#428

backend/app/controllers/application_controller.rb

@@ -1,10 +1,16 @@
 class ApplicationController < ActionController::API
+  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!
 
   def current_user = @current_user
 
@@ -93,5 +99,21 @@ 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/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/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
@@ -45,12 +46,12 @@ 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 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 +59,16 @@ 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 +80,7 @@ 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 +112,27 @@ 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 +141,22 @@ 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/tag_versions_controller.rb

@@ -35,8 +35,23 @@ class TagVersionsController < ApplicationController
   private
 
   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 +62,10 @@ 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 +73,8 @@ 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 +106,44 @@ 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
@@ -302,7 +305,8 @@ 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 render json: TagRepr.base(tag, language_code: locale.language_code) if tag
 
@@ -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
 

backend/app/controllers/users_controller.rb

@@ -21,6 +21,12 @@ class UsersController < ApplicationController
     render json: { valid: true, user: user.slice(:id, :name, :inheritance_code, :role) }
   end
 
+  def session
+    return head :unauthorized unless current_user
+
+    render json: current_user.slice(:id, :name, :role)
+  end
+
   def renew
     return head :unauthorized unless current_user
 

backend/app/controllers/wiki_pages_controller.rb

@@ -34,6 +34,25 @@ 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)
@@ -214,6 +233,7 @@ 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!
+  def will_generate_tag_names?
-    ApplicationRecord.transaction do
+    deprecated_at.nil? && (will_save_change_to_code? || will_save_change_to_deprecated_at?)
-      tag_ids = TagName.where(language_code:, primary_flg: true).pluck(:tag_id)
+  end
-      Tag.where.not(id: tag_ids).includes(:tag_names).find_each do
+
-        TagName.create!(tag_id: _1.id,
+  def save_with_tag_names!
-                        language_code:,
+    completed = self.class.transaction(requires_new: true) do
-                        name: TagName.generate_name(self, _1, _1.tag_name('ja')),
+      SharedResourceIdAllocator.lock_space!(Tag, 'tags')
-                        script_code:,
+      saved = yield
-                        primary_flg: true,
+      raise ActiveRecord::RecordNotSaved, 'Locale save was halted' unless saved
-                        auto_generated: true)
+
-      end
+      TagNameCompletion.for_locale!(self)
+      true
+    end
+    unless completed
+      raise ActiveRecord::RecordNotSaved, 'Locale tag completion was rolled back'
     end
   end
 end

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
 
@@ -259,20 +264,24 @@ class Tag < ApplicationRecord
       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:,
+        TagName.create!(tag:, language_code:, name:,
-                             script_code: locale.script_code, primary_flg: true,
+                        script_code: locale.script_code, primary_flg: true,
-                             auto_generated: false)
+                        auto_generated: false)
-        generate_tag_names!(locale, tag, tn)
+        TagNameCompletion.for_tag!(tag)
         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 +361,6 @@ 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．
+    fallback = "Tag_##{ tag.id }"
-
+    name =
-    "Tag_##{ tag.id }"
+        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/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/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
+    lock_space!(record.class, space)
-    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
 
     # 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 +1,117 @@
+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) })
+        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])
+        end
+        true
+      end
+      unless completed
+        raise ActiveRecord::RecordNotSaved, 'Locale tag completion was rolled back'
+      end
+    end
+
+    def for_tag! tag, locales: nil, certified_names: { }
+      locales ||=
+          Locale.where(deprecated_at: nil)
+          .order(:language_code, :created_at, :script_code).lock
+      Tag.transaction do
+        SharedResourceIdAllocator.lock_space!(Tag, 'tags')
+        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?
+
+          TagVersioning.ensure_snapshot!(tag, created_by_user: nil)
+          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
+          version = TagVersioning.record!(tag, event_type: :update, created_by_user: nil)
+          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
+    Tag.transaction do
-    record!(tag, event_type:, created_by_user:, language_code:)
+      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/routes.rb

@@ -1,4 +1,6 @@
 Rails.application.routes.draw do
+  resources :locales, only: [:index]
+
   resources :tag_groups, only: [:index, :show, :create, :update]
 
   resources :nico_tags, path: 'tags/nico', only: [:index, :show, :update]
@@ -43,6 +45,7 @@ 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
@@ -97,6 +100,7 @@ Rails.application.routes.draw do
     collection do
       post :verify
       get :me
+      get :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
+      TagNameCompletion.for_tag!(tag)
-          .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
     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
+  it 'accepts Ainu 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: 'ain', name: 'ain') }
-    expect { described_class.create!(code: 'en', name: 'English') }
         .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!
+  def create_ainu_locale!
-    prepare_english_reference!
+    prepare_ainu_reference!
-    described_class.create!(code: 'en', language_code: 'en',
+    described_class.create!(code: 'ain-Kana', language_code: 'ain',
-                            script_code: 'Latn', region_code: 826,
+                            script_code: 'Kana', region_code: 392,
-                            variants: '', name: 'English')
+                            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
@@ -35,63 +34,58 @@ 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))
+    expect(second.tag_names.find_by!(language_code: 'ain', primary_flg: true))
-        .to have_attributes(tag_id: second.id, language_code: 'en',
+        .to have_attributes(tag_id: second.id, language_code: 'ain',
-                            script_code: 'Latn', primary_flg: true,
+                            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_ainu_reference!
-    prepare_english_reference!
     tag = create(:tag, primary_name: 'already_named')
-    existing = create(:tag_name, name: 'existing_english', tag:,
+    existing = create(:tag_name, name: 'existing_ainu', tag:,
-                                 language_code: 'en', script_code: 'Latn')
+                                 language_code: 'ain', script_code: 'Kana')
 
-    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)
   end
 
-  it 'creates a primary name when the language has only an alias' do
+  it 'adds the new language primary while preserving existing names and aliases' do
-    pending '日本語以外の Locale 有効化は別課題で実装する'
+    tag = create(:tag, primary_name: 'named_tag')
-    prepare_english_reference!
+    create(:tag_name, :alias, name: 'existing_alias', tag:,
-    tag = create(:tag, primary_name: 'alias_only_tag')
+                              language_code: 'ja', script_code: 'Jpan')
-    alias_name = create(:tag_name, :alias, name: 'alias_en',
+    original_names = tag.tag_names.order(:id).map(&:attributes)
-                                          tag:,
-                                          language_code: 'en', script_code: 'Latn')
 
-    create_english_locale!
+    create_ainu_locale!
 
-    expect(alias_name.reload).to have_attributes(
+    expect(tag.tag_names.where(language_code: 'ja').order(:id).map(&:attributes))
-        tag_id: tag.id,
+        .to eq(original_names)
-        language_code: 'en', script_code: 'Latn', primary_flg: false)
+    generated = TagName.find_by!(tag_id: tag.id, language_code: 'ain', primary_flg: true)
-    generated = TagName.find_by!(tag_id: tag.id, language_code: 'en', primary_flg: true)
+    expect(generated).to have_attributes(name: 'named_tag', tag_id: tag.id, language_code: 'ain',
-    expect(generated).to have_attributes(tag_id: tag.id, language_code: 'en',
+                                         script_code: 'Kana', primary_flg: true,
-                                         script_code: 'Latn', 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_ainu_reference!
-    prepare_english_reference!
     first = create(:tag, primary_name: 'atomic_first')
     second = create(:tag, primary_name: 'atomic_second')
     allow(TagName).to receive(:generate_name).and_call_original
@@ -99,31 +93,27 @@ RSpec.describe Locale, type: :model do
         .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(described_class.exists?(code: 'ain-Kana')).to be(false)
-    expect(TagName.where(language_code: 'en', tag_id: [first.id, second.id])).to be_empty
+    expect(TagName.where(language_code: 'ain', tag_id: [first.id, second.id])).to be_empty
   end
 
-  it 'accepts a stable locale code outside the historical enum values' do
+  it 'rejects a private locale code outside the supported locale set' do
-    pending '日本語以外の Locale 有効化は別課題で実装する'
+    prepare_ainu_reference!
-    prepare_english_reference!
 
-    locale = described_class.create!(
+    expect {
-        code: 'en-x-rspec', language_code: 'en',
+      described_class.create!(
-        script_code: 'Latn', region_code: 826,
+          code: 'ain-Kana-x-rspec', language_code: 'ain',
-        variants: 'x-rspec', name: 'English')
+          script_code: 'Kana', region_code: 392,
-
+          variants: 'x-rspec', name: 'Ainu')
-    expect(locale.reload).to have_attributes(
+    }.to raise_error(ArgumentError)
-        code: 'en-x-rspec', language_code: 'en', script_code: 'Latn',
-        region_code: 826, variants: 'x-rspec')
   end
 
-  it 'registers the future British English locale tuple' do
+  it 'registers the supported Ainu locale tuple' do
-    pending '日本語以外の Locale 有効化は別課題で実装する'
 
-    expect(locale).to have_attributes(code: 'en', language_code: 'en',
+    expect(locale).to have_attributes(code: 'ain-Kana', language_code: 'ain',
-                                    script_code: 'Latn', region_code: 826,
+                                    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
+  it 'selects Kana 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'
     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',
+        ainu = create(:tag_name, name: 'temporary',
-                                   language_code: 'en', script_code: 'Latn')
+                                   language_code: 'ain', script_code: 'Kana')
-        english.update_columns(name: 'foo_bar')
+        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',
+        primary_tag_name_for(nipponese, 'ain').update!(
-                                        language_code: 'en', script_code: 'Latn')
+            name: 'different_ainu_name', auto_generated: false)
-        english = create(:tag, primary_tag_name: english_name)
+        ainu_name = create(:tag_name, name: 'temporary',
-        english_name.update_columns(name: 'foo_bar')
+                                        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(
+        expect(ainu_name.reload).to have_attributes(
-            name: 'foobar', language_code: 'en', tag_id: english.id)
+            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',
+    ainu = build(:tag_name, name: 'shared_name',
-                              language_code: 'en', script_code: 'Latn')
+                              language_code: 'ain', script_code: 'Kana')
 
-    expect(english).to be_valid
+    expect(ainu).to be_valid
-    expect { english.save! }.to change(described_class, :count).by(1)
+    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')
+      ainu_primary = primary_tag_name_for(tag, 'ain')
-      english_primary.update!(name: 'english_primary', auto_generated: false)
+      ainu_primary.update!(name: 'ainu_primary', auto_generated: false)
-      english_alias = create(:tag_name, :alias, tag:, name: 'english_alias',
+      ainu_alias = create(:tag_name, :alias, tag:, name: 'ainu_alias',
-                                                 language_code: 'en', script_code: 'Latn')
+                                                 language_code: 'ain', script_code: 'Kana')
       representative_id = tag.tag_name('ja')&.id
 
-      primary = described_class.find_by!(tag_id: english_alias.tag_id,
+      primary = described_class.find_by!(tag_id: ainu_alias.tag_id,
-                                         language_code: english_alias.language_code,
+                                         language_code: ainu_alias.language_code,
                                          primary_flg: true)
 
-      expect(primary).to eq(english_primary)
+      expect(primary).to eq(ainu_primary)
-      expect(described_class.canonicalise(locale, [english_alias.name]))
+      expect(described_class.canonicalise(locale, [ainu_alias.name]))
-          .to eq([english_primary.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',
+      ainu_name = create(:tag_name, name: 'ainu_canonical',
-                                      language_code: 'en', script_code: 'Latn')
+                                      language_code: 'ain', script_code: 'Kana')
-      english = create(:tag, primary_tag_name: english_name)
+      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',
+      ainu_alias = create(:tag_name, :alias, name: 'shared_alias',
-                                                tag: english,
+                                                tag: ainu,
-                                                language_code: 'en', script_code: 'Latn')
+                                                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(
+      expect(ainu_alias.reload).to have_attributes(
-          tag_id: english.id,
+          tag_id: ainu.id,
-          primary_flg: false, language_code: 'en')
+          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_ainu_reference!
-      prepare_english_reference!
       nipponese = create(:tag, primary_name: 'nipponese_canonical')
-      english_name = create(:tag_name, name: 'english_canonical',
+      ainu_name = build(:tag_name, tag: nil, name: 'ainu_canonical',
-                                      language_code: 'en', script_code: 'Latn')
+                                      language_code: 'ain', script_code: 'Kana')
-      english = create(:tag, primary_tag_name: english_name)
+      ainu = create(:tag, primary_tag_name: ainu_name)
-      primary_tag_name_for(english, 'ja').update!(
+      primary_tag_name_for(ainu, 'ja').update!(
-          name: 'english_in_nipponese', auto_generated: false)
+          name: 'ainu_in_nipponese', auto_generated: false)
-      english_locale = locale
+      ainu_locale = locale
       nipponese_alias = create(:tag_name, :alias, name: 'shared_alias',
                                                   tag: nipponese)
-      english_alias = create(:tag_name, :alias, name: 'shared_alias',
+      ainu_alias = create(:tag_name, :alias, name: 'shared_alias',
-                                                tag: english,
+                                                tag: ainu,
-                                                language_code: 'en', script_code: 'Latn')
+                                                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(
+      expect(ainu_alias.reload).to have_attributes(
-          tag_id: english.id,
+          tag_id: ainu.id,
-          primary_flg: false, language_code: 'en')
+          primary_flg: false, language_code: 'ain')
       expect(described_class.normalise_tags!(
-          english_locale, ['shared_alias'],
+          ainu_locale, ['shared_alias'],
-          with_tagme: false, with_no_deerjikist: false)).to eq([english])
+          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(
+        expect(primary_tag_name_for(tag, 'ain')).to have_attributes(
-            language_code: 'en', script_code: 'Latn',
+            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
+      it 'copies an Ainu-origin name to Japanese without reverse transcription' do
-        pending '日本語以外の Locale 有効化は別課題で実装する'
         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))
+                name: 'ainu_origin', auto_generated: true))
-        source_tag_name = TagName.find_by!(tag:, language_code: 'en', primary_flg: 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
+      it 'creates one primary per language when multiple locales use Ainu' do
-        pending '日本語以外の Locale 有効化は別課題で実装する'
         locale
         described_class.find_or_create_by_tag_name!(
-            locale, 'before_second_english_locale', category: :general)
+            locale, 'before_second_ainu_locale', category: :general)
-        Locale.create!(code: 'en-x-rspec', language_code: 'en',
-                       script_code: 'Latn', region_code: 826,
-                       variants: 'x-rspec', name: 'English')
 
         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(ainu).not_to eq(nipponese)
-        expect(primary_tag_name_for(english, 'en')).to have_attributes(
+        expect(primary_tag_name_for(ainu, 'ain')).to have_attributes(
-            name: 'same_name', tag_id: english.id, language_code: 'en', primary_flg: true)
+            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')
+        ainu = primary_tag_name_for(tag, 'ain')
-        english.update!(name: 'english_primary', auto_generated: false)
+        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(
+        expect(primary_tag_name_for(tags.first, 'ain')).to have_attributes(
-            name: 'normalised_english', language_code: 'en', script_code: 'Latn',
+            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')
+        ainu_primary = primary_tag_name_for(target_tag, 'ain')
-        source_primary = primary_tag_name_for(source_tag, 'en')
+        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(primary_tag_name_for(target_tag.reload, 'ain')).to eq(ainu_primary)
-        expect(TagName.where(tag: target_tag, language_code: 'en', primary_flg: true))
+        expect(TagName.where(tag: target_tag, language_code: 'ain', primary_flg: true))
-            .to contain_exactly(english_primary)
+            .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/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) }
 
@@ -54,13 +54,12 @@ 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 +71,6 @@ 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 +85,6 @@ 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 +99,6 @@ 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 +109,6 @@ 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 +122,6 @@ 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 +135,6 @@ 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 +150,179 @@ RSpec.describe 'Locale propagation on write paths', type: :request do
   end
 
   context 'with existing names in both languages' do
-    let(:english_name) do
+    let(:ainu_name) do
-      create(:tag_name, name: 'shared_name', language_code: 'en', script_code: 'Latn')
+      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!(name: 'shared_name')
-        primary_tag_name_for(tag, 'ja').update_columns(name: 'shared_name')
       end
     end
 
-    it 'plans and creates the post using the English identity and category' do
+    it 'plans and creates the post using the Ainu identity and category' do
-      pending '日本語以外の Locale 有効化は別課題で実装する'
       locale
-      english_tag
+      ainu_tag
       nipponese_tag
       post '/posts', params: {
-          locale: 'en', title: 'English identity',
+          locale: 'ain-Kana', title: 'Ainu identity',
-          url: 'https://example.com/english-identity', tags: 'shared_name', parent_post_ids: '' }
+          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
+    it 'updates the post using the Ainu identity' do
-      pending '日本語以外の Locale 有効化は別課題で実装する'
       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
+    it 'resolves the Ainu material tag' do
-      pending '日本語以外の Locale 有効化は別課題で実装する'
       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
+    it 'resolves the Ainu parent tag' do
-      pending '日本語以外の Locale 有効化は別課題で実装する'
       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
+    it 'resolves the Ainu 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'
       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
+  context 'when renaming or updating aliases in Ainu' do
-    let(:english_name) do
+    let(:ainu_name) do
-      create(:tag_name, name: 'english_original', language_code: 'en', script_code: 'Latn')
+      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 = primary_tag_name_for(other_tag, 'ain')
-      other_primary.update!(name: 'other_english_primary', auto_generated: false)
+      other_primary.update!(name: 'other_ainu_primary', auto_generated: false)
-      create(:tag_name, :alias, tag:, name: 'existing_english_alias',
+      create(:tag_name, :alias, tag:, name: 'existing_ainu_alias',
-                                language_code: 'en', script_code: 'Latn')
+                                language_code: 'ain', script_code: 'Kana')
-      primary_name_before = primary_tag_name_for(tag, 'en').name
+      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)
+            tag_id: other_tag.id, language_code: 'ain', primary_flg: true)
-        expect(TagName.where(tag: other_tag, language_code: 'en', 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(
+      expect(primary_tag_name_for(tag.reload, 'ain')).to have_attributes(
-          name: 'rename_target', language_code: 'en', tag_id: tag.id)
+          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',
+              script_code: 'Kana',
-              tag_id: tag.id, primary_flg: false, language_code: 'en')
+              tag_id: tag.id, primary_flg: false, language_code: 'ain')
-      primary = TagName.find_by!(tag_id: tag.id, language_code: 'en', primary_flg: true)
+      primary = TagName.find_by!(tag_id: tag.id, language_code: 'ain', primary_flg: true)
-      expect(primary).to have_attributes(name: 'english_original', script_code: 'Latn')
+      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 +332,7 @@ 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 +340,12 @@ 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',
+              tag_id: tag.id, script_code: 'Kana',
-              primary_flg: false, language_code: 'en')
+              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/posts_spec.rb

@@ -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_2', 'restore_name' => 'spec_tag_2',
-        { 'name' => 'spec_tag', 'type' => 'removed' }
+          '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/tag_group_locale_spec.rb

@@ -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/users_spec.rb

@@ -13,6 +13,24 @@ RSpec.describe 'Users', type: :request do
     { 'X-Transfer-Code' => user.inheritance_code }
   end
 
+  describe 'GET /users/session' do
+    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
     it 'creates guest user, IpAddress and UserIp, and returns code' do
       expect {

backend/spec/requests/wiki_locale_spec.rb

@@ -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
@@ -39,17 +39,17 @@ 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
 
@@ -57,14 +57,14 @@ RSpec.describe 'Wiki and native API locale contracts', type: :request 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 }
+      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/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 +73,7 @@ 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 +89,10 @@ 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 +108,20 @@ 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 +133,7 @@ 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 +145,14 @@ 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/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
+  it 'passes a future Ainu 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'
     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',
+      ainu_name = create(:tag_name, name: 'shared_name',
-                                      language_code: 'en', script_code: 'Latn')
+                                      language_code: 'ain', script_code: 'Kana')
-      english = create(:tag, primary_tag_name: english_name, category: :character)
+      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!(name: 'shared_name')
-      primary_tag_name_for(nipponese, 'ja').update_columns(name: 'shared_name')
+      ainu_parent_name = create(:tag_name, name: 'ainu_parent',
-      english_parent_name = create(:tag_name, name: 'english_parent',
+                                            language_code: 'ain', script_code: 'Kana')
-                                            language_code: 'en', script_code: 'Latn')
+      ainu_parent = create(:tag, primary_tag_name: ainu_parent_name,
-      english_parent = create(:tag, primary_tag_name: english_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',
+      ainu_name = create(:tag_name, name: 'ainu_canonical',
-                                      language_code: 'en', script_code: 'Latn')
+                                      language_code: 'ain', script_code: 'Kana')
-      english = create(:tag, primary_tag_name: english_name, category: :character)
+      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',
+      ainu_alias = create(:tag_name, :alias, name: 'shared_alias',
-                                               tag: english,
+                                               tag: ainu,
-                                               language_code: 'en', script_code: 'Latn')
+                                               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(
+      expect(ainu_alias.reload).to have_attributes(
-          tag_id: english.id,
+          tag_id: ainu.id,
-          primary_flg: false, language_code: 'en')
+          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',
@@ -97,8 +96,8 @@ RSpec.describe PostCreator do
 
         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')
+        tag_name = TagName.find_by!(language_code: 'ain', name: 'locale_character')
-        expect(tag_name).to have_attributes(script_code: 'Latn', primary_flg: true)
+        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 +1,68 @@
+require 'rails_helper'
+
+RSpec.describe TagNameCompletion do
+  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
+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)
+    primary_tag_name_for(tag, 'ain').update!(name: 'Ainu name', auto_generated: false)
-    create(:tag_name, :alias, tag:, language_code: 'en', script_code: 'Latn',
+    create(:tag_name, :alias, tag:, language_code: 'ain', script_code: 'Kana',
-                              name: 'English alias')
+                              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_ainu_names!
-    prepare_english_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
+  it 'creates a version for an Ainu-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_ainu_names!
-    prepare_english_names!
+    original = described_class.record!(tag:, event_type: :update, created_by_user: user)
-    original = described_class.record!(tag:, event_type: :create, created_by_user: user)
+    primary_tag_name_for(tag, 'ain').update!(name: 'Renamed')
-    primary_tag_name_for(tag, 'en').update!(name: 'Renamed')
 
     updated = described_class.record!(tag:, event_type: :update, created_by_user: user)
 
-    expect(updated.version_no).to eq(2)
+    expect(updated.version_no).to eq(original.version_no + 1)
-    expect(original.reload.names.fetch('en')).to include('name' => 'English name')
+    expect(original.reload.names.fetch('ain')).to include('name' => 'Ainu name')
-    expect(updated.names.fetch('en')).to include('name' => 'Renamed')
+    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_ainu_names!
-    prepare_english_names!
+    original = described_class.record!(tag:, event_type: :update, created_by_user: user)
-    described_class.record!(tag:, event_type: :create, created_by_user: user)
 
     unchanged = described_class.record!(tag:, event_type: :update, created_by_user: user)
 
-    expect(unchanged.version_no).to eq(1)
+    expect(unchanged.version_no).to eq(original.version_no)
-    expect(tag.reload.tag_versions.count).to eq(1)
+    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/locale_context.rb

@@ -1,22 +1,17 @@
-RSpec.shared_context 'English locale' do
+RSpec.shared_context 'Ainu locale' do
-  def prepare_english_reference!
+  def prepare_ainu_reference!
-    Language.find_or_create_by!(code: 'en') { _1.name = 'English' }
+    Language.find_or_create_by!(code: 'ain') { _1.name = 'ain' }
-    Script.find_or_create_by!(code: 'Latn') { _1.name = 'Latin' }
+    Script.find_or_create_by!(code: 'Kana') { _1.name = 'Kana' }
-    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
   end
 
   let(:locale) do
-    prepare_english_reference!
+    prepare_ainu_reference!
-    Locale.find_or_create_by!(code: 'en') do |record|
+    Locale.find_or_create_by!(code: 'ain-Kana') do |record|
-      record.language_code = 'en'
+      record.language_code = 'ain'
-      record.script_code = 'Latn'
+      record.script_code = 'Kana'
-      record.region_code = 826
+      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/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 id="root"><!-- outlet --></div>
-      <div class="flex flex-col h-screen w-screen">
+    <!-- ssr-state -->
-        <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>
     <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",
+      "version": "7.29.10",
-      "resolved": "https://registry.npmjs.org/@babel/runtime/-/runtime-7.27.6.tgz",
+      "resolved": "https://registry.npmjs.org/@babel/runtime/-/runtime-7.29.10.tgz",
-      "integrity": "sha512-vbavdySgbTTrmFE+EsiqUTzlOr5bzlnJtUv9PynGCAKvfQqjIXbvFdumPM/GxMDfyuGMJaJAU6TO4zc1Jf1i8Q==",
+      "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",
+    "build": "tsc -b && npm run build:client && npm run build:server",
-    "postbuild": "node scripts/generate-sitemap.js",
+    "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 +1,159 @@
+import { createReadStream } from 'node:fs'
+import { readFile, stat } from 'node:fs/promises'
+import { createServer } from 'node:http'
+import { createCipheriv, createDecipheriv, createHash, randomBytes } from 'node:crypto'
+import path from 'node:path'
+import { fileURLToPath } from 'node:url'
+
+import { render } 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 sessionSecret = process.env.SSR_COOKIE_SECRET
+if (process.env.NODE_ENV === 'production' && (!sessionSecret || sessionSecret.length < 32))
+  throw new Error ('SSR_COOKIE_SECRET must contain at least 32 characters in production')
+const sessionKey = createHash ('sha256').update (sessionSecret ?? randomBytes (32)).digest ()
+const cookieName = '__Host-btrc-session'
+const sessionSeconds = 7 * 24 * 60 * 60
+
+const encodeSession = code => {
+  const iv = randomBytes (12)
+  const cipher = createCipheriv ('aes-256-gcm', sessionKey, iv)
+  const payload = JSON.stringify ({ code, expires: Date.now () + sessionSeconds * 1000 })
+  const encrypted = Buffer.concat ([cipher.update (payload, 'utf8'), cipher.final ()])
+  return Buffer.concat ([iv, cipher.getAuthTag (), encrypted]).toString ('base64url')
+}
+
+const decodeSession = cookie => {
+  try
+  {
+    const token = cookie?.split (';').map (part => part.trim ())
+      .find (part => part.startsWith (`${cookieName}=`))?.slice (cookieName.length + 1)
+    if (!token || token.length > 2048) return undefined
+    const payload = Buffer.from (token, 'base64url')
+    const decipher = createDecipheriv ('aes-256-gcm', sessionKey, payload.subarray (0, 12))
+    decipher.setAuthTag (payload.subarray (12, 28))
+    const data = JSON.parse (Buffer.concat ([
+      decipher.update (payload.subarray (28)), decipher.final ()]).toString ('utf8'))
+    return typeof data.code === 'string' && data.expires > Date.now () ? data.code : undefined
+  }
+  catch
+  {
+    return undefined
+  }
+}
+const types = {
+    '.js': 'text/javascript', '.css': 'text/css', '.json': 'application/json',
+    '.png': 'image/png', '.gif': 'image/gif', '.jpg': 'image/jpeg',
+    '.svg': 'image/svg+xml', '.ico': 'image/x-icon', '.webp': 'image/webp',
+    '.woff': 'font/woff', '.woff2': 'font/woff2', '.otf': 'font/otf',
+    '.mp4': 'video/mp4', '.mp3': 'audio/mpeg', '.txt': 'text/plain' }
+
+if (process.env.NODE_ENV === 'production' && !process.env.PUBLIC_ORIGIN)
+  throw new Error ('PUBLIC_ORIGIN is required in production')
+
+const server = createServer (async (request, response) => {
+  response.setHeader ('Cache-Control', 'private, no-store')
+  const forwardedFor = request.headers['x-forwarded-for'] ?? request.socket.remoteAddress
+  if (request.url === '/_ssr/session')
+  {
+    if (request.method !== 'POST' || request.headers.origin !== origin)
+    {
+      response.writeHead (403).end ()
+      return
+    }
+    const code = request.headers['x-transfer-code']
+    if (typeof code !== 'string' || code.length > 512 || code.length === 0)
+    {
+      response.writeHead (400).end ()
+      return
+    }
+    try
+    {
+      const verified = await fetch (new URL ('users/session', apiBaseURL.replace (/\/?$/, '/')), {
+        headers: { 'X-Transfer-Code': code, 'X-Forwarded-For': forwardedFor },
+        signal: AbortSignal.timeout (10_000) })
+      if (!verified.ok)
+      {
+        response.writeHead (verified.status === 401 || verified.status === 403
+          ? verified.status : 503).end ()
+        return
+      }
+      response.setHeader ('Set-Cookie', `${cookieName}=${encodeSession (code)}; `
+        + `Path=/; HttpOnly; Secure; SameSite=Lax; Max-Age=${sessionSeconds}`)
+      response.writeHead (204).end ()
+    }
+    catch
+    {
+      response.writeHead (503).end ()
+    }
+    return
+  }
+  if (!['GET', 'HEAD'].includes (request.method))
+  {
+    response.writeHead (405, { Allow: 'GET, HEAD' }).end ()
+    return
+  }
+  try
+  {
+    const url = new URL (request.url, origin)
+    const pathname = decodeURIComponent (url.pathname)
+    const file = path.resolve (root, '.' + pathname)
+    const allowed = file.startsWith (root)
+        && !pathname.split ('/').some (segment => segment.startsWith ('.'))
+        && pathname !== '/index.html'
+    const info = allowed ? await stat (file).catch (() => null) : null
+    if (info?.isFile ())
+    {
+      response.writeHead (200, {
+	'Content-Type': types[path.extname (file)] ?? 'application/octet-stream',
+	'Content-Length': info.size,
+	'Cache-Control': /\/[^/]+-[\w-]{8}\.[^.]+$/.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, {
+      transferCode: decodeSession (request.headers.cookie), forwardedFor })
+    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 +1,308 @@
+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 = []
+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/session') return { id: 1, name: 'SSR account', role: 'admin' }
+  if (path === '/users/settings') return { theme: 'system', wiki_editor_mode: 'split' }
+  if (path === '/users/theme_slots') return []
+  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 === '/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 []
+  return null
+}
+
+before (async () => {
+  api = createServer ((request, response) => {
+    requests.push ({ method: request.method, url: request.url })
+    const url = new URL (request.url, 'http://localhost')
+    const data = responseFor (url)
+    response.writeHead (failAPI ? 503 : (data == null ? 404 : 200), {
+      'Content-Type': 'application/json' })
+    response.end (JSON.stringify (data))
+  })
+  await new Promise (resolve => api.listen (0, '127.0.0.1', resolve))
+  apiURL = `http://127.0.0.1:${api.address ().port}`
+  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,
+    SSR_COOKIE_SECRET: 'automated-check-only-not-a-production-secret' },
+    stdio: ['ignore', 'pipe', 'pipe'] })
+  httpOrigin = await new Promise ((resolve, reject) => {
+    node.stdout.on ('data', data => {
+      const match = data.toString ().match (/listening on (\d+)/)
+      if (match) resolve (`http://127.0.0.1:${match[1]}`)
+    })
+    node.on ('error', reject)
+    node.on ('exit', code => reject (new Error (`SSR server exited ${code}`)))
+  })
+  vite = await createViteServer ({ server: { middlewareMode: true }, appType: 'custom' })
+  const { pageRoutes } = await vite.ssrLoadModule ('/src/App.tsx')
+  const flatten = (entries, parent = '') => entries.flatMap (route => {
+    const path = [parent, route.path].filter (Boolean).join ('/')
+    return route.children ? flatten (route.children, path) : [{ ...route, path }]
+  })
+  routes = flatten (pageRoutes (null, () => {}))
+})
+
+after (async () => {
+  await vite?.close ()
+  node?.kill ()
+  api?.closeAllConnections ()
+  await new Promise (resolve => api?.close (resolve))
+})
+
+test ('every canonical screen route returns page HTML without JavaScript', async t => {
+  for (const route of routes) {
+    for (const locale of ['ja', 'ain-Kana']) {
+      const path = route.path.replace (':identifier', 'home').replace (/:id|:title/g, '1')
+        .replace ('*', 'unknown-screen')
+      const url = `/${locale}/${path}?from=2026-09-15&to=2026-09-15`
+      await t.test (`${locale} ${route.path}`, async () => {
+        const result = await render (url, origin, apiURL, { transferCode: 'test-secret' })
+        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-secret/)
+        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 ${locale}|SSR`))
+        assert.doesNotMatch (result.html, /Switched to client rendering|template id="B:/)
+      })
+    }
+  }
+})
+
+test ('parallel localized requests keep list data isolated', async () => {
+  const pages = await Promise.all (['ja', 'ain-Kana', 'ja', 'ain-Kana'].map (locale =>
+    render (`/${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 ${locale}`))
+    assert.equal (page.status, 200)
+    const state = JSON.parse (page.bootstrap)
+    assert.equal (state.locale, locale)
+  }
+  assert.ok (requests.some (request => request.url.includes ('page=2')))
+  assert.ok (requests.every (request => request.method === 'GET'))
+})
+
+test ('unknown resources and legacy URLs have correct status', async () => {
+  assert.equal ((await render ('/ja/unknown', origin, apiURL)).status, 404)
+  assert.equal ((await render ('/ja/help/unknown', origin, apiURL)).status, 404)
+  assert.equal ((await render ('/ja/posts/999', origin, apiURL)).status, 404)
+  const redirect = await render ('/help/home?edition=2026-09-15', origin, apiURL)
+  assert.equal (redirect.status, 308)
+  assert.equal (redirect.location, '/ja/help/home?edition=2026-09-15')
+})
+
+test ('HTTP cookie migration, CSRF protection, and API failure', async () => {
+  const rejected = await fetch (`${httpOrigin}/_ssr/session`, {
+    method: 'POST', headers: { Origin: 'https://other.invalid', 'X-Transfer-Code': 'test-secret' } })
+  assert.equal (rejected.status, 403)
+  const created = await fetch (`${httpOrigin}/_ssr/session`, {
+    method: 'POST', headers: { Origin: origin, 'X-Transfer-Code': 'test-secret' } })
+  assert.equal (created.status, 204)
+  const cookie = created.headers.get ('set-cookie')
+  assert.match (cookie, /HttpOnly; Secure; SameSite=Lax/)
+  assert.doesNotMatch (cookie, /test-secret/)
+  const settings = await fetch (`${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-secret/)
+  assert.match (settings.headers.get ('cache-control'), /private, no-store/)
+  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)
+  failAPI = true
+  try {
+    assert.equal ((await fetch (`${httpOrigin}/ja/posts`)).status, 503)
+  } finally {
+    failAPI = false
+  }
+})
+
+test ('hydrate every route with stored browser preferences', {
+  skip: !process.env.SSR_CHROME_PATH, timeout: 180_000,
+}, async t => {
+  const { default: WebSocket } = await import ('ws')
+  const chrome = spawn (process.env.SSR_CHROME_PATH, [
+    '--headless', '--no-sandbox', '--disable-gpu', '--disable-dev-shm-usage',
+    '--remote-debugging-port=0', `--user-data-dir=/tmp/btrc-ssr-browser-${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 = []
+    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 && url.pathname !== '/_ssr/session') {
+          void send ('Fetch.continueRequest', { requestId }, message.sessionId)
+          return
+        }
+        const data = url.pathname === '/users/verify'
+          ? { valid: true, user: { id: 1, name: 'SSR account', role: 'admin',
+              inheritance_code: 'test-secret' } }
+          : 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 (' '))
+      }
+    })
+    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 ('Fetch.enable', { patterns: [{ urlPattern: '*' }] }, sessionId)
+    const session = await fetch (`${httpOrigin}/_ssr/session`, {
+      method: 'POST', headers: { Origin: origin, 'X-Transfer-Code': 'test-secret' } })
+    await send ('Network.setExtraHTTPHeaders', { headers: {
+      Cookie: session.headers.get ('set-cookie').split (';')[0] } }, sessionId)
+    await send ('Page.addScriptToEvaluateOnNewDocument', { source: `
+      localStorage.setItem('user_code','test-secret');
+      localStorage.setItem('btrc_hub.client_settings',JSON.stringify({
+        lists:{postList:{limit:50},tagList:{limit:50},postSearch:{limit:50}},
+        behavior:{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});` }, 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)) {
+      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)
+        })
+      }
+    }
+  } finally {
+    ws?.close ()
+    chrome.kill ()
+  }
+})

frontend/src/App.tsx

@@ -1,18 +1,27 @@
+import { useQuery, useQueryClient } from '@tanstack/react-query'
 import { AnimatePresence, LayoutGroup, MotionConfig, motion } from 'framer-motion'
-import { Fragment, useEffect, useMemo, useState } from 'react'
+import { Suspense, lazy, useEffect, useLayoutEffect, useMemo, useState } from 'react'
+import { useTranslation } from 'react-i18next'
 import { createBrowserRouter,
+	 matchRoutes,
 	 Navigate,
-	 Route,
 	 RouterProvider,
-	 Routes,
+	 useLocation,
-	 useLocation } from 'react-router-dom'
+	 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 { prepareHelpPage } from '@/lib/help'
+import { fetchLocales, isLocaleCode, legacyLocalePath,
+	 switchLocalePath, unlocalisedPath } from '@/lib/locales'
+import { localesKeys, sessionKeys } from '@/lib/queryKeys'
+import { useLocale } from '@/lib/useLocale'
 import { applyClientAnimationMode,
 	 applyClientAppearance,
 	 fetchUserThemeSlots,
@@ -25,98 +34,135 @@ 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 { Dispatch, FC, ReactNode, SetStateAction } from 'react'
+import type { RouteMatch } from 'react-router-dom'
 
 import type { ClientAnimationMode } from '@/lib/settings'
+import type { AvailableLocale } from '@/lib/locales'
+import type { PageRoute } from '@/lib/routeLocales'
 import type { User } from '@/types'
 
+const GekanatorPage = lazy (() => import ('@/pages/GekanatorPage'))
+const DeerjikistDetailPage = lazy (() => import ('@/pages/deerjikists/DeerjikistDetailPage'))
+const MaterialBasePage = lazy (() => import ('@/pages/materials/MaterialBasePage'))
+const MaterialDetailPage = lazy (() => import ('@/pages/materials/MaterialDetailPage'))
+const MaterialHistoryPage = lazy (() => import ('@/pages/materials/MaterialHistoryPage'))
+const MaterialListPage = lazy (() => import ('@/pages/materials/MaterialListPage'))
+const MaterialNewPage = lazy (() => import ('@/pages/materials/MaterialNewPage'))
+const MaterialSyncSuppressionsPage = lazy (
+    () => import ('@/pages/materials/MaterialSyncSuppressionsPage'))
+const MorePage = lazy (() => import ('@/pages/MorePage'))
+const GekanatorUnavailablePage = lazy (() => import ('@/pages/GekanatorUnavailablePage'))
+const NicoTagListPage = lazy (() => import ('@/pages/tags/NicoTagListPage'))
+const TOSPage = lazy (() => import ('@/pages/TOSPage'))
+const HelpChangesPage = lazy (() => import ('@/pages/help/HelpChangesPage'))
+const HelpDiffPage = lazy (() => import ('@/pages/help/HelpDiffPage'))
+const HelpListPage = lazy (() => import ('@/pages/help/HelpListPage'))
+const PostDetailPage = lazy (() => import ('@/pages/posts/PostDetailPage'))
+const PostHistoryPage = lazy (() => import ('@/pages/posts/PostHistoryPage'))
+const PostNewPage = lazy (() => import ('@/pages/posts/PostNewPage'))
+const PostListPage = lazy (() => import ('@/pages/posts/PostListPage'))
+const PostSearchPage = lazy (() => import ('@/pages/posts/PostSearchPage'))
+const SettingPage = lazy (() => import ('@/pages/users/SettingPage'))
+const TagDetailPage = lazy (() => import ('@/pages/tags/TagDetailPage'))
+const TagHistoryPage = lazy (() => import ('@/pages/tags/TagHistoryPage'))
+const TagListPage = lazy (() => import ('@/pages/tags/TagListPage'))
+const TheatreDetailPage = lazy (() => import ('@/pages/theatres/TheatreDetailPage'))
+const WikiDetailPage = lazy (() => import ('@/pages/wiki/WikiDetailPage'))
+const WikiDiffPage = lazy (() => import ('@/pages/wiki/WikiDiffPage'))
+const WikiEditPage = lazy (() => import ('@/pages/wiki/WikiEditPage'))
+const WikiHistoryPage = lazy (() => import ('@/pages/wiki/WikiHistoryPage'))
+const WikiNewPage = lazy (() => import ('@/pages/wiki/WikiNewPage'))
+const WikiSearchPage = lazy (() => import ('@/pages/wiki/WikiSearchPage'))
+
+
+const GekanatorRoute = ({ user }: { user: User | null }) => {
+  const locale = useLocale ()
+  const location = useLocation ()
+  const pageLocale = resolvePageRoute (location.pathname)?.route.handle?.locale
+
+  if (pageLocale != null && pageLocale !== locale)
+    return <GekanatorUnavailablePage/>
+
+  return (
+      <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/> },
+    { path: 'posts/new', element: <PostNewPage user={user}/>,
+      handle: { robots: 'noindex' } },
+    { path: 'posts/search', element: <PostSearchPage/> },
+    { path: 'posts/:id', element: <PostDetailRoute user={user}/> },
+    { path: 'posts/changes', element: <PostHistoryPage/> },
+    { path: 'tags', element: <TagListPage/> },
+    { path: 'tags/:id', element: <TagDetailPage/> },
+    { path: 'tags/:id/deerjikists', element: <DeerjikistDetailPage/> },
+    { path: 'tags/nico', element: <NicoTagListPage user={user}/> },
+    { path: 'nico/tags', element: <NicoTagListPage user={user}/> },
+    { path: 'tags/changes', element: <TagHistoryPage/> },
+    { path: 'theatres/:id', element: <TheatreDetailPage user={user}/> },
+    { path: 'materials', element: <MaterialBasePage/>, children: [
+	{ index: true, element: <MaterialListPage/> },
+	{ path: 'changes', element: <MaterialHistoryPage/> },
+	{ path: 'new', element: <MaterialNewPage/>, handle: { robots: 'noindex' } },
+	{ path: 'suppressions', element: <MaterialSyncSuppressionsPage/>,
+	  handle: { robots: 'noindex', authentication: 'user' } },
+	{ path: ':id', element: <MaterialDetailPage/> }] },
+    { path: 'wiki', element: <WikiSearchPage/> },
+    { path: 'wiki/:title', element: <WikiDetailPage/> },
+    { path: 'wiki/new', element: <WikiNewPage user={user}/>,
+      handle: { robots: 'noindex' } },
+    { path: 'wiki/:id/edit', element: <WikiEditPage user={user}/>,
+      handle: { robots: 'noindex' } },
+    { path: 'wiki/:id/diff', element: <WikiDiffPage/> },
+    { path: 'wiki/changes', element: <WikiHistoryPage/> },
+    { path: 'help', element: <HelpListPage/> },
+    { path: 'help/changes', element: <HelpChangesPage/> },
+    { path: 'help/:identifier/diff', element: <HelpDiffPage/> },
+    { id: 'help.detail', path: 'help/:identifier', element: <HelpDetailPage/>,
+      handle: { prepare: prepareHelpPage } },
+    { path: 'users/settings', element: <SettingPage user={user} setUser={setUser}/>,
+      handle: { robots: 'noindex', authentication: 'user' } },
+    { path: 'settings', element: <LocaleRedirect to="/users/settings"/>,
+      handle: { redirectTo: '/users/settings' } },
+    { path: 'tos', element: <TOSPage/> },
+    { id: 'gekanator', path: 'gekanator', element: <GekanatorRoute user={user}/>,
+      handle: { locale: 'ja' } },
+    { path: 'more', element: <MorePage/> },
+    { path: '*', element: <NotFound/>, handle: { notFound: true } }]
+
+
+export const resolvePageRoute = (
+    pathname: string,
+): RouteMatch<string, PageRoute> | null => {
+  const match = matchRoutes<PageRoute> (
+      pageRoutes (null, () => { }), unlocalisedPath (pathname))?.at (-1)
+  return (match == null || match.route.handle?.notFound) ? null : match
+}
+
 
 const RouteTransitionWrapper = ({ animationMode, user, setUser }: {
     animationMode:  ClientAnimationMode
     user:           User | null
     setUser:        Dispatch<SetStateAction<User | null>> }) => {
-  const location = useLocation ()
+  const routes = useRoutes (pageRoutes (user, setUser))
-
-  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
 
   return (
-      <AnimatePresence mode="wait">
+      <AnimatePresence mode="wait" initial={animationMode !== 'off'}>
-	{routes}
+	<Suspense fallback={null}>{routes}</Suspense>
       </AnimatePresence>)
 }
 
@@ -128,12 +174,15 @@ const PostDetailRoute = ({ user }: { user: User | null }) => {
 }
 
 
-const RoutedApp: FC = () => {
+const RoutedApp = ({ locales }: { locales: AvailableLocale[] }) => {
-  const [user, setUser] = useState<User | null> (null)
+  const client = useQueryClient ()
+  const location = useLocation ()
+  const robots = resolvePageRoute (location.pathname)?.route.handle?.robots
+  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 (
       () => (
@@ -228,6 +277,9 @@ const RoutedApp: FC = () => {
 
   return (
       <DialogueProvider>
+	<PageHead>
+	  {robots != null && <meta name="robots" content={robots}/>}
+	</PageHead>
 	<UnsavedChangesGuardProvider>
 	  <KeyboardShortcutsProvider>
 	  <MotionConfig
@@ -238,18 +290,18 @@ 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}/>
 		<RouteTransitionWrapper
 		    animationMode={animationMode}
 		    user={user}
 		    setUser={setUser}/>
 	      </motion.div>
-	    </LayoutWrapper>
+	    </LayoutGroup>
 	  </MotionConfig>
 
 	  <Toaster/>
@@ -259,17 +311,76 @@ const RoutedApp: FC = () => {
 }
 
 
-const router = createBrowserRouter ([{
+const LocaleRoute: FC = () => {
-    path: '*',
+  const { locale } = useParams ()
-    element: <RoutedApp/> }])
+  const location = useLocation ()
+  const { i18n } = useTranslation ()
+  const { data, isPending, isError, refetch } = useQuery ({
+      queryKey: localesKeys.index,
+      queryFn: fetchLocales,
+      staleTime: 0,
+      refetchOnMount: 'always',
+      refetchOnWindowFocus: 'always',
+      refetchOnReconnect: 'always' })
+  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])
+
+  useEffect (() => {
+    void refetch ()
+  }, [location.key, refetch])
+
+  const redirect = legacyLocalePath (location)
+  if (!(isLocaleCode (locale)) && redirect == null)
+    return <NotFound/>
+  if (isError)
+    return <ServiceUnavailable/>
+  if (isPending)
+    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>

frontend/src/components/ErrorScreen.test.tsx

@@ -1,5 +1,6 @@
 import { render, screen } from '@testing-library/react'
 import { HelmetProvider } from 'react-helmet-async'
+import { MemoryRouter } from 'react-router-dom'
 import { describe, expect, it } from 'vitest'
 
 import ErrorScreen from '@/components/ErrorScreen'
@@ -12,9 +13,9 @@ describe ('ErrorScreen', () => {
     [503, '鯖死んでるよ（泣）'],
   ]) ('renders status %s', (status, message) => {
     render (
-        <HelmetProvider>
+        <MemoryRouter><HelmetProvider>
           <ErrorScreen status={status}/>
-        </HelmetProvider>,
+        </HelmetProvider></MemoryRouter>,
     )
 
     expect (screen.getByText (String (status))).toBeInTheDocument ()
@@ -24,9 +25,9 @@ describe ('ErrorScreen', () => {
 
   it ('throws for unsupported statuses', () => {
     expect (() => render (
-        <HelmetProvider>
+        <MemoryRouter><HelmetProvider>
           <ErrorScreen status={418}/>
-        </HelmetProvider>,
+        </HelmetProvider></MemoryRouter>,
     )).toThrow ()
   })
 })

frontend/src/components/ErrorScreen.tsx

@@ -1,9 +1,9 @@
-import { Helmet } from 'react-helmet-async'
-
 import nikumaru from '@/assets/fonts/nikumaru.otf'
 import errorImg from '@/assets/images/not-found.gif'
 import MainArea from '@/components/layout/MainArea'
-import { SITE_TITLE } from '@/config'
+import PageHead from '@/components/common/PageHead'
+import { useUITranslation } from '@/lib/useUITranslation'
+import { currentRenderContext } from '@/lib/renderContext'
 
 import type { FC } from 'react'
 
@@ -11,17 +11,19 @@ type Props = { status: number }
 
 
 const ErrorScreen: FC<Props> = ({ status }) => {
-  const [message, rightMsg, leftMsg]: [string, string, string] = (() => {
+  const context = currentRenderContext ()
+  if (context != null)
+    context.status = status
+  const { message: translate, label } = useUITranslation ('errors')
+  const [message]: [string, string, string] = (() => {
     switch (status)
     {
     case 403:
-      return ['権限ないよ（笑）', '帰れ！', '帰れ！']
     case 404:
-      return ['ページないよ（笑）', '帰れ！', '帰れ！']
     case 500:
-      return ['鯖でエラー出たって（嘲笑）', '管理人に', '聯絡を！']
     case 503:
-      return ['鯖死んでるよ（泣）', '管理人に', '聯絡を！']
+      return [translate (`${ status }.message`).text,
+	      translate (`${ status }.right`).text, translate (`${ status }.left`).text]
     default:
       throw new Error
     }
@@ -29,21 +31,14 @@ const ErrorScreen: FC<Props> = ({ status }) => {
 
   const title = message.replaceAll ('（', ' (').replaceAll ('）', ')')
 
-  const style = document.createElement ('style')
-  style.innerHTML = `
-      @font-face
-      {
-	font-family: 'Nikumaru';
-	src: url(${ nikumaru }) format('opentype');
-      }`
-  document.head.appendChild (style)
-
   return (
       <MainArea>
-	<Helmet>
+	<PageHead title={{ text: title,
+	    language: translate (`${status}.message`).language }}>
 	  <meta name="robots" content="noindex"/>
-	  <title>{title} | {SITE_TITLE}</title>
+	  <style>{`@font-face { font-family: 'Nikumaru';
-	</Helmet>
+	    src: url(${nikumaru}) format('opentype'); }`}</style>
+	</PageHead>
 	<div className="text-6xl font-bold text-transparent
 			bg-[linear-gradient(90deg,#ff0000,#ff8800,#ffff00,#00ff00,#00ffff,#0000ff,#ff00ff,#ff0000)]
 			bg-clip-text bg-[length:200%_100%] animate-rainbow-scroll drop-shadow-[0_0_6px_black]
@@ -51,11 +46,11 @@ const ErrorScreen: FC<Props> = ({ status }) => {
 	     style={{ fontFamily: 'Nikumaru' }}>
 	  <p>{status}</p>
 	  <div className="flex flex-row space-x-1 sm:space-x-2 md:space-x-4">
-	    <p style={{ writingMode: 'vertical-rl' }}>{leftMsg}</p>
+	    <p style={{ writingMode: 'vertical-rl' }}>{label (`${ status }.left`)}</p>
-	    <img className="max-w-[70vw]" src={errorImg} alt="逃げたギター"/>
+	    <img className="max-w-[70vw]" src={errorImg} alt={translate ('imageAlt').text}/>
-	    <p style={{ writingMode: 'vertical-rl' }}>{rightMsg}</p>
+	    <p style={{ writingMode: 'vertical-rl' }}>{label (`${ status }.right`)}</p>
 	  </div>
-	  <p className="mr-[-.5em]">{message}</p>
+	  <p className="mr-[-.5em]">{label (`${ status }.message`)}</p>
 	</div>
       </MainArea>)
 }

frontend/src/components/LocalisedText.test.tsx

@@ -0,0 +1,47 @@
+import { render } from '@testing-library/react'
+import { describe, expect, it } from 'vitest'
+
+import LocalisedText from '@/components/LocalisedText'
+
+
+describe ('LocalisedText', () => {
+  it.each ([
+      ['ネコ　チャペ', ['ネコ', 'チャペ']],
+      ['ネコ、チャペ', ['ネコ、', 'チャペ']],
+      ['著作者人格権、商標権、肖像権、パブリシティー権',
+       ['著作者人格権、', '商標権、', '肖像権、', 'パブリシティー権']],
+      ['ネコ、チャペ。', ['ネコ、', 'チャペ。']],
+      ['ネコ、「チャペ」。', ['ネコ、', '「チャペ」。']],
+      ['ネコ，、」チャペ', ['ネコ，、」', 'チャペ']]]) (
+      'adds word boundaries without changing %s', (text, words) => {
+	const { container } = render (<LocalisedText language="ain">{text}</LocalisedText>)
+	const wrapper = container.firstElementChild!
+	expect (wrapper).toHaveAttribute ('lang', 'ain-Kana')
+	expect (wrapper.textContent).toBe (text)
+	expect (Array.from (wrapper.querySelectorAll ('.ainu-ui-word'), node => node.textContent))
+	    .toEqual (words)
+	expect (wrapper.querySelectorAll ('wbr')).toHaveLength (words.length - 1)
+      })
+
+  it ('preserves Japanese fallback and links and code inside an Ainu paragraph', () => {
+    const { container } = render (
+	<LocalisedText language="ain">
+	  <span lang="ja">日本語、本文</span>
+	  <a href="https://example.com">ネコ　チャペ</a>
+	  <code>ネコ　チャペ</code>
+	  <strong>ネコ　チャペ</strong>
+	</LocalisedText>)
+    expect (container.querySelector ('[lang="ja"] .ainu-ui-word')).toBeNull ()
+    expect (container.querySelector ('a .ainu-ui-word')).toBeNull ()
+    expect (container.querySelector ('code .ainu-ui-word')).toBeNull ()
+    expect (container.querySelectorAll ('strong .ainu-ui-word')).toHaveLength (2)
+  })
+
+  it ('does not apply Ainu word splitting to Japanese text', () => {
+    const { container } = render (
+	<LocalisedText language="ja">ネコ、チャペ。</LocalisedText>)
+    expect (container.firstElementChild).toHaveAttribute ('lang', 'ja')
+    expect (container.querySelector ('.ainu-ui-word')).toBeNull ()
+    expect (container.textContent).toBe ('ネコ、チャペ。')
+  })
+})

frontend/src/components/LocalisedText.tsx

@@ -0,0 +1,89 @@
+import { Children, cloneElement, Fragment, isValidElement } from 'react'
+
+import { cn } from '@/lib/utils'
+
+import type { ReactNode } from 'react'
+
+
+export const formatUIString = (text: string, language: string): string =>
+    (language === 'ain' || language === 'ain-Kana')
+    ? text.replace (/[ \t\r\n]+/g, '\u3000')
+    : text
+
+
+const splitAinuText = (text: string): string[] => {
+  const parts: string[] = []
+  let part = ''
+  let boundary = false
+  for (const character of text)
+  {
+    // Keep punctuation runs and closing brackets/quotes with the preceding word.
+    if (boundary && !/[\u3000、，,。．\p{Pe}\p{Pf}]/u.test (character))
+    {
+      parts.push (part)
+      part = ''
+      boundary = false
+    }
+    part += character
+    if (/[\u3000、，,。．]/u.test (character))
+      boundary = true
+  }
+  if (part !== '')
+    parts.push (part)
+  return parts
+}
+
+
+export const localiseUIChildren = (children: ReactNode, language: string): ReactNode => {
+  if (language !== 'ain' && language !== 'ain-Kana')
+    return children
+
+  return Children.map (children, child => {
+    if (typeof child === 'string')
+    {
+      const parts = splitAinuText (formatUIString (child, language))
+      return parts.map ((part, index) => {
+	const spaces = part.match (/\u3000+$/u)?.[0] ?? ''
+	const word = part.slice (0, part.length - spaces.length)
+	return (
+	    <Fragment key={index}>
+	      {word !== '' && <span className="ainu-ui-word">{word}</span>}
+	      {spaces}
+	      {index < parts.length - 1 && <wbr/>}
+	    </Fragment>)
+      })
+    }
+
+    if (isValidElement<{ children?: ReactNode; lang?: string }> (child))
+    {
+      // Only traverse inline formatting owned by the renderer. Components,
+      // links and code retain their own children and behaviour.
+      const inline = child.type === Fragment
+	  || (typeof child.type === 'string'
+	      && ['span', 'em', 'strong', 'del', 's', 'b', 'i', 'u',
+		  'small', 'mark', 'sup', 'sub'].includes (child.type))
+      if (!inline
+	  || (child.props.lang != null && !(child.props.lang.startsWith ('ain'))))
+	return child
+      return cloneElement (child, { }, localiseUIChildren (child.props.children, language))
+    }
+
+    return child
+  })
+}
+
+
+const LocalisedText = (
+    { children, language, className }: {
+	children: ReactNode
+	language: string
+	className?: string },
+) => (
+    <span lang={language === 'ain' ? 'ain-Kana' : language}
+	className={cn ((language === 'ain' || language === 'ain-Kana') && 'ainu-ui-text',
+		      className)}>
+      {localiseUIChildren (children, language)}
+    </span>)
+
+
+export default LocalisedText

frontend/src/components/MaterialSidebar.tsx

@@ -1,19 +1,20 @@
 import { useQuery } from '@tanstack/react-query'
 import { useEffect, useRef, useState } from 'react'
-import { useLocation, useNavigate } from 'react-router-dom'
+import { useLocation } from 'react-router-dom'
 
+import { useLocale, useLocaleNavigate } from '@/lib/useLocale'
 import SidebarComponent from '@/components/layout/SidebarComponent'
 import TagLink from '@/components/TagLink'
 import { fetchMaterialTagTree, parseMaterialFilter } from '@/lib/materials'
 import { materialsKeys } from '@/lib/queryKeys'
 import { cn } from '@/lib/utils'
+import { useUITranslation } from '@/lib/useUITranslation'
 
 import type { CSSProperties, Dispatch, FC, ReactNode, SetStateAction } from 'react'
 
 import type { MaterialFilter, MaterialSidebarTag, Tag } from '@/types'
 
 const FILTERS: MaterialFilter[] = ['missing', 'present', 'any']
-const FILTER_LABELS: Record<MaterialFilter, string> = { present: '有', missing: '無', any: '全' }
 
 
 const px = (value: string): number => {
@@ -83,7 +84,7 @@ const tagSelectionShellClass = (selected: boolean): string =>
 const updateMaterialFilterQuery = (
     pathname: string,
     locationSearch: string,
-    navigate: ReturnType<typeof useNavigate>,
+    navigate: ReturnType<typeof useLocaleNavigate>,
     materialFilter: MaterialFilter,
 ) => {
   const qs = new URLSearchParams (locationSearch)
@@ -95,24 +96,27 @@ const updateMaterialFilterQuery = (
 const MaterialFilterButtons: FC<{ materialFilter: MaterialFilter
 				  onChange:       (materialFilter: MaterialFilter) => void }> = (
     { materialFilter, onChange },
-) => (
+) => {
-    <div className="flex flex-wrap gap-2 justify-end md:justify-start flex-center">
+  const { label } = useUITranslation ('materials')
-      <label className="my-auto text-sm font-bold">素材：</label>
+  return (
-      {FILTERS.map (value => (
+      <div className="flex flex-wrap gap-2 justify-end md:justify-start flex-center">
-	  <button
+	<label className="my-auto text-sm font-bold">{label ('sidebar.label')}</label>
-	      key={value}
+	{FILTERS.map (value => (
-	      type="button"
+	    <button
-	      onClick={() => onChange (value)}
+		key={value}
-	      className={cn (
+		type="button"
-		  'rounded-full border px-3 py-1 text-sm',
+		onClick={() => onChange (value)}
-		  (materialFilter === value
+		className={cn (
-		   ? ['border-sky-500 bg-sky-50 text-sky-700 dark:border-sky-400',
+		    'rounded-full border px-3 py-1 text-sm',
-		      'dark:bg-sky-950 dark:text-sky-100']
+		    (materialFilter === value
-		   : ['border-neutral-300 bg-white text-neutral-700 dark:border-stone-700',
+		     ? ['border-sky-500 bg-sky-50 text-sky-700 dark:border-sky-400',
-		      'dark:bg-stone-900 dark:text-stone-200']))}>
+			'dark:bg-sky-950 dark:text-sky-100']
-	    {FILTER_LABELS[value]}
+		     : ['border-neutral-300 bg-white text-neutral-700 dark:border-stone-700',
-	  </button>))}
+			'dark:bg-stone-900 dark:text-stone-200']))}>
-    </div>)
+	      {label (`sidebar.${value}`)}
+	    </button>))}
+      </div>)
+}
 
 
 const MaterialTreeNode: FC<{
@@ -125,10 +129,11 @@ const MaterialTreeNode: FC<{
     tag:            MaterialSidebarTag
 }> = ({ materialFilter, nestLevel = 0, onChildren, openTags, selectedTagId,
 	 setOpenTags, tag }) => {
+  const locale = useLocale ()
   const open = Boolean (openTags[tag.id])
   const { data } = useQuery ({
-      queryKey: materialsKeys.tree ({ parentId: tag.id, materialFilter }),
+      queryKey: materialsKeys.tree ({ parentId: tag.id, materialFilter }, locale),
-      queryFn:	() => fetchMaterialTagTree ({ parentId: tag.id, materialFilter }),
+      queryFn:	() => fetchMaterialTagTree ({ parentId: tag.id, materialFilter }, locale),
       enabled:	open && tag.hasChildren && tag.children.length === 0})
 
   useEffect (() => {
@@ -200,6 +205,7 @@ const MobileMaterialTreeNode: FC<{ depth?: number
       tag,
     },
 ) => {
+  const locale = useLocale ()
   const open = Boolean (openTags[tag.id])
   const tagColumnRef = useRef<HTMLDivElement | null> (null)
   const chipRef = useRef<HTMLDivElement | null> (null)
@@ -210,8 +216,8 @@ const MobileMaterialTreeNode: FC<{ depth?: number
   const [tagLinkInlineSizePx, setTagLinkInlineSizePx] = useState<number | null> (null)
   const [childAvailableInlineSizePx, setChildAvailableInlineSizePx] = useState<number | null> (null)
   const { data } = useQuery ({
-      queryKey: materialsKeys.tree ({ parentId: tag.id, materialFilter }),
+      queryKey: materialsKeys.tree ({ parentId: tag.id, materialFilter }, locale),
-      queryFn:  () => fetchMaterialTagTree ({ parentId: tag.id, materialFilter }),
+      queryFn:  () => fetchMaterialTagTree ({ parentId: tag.id, materialFilter }, locale),
       enabled:  open && tag.hasChildren && tag.children.length === 0})
 
   useEffect (() => {
@@ -382,8 +388,10 @@ const MobileMaterialTreeNode: FC<{ depth?: number
 
 
 const MaterialSidebar: FC = () => {
+  const { label } = useUITranslation ('materials')
+  const locale = useLocale ()
   const location = useLocation ()
-  const navigate = useNavigate ()
+  const navigate = useLocaleNavigate ()
   const qs = new URLSearchParams (location.search)
   const materialFilter = parseMaterialFilter (qs.get ('material_filter'), 'any')
   const selectedTagId = Number (qs.get ('tag_id') ?? 0) || null
@@ -395,8 +403,8 @@ const MaterialSidebar: FC = () => {
       useState<number | null> (null)
 
   const { data: rootTags = [], isLoading, isError } = useQuery ({
-      queryKey: materialsKeys.tree ({ parentId: null, materialFilter }),
+      queryKey: materialsKeys.tree ({ parentId: null, materialFilter }, locale),
-      queryFn:  () => fetchMaterialTagTree ({ parentId: null, materialFilter })})
+      queryFn:  () => fetchMaterialTagTree ({ parentId: null, materialFilter }, locale)})
 
   useEffect (() => {
     setDesktopTags (rootTags)
@@ -494,10 +502,12 @@ const MaterialSidebar: FC = () => {
 		materialFilter={materialFilter}
 		onChange={handleFilterChange}/>
 	    {isLoading && (
-		<p className="text-sm text-neutral-500 dark:text-stone-400">読込中……</p>)}
+		<p className="text-sm text-neutral-500 dark:text-stone-400">
+		  {label ('shared:messages.loadingEllipsis')}
+		</p>)}
 	    {isError && (
 		<p className="text-sm text-red-600 dark:text-red-300">
-		  タグ一覧の取得に失敗しました．
+		  {label ('sidebar.error')}
 		</p>)}
 	    {(!isLoading && !isError) && (
 		<ul>

frontend/src/components/MenuSeparator.tsx

@@ -3,8 +3,8 @@ import type { FC } from 'react'
 
 const MenuSeparator: FC = () => (
     <>
-      <span className="hidden md:inline flex items-center px-2">|</span>
+      <span className="top-nav-separator-vertical items-center px-2">|</span>
-      <hr className="block md:hidden w-full opacity-25
+      <hr className="top-nav-separator-horizontal w-full opacity-25
 		     border-t border-black dark:border-white"/>
     </>)
 

frontend/src/components/PostEditForm.test.tsx

@@ -1,8 +1,10 @@
-import { fireEvent, render, screen, waitFor } from '@testing-library/react'
+import { fireEvent, screen, waitFor } from '@testing-library/react'
 import { describe, expect, it, vi } from 'vitest'
 
+import { textContentOf } from '@/test/text'
 import PostEditForm from '@/components/PostEditForm'
 import { buildPost, buildTag } from '@/test/factories'
+import { renderWithProviders as render } from '@/test/render'
 
 const postsApi = vi.hoisted (() => ({
   updatePost: vi.fn (),
@@ -19,7 +21,8 @@ const toastApi = vi.hoisted (() => ({
 vi.mock ('@/lib/posts', () => postsApi)
 vi.mock ('@/lib/api', () => api)
 vi.mock ('@/components/ui/use-toast', () => toastApi)
-vi.mock ('@/lib/dialogues/useDialogue', () => ({
+vi.mock ('@/lib/dialogues/useDialogue', async importOriginal => ({
+  ...await importOriginal<typeof import ('@/lib/dialogues/useDialogue')> (),
   default: () => ({
     choice: vi.fn (),
   }),
@@ -60,11 +63,12 @@ describe ('PostEditForm', () => {
             parentPostIds: '3 4',
             tags:          'general-tag',
           }),
-          { baseVersionNo: 4 },
+          { baseVersionNo: 4 }, 'ja',
       )
     })
     expect (onSave).toHaveBeenCalledWith (expect.objectContaining ({ versionNo: 5 }))
-    expect (toastApi.toast).toHaveBeenCalledWith ({ description: '更新しました．' })
+    expect (toastApi.toast).toHaveBeenCalledTimes (1)
+    expect (textContentOf (toastApi.toast.mock.calls[0][0].description)).toBe ('更新しました．')
   })
 
   it ('preserves duration while the video tag is temporarily removed', () => {
@@ -78,7 +82,7 @@ describe ('PostEditForm', () => {
 
     render (<PostEditForm post={post} onSave={vi.fn ()}/>)
 
-    expect (screen.getByText ('動画時間').parentElement?.querySelector ('input'))
+    expect (screen.getByDisplayValue ('180.5'))
 	.toHaveValue ('180.5')
 
     const tags = screen.getAllByRole ('textbox')[2]
@@ -88,7 +92,7 @@ describe ('PostEditForm', () => {
     fireEvent.change (tags, {
       target: { value: '動画 general-tag' },
     })
-    expect (screen.getByText ('動画時間').parentElement?.querySelector ('input'))
+    expect (screen.getByDisplayValue ('180.5'))
 	.toHaveValue ('180.5')
   })
 

frontend/src/components/PostEditForm.tsx

@@ -1,5 +1,6 @@
 import { useEffect, useMemo, useState } from 'react'
 
+import { useLocale } from '@/lib/useLocale'
 import PostOriginalCreatedTimeField from '@/components/PostOriginalCreatedTimeField'
 import FieldError from '@/components/common/FieldError'
 import PostDurationField from '@/components/posts/PostDurationField'
@@ -12,6 +13,7 @@ import useDialogue from '@/lib/dialogues/useDialogue'
 import { updatePost } from '@/lib/posts'
 import { msToTime } from '@/lib/utils'
 import { useValidationErrors } from '@/lib/useValidationErrors'
+import { useUITranslation } from '@/lib/useUITranslation'
 
 import type { FC, FormEvent } from 'react'
 
@@ -51,6 +53,8 @@ type Props = { post:    Post
 
 
 const PostEditForm: FC<Props> = ({ post, onSave }) => {
+  const locale = useLocale ()
+  const { label } = useUITranslation ('posts')
   const [disabled, setDisabled] = useState (false)
   const [duration, setDuration] = useState<string> (videoMsToDurationValue (post.videoMs))
   const { baseErrors, fieldErrors, clearValidationErrors, applyValidationError } =
@@ -61,7 +65,7 @@ const PostEditForm: FC<Props> = ({ post, onSave }) => {
       useState<string | null> (post.originalCreatedFrom)
   const [parentPostIds, setParentPostIds] =
       useState ((post.parentPosts ?? []).map (p => p.id).join (' '))
-  const [tags, setTags] = useState<string> ('')
+  const [tags, setTags] = useState<string> (() => tagsToStr (post.tags))
   const [title, setTitle] = useState (post.title)
 
   const videoFlg =
@@ -70,12 +74,15 @@ const PostEditForm: FC<Props> = ({ post, onSave }) => {
 
   const dialogue = useDialogue ()
 
-  const update = async (...args: Parameters<typeof updatePost>) => {
+  const update = async (
+      postData: Parameters<typeof updatePost>[0],
+      options: Parameters<typeof updatePost>[1],
+  ) => {
     clearValidationErrors ()
 
     try
     {
-      const data = await updatePost (...args)
+      const data = await updatePost (postData, options, locale)
       onSave ({ ...post,
 		versionNo:              data.versionNo,
 		title:                  data.title,
@@ -86,7 +93,7 @@ const PostEditForm: FC<Props> = ({ post, onSave }) => {
 		siblingPosts:           data.siblingPosts,
 		originalCreatedFrom:    data.originalCreatedFrom,
 		originalCreatedBefore:  data.originalCreatedBefore } as Post)
-      toast ({ description: '更新しました．' })
+      toast ({ description: label ('shared:messages.updated') })
     }
     catch (e)
     {
@@ -96,24 +103,28 @@ const PostEditForm: FC<Props> = ({ post, onSave }) => {
 	{
 	  if (applyValidationError (e))
 	    {
-	      toast ({ description: '更新はできなかったよ……' })
+	      toast ({ description: label ('edit.validationFailed') })
 	      return
 	    }
 
-	  toast ({ title: '失敗……', description: '入力を確認してください．' })
+	  toast ({ title: label ('shared:messages.failed'),
+	      description: label ('shared:messages.checkInput') })
 
 	  return
 	}
 
       const action = await dialogue.choice ({
-	  title: '競合が発生しました．',
+	  title: label ('edit.conflictTitle'),
 	  description: (
 	      <div>
-		<p>ほかの耕作員が先に更新してゐます．</p>
+		<p>{label ('edit.conflictDescription')}</p>
-		<p>現在の変更をどう扱ひますか?</p>
+		<p>{label ('edit.conflictQuestion')}</p>
 	      </div>),
-	  choices: [...(response?.data?.mergeable ? [{ value: 'merge', label: '差分をマージ' }] : []),
+	  cancelText: label ('shared:actions.cancel'),
-		    { value: 'overwrite', label: '強制上書き', variant: 'danger' }] })
+	  closeLabel: label ('settings:actions.close'),
+	  choices: [...(response?.data?.mergeable
+	      ? [{ value: 'merge', label: label ('edit.merge') }] : []),
+	      { value: 'overwrite', label: label ('edit.overwrite'), variant: 'danger' }] })
 
       if (action === 'merge')
 	{
@@ -163,13 +174,13 @@ const PostEditForm: FC<Props> = ({ post, onSave }) => {
 	<FieldError messages={baseErrors}/>
 
 	<PostTextField
-	    label="タイトル"
+	    label={label ('shared:labels.title')}
 	    value={title ?? ''}
 	    disabled={disabled}
 	    onChange={setTitle}/>
 
 	<PostTextField
-	    label="親投稿"
+	    label={label ('shared:labels.parentPosts')}
 	    value={parentPostIds}
 	    disabled={disabled}
 	    errors={fieldErrors.parentPostIds}
@@ -202,7 +213,7 @@ const PostEditForm: FC<Props> = ({ post, onSave }) => {
 
 	{/* 送信 */}
 	<Button type="submit" disabled={disabled}>
-	  更新
+	  {label ('shared:actions.update')}
 	</Button>
       </form>)
 }

frontend/src/components/PostEmbed.test.tsx

@@ -1,8 +1,9 @@
-import { fireEvent, render, screen, waitFor } from '@testing-library/react'
+import { fireEvent, screen, waitFor } from '@testing-library/react'
 import { beforeEach, describe, expect, it, vi } from 'vitest'
 
 import PostEmbed from '@/components/PostEmbed'
 import { buildPost } from '@/test/factories'
+import { renderWithProviders as render } from '@/test/render'
 
 const dialogue = vi.hoisted (() => ({
   confirm: vi.fn (),
@@ -12,8 +13,9 @@ const nicoViewer = vi.hoisted (() => ({
   props: vi.fn (),
 }))
 
-vi.mock ('@/components/dialogues/DialogueProvider', () => ({
+vi.mock ('@/lib/dialogues/useDialogue', async importOriginal => ({
-  useDialogue: () => dialogue,
+  ...await importOriginal<typeof import ('@/lib/dialogues/useDialogue')> (),
+  default: () => dialogue,
 }))
 
 vi.mock ('@/components/NicoViewer', () => ({

frontend/src/components/PostEmbed.tsx

@@ -3,9 +3,10 @@ import YoutubeEmbed from 'react-youtube'
 
 import NicoViewer from '@/components/NicoViewer'
 import TwitterEmbed from '@/components/TwitterEmbed'
-import { useDialogue } from '@/components/dialogues/DialogueProvider'
+import useDialogue from '@/lib/dialogues/useDialogue'
 import { Button } from '@/components/ui/button'
 import { useClientBehaviourSettings } from '@/lib/useClientBehaviourSettings'
+import { useUITranslation } from '@/lib/useUITranslation'
 
 import type { FC, RefObject } from 'react'
 
@@ -36,6 +37,7 @@ const PostEmbed: FC<Props> = (
       onError },
 ) => {
   const dialogue = useDialogue ()
+  const { label } = useUITranslation ('posts')
   const behaviourSettings = useClientBehaviourSettings ()
   const embedAutoLoadMode = behaviourSettings.embedAutoLoad ?? 'auto'
   const [manualLoadRequested, setManualLoadRequested] = useState (false)
@@ -135,7 +137,7 @@ const PostEmbed: FC<Props> = (
 
   const externalLink = (
       <a href={post.url} target="_blank" rel="noreferrer">
-	外部ページを開く
+	{label ('embed.openExternal')}
       </a>)
 
   const manualLoadControl = (
@@ -144,7 +146,7 @@ const PostEmbed: FC<Props> = (
 	    type="button"
 	    variant="outline"
 	    onClick={() => setManualLoadRequested (true)}>
-	  埋め込みを読込
+	  {label ('embed.load')}
 	</Button>
 	{externalLink}
       </div>)
@@ -239,15 +241,15 @@ const PostEmbed: FC<Props> = (
 		e.preventDefault ()
 
 		setFramed (await dialogue.confirm ({
-		    title: '未確認の外部ページを表示します。',
+		    title: label ('embed.confirmTitle'),
 		    description: (
 			<div>
-			  <p>悪意のあるスクリプトが実行される可能性があります。</p>
+			  <p>{label ('embed.risk')}</p>
-			  <p>表示しますか?</p>
+			  <p>{label ('embed.question')}</p>
 			</div>),
-		    confirmText: '表示' }))
+		    confirmText: label ('shared:actions.show') }))
 	      }}>
-		外部ページを表示
+		{label ('embed.showExternal')}
 	      </a>)}
 	    </div>)}
       </>)

frontend/src/components/PostFormTagsArea.test.tsx

@@ -26,7 +26,8 @@ describe ('PostFormTagsArea', () => {
     await waitFor (() => {
       expect (api.apiGet).toHaveBeenCalledWith (
           '/tags/autocomplete',
-          { params: { q: '虹', nico: '0' } },
+          { locale: 'ja', params: { q: '虹', nico: '0' },
+	    signal: expect.any (AbortSignal) },
       )
     })
     expect (setTags).toHaveBeenCalledWith ('虹夏')

frontend/src/components/PostFormTagsArea.tsx

@@ -1,13 +1,15 @@
 // TODO: TagSearch と共通化する．
 
-import { useRef, useState } from 'react'
+import { useEffect, useRef, useState } from 'react'
 
+import { useLocale } from '@/lib/useLocale'
+import { useUITranslation } from '@/lib/useUITranslation'
 import TagSearchBox from '@/components/TagSearchBox'
 import FormField from '@/components/common/FormField'
 import TextArea from '@/components/common/TextArea'
 import { apiGet } from '@/lib/api'
 
-import type { ComponentPropsWithoutRef, FC, SyntheticEvent } from 'react'
+import type { ComponentPropsWithoutRef, FC, ReactNode, SyntheticEvent } from 'react'
 
 import type { Tag } from '@/types'
 
@@ -34,19 +36,29 @@ const replaceToken = (value: string, start: number, end: number, text: string) =
 type Props = Omit<ComponentPropsWithoutRef<'textarea'>, 'value' | 'onChange' | 'onBlur'> & {
     tags:     string
     setTags:  (tags: string) => void
-    errors?:  string[] }
+    errors?:  ReactNode[] }
 
 
 const PostFormTagsArea: FC<Props> = ({ tags, setTags, errors, ...rest }) => {
+  const { label } = useUITranslation ('navigation')
+  const locale = useLocale ()
   const ref = useRef<HTMLTextAreaElement> (null)
 
   const [bounds, setBounds] = useState<{ start: number; end: number }> ({ start: 0, end: 0 })
   const [focused, setFocused] = useState (false)
-  const [suggestions, setSuggestions] = useState<Tag[]> ([])
+  const [request, setRequest] = useState ({ query: '' })
+  const [result, setResult] = useState<{
+      locale: string
+      request: { query: string }
+      tags: Tag[] }> ({ locale, request, tags: [] })
+  const currentToken = getTokenAt (tags, Math.min (bounds.start, tags.length)).token
+  const suggestions = (result.locale === locale && result.request === request
+      && request.query === currentToken) ? result.tags : []
   const [suggestionsVsbl, setSuggestionsVsbl] = useState (false)
 
   const handleTagSelect = (tag: Tag) => {
     setSuggestionsVsbl (false)
+    setRequest ({ query: '' })
     const textarea = ref.current!
     const newValue = replaceToken (tags, bounds.start, bounds.end, tag.name + ' ')
     setTags (newValue)
@@ -58,8 +70,10 @@ const PostFormTagsArea: FC<Props> = ({ tags, setTags, errors, ...rest }) => {
     })
   }
 
-  const recompute = async (pos: number, v: string = tags) => {
+  const recompute = (pos: number, v: string = tags) => {
     const { start, end, token } = getTokenAt (v, pos)
+    setRequest ({ query: token })
+    setSuggestionsVsbl (token.trim () !== '')
     if (!(token.trim ()))
       {
 	setSuggestionsVsbl (false)
@@ -67,17 +81,43 @@ const PostFormTagsArea: FC<Props> = ({ tags, setTags, errors, ...rest }) => {
       }
 
     setBounds ({ start, end })
-
-    const data = await apiGet<Tag[]> ('/tags/autocomplete', { params: {
-	q: token,
-	nico: '0' } })
-    const nextSuggestions = data.filter (t => t.postCount > 0)
-    setSuggestions (nextSuggestions)
-    setSuggestionsVsbl (nextSuggestions.length > 0)
   }
 
+  useEffect (() => {
+    if (request.query.trim () === '')
+      return
+    const controller = new AbortController ()
+    let active = true
+    void (async () => {
+      try
+      {
+	const tags = await apiGet<Tag[]> ('/tags/autocomplete', {
+	    locale, signal: controller.signal, params: { q: request.query, nico: '0' } })
+	if (active)
+	{
+	  setResult ({ locale, request,
+	      tags: tags.filter (tag => tag.postCount > 0) })
+	}
+      }
+      catch
+      {
+	if (active)
+	  setResult ({ locale, request, tags: [] })
+      }
+    }) ()
+    return () => {
+      active = false
+      controller.abort ()
+    }
+  }, [request, locale])
+
+  useEffect (() => {
+    setSuggestionsVsbl (false)
+    setRequest ({ query: '' })
+  }, [locale])
+
   return (
-      <FormField className="relative w-full" label="タグ" messages={errors}>
+      <FormField className="relative w-full" label={label ('tags')} messages={errors}>
 	{({ describedBy, invalid }) => (
 	    <>
 	      <TextArea
@@ -89,7 +129,7 @@ const PostFormTagsArea: FC<Props> = ({ tags, setTags, errors, ...rest }) => {
 		  onChange={ev => setTags (ev.target.value)}
 		  onSelect={async (ev: SyntheticEvent<HTMLTextAreaElement>) => {
 		    const pos = (ev.target as HTMLTextAreaElement).selectionStart
-		    await recompute (pos)
+		    await recompute (pos, (ev.target as HTMLTextAreaElement).value)
 		  }}
 		  onFocus={() => setFocused (true)}
 		  onBlur={() => {

frontend/src/components/PostList.test.tsx

@@ -26,11 +26,11 @@ describe ('PostList', () => {
 
     expect (screen.getByRole ('link', { name: 'First' })).toHaveAttribute (
         'href',
-        '/posts/1',
+        '/ja/posts/1',
     )
     expect (
         screen.getByRole ('link', { name: 'https://example.com/second' }),
-    ).toHaveAttribute ('href', '/posts/2')
+    ).toHaveAttribute ('href', '/ja/posts/2')
   })
 
   it ('calls the optional click handler', () => {

frontend/src/components/PostList.tsx

@@ -3,6 +3,7 @@ import { useRef } from 'react'
 import { useLocation } from 'react-router-dom'
 
 import PrefetchLink from '@/components/PrefetchLink'
+import { useUITranslation } from '@/lib/useUITranslation'
 import { useClientBehaviourSettings } from '@/lib/useClientBehaviourSettings'
 import { cn } from '@/lib/utils'
 import { useSharedTransitionStore } from '@/stores/sharedTransitionStore'
@@ -16,6 +17,7 @@ type Props = { posts:     Post[]
 
 
 const PostList: FC<Props> = ({ posts, onClick }) => {
+  const { label } = useUITranslation ('shared')
   const location = useLocation ()
   const behaviourSettings = useClientBehaviourSettings ()
   const thumbnailMode = behaviourSettings.thumbnailMode ?? 'normal'
@@ -75,7 +77,7 @@ const PostList: FC<Props> = ({ posts, onClick }) => {
 		   ? (
 		      <div className="flex h-full w-full items-center justify-center
 				      bg-muted text-center text-xs text-muted-foreground">
-			サムネイルなし
+			{label ('labels.noThumbnail')}
 		      </div>)
 		   : (
 		      <img

frontend/src/components/PostOriginalCreatedTimeField.test.tsx

@@ -1,7 +1,8 @@
-import { fireEvent, render, screen } from '@testing-library/react'
+import { fireEvent, screen } from '@testing-library/react'
 import { describe, expect, it, vi } from 'vitest'
 
 import PostOriginalCreatedTimeField from '@/components/PostOriginalCreatedTimeField'
+import { renderWithProviders as render } from '@/test/render'
 
 describe ('PostOriginalCreatedTimeField', () => {
   it ('updates from and before values', () => {

frontend/src/components/PostOriginalCreatedTimeField.tsx

@@ -1,8 +1,9 @@
 import DateTimeField, { toMinutePrecisionIsoUtc } from '@/components/common/DateTimeField'
 import FormField from '@/components/common/FormField'
 import { Button } from '@/components/ui/button'
+import { useUITranslation } from '@/lib/useUITranslation'
 
-import type { FC } from 'react'
+import type { FC, ReactNode } from 'react'
 
 type Props = {
     disabled?:                boolean
@@ -10,7 +11,7 @@ type Props = {
     setOriginalCreatedFrom:   (x: string | null) => void
     originalCreatedBefore:    string | null
     setOriginalCreatedBefore: (x: string | null) => void
-    errors?:                  string[] }
+    errors?:                  ReactNode[] }
 
 
 const PostOriginalCreatedTimeField: FC<Props> = (
@@ -19,71 +20,71 @@ const PostOriginalCreatedTimeField: FC<Props> = (
       setOriginalCreatedFrom,
       originalCreatedBefore,
       setOriginalCreatedBefore,
-      errors }: Props) => {
+      errors }: Props,
+) => {
+  const { label } = useUITranslation ('shared')
   return (
-      <FormField label="オリジナルの作成日時" messages={errors}>
+      <FormField label={label ('labels.originalCreatedAt')} messages={errors}>
 	  {({ describedBy, invalid }) => (
 	      <>
-		<div className="my-1 flex">
+		<div className="my-1 flex min-w-0 flex-wrap items-center gap-2">
-		  <div className="w-80">
+		  <DateTimeField
-		    <DateTimeField
+		      className="min-w-0 max-w-full"
-			className="mr-2"
+		      disabled={disabled ?? false}
-			disabled={disabled ?? false}
+		      aria-describedby={describedBy}
-			aria-describedby={describedBy}
+		      aria-invalid={invalid}
-			aria-invalid={invalid}
+		      invalid={invalid}
-			invalid={invalid}
+		      value={originalCreatedFrom ?? undefined}
-			value={originalCreatedFrom ?? undefined}
+		      onChange={setOriginalCreatedFrom}
-			onChange={setOriginalCreatedFrom}
+		      onBlur={ev => {
-			onBlur={ev => {
+			const v = ev.target.value
-			  const v = ev.target.value
+			if (!(v))
-			  if (!(v))
+			  return
-			    return
 
-			  const d = new Date (v)
+			const d = new Date (v)
-			  if (d.getMinutes () === 0 && d.getHours () === 0)
+			if (d.getMinutes () === 0 && d.getHours () === 0)
-			    d.setDate (d.getDate () + 1)
+			  d.setDate (d.getDate () + 1)
-			  else
+			else
-			    d.setMinutes (d.getMinutes () + 1)
+			  d.setMinutes (d.getMinutes () + 1)
-			  setOriginalCreatedBefore (toMinutePrecisionIsoUtc (d.toISOString ()))
+			setOriginalCreatedBefore (toMinutePrecisionIsoUtc (d.toISOString ()))
-			}}/>
+		      }}/>
-		    以降
+		  <span className="ainu-ui-label shrink-0 whitespace-nowrap">
-		  </div>
+		    {label ('labels.since')}
-		  <div>
+		  </span>
-		    <Button
+		  <Button
-			type="button"
+		      type="button"
-			className="bg-gray-600 text-white rounded"
+		      className="ainu-ui-label shrink-0 rounded bg-gray-600 text-white
-			disabled={disabled}
+				 dark:bg-gray-600 dark:text-white"
-			onClick={() => {
+		      disabled={disabled}
-			  setOriginalCreatedFrom (null)
+		      onClick={() => {
-			}}>
+			setOriginalCreatedFrom (null)
-		      リセット
+		      }}>
-		    </Button>
+		    {label ('actions.reset')}
-		  </div>
+		  </Button>
 		</div>
 
-		<div className="my-1 flex">
+		<div className="my-1 flex min-w-0 flex-wrap items-center gap-2">
-		  <div className="w-80">
+		  <DateTimeField
-		    <DateTimeField
+		      className="min-w-0 max-w-full"
-			className="mr-2"
+		      disabled={disabled}
-			disabled={disabled}
+		      aria-describedby={describedBy}
-			aria-describedby={describedBy}
+		      aria-invalid={invalid}
-			aria-invalid={invalid}
+		      invalid={invalid}
-			invalid={invalid}
+		      value={originalCreatedBefore ?? undefined}
-			value={originalCreatedBefore ?? undefined}
+		      onChange={setOriginalCreatedBefore}/>
-			onChange={setOriginalCreatedBefore}/>
+		  <span className="ainu-ui-label shrink-0 whitespace-nowrap">
-		    より前
+		    {label ('labels.before')}
-		  </div>
+		  </span>
-		  <div>
+		  <Button
-		    <Button
+		      type="button"
-			type="button"
+		      className="ainu-ui-label shrink-0 rounded bg-gray-600 text-white
-			className="bg-gray-600 text-white rounded"
+				 dark:bg-gray-600 dark:text-white"
-			disabled={disabled}
+		      disabled={disabled}
-			onClick={() => {
+		      onClick={() => {
-			  setOriginalCreatedBefore (null)
+			setOriginalCreatedBefore (null)
-			}}>
+		      }}>
-		      リセット
+		    {label ('actions.reset')}
-		    </Button>
+		  </Button>
-		  </div>
 		</div>
 	      </>)}
       </FormField>)

frontend/src/components/PrefetchLink.tsx

@@ -1,12 +1,15 @@
 import { useQueryClient } from '@tanstack/react-query'
 import { forwardRef, useMemo } from 'react'
 import { flushSync } from 'react-dom'
-import { createPath, useNavigate } from 'react-router-dom'
+import { createPath } from 'react-router-dom'
 
+import { localiseTo } from '@/lib/locales'
+import { useLocale, useLocaleNavigate } from '@/lib/useLocale'
 import { useOverlayStore } from '@/components/RouteBlockerOverlay'
 import { prefetchForURL } from '@/lib/prefetchers'
 import { useClientBehaviourSettings } from '@/lib/useClientBehaviourSettings'
 import { cn } from '@/lib/utils'
+import { currentRenderContext } from '@/lib/renderContext'
 
 import type { AnchorHTMLAttributes, MouseEvent, TouchEvent } from 'react'
 import type { To } from 'react-router-dom'
@@ -32,16 +35,20 @@ export default forwardRef<HTMLAnchorElement, Props> (({
   if ('onClick' in rest)
     delete rest['onClick']
 
-  const navigate = useNavigate ()
+  const navigate = useLocaleNavigate ()
+  const locale = useLocale ()
   const qc = useQueryClient ()
   const behaviourSettings = useClientBehaviourSettings ()
   const linkPreloadMode = behaviourSettings.linkPreload ?? 'intent'
   const path = useMemo (
-      () => typeof to === 'string' ? to : createPath (to),
+      () => {
-      [to],
+	const localised = localiseTo (to, locale)
+	return typeof localised === 'string' ? localised : createPath (localised)
+      },
+      [to, locale],
   )
   const url = useMemo (() => {
-    return (new URL (path, window.location.origin)).toString ()
+    return (new URL (path, currentRenderContext ()?.origin ?? 'http://localhost')).toString ()
   }, [path])
   const setOverlay = useOverlayStore (s => s.setActive)
 
@@ -98,7 +105,7 @@ export default forwardRef<HTMLAnchorElement, Props> (({
       if (!(ok) && cancelOnError)
 	return
 
-      navigate (to, { replace, ...(state && { state }) })
+      navigate (path, { replace, ...(state && { state }) })
     }
     catch (ex)
     {

frontend/src/components/RouteBlockerOverlay.tsx

@@ -1,6 +1,10 @@
 import { useEffect } from 'react'
+import { useTranslation } from 'react-i18next'
 import { create } from 'zustand'
 
+import LocalisedText from '@/components/LocalisedText'
+import { translateUIMessage } from '@/lib/i18n'
+
 import type { FC } from 'react'
 
 type OverlayStore = {
@@ -14,6 +18,9 @@ export const useOverlayStore = create<OverlayStore> (set => ({
 
 
 const RouteBlockerOverlay: FC = () => {
+  const { i18n } = useTranslation ('common')
+  const loading = translateUIMessage ('loading', 'common', i18n.language)
+  const loadingLabel = translateUIMessage ('loadingLabel', 'common', i18n.language)
   const active = useOverlayStore (s => s.active)
 
   useEffect (() => {
@@ -35,11 +42,12 @@ const RouteBlockerOverlay: FC = () => {
   return (
       <div
 	  role="progressbar"
-	  aria-label="Loading"
+	  aria-label={loadingLabel.text}
+	  lang={loadingLabel.language}
 	  className="fixed inset-0 z-[9999] bg-black/50 backdrop-blur-sm pointer-events-auto">
 	<div className="absolute inset-0 flex items-center justify-center">
 	  <div className="rounded-2xl bg-black/60 text-white px-6 py-3 text-sm">
-	    Loading...
+	    <LocalisedText language={loading.language}>{loading.text}</LocalisedText>
 	  </div>
 	</div>
       </div>)

frontend/src/components/SortHeader.test.tsx

@@ -17,7 +17,7 @@ describe ('SortHeader', () => {
 
     expect (screen.getByRole ('link', { name: 'タイトル ▲' })).toHaveAttribute (
         'href',
-        '/posts?tags=x&page=1&order=title%3Adesc',
+        '/ja/posts?tags=x&page=1&order=title%3Adesc',
     )
   })
 
@@ -33,7 +33,7 @@ describe ('SortHeader', () => {
 
     expect (screen.getByRole ('link', { name: '更新' })).toHaveAttribute (
         'href',
-        '/posts?page=1&order=updated_at%3Adesc',
+        '/ja/posts?page=1&order=updated_at%3Adesc',
     )
   })
 })

frontend/src/components/SortHeader.tsx

@@ -2,10 +2,12 @@ import { useLocation } from 'react-router-dom'
 
 import PrefetchLink from '@/components/PrefetchLink'
 
+import type { ReactNode } from 'react'
+
 
 export default <T extends string,>({ by, label, currentOrder, defaultDirection }: {
     by:               T
-    label:            string
+    label:            ReactNode
     currentOrder:     `${ T }:${ 'asc' | 'desc' }`
     defaultDirection: Record<T, 'asc' | 'desc'> }) => {
   const [fld, dir] = currentOrder.split (':')
@@ -23,9 +25,9 @@ export default <T extends string,>({ by, label, currentOrder, defaultDirection }
       <PrefetchLink
 	  className="text-inherit visited:text-inherit hover:text-inherit"
 	  to={`${ location.pathname }?${ qs.toString () }`}>
-	<span className="font-bold">
+	<span className="inline-flex w-max items-baseline gap-1 whitespace-nowrap font-bold">
 	  {label}
-	  {by === fld && (dir === 'asc' ? ' ▲' : ' ▼')}
+	  {by === fld && <span className="shrink-0">{dir === 'asc' ? '▲' : '▼'}</span>}
 	</span>
       </PrefetchLink>)
 }

frontend/src/components/TagDetailSidebar.tsx

@@ -12,6 +12,7 @@ import { useQueryClient } from '@tanstack/react-query'
 import { motion } from 'framer-motion'
 import { useEffect, useMemo, useRef, useState } from 'react'
 
+import { useLocale } from '@/lib/useLocale'
 import DraggableDroppableTagRow from '@/components/DraggableDroppableTagRow'
 import PrefetchLink from '@/components/PrefetchLink'
 import TagLink from '@/components/TagLink'
@@ -25,8 +26,11 @@ import { apiDelete, apiGet, apiPatch, apiPost } from '@/lib/api'
 import { clientAnimationTransition } from '@/lib/clientAnimation'
 import { postsKeys, tagsKeys } from '@/lib/queryKeys'
 import { useClientBehaviourSettings } from '@/lib/useClientBehaviourSettings'
-import { dateString, originalCreatedAtString } from '@/lib/utils'
+import { localisedDateString, originalCreatedAtString } from '@/lib/utils'
+import LocalisedText from '@/components/LocalisedText'
+import { useUITranslation } from '@/lib/useUITranslation'
 
+import type { LocaleCode } from '@/lib/locales'
 import type { CollisionDetection, DragEndEvent } from '@dnd-kit/core'
 import type { FC, MutableRefObject, ReactNode } from 'react'
 
@@ -180,8 +184,10 @@ const buildFlatTagByCategory = (
 
 const changeCategory = async (
     tagId:    number,
-    category: Category): Promise<void> => {
+    category: Category,
-  await apiPatch (`/tags/${ tagId }`, { category })
+    locale: LocaleCode = 'ja',
+): Promise<void> => {
+  await apiPatch (`/tags/${ tagId }`, { category }, { locale })
 }
 
 
@@ -227,6 +233,8 @@ type ActiveTagDrag = {
 
 
 const TagDetailSidebar: FC<Props> = ({ className, post, sp }) => {
+  const locale = useLocale ()
+  const { label } = useUITranslation ('tags')
   sp = Boolean (sp)
 
   const qc = useQueryClient ()
@@ -271,7 +279,7 @@ const TagDetailSidebar: FC<Props> = ({ className, post, sp }) => {
       useSensor (TouchSensor, { activationConstraint: { delay: 250, tolerance: 8 } }))
 
   const reloadTags = async (): Promise<void> => {
-    setTags (buildTagByCategory (await apiGet<Post> (`/posts/${ post.id }`)))
+    setTags (buildTagByCategory (await apiGet<Post> (`/posts/${ post.id }`, { locale })))
     qc.invalidateQueries ({ queryKey: postsKeys.root })
     qc.invalidateQueries ({ queryKey: tagsKeys.root })
   }
@@ -314,14 +322,15 @@ const TagDetailSidebar: FC<Props> = ({ className, post, sp }) => {
 	    return
 
 	  if (fromParentId != null)
-	    await apiDelete (`/tags/${ fromParentId }/children/${ childId }`)
+	    await apiDelete (`/tags/${ fromParentId }/children/${ childId }`, { locale })
 
-	  await apiPost (`/tags/${ parentId }/children/${ childId }`, { })
+	  await apiPost (`/tags/${ parentId }/children/${ childId }`, { }, { locale })
 
 	  await reloadTags ()
 	  toast ({
-	      title: '上位タグ対応追加',
+	      title: label ('relations.added'),
-	      description: `《${ child?.name }》を《${ parent?.name }》の子タグに設定しました．` })
+	      description: label ('relations.addedDescription', {
+		  child: child.name, parent: parent.name }) })
 
 	  break
 	}
@@ -333,20 +342,21 @@ const TagDetailSidebar: FC<Props> = ({ className, post, sp }) => {
 	    return
 
 	  if (child.category !== cat)
-	    await changeCategory (childId, cat)
+	    await changeCategory (childId, cat, locale)
 
 	  if (fromParentId != null)
-	    await apiDelete (`/tags/${ fromParentId }/children/${ childId }`)
+	    await apiDelete (`/tags/${ fromParentId }/children/${ childId }`, { locale })
 
 	  const fromParent = fromParentId == null ? null : findTag (tags, fromParentId)
 
 	  await reloadTags ()
 	  toast ({
-	      title: '上位タグ対応解除',
+	      title: label ('relations.removed'),
 	      description: (
 		  fromParent
-		  ? `《${ child.name }》を《${ fromParent.name }》の子タグから外しました．`
+		  ? label ('relations.removedDescription', {
-		  : `《${ child.name }》のカテゴリを変更しました．`) })
+		      child: child.name, parent: fromParent.name })
+		  : label ('relations.categoryChanged', { name: child.name })) })
 
 	  break
 	}
@@ -354,7 +364,8 @@ const TagDetailSidebar: FC<Props> = ({ className, post, sp }) => {
     }
     catch
     {
-      toast ({ title: '上位タグ対応失敗', description: '独裁者である必要があります．' })
+      toast ({ title: label ('relations.failed'),
+	  description: label ('relations.permissionRequired') })
     }
     finally
     {
@@ -468,21 +479,26 @@ const TagDetailSidebar: FC<Props> = ({ className, post, sp }) => {
 		      ? undefined
 		      : `post-info-${ sp }`}
 		  transition={{ layout: layoutTransition }}>
-		<SectionTitle>情報</SectionTitle>
+		<SectionTitle>{label ('shared:labels.information')}</SectionTitle>
 		<ul>
-		  <li>Id.: {post.id}</li>
+		  <li>{label ('shared:idPrefix')}{post.id}</li>
 		  <li>
-		    <>耕作者: </>
+		    {label ('shared:labels.uploadedBy')}
 		    {post.uploadedUser
 		     ? (
 			<PrefetchLink to={`/users/${ post.uploadedUser.id }`}>
-			  {post.uploadedUser.name || '名もなきニジラー'}
+			  {post.uploadedUser.name || label ('shared:labels.anonymous')}
 			</PrefetchLink>)
-		     : 'bot操作'}
+		     : label ('shared:labels.bot')}
 		  </li>
-		  <li>耕作日時: {dateString (post.createdAt)}</li>
 		  <li>
-		    <>リンク: </>
+		    {label ('shared:labels.uploadedAt')}
+		    <LocalisedText language={locale}>
+		      {localisedDateString (post.createdAt, locale)}
+		    </LocalisedText>
+		  </li>
+		  <li>
+		    {label ('shared:labels.link')}
 		    <a
 			className="break-all"
 			href={post.url}
@@ -492,13 +508,15 @@ const TagDetailSidebar: FC<Props> = ({ className, post, sp }) => {
 		    </a>
 		  </li>
 		  <li>
-		    <>オリジナルの投稿日時: </>
+		    {label ('shared:labels.originalPostedAt')}
-		    {originalCreatedAtString (post.originalCreatedFrom,
+		    <LocalisedText language={locale}>
-					      post.originalCreatedBefore)}
+		      {originalCreatedAtString (post.originalCreatedFrom,
+			  post.originalCreatedBefore, locale)}
+		    </LocalisedText>
 		  </li>
 		  <li>
 		    <PrefetchLink to={`/posts/changes?id=${ post.id }`}>
-		      履歴
+		      {label ('navigation:history')}
 		    </PrefetchLink>
 		  </li>
 		</ul>

frontend/src/components/TagLink.test.tsx

@@ -13,7 +13,7 @@ describe ('TagLink', () => {
 
     expect (screen.getByRole ('link', { name: '虹 夏' })).toHaveAttribute (
         'href',
-        '/posts?tags=%E8%99%B9+%E5%A4%8F',
+        '/ja/posts?tags=%E8%99%B9+%E5%A4%8F',
     )
     expect (screen.getByText ('4')).toBeInTheDocument ()
   })
@@ -40,7 +40,7 @@ describe ('TagLink', () => {
 
     expect (screen.getByRole ('link', { name: '?' })).toHaveAttribute (
         'href',
-        '/wiki/a%2Fb',
+        '/ja/wiki/a%2Fb',
     )
   })
 

frontend/src/components/TagLink.tsx

@@ -1,5 +1,6 @@
 import PrefetchLink from '@/components/PrefetchLink'
 import ResponsiveMarqueeText from '@/components/ResponsiveMarqueeText'
+import { useUITranslation } from '@/lib/useUITranslation'
 import { cn } from '@/lib/utils'
 
 import type { ComponentProps, CSSProperties, FC, HTMLAttributes } from 'react'
@@ -67,6 +68,10 @@ const TagLink: FC<Props> = ({ tag,
 			      style,
 			      title,
 			      ...props }) => {
+  const { message } = useUITranslation ()
+  const missingMaterial = message ('tagLink.missingMaterial', { name: tag.name })
+  const missingDeerjikist = message ('tagLink.missingDeerjikist', { name: tag.name })
+  const missingWiki = message ('tagLink.missingWiki', { name: tag.name })
   const colourStyle = {
       '--tag-link-colour': `var(--tag-colour-${ tag.category })`,
       '--tag-link-hover-colour': `var(--tag-colour-${ tag.category }-hover)`,
@@ -121,7 +126,8 @@ const TagLink: FC<Props> = ({ tag,
 			  to={`/materials/new?tag=${ encodeURIComponent (tag.name) }`}
 			  className="animate-[wiki-blink_.25s_steps(2,end)_infinite]
 				     dark:animate-[wiki-blink-dark_.25s_steps(2,end)_infinite]"
-			  title={`${ tag.name } 素材情報が存在しません．`}>
+			  lang={missingMaterial.language}
+			  title={missingMaterial.text}>
 			!
 		      </PrefetchLink>)
 		  : (
@@ -131,7 +137,8 @@ const TagLink: FC<Props> = ({ tag,
 			      to={`/tags/${ tag.id }/deerjikists`}
 			      className="animate-[wiki-blink_.25s_steps(2,end)_infinite]
 					 dark:animate-[wiki-blink-dark_.25s_steps(2,end)_infinite]"
-			      title={`${ tag.name } に関する情報が存在しません．`}>
+			      lang={missingDeerjikist.language}
+			      title={missingDeerjikist.text}>
 			    !
 			  </PrefetchLink>)
 		      : (
@@ -139,7 +146,8 @@ const TagLink: FC<Props> = ({ tag,
 			      to={`/wiki/${ encodeURIComponent (tag.name) }`}
 			      className="animate-[wiki-blink_.25s_steps(2,end)_infinite]
 					 dark:animate-[wiki-blink-dark_.25s_steps(2,end)_infinite]"
-			      title={`${ tag.name } Wiki が存在しません．`}>
+			      lang={missingWiki.language}
+			      title={missingWiki.text}>
 			    !
 			  </PrefetchLink>)))}
 	    </span>)}

frontend/src/components/TagSearch.tsx

@@ -1,8 +1,10 @@
 // TODO: タグ入力系すべてに同様の処理あるため共通化する．
 
 import { useEffect, useState } from 'react'
-import { useNavigate, useLocation } from 'react-router-dom'
+import { useLocation } from 'react-router-dom'
 
+import { useLocale, useLocaleNavigate } from '@/lib/useLocale'
+import { useUITranslation } from '@/lib/useUITranslation'
 import { apiGet } from '@/lib/api'
 import { inputClass } from '@/lib/utils'
 
@@ -14,30 +16,64 @@ import type { Tag } from '@/types'
 
 
 const TagSearch: FC = () => {
+  const { message } = useUITranslation ('shared')
+  const locale = useLocale ()
   const location = useLocation ()
-  const navigate = useNavigate ()
+  const navigate = useLocaleNavigate ()
 
   const [activeIndex, setActiveIndex] = useState (-1)
   const [search, setSearch] = useState ('')
-  const [suggestions, setSuggestions] = useState<Tag[]> ([])
+  const [request, setRequest] = useState ({ query: '' })
+  const [result, setResult] = useState<{
+      locale: string
+      request: { query: string }
+      tags: Tag[] }> ({ locale, request, tags: [] })
+  const suggestions = result.locale === locale && result.request === request
+      ? result.tags : []
   const [suggestionsVsbl, setSuggestionsVsbl] = useState (false)
 
-  const whenChanged = async (ev: ChangeEvent<HTMLInputElement>) => {
+  const whenChanged = (ev: ChangeEvent<HTMLInputElement>) => {
-    setSearch (ev.target.value)
+    const value = ev.target.value
-
+    const query = value.trim ().split (' ').at (-1) ?? ''
-    const q = ev.target.value.trim ().split (' ').at (-1)
+    setSearch (value)
-    if (!(q))
+    setRequest ({ query })
-      {
+    setActiveIndex (-1)
-	setSuggestions ([])
+    setSuggestionsVsbl (query !== '')
-	return
-      }
-
-    const data = await apiGet<Tag[]> ('/tags/autocomplete', { params: { q } })
-    setSuggestions (data.filter (t => t.postCount > 0))
-    if (suggestions.length > 0)
-      setSuggestionsVsbl (true)
   }
 
+  useEffect (() => {
+    if (request.query === '')
+      return
+    const controller = new AbortController ()
+    let active = true
+    void (async () => {
+      try
+      {
+	const tags = await apiGet<Tag[]> ('/tags/autocomplete', {
+	    locale, signal: controller.signal, params: { q: request.query } })
+	if (active)
+	{
+	  setResult ({ locale, request,
+	      tags: tags.filter (tag => tag.postCount > 0) })
+	}
+      }
+      catch
+      {
+	if (active)
+	  setResult ({ locale, request, tags: [] })
+      }
+    }) ()
+    return () => {
+      active = false
+      controller.abort ()
+    }
+  }, [request, locale])
+
+  useEffect (() => {
+    setActiveIndex (-1)
+    setSuggestionsVsbl (false)
+  }, [locale])
+
   const handleKeyDown = (ev: KeyboardEvent<HTMLInputElement>) => {
     switch (ev.key)
     {
@@ -81,6 +117,7 @@ const TagSearch: FC = () => {
 		match }))
 	    .toString () }`)
 	setSuggestionsVsbl (false)
+	setRequest ({ query: '' })
       }
   }
 
@@ -91,7 +128,8 @@ const TagSearch: FC = () => {
 	? ('not:' + tag.name)
 	: tag.name)
     setSearch (parts.join (' ') + ' ')
-    setSuggestions ([])
+    setRequest ({ query: '' })
+    setSuggestionsVsbl (false)
     setActiveIndex (-1)
   }
 
@@ -100,13 +138,16 @@ const TagSearch: FC = () => {
     const anyFlg = query.get ('match') === 'any'
     const tagsQuery = `${ query.get ('tags') ?? '' }${ anyFlg ? ' type:or' : '' }`
     setSearch (tagsQuery)
+    setRequest ({ query: '' })
+    setActiveIndex (-1)
+    setSuggestionsVsbl (false)
   }, [location.search])
 
   return (
       <div className="relative w-full">
 	<input type="text"
 	       data-shortcut-focus-search="true"
-	       placeholder="タグ検索..."
+	       placeholder={message ('labels.tagSearch').text}
 	       value={search}
 	       onChange={whenChanged}
 	       onFocus={() => setSuggestionsVsbl (true)}

frontend/src/components/TagSidebar.tsx

@@ -1,7 +1,9 @@
 import { AnimatePresence, motion } from 'framer-motion'
 import { useEffect, useState } from 'react'
-import { useLocation, useNavigate } from 'react-router-dom'
+import { useLocation } from 'react-router-dom'
 
+import { useLocale, useLocaleNavigate } from '@/lib/useLocale'
+import { useUITranslation } from '@/lib/useUITranslation'
 import TagLink from '@/components/TagLink'
 import TagSearch from '@/components/TagSearch'
 import SectionTitle from '@/components/common/SectionTitle'
@@ -22,7 +24,9 @@ type Props = { posts:     Post[]
 
 
 const TagSidebar: FC<Props> = ({ posts, onClick }) => {
-  const navigate = useNavigate ()
+  const { label } = useUITranslation ('shared')
+  const locale = useLocale ()
+  const navigate = useLocaleNavigate ()
   const behaviourSettings = useClientBehaviourSettings ()
   const animationMode = behaviourSettings.animation ?? 'normal'
   const animationsOff = animationMode === 'off'
@@ -69,7 +73,7 @@ const TagSidebar: FC<Props> = ({ posts, onClick }) => {
 
   const TagBlock = (
       <>
-	<SectionTitle>タグ</SectionTitle>
+	<SectionTitle>{label ('navigation:tags')}</SectionTitle>
 	<ul>
 	  {CATEGORIES.flatMap (cat => cat in tags ? (
 	      tags[cat].map (tag => (
@@ -88,7 +92,7 @@ const TagSidebar: FC<Props> = ({ posts, onClick }) => {
 			 </motion.div>)}
 		  </li>))) : [])}
 	</ul>
-	<SectionTitle>関聯</SectionTitle>
+	<SectionTitle>{label ('labels.relations')}</SectionTitle>
 	<a href="#"
 	   onClick={ev => {
 	     ev.preventDefault ()
@@ -96,7 +100,7 @@ const TagSidebar: FC<Props> = ({ posts, onClick }) => {
 	       try
 	       {
 		 const data = await apiGet<Post> ('/posts/random',
-		     { params: { tags: tagsQuery.split (' ').filter (e => e !== '').join (' '),
+		     { locale, params: { tags: tagsQuery.split (' ').filter (e => e !== '').join (' '),
 				 match: (anyFlg ? 'any' : 'all') } })
 		 navigate (`/posts/${ data.id }`)
 	       }
@@ -106,7 +110,7 @@ const TagSidebar: FC<Props> = ({ posts, onClick }) => {
 	       }
 	     }) ())
 	   }}>
-	  ランダム
+	  {label ('actions.random')}
 	</a>
       </>)
 
@@ -146,7 +150,7 @@ const TagSidebar: FC<Props> = ({ posts, onClick }) => {
 	     ev.preventDefault ()
 	     setTagsVsbl (v => !(v))
 	   }}>
-	  {tagsVsbl ? '▲▲▲ タグ一覧を閉じる ▲▲▲' : '▼▼▼ タグ一覧を表示 ▼▼▼'}
+	  {tagsVsbl ? label ('labels.hideTags') : label ('labels.showTags')}
 	</a>
       </SidebarComponent>)
 }

frontend/src/components/TopNav.tsx

@@ -1,12 +1,22 @@
 import { useQuery } from '@tanstack/react-query'
 import { AnimatePresence, motion } from 'framer-motion'
+import { Globe } from 'lucide-react'
 import { Fragment, useEffect, useLayoutEffect, useRef, useState } from 'react'
 import { useLocation } from 'react-router-dom'
 
+import { useLocale, useLocaleNavigate } from '@/lib/useLocale'
+import LocalisedText, { formatUIString } from '@/components/LocalisedText'
 import Separator from '@/components/MenuSeparator'
 import PrefetchLink from '@/components/PrefetchLink'
 import TopNavUser from '@/components/TopNavUser'
+import TranslatedText from '@/components/TranslatedText'
 import { WikiIdBus } from '@/lib/eventBus/WikiIdBus'
+import { isLocaleCode,
+	 localeFromPath,
+	 switchLocalePath,
+	 unlocalisedPath } from '@/lib/locales'
+import { uiMessage, uiMessageLanguage } from '@/lib/messages'
+import { useUITranslation } from '@/lib/useUITranslation'
 import { materialsKeys, tagsKeys, wikiKeys } from '@/lib/queryKeys'
 import { useClientBehaviourSettings } from '@/lib/useClientBehaviourSettings'
 import { canEditContent } from '@/lib/users'
@@ -17,20 +27,30 @@ import { fetchWikiPage } from '@/lib/wiki'
 
 import type { FC, MouseEvent } from 'react'
 
+import type { AvailableLocale } from '@/lib/locales'
 import type { Material, Menu, MenuVisibleItem, Tag, User } from '@/types'
 
-type Props = { user: User | null }
+type Props = { user: User | null; locales: AvailableLocale[] }
 type NavDensity = 'auto' | 'comfortable' | 'compact'
 
 
 export const menuOutline = (
-    { tag, material, wikiId, user, pathName }: {
+    { tag, material, wikiId, user, pathName: fullPathname }: {
 	tag?: Tag | null
 	material?: Material | null
 	wikiId: number | null
 	user: User | null
 	pathName: string },
 ): Menu => {
+  const pathName = unlocalisedPath (fullPathname)
+  const locale = localeFromPath (fullPathname) ?? 'ja'
+
+  const message = (
+      key: Parameters<typeof uiMessage>[1],
+      values?: Record<string, string | number>,
+  ) => ({ name: uiMessage (locale, key, values),
+	  nameLanguage: uiMessageLanguage (locale, key) })
+
   const postCount = tag?.postCount ?? material?.tag?.postCount ?? 0
   const editable = canEditContent (user)
 
@@ -41,71 +61,75 @@ export const menuOutline = (
 
   const materialFlg = /^\/materials\/\d+/.test (pathName)
 
-  const helpVsbl = /\/help\/((?!changes)[^\/?]+)/.test (pathName)
+  const helpVsbl = /\/help\/((?!changes)[^/?]+)/.test (pathName)
   const helpIdentifier = pathName.split ('/')[2] ?? ''
 
   return [
-      { name: '広場', to: '/posts', subMenu: [
+      { ...message ('posts'), to: '/posts', subMenu: [
-	  { name: '一覧', to: '/posts' },
+	  { ...message ('list'), to: '/posts' },
-	  { name: '検索', to: '/posts/search' },
+	  { ...message ('search'), to: '/posts/search' },
-	  { name: '追加', to: '/posts/new', visible: editable },
+	  { ...message ('add'), to: '/posts/new', visible: editable },
-	  { name: '全体履歴', to: '/posts/changes' },
+	  { ...message ('allHistory'), to: '/posts/changes' },
-	  { name: 'ヘルプ', to: '/wiki/ヘルプ:広場' }] },
+	  { ...message ('help'), to: '/wiki/ヘルプ:広場' }] },
-      { name: 'タグ', to: '/tags', subMenu: [
+      { ...message ('tags'), to: '/tags', subMenu: [
-	  { name: 'マスタ', to: '/tags' },
+	  { ...message ('master'), to: '/tags' },
-	  { name: 'ニコニコ連携', to: '/tags/nico' },
+	  { ...message ('nicoLinks'), to: '/tags/nico' },
-	  { name: '全体履歴', to: '/tags/changes' },
+	  { ...message ('allHistory'), to: '/tags/changes' },
-	  { name: 'ヘルプ', to: '/wiki/ヘルプ:タグ' },
+	  { ...message ('help'), to: '/wiki/ヘルプ:タグ' },
 	  { component: <Separator/>, visible: tagFlg },
-	  { name: `広場 (${ postCount || 0 })`,
+	  { ...message ('postsWithCount', { count: postCount }),
 	    to: `/posts?tags=${ encodeURIComponent (tag?.name ?? '') }`,
 	    visible: tagFlg },
-	  { name: '履歴', to: `/tags/changes?id=${ tag?.id }`,
+	  { ...message ('history'), to: `/tags/changes?id=${ tag?.id }`,
 	    visible: tagFlg && tag?.category !== 'nico' }] },
-      { name: '素材', to: '/materials', visible: true, subMenu: [
+      { ...message ('materials'), to: '/materials', visible: true, subMenu: [
-	  { name: '一覧', to: '/materials' },
+	  { ...message ('list'), to: '/materials' },
-	  { name: '追加', to: '/materials/new', visible: editable },
+	  { ...message ('add'), to: '/materials/new', visible: editable },
-	  { name: '抑止', to: '/materials/suppressions',
+	  { ...message ('suppressions'), to: '/materials/suppressions',
 	    visible: user?.role === 'admin' },
-	  { name: '全体履歴', to: '/materials/changes' },
+	  { ...message ('allHistory'), to: '/materials/changes' },
-	  { name: 'ヘルプ', to: '/wiki/ヘルプ:素材管理' },
+	  { ...message ('help'), to: '/wiki/ヘルプ:素材管理' },
 	  { component: <Separator/>, visible: materialFlg },
-	  { name: `広場 (${ postCount || 0 })`,
+	  { ...message ('postsWithCount', { count: postCount }),
 	    to: `/posts?tags=${ encodeURIComponent (material?.tag?.name ?? '') }`,
 	    visible: materialFlg && Boolean (material?.tag) },
-	  { name: '履歴', to: `/materials/changes?material_id=${ material?.id }`,
+	  { ...message ('history'), to: `/materials/changes?material_id=${ material?.id }`,
 	    visible: materialFlg }] },
-      { name: 'Wiki', to: '/wiki', subMenu: [
+      { ...message ('wiki'), to: '/wiki', subMenu: [
-	  { name: '検索', to: '/wiki' },
+	  { ...message ('search'), to: '/wiki' },
-	  { name: '新規', to: '/wiki/new', visible: editable },
+	  { ...message ('create'), to: '/wiki/new', visible: editable },
-	  { name: '全体履歴', to: '/wiki/changes' },
+	  { ...message ('allHistory'), to: '/wiki/changes' },
-	  { name: 'ヘルプ', to: '/wiki/ヘルプ:Wiki' },
+	  { ...message ('help'), to: '/wiki/ヘルプ:Wiki' },
 	  { component: <Separator/>, visible: wikiPageFlg },
-	  { name: `広場 (${ postCount || 0 })`, to: `/posts?tags=${ wikiTitle }`,
+	  { ...message ('postsWithCount', { count: postCount }), to: `/posts?tags=${ wikiTitle }`,
 	    visible: wikiPageFlg },
-	  { name: '履歴', to: `/wiki/changes?id=${ wikiId }`, visible: wikiPageFlg },
+	  { ...message ('history'), to: `/wiki/changes?id=${ wikiId }`, visible: wikiPageFlg },
-	  { name: '編輯', to: `/wiki/${ wikiId || wikiTitle }/edit`,
+	  { ...message ('edit'), to: `/wiki/${ wikiId || wikiTitle }/edit`,
 	    visible: wikiPageFlg && editable }] },
-      { name: 'ヘルプ', to: '/help/home', base: '/help', subMenu: [
+      { ...message ('help'), to: '/help/home', base: '/help', subMenu: [
-	  { name: '検索', to: '/help' },
+	  { ...message ('search'), to: '/help' },
-	  { name: '全体履歴', to: '/help/changes' },
+	  { ...message ('allHistory'), to: '/help/changes' },
 	  { component: <Separator/>, visible: helpVsbl },
-	  { name: '履歴',
+	  { ...message ('history'),
 	    to: `/help/changes?identifier=${ helpIdentifier }`,
 	    visible: helpVsbl }] },
-      { name: 'おたのしみ', visible: false, subMenu: [
+      { ...message ('entertainment'), visible: false, subMenu: [
-	  { name: '上映会 (β)', to: '/theatres/1' },
+	  { ...message ('theatre'), to: '/theatres/1' },
-	  { name: 'グカネータ (β)', to: '/gekanator' }] },
+	  { ...message ('gekanator'), to: '/gekanator' }] },
-      { name: 'ユーザ', to: '/users/settings', visible: false, subMenu: [
+      { ...message ('users'), to: '/users/settings', visible: false, subMenu: [
-	  { name: '一覧', to: '/users', visible: false },
+	  { ...message ('list'), to: '/users', visible: false },
-	  { name: 'お前', to: `/users/${ user?.id }`, visible: false },
+	  { ...message ('currentUser'), to: `/users/${ user?.id }`, visible: false },
-	  { name: '設定', to: '/users/settings', visible: Boolean (user) }] },
+	  { ...message ('settings'), to: '/users/settings', visible: Boolean (user) }] },
-      { name: '法規', visible: false, subMenu: [
+      { ...message ('legal'), visible: false, subMenu: [
-	  { name: '利用規約', to: '/tos' }] }]
+	  { ...message ('terms'), to: '/tos' }] }]
 }
 
 
-const TopNav: FC<Props> = ({ user }) => {
+const TopNav: FC<Props> = ({ user, locales }) => {
+  const { message, label } = useUITranslation ('shared')
+  const locale = useLocale ()
+  const localeName = locales.find (entry => entry.code === locale)?.name
+  const navigate = useLocaleNavigate ()
   const location = useLocation ()
   const behaviourSettings = useClientBehaviourSettings ()
   const animationMode = behaviourSettings.animation ?? 'normal'
@@ -117,23 +141,35 @@ const TopNav: FC<Props> = ({ user }) => {
   const navRef = useRef<HTMLDivElement | null> (null)
   const layoutRef = useRef<HTMLDivElement | null> (null)
   const barRef = useRef<HTMLElement | null> (null)
+  const submenuContentRef = useRef<HTMLDivElement | null> (null)
+  const highlightTargetRef = useRef (-1)
 
   const measure = (idx: number) => {
     const nav = navRef.current
     const el = itemsRef.current[idx < 0 ? visibleMenu.length : idx]
 
-    if (!(nav) || !(el))
+    if (nav == null || el == null || nav.offsetWidth === 0
-      {
+	|| layoutRef.current?.dataset.desktop !== 'true')
-	setHL ({ left: 0, width: 0, visible: true })
+    {
-	return
+      setHL (current => current.visible
-      }
+	  ? { left: 0, width: 0, visible: false } : current)
+      return
+    }
 
-    const navRect = nav.getBoundingClientRect ()
+    // Layout offsets exclude Framer Motion's temporary projection transforms.
-    const elRect = el.getBoundingClientRect ()
+    let left = 0
-
+    let node: HTMLElement | null = el
-    setHL ({ left:    elRect.left - navRect.left,
+    while (node != null && node !== nav)
-	     width:   elRect.width,
+    {
-	     visible: true })
+      left += node.offsetLeft
+      const parent: Element | null = node.offsetParent
+      node = parent instanceof HTMLElement ? parent : null
+    }
+    const width = node === nav ? el.offsetWidth : 0
+    const visible = width > 0
+    setHL (current =>
+	(current.left === left && current.width === width && current.visible === visible)
+	? current : { left, width, visible })
   }
 
   const [hl, setHL] = useState<{ left: number; width: number; visible: boolean }> ({
@@ -141,62 +177,67 @@ const TopNav: FC<Props> = ({ user }) => {
       width:    0,
       visible:  false })
   const [menuOpen, setMenuOpen] = useState (false)
+  const menuToggleLabel = message (menuOpen ? 'dialogue.close' : 'navigation:menuToggle')
   const [desktop, setDesktop] = useState (false)
   const [density, setDensity] = useState<NavDensity> ('auto')
   const [moreVsbl, setMoreVsbl] = useState (false)
   const [openItemIdx, setOpenItemIdx] = useState (-1)
+  const [submenuHeight, setSubmenuHeight] = useState (0)
   const [wikiId, setWikiId] = useState<number | null> (WikiIdBus.get ())
 
   const wikiIdStr = String (wikiId ?? '')
 
   const { data: wikiPage } = useQuery ({
       enabled: Boolean (wikiIdStr),
-      queryKey: wikiKeys.show (wikiIdStr, { }),
+      queryKey: wikiKeys.show (wikiIdStr, { }, locale),
-      queryFn: () => fetchWikiPage (wikiIdStr, { }) })
+      queryFn: () => fetchWikiPage (wikiIdStr, { }, locale) })
 
-  const tagFlg = /^\/tags\/\d+/.test (location.pathname)
+  const pathname = unlocalisedPath (location.pathname)
-  const materialFlg = /^\/materials\/\d+/.test (location.pathname)
+  const tagFlg = /^\/tags\/\d+/.test (pathname)
+  const materialFlg = /^\/materials\/\d+/.test (pathname)
   const effectiveTitle = (((tagFlg || materialFlg)
-			   ? location.pathname.split ('/')[2]
+			   ? pathname.split ('/')[2]
 			   : wikiPage?.title)
 			  ?? '')
 
   const { data: tag } = useQuery ({
       enabled: Boolean (effectiveTitle),
-      queryKey: tagsKeys.show (effectiveTitle),
+      queryKey: tagsKeys.show (effectiveTitle, locale),
-      queryFn: () => (tagFlg ? fetchTag : fetchTagByName) (effectiveTitle) })
+      queryFn: () => (tagFlg ? fetchTag : fetchTagByName) (effectiveTitle, locale) })
 
   const { data: material } = useQuery ({
       enabled: Boolean (effectiveTitle),
-      queryKey: materialsKeys.show (effectiveTitle),
+      queryKey: materialsKeys.show (effectiveTitle, locale),
-      queryFn: () => fetchMaterial (effectiveTitle) })
+      queryFn: () => fetchMaterial (effectiveTitle, locale) })
 
   const menu = menuOutline ({ tag, material, wikiId, user, pathName: location.pathname })
   const visibleMenu = menu.filter ((item): item is MenuVisibleItem => item.visible ?? true)
+  const menuLabels = visibleMenu.map (item => item.name).join ('\u0000')
   const moreMenu = menu.filter (item =>
       !(item.visible ?? true)
       || item.subMenu.filter (subItem => subItem.visible ?? true).length > 0)
   const activeIdx =
-      visibleMenu.findIndex (item => location.pathname.startsWith (item.base || item.to))
+      visibleMenu.findIndex (item => pathname.startsWith (item.base || item.to))
-  const submenuHeight = moreVsbl ? 40 * moreMenu.length : (activeIdx < 0 ? 0 : 40)
+  highlightTargetRef.current = moreVsbl ? -1 : activeIdx
+  const activeSubmenuId = `submenu-${ menu.indexOf (visibleMenu[activeIdx]) }`
   const topNavTransition =
       animationsOff
       ? { duration: 0 }
-      : reducedAnimations
+      : (reducedAnimations
-	? { duration: .08, ease: 'linear' as const }
+	 ? { duration: .08, ease: 'linear' as const }
-	: { duration: .2, ease: 'easeOut' as const }
+	 : { duration: .2, ease: 'easeOut' as const })
   const opacityTransition =
       animationsOff
       ? { duration: 0 }
-      : reducedAnimations
+      : (reducedAnimations
-	? { duration: .08 }
+	 ? { duration: .08 }
-	: { duration: .12 }
+	 : { duration: .12 })
   const highlightTransitionClass =
       animationsOff
       ? undefined
-      : reducedAnimations
+      : (reducedAnimations
-	? 'transition-[transform,width] duration-75 ease-linear'
+	 ? 'transition-[transform,width] duration-75 ease-linear'
-	: 'transition-[transform,width] duration-200 ease-out'
+	 : 'transition-[transform,width] duration-200 ease-out')
 
   const prevActiveIdxRef = useRef<number> (activeIdx)
 
@@ -215,7 +256,7 @@ const TopNav: FC<Props> = ({ user }) => {
     if (layout == null || bar == null || primary == null)
       return
 
-    const userLink = bar.querySelector<HTMLElement> ('.top-nav-user-desktop')
+    const account = bar.querySelector<HTMLElement> ('.top-nav-account')
     let raf = 0
     let active = true
 
@@ -237,11 +278,16 @@ const TopNav: FC<Props> = ({ user }) => {
 	  {
 	    layout.setAttribute ('data-density', candidate)
 	    const style = getComputedStyle (bar)
-	    const required = primary.getBoundingClientRect ().width
+	    const primaryWidth = Math.max (
-		+ (userLink?.getBoundingClientRect ().width ?? 0)
+		primary.getBoundingClientRect ().width, primary.scrollWidth)
+	    const accountWidth =
+		account == null
+		? 0
+		: Math.max (account.getBoundingClientRect ().width, account.scrollWidth)
+	    const required = primaryWidth + accountWidth
 		+ parseFloat (style.paddingLeft) + parseFloat (style.paddingRight)
-		+ (userLink == null ? 0 : parseFloat (style.columnGap))
+		+ (account == null ? 0 : parseFloat (style.columnGap))
-	    if (required <= bar.clientWidth)
+	    if (Math.ceil (required) <= bar.clientWidth)
 	      return candidate
 	  }
 	  return null
@@ -269,8 +315,11 @@ const TopNav: FC<Props> = ({ user }) => {
 	typeof ResizeObserver === 'undefined' ? null : new ResizeObserver (schedule)
     observer?.observe (bar)
     observer?.observe (primary)
-    if (userLink != null)
+    for (const item of itemsRef.current)
-      observer?.observe (userLink)
+      if (item != null)
+	observer?.observe (item)
+    if (account != null)
+      observer?.observe (account)
     update ()
     addEventListener ('resize', schedule)
     document.fonts?.addEventListener ('loadingdone', schedule)
@@ -283,22 +332,74 @@ const TopNav: FC<Props> = ({ user }) => {
       removeEventListener ('resize', schedule)
       document.fonts?.removeEventListener ('loadingdone', schedule)
     }
-  }, [activeIdx, moreVsbl, desktop, density, user?.name])
+  }, [activeIdx, moreVsbl, desktop, density, user?.name, locale, locales, menuLabels])
+
+  useLayoutEffect (() => {
+    measure (moreVsbl ? -1 : activeIdx)
+    if (!(desktop))
+      setMoreVsbl (false)
+  }, [activeIdx, moreVsbl, desktop, density, locale, animationMode, menuLabels])
 
   useEffect (() => {
     const unsubscribe = WikiIdBus.subscribe (setWikiId)
     return () => unsubscribe ()
   }, [])
 
+  useLayoutEffect (() => {
+    const content = submenuContentRef.current
+    if (content == null)
+      return
+
+    const update = () => {
+      setSubmenuHeight (Math.ceil (content.getBoundingClientRect ().height))
+    }
+    const observer =
+	typeof ResizeObserver === 'undefined' ? null : new ResizeObserver (update)
+    observer?.observe (content)
+    update ()
+    addEventListener ('resize', update)
+
+    return () => {
+      observer?.disconnect ()
+      removeEventListener ('resize', update)
+    }
+  }, [activeIdx, moreVsbl, desktop, density, locale])
+
   useEffect (() => {
     setMenuOpen (false)
     setOpenItemIdx (activeIdx)
   }, [activeIdx, location])
 
+  const localeSelector = (
+      <label className="top-nav-menu-link relative flex h-8 shrink-0 items-center gap-1
+			rounded px-1 focus-within:ring-2">
+	<Globe aria-hidden="true" size={16}/>
+	<span className="top-nav-locale-name whitespace-nowrap text-sm">
+	  <LocalisedText language={locale}>{localeName}</LocalisedText>
+	</span>
+	<select
+	    aria-label={formatUIString (localeName ?? '', locale)}
+	    value={locale}
+	    className="absolute inset-0 h-full w-full cursor-pointer opacity-0"
+	    onChange={event => {
+	      const nextLocale = event.target.value
+	      if (isLocaleCode (nextLocale)
+		  && locales.some (entry => entry.code === nextLocale))
+	      {
+		navigate (switchLocalePath (location, nextLocale))
+	      }
+	    }}>
+	  {locales.map (entry => isLocaleCode (entry.code) && (
+	      <option key={entry.code} value={entry.code}>
+		{formatUIString (entry.name, entry.code)}
+	      </option>))}
+	</select>
+      </label>)
+
   return (
       <div ref={layoutRef} className="top-nav-layout w-full min-w-0 shrink-0"
 	  data-desktop={desktop} data-density={density}>
-	<nav ref={barRef}
+	<nav ref={barRef} lang={uiMessageLanguage (locale, 'posts')}
 	    className="top-nav-root top-nav-bar flex justify-between items-center w-full">
 	  <div className="top-nav-primary flex shrink-0 items-center h-12">
 	    <PrefetchLink
@@ -307,7 +408,7 @@ const TopNav: FC<Props> = ({ user }) => {
 		onClick={() => {
 		  scroll (0, 0)
 		}}>
-	      ぼざクリ タグ広場
+	      {label ('labels.brand')}
 	    </PrefetchLink>
 
 	    <div ref={navRef}
@@ -326,7 +427,8 @@ const TopNav: FC<Props> = ({ user }) => {
 		      className="shrink-0 whitespace-nowrap"
 		      {...(animationsOff
 			   ? { }
-			   : { layoutId: `menu-${ item.name }` })}
+			   : { layoutId: `menu-${ menu.indexOf (item) }` })}
+		      onLayoutAnimationComplete={() => measure (highlightTargetRef.current)}
 		      animate={{ opacity: moreVsbl ? 0 : 1 }}
 		      transition={{ opacity: opacityTransition,
 				    layout: topNavTransition }}
@@ -339,7 +441,9 @@ const TopNav: FC<Props> = ({ user }) => {
 			}}
 			className={cn ('top-nav-menu-link relative z-10 flex h-full items-center',
 				       (i === openItemIdx) && 'font-bold')}>
-		      {item.name}
+		      <LocalisedText language={item.nameLanguage ?? 'ja'}>
+			{item.name}
+		      </LocalisedText>
 		    </PrefetchLink>
 		  </motion.div>))}
 	      <PrefetchLink
@@ -355,22 +459,30 @@ const TopNav: FC<Props> = ({ user }) => {
 		  className={cn ('top-nav-menu-link relative z-10 flex h-full items-center',
 				 'shrink-0 whitespace-nowrap',
 				 (openItemIdx < 0 || moreVsbl) && 'font-bold')}>
-		その他 &raquo;
+		<TranslatedText messageKey="more"/>
 	      </PrefetchLink>
 	    </div>
 	  </div>
 
-	  <TopNavUser user={user}/>
+	  <div className="top-nav-account ml-auto flex min-w-0 items-center gap-2">
+	    <TopNavUser user={user}/>
+	    {localeSelector}
+	  </div>
 
-	  <button
+	  <div className="top-nav-mobile-controls ml-auto flex shrink-0 items-center gap-2">
-	     type="button"
+	    {menuOpen && localeSelector}
-	     className="top-nav-mobile-toggle shrink-0 whitespace-nowrap
+	    <button
-			ml-auto border-0 bg-transparent pr-4"
+		type="button"
-	     onClick={() => {
+		className="top-nav-mobile-toggle shrink-0 whitespace-nowrap
-	       setMenuOpen (!(menuOpen))
+			   border-0 bg-transparent pr-4"
-	     }}>
+		aria-label={menuToggleLabel.text}
-	    {menuOpen ? '×' : 'Menu'}
+		lang={menuToggleLabel.language}
-	  </button>
+		onClick={() => {
+		  setMenuOpen (!(menuOpen))
+		}}>
+	      {menuOpen ? '×' : label ('navigation:menuToggle')}
+	    </button>
+	  </div>
 	</nav>
 
 	<AnimatePresence initial={false}>
@@ -387,26 +499,34 @@ const TopNav: FC<Props> = ({ user }) => {
 	      }}
 	      transition={{ layout: topNavTransition }}
 	      onAnimationComplete={() => {
-		measure (moreVsbl ? -1 : activeIdx)
+		measure (highlightTargetRef.current)
+	      }}
+	      onLayoutAnimationComplete={() => {
+		measure (highlightTargetRef.current)
 	      }}>
+	  <div ref={submenuContentRef} className={cn (moreVsbl && 'top-nav-more-menu')}>
 	  {moreVsbl
 	   ? (
 	      moreMenu.map ((item, i) => (
-		  <div key={i} className="relative h-[40px]">
+		  <div key={i} className="contents">
-		    <div className="absolute inset-0 flex items-center px-3
-				    overflow-x-auto whitespace-nowrap">
 		      <motion.div
 			  transition={topNavTransition}
 			  {...(animationsOff
 			       ? { }
 			       : ((item.visible ?? true)
-			       ? { layoutId: `menu-${ item.name }` }
+			       ? { layoutId: `menu-${ menu.indexOf (item) }` }
 			       : { initial: { x: 40, y: -40, opacity: 0 },
 				   animate: { x: 0, y: 0, opacity: 1 },
 				   exit: { x: 40, y: -40, opacity: 0 } }))}
-			  className="z-10 h-full flex shrink-0 items-center px-3 font-bold w-28">
+			  onLayoutAnimationComplete={() => measure (highlightTargetRef.current)}
-			<h2>{item.name}</h2>
+			  className="z-10 min-w-0 px-3 py-2 font-bold">
+			<h2>
+			  <LocalisedText language={item.nameLanguage ?? 'ja'}>
+			    {item.name}
+			  </LocalisedText>
+			</h2>
 		      </motion.div>
+		      <div className="top-nav-more-links flex min-w-0 flex-wrap items-center">
 		      {item.subMenu
 		       .filter (subItem => subItem.visible ?? true)
 		       .map ((subItem, j) => (
@@ -414,12 +534,12 @@ const TopNav: FC<Props> = ({ user }) => {
 			  ? (
 			      <motion.div
 				  key={`c-${ i }-${ j }`}
+				  className="min-w-0 max-w-full"
 				  transition={topNavTransition}
 				  {...(animationsOff
 				       ? { }
-				       : ((visibleMenu[activeIdx]?.name
+				       : ((visibleMenu[activeIdx] === item)
-					=== item.name)
+				       ? { layoutId: `submenu-${ menu.indexOf (item) }-${ j }` }
-				       ? { layoutId: `submenu-${ item.name }-${ j }` }
 				       : { initial: { y: -40, opacity: 0 },
 					   animate: { y: 0, opacity: 1 },
 					   exit: { y: -40, opacity: 0 } }))}>
@@ -428,12 +548,12 @@ const TopNav: FC<Props> = ({ user }) => {
 			  : (
 			      <motion.div
 				  key={`l-${ i }-${ j }`}
+				  className="min-w-0 max-w-full"
 				  transition={topNavTransition}
 				  {...(animationsOff
 				       ? { }
-				       : ((visibleMenu[activeIdx]?.name
+				       : ((visibleMenu[activeIdx] === item)
-					=== item.name)
+				       ? { layoutId: `submenu-${ menu.indexOf (item) }-${ j }` }
-				       ? { layoutId: `submenu-${ item.name }-${ j }` }
 				       : { initial: { y: -40, opacity: 0 },
 					   animate: { y: 0, opacity: 1 },
 					   exit: { y: -40, opacity: 0 } }))}>
@@ -441,49 +561,52 @@ const TopNav: FC<Props> = ({ user }) => {
 				    to={subItem.to}
 				    target={subItem.to.slice (0, 2) === '//' ? '_blank' : undefined}
 				    onClick={() => setMoreVsbl (false)}
-				    className="top-nav-menu-link h-full flex items-center px-3">
+				    className="top-nav-menu-link flex min-h-[40px] items-center px-3 py-2">
-				  {subItem.name}
+				  <LocalisedText language={subItem.nameLanguage ?? 'ja'}>
+				    {subItem.name}
+				  </LocalisedText>
 				</PrefetchLink>
 			      </motion.div>)))}
 		    </div>
 		  </div>)))
 	   : ((visibleMenu[activeIdx]?.subMenu ?? []).length > 0
 	      && (
-		  <div className="relative h-[40px]">
+		  <div className="relative min-h-[40px]">
 		    {animationsOff
 		     ? (
-			 <div className="absolute inset-0 flex items-center px-3
+			 <div className="flex min-h-[40px] flex-wrap items-center px-3">
-					 overflow-x-auto whitespace-nowrap">
 			   {(visibleMenu[activeIdx]?.subMenu ?? [])
 			    .filter (item => item.visible ?? true)
 			    .map ((item, i) => (
 			       'component' in item
 			       ? (
-				   <div key={`c-${ i }`}>
+				   <div key={`c-${ i }`} className="min-w-0 max-w-full">
 				     {item.component}
 				   </div>)
 			       : (
-				   <div key={`l-${ i }`}>
+				   <div key={`l-${ i }`} className="min-w-0 max-w-full">
 				     <PrefetchLink
 					 to={item.to}
 					 target={item.to.slice (0, 2) === '//'
 						 ? '_blank'
 						 : undefined}
-					 className="top-nav-menu-link h-full flex items-center px-3">
+					 className="top-nav-menu-link flex min-h-[40px]
-				       {item.name}
+						    items-center px-3 py-2">
+				       <LocalisedText language={item.nameLanguage ?? 'ja'}>
+					 {item.name}
+				       </LocalisedText>
 				     </PrefetchLink>
 				   </div>)))}
 			 </div>)
 		     : (
-			 <AnimatePresence initial={false} custom={dir}>
+			 <AnimatePresence initial={false} custom={dir} mode="popLayout">
 			   <motion.div
 			       key={activeIdx}
 			       custom={dir}
 			       variants={{ enter: (d: -1 | 1) => ({ y: d * 24, opacity: 0 }),
 					   centre: { y: 0, opacity: 1 },
 					   exit: (d: -1 | 1) => ({ y: (-d) * 24, opacity: 0 }) }}
-			       className="absolute inset-0 flex items-center px-3
+			       className="relative flex min-h-[40px] flex-wrap items-center px-3"
-					  overflow-x-auto whitespace-nowrap"
 			       initial="enter"
 			       animate="centre"
 			       exit="exit"
@@ -495,27 +618,33 @@ const TopNav: FC<Props> = ({ user }) => {
 				 ? (
 				     <motion.div
 					 key={`c-${ i }`}
+					 className="min-w-0 max-w-full"
 					 transition={{ layout: topNavTransition }}
-					 layoutId={`submenu-${ visibleMenu[activeIdx].name }-${ i }`}>
+					 layoutId={`${ activeSubmenuId }-${ i }`}>
 				       {item.component}
 				     </motion.div>)
 				 : (
 				     <motion.div
 					 key={`l-${ i }`}
+					 className="min-w-0 max-w-full"
 					 transition={{ layout: topNavTransition }}
-					 layoutId={`submenu-${ visibleMenu[activeIdx].name }-${ i }`}>
+					 layoutId={`${ activeSubmenuId }-${ i }`}>
 				       <PrefetchLink
 					   to={item.to}
 					   target={item.to.slice (0, 2) === '//'
 						   ? '_blank'
 						   : undefined}
-					   className="top-nav-menu-link h-full flex items-center px-3">
+					   className="top-nav-menu-link flex min-h-[40px]
-					 {item.name}
+						      items-center px-3 py-2">
+					 <LocalisedText language={item.nameLanguage ?? 'ja'}>
+					   {item.name}
+					 </LocalisedText>
 				       </PrefetchLink>
 				     </motion.div>)))}
 			   </motion.div>
 			 </AnimatePresence>)}
 		  </div>))}
+	  </div>
 	  </motion.div>
 	</AnimatePresence>
 
@@ -540,7 +669,9 @@ const TopNav: FC<Props> = ({ user }) => {
 				   setOpenItemIdx (i)
 				 }
 			     }}>
-			   {item.name}
+			   <LocalisedText language={item.nameLanguage ?? 'ja'}>
+			     {item.name}
+			   </LocalisedText>
 			 </PrefetchLink>
 
 			 {i === openItemIdx && (
@@ -561,7 +692,9 @@ const TopNav: FC<Props> = ({ user }) => {
 						   ? '_blank'
 						   : undefined}
 					   className="top-nav-mobile-row w-full min-h-[36px] flex items-center pl-12">
-					 {subItem.name}
+					 <LocalisedText language={subItem.nameLanguage ?? 'ja'}>
+					   {subItem.name}
+					 </LocalisedText>
 				       </PrefetchLink>)))}
 			     </div>)}
 		       </Fragment>))}
@@ -570,7 +703,7 @@ const TopNav: FC<Props> = ({ user }) => {
 		       className={cn ('top-nav-mobile-row w-full min-h-[40px] flex items-center pl-8',
 				      ((openItemIdx < 0)
 				       && 'top-nav-mobile-active font-bold'))}>
-		     その他 &raquo;
+		     <TranslatedText messageKey="more"/>
 		   </PrefetchLink>
 		   <TopNavUser user={user} sp/>
 		   <Separator/>
@@ -605,7 +738,9 @@ const TopNav: FC<Props> = ({ user }) => {
 				     setOpenItemIdx (i)
 				   }
 			       }}>
-			     {item.name}
+			     <LocalisedText language={item.nameLanguage ?? 'ja'}>
+			       {item.name}
+			     </LocalisedText>
 			   </PrefetchLink>
 
 			   <AnimatePresence initial={false}>
@@ -639,7 +774,10 @@ const TopNav: FC<Props> = ({ user }) => {
 						       ? '_blank'
 						       : undefined}
 					       className="top-nav-mobile-row w-full min-h-[36px] flex items-center pl-12">
-					     {subItem.name}
+					     <LocalisedText
+						 language={subItem.nameLanguage ?? 'ja'}>
+					       {subItem.name}
+					     </LocalisedText>
 					   </PrefetchLink>)))}
 				 </motion.div>)}
 			   </AnimatePresence>
@@ -649,7 +787,7 @@ const TopNav: FC<Props> = ({ user }) => {
 			 className={cn ('top-nav-mobile-row w-full min-h-[40px] flex items-center pl-8',
 					((openItemIdx < 0)
 					 && 'top-nav-mobile-active font-bold'))}>
-		       その他 &raquo;
+		       <TranslatedText messageKey="more"/>
 		     </PrefetchLink>
 		     <TopNavUser user={user} sp/>
 		     <Separator/>

frontend/src/components/TopNavUser.test.tsx

@@ -17,7 +17,7 @@ describe ('TopNavUser', () => {
 
     expect (screen.getByRole ('link', { name: '山田' })).toHaveAttribute (
         'href',
-        '/users/settings',
+        '/ja/users/settings',
     )
   })
 

frontend/src/components/TopNavUser.tsx

@@ -1,6 +1,7 @@
 import Separator from '@/components/MenuSeparator'
 import PrefetchLink from '@/components/PrefetchLink'
 import { cn } from '@/lib/utils'
+import { useUITranslation } from '@/lib/useUITranslation'
 
 import type { FC } from 'react'
 
@@ -11,6 +12,7 @@ type Props = { user:  User | null,
 
 
 const TopNavUser: FC<Props> = ({ user, sp }) => {
+  const { label } = useUITranslation ('shared')
   if (!(user))
     return
 
@@ -23,9 +25,8 @@ const TopNavUser: FC<Props> = ({ user, sp }) => {
   return (
       <>
 	{sp && <Separator/>}
-	<PrefetchLink to="/users/settings"
+	<PrefetchLink to="/users/settings" className={className}>
-	      className={className}>
+	  {user.name || label ('labels.anonymous')}
-	  {user.name || '名もなきニジラー'}
 	</PrefetchLink>
       </>)
 }

frontend/src/components/TranslatedText.tsx

@@ -0,0 +1,23 @@
+import LocalisedText from '@/components/LocalisedText'
+import { useUITranslation } from '@/lib/useUITranslation'
+
+type Props = {
+    messageKey: string
+    namespace?: string
+    values?: Record<string, string | number>
+    className?: string }
+
+
+const TranslatedText = (
+    { messageKey, namespace = 'navigation', values, className }: Props,
+) => {
+  const { message } = useUITranslation (namespace)
+  const result = message (messageKey, values)
+  return (
+      <LocalisedText language={result.language} className={className}>
+	{result.text}
+      </LocalisedText>)
+}
+
+
+export default TranslatedText

frontend/src/components/WikiBody.tsx

@@ -3,16 +3,20 @@ import { useMemo } from 'react'
 import ReactMarkdown from 'react-markdown'
 import remarkGFM from 'remark-gfm'
 
+import { useLocale } from '@/lib/useLocale'
+import { useUITranslation } from '@/lib/useUITranslation'
 import PrefetchLink from '@/components/PrefetchLink'
 import { wikiKeys } from '@/lib/queryKeys'
 import remarkWikiAutoLink from '@/lib/remark-wiki-autolink'
-import { fetchWikiPages } from '@/lib/wiki'
+import { fetchWikiAutolinkCandidates } from '@/lib/wiki'
+import { ainuMDXComponents, LocalisedDocument } from '@/mdx-components'
 
 import type { FC } from 'react'
 import type { Components } from 'react-markdown'
 
 type Props = { title: string
-	       body?: string }
+	       body?: string
+	       language?: string }
 
 const mdComponents = { a: (({ href, children }) => (
 			      ['/', '.'].some (e => href?.startsWith (e))
@@ -25,20 +29,33 @@ const mdComponents = { a: (({ href, children }) => (
 				  </a>))) } as const satisfies Components
 
 
-const WikiBody: FC<Props> = ({ title, body }) => {
+const WikiBody: FC<Props> = ({ title, body, language = 'und' }) => {
+  const { message } = useUITranslation ('wiki')
+  const locale = useLocale ()
+  const missingPage = message ('missingPage', {
+      url: `/wiki/new?title=${ encodeURIComponent (title) }` })
+  const contentLanguage = body ? language : missingPage.language
+  const matchLanguage = contentLanguage === 'und'
+      ? 'ja' : (contentLanguage === 'ain-Kana' ? 'ain' : contentLanguage)
   const { data } = useQuery ({
       enabled: Boolean (body),
-      queryKey: wikiKeys.index ({ }),
+      queryKey: wikiKeys.autolinkCandidates (matchLanguage, locale),
-      queryFn: () => fetchWikiPages ({ }) })
+      queryFn: () => fetchWikiAutolinkCandidates (matchLanguage, locale) })
-  const pageNames = (data ?? []).map (page => page.title).sort ((a, b) => b.length - a.length)
 
   const remarkPlugins = useMemo (
-      () => [() => remarkWikiAutoLink (pageNames), remarkGFM], [pageNames])
+      () => [() => remarkWikiAutoLink (data ?? [], matchLanguage, locale), remarkGFM],
+      [data, matchLanguage, locale])
+  const components = {
+      ...((contentLanguage === 'ain' || contentLanguage === 'ain-Kana')
+	  ? ainuMDXComponents : { }),
+      ...mdComponents }
 
   return (
-      <ReactMarkdown components={mdComponents} remarkPlugins={remarkPlugins}>
+      <LocalisedDocument language={contentLanguage}>
-	{body || `このページは存在しません。[新規作成してください](/wiki/new?title=${ encodeURIComponent (title) })。`}
+	<ReactMarkdown components={components} remarkPlugins={remarkPlugins}>
-      </ReactMarkdown>)
+	  {body || missingPage.text}
+	</ReactMarkdown>
+      </LocalisedDocument>)
 }
 
 export default WikiBody

frontend/src/components/common/FieldError.tsx

@@ -1,7 +1,7 @@
-import type { FC } from 'react'
+import type { FC, ReactNode } from 'react'
 
 type Props = { id?:        string
-	       messages?:  string[] }
+	       messages?:  ReactNode[] }
 
 
 export const FieldError: FC<Props> = ({ id, messages }: Props) => {

frontend/src/components/common/FieldWarning.tsx

@@ -1,7 +1,7 @@
-import type { FC } from 'react'
+import type { FC, ReactNode } from 'react'
 
 type Props = { id?:        string
-	       messages?:  string[] }
+	       messages?:  ReactNode[] }
 
 
 export const FieldWarning: FC<Props> = ({ id, messages }: Props) => {

frontend/src/components/common/FormField.tsx

@@ -16,7 +16,7 @@ type Props = {
 		   onChange: (event: React.ChangeEvent<HTMLInputElement>) => void }
     className?:  string
     label:      ReactNode
-    messages?:  string[] }
+    messages?:  ReactNode[] }
 
 
 const FormField: FC<Props> = ({ children, checkBox, className, label, messages }: Props) => {

frontend/src/components/common/PageHead.tsx

@@ -0,0 +1,46 @@
+import { Helmet } from 'react-helmet-async'
+import { useLocation } from 'react-router-dom'
+
+import { useLocale } from '@/lib/useLocale'
+import { useUITranslation } from '@/lib/useUITranslation'
+import { currentRenderContext } from '@/lib/renderContext'
+
+import type { ReactNode } from 'react'
+
+type LocalisedTitle = { text: string; language: string }
+type Props = {
+    title?: string | LocalisedTitle
+    includeSiteName?: boolean
+    description?: LocalisedTitle
+    canonical?: string
+    children?: ReactNode }
+
+
+const PageHead = (
+    { title, includeSiteName = true, description: pageDescription, canonical, children }: Props,
+) => {
+  const locale = useLocale ()
+  const location = useLocation ()
+  const origin = currentRenderContext ()?.origin
+  const pageCanonical = canonical ?? (origin == null
+      ? undefined : new URL (location.pathname + location.search, origin).href)
+  const { message, siteTitle } = useUITranslation ('shared')
+  const pageTitle = typeof title === 'string' ? { text: title, language: locale } : title
+  const fullTitle =
+      pageTitle == null
+      ? siteTitle.text
+      : (includeSiteName ? `${pageTitle.text} | ${siteTitle.text}` : pageTitle.text)
+  const description = pageDescription ?? pageTitle
+      ?? message ('head.description', { brand: siteTitle.text })
+
+  return (
+      <Helmet>
+	<title lang={pageTitle?.language ?? siteTitle.language}>{fullTitle}</title>
+	<meta name="description" content={description.text} lang={description.language}/>
+	{pageCanonical != null && <link rel="canonical" href={pageCanonical}/>}
+	{children}
+      </Helmet>)
+}
+
+
+export default PageHead

frontend/src/components/common/Pagination.test.tsx

@@ -13,11 +13,11 @@ describe ('Pagination', () => {
 
     expect (screen.getByLabelText ('前のページ')).toHaveAttribute (
         'href',
-        '/posts?tags=abc&page=2',
+        '/ja/posts?tags=abc&page=2',
     )
     expect (screen.getByLabelText ('次のページ')).toHaveAttribute (
         'href',
-        '/posts?tags=abc&page=4',
+        '/ja/posts?tags=abc&page=4',
     )
     expect (screen.getByText ('3')).toHaveAttribute ('aria-current', 'page')
   })
@@ -33,6 +33,6 @@ describe ('Pagination', () => {
 
     rerender (<Pagination page={1} totalPages={2}/>)
 
-    expect (screen.getByLabelText ('次のページ')).toHaveAttribute ('href', '/tags?page=2')
+    expect (screen.getByLabelText ('次のページ')).toHaveAttribute ('href', '/ja/tags?page=2')
   })
 })

frontend/src/components/common/Pagination.tsx

@@ -1,6 +1,7 @@
 import { useLocation } from 'react-router-dom'
 
 import PrefetchLink from '@/components/PrefetchLink'
+import { useUITranslation } from '@/lib/useUITranslation'
 
 import type { FC } from 'react'
 
@@ -49,6 +50,7 @@ const getPages = (
 
 const Pagination: FC<Props> = ({ page, totalPages, siblingCount = 3 }) => {
   const location = useLocation ()
+  const { message } = useUITranslation ()
 
   const buildTo = (p: number) => {
     const qs = new URLSearchParams (location.search)
@@ -59,7 +61,9 @@ const Pagination: FC<Props> = ({ page, totalPages, siblingCount = 3 }) => {
   const pages = getPages (page, totalPages, siblingCount)
 
   return (
-      <nav className="mt-4 flex justify-center" aria-label="Pagination">
+      <nav className="mt-4 flex justify-center"
+	  lang={message ('pagination.label').language}
+	  aria-label={message ('pagination.label').text}>
 	<div className="flex items-center gap-2">
 	  {(page > 1)
 	   ? (
@@ -67,13 +71,15 @@ const Pagination: FC<Props> = ({ page, totalPages, siblingCount = 3 }) => {
 		<PrefetchLink
 		    className="md:hidden p-2"
 		    to={buildTo (1)}
-		    aria-label="最初のページ">
+		    lang={message ('pagination.first').language}
+		    aria-label={message ('pagination.first').text}>
 		  |&lt;
 		</PrefetchLink>
 		<PrefetchLink
 		    className="p-2"
 		    to={buildTo (page - 1)}
-		    aria-label="前のページ">
+		    lang={message ('pagination.previous').language}
+		    aria-label={message ('pagination.previous').text}>
 		  &lt;
 		</PrefetchLink>
 	      </>)
@@ -106,13 +112,15 @@ const Pagination: FC<Props> = ({ page, totalPages, siblingCount = 3 }) => {
 		<PrefetchLink
 		    className="p-2"
 		    to={buildTo (page + 1)}
-		    aria-label="次のページ">
+		    lang={message ('pagination.next').language}
+		    aria-label={message ('pagination.next').text}>
 		  &gt;
 		</PrefetchLink>
 		<PrefetchLink
 		    className="md:hidden p-2"
 		    to={buildTo (totalPages)}
-		    aria-label="最後のページ">
+		    lang={message ('pagination.last').language}
+		    aria-label={message ('pagination.last').text}>
 		  &gt;|
 		</PrefetchLink>
 	      </>)

frontend/src/components/common/TabGroup.tsx

@@ -3,7 +3,7 @@ import type { FC } from 'react'
 import React, { useState } from 'react'
 import { cn } from '@/lib/utils'
 
-type TabProps = { name:     string
+type TabProps = { name:     React.ReactNode
 		  init?:    boolean
 		  children: React.ReactNode }
 

frontend/src/components/common/TagInput.test.tsx

@@ -1,8 +1,9 @@
-import { fireEvent, render, screen, waitFor } from '@testing-library/react'
+import { fireEvent, screen, waitFor } from '@testing-library/react'
 import { beforeEach, describe, expect, it, vi } from 'vitest'
 
 import TagInput from '@/components/common/TagInput'
 import { buildTag } from '@/test/factories'
+import { renderWithProviders as render } from '@/test/render'
 
 const api = vi.hoisted (() => ({
   apiGet: vi.fn (),
@@ -26,7 +27,8 @@ describe ('TagInput', () => {
     await waitFor (() => {
       expect (api.apiGet).toHaveBeenCalledWith (
           '/tags/autocomplete',
-          { params: { q: '虹夏', nico: '0' } },
+          { locale: 'ja', params: { q: '虹夏', nico: '0' },
+	    signal: expect.any (AbortSignal) },
       )
     })
     expect (setValue).toHaveBeenCalledWith ('ぼっち 虹夏')
@@ -53,7 +55,8 @@ describe ('TagInput', () => {
     await waitFor (() => {
       expect (api.apiGet).toHaveBeenCalledWith (
           '/tags/autocomplete',
-          { params: { q: '虹夏', nico: '1' } },
+          { locale: 'ja', params: { q: '虹夏', nico: '1' },
+	    signal: expect.any (AbortSignal) },
       )
     })
   })