ain-Kana/)
+  assert.equal ((await fetch (`${httpOrigin}/_ssr/session`, { method: 'POST' })).status, 405)
+
+  const csrf = await fetch (`${httpOrigin}/api/users/csrf`, { headers: { Cookie: cookie } })
+  const { token } = await csrf.json ()
+  const write = (csrfToken, requestOrigin = origin) => fetch (
+    `${httpOrigin}/api/users/verify`, { method: 'POST',
+      headers: { Cookie: cookie, Origin: requestOrigin, 'Content-Type': 'application/json',
+        'X-CSRF-Token': csrfToken }, body: JSON.stringify ({ code: recoveryCode }) })
+  assert.equal ((await write ('invalid')).status, 403)
+  assert.equal ((await write (token, 'https://other.invalid')).status, 403)
+  assert.equal ((await fetch (`${httpOrigin}/ja/users/settings`, {
+    headers: { Cookie: cookie } })).status, 200)
+  const renewed = await write (token)
+  assert.equal (renewed.status, 200)
+  const renewedCookie = renewed.headers.get ('set-cookie').split (';')[0]
+  assert.notEqual (renewedCookie, cookie)
+  assert.equal ((await fetch (`${httpOrigin}/ja/users/settings`, {
+    headers: { Cookie: cookie } })).status, 401)
+  const renewedCSRF = await fetch (`${httpOrigin}/api/users/csrf`, {
+    headers: { Cookie: renewedCookie } })
+  const newToken = (await renewedCSRF.json ()).token
+  const logout = await fetch (`${httpOrigin}/api/users/session`, { method: 'DELETE',
+    headers: { Cookie: renewedCookie, Origin: origin, 'X-CSRF-Token': newToken } })
+  assert.equal (logout.status, 204)
+  assert.match (logout.headers.get ('set-cookie'), /Max-Age=0/)
+  assert.equal ((await fetch (`${httpOrigin}/ja/users/settings`, {
+    headers: { Cookie: renewedCookie } })).status, 401)
+  failAPI = true
+  try {
+    assert.equal ((await fetch (`${httpOrigin}/ja/posts`)).status, 503)
+  } finally {
+    failAPI = false
+  }
+})
+
+test ('parallel user and Locale requests never share authentication or query state', async () => {
+  const cookies = await Promise.all ([authenticatedCookie (),
+    authenticatedCookie ('second-recovery-secret')])
+  const inputs = cookies.flatMap ((cookie, user) => ['ja', 'ain-Kana'].map (locale => ({
+    cookie, locale, name: user === 0 ? 'SSR account' : 'Second account',
+    other: user === 0 ? 'Second account' : 'SSR account' })))
+  const pages = await Promise.all (inputs.map (async input => {
+    const response = await fetch (`${httpOrigin}/${input.locale}/users/settings`, {
+      headers: { Cookie: input.cookie } })
+    assert.equal (response.status, 200)
+    return response.text ()
+  }))
+  for (const [index, html] of pages.entries ()) {
+    const input = inputs[index]
+    assert.match (html, new RegExp (input.name))
+    assert.doesNotMatch (html, new RegExp (input.other))
+    assert.match (html, new RegExp (`<html lang="${input.locale}"`))
+    assert.doesNotMatch (html, /recovery-secret|opaque-rails-session|csrf-/)
+  }
+})
+
+test ('renewed recovery codes invalidate old sessions and forward the new Rails cookie',
+  async () => {
+    const cookie = await authenticatedCookie ('second-recovery-secret')
+    const csrf = await fetch (`${httpOrigin}/api/users/csrf`, { headers: { Cookie: cookie } })
+    const { token } = await csrf.json ()
+    const renewed = await fetch (`${httpOrigin}/api/users/code/renew`, {
+      method: 'POST', headers: { Cookie: cookie, Origin: origin, 'X-CSRF-Token': token } })
+    assert.equal (renewed.status, 200)
+    const newCookie = renewed.headers.get ('set-cookie').split (';')[0]
+    assert.notEqual (newCookie, cookie)
+    assert.equal ((await fetch (`${httpOrigin}/ja/users/settings`, {
+      headers: { Cookie: cookie } })).status, 401)
+    assert.equal ((await fetch (`${httpOrigin}/ain-Kana/users/settings`, {
+      headers: { Cookie: newCookie } })).status, 200)
+  })
+
+test ('hydrate every route with stored browser preferences', {
+  skip: !process.env.SSR_CHROME_PATH, timeout: 180_000,
+}, async t => {
+  const { default: WebSocket } = await import ('ws')
+  const chrome = spawn (process.env.SSR_CHROME_PATH, [
+    '--headless', '--no-sandbox', '--disable-gpu', '--disable-dev-shm-usage',
+    '--remote-debugging-port=0', `--user-data-dir=/tmp/btrc-ssr-browser-${process.pid}`],
+    { stdio: ['ignore', 'ignore', 'pipe'] })
+  let ws
+  try {
+    const endpoint = await new Promise ((resolve, reject) => {
+      let output = ''
+      chrome.stderr.on ('data', data => {
+        output += data
+        const match = output.match (/DevTools listening on (ws:\/\/\S+)/)
+        if (match) resolve (match[1])
+      })
+      chrome.on ('error', reject)
+    })
+    ws = new WebSocket (endpoint)
+    await new Promise (resolve => ws.on ('open', resolve))
+    const pending = new Map ()
+    let sequence = 0, errors = [], probeActive = false, delayedChunks = 0, documents = 0
+    const send = (method, params = {}, sessionId) => new Promise ((resolve, reject) => {
+      const id = ++sequence
+      pending.set (id, { resolve, reject })
+      ws.send (JSON.stringify ({ id, method, params, sessionId }))
+    })
+    ws.on ('message', raw => {
+      const message = JSON.parse (raw)
+      if (message.id) {
+        const entry = pending.get (message.id)
+        pending.delete (message.id)
+        if (message.error) entry?.reject (message.error)
+        else entry?.resolve (message.result)
+      } else if (message.method === 'Fetch.requestPaused') {
+        const { requestId, request } = message.params
+        const url = new URL (request.url)
+        if (url.origin === httpOrigin) {
+          const delayed = probeActive
+            && /\/(MaterialBasePage|MaterialListPage|TagListPage)-[^/]+\.js$/.test (url.pathname)
+          if (delayed) ++delayedChunks
+          setTimeout (() => {
+            void send ('Fetch.continueRequest', { requestId }, message.sessionId)
+          }, delayed ? 600 : 0)
+          return
+        }
+        const data = responseFor (url)
+        void send ('Fetch.fulfillRequest', { requestId,
+          responseCode: request.method === 'OPTIONS' ? 204 : 200,
+          responseHeaders: [{ name: 'Content-Type', value: 'application/json' },
+            { name: 'Access-Control-Allow-Origin', value: httpOrigin },
+            { name: 'Access-Control-Allow-Headers', value: '*' },
+            { name: 'Access-Control-Allow-Methods', value: '*' }],
+          body: Buffer.from (JSON.stringify (data ?? {})).toString ('base64') }, message.sessionId)
+      } else if (message.method === 'Runtime.exceptionThrown') {
+        errors.push (message.params.exceptionDetails.exception?.description
+          ?? message.params.exceptionDetails.text)
+      } else if (message.method === 'Runtime.consoleAPICalled'
+        && message.params.type === 'error') {
+        errors.push (message.params.args.map (arg => arg.value ?? arg.description).join (' '))
+      } else if (message.method === 'Network.requestWillBeSent'
+          && message.params.type === 'Document') {
+        ++documents
+      }
+    })
+    const { targetId } = await send ('Target.createTarget', { url: 'about:blank' })
+    const { sessionId } = await send ('Target.attachToTarget', { targetId, flatten: true })
+    await send ('Runtime.enable', {}, sessionId)
+    await send ('Page.enable', {}, sessionId)
+    await send ('Network.enable', {}, sessionId)
+    await send ('Network.setCacheDisabled', { cacheDisabled: true }, sessionId)
+    await send ('Fetch.enable', { patterns: [{ urlPattern: '*' }] }, sessionId)
+    const cookie = await authenticatedCookie ()
+    await send ('Network.setExtraHTTPHeaders', { headers: {
+      Cookie: cookie } }, sessionId)
+    await send ('Page.addScriptToEvaluateOnNewDocument', { source: `
+      localStorage.setItem('user_code','test-recovery-secret');
+      localStorage.setItem('btrc_hub.client_settings',JSON.stringify({
+        lists:{postList:{limit:50},tagList:{limit:50},postSearch:{limit:50}},
+        behavior:{animation:new URLSearchParams(location.search).get('animation')??'off'},
+        theatre:{layoutMode:'tagsBottom',tagFlow:'horizontal'}
+      }));
+      new MutationObserver(()=>{
+        const child=document.getElementById('root')?.firstElementChild;
+        if(child&&!window.__initialSSRNode)window.__initialSSRNode=child;
+      }).observe(document,{childList:true,subtree:true});
+      if(new URLSearchParams(location.search).has('layoutProbe')){
+        window.__layoutProbe={samples:[],mainLost:false,earlyAnimation:false};
+        let originalMain=null;
+        const sample=()=>{
+          const main=document.querySelector('main');
+          const layout=document.querySelector('.top-nav-layout');
+          const controls=document.querySelector('.top-nav-mobile-controls');
+          if(main&&layout&&controls){
+            originalMain??=main;
+            if(!originalMain.isConnected)window.__layoutProbe.mainLost=true;
+            const ready=layout.dataset.layoutReady==='true';
+            const state={mobile:getComputedStyle(controls).display!=='none',
+              measured:layout.hasAttribute('data-desktop'),ready};
+            const previous=window.__layoutProbe.samples.at(-1);
+            if(JSON.stringify(previous)!==JSON.stringify(state))
+              window.__layoutProbe.samples.push(state);
+            if(!ready&&layout.getAnimations({subtree:true})
+                .some(animation=>animation.playState==='running'))
+              window.__layoutProbe.earlyAnimation=true;
+          }else if(originalMain&&!originalMain.isConnected){
+            window.__layoutProbe.mainLost=true;
+          }
+          requestAnimationFrame(sample);
+        };
+        requestAnimationFrame(sample);
+      }` }, sessionId)
+    const evaluate = async expression => (await send ('Runtime.evaluate', {
+      expression, returnByValue: true }, sessionId)).result.value
+    for (const route of routes.filter (entry => !entry.handle?.redirectTo
+      && (process.env.SSR_COUNTS_ONLY !== '1' || entry.path.startsWith ('counts')))) {
+      for (const locale of ['ja', 'ain-Kana']) {
+        await t.test (`hydrate ${locale} ${route.path}`, async () => {
+          const path = route.path.replace (':identifier', 'home').replace (/:id|:title/g, '1')
+            .replace ('*', 'unknown-screen')
+          errors = []
+          await send ('Page.navigate', {
+            url: `${httpOrigin}/${locale}/${path}?from=2026-09-15&to=2026-09-15` }, sessionId)
+          let hydrated = false
+          for (let attempt = 0; attempt < 100; ++attempt) {
+            await new Promise (resolve => setTimeout (resolve, 75))
+            try {
+              hydrated = await evaluate (`Object.keys(document.getElementById('root')??{})
+                .some(key=>key.startsWith('__reactContainer'))`)
+            } catch {}
+            if (hydrated) break
+          }
+          assert.ok (hydrated, 'hydrateRoot must run')
+          await new Promise (resolve => setTimeout (resolve, 150))
+          assert.deepEqual (errors, [])
+          assert.ok (await evaluate (`document.getElementById('root').firstElementChild
+            ===window.__initialSSRNode`), 'server DOM must be preserved')
+          assert.equal (await evaluate ('document.documentElement.lang'), locale)
+        })
+      }
+    }
+    for (const width of [375, 1240]) {
+      await send ('Emulation.setDeviceMetricsOverride', {
+        width, height: 900, deviceScaleFactor: 1, mobile: width < 768 }, sessionId)
+      for (const resource of ['posts', 'tags']) {
+        await t.test (`counts layout ${width} ${resource}`, async () => {
+          await send ('Page.navigate', {
+            url: `${httpOrigin}/ja/counts/${resource}` }, sessionId)
+          let ready = false
+          for (let attempt = 0; attempt < 100; ++attempt) {
+            await new Promise (resolve => setTimeout (resolve, 75))
+            try {
+              ready = await evaluate (`document.querySelector('tbody tr')!=null`)
+            } catch {}
+            if (ready) break
+          }
+          assert.ok (ready, 'history query results must render')
+          const layout = await evaluate (`(()=>{
+            const nav=document.getElementById('counts-targets');
+            const main=document.querySelector('main').getBoundingClientRect();
+            return {visible:nav.getClientRects().length>0,
+              right:nav.getBoundingClientRect().right,left:main.left,width:main.width};
+          })()`)
+          assert.ok (width >= 768 ? layout.visible && layout.right <= layout.left
+            : !layout.visible && layout.width >= width - 16,
+            'the sidebar sits beside the table on desktop and collapses on mobile')
+          const toggle = `Array.from(document.querySelectorAll('button'))
+            .find(button=>button.textContent.includes('集計条件'))`
+          assert.equal (await evaluate (`(${toggle}).getAttribute('aria-expanded')`), 'false')
+          await evaluate (`(${toggle}).click()`)
+          const positions = await evaluate (`(()=>{
+            const output=document.querySelector('[data-counts-output]').getBoundingClientRect();
+            const filters=document.querySelector('[data-counts-filters]').getBoundingClientRect();
+            return {left:output.left,right:filters.left,top:output.top,bottom:filters.top};
+          })()`)
+          assert.ok (width >= 768 ? positions.left < positions.right
+            : positions.top < positions.bottom, 'output precedes filters in the layout')
+          assert.ok (await evaluate ('document.documentElement.scrollWidth<=innerWidth'))
+          if (resource === 'posts' && process.env.SSR_COUNTS_ONLY === '1') {
+            const { writeFile } = await import ('node:fs/promises')
+            const shot = await send ('Page.captureScreenshot', { format: 'png' }, sessionId)
+            await writeFile (`/tmp/counts-${width}-conditions.png`,
+              Buffer.from (shot.data, 'base64'))
+          }
+          await evaluate (`(${toggle}).click()`)
+          for (const dark of [false, true]) {
+            await evaluate (`document.documentElement.classList.toggle('dark',${dark})`)
+            assert.ok (await evaluate ('document.documentElement.scrollWidth<=innerWidth'),
+              'counts controls must fit the viewport in both themes')
+            if (resource === 'posts' && process.env.SSR_COUNTS_ONLY === '1') {
+              const { writeFile } = await import ('node:fs/promises')
+              const shot = await send ('Page.captureScreenshot', { format: 'png' }, sessionId)
+              await writeFile (`/tmp/counts-${width}-${dark ? 'dark' : 'light'}.png`,
+                Buffer.from (shot.data, 'base64'))
+            }
+          }
+        })
+      }
+    }
+    if (process.env.SSR_COUNTS_ONLY === '1') return
+    probeActive = true
+    for (const width of [375, 1240]) {
+      await send ('Emulation.setDeviceMetricsOverride', {
+        width, height: 900, deviceScaleFactor: 1, mobile: width < 768 }, sessionId)
+      for (const animation of ['off', 'reduced', 'normal']) {
+        for (const locale of ['ja', 'ain-Kana']) {
+          for (const page of ['materials', 'tags']) {
+            await t.test (`stable first paint ${width} ${animation} ${locale} ${page}`,
+              async () => {
+                errors = []
+                documents = 0
+                delayedChunks = 0
+                await send ('Page.navigate', { url:
+                  `${httpOrigin}/${locale}/${page}?layoutProbe=1&animation=${animation}` }, sessionId)
+                let ready = false
+                for (let attempt = 0; attempt < 100; ++attempt) {
+                  await new Promise (resolve => setTimeout (resolve, 75))
+                  try {
+                    ready = await evaluate (`document.querySelector('.top-nav-layout')
+                      ?.dataset.layoutReady==='true'
+                      &&Object.keys(document.getElementById('root')??{})
+                      .some(key=>key.startsWith('__reactContainer'))`)
+                  } catch {}
+                  if (ready) break
+                }
+                assert.ok (ready, 'hydration and the first layout measurement must finish')
+                await new Promise (resolve => setTimeout (resolve, 150))
+                const probe = await evaluate ('window.__layoutProbe')
+                assert.ok (delayedChunks >= (page === 'materials' ? 2 : 1))
+                assert.equal (documents, 1)
+                assert.deepEqual (errors, [])
+                assert.equal (probe.mainLost, false, 'SSR page content must stay attached')
+                assert.equal (probe.earlyAnimation, false, 'first layout must not animate')
+                const initial = probe.samples.find (sample => !sample.measured)
+                assert.ok (initial, 'observe the CSS layout before hydration')
+                assert.equal (initial.mobile, width < 768)
+                const final = probe.samples.at (-1)
+                if (!final.mobile)
+                  assert.ok (probe.samples.every (sample => !sample.mobile),
+                    'a desktop page must not initially show the mobile controls')
+                assert.ok (await evaluate (`document.documentElement.scrollWidth<=innerWidth`),
+                  'the measured layout must fit the viewport')
+              })
+          }
+        }
+      }
+    }
+  } finally {
+    ws?.close ()
+    chrome.kill ()
+  }
+})

frontend/src/App.tsx

@@ -1,18 +1,31 @@
+import { useQuery, useQueryClient } from '@tanstack/react-query'
 import { AnimatePresence, LayoutGroup, MotionConfig, motion } from 'framer-motion'
-import { Fragment, useEffect, useMemo, useState } from 'react'
+import { createElement, Suspense, lazy, useEffect,
+	 useLayoutEffect, useMemo, useState } from 'react'
+import { useTranslation } from 'react-i18next'
 import { createBrowserRouter,
+	 matchRoutes,
 	 Navigate,
-	 Route,
 	 RouterProvider,
-	 Routes,
-	 useLocation } from 'react-router-dom'
+	 useLocation,
+	 useParams,
+	 useRoutes } from 'react-router-dom'
 
 import DevModeWatermark from '@/components/DevModeWatermark'
 import RouteBlockerOverlay from '@/components/RouteBlockerOverlay'
 import TopNav from '@/components/TopNav'
 import DialogueProvider from '@/components/dialogues/DialogueProvider'
+import PageHead from '@/components/common/PageHead'
 import { Toaster } from '@/components/ui/toaster'
-import { apiPost, isApiError } from '@/lib/api'
+import { isApiError } from '@/lib/api'
+import { initialiseUserSession } from '@/lib/users'
+import { prepareHelpPage } from '@/lib/help'
+import { fetchLocales, isLocaleCode, legacyLocalePath,
+	 switchLocalePath, unlocalisedPath } from '@/lib/locales'
+import { localesKeys, sessionKeys } from '@/lib/queryKeys'
+import { switchPostFilterLocale } from '@/lib/posts'
+import { switchWikiLocale } from '@/lib/wiki'
+import { useLocale } from '@/lib/useLocale'
 import { applyClientAnimationMode,
 	 applyClientAppearance,
 	 fetchUserThemeSlots,
@@ -25,98 +38,204 @@ import { applyClientAnimationMode,
 import { useClientBehaviourSettings } from '@/lib/useClientBehaviourSettings'
 import { UnsavedChangesGuardProvider } from '@/lib/useUnsavedChangesGuard'
 import { KeyboardShortcutsProvider } from '@/lib/useKeyboardShortcuts'
-import DeerjikistDetailPage from '@/pages/deerjikists/DeerjikistDetailPage'
-import MaterialBasePage from '@/pages/materials/MaterialBasePage'
-import MaterialDetailPage from '@/pages/materials/MaterialDetailPage'
-import MaterialHistoryPage from '@/pages/materials/MaterialHistoryPage'
-import MaterialListPage from '@/pages/materials/MaterialListPage'
-import MaterialNewPage from '@/pages/materials/MaterialNewPage'
-import MaterialSyncSuppressionsPage from '@/pages/materials/MaterialSyncSuppressionsPage'
-import MorePage from '@/pages/MorePage'
-import GekanatorPage from '@/pages/GekanatorPage'
-import NicoTagListPage from '@/pages/tags/NicoTagListPage'
 import NotFound from '@/pages/NotFound'
-import TOSPage from '@/pages/TOSPage.mdx'
 import HelpDetailPage from '@/pages/help/HelpDetailPage'
-import HelpChangesPage from '@/pages/help/HelpChangesPage'
-import HelpDiffPage from '@/pages/help/HelpDiffPage'
-import HelpListPage from '@/pages/help/HelpListPage'
-import PostDetailPage from '@/pages/posts/PostDetailPage'
-import PostHistoryPage from '@/pages/posts/PostHistoryPage'
-import PostNewPage from '@/pages/posts/PostNewPage'
-import PostListPage from '@/pages/posts/PostListPage'
-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'
-import WikiDiffPage from '@/pages/wiki/WikiDiffPage'
-import WikiEditPage from '@/pages/wiki/WikiEditPage'
-import WikiHistoryPage from '@/pages/wiki/WikiHistoryPage'
-import WikiNewPage from '@/pages/wiki/WikiNewPage'
-import WikiSearchPage from '@/pages/wiki/WikiSearchPage'
 
-import type { Dispatch, FC, SetStateAction } from 'react'
+import type { ComponentType, Dispatch, FC, ReactNode, SetStateAction } from 'react'
+import type { RouteMatch } from 'react-router-dom'
 
-import type { ClientAnimationMode } from '@/lib/settings'
+import type { AvailableLocale, LocaleCode } from '@/lib/locales'
+import type { PageRoute } from '@/lib/routeLocales'
 import type { User } from '@/types'
 
+const lazyPage = <Props extends object,> (
+    load: () => Promise<{ default: ComponentType<Props> }>,
+) => {
+  let loaded: ComponentType<Props> | null = null
+  let pending: ReturnType<typeof load> | null = null
+  const preload = () => pending ??= load ().then (module => {
+    loaded = module.default
+    return module
+  }).catch (error => {
+    pending = null
+    throw error
+  })
+  const Deferred = lazy (preload)
+  // A preloaded page must render synchronously on the first hydration pass.
+  const Page = (props: Props) => createElement (loaded ?? Deferred, props)
+  return Object.assign (Page, { preload })
+}
 
-const RouteTransitionWrapper = ({ animationMode, user, setUser }: {
-    animationMode:  ClientAnimationMode
-    user:           User | null
-    setUser:        Dispatch<SetStateAction<User | null>> }) => {
+
+const GekanatorPage = lazyPage (() => import ('@/pages/GekanatorPage'))
+const DeerjikistDetailPage = lazyPage (() => import ('@/pages/deerjikists/DeerjikistDetailPage'))
+const MaterialBasePage = lazyPage (() => import ('@/pages/materials/MaterialBasePage'))
+const MaterialDetailPage = lazyPage (() => import ('@/pages/materials/MaterialDetailPage'))
+const MaterialHistoryPage = lazyPage (() => import ('@/pages/materials/MaterialHistoryPage'))
+const MaterialListPage = lazyPage (() => import ('@/pages/materials/MaterialListPage'))
+const MaterialNewPage = lazyPage (() => import ('@/pages/materials/MaterialNewPage'))
+const MaterialSyncSuppressionsPage = lazyPage (
+    () => import ('@/pages/materials/MaterialSyncSuppressionsPage'))
+const CountsPage = lazyPage (() => import ('@/pages/CountsPage'))
+const CountsResourcePage = lazyPage (() => import ('@/pages/CountsResourcePage'))
+const MorePage = lazyPage (() => import ('@/pages/MorePage'))
+const GekanatorUnavailablePage = lazyPage (() => import ('@/pages/GekanatorUnavailablePage'))
+const NicoTagListPage = lazyPage (() => import ('@/pages/tags/NicoTagListPage'))
+const TOSPage = lazyPage (() => import ('@/pages/TOSPage'))
+const HelpChangesPage = lazyPage (() => import ('@/pages/help/HelpChangesPage'))
+const HelpDiffPage = lazyPage (() => import ('@/pages/help/HelpDiffPage'))
+const HelpListPage = lazyPage (() => import ('@/pages/help/HelpListPage'))
+const PostDetailPage = lazyPage (() => import ('@/pages/posts/PostDetailPage'))
+const PostHistoryPage = lazyPage (() => import ('@/pages/posts/PostHistoryPage'))
+const PostNewPage = lazyPage (() => import ('@/pages/posts/PostNewPage'))
+const PostListPage = lazyPage (() => import ('@/pages/posts/PostListPage'))
+const PostSearchPage = lazyPage (() => import ('@/pages/posts/PostSearchPage'))
+const SettingPage = lazyPage (() => import ('@/pages/users/SettingPage'))
+const TagDetailPage = lazyPage (() => import ('@/pages/tags/TagDetailPage'))
+const TagHistoryPage = lazyPage (() => import ('@/pages/tags/TagHistoryPage'))
+const TagListPage = lazyPage (() => import ('@/pages/tags/TagListPage'))
+const TheatreDetailPage = lazyPage (() => import ('@/pages/theatres/TheatreDetailPage'))
+const WikiDetailPage = lazyPage (() => import ('@/pages/wiki/WikiDetailPage'))
+const WikiDiffPage = lazyPage (() => import ('@/pages/wiki/WikiDiffPage'))
+const WikiEditPage = lazyPage (() => import ('@/pages/wiki/WikiEditPage'))
+const WikiHistoryPage = lazyPage (() => import ('@/pages/wiki/WikiHistoryPage'))
+const WikiNewPage = lazyPage (() => import ('@/pages/wiki/WikiNewPage'))
+const WikiSearchPage = lazyPage (() => import ('@/pages/wiki/WikiSearchPage'))
+
+
+const GekanatorRoute = ({ user }: { user: User | null }) => {
+  const locale = useLocale ()
   const location = useLocation ()
+  const pageLocale = resolvePageRoute (location.pathname)?.route.handle?.locale
 
-  const routes = (
-      <Routes location={location}>
-	<Route path="/" element={<Navigate to="/posts" replace/>}/>
-	<Route path="/posts" element={<PostListPage/>}/>
-	<Route path="/posts/new" element={<PostNewPage user={user}/>}/>
-	<Route path="/posts/search" element={<PostSearchPage/>}/>
-	<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/:id/deerjikists" element={<DeerjikistDetailPage/>}/>
-	<Route path="/tags/nico" element={<NicoTagListPage user={user}/>}/>
-	<Route path="/nico/tags" element={<NicoTagListPage user={user}/>}/>
-	<Route path="/tags/changes" element={<TagHistoryPage/>}/>
-	<Route path="/theatres/:id" element={<TheatreDetailPage user={user}/>}/>
-	<Route path="/materials" element={<MaterialBasePage/>}>
-	  <Route index element={<MaterialListPage/>}/>
-	  <Route path="changes" element={<MaterialHistoryPage/>}/>
-	  <Route path="new" element={<MaterialNewPage/>}/>
-	  <Route path="suppressions" element={<MaterialSyncSuppressionsPage/>}/>
-	  <Route path=":id" element ={<MaterialDetailPage/>}/>
-	</Route>
-	<Route path="/wiki" element={<WikiSearchPage/>}/>
-	<Route path="/wiki/:title" element={<WikiDetailPage/>}/>
-	<Route path="/wiki/new" element={<WikiNewPage user={user}/>}/>
-	<Route path="/wiki/:id/edit" element={<WikiEditPage user={user}/>}/>
-	<Route path="/wiki/:id/diff" element={<WikiDiffPage/>}/>
-	<Route path="/wiki/changes" element={<WikiHistoryPage/>}/>
-	<Route path="/help" element={<HelpListPage/>}/>
-	<Route path="/help/changes" element={<HelpChangesPage/>}/>
-	<Route path="/help/:identifier/diff" element={<HelpDiffPage/>}/>
-	<Route path="/help/:identifier" element={<HelpDetailPage/>}/>
-	<Route path="/users/settings" element={<SettingPage user={user} setUser={setUser}/>}/>
-	<Route path="/settings" element={<Navigate to="/users/settings" replace/>}/>
-	<Route path="/tos" element={<TOSPage/>}/>
-	<Route path="/gekanator" element={<GekanatorPage user={user}/>}/>
-	<Route path="/more" element={<MorePage/>}/>
-	<Route path="*" element={<NotFound/>}/>
-      </Routes>)
-
-  if (animationMode === 'off')
-    return routes
+  if (pageLocale != null && pageLocale !== locale)
+    return <GekanatorUnavailablePage/>
 
   return (
-      <AnimatePresence mode="wait">
-	{routes}
+      <Suspense fallback={null}>
+	<GekanatorPage user={user}/>
+      </Suspense>)
+}
+
+
+export const pageRoutes = (
+    user: User | null,
+    setUser: Dispatch<SetStateAction<User | null>>,
+): PageRoute[] => [
+    { path: '', element: <LocaleRedirect to="/posts"/>,
+      handle: { redirectTo: '/posts' } },
+    { path: 'posts', element: <PostListPage/>,
+      handle: { preload: PostListPage.preload, switchLocale: switchPostFilterLocale,
+	sitemap: ['static'] } },
+    { path: 'posts/new', element: <PostNewPage user={user}/>,
+      handle: { preload: PostNewPage.preload, robots: 'noindex' } },
+    { path: 'posts/search', element: <PostSearchPage/>,
+      handle: { preload: PostSearchPage.preload, switchLocale: switchPostFilterLocale } },
+    { path: 'posts/:id', element: <PostDetailRoute user={user}/>,
+      handle: { preload: PostDetailPage.preload, sitemap: ['posts'] } },
+    { path: 'posts/changes', element: <PostHistoryPage/>,
+      handle: { preload: PostHistoryPage.preload } },
+    { path: 'tags', element: <TagListPage/>,
+      handle: { preload: TagListPage.preload, sitemap: ['static'] } },
+    { path: 'tags/:id', element: <TagDetailPage/>,
+      handle: { preload: TagDetailPage.preload, sitemap: ['tags'] } },
+    { path: 'tags/:id/deerjikists', element: <DeerjikistDetailPage/>,
+      handle: { preload: DeerjikistDetailPage.preload, sitemap: ['deerjikists'] } },
+    { path: 'tags/nico', element: <NicoTagListPage user={user}/>,
+      handle: { preload: NicoTagListPage.preload, sitemap: ['static'] } },
+    { path: 'nico/tags', element: <NicoTagListPage user={user}/>,
+      handle: { preload: NicoTagListPage.preload } },
+    { path: 'tags/changes', element: <TagHistoryPage/>,
+      handle: { preload: TagHistoryPage.preload } },
+    { path: 'theatres/:id', element: <TheatreDetailPage user={user}/>,
+      handle: { preload: TheatreDetailPage.preload, sitemap: ['theatres'] } },
+    { path: 'materials', element: <MaterialBasePage/>,
+      handle: { preload: MaterialBasePage.preload }, children: [
+	{ index: true, element: <MaterialListPage/>,
+	  handle: { preload: MaterialListPage.preload, sitemap: ['static'] } },
+	{ path: 'changes', element: <MaterialHistoryPage/>,
+	  handle: { preload: MaterialHistoryPage.preload } },
+	{ path: 'new', element: <MaterialNewPage/>,
+	  handle: { preload: MaterialNewPage.preload, robots: 'noindex' } },
+	{ path: 'suppressions', element: <MaterialSyncSuppressionsPage/>,
+	  handle: { preload: MaterialSyncSuppressionsPage.preload,
+	    robots: 'noindex', authentication: 'user' } },
+	{ path: ':id', element: <MaterialDetailPage/>,
+	  handle: { preload: MaterialDetailPage.preload, sitemap: ['materials'] } }] },
+    { path: 'wiki', element: <WikiSearchPage/>,
+      handle: { preload: WikiSearchPage.preload, sitemap: ['static'] } },
+    { path: 'wiki/:title', element: <WikiDetailPage/>,
+      handle: { preload: WikiDetailPage.preload, switchLocale: switchWikiLocale,
+	sitemap: ['descriptions', 'tag_groups'] } },
+    { path: 'wiki/new', element: <WikiNewPage user={user}/>,
+      handle: { preload: WikiNewPage.preload, robots: 'noindex' } },
+    { path: 'wiki/:id/edit', element: <WikiEditPage user={user}/>,
+      handle: { preload: WikiEditPage.preload, robots: 'noindex',
+	switchLocale: request => switchWikiLocale (request, 'edit') } },
+    { path: 'wiki/:id/diff', element: <WikiDiffPage/>,
+      handle: { preload: WikiDiffPage.preload,
+	switchLocale: request => switchWikiLocale (request, 'diff') } },
+    { path: 'wiki/changes', element: <WikiHistoryPage/>,
+      handle: { preload: WikiHistoryPage.preload,
+	switchLocale: request => switchWikiLocale (request, 'history') } },
+    { path: 'help', element: <HelpListPage/>,
+      handle: { preload: HelpListPage.preload, sitemap: ['static'] } },
+    { path: 'help/changes', element: <HelpChangesPage/>,
+      handle: { preload: HelpChangesPage.preload } },
+    { path: 'help/:identifier/diff', element: <HelpDiffPage/>,
+      handle: { preload: HelpDiffPage.preload } },
+    { id: 'help.detail', path: 'help/:identifier', element: <HelpDetailPage/>,
+      handle: { prepare: prepareHelpPage, sitemap: ['help'] } },
+    { path: 'users/settings', element: <SettingPage user={user} setUser={setUser}/>,
+      handle: { preload: SettingPage.preload, robots: 'noindex', authentication: 'user' } },
+    { path: 'settings', element: <LocaleRedirect to="/users/settings"/>,
+      handle: { redirectTo: '/users/settings' } },
+    { path: 'tos', element: <TOSPage/>,
+      handle: { preload: TOSPage.preload, sitemap: ['static'] } },
+    { id: 'gekanator', path: 'gekanator', element: <GekanatorRoute user={user}/>,
+      handle: { locale: 'ja', sitemap: ['static'], preload: locale => locale === 'ja'
+	  ? GekanatorPage.preload () : GekanatorUnavailablePage.preload () } },
+    { path: 'counts', element: <CountsPage/>,
+      handle: { preload: CountsPage.preload } },
+    { path: 'counts/posts', element: <CountsResourcePage resource="posts"/>,
+      handle: { preload: CountsResourcePage.preload } },
+    { path: 'counts/tags', element: <CountsResourcePage resource="tags"/>,
+      handle: { preload: CountsResourcePage.preload } },
+    { path: 'more', element: <MorePage/>,
+      handle: { preload: MorePage.preload, sitemap: ['static'] } },
+    { path: '*', element: <NotFound/>, handle: { notFound: true } }]
+
+
+const matchPageRoutes = (pathname: string) =>
+    matchRoutes<PageRoute> (pageRoutes (null, () => { }), unlocalisedPath (pathname))
+
+
+export const preloadPageRoute = async (
+    pathname: string,
+    locale: LocaleCode,
+): Promise<void> => {
+  await Promise.all ((matchPageRoutes (pathname) ?? [])
+      .map (match => match.route.handle?.preload?.(locale)))
+}
+
+
+export const resolvePageRoute = (
+    pathname: string,
+): RouteMatch<string, PageRoute> | null => {
+  const match = matchPageRoutes (pathname)?.at (-1)
+  return (match == null || match.route.handle?.notFound) ? null : match
+}
+
+
+const RouteTransitionWrapper = ({ user, setUser }: {
+    user:    User | null
+    setUser: Dispatch<SetStateAction<User | null>> }) => {
+  const routes = useRoutes (pageRoutes (user, setUser))
+
+  return (
+      <AnimatePresence mode="wait" initial={false}>
+	<Suspense fallback={null}>{routes}</Suspense>
       </AnimatePresence>)
 }
 
@@ -128,12 +247,23 @@ const PostDetailRoute = ({ user }: { user: User | null }) => {
 }
 
 
-const RoutedApp: FC = () => {
-  const [user, setUser] = useState<User | null> (null)
+const RoutedApp = ({ locales }: { locales: AvailableLocale[] }) => {
+  const client = useQueryClient ()
+  const location = useLocation ()
+  const locale = useLocale ()
+  const route = resolvePageRoute (location.pathname)
+  const robots = route?.route.handle?.robots
+  const switchLocale = async (targetLocale: LocaleCode): Promise<string> => {
+    const resolve = route?.route.handle?.switchLocale
+    return (resolve != null && route != null)
+	? resolve ({ location, params: route.params, locale, targetLocale })
+	: switchLocalePath (location, targetLocale)
+  }
+  const [user, setUser] = useState<User | null> (
+      () => client.getQueryData<User> (sessionKeys.current) ?? null)
   const [status, setStatus] = useState (200)
   const behaviourSettings = useClientBehaviourSettings ()
   const animationMode = behaviourSettings.animation ?? 'normal'
-  const LayoutWrapper = animationMode === 'off' ? Fragment : LayoutGroup
 
   const appLayoutTransition = useMemo (
       () => (
@@ -164,36 +294,21 @@ const RoutedApp: FC = () => {
   }, [animationMode])
 
   useEffect (() => {
-    const createUser = async () => {
-      const data = await apiPost<{ code: string; user: User }> ('/users')
-      if (data.code)
-	{
-	  localStorage.setItem ('user_code', data.code)
-	  setUser (data.user)
-	}
-    }
-
-    const code = localStorage.getItem ('user_code')
-    if (code)
+    let cancelled = false
+    void (async () => {
+      try
       {
-	void (async () => {
-	  try
-	  {
-	    const data = await apiPost<{ valid: boolean; user: User }> ('/users/verify', { code })
-	    if (data.valid)
-	      setUser (data.user)
-	    else
-	      await createUser ()
-	  }
-	  catch (err)
-	  {
-	    if (isApiError (err))
-	      setStatus (err.response?.status ?? 200)
-	  }
-	}) ()
+	const user = await initialiseUserSession ()
+	if (!cancelled)
+	  setUser (user)
       }
-    else
-      createUser ()
+      catch (error)
+      {
+	if (!cancelled && isApiError (error))
+	  setStatus (error.response?.status ?? 503)
+      }
+    }) ()
+    return () => { cancelled = true }
   }, [])
 
   useEffect (() => {
@@ -228,6 +343,9 @@ const RoutedApp: FC = () => {
 
   return (
       <DialogueProvider>
+	<PageHead>
+	  {robots != null && <meta name="robots" content={robots}/>}
+	</PageHead>
 	<UnsavedChangesGuardProvider>
 	  <KeyboardShortcutsProvider>
 	  <MotionConfig
@@ -238,18 +356,17 @@ const RoutedApp: FC = () => {
 		    ? 'user'
 		    : 'always'
 	      }>
-	    <LayoutWrapper>
+	    <LayoutGroup>
 	      <motion.div
 		  layout={animationMode === 'off' ? false : 'position'}
 		  transition={{ layout: appLayoutTransition }}
 		  className="relative flex h-dvh w-full flex-col overflow-y-hidden">
-		<TopNav user={user}/>
+		<TopNav user={user} locales={locales} resolveLocaleSwitch={switchLocale}/>
 		<RouteTransitionWrapper
-		    animationMode={animationMode}
 		    user={user}
 		    setUser={setUser}/>
 	      </motion.div>
-	    </LayoutWrapper>
+	    </LayoutGroup>
 	  </MotionConfig>
 
 	  <Toaster/>
@@ -259,17 +376,73 @@ const RoutedApp: FC = () => {
 }
 
 
-const router = createBrowserRouter ([{
-    path: '*',
-    element: <RoutedApp/> }])
+const LocaleRoute: FC = () => {
+  const { locale } = useParams ()
+  const location = useLocation ()
+  const { i18n } = useTranslation ()
+  const { data, isError } = useQuery ({
+      queryKey: localesKeys.index,
+      queryFn: fetchLocales,
+      staleTime: 60_000,
+      refetchInterval: 60_000,
+      refetchOnMount: true,
+      refetchOnWindowFocus: true,
+      refetchOnReconnect: true })
+  const activeLocale =
+      (isLocaleCode (locale)
+       && data?.locales.some (entry => entry.code === locale))
+      ? locale
+      : null
+
+  useLayoutEffect (() => {
+    if (activeLocale != null)
+      document.documentElement.lang = activeLocale
+    if (activeLocale != null && i18n.language !== activeLocale)
+      void i18n.changeLanguage (activeLocale)
+  }, [activeLocale, i18n])
+
+  const redirect = legacyLocalePath (location)
+  if (!(isLocaleCode (locale)) && redirect == null)
+    return <NotFound/>
+  if (isError && data == null)
+    return <ServiceUnavailable/>
+  if (data == null)
+    return null
+  if (isLocaleCode (locale))
+  {
+    return data.locales.some (entry => entry.code === locale)
+        ? <RoutedApp locales={data.locales}/>
+        : <NotFound/>
+  }
+
+  return redirect == null ? <NotFound/> : <Navigate to={redirect} replace/>
+}
 
 
-const App: FC = () => (
+const LocaleRedirect = ({ to }: { to: string }) => {
+  const locale = useLocale ()
+  const location = useLocation ()
+  return <Navigate to={switchLocalePath ({ ...location, pathname: to }, locale)} replace/>
+}
+
+
+export const appRoutes = [
+    { path: '/:locale/*', element: <LocaleRoute/> },
+    { path: '*', element: <LocaleRoute/> }]
+
+
+export const AppFrame = ({ children }: { children: ReactNode }) => (
     <>
       <RouteBlockerOverlay/>
       {import.meta.env.DEV && <DevModeWatermark/>}
-      <RouterProvider router={router}/>
+      {children}
     </>)
 
 
+const App: FC = () => {
+  const [router] = useState (() => createBrowserRouter (appRoutes))
+  return <AppFrame><RouterProvider router={router}/></AppFrame>
+}
+
+
 export default App

frontend/src/components/DevModeWatermark.tsx

@@ -1,4 +1,7 @@
+import { useTranslation } from 'react-i18next'
+
 import nikumaru from '@/assets/fonts/nikumaru.otf'
+import { translateUIMessage } from '@/lib/i18n'
 
 import type { FC } from 'react'
 
@@ -8,6 +11,8 @@ const COLUMN_COUNT = 12
 
 
 const DevModeWatermark: FC = () => {
+  const { i18n } = useTranslation ('shared')
+  const text = translateUIMessage ('labels.development', 'shared', i18n.language)
   return (
       <div
 	  aria-hidden="true"
@@ -29,13 +34,14 @@ const DevModeWatermark: FC = () => {
 		{Array.from ({ length: COLUMN_COUNT }, (_, columnIndex) => (
 		    <span
 			key={columnIndex}
+			lang={text.language}
 			className={
 			    'whitespace-nowrap text-3xl font-bold '
 			    + 'tracking-[0.3em] text-neutral-950/5 '
 			    + 'dark:text-white/10'
 			}
 			style={{ fontFamily: 'Nikumaru' }}>
-		      開発モード
+		      {text.text}
 		    </span>))}
 	      </div>))}
 	</div>