From f362b915a5730d78ea02f56b7297bb61f72a61e2 Mon Sep 17 00:00:00 2001
From: miteruzo <miteruzo@naver.com>
Date: Fri, 16 Oct 2026 00:15:21 +0900
Subject: [PATCH] #431

---
 backend/spec/db/wiki_removal_spec.rb          |  23 +++
 backend/spec/models/tag_group_spec.rb         |  16 +-
 .../models/tag_name_sanitisation_rule_spec.rb |  60 +++++++
 backend/spec/models/user_spec.rb              |  25 +++
 .../tag_description_wiki_write_spec.rb        |   3 +-
 .../spec/requests/tag_group_locale_spec.rb    | 122 ++++++++++++++
 .../spec/requests/tag_group_markdown_spec.rb  |   9 +
 backend/spec/requests/tag_group_wiki_spec.rb  |  10 +-
 backend/spec/requests/tag_versions_spec.rb    |   1 +
 backend/spec/requests/tags_spec.rb            |   7 +-
 backend/spec/requests/wiki_conflict_spec.rb   |   1 +
 backend/spec/requests/wiki_locale_spec.rb     | 158 ++++++++++++++++++
 backend/spec/requests/wiki_spec.rb            |  18 +-
 backend/spec/support/ainu_locale_contract.rb  |  22 +++
 backend/spec/support/tag_group_records.rb     |  11 +-
 backend/spec/support/wiki_records.rb          |   4 +-
 16 files changed, 458 insertions(+), 32 deletions(-)
 create mode 100644 backend/spec/db/wiki_removal_spec.rb
 create mode 100644 backend/spec/models/user_spec.rb
 create mode 100644 backend/spec/requests/tag_group_locale_spec.rb
 create mode 100644 backend/spec/requests/wiki_locale_spec.rb
 create mode 100644 backend/spec/support/ainu_locale_contract.rb

diff --git a/backend/spec/db/wiki_removal_spec.rb b/backend/spec/db/wiki_removal_spec.rb
new file mode 100644
index 0000000..33fe633
--- /dev/null
+++ b/backend/spec/db/wiki_removal_spec.rb
@@ -0,0 +1,23 @@
+require 'rails_helper'
+
+RSpec.describe 'Schema after Wiki removal' do
+  it 'has no legacy Wiki tables or name indirection columns' do
+    connection = ApplicationRecord.connection
+    ['wiki_pages', 'wiki_revisions', 'wiki_lines', 'wiki_revision_lines', 'wiki_versions']
+        .each do |table|
+      expect(connection.table_exists?(table)).to be(false)
+    end
+    expect(connection.column_exists?(:tags, :tag_name_id)).to be(false)
+    expect(connection.column_exists?(:tag_names, :canonical_id)).to be(false)
+  end
+
+  it 'requires TagName ownership while keeping the native resources and history' do
+    connection = ApplicationRecord.connection
+    expect(TagName.columns_hash.fetch('tag_id').null).to be(false)
+    expect(connection.foreign_key_exists?(:tag_names, :tags)).to be(true)
+    ['tag_descriptions', 'tag_description_versions', 'tag_groups', 'tag_group_versions']
+        .each do |table|
+      expect(connection.table_exists?(table)).to be(true)
+    end
+  end
+end
diff --git a/backend/spec/models/tag_group_spec.rb b/backend/spec/models/tag_group_spec.rb
index 67c1125..9e5be9d 100644
--- a/backend/spec/models/tag_group_spec.rb
+++ b/backend/spec/models/tag_group_spec.rb
@@ -4,7 +4,8 @@ RSpec.describe TagGroup, type: :model do
   let(:actor) { create_member_user! }
 
   def create_group name:, members: [], placements: []
-    TagGroupOperation.create!(name:, description: nil, members:, placements:, actor:)
+    TagGroupOperation.create!(
+        Locale.nipponese, name:, description: nil, members:, placements:, actor:)
   end
 
   it 'retains version IDs and snapshots after destroying an empty group' do
@@ -16,7 +17,8 @@ RSpec.describe TagGroup, type: :model do
 
     expect(TagGroupVersion.where(tag_group_id: group.id).order(:version_no).map(&:attributes))
         .to eq(versions)
-    expect(TagGroupRepr.historical(TagGroupVersion.find(versions.first.fetch('id'))))
+    expect(TagGroupRepr.historical(
+        Locale.nipponese, TagGroupVersion.find(versions.first.fetch('id'))))
         .to include('id' => group.id, 'name' => 'history owner', 'members' => [])
   end
 
@@ -26,14 +28,8 @@ RSpec.describe TagGroup, type: :model do
     parent = create_group(
         name: 'parent group',
         members: [{ 'tag_group_id' => child.id }],
-        placements: [{
-            'section_name' => 'section',
-            'description' => nil,
-            'children' => [{
-                'tag_group_id' => child.id,
-                'children' => []
-            }]
-        }])
+        placements: [{ 'section_name' => 'section', 'description' => nil,
+                       'children' => [{ 'tag_group_id' => child.id, 'children' => [] }] }])
 
     versions = parent.versions.order(:version_no).map(&:attributes)
 
diff --git a/backend/spec/models/tag_name_sanitisation_rule_spec.rb b/backend/spec/models/tag_name_sanitisation_rule_spec.rb
index cec475d..58bd168 100644
--- a/backend/spec/models/tag_name_sanitisation_rule_spec.rb
+++ b/backend/spec/models/tag_name_sanitisation_rule_spec.rb
@@ -34,6 +34,66 @@ RSpec.describe TagNameSanitisationRule, type: :model do
       described_class.create!(priority: 10, source_pattern: 'foo_', replacement: 'foo')
     end
 
+    [:primary, :alias].each do |source_kind|
+      it "keeps the primary identity when a #{ source_kind } collides within its Tag" do
+        tag = create(:tag, primary_name: source_kind == :primary ? 'temporary' : 'foobar')
+        primary = tag.tag_name('ja')
+        alias_name = create(:tag_name, :alias, tag:,
+                             name: source_kind == :primary ? 'foobar' : 'temporary_alias')
+        source = source_kind == :primary ? primary : alias_name
+        source.update_columns(name: 'foo_bar')
+
+        expect { described_class.apply! }.to change(TagName, :count).by(-1)
+            .and change(Tag, :count).by(0)
+
+        expect(primary.reload).to have_attributes(
+            name: 'foobar', primary_flg: true, tag_id: tag.id)
+        expect(TagName.exists?(alias_name.id)).to be(false)
+        expect(TagName.where(tag:, language_code: 'ja', primary_flg: true))
+            .to contain_exactly(primary)
+        expect(tag.tag_versions.order(:version_no).last.names.fetch('ja'))
+            .to include('name' => 'foobar', 'aliases' => [])
+      end
+    end
+
+    it 'deduplicates colliding aliases without changing the primary name' do
+      tag = create(:tag, primary_name: 'primary')
+      primary = tag.tag_name('ja')
+      kept = create(:tag_name, :alias, tag:, name: 'foobar')
+      removed = create(:tag_name, :alias, tag:, name: 'temporary_alias')
+      removed.update_columns(name: 'foo_bar')
+
+      described_class.apply!
+
+      expect(primary.reload).to have_attributes(name: 'primary', primary_flg: true)
+      expect(kept.reload.tag_id).to eq(tag.id)
+      expect(TagName.exists?(removed.id)).to be(false)
+      expect(tag.tag_versions.order(:version_no).last.names.fetch('ja').fetch('aliases'))
+          .to eq([{ 'name' => 'foobar', 'script_code' => 'Jpan' }])
+    end
+
+    it 'rolls back a collision merge when the source owns a description' do
+      user = create_member_user!
+      target = create(:tag, primary_name: 'foobar')
+      source = create(:tag, primary_name: 'temporary')
+      TagDescriptionOperation.create!(
+          Locale.nipponese, tag: source, body: 'retained', created_by_user: user)
+      source.tag_name('ja').update_columns(name: 'foo_bar')
+      post = create(:post)
+      PostTag.create!(post:, tag: source)
+      models = [Tag, TagName, TagVersion, TagDescription, TagDescriptionVersion, PostTag]
+      snapshots = models.map { |model| model.order(*Array(model.primary_key)).map(&:attributes) }
+
+      expect { described_class.apply! }.to raise_error(ActiveRecord::RecordInvalid)
+
+      after_state = models.map do |model|
+        model.order(*Array(model.primary_key)).map(&:attributes)
+      end
+      expect(after_state).to eq(snapshots)
+      expect(post.reload.tags).to contain_exactly(source)
+      expect(target.reload.name('ja')).to eq('foobar')
+    end
+
     context 'when only another language has the sanitised name' do
       include_context 'English locale'
 
diff --git a/backend/spec/models/user_spec.rb b/backend/spec/models/user_spec.rb
new file mode 100644
index 0000000..692d682
--- /dev/null
+++ b/backend/spec/models/user_spec.rb
@@ -0,0 +1,25 @@
+require 'rails_helper'
+
+RSpec.describe User, type: :model do
+  it 'nullifies description authorship without deleting native content or history' do
+    author = create_member_user!
+    editor = create_member_user!
+    tag = create(:tag)
+    description = TagDescriptionOperation.create!(
+        Locale.nipponese, tag:, body: 'initial', created_by_user: author)
+    TagDescriptionOperation.update!(
+        Locale.nipponese, tag:, body: 'edited', updated_by_user: editor)
+    versions = TagDescriptionVersion.where(tag_id: tag.id).order(:version_no)
+    snapshots = versions.map(&:attributes)
+
+    expect(author.created_tag_descriptions).to contain_exactly(description)
+    expect(editor.updated_tag_descriptions).to contain_exactly(description)
+    expect { author.destroy! }.to change(TagDescription, :count).by(0)
+        .and change(TagDescriptionVersion, :count).by(0)
+    expect(description.reload).to have_attributes(
+        body: 'edited', created_by_user_id: nil, updated_by_user_id: editor.id)
+    expect { editor.destroy! }.not_to change(TagDescription, :count)
+    expect(description.reload.updated_by_user_id).to be_nil
+    expect(versions.reload.map(&:attributes)).to eq(snapshots)
+  end
+end
diff --git a/backend/spec/requests/tag_description_wiki_write_spec.rb b/backend/spec/requests/tag_description_wiki_write_spec.rb
index 0658d7c..53b9675 100644
--- a/backend/spec/requests/tag_description_wiki_write_spec.rb
+++ b/backend/spec/requests/tag_description_wiki_write_spec.rb
@@ -26,7 +26,8 @@ RSpec.describe 'Tag description Wiki facade writes', type: :request do
 
   context 'with an existing description' do
     let!(:description) do
-      TagDescriptionOperation.create!(tag:, body: 'before', created_by_user: user)
+      TagDescriptionOperation.create!(
+          Locale.nipponese, tag:, body: 'before', created_by_user: user)
     end
     let!(:first_version) { current_description_version(description) }
 
diff --git a/backend/spec/requests/tag_group_locale_spec.rb b/backend/spec/requests/tag_group_locale_spec.rb
new file mode 100644
index 0000000..bc3088e
--- /dev/null
+++ b/backend/spec/requests/tag_group_locale_spec.rb
@@ -0,0 +1,122 @@
+require 'rails_helper'
+
+RSpec.describe 'Tag group locale contracts', type: :request do
+  include TagGroupRecords
+  include_context 'Ainu locale contract'
+
+  let!(:user) { create_member_user! }
+  let!(:tag) { create(:tag, primary_name: 'japanese_member') }
+  let!(:ainu_name) { add_ainu_name(tag, 'ainu_member') }
+  let(:headers) { { 'X-Transfer-Code' => user.inheritance_code } }
+  let(:members) { [{ 'tag_id' => tag.id }] }
+  let(:placements) do
+    [{ 'section_name' => 'section', 'description' => nil, 'children' => [
+        { 'tag_id' => tag.id, 'children' => [
+            { 'tag_id' => tag.id, 'children' => [] }] }] }]
+  end
+  let!(:group) do
+    TagVersioning.ensure_snapshot!(tag, created_by_user: user)
+    TagGroupOperation.create!(
+        ainu_locale, name: 'locale group', description: nil, members:, placements:, actor: user)
+  end
+
+  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' }
+      expect(response).to have_http_status(:ok)
+      representation = json.is_a?(Array) ? json.sole : json
+      expect(representation.fetch('members').sole.fetch('tag').fetch('name'))
+          .to eq('ainu_member')
+      node = representation.fetch('placements').sole.fetch('children').sole
+      expect(node.fetch('tag').fetch('name')).to eq('ainu_member')
+      expect(node.fetch('children').sole.fetch('tag').fetch('name')).to eq('ainu_member')
+      expect(response.body).not_to include('japanese_member')
+    end
+  end
+
+  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' }
+    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 }
+    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 }
+    expect(response).to have_http_status(:ok)
+    expect(json.fetch('diff').map { _1.fetch('type') }.uniq).to eq(['context'])
+  end
+
+  ['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' },
+          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' }
+      expect(response).to have_http_status(:ok)
+      expect(json.fetch('id')).to eq(id)
+      get "#{ path }/exists", params: { locale: 'ain' }
+      expect(response).to have_http_status(:no_content)
+      get '/wiki/search', params: { locale: 'ain', 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
+      expect(response).to have_http_status(:ok)
+      get "/tag_groups/#{ id }", params: { locale: 'ain' }
+      expect(json.fetch('members').sole.fetch('tag').fetch('name')).to eq('ainu_member')
+    end
+  end
+
+  it 'resolves Markdown names in the requested language and rolls back invalid input' do
+    parsed = TagGroupMarkdownParser.parse(ainu_locale, body: '- ainu_member')
+    expect(parsed.fetch(:members)).to eq(members)
+    expect do
+      TagGroupMarkdownParser.parse(ainu_locale, body: '- japanese_member')
+    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' },
+        headers: headers
+    expect(response).to have_http_status(:unprocessable_entity)
+    expect(group_state).to eq(before_state)
+  end
+
+  it 'passes locale into native validation and facade compatibility checks' do
+    post '/tag_groups', params: {
+        locale: 'ain', 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' }
+    expect(response).to have_http_status(:ok)
+    body = json.fetch('body')
+    put "/wiki/#{ id }", params: { locale: 'ain', title: 'tag_group:native', body: },
+        headers: headers
+    expect(response).to have_http_status(:ok)
+    expect(TagGroup.find(id).version_no).to eq(1)
+  end
+
+  it 'does not substitute current or Japanese names for a missing historical language' do
+    other = create(:tag, primary_name: 'historical_japanese')
+    TagVersioning.ensure_snapshot!(other, created_by_user: user)
+    old_group = TagGroupOperation.create!(
+        Locale.nipponese, name: 'old group', description: nil,
+        members: [{ 'tag_id' => other.id }],
+        placements: [{ 'tag_id' => other.id, 'children' => [] }], actor: user)
+    add_ainu_name(other, 'current_ainu')
+    version = old_group.versions.sole
+    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 }
+    expect(response).to have_http_status(:unprocessable_entity)
+    expect(response.body).not_to include('historical_japanese', 'current_ainu')
+  end
+end
diff --git a/backend/spec/requests/tag_group_markdown_spec.rb b/backend/spec/requests/tag_group_markdown_spec.rb
index 68cc37b..2e12c9e 100644
--- a/backend/spec/requests/tag_group_markdown_spec.rb
+++ b/backend/spec/requests/tag_group_markdown_spec.rb
@@ -115,6 +115,15 @@ RSpec.describe 'Tag group Markdown round trips through the Wiki facade', type: :
         MARKDOWN
   end
 
+  it 'round trips a top-level list followed by heading Sections' do
+    check_round_trip(
+        members: [tag_member(series), tag_member(deer)],
+        placements: [tag_node(series),
+                     { 'section_name' => '区分', 'description' => nil,
+                       'children' => [tag_node(deer)] }],
+        markdown: "- ぼざろクリーチャーシリーズ\n\n## 区分\n\n- 洗澡鹿")
+  end
+
   it 'rejects mixed top-level heading Sections and Tags without losing structure' do
     id = seed_group(
         name: '混在構造', members: [tag_member(series)],
diff --git a/backend/spec/requests/tag_group_wiki_spec.rb b/backend/spec/requests/tag_group_wiki_spec.rb
index d24add8..73f1bad 100644
--- a/backend/spec/requests/tag_group_wiki_spec.rb
+++ b/backend/spec/requests/tag_group_wiki_spec.rb
@@ -10,8 +10,9 @@ RSpec.describe 'Tag group Wiki facade reads', type: :request do
   let!(:page) { create_markdown_group('読取り契約', '- 旧タグ') }
   let!(:first_revision) { page.versions.sole }
   let!(:last_revision) do
-    parsed = TagGroupMarkdownParser.parse(body: '- 新タグ')
+    parsed = TagGroupMarkdownParser.parse(Locale.nipponese, body: '- 新タグ')
     TagGroupOperation.update!(
+        Locale.nipponese,
         group: page, name: page.name, actor: user,
         **parsed.slice(:description, :members, :placements))
     page.versions.order(:version_no).last
@@ -67,7 +68,8 @@ RSpec.describe 'Tag group Wiki facade reads', type: :request do
   end
 
   it 'combines Tag Groups and Tag Descriptions without Help in the unfiltered list' do
-    TagDescriptionOperation.create!(tag: new_tag, body: 'tag description', created_by_user: user)
+    TagDescriptionOperation.create!(
+        Locale.nipponese, tag: new_tag, body: 'tag description', created_by_user: user)
     get '/wiki'
     expect(response).to have_http_status(:ok)
     expect(json.map { _1.fetch('title') }).to include(
@@ -87,6 +89,7 @@ RSpec.describe 'Tag group Wiki facade reads', type: :request do
   it 'does not restore a stale namespaced Wiki page after a group rename' do
     group = create_markdown_group('旧名称', '正本')
     TagGroupOperation.update!(
+        Locale.nipponese,
         group:, name: '新名称', description: '正本', members: [], placements: [], actor: user)
 
     get group_title_path('旧名称')
@@ -99,7 +102,8 @@ RSpec.describe 'Tag group Wiki facade reads', type: :request do
   end
 
   it 'orders mixed resource history by timestamp rather than independent IDs' do
-    TagDescriptionOperation.create!(tag: new_tag, body: 'description', created_by_user: user)
+    TagDescriptionOperation.create!(
+        Locale.nipponese, tag: new_tag, body: 'description', created_by_user: user)
     TagGroupVersion.update_all(created_at: 3.days.ago)
     TagDescriptionVersion.update_all(created_at: 1.day.ago)
 
diff --git a/backend/spec/requests/tag_versions_spec.rb b/backend/spec/requests/tag_versions_spec.rb
index 7165a0f..f05bb0b 100644
--- a/backend/spec/requests/tag_versions_spec.rb
+++ b/backend/spec/requests/tag_versions_spec.rb
@@ -248,6 +248,7 @@ RSpec.describe 'TagVersions API', type: :request do
               message: 'init')
 
       TagDescriptionOperation.update!(
+        Locale.nipponese,
           tag: wiki_page.tag,
           body: 'after',
           updated_by_user: member,
diff --git a/backend/spec/requests/tags_spec.rb b/backend/spec/requests/tags_spec.rb
index 897aed4..7a66889 100644
--- a/backend/spec/requests/tags_spec.rb
+++ b/backend/spec/requests/tags_spec.rb
@@ -1402,11 +1402,8 @@ RSpec.describe 'Tags API', type: :request do
                 message: 'init')
 
         TagDescriptionOperation.update!(
-          tag: wiki_page.tag,
-          body: 'wiki body before',
-          updated_by_user: member_user,
-          message: 'init'
-        )
+            Locale.nipponese, tag: wiki_page.tag, body: 'wiki body before',
+            updated_by_user: member_user, message: 'init')
 
         wiki_history = description_versions(wiki_page).map(&:attributes)
 
diff --git a/backend/spec/requests/wiki_conflict_spec.rb b/backend/spec/requests/wiki_conflict_spec.rb
index 5da7988..55c2f35 100644
--- a/backend/spec/requests/wiki_conflict_spec.rb
+++ b/backend/spec/requests/wiki_conflict_spec.rb
@@ -19,6 +19,7 @@ RSpec.describe 'Wiki conflict handling', type: :request do
     stale_id = current_description_version(page).id
 
     TagDescriptionOperation.update!(
+        Locale.nipponese,
         tag: page.tag,
         body: 'second',
         updated_by_user: user,
diff --git a/backend/spec/requests/wiki_locale_spec.rb b/backend/spec/requests/wiki_locale_spec.rb
new file mode 100644
index 0000000..f8a653b
--- /dev/null
+++ b/backend/spec/requests/wiki_locale_spec.rb
@@ -0,0 +1,158 @@
+require 'rails_helper'
+
+RSpec.describe 'Wiki and native API locale contracts', type: :request do
+  include WikiRecords
+  include TagGroupRecords
+  include_context 'Ainu locale contract'
+
+  let!(:user) { create_member_user! }
+  let!(:tag) { create(:tag, primary_name: 'japanese_title') }
+  let!(:ainu_name) { add_ainu_name(tag, 'ainu_title') }
+  let(:headers) { { 'X-Transfer-Code' => user.inheritance_code } }
+  let!(:japanese) do
+    TagDescriptionOperation.create!(
+        Locale.nipponese, tag:, body: 'Japanese body', created_by_user: user)
+  end
+  let!(:ainu) do
+    TagDescriptionOperation.create!(
+        ainu_locale, tag:, body: 'Ainu body', created_by_user: user)
+  end
+
+  ['/wiki', '/wiki/search'].each do |path|
+    it "filters #{ path } by the selected language" do
+      get path, params: { locale: 'ain' }
+      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' }
+      expect(response).to have_http_status(:ok)
+      expect(json).to eq([])
+    end
+  end
+
+  it 'uses the existing default locale when no locale is specified' do
+    get '/wiki'
+    expect(response).to have_http_status(:ok)
+    expect(json.map { _1.fetch('id') }).to eq([japanese.id])
+  end
+
+  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' }
+      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' }
+      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' }
+    expect(response).to have_http_status(:no_content)
+    get '/wiki/title/japanese_title/exists', params: { locale: 'ain' }
+    expect(response).to have_http_status(:not_found)
+  end
+
+  it 'does not disclose another language through ID, existence, diff or history' 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 }
+      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 }
+    expect(response).to have_http_status(:ok)
+    expect(json).to eq([])
+    get '/wiki/changes', params: { locale: 'ain' }
+    expect(json.map { _1.fetch('revision_id') })
+        .to eq([current_description_version(ainu).id])
+  end
+
+  it 'does not update a description addressed through another language ID' 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
+    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])
+        .to eq(snapshot)
+  end
+
+  [:wiki, :native].each do |api|
+    it "creates the selected language through #{ api } without changing Japanese history" do
+      other = create(:tag, primary_name: 'other_japanese')
+      add_ainu_name(other, 'other_ainu')
+      original = TagDescriptionOperation.create!(
+          Locale.nipponese, tag: other, body: 'original', created_by_user: user)
+      snapshot = original.attributes
+      expect do
+        if api == :wiki
+          post '/wiki', params: { locale: 'ain', title: 'other_ainu', body: 'created' },
+               headers: headers
+        else
+          put "/tags/#{ other.id }/description", params: { locale: 'ain', body: 'created' },
+              headers: headers
+        end
+      end.to change(TagDescription, :count).by(1)
+          .and change(TagDescriptionVersion, :count).by(1)
+      expect(response).to have_http_status(:created)
+      created = TagDescription.find_by!(tag: other, language_code: 'ain')
+      expect(created).to have_attributes(body: 'created', version_no: 1)
+      expect(current_description_version(created)).to have_attributes(language_code: 'ain')
+      expect(original.reload.attributes).to eq(snapshot)
+    end
+  end
+
+  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' },
+        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' }
+    expect(json).to include('body' => 'native edit', 'revision_id' => second.id)
+
+    put "/wiki/#{ ainu.id }", params: {
+        locale: 'ain', 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' }
+    expect(json).to include('body' => 'facade edit', 'language_code' => 'ain', 'version_no' => 3)
+    expect(japanese.reload.attributes).to eq(snapshot)
+  end
+
+  it 'rejects a stale selected-language revision without a partial title or body edit' do
+    stale = current_description_version(ainu)
+    TagDescriptionOperation.update!(
+        ainu_locale, tag:, body: 'current', updated_by_user: user)
+    snapshot = [ainu.reload.attributes, ainu_name.attributes, japanese.attributes]
+    expect do
+      put "/wiki/#{ ainu.id }", params: {
+          locale: 'ain', 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)
+    expect([ainu.reload.attributes, ainu_name.reload.attributes, japanese.reload.attributes])
+        .to eq(snapshot)
+  end
+
+  it 'scopes historical show and diff to the selected description' 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 }
+    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 }
+    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 }
+    expect(response).to have_http_status(:not_found)
+  end
+end
diff --git a/backend/spec/requests/wiki_spec.rb b/backend/spec/requests/wiki_spec.rb
index 80f9e28..12663c0 100644
--- a/backend/spec/requests/wiki_spec.rb
+++ b/backend/spec/requests/wiki_spec.rb
@@ -232,7 +232,9 @@ RSpec.describe 'Wiki API', type: :request do
     context 'when conflict' do
       it 'returns 409 when base_revision_id mismatches' do
         # 先に別ユーザ（同じ member でもOK）が 1 回更新して先頭を進める
-        TagDescriptionOperation.update!(tag: page.tag, body: "zzz", updated_by_user: member, message: 'other edit')
+        TagDescriptionOperation.update!(
+            Locale.nipponese, tag: page.tag, body: 'zzz',
+            updated_by_user: member, message: 'other edit')
         page.reload
 
         stale_id = description_versions(page).order(:id).first.id # わざと古い id
@@ -314,12 +316,14 @@ RSpec.describe 'Wiki API', type: :request do
 
   describe 'GET /wiki/changes' do
     let!(:rev1) do
-      TagDescriptionOperation.update!(tag: page.tag, body: "a\nb", updated_by_user: user, message: 'r1')
+      TagDescriptionOperation.update!(
+          Locale.nipponese, tag: page.tag, body: "a\nb", updated_by_user: user, message: 'r1')
       current_description_version(page)
     end
 
     let!(:rev2) do
-      TagDescriptionOperation.update!(tag: page.tag, body: "a\nc", updated_by_user: user, message: 'r2')
+      TagDescriptionOperation.update!(
+          Locale.nipponese, tag: page.tag, body: "a\nc", updated_by_user: user, message: 'r2')
       current_description_version(page)
     end
 
@@ -354,7 +358,7 @@ RSpec.describe 'Wiki API', type: :request do
     it 'returns empty array when page has no revisions and filtered by id' do
       # 別ページを作って revision 無し
       tn2 = create(:tag_name, name: 'spec_no_rev')
-      # 異常データ: revision 無し WikiPage を直接作る
+      # 異常データ: Version のない TagDescription を直接作る
       p2 = TagDescription.create!(
           tag: tn2.tag, language_code: 'ja', body: 'init', version_no: 1)
 
@@ -392,12 +396,14 @@ RSpec.describe 'Wiki API', type: :request do
 
   describe 'GET /wiki/:id/diff' do
     let!(:rev_a) do
-      TagDescriptionOperation.update!(tag: page.tag, body: "a\nb\nc", updated_by_user: user, message: 'A')
+      TagDescriptionOperation.update!(
+          Locale.nipponese, tag: page.tag, body: "a\nb\nc", updated_by_user: user, message: 'A')
       current_description_version(page)
     end
 
     let!(:rev_b) do
-      TagDescriptionOperation.update!(tag: page.tag, body: "a\nx\nc", updated_by_user: user, message: 'B')
+      TagDescriptionOperation.update!(
+          Locale.nipponese, tag: page.tag, body: "a\nx\nc", updated_by_user: user, message: 'B')
       current_description_version(page)
     end
 
diff --git a/backend/spec/support/ainu_locale_contract.rb b/backend/spec/support/ainu_locale_contract.rb
new file mode 100644
index 0000000..83187cf
--- /dev/null
+++ b/backend/spec/support/ainu_locale_contract.rb
@@ -0,0 +1,22 @@
+RSpec.shared_context 'Ainu locale contract' do
+  let(:ainu_locale) { instance_double(Locale, language_code: 'ain', script_code: 'Jpan') }
+
+  before do
+    # Only the foreign-key reference is seeded; no Locale or enum is enabled.
+    Language.connection.execute(<<~SQL)
+      INSERT IGNORE INTO languages (code, name, created_at)
+      VALUES ('ain', 'Ainu', CURRENT_TIMESTAMP)
+    SQL
+    allow(Locale).to receive(:find_by).and_call_original
+    allow(Locale).to receive(:find_by).with(code: 'ain').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:,
+        primary_flg: true, auto_generated: false,
+        created_at: Time.current, updated_at: Time.current }])
+    tag.tag_names.reset
+    TagName.find_by!(tag_id: tag.id, language_code: 'ain', name:)
+  end
+end
diff --git a/backend/spec/support/tag_group_records.rb b/backend/spec/support/tag_group_records.rb
index 9d370c7..82c1693 100644
--- a/backend/spec/support/tag_group_records.rb
+++ b/backend/spec/support/tag_group_records.rb
@@ -94,13 +94,14 @@ module TagGroupRecords
     tag.reload
   end
 
-  def create_markdown_group name, body
-    parsed = TagGroupMarkdownParser.parse(body:)
-    TagGroupOperation.create!(name:, actor: user, **parsed.slice(:description, :members, :placements))
+  def create_markdown_group name, body, locale: Locale.nipponese
+    parsed = TagGroupMarkdownParser.parse(locale, body:)
+    TagGroupOperation.create!(
+        locale, name:, actor: user, **parsed.slice(:description, :members, :placements))
   end
 
-  def group_markdown group
-    TagGroupMarkdownRenderer.render(TagGroupRepr.one(group.reload))
+  def group_markdown group, locale: Locale.nipponese
+    TagGroupMarkdownRenderer.render(TagGroupRepr.one(locale, group.reload))
   end
 
   def seed_group name:, placements: [], members: [], description: nil, id: nil
diff --git a/backend/spec/support/wiki_records.rb b/backend/spec/support/wiki_records.rb
index 4dbcfb1..ff06bb1 100644
--- a/backend/spec/support/wiki_records.rb
+++ b/backend/spec/support/wiki_records.rb
@@ -1,6 +1,6 @@
 module WikiRecords
-  def seed_description(tag_name:, body:, created_by_user:, message: nil)
-    TagDescriptionOperation.create!(tag: tag_name.tag, body:, created_by_user:, message:)
+  def seed_description(tag_name:, body:, created_by_user:, message: nil, locale: Locale.nipponese)
+    TagDescriptionOperation.create!(locale, tag: tag_name.tag, body:, created_by_user:, message:)
   end
 
   def description_versions(description)