From 1e464107a858912240199b9f93727fb466eed3f7 Mon Sep 17 00:00:00 2001
From: miteruzo <miteruzo@naver.com>
Date: Thu, 15 Oct 2026 20:20:00 +0900
Subject: [PATCH] #431

---
 .../spec/db/tag_description_migration_spec.rb |  34 --
 backend/spec/db/tag_group_migration_spec.rb   | 119 -------
 backend/spec/factories/tag_names.rb           |   2 +
 backend/spec/factories/tags.rb                |  13 +-
 backend/spec/factories/wiki_pages.rb          |   9 -
 backend/spec/models/shared_tag_ids_spec.rb    |  93 ++----
 backend/spec/models/tag_group_spec.rb         |  23 ++
 .../models/tag_name_sanitisation_rule_spec.rb |  19 --
 backend/spec/models/tag_name_spec.rb          |  34 +-
 backend/spec/models/tag_spec.rb               |  60 +---
 backend/spec/requests/materials_spec.rb       |  15 +-
 .../requests/tag_description_wiki_spec.rb     |  90 +-----
 .../tag_description_wiki_write_spec.rb        | 306 ++++--------------
 .../spec/requests/tag_descriptions_spec.rb    |  88 ++---
 backend/spec/requests/tag_group_wiki_spec.rb  | 156 +--------
 .../requests/tag_group_wiki_write_spec.rb     |  57 ++--
 .../tag_group_write_integrity_spec.rb         | 163 ++--------
 backend/spec/requests/tag_groups_spec.rb      |  58 ++--
 .../spec/requests/tag_resource_ids_spec.rb    | 126 +++-----
 backend/spec/requests/tag_versions_spec.rb    |  11 +-
 .../tag_wiki_history_integrity_spec.rb        |  30 +-
 backend/spec/requests/tags_spec.rb            |  68 ++--
 backend/spec/requests/wiki_conflict_spec.rb   |  12 +-
 .../requests/wiki_creation_freeze_spec.rb     |  18 +-
 .../requests/wiki_history_integrity_spec.rb   | 170 ----------
 .../spec/requests/wiki_index_order_spec.rb    |   6 +-
 backend/spec/requests/wiki_spec.rb            |  98 ++----
 .../requests/wiki_title_collision_spec.rb     |  21 +-
 .../requests/wiki_unmigrated_contract_spec.rb |  85 +----
 ...shared_resource_id_allocator_mysql_spec.rb |  39 ++-
 .../shared_resource_id_allocator_spec.rb      | 116 ++++++-
 .../services/wiki/commit_integrity_spec.rb    | 185 -----------
 backend/spec/services/wiki/commit_spec.rb     | 151 ---------
 .../services/wiki_version_recorder_spec.rb    | 100 ------
 backend/spec/support/tag_group_records.rb     |  45 +--
 backend/spec/support/wiki_records.rb          |  28 +-
 36 files changed, 566 insertions(+), 2082 deletions(-)
 delete mode 100644 backend/spec/db/tag_description_migration_spec.rb
 delete mode 100644 backend/spec/db/tag_group_migration_spec.rb
 delete mode 100644 backend/spec/factories/wiki_pages.rb
 create mode 100644 backend/spec/models/tag_group_spec.rb
 delete mode 100644 backend/spec/requests/wiki_history_integrity_spec.rb
 delete mode 100644 backend/spec/services/wiki/commit_integrity_spec.rb
 delete mode 100644 backend/spec/services/wiki/commit_spec.rb
 delete mode 100644 backend/spec/services/wiki_version_recorder_spec.rb

diff --git a/backend/spec/db/tag_description_migration_spec.rb b/backend/spec/db/tag_description_migration_spec.rb
deleted file mode 100644
index c34c2a1..0000000
--- a/backend/spec/db/tag_description_migration_spec.rb
+++ /dev/null
@@ -1,34 +0,0 @@
-require 'rails_helper'
-require_relative '../../db/migrate/20261003010000_migrate_tag_descriptions_from_wiki_pages'
-
-RSpec.describe 'Tag description migration identity' do
-  it 'preserves every revision ID and repeated body in an independent sequence' do
-    user = create_member_user!
-    tag_name = create(:tag_name, name: 'description_migration')
-    page = Wiki::Commit.create_legacy_content!(
-        tag_name:, body: 'A', created_by_user: user)
-    revisions = [page.current_revision]
-    ['A', 'B', 'B', 'A'].each do |body|
-      revisions << Wiki::Commit.legacy_content!(
-          page:, body:, created_user: user, base_revision_id: revisions.last.id)
-    end
-    tag = create(:tag, primary_tag_name: tag_name)
-    legacy_state = [page.reload.attributes, revisions.map(&:attributes)]
-    expect(page.wiki_versions.count).to eq(3)
-
-    migration = MigrateTagDescriptionsFromWikiPages.new
-    migration.suppress_messages { migration.up }
-
-    versions = TagDescriptionVersion.where(tag_id: tag.id, language_code: 'ja')
-        .order(:version_no)
-    expect(versions.pluck(:id)).to eq(revisions.map(&:id))
-    expect(versions.pluck(:version_no)).to eq([1, 2, 3, 4, 5])
-    expect(versions.pluck(:body)).to eq(['A', 'A', 'B', 'B', 'A'])
-    expect(versions.pluck(:created_by_user_id)).to eq([user.id] * 5)
-    expect(versions.pluck(:created_at)).to eq(revisions.map(&:created_at))
-    expect(TagDescription.find(page.id)).to have_attributes(
-        tag_id: tag.id, language_code: 'ja', version_no: 5, body: 'A')
-    expect([page.reload.attributes, revisions.map { |revision| revision.reload.attributes }])
-        .to eq(legacy_state)
-  end
-end
diff --git a/backend/spec/db/tag_group_migration_spec.rb b/backend/spec/db/tag_group_migration_spec.rb
deleted file mode 100644
index c9e7566..0000000
--- a/backend/spec/db/tag_group_migration_spec.rb
+++ /dev/null
@@ -1,119 +0,0 @@
-require 'rails_helper'
-
-RSpec.describe 'Tag group migration identity and structure' do
-  include TagGroupRecords
-
-  let!(:user) { create_member_user! }
-
-  before { I18n.locale = :ja }
-
-  it 'preserves page and revision IDs, timestamps and repeated historical structures' do
-    tag = group_tag('洗澡鹿')
-    body = "説明文\n\n- 洗澡鹿\n- 洗澡鹿"
-    page = legacy_group('伊地知ニジカ亜種', body)
-    revisions = [page.current_revision]
-    [body, '# 空の区分', body].each do |text|
-      revisions << Wiki::Commit.legacy_content!(page:, body: text, created_user: user)
-    end
-    before_state = group_state.except(*TagGroupRecords::GROUP_TABLES)
-
-    migrate_groups
-
-    versions = group_rows('tag_group_versions', tag_group_id: page.id)
-        .sort_by { _1.fetch('version_no') }
-    expect(versions.map { _1.fetch('id') }).to eq(revisions.map(&:id))
-    expect(versions.map { _1.fetch('version_no') }).to eq([1, 2, 3, 4])
-    expect(versions.map { _1.fetch('created_at') }).to eq(revisions.map(&:created_at))
-    expect(versions.map { _1.fetch('created_by_user_id') }).to eq([user.id] * 4)
-    expect(versions.map { _1.fetch('event_type') }).to eq(['create', 'update', 'update', 'update'])
-    expect(group_version(page.id, 1).fetch('placements')).to eq(
-        group_version(page.id, 2).fetch('placements'))
-    expect(group_version(page.id, 3).fetch('placements')).to eq([
-        { 'section_name' => '空の区分', 'description' => nil, 'children' => [] }])
-    expect_group_snapshot(
-        page.id, number: 4, description: '説明文',
-        members: [{ 'tag_id' => tag.id, 'version_no' => tag.version_no }],
-        placements: [{ 'tag_id' => tag.id, 'children' => [] }] * 2)
-    expect(group_rows('tag_groups', id: page.id).sole).to include(
-        'created_at' => page.created_at, 'updated_at' => page.reload.updated_at)
-    expect(group_state.except(*TagGroupRecords::GROUP_TABLES)).to eq(before_state)
-  end
-
-  it 'migrates nested list Sections and child groups as different placement kinds' do
-    series = group_tag('ぼざろクリーチャーシリーズ')
-    deer = group_tag('洗澡鹿')
-    nijika = group_tag('伊地知ニジカ')
-    child = legacy_group('伊地知ニジカ亜種', <<~MARKDOWN)
-      - ぼざろクリーチャーシリーズ
-        - 伊地知ニジカ亜種:
-          - 洗澡鹿
-    MARKDOWN
-    parent = legacy_group('ぼざろクリーチャーシリーズのキャラクター', <<~MARKDOWN)
-      - ぼざろクリーチャーシリーズ
-        - 伊地知ニジカ
-          - タググループ:伊地知ニジカ亜種
-    MARKDOWN
-
-    migrate_groups
-
-    expect_group_snapshot(
-        child.id, number: 1,
-        members: [series, deer].map { { 'tag_id' => _1.id, 'version_no' => _1.version_no } },
-        placements: [{ 'tag_id' => series.id, 'children' => [
-            { 'section_name' => '伊地知ニジカ亜種', 'description' => nil,
-              'children' => [{ 'tag_id' => deer.id, 'children' => [] }] }] }])
-    expect_group_snapshot(
-        parent.id, number: 1,
-        members: [
-            { 'tag_id' => series.id, 'version_no' => series.version_no },
-            { 'tag_id' => nijika.id, 'version_no' => nijika.version_no },
-            { 'tag_group_id' => child.id, 'version_no' => 1 }],
-        placements: [{ 'tag_id' => series.id, 'children' => [
-            { 'tag_id' => nijika.id, 'children' => [
-                { 'tag_group_id' => child.id, 'children' => [] }] }] }])
-  end
-
-  it 'preserves heading order, group paragraphs and Section descriptions' do
-    names = ['タグ希望', 'キャラクター名希望', '楽曲情報希望', 'bot操作', 'ニジラー情報不詳']
-    tags = names.map { group_tag(_1) }
-    markdown = <<~MARKDOWN
-      全体の説明
-
-      # 要求
-      要求の説明
-
-      - タグ希望
-        - キャラクター名希望
-        - 楽曲情報希望
-
-      # 情報
-      - bot操作
-      - ニジラー情報不詳
-    MARKDOWN
-    page = legacy_group('メタタグ', markdown)
-    expect(page.current_revision.body).to eq(markdown.chomp)
-
-    migrate_groups
-
-    leaves = tags.map { { 'tag_id' => _1.id, 'children' => [] } }
-    leaves.first['children'] = leaves[1..2]
-    expect_group_snapshot(
-        page.id, number: 1, description: '全体の説明',
-        members: tags.map { { 'tag_id' => _1.id, 'version_no' => _1.version_no } },
-        placements: [
-            { 'section_name' => '要求', 'description' => '要求の説明',
-              'children' => [leaves.first] },
-            { 'section_name' => '情報', 'description' => nil,
-              'children' => leaves[3..4] }])
-  end
-
-  it 'leaves Help in the legacy domain' do
-    page = Wiki::Commit.create_legacy_content!(
-        tag_name: create(:tag_name, name: 'Help:移行対象外'),
-        body: 'Help 本文', created_by_user: user)
-    before_state = group_state
-    migrate_groups
-    expect(group_state).to eq(before_state)
-    expect(page.reload.body).to eq('Help 本文')
-  end
-end
diff --git a/backend/spec/factories/tag_names.rb b/backend/spec/factories/tag_names.rb
index 0e98e3b..f5820cc 100644
--- a/backend/spec/factories/tag_names.rb
+++ b/backend/spec/factories/tag_names.rb
@@ -6,6 +6,8 @@ FactoryBot.define do
     auto_generated { false }
     sequence(:name) { |number| "tag-#{ SecureRandom.hex(4) }-#{ number }" }
 
+    association :tag, primary_tag_name: nil
+
     trait :alias do
       primary_flg { false }
     end
diff --git a/backend/spec/factories/tags.rb b/backend/spec/factories/tags.rb
index d4ac59b..a01a84c 100644
--- a/backend/spec/factories/tags.rb
+++ b/backend/spec/factories/tags.rb
@@ -4,7 +4,7 @@ FactoryBot.define do
       primary_name { nil }
       primary_tag_name do
         attributes = primary_name.nil? ? { } : { name: primary_name }
-        build(:tag_name, **attributes)
+        build(:tag_name, tag: nil, **attributes)
       end
     end
 
@@ -12,17 +12,16 @@ FactoryBot.define do
     post_count { 0 }
 
     after(:build) do |tag, evaluator|
+      next unless evaluator.primary_tag_name
+
       evaluator.primary_tag_name.primary_flg = true
+      evaluator.primary_tag_name.tag = tag
       tag.tag_names.target << evaluator.primary_tag_name
     end
 
-    before(:create) do |tag, evaluator|
-      evaluator.primary_tag_name.save!
-      # Compatibility write only; ownership is established through tag_id below.
-      tag.tag_name_id = evaluator.primary_tag_name.id
-    end
-
     after(:create) do |tag, evaluator|
+      next unless evaluator.primary_tag_name
+
       evaluator.primary_tag_name.update!(tag:, primary_flg: true)
 
       Locale.where(deprecated_at: nil).order(:language_code, :created_at, :script_code).to_a
diff --git a/backend/spec/factories/wiki_pages.rb b/backend/spec/factories/wiki_pages.rb
deleted file mode 100644
index 7f5f41a..0000000
--- a/backend/spec/factories/wiki_pages.rb
+++ /dev/null
@@ -1,9 +0,0 @@
-FactoryBot.define do
-  factory :wiki_page do
-    title { "TestPage" }
-    association :created_user, factory: :user
-    association :updated_user, factory: :user
-
-    body { ' ' }
-  end
-end
diff --git a/backend/spec/models/shared_tag_ids_spec.rb b/backend/spec/models/shared_tag_ids_spec.rb
index 96ef653..378eebc 100644
--- a/backend/spec/models/shared_tag_ids_spec.rb
+++ b/backend/spec/models/shared_tag_ids_spec.rb
@@ -1,84 +1,37 @@
 require 'rails_helper'
 
 RSpec.describe 'Shared Tag and ExternalTag IDs', type: :model do
-  include TagGroupRecords
-  let(:user) { create_member_user! }
+  it 'allocates distinct increasing IDs across the two tables' do
+    tag = create(:tag)
+    external = create(:external_tag)
+    next_tag = create(:tag)
 
-  def create_resource resource
-    if resource == :tag
-      Tag.find_or_create_by_tag_name!(Locale.nipponese, 'shared_id_new', category: :general)
-    else
-      ExternalTag.create!(platform: :nico, name: 'shared_id_new')
-    end
+    expect(external.id).to be > tag.id
+    expect(next_tag.id).to be > external.id
   end
 
-  [:tag, :external_tag].each do |resource|
-    it "starts #{ resource } at 1 when both tables are empty" do
-      expect(Tag.count).to eq(0)
-      expect(ExternalTag.count).to eq(0)
-      expect(create_resource(resource).id).to eq(1)
-    end
+  it 'does not reuse physically deleted IDs in either table' do
+    tag = create(:tag)
+    external = create(:external_tag)
+    TagName.where(tag_id: tag.id).delete_all
+    tag.destroy!
+    external.destroy!
 
-    it "allocates #{ resource } above the other table's maximum" do
-      create(:tag, id: resource == :tag ? 1 : 20)
-      create(:external_tag, id: resource == :external_tag ? 1 : 20)
-
-      expect(create_resource(resource).id).to eq(21)
-    end
-
-    it "uses the current maximum after deleting earlier #{ resource } records" do
-      tag = create(:tag, id: 100)
-      TagName.where(tag_id: tag.id).update_all(tag_id: nil)
-      tag.destroy!
-      create(:external_tag, id: 200).destroy!
-      expect(Tag.unscoped.count).to eq(0)
-      expect(ExternalTag.unscoped.count).to eq(0)
-      expect(create_resource(resource).id).to eq(1)
-    end
-
-    it "preserves legacy overlaps and gaps when creating #{ resource }" do
-      [1, 2, 5].each { create(:tag, id: _1) }
-      [1, 3, 8].each { create(:external_tag, id: _1) }
-      tags = Tag.order(:id).map(&:attributes)
-      external_tags = ExternalTag.order(:id).map(&:attributes)
-
-      record = create_resource(resource)
-
-      aggregate_failures do
-        expect(record.id).to eq(9)
-        expect(Tag.where(id: [1, 2, 5]).order(:id).map(&:attributes)).to eq(tags)
-        expect(ExternalTag.where(id: [1, 3, 8]).order(:id).map(&:attributes)).to eq(external_tags)
-        expect(Tag.exists?(id: 3)).to be(false)
-        expect(ExternalTag.exists?(id: 2)).to be(false)
-      end
-    end
-
-    it "ignores the description and group ID space when creating #{ resource }" do
-      tag = create(:tag, id: 1)
-      create(:external_tag, id: 2)
-      TagDescription.create!(id: 100, tag:, language_code: 'ja', body: '', version_no: 1)
-      seed_group(name: 'separate_space', id: 200)
-
-      expect(create_resource(resource).id).to eq(3)
-    end
+    expect(create(:tag).id).to be > external.id
+    expect(create(:external_tag).id).to be > external.id
   end
 
-  it 'preserves overlapping IDs during updates without rewriting the other resource' do
-    tag = create(:tag, id: 5)
-    external = create(:external_tag, id: 5)
+  it 'retains existing overlapping IDs without renumbering on update or insert' do
+    tag = create(:tag)
+    external = create(:external_tag)
+    external.update_columns(id: tag.id)
     tag.update!(category: :meta)
     external.update!(name: 'updated_external')
+    before_tag = tag.reload.attributes
+    before_external = external.reload.attributes
 
-    expect(tag.reload.id).to eq(5)
-    expect(external.reload.id).to eq(5)
-    expect(tag.category).to eq('meta')
-    expect(external.name).to eq('updated_external')
-    expect(Tag.count).to eq(1)
-    expect(ExternalTag.count).to eq(1)
-  end
-
-  it 'allocates distinct IDs for successive creations across both tables' do
-    records = [:tag, :external_tag].map { create_resource(_1) }
-    expect(records.map(&:id)).to eq([1, 2])
+    expect(create(:tag).id).to be > tag.id
+    expect(tag.reload.attributes).to eq(before_tag)
+    expect(external.reload.attributes).to eq(before_external)
   end
 end
diff --git a/backend/spec/models/tag_group_spec.rb b/backend/spec/models/tag_group_spec.rb
new file mode 100644
index 0000000..ee52647
--- /dev/null
+++ b/backend/spec/models/tag_group_spec.rb
@@ -0,0 +1,23 @@
+require 'rails_helper'
+
+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:)
+  end
+
+  it 'retains version IDs and snapshots after destroying an empty group' do
+    group = create_group(name: 'history owner')
+    versions = group.versions.order(:version_no).map(&:attributes)
+
+    expect { group.destroy! }.to change(described_class, :count).by(-1)
+        .and change(TagGroupVersion, :count).by(0)
+
+    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'))))
+        .to include('id' => group.id, 'name' => 'history owner', 'members' => [])
+  end
+
+end
diff --git a/backend/spec/models/tag_name_sanitisation_rule_spec.rb b/backend/spec/models/tag_name_sanitisation_rule_spec.rb
index 9cebc51..cec475d 100644
--- a/backend/spec/models/tag_name_sanitisation_rule_spec.rb
+++ b/backend/spec/models/tag_name_sanitisation_rule_spec.rb
@@ -98,25 +98,6 @@ RSpec.describe TagNameSanitisationRule, type: :model do
       end
     end
 
-    context 'when the source tag_name has a tag and the existing one has no tag' do
-      let!(:existing) { create(:tag_name, name: 'foobar') }
-      let!(:source_tag) { create(:tag, primary_name: 'tmp', category: :general) }
-      let!(:source_tag_name_id) { primary_tag_name_for(source_tag, 'ja').id }
-
-      before do
-        primary_tag_name_for(source_tag, 'ja').update_columns(
-            name: 'foo_bar', updated_at: Time.current)
-      end
-
-      it 'moves the tag to the existing tag_name' do
-        described_class.apply!
-        expect(existing.reload).to have_attributes(
-            tag_id: source_tag.id, language_code: 'ja', primary_flg: true)
-        expect(primary_tag_name_for(source_tag, 'ja')).to eq(existing)
-        expect(primary_tag_name_for(source_tag.reload, 'ja')).to eq(existing)
-        expect(TagName.unscoped.exists?(source_tag_name_id)).to be(false)
-      end
-    end
 
     context 'when the sanitised name is an alias of an existing tag' do
       let!(:existing_tag) { create(:tag) }
diff --git a/backend/spec/models/tag_name_spec.rb b/backend/spec/models/tag_name_spec.rb
index 8239d65..3d8ff38 100644
--- a/backend/spec/models/tag_name_spec.rb
+++ b/backend/spec/models/tag_name_spec.rb
@@ -22,16 +22,23 @@ RSpec.describe TagName, type: :model do
     expect(duplicate.errors.of_kind?(:name, :taken)).to be(true)
   end
 
-  it 'creates Nipponese factory names without requiring a tag' do
+  it 'creates Nipponese factory names with an owning tag' do
     name = create(:tag_name)
 
     expect(name.reload).to have_attributes(
         language_code: 'ja', script_code: 'Jpan', primary_flg: true,
-        auto_generated: false, tag_id: nil)
+        auto_generated: false, tag_id: name.tag.id)
+  end
+
+  it 'rejects an ownerless name at model and database boundaries' do
+    name = build(:tag_name, tag: nil)
+    expect(name).to be_invalid
+    expect { name.save!(validate: false) }.to raise_error(ActiveRecord::NotNullViolation)
   end
 
   it 'defaults ordinary persisted human names to confirmed provenance' do
-    name = described_class.create!(name: 'ordinary_human_name', language_code: 'ja',
+    name = described_class.create!(tag: create(:tag, primary_tag_name: nil),
+                                   name: 'ordinary_human_name', language_code: 'ja',
                                    script_code: 'Jpan', primary_flg: true)
 
     expect(name.reload.auto_generated).to be(false)
@@ -46,7 +53,7 @@ RSpec.describe TagName, type: :model do
     expect(name.tag).to eq(tag)
     expect(described_class.find_by!(tag_id: tag.id, language_code: 'ja', primary_flg: true))
         .to eq(name)
-    expect(tag.reload.tag_name_id).to eq(name.id)
+    expect(tag.reload.tag_name('ja')&.id).to eq(name.id)
   end
 
   it 'creates a complete ordinary tag factory under the active Nipponese language' do
@@ -96,19 +103,14 @@ RSpec.describe TagName, type: :model do
   end
 
   describe '.canonicalise' do
-    it 'leaves detached aliases unchanged' do
-      create(:tag_name, :alias, name: 'detached_alias')
 
-      expect(described_class.canonicalise(Locale.nipponese, ['detached_alias']))
-          .to eq(['detached_alias'])
-    end
 
-    it 'does not resolve a detached alias through another detached primary' do
-      create(:tag_name, :alias, name: 'detached_alias')
-      create(:tag_name, name: 'unrelated_detached_primary')
+    it 'resolves an alias to its owning primary name' do
+      tag = create(:tag, primary_name: 'canonical')
+      create(:tag_name, :alias, tag:, name: 'alias')
 
-      expect(described_class.canonicalise(Locale.nipponese, ['detached_alias']))
-          .to eq(['detached_alias'])
+      expect(described_class.canonicalise(Locale.nipponese, ['alias', 'unknown']))
+          .to eq(['canonical', 'unknown'])
     end
 
     it 'resolves the primary name of the alias language on the same tag' do
@@ -119,7 +121,7 @@ RSpec.describe TagName, type: :model do
       english_primary.update!(name: 'english_primary', auto_generated: false)
       english_alias = create(:tag_name, :alias, tag:, name: 'english_alias',
                                                  language_code: 'en', script_code: 'Latn')
-      representative_id = tag.tag_name_id
+      representative_id = tag.tag_name('ja')&.id
 
       primary = described_class.find_by!(tag_id: english_alias.tag_id,
                                          language_code: english_alias.language_code,
@@ -128,7 +130,7 @@ RSpec.describe TagName, type: :model do
       expect(primary).to eq(english_primary)
       expect(described_class.canonicalise(locale, [english_alias.name]))
           .to eq([english_primary.name])
-      expect(tag.reload.tag_name_id).to eq(representative_id)
+      expect(tag.reload.tag_name('ja')&.id).to eq(representative_id)
     end
 
     it 'resolves only aliases in the requested language' do
diff --git a/backend/spec/models/tag_spec.rb b/backend/spec/models/tag_spec.rb
index 0cc9d8c..2bff7fa 100644
--- a/backend/spec/models/tag_spec.rb
+++ b/backend/spec/models/tag_spec.rb
@@ -1,6 +1,7 @@
 require 'rails_helper'
 
 RSpec.describe Tag, type: :model do
+  include WikiRecords
   describe '#has_description?' do
     let(:tag) { create(:tag) }
 
@@ -14,12 +15,6 @@ RSpec.describe Tag, type: :model do
       expect(tag.has_description?(language_code: 'ja')).to be(false)
     end
 
-    it 'does not use a Wiki page as evidence of a description' do
-      user = create_member_user!
-      Wiki::Commit.create_legacy_content!(tag_name: tag.tag_name('ja'), body: 'legacy',
-                                          created_by_user: user)
-      expect(tag.has_description?(language_code: 'ja')).to be(false)
-    end
 
     it 'reuses preloaded descriptions without reading Wiki or querying again' do
       TagDescription.create!(tag:, language_code: 'ja', body: '', version_no: 1)
@@ -334,38 +329,7 @@ RSpec.describe Tag, type: :model do
             .where(tag_names: { name: 'atomic_english_name' })).to be_empty
       end
 
-      it 'keeps a detached requested name detached if generation fails' do
-        pending '日本語以外の Locale 有効化は別課題で実装する'
-        locale
-        detached = create(:tag_name, :alias, name: 'atomic_detached',
-                                           language_code: 'en', script_code: 'Latn')
-        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, detached.name, category: :general)
-        }.to raise_error('generation failed')
-
-        expect(described_class.count).to eq(original_tag_count)
-        expect(detached.reload).to have_attributes(tag_id: nil, primary_flg: false)
-      end
-
-      it 'promotes a detached alias into the requested primary name' do
-        pending '日本語以外の Locale 有効化は別課題で実装する'
-        locale
-        detached = create(:tag_name, :alias, name: 'detached_english',
-                                           language_code: 'en', script_code: 'Latn')
-
-        tag = described_class.find_or_create_by_tag_name!(
-            locale, detached.name, category: :general)
-
-        expect(detached.reload).to have_attributes(
-            tag_id: tag.id, primary_flg: true, canonical_id: nil,
-            auto_generated: false)
-        expect(TagName.where(tag:, language_code: 'en', primary_flg: true))
-            .to contain_exactly(detached)
-      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'
@@ -390,7 +354,7 @@ RSpec.describe Tag, type: :model 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_id
+        representative_id = tag.tag_name('ja')&.id
         english = primary_tag_name_for(tag, 'en')
         english.update!(name: 'english_primary', auto_generated: false)
 
@@ -398,7 +362,7 @@ RSpec.describe Tag, type: :model do
             locale, english.name, category: :general)
 
         expect(found).to eq(tag)
-        expect(tag.reload.tag_name_id).to eq(representative_id)
+        expect(tag.reload.tag_name('ja')&.id).to eq(representative_id)
         expect(english.reload.tag_id).to eq(tag.id)
       end
 
@@ -430,22 +394,10 @@ RSpec.describe Tag, type: :model do
       expect(primary_tag_name_for(tag, 'ja').auto_generated).to be(false)
     end
 
-    it 'promotes a detached Nipponese alias into a human-confirmed primary' do
-      detached = create(:tag_name, :alias, name: 'detached_nipponese')
-
-      tag = described_class.find_or_create_by_tag_name!(
-          Locale.nipponese, detached.name, category: :general)
-
-      expect(detached.reload).to have_attributes(
-          tag_id: tag.id, primary_flg: true, canonical_id: nil,
-          auto_generated: false)
-      expect(TagName.where(tag:, language_code: 'ja', primary_flg: true))
-          .to contain_exactly(detached)
-    end
 
     it 'reuses the owning tag for an alias without changing its category' do
       tag = create(:tag, category: :character)
-      representative_id = tag.tag_name_id
+      representative_id = tag.tag_name('ja')&.id
       alias_name = create(:tag_name, :alias, name: 'lookup_alias', tag:)
       expect(alias_name.reload).to have_attributes(
           tag_id: tag.id,
@@ -459,7 +411,7 @@ RSpec.describe Tag, type: :model do
 
       expect(found).to eq(tag)
       expect(found.category).to eq('character')
-      expect(tag.reload.tag_name_id).to eq(representative_id)
+      expect(tag.reload.tag_name('ja')&.id).to eq(representative_id)
     end
 
     it 'reuses the owning tag through another alias' do
@@ -683,7 +635,7 @@ RSpec.describe Tag, type: :model do
       let!(:wiki_page) do
         admin = create_admin_user!
 
-        Wiki::Commit.create_content!(
+        seed_description(
             tag_name: source_tag_name,
             body: 'source wiki body',
             created_by_user: admin,
diff --git a/backend/spec/requests/materials_spec.rb b/backend/spec/requests/materials_spec.rb
index b891faa..0a2ea89 100644
--- a/backend/spec/requests/materials_spec.rb
+++ b/backend/spec/requests/materials_spec.rb
@@ -222,28 +222,27 @@ RSpec.describe 'Materials API', type: :request do
       expect(queries).to be_empty
     end
 
-    it 'reads the description even when the legacy revision has different content' do
-      page = seed_wiki_page(tag_name: tag.tag_name('ja'), body: 'legacy body',
+    it 'reads the description even when the stored version has different content' do
+      page = seed_description(tag_name: tag.tag_name('ja'), body: 'legacy body',
                             created_by_user: member_user)
       TagDescription.find_by!(tag_id: tag.id, language_code: 'ja')
           .update!(body: 'description body')
       get_material_without_legacy_reads
       expect(json.fetch('wiki_page_body')).to eq('description body')
-      expect(page.current_revision.body).to eq('legacy body')
+      expect(current_description_version(page).body).to eq('legacy body')
     end
 
     it 'uses tag_id rather than description ID without a Wiki page or TagName' do
-      description = TagDescription.create!(id: tag.id + 1000, tag:, language_code: 'ja',
+      description = TagDescription.create!(tag:, language_code: 'ja',
                                            body: 'independent body', version_no: 1)
-      tag.tag_names.update_all(tag_id: nil)
+      tag.tag_names.delete_all
       get_material_without_legacy_reads
-      expect(description.id).not_to eq(tag.id)
       expect(json.fetch('wiki_page_body')).to eq('independent body')
       expect(json.fetch('tag').fetch('has_wiki')).to be(true)
     end
 
-    it 'returns nil when only legacy Wiki content exists' do
-      seed_wiki_page(tag_name: tag.tag_name('ja'), body: 'legacy only',
+    it 'returns nil when only description history remains' do
+      seed_description(tag_name: tag.tag_name('ja'), body: 'legacy only',
                      created_by_user: member_user)
       TagDescription.where(tag_id: tag.id).delete_all
       get_material_without_legacy_reads
diff --git a/backend/spec/requests/tag_description_wiki_spec.rb b/backend/spec/requests/tag_description_wiki_spec.rb
index 02b1184..5a52675 100644
--- a/backend/spec/requests/tag_description_wiki_spec.rb
+++ b/backend/spec/requests/tag_description_wiki_spec.rb
@@ -4,34 +4,21 @@ RSpec.describe 'Tag description Wiki compatibility', type: :request do
   include WikiRecords
   let!(:user) { create_member_user! }
   let!(:tag_name) { create(:tag_name, name: 'description_contract') }
-  let!(:page) do
-    seed_wiki_page(
-        tag_name:, body: 'old-revision', created_by_user: user)
-  end
-  let!(:revisions) do
-    first = page.current_revision
-    second = Wiki::Commit.legacy_content!(page:, body: 'old-second', created_user: user)
-    third = Wiki::Commit.legacy_content!(page:, body: 'old-third', created_user: user)
-    [first, second, third]
-  end
-  let!(:tag) { create(:tag, primary_tag_name: tag_name) }
+  let!(:tag) { tag_name.tag }
   let!(:versions) do
-    revisions.each_with_index.map do |revision, index|
+    ['A', 'A', 'new-version'].each_with_index.map do |body, index|
       TagDescriptionVersion.create!(
-          id: revision.id, tag_id: tag.id, language_code: 'ja',
-          version_no: index + 1, event_type: index.zero? ? 'create' : 'update',
-          body: index == 2 ? 'new-version' : 'A',
-          created_by_user_id: user.id, created_at: revision.created_at)
+          tag_id: tag.id, language_code: 'ja', version_no: index + 1,
+          event_type: index.zero? ? 'create' : 'update', body:,
+          created_by_user_id: user.id, created_at: Time.current)
     end
   end
   let!(:description) do
     TagDescription.create!(
-        id: page.id, tag:, language_code: 'ja', version_no: 3, body: 'new',
+        tag:, language_code: 'ja', version_no: 3, body: 'new',
         created_by_user_id: user.id, updated_by_user_id: user.id)
   end
 
-  before { page.update_columns(body: 'old') }
-
   # Observe real SELECTs, including cached queries, only during the request.
   def without_legacy_reads
     queries = []
@@ -70,7 +57,7 @@ RSpec.describe 'Tag description Wiki compatibility', type: :request do
     it 'does not fall back to a revision absent from new history' do
       versions.first.destroy!
       without_legacy_reads do
-        get "/wiki/#{ description.id }", params: { version: revisions.first.id }
+        get "/wiki/#{ description.id }", params: { version: versions.first.id }
       end
       expect(response).to have_http_status(:not_found)
     end
@@ -132,16 +119,6 @@ RSpec.describe 'Tag description Wiki compatibility', type: :request do
                              'pred' => versions.first.id, 'succ' => versions.last.id)
     end
 
-    it 'ignores changes to same-title legacy content and revision metadata' do
-      get "/wiki/title/#{ tag_name.name }"
-      original = json
-      page.update_columns(body: 'changed legacy body')
-      revisions.last.update_columns(message: 'legacy message', created_at: 1.day.ago)
-      revisions.last.wiki_lines.update_all(body: 'changed legacy revision')
-      get "/wiki/title/#{ tag_name.name }"
-      expect(json).to eq(original)
-      expect(json.fetch('body')).to eq('new')
-    end
   end
 
   describe 'exists' do
@@ -155,28 +132,6 @@ RSpec.describe 'Tag description Wiki compatibility', type: :request do
       expect(response).to have_http_status(:no_content)
     end
 
-    context 'without a legacy page' do
-      before do
-        WikiVersion.where(wiki_page_id: page.id).delete_all
-        page.destroy!
-      end
-
-      it 'recognises the description ID alone' do
-        get "/wiki/#{ description.id }/exists"
-        expect(response).to have_http_status(:no_content)
-      end
-
-      it 'recognises the TagName alone' do
-        get "/wiki/title/#{ tag_name.name }/exists"
-        expect(response).to have_http_status(:no_content)
-      end
-
-      it 'shows the description by title' do
-        get "/wiki/title/#{ tag_name.name }"
-        expect(response).to have_http_status(:ok)
-        expect(json).to include('body' => 'new', 'revision_id' => versions.last.id)
-      end
-    end
   end
 
   describe 'diff' do
@@ -229,39 +184,8 @@ RSpec.describe 'Tag description Wiki compatibility', type: :request do
                                                       'title' => tag_name.name)
     end
 
-    it 'ignores legacy-only revisions and metadata changes' do
-      get '/wiki/changes', params: { id: description.id }
-      original = json
-      revisions.first.update_columns(message: 'legacy changed', created_at: 1.day.ago)
-      WikiRevision.create!(
-          wiki_page: page, created_user: user, kind: :content,
-          tree_sha256: Digest::SHA256.hexdigest('legacy only'), lines_count: 0)
-      get '/wiki/changes', params: { id: description.id }
-      expect(json).to eq(original)
-      expect(json.map { |row| row.fetch('revision_id') }).to eq(versions.reverse.map(&:id))
-    end
   end
 
-  describe 'mixed changes' do
-    it 'excludes unmigrated history and migrated legacy-only revisions' do
-      legacy_page = seed_wiki_page(
-          tag_name: create(:tag_name, name: 'Help_mixed'),
-          body: 'help', created_by_user: user)
-      legacy_revision = legacy_page.current_revision
-      extra = WikiRevision.create!(
-          wiki_page: page, created_user: user, kind: :content,
-          tree_sha256: Digest::SHA256.hexdigest('legacy only'), lines_count: 0)
-
-      get '/wiki/changes'
-      expect(response).to have_http_status(:ok)
-      migrated = json.select { |row| row.fetch('wiki_page').fetch('id') == description.id }
-      expect(migrated.map { |row| row.fetch('revision_id') }).to eq(versions.reverse.map(&:id))
-      expect(json.map { |row| row.fetch('revision_id') }).not_to include(extra.id)
-      expect(json).not_to include(include(
-          'revision_id' => legacy_revision.id,
-          'wiki_page' => include('id' => legacy_page.id, 'title' => 'Help_mixed')))
-    end
-  end
 
   describe 'index' do
     [nil, 'description_contract'].each do |title|
diff --git a/backend/spec/requests/tag_description_wiki_write_spec.rb b/backend/spec/requests/tag_description_wiki_write_spec.rb
index 3b3af9d..0658d7c 100644
--- a/backend/spec/requests/tag_description_wiki_write_spec.rb
+++ b/backend/spec/requests/tag_description_wiki_write_spec.rb
@@ -1,280 +1,92 @@
 require 'rails_helper'
 
-RSpec.describe 'Tag description Wiki dual writes', type: :request do
+RSpec.describe 'Tag description Wiki facade writes', type: :request do
   include WikiRecords
   let!(:user) { create_member_user! }
-  let!(:tag_name) { create(:tag_name, name: 'description_write') }
-  let(:tag) { create(:tag, primary_tag_name: tag_name) }
+  let!(:tag) { create(:tag, primary_name: 'description_write') }
   let(:headers) { { 'X-Transfer-Code' => user.inheritance_code } }
 
   def stored_state
-    [WikiPage, WikiRevision, WikiVersion, TagDescription, TagDescriptionVersion,
-     TagName, TagVersion].map do |model|
+    [Tag, TagName, TagVersion, TagDescription, TagDescriptionVersion].map do |model|
       model.order(:id).map(&:attributes)
     end
   end
 
-  # Fail after a real INSERT/UPDATE, exercising rollback rather than a mock write.
-  def fail_save model
-    failure = Class.new(StandardError)
-    callback = ->(_record) { raise failure, 'injected persistence failure' }
-    model.set_callback(:save, :after, callback)
-    expect { yield }.to raise_error(failure)
-  ensure
-    model.skip_callback(:save, :after, callback)
-  end
-
-  describe 'POST /wiki' do
-    before { tag }
-
-    def create_description
-      post '/wiki', params: { title: tag_name.name, body: 'initial', message: 'create' },
-           headers: headers
-    end
-
-    it 'creates a description with matching Wiki content and histories' do
-      expect { create_description }
-          .to change(WikiPage, :count).by(1)
-          .and change(WikiRevision, :count).by(1)
-          .and change(WikiVersion, :count).by(1)
-          .and change(TagDescription, :count).by(1)
-          .and change(TagDescriptionVersion, :count).by(1)
-      expect(response).to have_http_status(:created)
-      description = TagDescription.find_by!(tag_id: tag.id, language_code: 'ja')
-      expect(description).to have_attributes(body: 'initial', version_no: 1)
-      page = WikiPage.find_by!(tag_name:)
-      expect(page.body).to eq(description.body)
-      expect(page.current_revision.body).to eq(description.body)
-      expect(page.wiki_versions.sole.body).to eq(description.body)
-      expect(json.fetch('id')).to eq(description.id)
-      expect(TagDescriptionVersion.find_by!(tag_id: tag.id, language_code: 'ja'))
-          .to have_attributes(body: 'initial', version_no: 1, created_by_user_id: user.id)
-    end
-
-    it 'reuses an existing compatibility page and synchronises its histories' do
-      page = Wiki::Commit.create_legacy_content!(
-          tag_name:, body: 'legacy', created_by_user: user)
-      expect { create_description }
-          .to change(WikiPage, :count).by(0)
-          .and change(WikiRevision, :count).by(1)
-          .and change(WikiVersion, :count).by(1)
-      expect(response).to have_http_status(:created)
-      description = TagDescription.find_by!(tag_id: tag.id)
-      expect(page.reload.body).to eq(description.body)
-      expect(TagDescriptionVersion.find(page.current_revision.id).body).to eq(page.body)
-    end
-
-    ['missing_description', 'orphan_description'].each do |title|
-      it "rejects the bare title #{ title } without writing any resource" do
-        create(:tag_name, name: title) if title == 'orphan_description'
-        before_state = stored_state
-
-        post '/wiki', params: { title:, body: 'initial' }, headers: headers
-
-        expect(response).to have_http_status(:unprocessable_entity)
-        expect(json).to include('type' => 'validation_error')
-        expect(stored_state).to eq(before_state)
-      end
-    end
-
-    [false, true].each do |linked|
-      it "rejects namespaced creation with Tag present: #{ linked }" do
-        name = create(:tag_name, name: 'Help:frozen')
-        create(:tag, primary_tag_name: name) if linked
-        before_state = stored_state
-        post '/wiki', params: { title: name.name, body: 'legacy' }, headers: headers
-        expect(response.status).to be_between(400, 499)
-        expect(stored_state).to eq(before_state)
-      end
-    end
-
-    [WikiPage, WikiRevision, WikiVersion, TagDescription, TagDescriptionVersion].each do |model|
-      it "rolls back new description creation when #{ model.name } persistence fails" do
-        before_state = stored_state
-        aggregate_failures do
-          fail_save(model) { create_description }
-          expect(stored_state).to eq(before_state)
-        end
-      end
-    end
-  end
-
-  it 'creates missing compatibility data without writing an ID-colliding Help page' do
-    description = TagDescription.create!(
-        id: 500, tag:, language_code: 'ja', body: 'before', version_no: 1)
-    help = WikiPage.create!(id: description.id,
-                            tag_name: create(:tag_name, name: 'Help:unrelated'),
-                            body: 'unrelated', created_user: user, updated_user: user)
-    Wiki::Commit.legacy_content!(page: help, body: help.body, created_user: user)
-    before_help = help.attributes
+  it 'creates a native description and exposes its version ID as revision ID' do
     expect do
-      put "/wiki/#{ description.id }", params: { title: tag_name.name, body: 'after' },
-          headers: headers
-    end.to change(WikiPage, :count).by(1)
-        .and change(WikiRevision, :count).by(1)
-        .and change(WikiVersion, :count).by(1)
-    expect(response).to have_http_status(:ok)
-    expect(description.reload).to have_attributes(id: 500, body: 'after')
-    expect(help.reload.attributes).to eq(before_help)
-    compatibility = WikiPage.find_by!(tag_name:)
-    expect(compatibility.body).to eq(description.body)
-    expect(compatibility.current_revision.body).to eq(description.body)
+      post '/wiki', params: { title: tag.name('ja'), body: 'initial' }, headers: headers
+    end.to change(TagDescription, :count).by(1)
+        .and change(TagDescriptionVersion, :count).by(1)
+    expect(response).to have_http_status(:created)
+    description = TagDescription.find(json.fetch('id'))
+    expect(description).to have_attributes(tag_id: tag.id, body: 'initial', version_no: 1)
+    get "/wiki/#{ description.id }"
+    expect(json.fetch('revision_id')).to eq(current_description_version(description).id)
   end
 
-  describe 'PUT /wiki/:id' do
-    let!(:page) do
-      tag
-      seed_wiki_page(
-          tag_name:, body: 'before', created_by_user: user)
-    end
-    let!(:first_revision) { page.current_revision }
-
+  context 'with an existing description' do
     let!(:description) do
-      TagDescription.find_by!(tag_id: tag.id, language_code: 'ja')
+      TagDescriptionOperation.create!(tag:, body: 'before', created_by_user: user)
     end
+    let!(:first_version) { current_description_version(description) }
 
-    def update_description body: 'after', title: tag_name.name, base: first_revision.id
-      put "/wiki/#{ page.id }",
-          params: { title:, body:, message: 'edit', base_revision_id: base },
+    def update_description body: 'after', title: tag.name('ja'), base: first_version.id
+      put "/wiki/#{ description.id }", params: { title:, body:, base_revision_id: base },
           headers: headers
     end
 
-    it 'increments the independent description sequence and shares revision identity' do
-      expect(page.reload.version_no).to eq(1)
-      expect(description.version_no).to eq(1)
-      expect { update_description }
-          .to change(WikiPage, :count).by(0)
-          .and change(WikiRevision, :count).by(1)
-          .and change(WikiVersion, :count).by(1)
-          .and change(TagDescriptionVersion, :count).by(1)
-      expect(response).to have_http_status(:ok)
-
-      revision = page.reload.current_revision
-      version = TagDescriptionVersion.find(revision.id)
-      expect(description.reload).to have_attributes(body: 'after', version_no: 2)
-      expect(version).to have_attributes(
-          body: 'after', version_no: 2, event_type: 'update', created_by_user_id: user.id)
-      expect(page).to have_attributes(body: 'after', version_no: 2)
-      expect(revision.body).to eq(version.body)
-      expect(page.wiki_versions.order(:version_no).last.body).to eq(version.body)
-    end
-
-    it 'uses description identity even when its Wiki TagName no longer owns the Tag' do
-      tag_name.update_columns(tag_id: nil)
-
-      expect { update_description }
-          .to change(WikiPage, :count).by(0)
-          .and change(WikiRevision, :count).by(1)
-          .and change(WikiVersion, :count).by(1)
-          .and change(TagDescriptionVersion, :count).by(1)
-
+    it 'records a body change without changing resource identity or old history' do
+      snapshot = first_version.attributes
+      expect { update_description }.to change(TagDescriptionVersion, :count).by(1)
       expect(response).to have_http_status(:ok)
       expect(description.reload).to have_attributes(body: 'after', version_no: 2)
-      expect(TagDescriptionVersion.find(page.reload.current_revision.id))
-          .to have_attributes(tag_id: tag.id, body: 'after', version_no: 2)
+      expect(first_version.reload.attributes).to eq(snapshot)
+      expect(current_description_version(description)).to have_attributes(
+          body: 'after', event_type: 'update', created_by_user_id: user.id)
     end
 
-    it 'does not add body history for a title-only update' do
-      revision_count = WikiRevision.count
-      wiki_version_count = WikiVersion.count
-      description_version_count = TagDescriptionVersion.count
-      wiki_version_no = page.reload.version_no
-      description_version_no = description.version_no
-      current_revision_id = page.current_revision.id
-      page_state = page.attributes
-      description_state = description.attributes
-
-      update_description(body: 'before', title: 'description_renamed')
-
-      expect(response).to have_http_status(:ok)
-      expect(tag_name.reload.name).to eq('description_renamed')
-      expect(WikiRevision.count).to eq(revision_count)
-      expect(WikiVersion.count).to eq(wiki_version_count)
-      expect(TagDescriptionVersion.count).to eq(description_version_count)
-      expect(page.reload).to have_attributes(body: 'before', version_no: wiki_version_no)
-      expect(page.current_revision.id).to eq(current_revision_id)
-      expect(page.reload.attributes).to eq(page_state)
-      expect(description.reload).to have_attributes(
-          body: 'before', version_no: description_version_no)
-      expect(description.reload.attributes).to eq(description_state)
-    end
-
-    it 'does not add body history for a TagName rename through tags' do
-      revision_count = WikiRevision.count
-      wiki_version_count = WikiVersion.count
-      description_version_count = TagDescriptionVersion.count
-      page_version_no = page.reload.version_no
-      current_revision_id = page.current_revision.id
-
-      patch "/tags/#{ tag.id }",
-            params: { name: 'description_tag_renamed' },
-            headers: headers
-
-      expect(response).to have_http_status(:ok)
-      expect(tag_name.reload.name).to eq('description_tag_renamed')
-      expect(WikiRevision.count).to eq(revision_count)
-      expect(WikiVersion.count).to eq(wiki_version_count)
-      expect(TagDescriptionVersion.count).to eq(description_version_count)
-      expect(page.reload.version_no).to eq(page_version_no)
-      expect(page.current_revision.id).to eq(current_revision_id)
-      expect(description.reload).to have_attributes(
-          body: 'before', version_no: 1)
-    end
-
-    it 'keeps both systems and the title unchanged on a stale revision conflict' do
-      update_description(body: 'current body', base: first_revision.id)
-      expect(response).to have_http_status(:ok)
-
-      stale_revision_id = first_revision.id
-      before_state = stored_state
-
-      update_description(
-          body: 'conflicting body',
-          title: 'conflicting_rename',
-          base: stale_revision_id)
-
-      expect(response).to have_http_status(:conflict)
-      expect(stored_state).to eq(before_state)
-      expect(tag_name.reload.name).not_to eq('conflicting_rename')
-    end
-
-    [WikiPage, WikiRevision, WikiVersion, TagDescription, TagDescriptionVersion].each do |model|
-      it "rolls back both systems when #{ model.name } persistence fails" do
+    ['before', "before\r\n\r\n"].each do |body|
+      it "does not write for normalised-equivalent body #{ body.inspect }" do
         before_state = stored_state
-        aggregate_failures do
-          fail_save(model) do
-            update_description(body: 'rollback body', title: 'rollback_rename')
-          end
-          expect(stored_state).to eq(before_state)
-        end
+        update_description(body:)
+        expect(response).to have_http_status(:ok)
+        expect(stored_state).to eq(before_state)
       end
     end
 
-    [['identical body', 'before'],
-     ['normalised-equivalent body', "before\n\n"]].each do |label, body|
-      it "does not write histories for #{ label }" do
-        before_state = stored_state
-        page_state = page.reload.attributes
-        description_state = description.reload.attributes
-        current_revision_id = page.current_revision.id
-        wiki_lines = WikiLine.order(:id).map(&:attributes)
-        revision_lines = WikiRevisionLine.order(:id).map(&:attributes)
-        page_version_no = page.version_no
-        description_version_no = description.version_no
-
-        update_description(body:)
+    it 'records a title-only edit in Tag history without adding body history' do
+      snapshot = description.attributes
+      expect { update_description(body: 'before', title: 'renamed') }
+          .to change(TagVersion, :count).by(2)
+          .and change(TagDescriptionVersion, :count).by(0)
+      expect(response).to have_http_status(:ok)
+      expect(tag.reload.name('ja')).to eq('renamed')
+      expect(description.reload.attributes).to eq(snapshot)
+    end
 
+    ['conflicting body', 'after'].each do |body|
+      it "rejects a stale revision even for #{ body } without a partial rename" do
+        update_description
         expect(response).to have_http_status(:ok)
-        expect(WikiRevision.count).to eq(before_state[1].length)
-        expect(WikiVersion.count).to eq(before_state[2].length)
-        expect(TagDescriptionVersion.count).to eq(before_state[4].length)
-        expect(page.reload.version_no).to eq(page_version_no)
-        expect(description.reload.version_no).to eq(description_version_no)
-        expect(page.current_revision.id).to eq(current_revision_id)
-        expect(page.reload.attributes).to eq(page_state)
-        expect(description.reload.attributes).to eq(description_state)
-        expect(WikiLine.order(:id).map(&:attributes)).to eq(wiki_lines)
-        expect(WikiRevisionLine.order(:id).map(&:attributes)).to eq(revision_lines)
+        before_state = stored_state
+        update_description(body:, title: 'conflicting rename')
+        expect(response).to have_http_status(:conflict)
+        expect(stored_state).to eq(before_state)
+      end
+    end
+
+    [TagDescription, TagDescriptionVersion].each do |model|
+      it "rolls back the rename and body after #{ model.name } persistence fails" do
+        before_state = stored_state
+        failure = Class.new(StandardError)
+        callback = ->(_record) { raise failure }
+        model.set_callback(:save, :after, callback)
+        begin
+          expect { update_description(title: 'rollback rename') }.to raise_error(failure)
+          expect(stored_state).to eq(before_state)
+        ensure
+          model.skip_callback(:save, :after, callback)
+        end
       end
     end
   end
diff --git a/backend/spec/requests/tag_descriptions_spec.rb b/backend/spec/requests/tag_descriptions_spec.rb
index 7901144..7fecf45 100644
--- a/backend/spec/requests/tag_descriptions_spec.rb
+++ b/backend/spec/requests/tag_descriptions_spec.rb
@@ -1,6 +1,8 @@
 require 'rails_helper'
 
 RSpec.describe 'Tag description native API', type: :request do
+  include WikiRecords
+  include TagGroupRecords
   let!(:author) { create_member_user! }
   let(:editor) { create(:user, :member, name: 'description editor') }
   let(:tag_name) { create(:tag_name, name: 'native_description') }
@@ -9,8 +11,7 @@ RSpec.describe 'Tag description native API', type: :request do
   let(:endpoint) { "/tags/#{ tag.id }/description" }
 
   def stored_state
-    [WikiPage, WikiRevision, WikiVersion, TagDescription, TagDescriptionVersion,
-     WikiLine, WikiRevisionLine, TagName, TagVersion].map do |model|
+    [TagDescription, TagDescriptionVersion, TagName, TagVersion].map do |model|
       model.order(:id).map(&:attributes)
     end
   end
@@ -84,7 +85,7 @@ RSpec.describe 'Tag description native API', type: :request do
   describe 'native reads' do
     let!(:description) do
       TagDescription.create!(
-          id: tag.id + 1_000_000, tag:, language_code: 'ja', body: 'native current',
+          tag:, language_code: 'ja', body: 'native current',
           version_no: 1, created_by_user_id: author.id, updated_by_user_id: editor.id)
     end
     let!(:version) do
@@ -95,15 +96,14 @@ RSpec.describe 'Tag description native API', type: :request do
     let(:name_endpoint) { "/tags/name/#{ tag_name.name }/description" }
 
     it 'reads the current resource by Tag ID without a WikiPage' do
-      expect(description.id).not_to eq(tag.id)
-      expect(WikiPage.exists?(id: description.id)).to be(false)
       without_legacy_reads { native_get(endpoint) }
       expect(response).to have_http_status(:ok)
       expect_current(description)
     end
 
     it 'does not interpret a compatibility handle as a Tag ID' do
-      other_tag = create(:tag, id: description.id, primary_name: 'handle_collision')
+      other_tag = create(:tag, primary_name: 'handle_collision')
+      description.update_columns(id: other_tag.id)
       other = TagDescription.create!(
           tag: other_tag, language_code: 'ja', body: 'other current', version_no: 1,
           created_by_user_id: author.id, updated_by_user_id: author.id)
@@ -153,32 +153,6 @@ RSpec.describe 'Tag description native API', type: :request do
       expect_current(description)
     end
 
-    [:id, :name].each do |lookup|
-      it "ignores divergent legacy body and history for #{ lookup } lookup" do
-        page = WikiPage.create!(
-            id: description.id, tag_name:, body: 'old current',
-            created_user: author, updated_user: author)
-        revision = WikiRevision.create!(
-            wiki_page: page, created_user: author, kind: :content,
-            lines_count: 1, tree_sha256: Digest::SHA256.hexdigest('old revision'))
-        line = WikiLine.create!(body: 'old revision', sha256: revision.tree_sha256)
-        WikiRevisionLine.create!(wiki_revision: revision, wiki_line: line, position: 0)
-        WikiVersionRecorder.record!(page:, event_type: :create, created_by_user: author)
-        path = lookup == :id ? endpoint : name_endpoint
-        action = lookup == :id ? 'show' : 'show_by_title'
-
-        without_legacy_reads { native_get(path, action:) }
-        expect(response).to have_http_status(:ok)
-        expect_current(description)
-        original = json
-        page.update_columns(body: 'changed old current')
-        line.update_columns(body: 'changed old revision')
-        revision.update_columns(message: 'changed old history', created_at: 1.day.ago)
-        without_legacy_reads { native_get(path, action:) }
-        expect(response).to have_http_status(:ok)
-        expect(json).to eq(original)
-      end
-    end
   end
 
   describe 'missing native resources' do
@@ -206,44 +180,24 @@ RSpec.describe 'Tag description native API', type: :request do
     context 'without an existing description' do
       before { tag }
 
-      it 'creates a description with synchronised Wiki content and histories' do
-        unrelated = Wiki::Commit.create_legacy_content!(
-            tag_name: create(:tag_name, name: 'Help:unrelated_native_description'),
-            body: 'unrelated body', created_by_user: author)
-        unrelated_state = [unrelated.attributes,
-                           unrelated.wiki_revisions.map(&:attributes),
-                           unrelated.wiki_versions.map(&:attributes)]
+
+      it 'creates native history that is immediately available through the facade' do
         expect { native_write(body: 'created natively') }
             .to change(TagDescription, :count).by(1)
             .and change(TagDescriptionVersion, :count).by(1)
-            .and change(WikiPage, :count).by(1)
-            .and change(WikiRevision, :count).by(1)
-            .and change(WikiVersion, :count).by(1)
         expect(response).to have_http_status(:created)
         description = TagDescription.find_by!(tag_id: tag.id, language_code: 'ja')
-        page = WikiPage.find_by!(tag_name: tag.tag_name('ja'))
-        revision = page.current_revision
-        version = TagDescriptionVersion.find(revision.id)
-        expect(description).to have_attributes(
-            body: 'created natively', version_no: 1,
-            created_by_user_id: editor.id, updated_by_user_id: editor.id)
-        expect(version).to have_attributes(
-            tag_id: tag.id, language_code: 'ja', body: description.body,
-            version_no: 1, event_type: 'create', created_by_user_id: editor.id)
-        expect(page).to have_attributes(tag_name_id: tag_name.id, body: description.body)
-        expect(revision.body).to eq(version.body)
-        expect(page.wiki_versions.last.body).to eq(version.body)
-        unrelated.reload
-        expect([unrelated.attributes, unrelated.wiki_revisions.map(&:attributes),
-                unrelated.wiki_versions.map(&:attributes)]).to eq(unrelated_state)
         expect_current(description)
-
+        version = current_description_version(description)
+        expect(version).to have_attributes(
+            body: 'created natively', version_no: 1, event_type: 'create',
+            created_by_user_id: editor.id)
         get "/wiki/#{ description.id }"
         expect(response).to have_http_status(:ok)
         expect(json).to include('body' => description.body, 'revision_id' => version.id)
       end
 
-      [WikiPage, WikiRevision, WikiVersion, TagDescription, TagDescriptionVersion].each do |model|
+      [TagDescription, TagDescriptionVersion].each do |model|
         it "rolls back native create when #{ model.name } persistence fails" do
           headers
           before_state = stored_state
@@ -258,7 +212,7 @@ RSpec.describe 'Tag description native API', type: :request do
     context 'with an existing description' do
       let!(:page) do
         tag
-        Wiki::Commit.create_content!(tag_name:, body: 'before', created_by_user: author)
+        seed_description(tag_name:, body: 'before', created_by_user: author)
       end
       let!(:description) do
         TagDescription.find_by!(tag_id: tag.id, language_code: 'ja')
@@ -268,22 +222,20 @@ RSpec.describe 'Tag description native API', type: :request do
         expect(page.reload.version_no).to eq(1)
         expect(description.version_no).to eq(1)
         expect { native_write(body: 'after') }
-            .to change(WikiRevision, :count).by(1)
-            .and change(WikiVersion, :count).by(1)
-            .and change(TagDescriptionVersion, :count).by(1)
+            .to change(TagDescriptionVersion, :count).by(1)
         expect(response).to have_http_status(:ok)
         expect(description.reload).to have_attributes(
             body: 'after', version_no: 2,
             created_by_user_id: author.id, updated_by_user_id: editor.id)
         expect(page.reload).to have_attributes(body: 'after', version_no: 2)
 
-        revision = page.current_revision
+        revision = current_description_version(page)
         version = TagDescriptionVersion.find(revision.id)
         expect(version).to have_attributes(
             tag_id: tag.id, language_code: 'ja', version_no: 2, event_type: 'update',
             body: 'after', created_by_user_id: editor.id)
         expect(revision.body).to eq(version.body)
-        expect(page.wiki_versions.order(:version_no).last.body).to eq(version.body)
+        expect(description_versions(page).order(:version_no).last.body).to eq(version.body)
         get "/wiki/#{ description.id }"
         expect(response).to have_http_status(:ok)
         expect(json).to include('body' => 'after', 'revision_id' => version.id)
@@ -294,7 +246,7 @@ RSpec.describe 'Tag description native API', type: :request do
           before_state = stored_state
           page_state = page.reload.attributes
           description_state = description.reload.attributes
-          current_revision_id = page.current_revision.id
+          current_revision_id = current_description_version(page).id
 
           native_write(body:)
 
@@ -302,11 +254,11 @@ RSpec.describe 'Tag description native API', type: :request do
           expect(stored_state).to eq(before_state)
           expect(page.reload.attributes).to eq(page_state)
           expect(description.reload.attributes).to eq(description_state)
-          expect(page.current_revision.id).to eq(current_revision_id)
+          expect(current_description_version(page).id).to eq(current_revision_id)
         end
       end
 
-      [WikiPage, WikiRevision, WikiVersion, TagDescription, TagDescriptionVersion].each do |model|
+      [TagDescription, TagDescriptionVersion].each do |model|
         it "rolls back native update when #{ model.name } persistence fails" do
           headers
           before_state = stored_state
diff --git a/backend/spec/requests/tag_group_wiki_spec.rb b/backend/spec/requests/tag_group_wiki_spec.rb
index b42805c..d24add8 100644
--- a/backend/spec/requests/tag_group_wiki_spec.rb
+++ b/backend/spec/requests/tag_group_wiki_spec.rb
@@ -7,21 +7,17 @@ RSpec.describe 'Tag group Wiki facade reads', type: :request do
   let!(:user) { create_member_user! }
   let!(:old_tag) { group_tag('旧タグ') }
   let!(:new_tag) { group_tag('新タグ') }
-  let!(:page) { legacy_group('読取り契約', '- 旧タグ') }
-  let!(:first_revision) { page.current_revision }
+  let!(:page) { create_markdown_group('読取り契約', '- 旧タグ') }
+  let!(:first_revision) { page.versions.sole }
   let!(:last_revision) do
-    Wiki::Commit.legacy_content!(page:, body: '- 新タグ', created_user: user)
+    parsed = TagGroupMarkdownParser.parse(body: '- 新タグ')
+    TagGroupOperation.update!(
+        group: page, name: page.name, actor: user,
+        **parsed.slice(:description, :members, :placements))
+    page.versions.order(:version_no).last
   end
 
-  before do
-    I18n.locale = :ja
-    migrate_groups
-    page.update_columns(body: 'legacy stale current')
-    page.wiki_revisions.each do |revision|
-      revision.wiki_lines.update_all(body: 'legacy stale revision')
-    end
-    page.wiki_versions.update_all(body: 'legacy stale version')
-  end
+  before { I18n.locale = :ja }
 
   [:id, :title].each do |lookup|
     context "with #{ lookup } lookup" do
@@ -71,36 +67,13 @@ 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
-    help = seed_wiki_page(
-        tag_name: create(:tag_name, name: 'Help:混在'), body: 'help', created_by_user: user)
     TagDescriptionOperation.create!(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(
         'タググループ:読取り契約', '新タグ')
-    expect(json.map { _1.fetch('title') }).not_to include(help.title)
   end
 
-  it 'excludes Help when its ID collides with a new group' do
-    help = seed_wiki_page(
-        tag_name: create(:tag_name, name: 'Help:ID重複'), body: 'help body',
-        created_by_user: user)
-    seed_group(name: '別 ID重複', id: help.id, description: 'group body')
-
-    get '/wiki'
-    expect(response).to have_http_status(:ok)
-    expect(json.map { _1.fetch('title') }).to include('タググループ:別 ID重複')
-    expect(json.map { _1.fetch('title') }).not_to include(help.title)
-
-    get "/wiki/title/#{ CGI.escapeURIComponent(help.title) }"
-    expect(response).to have_http_status(:not_found)
-
-    get '/wiki/changes'
-    expect(response).to have_http_status(:ok)
-    expect(json.map { _1.dig('wiki_page', 'title') }).to include(
-        'タググループ:別 ID重複')
-    expect(json.map { _1.dig('wiki_page', 'title') }).not_to include(help.title)
-  end
 
   it 'finds groups by a partial prefix of their displayed title' do
     get '/wiki', params: { title: 'タググル' }
@@ -112,8 +85,9 @@ RSpec.describe 'Tag group Wiki facade reads', type: :request do
   end
 
   it 'does not restore a stale namespaced Wiki page after a group rename' do
-    old_page = legacy_group('旧名称', '- 旧本文')
-    seed_group(name: '新名称', id: old_page.id, description: '正本')
+    group = create_markdown_group('旧名称', '正本')
+    TagGroupOperation.update!(
+        group:, name: '新名称', description: '正本', members: [], placements: [], actor: user)
 
     get group_title_path('旧名称')
     expect(response).to have_http_status(:not_found)
@@ -125,12 +99,8 @@ RSpec.describe 'Tag group Wiki facade reads', type: :request do
   end
 
   it 'orders mixed resource history by timestamp rather than independent IDs' do
-    help = seed_wiki_page(
-        tag_name: create(:tag_name, name: 'Help:時系列'), body: 'help',
-        created_by_user: user)
     TagDescriptionOperation.create!(tag: new_tag, body: 'description', created_by_user: user)
     TagGroupVersion.update_all(created_at: 3.days.ago)
-    WikiRevision.where(wiki_page_id: help.id).update_all(created_at: 2.days.ago)
     TagDescriptionVersion.update_all(created_at: 1.day.ago)
 
     get '/wiki/changes'
@@ -139,7 +109,6 @@ RSpec.describe 'Tag group Wiki facade reads', type: :request do
     timestamps = json.map { Time.iso8601(_1.fetch('timestamp')) }
     expect(timestamps).to eq(timestamps.sort.reverse)
     titles = json.map { _1.dig('wiki_page', 'title') }
-    expect(titles).not_to include(help.title)
     expect(titles.index('新タグ')).to be < titles.index('タググループ:読取り契約')
   end
 
@@ -169,19 +138,6 @@ RSpec.describe 'Tag group Wiki facade reads', type: :request do
         'wiki_page' => include('id' => page.id, 'title' => 'タググループ:読取り契約'))
   end
 
-  it 'includes group history but excludes all legacy-only revisions' do
-    extra = Wiki::Commit.legacy_content!(page:, body: 'legacy only', created_user: user)
-    help = seed_wiki_page(
-        tag_name: create(:tag_name, name: 'Help:変更一覧'), body: 'help', created_by_user: user)
-    get '/wiki/changes'
-    expect(response).to have_http_status(:ok)
-    rows = json.select { _1.fetch('wiki_page').fetch('title') == 'タググループ:読取り契約' }
-    expect(rows.map { _1.fetch('revision_id') }).to eq([last_revision.id, first_revision.id])
-    expect(rows.map { _1.fetch('revision_id') }).not_to include(extra.id)
-    expect(json).not_to include(include(
-        'revision_id' => help.current_revision.id,
-        'wiki_page' => include('title' => help.title)))
-  end
 
   [false, true].each do |explicit|
     it "diffs structured snapshots with #{ explicit ? 'explicit' : 'current' } target" do
@@ -215,95 +171,5 @@ RSpec.describe 'Tag group Wiki facade reads', type: :request do
     expect(json.fetch('body').strip).to eq('独立した説明')
   end
 
-  context 'when Help, description and group share the same numeric ID' do
-    let(:colliding_help) do
-      seed_wiki_page(
-          tag_name: create(:tag_name, name: 'Help:三者ID衝突'),
-          body: 'help', created_by_user: user)
-    end
-    let(:colliding_group_id) do
-      seed_group(name: '三者ID衝突', id: colliding_help.id, description: 'group')
-    end
-    let(:colliding_description) do
-      TagDescription.create!(
-          id: colliding_help.id, tag: new_tag, language_code: 'ja',
-          body: 'description', version_no: 1)
-    end
-    let(:colliding_description_version) do
-      TagDescriptionVersion.create!(
-          tag_id: new_tag.id, language_code: 'ja', version_no: 1,
-          event_type: 'create', body: 'description', created_by_user_id: user.id,
-          created_at: Time.current)
-    end
 
-    before do
-      colliding_group_id
-      colliding_description
-      colliding_description_version
-    end
-
-    it 'lists both new resources sharing a numeric ID without legacy Help' do
-      get '/wiki'
-
-      expect(response).to have_http_status(:ok)
-      rows = json.select { _1.fetch('id') == colliding_help.id }
-      expect(rows.map { [_1.fetch('id'), _1.fetch('title')] }).to contain_exactly(
-          [colliding_description.id, '新タグ'],
-          [colliding_group_id, 'タググループ:三者ID衝突'])
-    end
-
-    it 'lists each resource history without deduplicating the shared resource ID' do
-      get '/wiki/changes'
-
-      expect(response).to have_http_status(:ok)
-      rows = json.select { _1.fetch('wiki_page').fetch('id') == colliding_help.id }
-      histories = rows.map do |row|
-        [row.fetch('revision_id'), row.fetch('wiki_page').fetch('title')]
-      end
-      expect(histories).to contain_exactly(
-          [colliding_description_version.id, '新タグ'],
-          [group_version(colliding_group_id, 1).fetch('id'), 'タググループ:三者ID衝突'])
-    end
-
-    it 'still excludes legacy copies of an actually migrated group and its history' do
-      extra = Wiki::Commit.legacy_content!(page:, body: 'legacy only', created_user: user)
-
-      get '/wiki'
-
-      expect(response).to have_http_status(:ok)
-      rows = json.select { _1.fetch('id') == page.id }
-      expect(rows.map { _1.fetch('title') }).to eq(['タググループ:読取り契約'])
-
-      get '/wiki/changes'
-
-      expect(response).to have_http_status(:ok)
-      rows = json.select { _1.fetch('wiki_page').fetch('id') == page.id }
-      expect(rows.map { _1.fetch('revision_id') })
-          .to contain_exactly(first_revision.id, last_revision.id)
-      expect(rows.map { _1.fetch('revision_id') }).not_to include(extra.id)
-      expect(rows.map { _1.fetch('wiki_page').fetch('title') })
-          .to all(eq('タググループ:読取り契約'))
-    end
-  end
-
-  it 'resolves new resources by title while excluding colliding legacy Help' do
-    help = seed_wiki_page(
-        tag_name: create(:tag_name, name: 'Help:ID衝突'), body: 'help', created_by_user: user)
-    seed_group(name: 'ID衝突', id: help.id, description: 'group')
-    TagDescription.create!(
-        id: help.id, tag: new_tag, language_code: 'ja', body: 'description', version_no: 1)
-    TagDescriptionVersion.create!(
-        tag_id: new_tag.id, language_code: 'ja', version_no: 1,
-        event_type: 'create', body: 'description', created_at: Time.current)
-    { 'タググループ:ID衝突' => 'group', '新タグ' => 'description' }
-        .each do |title, body|
-      get "/wiki/title/#{ CGI.escapeURIComponent(title) }"
-      expect(response).to have_http_status(:ok)
-      expect(json.fetch('body').strip).to eq(body)
-    end
-    without_group_legacy_reads do
-      get "/wiki/title/#{ CGI.escapeURIComponent(help.title) }"
-    end
-    expect(response).to have_http_status(:not_found)
-  end
 end
diff --git a/backend/spec/requests/tag_group_wiki_write_spec.rb b/backend/spec/requests/tag_group_wiki_write_spec.rb
index 7498e9f..846537f 100644
--- a/backend/spec/requests/tag_group_wiki_write_spec.rb
+++ b/backend/spec/requests/tag_group_wiki_write_spec.rb
@@ -33,11 +33,10 @@ RSpec.describe 'Tag group Wiki facade writes', type: :request do
     end
   end
 
-  it 'creates the group, snapshot and matching compatibility histories' do
+  it 'creates the group, snapshot and native version history' do
     expect { create_group }
-        .to change(WikiPage, :count).by(1)
-        .and change(WikiRevision, :count).by(1)
-        .and change(WikiVersion, :count).by(1)
+        .to change(TagGroup, :count).by(1)
+        .and change(TagGroupVersion, :count).by(1)
     expect(response).to have_http_status(:created)
     group = group_rows('tag_groups', name: '新規').sole
     expect(json).to include('id' => group.fetch('id'), 'title' => 'タググループ:新規')
@@ -45,10 +44,9 @@ RSpec.describe 'Tag group Wiki facade writes', type: :request do
     version = group_version(group.fetch('id'), 1)
     expect(version).to include('event_type' => 'create', 'created_by_user_id' => user.id)
     expect(group).to include('created_by_user_id' => user.id, 'updated_by_user_id' => user.id)
-    page = WikiPage.joins(:tag_name).find_by!(tag_names: { name: 'タググループ:新規' })
-    expect(page.body).to eq('- 洗澡鹿')
-    expect(page.current_revision.body).to eq(page.body)
-    expect(page.wiki_versions.sole.body).to eq(page.body)
+    get group_title_path('新規')
+    expect(response).to have_http_status(:ok)
+    expect(json.fetch('body')).to eq('- 洗澡鹿')
   end
 
   it 'keeps repeated placements but only one membership and one snapshot member' do
@@ -108,10 +106,9 @@ RSpec.describe 'Tag group Wiki facade writes', type: :request do
   end
 
   context 'updating a migrated group' do
-    let!(:page) { legacy_group('更新', '- 洗澡鹿') }
-    let!(:old_revision) { page.current_revision }
+    let!(:page) { create_markdown_group('更新', '- 洗澡鹿') }
+    let!(:old_revision) { page.versions.order(:version_no).last }
 
-    before { migrate_groups }
 
     def update_group body: '- 伊地知ニジカ', title: 'タググループ:更新', request_headers: headers
       put "/wiki/#{ page.id }", params: { title:, body: }, headers: request_headers
@@ -119,9 +116,9 @@ RSpec.describe 'Tag group Wiki facade writes', type: :request do
 
     [1, 3].each do |repetitions|
       it "keeps identical Markdown unchanged after #{ repetitions } Wiki PUTs" do
-        body = page.body
+        body = group_markdown(page)
         travel_to(1.hour.from_now) do
-          expect_noop_group_update(group_id: page.id, page:) do
+          expect_noop_group_update(group_id: page.id) do
             repetitions.times do
               update_group(body:)
               expect(response).to have_http_status(:ok)
@@ -134,13 +131,13 @@ RSpec.describe 'Tag group Wiki facade writes', type: :request do
     it 'keeps identical Markdown unchanged with a stale base_revision_id' do
       update_group
       expect(response).to have_http_status(:ok)
-      body = page.reload.body
-      expect(page.current_revision.id).not_to eq(old_revision.id)
+      body = group_markdown(page)
+      expect(page.versions.order(:version_no).last.id).not_to eq(old_revision.id)
 
       travel_to(1.hour.from_now) do
-        expect_noop_group_update(group_id: page.id, page:) do
+        expect_noop_group_update(group_id: page.id) do
           put "/wiki/#{ page.id }",
-              params: { title: page.title, body:, base_revision_id: old_revision.id },
+              params: { title: "タググループ:#{ page.name }", body:, base_revision_id: old_revision.id },
               headers: headers
         end
       end
@@ -148,9 +145,9 @@ RSpec.describe 'Tag group Wiki facade writes', type: :request do
 
     it 'keeps the original editor on identical Markdown from another member' do
       editor = create(:user, :member)
-      body = page.body
+      body = group_markdown(page)
       travel_to(1.hour.from_now) do
-        expect_noop_group_update(group_id: page.id, page:) do
+        expect_noop_group_update(group_id: page.id) do
           update_group(body:, request_headers: { 'X-Transfer-Code' => editor.inheritance_code })
         end
       end
@@ -168,11 +165,11 @@ RSpec.describe 'Tag group Wiki facade writes', type: :request do
           page.id, number: 2,
           members: [{ 'tag_id' => other_tag.id, 'version_no' => other_tag.version_no }],
           placements: changed_placements)
-      body = page.reload.body
+      body = group_markdown(page)
       expect(body).to eq('- 伊地知ニジカ')
 
       travel_to(1.hour.from_now) do
-        expect_noop_group_update(group_id: page.id, page:) { update_group(body:) }
+        expect_noop_group_update(group_id: page.id) { update_group(body:) }
       end
     end
 
@@ -187,16 +184,13 @@ RSpec.describe 'Tag group Wiki facade writes', type: :request do
       expect(group_version(page.id, 1)).to eq(old)
       expect(group_version(page.id, 2)).to include(
           'event_type' => 'update', 'created_by_user_id' => user.id)
-      expect(page.reload.body.strip).to eq('- 伊地知ニジカ')
-      expect(page.wiki_revisions.count).to eq(2)
-      expect(page.wiki_versions.count).to eq(2)
-      expect(page.current_revision.body).to eq(page.body)
-      expect(page.wiki_versions.order(:version_no).last.body).to eq(page.body)
+      expect(group_markdown(page).strip).to eq('- 伊地知ニジカ')
+      expect(page.versions.count).to eq(2)
     end
 
     it 'accepts the current base_revision_id used by the existing frontend' do
       put "/wiki/#{ page.id }",
-          params: { title: page.title, body: '- 伊地知ニジカ',
+          params: { title: "タググループ:#{ page.name }", body: '- 伊地知ニジカ',
                     base_revision_id: old_revision.id }, headers: headers
       expect(response).to have_http_status(:ok)
       expect(group_rows('tag_groups', id: page.id).sole.fetch('version_no')).to eq(2)
@@ -207,12 +201,12 @@ RSpec.describe 'Tag group Wiki facade writes', type: :request do
       expect(response).to have_http_status(:ok)
 
       put "/wiki/#{ page.id }",
-          params: { title: page.title, body: '- 洗澡鹿',
+          params: { title: "タググループ:#{ page.name }", body: '- 洗澡鹿',
                     base_revision_id: old_revision.id }, headers: headers
 
       expect(response).to have_http_status(:ok)
       expect(group_rows('tag_groups', id: page.id).sole.fetch('version_no')).to eq(3)
-      expect(page.reload.body.strip).to eq('- 洗澡鹿')
+      expect(group_markdown(page).strip).to eq('- 洗澡鹿')
     end
 
     it 'records the editor and update time' do
@@ -257,9 +251,7 @@ RSpec.describe 'Tag group Wiki facade writes', type: :request do
       let!(:page) do
         next unless operation == :update
 
-        legacy = legacy_group('更新', '- 洗澡鹿')
-        seed_group(name: '更新', id: legacy.id, members:, placements:)
-        legacy
+        create_markdown_group('更新', '- 洗澡鹿')
       end
       let!(:child_id) { seed_group(name: '子グループ', description: '子') }
 
@@ -296,7 +288,6 @@ RSpec.describe 'Tag group Wiki facade writes', type: :request do
       end
 
       tables = TagGroupRecords::GROUP_TABLES
-      tables += ['wiki_pages', 'wiki_revisions', 'wiki_versions']
       tables.each do |table|
         it "rolls back all writes after a real #{ table } write fails" do
           expect_atomic_group_write(table) { write_group(operation, headers) }
diff --git a/backend/spec/requests/tag_group_write_integrity_spec.rb b/backend/spec/requests/tag_group_write_integrity_spec.rb
index 98c2e5d..24e5d99 100644
--- a/backend/spec/requests/tag_group_write_integrity_spec.rb
+++ b/backend/spec/requests/tag_group_write_integrity_spec.rb
@@ -24,11 +24,6 @@ RSpec.describe 'Tag group write integrity', type: :request do
     put "/wiki/#{ id }", params: { title:, body:, base_revision_id: base }, headers: headers
   end
 
-  def create_help body
-    seed_wiki_page(
-        tag_name: create(:tag_name, name: 'Help:既存'), body:, created_by_user: user)
-  end
-
   def expect_no_writes
     before_state = group_state
     yield
@@ -37,66 +32,28 @@ RSpec.describe 'Tag group write integrity', type: :request do
   end
 
   context 'resource identity' do
-    it 'rejects removing the prefix from a migrated group atomically' do
-      page = legacy_group('更新', '- 洗澡鹿')
-      seed_group(name: '更新', id: page.id, members:, placements:)
-
-      expect_no_writes do
-        put_wiki(page.id, title: '更新', base: page.current_revision.id)
-      end
-    end
 
     it 'rejects an unprefixed update to an independent group' do
       id = seed_group(name: '独立', members:, placements:)
       expect_no_writes { put_wiki(id, title: '独立') }
     end
 
-    it 'does not revive legacy writes when the compatibility title is stale' do
-      page = legacy_group('更新', '- 洗澡鹿')
-      seed_group(name: '更新', id: page.id, members:, placements:)
-      page.tag_name.update!(name: '古い別名')
 
-      expect_no_writes { put_wiki(page.id, title: '古い別名') }
-    end
-
-    it 'renames the group and its compatibility page through the operation' do
-      page = legacy_group('更新', '- 洗澡鹿')
-      seed_group(name: '更新', id: page.id, members:, placements:)
+    it 'renames the group and its facade title through the operation' do
+      page = create_markdown_group('更新', '- 洗澡鹿')
 
       put_wiki(page.id, title: 'タググループ:改名')
 
       expect(response).to have_http_status(:ok)
       expect(TagGroup.find(page.id)).to have_attributes(name: '改名', version_no: 2)
-      expect(page.reload.title).to eq('タググループ:改名')
-      expect(page.body).to eq('- 伊地知ニジカ')
+      expect("タググループ:#{ page.reload.name }").to eq('タググループ:改名')
+      expect(group_markdown(page)).to eq('- 伊地知ニジカ')
     end
 
-    it 'rejects a standalone Help update despite a colliding group ID' do
-      page = create_help('Help body')
-      id = seed_group(name: '別グループ', id: page.id, members:, placements:)
-      group_before = TagGroup.find(id).attributes
-      version_before = group_version(id, 1)
 
-      expect_no_writes { put_wiki(id, title: 'Help:改名', body: 'Help after') }
-
-      expect(page.reload.body).to eq('Help body')
-      expect(page.title).to eq('Help:既存')
-      expect(TagGroup.find(id).attributes).to eq(group_before)
-      expect(group_version(id, 1)).to eq(version_before)
-    end
-
-    it 'rejects an ambiguous unprefixed rename when Help and group IDs collide' do
-      page = create_help('Help body')
-      seed_group(name: '更新', id: page.id, members:, placements:)
-
-      expect_no_writes { put_wiki(page.id, title: '更新') }
-      expect_no_writes do
-        put_wiki(page.id, title: '更新', base: page.current_revision.id)
-      end
-    end
 
     it 'keeps a description update separate from a colliding group' do
-      page = Wiki::Commit.create_content!(
+      page = seed_description(
           tag_name: tag.tag_name('ja'), body: 'description before', created_by_user: user)
       description = TagDescription.find_by!(tag_id: tag.id)
       id = seed_group(name: '更新', id: description.id, members:, placements:)
@@ -110,106 +67,22 @@ RSpec.describe 'Tag group write integrity', type: :request do
       expect(TagGroup.find(id).attributes).to eq(group_before)
     end
 
-    it 'does not route a colliding Help write into an unrelated description' do
-      page = create_help('Help before')
-      id = seed_group(name: '更新', id: page.id, members:, placements:)
-      description = TagDescription.create!(
-          id:, tag:, language_code: 'ja', version_no: 1, body: 'description')
+  end
 
-      expect_no_writes { put_wiki(id, title: 'Help:既存', body: 'Help after') }
 
-      expect(page.reload.body).to eq('Help before')
-      expect(description.reload.body).to eq('description')
-      expect(TagGroup.find(id).version_no).to eq(1)
-      put_wiki(id, title: '洗澡鹿', body: 'description after')
-      expect(response).to have_http_status(:ok)
-      expect(description.reload.body).to eq('description after')
-      put_wiki(id, title: 'タググループ:更新')
-      expect(response).to have_http_status(:ok)
-      expect(TagGroup.find(id).version_no).to eq(2)
-      expect(page.reload.body).to eq('Help before')
-      expect(description.reload.body).to eq('description after')
+  it 'rolls back a facade create when its saved structure cannot be rendered' do
+    allow(TagGroupMarkdownRenderer).to receive(:render)
+        .and_raise(TagGroupMarkdownRenderer::UnsupportedStructure, 'unsupported')
+    expect_no_writes do
+      post '/wiki', params: { title: 'タググループ:新規', body: '- 洗澡鹿' }, headers: headers
     end
   end
 
-  context 'compatibility synchronisation' do
-    it 'synchronises a native rename without modifying an ID-colliding Help page' do
-      help = create_help('Help before')
-      id = seed_group(name: '更新', id: help.id, members:, placements:)
-      help_before = help.attributes
-
-      expect do
-        put "/tag_groups/#{ id }", params: native_payload(name: '改名'), headers:, as: :json
-      end.to change(WikiPage, :count).by(1)
-          .and change(WikiRevision, :count).by(1)
-          .and change(WikiVersion, :count).by(1)
-
-      expect(response).to have_http_status(:ok)
-      expect(TagGroup.find(id).name).to eq('改名')
-      expect(help.reload.attributes).to eq(help_before)
-    end
-
-    ['wiki_lines', 'wiki_revision_lines'].each do |table|
-      it "rolls back native and compatibility state on #{ table } failure" do
-        expect_atomic_group_write(table) do
-          post '/tag_groups', params: native_payload, headers:, as: :json
-        end
-      end
-    end
-
-    it 'rolls back a renderer failure instead of treating it as unsupported structure' do
-      allow(TagGroupMarkdownRenderer).to receive(:render).and_raise('renderer failure')
-      before_state = group_state
-
-      expect do
-        post '/tag_groups', params: native_payload, headers:, as: :json
-      end.to raise_error(RuntimeError, 'renderer failure')
-
-      expect(group_state).to eq(before_state)
-    end
-
-    it 'preserves unplaced membership and reports the skipped sync with its version' do
-      page = legacy_group('更新', '- 洗澡鹿')
-      id = seed_group(name: '更新', id: page.id, members:, placements:)
-      wiki_before = group_state.slice(*TagGroupRecords::WRITE_TABLES.drop(5))
-      warnings = []
-      allow(Rails.logger).to receive(:warn) { warnings << _1 }
-
-      put "/tag_groups/#{ id }",
-          params: native_payload(member_rows: members + [{ 'tag_id' => other_tag.id }]),
-          headers:, as: :json
-
-      expect(response).to have_http_status(:ok)
-      expect(json.fetch('members').map { _1.fetch('tag').fetch('id') })
-          .to contain_exactly(tag.id, other_tag.id)
-      expect(group_version(id, 2).fetch('members')).to include(
-          { 'tag_id' => other_tag.id, 'version_no' => other_tag.version_no })
-      expect(group_state.slice(*TagGroupRecords::WRITE_TABLES.drop(5))).to eq(wiki_before)
-      payload = JSON.parse(warnings.grep(/tag_group_wiki_sync_skipped/).sole.split(' ', 2).last)
-      expect(payload).to include(
-          'status' => 'unsupported_structure', 'tag_group_id' => id,
-          'version_no' => 2, 'user_id' => user.id,
-          'reason' => '掲載位置のない membership は Markdown にできません．')
-    end
-
-    it 'preserves a list Section description and records why no Wiki was created' do
-      nodes = [{ 'tag_id' => tag.id, 'children' => [
-          { 'section_name' => '区分', 'description' => '構造化の説明', 'children' => [] }] }]
-      warnings = []
-      allow(Rails.logger).to receive(:warn) { warnings << _1 }
-      before_count = WikiPage.count
-
-      post '/tag_groups', params: native_payload(nodes:), headers:, as: :json
-
-      expect(response).to have_http_status(:created)
-      id = json.fetch('id')
-      expect(group_version(id, 1).fetch('placements')).to eq(nodes)
-      expect(json.fetch('placements').sole.fetch('children').sole)
-          .to include('description' => '構造化の説明')
-      expect(WikiPage.count).to eq(before_count)
-      expect(warnings.grep(/tag_group_wiki_sync_skipped/).sole)
-          .to include('リスト内 Section の説明文は Markdown にできません．')
-    end
+  it 'rolls back a facade update when its saved structure cannot be rendered' do
+    id = seed_group(name: '更新', members:, placements:)
+    allow(TagGroupMarkdownRenderer).to receive(:render)
+        .and_raise(TagGroupMarkdownRenderer::UnsupportedStructure, 'unsupported')
+    expect_no_writes { put_wiki(id, title: 'タググループ:改名') }
   end
 
   context 'identifier Markdown' do
@@ -293,10 +166,10 @@ RSpec.describe 'Tag group write integrity', type: :request do
       expect(group_version(id, 2)).to include('description' => '説明を追加', 'members' => members)
     end
 
-    it 'rolls back membership removal and placement edits on a late sync failure' do
+    it 'rolls back membership removal and placement edits on a version persistence failure' do
       new_members = [{ 'tag_id' => tag.id }]
       new_nodes = [{ 'tag_id' => tag.id, 'children' => [] }]
-      expect_atomic_group_write('wiki_versions') do
+      expect_atomic_group_write('tag_group_versions') do
         put "/tag_groups/#{ id }",
             params: native_payload(nodes: new_nodes, member_rows: new_members), headers:, as: :json
       end
diff --git a/backend/spec/requests/tag_groups_spec.rb b/backend/spec/requests/tag_groups_spec.rb
index d910dfb..ebca4c7 100644
--- a/backend/spec/requests/tag_groups_spec.rb
+++ b/backend/spec/requests/tag_groups_spec.rb
@@ -234,8 +234,7 @@ RSpec.describe 'Tag group native API', type: :request do
 
     context 'compatibility writes for representable structures' do
       let(:group_id) do
-        page = legacy_group('専用API', '説明')
-        seed_group(name: '専用API', id: page.id, description: '説明')
+        seed_group(name: '専用API', description: '説明')
       end
       let(:members) { [{ 'tag_id' => tag.id }, { 'tag_group_id' => child_id }] }
       let(:snapshot_members) do
@@ -252,10 +251,9 @@ RSpec.describe 'Tag group native API', type: :request do
             group_id, number: 2, description: '全体の説明', placements:,
             members: snapshot_members + [
                 { 'tag_id' => unplaced.id, 'version_no' => unplaced.version_no }])
-        page = WikiPage.joins(:tag_name).find_by!(tag_names: { name: 'タググループ:専用API' })
 
         travel_to(1.hour.from_now) do
-          expect_noop_group_update(group_id:, page:) do
+          expect_noop_group_update(group_id:) do
             native_write(:update, unplaced_payload)
           end
         end
@@ -267,20 +265,18 @@ RSpec.describe 'Tag group native API', type: :request do
             members: [{ 'tag_id' => tag.id }, { 'tag_group_id' => child_id }], placements: }
         end
         let(:additional_tag) { group_tag('追加対象タグ') }
-        let(:compatibility_page) do
-          WikiPage.joins(:tag_name).find_by!(tag_names: { name: 'タググループ:構造化' })
-        end
 
         before do
           native_write(:update, synchronised_payload)
           expect(response).to have_http_status(:ok)
-          expect(compatibility_page.body).to include('- 掲載タグ', '- タググループ:子')
+          expect(group_markdown(TagGroup.find(group_id)))
+              .to include('- 掲載タグ', '- タググループ:子')
         end
 
         [1, 3].each do |repetitions|
           it "keeps identical native content unchanged after #{ repetitions } PUTs" do
             travel_to(1.hour.from_now) do
-              expect_noop_group_update(group_id:, page: compatibility_page) do
+              expect_noop_group_update(group_id:) do
                 repetitions.times do
                   native_write(:update, synchronised_payload)
                   expect(response).to have_http_status(:ok)
@@ -292,7 +288,7 @@ RSpec.describe 'Tag group native API', type: :request do
 
         it 'treats membership order alone as a no-op' do
           travel_to(1.hour.from_now) do
-            expect_noop_group_update(group_id:, page: compatibility_page) do
+            expect_noop_group_update(group_id:) do
               native_write(:update, synchronised_payload.merge(
                   members: synchronised_payload.fetch(:members).reverse))
             end
@@ -302,7 +298,7 @@ RSpec.describe 'Tag group native API', type: :request do
         it 'keeps the original editor when another member submits identical content' do
           editor = create(:user, :member)
           travel_to(1.hour.from_now) do
-            expect_noop_group_update(group_id:, page: compatibility_page) do
+            expect_noop_group_update(group_id:) do
               put "/tag_groups/#{ group_id }", params: synchronised_payload,
                   headers: { 'X-Transfer-Code' => editor.inheritance_code }, as: :json
             end
@@ -313,7 +309,7 @@ RSpec.describe 'Tag group native API', type: :request do
           put "/wiki/#{ group_id }",
               params: { title: 'タググループ:構造化', body: '- 未掲載タグ' }, headers: headers
           expect(response).to have_http_status(:ok)
-          expect(compatibility_page.reload.body).to eq('- 未掲載タグ')
+          expect(group_markdown(TagGroup.find(group_id))).to eq('- 未掲載タグ')
           same_content = {
               name: '構造化', description: nil, members: [{ 'tag_id' => unplaced.id }],
               placements: [{ 'tag_id' => unplaced.id, 'children' => [] }] }
@@ -323,7 +319,7 @@ RSpec.describe 'Tag group native API', type: :request do
               placements: same_content.fetch(:placements))
 
           travel_to(1.hour.from_now) do
-            expect_noop_group_update(group_id:, page: compatibility_page) do
+            expect_noop_group_update(group_id:) do
               native_write(:update, same_content)
             end
           end
@@ -332,7 +328,7 @@ RSpec.describe 'Tag group native API', type: :request do
         ['name', 'description', 'membership addition', 'membership removal',
          'Section name', 'Section description', 'placement order', 'placement hierarchy']
             .each do |change|
-          it "records a real #{ change } change in both histories" do
+          it "records a real #{ change } change in native history" do
             changed = synchronised_payload.deep_dup
             section = changed.fetch(:placements).first
             children = section.fetch('children')
@@ -356,11 +352,6 @@ RSpec.describe 'Tag group native API', type: :request do
             old_versions = group_rows('tag_group_versions', tag_group_id: group_id)
             group = TagGroup.find(group_id)
             number = group.version_no
-            page = compatibility_page
-            old_revision_id = page.current_revision.id
-            old_wiki_version_id = page.wiki_versions.order(version_no: :desc).first.id
-            revision_count = page.wiki_revisions.count
-            version_count = page.wiki_versions.count
             travel_to(1.hour.from_now) { native_write(:update, changed) }
 
             expect(response).to have_http_status(:ok)
@@ -379,23 +370,17 @@ RSpec.describe 'Tag group native API', type: :request do
             versions = group_rows('tag_group_versions', tag_group_id: group_id)
             expect(versions.size).to eq(old_versions.size + 1)
             expect(versions.select { _1.fetch('version_no') <= number }).to eq(old_versions)
-            expect(page.wiki_revisions.count).to eq(revision_count + 1)
-            expect(page.wiki_versions.count).to eq(version_count + 1)
-            expect(page.reload.current_revision.id).not_to eq(old_revision_id)
-            expect(page.wiki_versions.order(version_no: :desc).first.id)
-                .not_to eq(old_wiki_version_id)
             get group_title_path(changed.fetch(:name))
             expect(response).to have_http_status(:ok)
-            expect(json.fetch('body')).to eq(page.body)
+            expect(json.fetch('body')).to eq(group_markdown(group))
           end
         end
       end
 
-      it 'creates native state and its compatibility histories' do
+      it 'creates native state and its native history' do
         expect { native_write(:create) }
-            .to change(WikiPage, :count).by(1)
-            .and change(WikiRevision, :count).by(1)
-            .and change(WikiVersion, :count).by(1)
+            .to change(TagGroup, :count).by(1)
+            .and change(TagGroupVersion, :count).by(1)
         expect(response).to have_http_status(:created)
         expect_group_snapshot(
             json.fetch('id'), number: 1, members: snapshot_members,
@@ -410,18 +395,13 @@ RSpec.describe 'Tag group native API', type: :request do
           number = operation == :create ? 1 : 2
           expect_group_snapshot(
               id, number:, members: snapshot_members, placements:, description: '全体の説明')
-          page = WikiPage.joins(:tag_name).find_by!(tag_names: { name: 'タググループ:構造化' })
-          expect(page.body).to include('全体の説明', '# 区分', '- 掲載タグ', '- タググループ:子')
-          expect(page.current_revision.body).to eq(page.body)
-          expect(page.wiki_versions.order(:version_no).last.body).to eq(page.body)
-          expect(page.wiki_revisions.count).to eq(number)
-          expect(page.wiki_versions.count).to eq(number)
+          expect(TagGroup.find(id).versions.count).to eq(number)
           get group_title_path('構造化')
           expect(response).to have_http_status(:ok)
-          expect(json.fetch('body')).to eq(page.body)
+          expect(json.fetch('body')).to include('全体の説明', '# 区分', '- 掲載タグ')
         end
 
-        (TagGroupRecords::GROUP_TABLES + ['wiki_pages', 'wiki_revisions', 'wiki_versions'])
+        TagGroupRecords::GROUP_TABLES
             .each do |table|
           it "rolls back native #{ operation } after #{ table } writes" do
             expect_atomic_group_write(table) { native_write(operation) }
@@ -429,12 +409,12 @@ RSpec.describe 'Tag group native API', type: :request do
         end
       end
 
-      it 'assigns the next group ID from the existing maximum' do
+      it 'assigns the next group ID above the existing maximum' do
         child_id
         expected_id = [TagGroup.maximum(:id).to_i, TagDescription.maximum(:id).to_i].max + 1
         native_write(:create)
         expect(response).to have_http_status(:created)
-        expect(json.fetch('id')).to eq(expected_id)
+        expect(json.fetch('id')).to be >= expected_id
       end
 
       TagGroupRecords::GROUP_TABLES.each do |table|
diff --git a/backend/spec/requests/tag_resource_ids_spec.rb b/backend/spec/requests/tag_resource_ids_spec.rb
index 7c324cc..e06e96b 100644
--- a/backend/spec/requests/tag_resource_ids_spec.rb
+++ b/backend/spec/requests/tag_resource_ids_spec.rb
@@ -1,101 +1,59 @@
 require 'rails_helper'
 
 RSpec.describe 'Tag resource ID allocation', type: :request do
-  include TagGroupRecords
   include WikiRecords
-
   let!(:user) { create_member_user! }
   let(:headers) { { 'X-Transfer-Code' => user.inheritance_code } }
 
-  def seed_description id
-    tag = create(:tag, primary_name: "description_id_#{ id }")
-    TagDescription.create!(id:, tag:, language_code: 'ja', body: 'existing', version_no: 1)
-  end
-
-  def create_resource resource
-    if resource == :description
-      tag = create(:tag, primary_name: 'new_description')
-      post '/wiki', params: { title: tag.name('ja'), body: 'new description' }, headers: headers
-    else
-      post '/tag_groups', params: {
-          name: 'new_group', description: 'new group', members: [], placements: [] },
-          headers:, as: :json
-    end
+  def create_description name
+    tag = create(:tag, primary_name: name)
+    post '/wiki', params: { title: tag.name('ja'), body: 'description' }, headers: headers
     expect(response).to have_http_status(:created)
+    TagDescription.find(json.fetch('id'))
   end
 
-  [:description, :group].each do |resource|
-    it "keeps #{ resource } independent of the Tag and ExternalTag ID space" do
-      create(:tag, id: 100)
-      create(:external_tag, id: 200)
-      seed_description(1)
-      seed_group(name: 'shared_space', id: 2)
+  def create_group name
+    post '/tag_groups', params: { name:, members: [], placements: [] }, headers:, as: :json
+    expect(response).to have_http_status(:created)
+    TagGroup.find(json.fetch('id'))
+  end
 
-      create_resource(resource)
-
-      expect(json.fetch('id')).to eq(3)
-    end
-
-    it "uses the other resource's larger maximum when allocating #{ resource }" do
-      seed_description(resource == :description ? 1 : 20)
-      seed_group(name: 'other_space', id: resource == :group ? 1 : 20)
-      create_resource(resource)
-      expect(json.fetch('id')).to eq(21)
-    end
-
-    it "starts #{ resource } at 1 even after previous allocated rows were removed" do
-      expect(TagDescription.count).to eq(0)
-      expect(TagGroup.count).to eq(0)
-      if resource == :description
-        seed_description(100).destroy!
-      else
-        id = seed_group(name: 'removed', id: 100)
-        TagGroup.find(id).destroy!
-      end
-      create_resource(resource)
-      expect(json.fetch('id')).to eq(1)
-    end
-
-    it "allocates #{ resource } above both maxima, preserving legacy overlaps and gaps" do
-      [1, 2, 5].each { seed_description(_1) }
-      [1, 3, 8].each { seed_group(name: "group_#{ _1 }", id: _1) }
-      descriptions = TagDescription.order(:id).map(&:attributes)
-      groups = TagGroup.order(:id).map(&:attributes)
-
-      create_resource(resource)
-
-      expect(json.fetch('id')).to eq(9)
-      expect(TagDescription.where(id: [1, 2, 5]).order(:id).map(&:attributes)).to eq(descriptions)
-      expect(TagGroup.where(id: [1, 3, 8]).order(:id).map(&:attributes)).to eq(groups)
-      expect(TagDescription.exists?(id: 3)).to be(false)
-      expect(TagGroup.exists?(id: 2)).to be(false)
+  it 'shares resource and revision IDs while keeping independent version numbers' do
+    description = create_description('first')
+    group = create_group('second')
+    other = create_description('third')
+    expect([description.id, group.id, other.id]).to eq(
+        [description.id, group.id, other.id].sort.uniq)
+    versions = [current_description_version(description), group.versions.sole,
+                current_description_version(other)]
+    expect(versions.map(&:id)).to eq(versions.map(&:id).sort.uniq)
+    expect(versions.map(&:version_no)).to eq([1, 1, 1])
+    [description, group, other].zip(versions).each do |resource, version|
+      get "/wiki/#{ resource.id }"
+      expect(response).to have_http_status(:ok)
+      expect(json.fetch('revision_id')).to eq(version.id)
     end
   end
 
-  it 'preserves group ID and unrelated rows on update' do
-    id = seed_group(name: 'existing', id: 5, description: 'before')
-    other_id = seed_group(name: 'other', id: 8, description: 'other')
-    other = TagGroup.find(other_id).attributes
-    put "/tag_groups/#{ id }", params: {
-        name: 'renamed', description: 'after', members: [], placements: [] }, headers:, as: :json
+  it 'does not reuse a deleted description ID for a group or vice versa' do
+    description = create_description('deleted')
+    description.destroy!
+    group = create_group('deleted group')
+    expect(group.id).to be > description.id
+    group.destroy!
+    expect(create_description('replacement').id).to be > group.id
+  end
+
+  it 'preserves resource and old revision identity on an update' do
+    description = create_description('stable')
+    original = current_description_version(description)
+    snapshot = original.attributes
+    put "/wiki/#{ description.id }", params: {
+        title: 'stable', body: 'after', base_revision_id: original.id }, headers: headers
     expect(response).to have_http_status(:ok)
-    expect(json.fetch('id')).to eq(id)
-    expect(TagGroup.find(id).description).to eq('after')
-    expect(TagGroup.find(other_id).attributes).to eq(other)
-    expect(TagGroup.count).to eq(2)
-  end
-
-  it 'preserves description identity on a compatibility update' do
-    tag = create(:tag, primary_name: 'existing_description')
-    page = seed_wiki_page(tag_name: tag.tag_name('ja'), body: 'before', created_by_user: user)
-    description = TagDescription.find_by!(tag_id: tag.id, language_code: 'ja')
-    id = description.id
-    put "/wiki/#{ id }", params: {
-        title: tag.name('ja'), body: 'after', base_revision_id: page.current_revision.id },
-        headers: headers
-    expect(response).to have_http_status(:ok)
-    expect(description.reload.id).to eq(id)
-    expect(description.body).to eq('after')
-    expect(TagDescription.count).to eq(1)
+    expect(json.fetch('id')).to eq(description.id)
+    expect(description.reload).to have_attributes(body: 'after', version_no: 2)
+    expect(original.reload.attributes).to eq(snapshot)
+    expect(current_description_version(description).id).to be > original.id
   end
 end
diff --git a/backend/spec/requests/tag_versions_spec.rb b/backend/spec/requests/tag_versions_spec.rb
index f105773..7165a0f 100644
--- a/backend/spec/requests/tag_versions_spec.rb
+++ b/backend/spec/requests/tag_versions_spec.rb
@@ -1,6 +1,7 @@
 require 'rails_helper'
 
 RSpec.describe 'TagVersions API', type: :request do
+  include WikiRecords
   let(:member) { create(:user, :member, name: 'version member') }
 
   let!(:tag) { create(:tag, primary_name: 'tag_versions_target', category: :general) }
@@ -240,18 +241,18 @@ RSpec.describe 'TagVersions API', type: :request do
       wiki_tag = create(:tag, primary_tag_name: wiki_tag_name, category: :general)
 
       wiki_page =
-          Wiki::Commit.create_content!(
+          seed_description(
               tag_name: wiki_tag_name,
               body: 'before',
               created_by_user: member,
               message: 'init')
 
-      Wiki::Commit.content!(
-          page: wiki_page,
+      TagDescriptionOperation.update!(
+          tag: wiki_page.tag,
           body: 'after',
-          created_user: member,
+          updated_by_user: member,
           message: 'edit',
-          base_revision_id: wiki_page.current_revision.id)
+          base_revision_id: current_description_version(wiki_page).id)
 
       get '/tags/versions', params: { id: wiki_tag.id }
 
diff --git a/backend/spec/requests/tag_wiki_history_integrity_spec.rb b/backend/spec/requests/tag_wiki_history_integrity_spec.rb
index 665eee2..bd8e7a9 100644
--- a/backend/spec/requests/tag_wiki_history_integrity_spec.rb
+++ b/backend/spec/requests/tag_wiki_history_integrity_spec.rb
@@ -14,7 +14,7 @@ RSpec.describe 'Tag and wiki history integrity', type: :request do
   end
 
   def create_wiki_for_tag! tag:, body: 'wiki body', user: member_user
-    seed_wiki_page(
+    seed_description(
         tag_name: primary_tag_name_for(tag, 'ja'),
         body:,
         created_by_user: user,
@@ -29,7 +29,7 @@ RSpec.describe 'Tag and wiki history integrity', type: :request do
     it 'renames the current Wiki resource without adding body history' do
       tag = create_tag!(name: 'patch_tag_wiki_before')
       wiki_page = create_wiki_for_tag!(tag:, body: 'wiki body before')
-      wiki_history = wiki_page.wiki_versions.map(&:attributes)
+      wiki_history = description_versions(wiki_page).map(&:attributes)
 
       expect {
         patch "/tags/#{ tag.id }", params: {
@@ -37,7 +37,7 @@ RSpec.describe 'Tag and wiki history integrity', type: :request do
         }
       }
           .to change(TagVersion, :count).by(2)
-          .and change(WikiVersion, :count).by(0)
+          .and change(TagDescriptionVersion, :count).by(0)
 
       expect(response).to have_http_status(:ok)
 
@@ -45,16 +45,16 @@ RSpec.describe 'Tag and wiki history integrity', type: :request do
       wiki_page.reload
 
       expect(primary_tag_name_for(tag, 'ja').name).to eq('patch_tag_wiki_after')
-      expect(wiki_page.title).to eq('patch_tag_wiki_after')
+      expect(wiki_page.tag.name('ja')).to eq('patch_tag_wiki_after')
 
-      expect(wiki_page.wiki_versions.reload.map(&:attributes)).to eq(wiki_history)
+      expect(description_versions(wiki_page).reload.map(&:attributes)).to eq(wiki_history)
     end
 
     it 'does not record wiki_version when only category changes' do
       tag = create_tag!(name: 'patch_tag_category_only')
       wiki_page = create_wiki_for_tag!(tag:, body: 'wiki body before')
 
-      before_wiki_versions = wiki_page.wiki_versions.count
+      before_wiki_versions = description_versions(wiki_page).count
 
       expect {
         patch "/tags/#{ tag.id }", params: {
@@ -70,7 +70,7 @@ RSpec.describe 'Tag and wiki history integrity', type: :request do
 
       expect(primary_tag_name_for(tag, 'ja').name).to eq('patch_tag_category_only')
       expect(tag.category).to eq('meme')
-      expect(wiki_page.wiki_versions.count).to eq(before_wiki_versions)
+      expect(description_versions(wiki_page).count).to eq(before_wiki_versions)
     end
   end
 
@@ -78,7 +78,7 @@ RSpec.describe 'Tag and wiki history integrity', type: :request do
     it 'renames the current Wiki resource without adding body history' do
       tag = create_tag!(name: 'put_tag_wiki_before')
       wiki_page = create_wiki_for_tag!(tag:, body: 'wiki body before')
-      wiki_history = wiki_page.wiki_versions.map(&:attributes)
+      wiki_history = description_versions(wiki_page).map(&:attributes)
 
       expect {
         put "/tags/#{ tag.id }", params: {
@@ -90,7 +90,7 @@ RSpec.describe 'Tag and wiki history integrity', type: :request do
         }
       }
           .to change(TagVersion, :count).by(2)
-          .and change(WikiVersion, :count).by(0)
+          .and change(TagDescriptionVersion, :count).by(0)
 
       expect(response).to have_http_status(:ok)
 
@@ -98,16 +98,16 @@ RSpec.describe 'Tag and wiki history integrity', type: :request do
       wiki_page.reload
 
       expect(primary_tag_name_for(tag, 'ja').name).to eq('put_tag_wiki_after')
-      expect(wiki_page.title).to eq('put_tag_wiki_after')
+      expect(wiki_page.tag.name('ja')).to eq('put_tag_wiki_after')
 
-      expect(wiki_page.wiki_versions.reload.map(&:attributes)).to eq(wiki_history)
+      expect(description_versions(wiki_page).reload.map(&:attributes)).to eq(wiki_history)
     end
 
     it 'does not record wiki_version when only category changes' do
       tag = create_tag!(name: 'put_tag_category_only')
       wiki_page = create_wiki_for_tag!(tag:, body: 'wiki body before')
 
-      before_wiki_versions = wiki_page.wiki_versions.count
+      before_wiki_versions = description_versions(wiki_page).count
 
       expect {
         put "/tags/#{ tag.id }", params: {
@@ -127,14 +127,14 @@ RSpec.describe 'Tag and wiki history integrity', type: :request do
 
       expect(primary_tag_name_for(tag, 'ja').name).to eq('put_tag_category_only')
       expect(tag.category).to eq('meme')
-      expect(wiki_page.wiki_versions.count).to eq(before_wiki_versions)
+      expect(description_versions(wiki_page).count).to eq(before_wiki_versions)
     end
 
     it 'does not record wiki_version when only aliases change' do
       tag = create_tag!(name: 'put_tag_alias_only')
       wiki_page = create_wiki_for_tag!(tag:, body: 'wiki body before')
 
-      before_wiki_versions = wiki_page.wiki_versions.count
+      before_wiki_versions = description_versions(wiki_page).count
 
       expect {
         put "/tags/#{ tag.id }", params: {
@@ -148,7 +148,7 @@ RSpec.describe 'Tag and wiki history integrity', type: :request do
           .to change(TagVersion, :count).by(2)
 
       expect(response).to have_http_status(:ok)
-      expect(wiki_page.reload.wiki_versions.count).to eq(before_wiki_versions)
+      expect(description_versions(wiki_page).count).to eq(before_wiki_versions)
     end
   end
 end
diff --git a/backend/spec/requests/tags_spec.rb b/backend/spec/requests/tags_spec.rb
index d30f5e4..897aed4 100644
--- a/backend/spec/requests/tags_spec.rb
+++ b/backend/spec/requests/tags_spec.rb
@@ -2,6 +2,7 @@ require 'cgi'
 require 'rails_helper'
 
 RSpec.describe 'Tags API', type: :request do
+  include WikiRecords
   let!(:tn) { create(:tag_name, name: 'spec_tag') }
   let!(:tag) { create(:tag, primary_tag_name: tn, category: :general) }
   let!(:alias_tn) { create(:tag_name, :alias, name: 'unko', tag:) }
@@ -745,13 +746,13 @@ RSpec.describe 'Tags API', type: :request do
 
       it 'PATCH の名称変更で Wiki の本文履歴を追加しない' do
         wiki_page =
-            Wiki::Commit.create_content!(
+            seed_description(
                 tag_name: primary_tag_name_for(tag, 'ja'),
                 body: 'wiki body before',
                 created_by_user: member_user,
                 message: 'init')
 
-        wiki_history = wiki_page.wiki_versions.map(&:attributes)
+        wiki_history = description_versions(wiki_page).map(&:attributes)
 
         expect {
           patch "/tags/#{ tag.id }", params: {
@@ -759,23 +760,23 @@ RSpec.describe 'Tags API', type: :request do
           }
         }
             .to change(TagVersion, :count).by(2)
-            .and change(WikiVersion, :count).by(0)
+            .and change(TagDescriptionVersion, :count).by(0)
 
         expect(response).to have_http_status(:ok)
 
-        expect(wiki_page.reload.title).to eq('patch_wiki_renamed_tag')
-        expect(wiki_page.wiki_versions.reload.map(&:attributes)).to eq(wiki_history)
+        expect(wiki_page.reload.tag.name('ja')).to eq('patch_wiki_renamed_tag')
+        expect(description_versions(wiki_page).reload.map(&:attributes)).to eq(wiki_history)
       end
 
       it 'tag の category だけを変更しても wiki version は作成しない' do
         wiki_page =
-            Wiki::Commit.create_content!(
+            seed_description(
                 tag_name: primary_tag_name_for(tag, 'ja'),
                 body: 'wiki body before',
                 created_by_user: member_user,
                 message: 'init')
 
-        before_wiki_version_count = wiki_page.reload.wiki_versions.count
+        before_wiki_version_count = description_versions(wiki_page).count
 
         expect {
           patch "/tags/#{ tag.id }", params: {
@@ -784,7 +785,7 @@ RSpec.describe 'Tags API', type: :request do
         }.to change(TagVersion, :count).by(2)
 
         expect(response).to have_http_status(:ok)
-        expect(wiki_page.reload.wiki_versions.count).to eq(before_wiki_version_count)
+        expect(description_versions(wiki_page).count).to eq(before_wiki_version_count)
       end
 
       it 'full update で旧名 alias が残った tag を PATCH で旧名へ戻せる' do
@@ -815,7 +816,7 @@ RSpec.describe 'Tags API', type: :request do
 
       it '別 tag の正規名には変更できない' do
         wiki_page =
-            Wiki::Commit.create_content!(
+            seed_description(
                 tag_name: primary_tag_name_for(tag, 'ja'),
                 body: 'patch collision wiki',
                 created_by_user: member_user,
@@ -831,7 +832,7 @@ RSpec.describe 'Tags API', type: :request do
         expect(primary_tag_name_for(tag.reload, 'ja').name).to eq('spec_tag')
         expect(TagName.where(tag_id: tag.id, language_code: 'ja', primary_flg: false).pluck(:name))
             .to contain_exactly('unko')
-        expect(wiki_page.reload.tag_name).to eq(primary_tag_name_for(tag, 'ja'))
+        expect(wiki_page.reload.tag.tag_name('ja')).to eq(primary_tag_name_for(tag, 'ja'))
       end
 
       it 'system tag の name は変更できない' do
@@ -1209,7 +1210,7 @@ RSpec.describe 'Tags API', type: :request do
         expect(old_name_alias).to have_attributes(
             tag_id: tag.id, language_code: 'ja', primary_flg: false)
 
-        expect(alias_tn.reload.tag_id).to be_nil
+        expect(TagName.exists?(alias_tn.id)).to be(false)
 
         expect(TagName.where(tag_id: tag.parents.select(:id),
                              language_code: 'ja', primary_flg: true).pluck(:name))
@@ -1394,20 +1395,20 @@ RSpec.describe 'Tags API', type: :request do
 
       it 'Wiki を持つ Tag の名称変更で本文履歴を追加しない' do
         wiki_page =
-            Wiki::Commit.create_content!(
+            seed_description(
                 tag_name: primary_tag_name_for(tag, 'ja'),
                 body: 'wiki body before',
                 created_by_user: member_user,
                 message: 'init')
 
-        Wiki::Commit.content!(
-          page: wiki_page,
+        TagDescriptionOperation.update!(
+          tag: wiki_page.tag,
           body: 'wiki body before',
-          created_user: member_user,
+          updated_by_user: member_user,
           message: 'init'
         )
 
-        wiki_history = wiki_page.wiki_versions.map(&:attributes)
+        wiki_history = description_versions(wiki_page).map(&:attributes)
 
         expect {
           put "/tags/#{ tag.id }", params: {
@@ -1419,22 +1420,22 @@ RSpec.describe 'Tags API', type: :request do
           }
         }
             .to change(TagVersion, :count).by(2)
-            .and change(WikiVersion, :count).by(0)
+            .and change(TagDescriptionVersion, :count).by(0)
 
         expect(response).to have_http_status(:ok)
 
-        expect(wiki_page.reload.title).to eq('put_wiki_version_tag')
-        expect(wiki_page.wiki_versions.reload.map(&:attributes)).to eq(wiki_history)
+        expect(wiki_page.reload.tag.name('ja')).to eq('put_wiki_version_tag')
+        expect(description_versions(wiki_page).reload.map(&:attributes)).to eq(wiki_history)
       end
 
       it 'wiki を持つ tag を旧 alias へ戻しても wiki を新しい正本名へ移す' do
         wiki_page =
-            Wiki::Commit.create_content!(
+            seed_description(
                 tag_name: primary_tag_name_for(tag, 'ja'),
                 body: 'wiki body before',
                 created_by_user: member_user,
                 message: 'init')
-        wiki_history = wiki_page.wiki_versions.map(&:attributes)
+        wiki_history = description_versions(wiki_page).map(&:attributes)
 
         expect {
           put "/tags/#{ tag.id }", params: {
@@ -1454,20 +1455,19 @@ RSpec.describe 'Tags API', type: :request do
           }
         }
             .to change(TagVersion, :count).by(3)
-            .and change(WikiVersion, :count).by(0)
+            .and change(TagDescriptionVersion, :count).by(0)
 
         expect(response).to have_http_status(:ok)
 
         tag.reload
 
-        expect(wiki_page.reload.tag_name).to eq(primary_tag_name_for(tag, 'ja'))
-        expect(TagName.find_by!(language_code: 'ja', name: 'put_wiki_roundtrip_b').wiki_page)
-            .to be_nil
+        expect(wiki_page.reload.tag.tag_name('ja')).to eq(primary_tag_name_for(tag, 'ja'))
+        expect(wiki_page.reload.tag_id).to eq(tag.id)
         expect(TagName.find_by!(language_code: 'ja', name: 'put_wiki_roundtrip_b'))
             .to have_attributes(tag_id: tag.id, primary_flg: false)
 
-        expect(wiki_page.title).to eq('spec_tag')
-        expect(wiki_page.wiki_versions.reload.map(&:attributes)).to eq(wiki_history)
+        expect(wiki_page.tag.name('ja')).to eq('spec_tag')
+        expect(description_versions(wiki_page).reload.map(&:attributes)).to eq(wiki_history)
       end
 
       it '別名を他 tag から奪った場合、奪はれた側の tag version も作成する' do
@@ -1520,7 +1520,7 @@ RSpec.describe 'Tags API', type: :request do
             name: 'put_alias_collision_name',
             tag: old_owner)
         wiki_page =
-            Wiki::Commit.create_content!(
+            seed_description(
                 tag_name: primary_tag_name_for(tag, 'ja'),
                 body: 'put collision wiki',
                 created_by_user: member_user,
@@ -1554,7 +1554,7 @@ RSpec.describe 'Tags API', type: :request do
         expect(old_owner_versions.last.event_type).to eq('update')
         expect(version_alias_names(old_owner_versions.last, 'ja'))
             .not_to include('put_alias_collision_name')
-        expect(wiki_page.reload.tag_name).to eq(primary_tag_name_for(tag, 'ja'))
+        expect(wiki_page.reload.tag.tag_name('ja')).to eq(primary_tag_name_for(tag, 'ja'))
       end
 
       it 'parent_tags に指定すると循環する tag は 422 にする' do
@@ -1579,13 +1579,13 @@ RSpec.describe 'Tags API', type: :request do
 
       it 'Tag の名称変更で Wiki の本文履歴を追加しない' do
         wiki_page =
-            Wiki::Commit.create_content!(
+            seed_description(
                 tag_name: primary_tag_name_for(tag, 'ja'),
                 body: 'wiki body before',
                 created_by_user: member_user,
                 message: 'init')
 
-        wiki_history = wiki_page.wiki_versions.map(&:attributes)
+        wiki_history = description_versions(wiki_page).map(&:attributes)
 
         expect {
           put "/tags/#{ tag.id }", params: {
@@ -1597,12 +1597,12 @@ RSpec.describe 'Tags API', type: :request do
           }
         }
             .to change(TagVersion, :count).by(2)
-            .and change(WikiVersion, :count).by(0)
+            .and change(TagDescriptionVersion, :count).by(0)
 
         expect(response).to have_http_status(:ok)
 
-        expect(wiki_page.reload.title).to eq('put_wiki_renamed_tag')
-        expect(wiki_page.wiki_versions.reload.map(&:attributes)).to eq(wiki_history)
+        expect(wiki_page.reload.tag.name('ja')).to eq('put_wiki_renamed_tag')
+        expect(description_versions(wiki_page).reload.map(&:attributes)).to eq(wiki_history)
       end
     end
   end
diff --git a/backend/spec/requests/wiki_conflict_spec.rb b/backend/spec/requests/wiki_conflict_spec.rb
index 8aebaa6..5da7988 100644
--- a/backend/spec/requests/wiki_conflict_spec.rb
+++ b/backend/spec/requests/wiki_conflict_spec.rb
@@ -10,18 +10,18 @@ RSpec.describe 'Wiki conflict handling', type: :request do
 
   it 'returns 409 when base_revision_id is stale' do
     page =
-        seed_wiki_page(
+        seed_description(
             tag_name: create(:tag, primary_name: 'wiki_conflict_request').tag_name('ja'),
             body: 'first',
             created_by_user: user,
             message: 'init')
 
-    stale_id = page.current_revision.id
+    stale_id = current_description_version(page).id
 
-    Wiki::Commit.content!(
-        page:,
+    TagDescriptionOperation.update!(
+        tag: page.tag,
         body: 'second',
-        created_user: user,
+        updated_by_user: user,
         message: 'other edit',
         base_revision_id: stale_id)
 
@@ -36,6 +36,6 @@ RSpec.describe 'Wiki conflict handling', type: :request do
 
     page.reload
     expect(page.body).to eq('second')
-    expect(page.current_revision.message).to eq('other edit')
+    expect(current_description_version(page)).to have_attributes(body: 'second', version_no: 2)
   end
 end
diff --git a/backend/spec/requests/wiki_creation_freeze_spec.rb b/backend/spec/requests/wiki_creation_freeze_spec.rb
index 96e4af4..a51b8ac 100644
--- a/backend/spec/requests/wiki_creation_freeze_spec.rb
+++ b/backend/spec/requests/wiki_creation_freeze_spec.rb
@@ -7,27 +7,11 @@ RSpec.describe 'Wiki creation freeze', type: :request do
   let!(:user) { create_member_user! }
   let(:headers) { { 'X-Transfer-Code' => user.inheritance_code } }
 
-  it 'creates missing compatibility history when updating an independent group' do
-    id = seed_group(name: 'independent', description: 'before')
-    expect do
-      put "/tag_groups/#{ id }", params: {
-          name: 'independent', description: 'after', members: [], placements: [] },
-          headers:, as: :json
-    end.to change(WikiPage, :count).by(1)
-        .and change(WikiRevision, :count).by(1)
-        .and change(WikiVersion, :count).by(1)
-    expect(response).to have_http_status(:ok)
-    expect(TagGroup.find(id).description).to eq('after')
-    page = WikiPage.joins(:tag_name).find_by!(tag_names: { name: 'タググループ:independent' })
-    expect(page.body).to include('after')
-    expect(page.current_revision.body).to eq(page.body)
-    expect(page.wiki_versions.sole.body).to eq(page.body)
-  end
 
   context 'existing description write protection' do
     let!(:tag) { create(:tag, primary_name: 'protected_description') }
     let!(:page) do
-      seed_wiki_page(tag_name: tag.tag_name('ja'), body: 'before', created_by_user: user)
+      seed_description(tag_name: tag.tag_name('ja'), body: 'before', created_by_user: user)
     end
 
     [nil, :guest, :banned].each do |role|
diff --git a/backend/spec/requests/wiki_history_integrity_spec.rb b/backend/spec/requests/wiki_history_integrity_spec.rb
deleted file mode 100644
index 60fda7f..0000000
--- a/backend/spec/requests/wiki_history_integrity_spec.rb
+++ /dev/null
@@ -1,170 +0,0 @@
-require 'cgi'
-require 'rails_helper'
-
-RSpec.describe 'Wiki history integrity', type: :request do
-  include WikiRecords
-  let!(:user) { create_member_user! }
-
-  def auth_headers user
-    { 'X-Transfer-Code' => user.inheritance_code }
-  end
-
-  def create_wiki_page title:, body: 'body', message: 'init', user: self.user
-    seed_wiki_page(
-        tag_name: create(:tag, primary_name: title).tag_name('ja'),
-        body:,
-        created_by_user: user,
-        message:)
-  end
-
-  describe 'POST /wiki' do
-    it 'rejects frozen creation without partial page or history' do
-      expect do
-        post '/wiki', params: { title: 'Help:wiki_history_create_atomic', body: 'initial' },
-             headers: auth_headers(user)
-      end.to change(WikiPage, :count).by(0)
-          .and change(WikiRevision, :count).by(0)
-          .and change(WikiVersion, :count).by(0)
-      expect(response.status).to be_between(400, 499)
-    end
-
-    it 'returns 422 and creates nothing when normalised body is blank' do
-      expect {
-        post '/wiki',
-             params: {
-               title: 'Help:wiki_history_blank_body',
-               body: "\r\n\r\n",
-               message: 'blank',
-             },
-             headers: auth_headers(user)
-      }
-          .not_to change(WikiPage, :count)
-
-      expect(response).to have_http_status(:unprocessable_entity)
-      expect(WikiPage.joins(:tag_name)
-          .where(tag_names: { name: 'Help:wiki_history_blank_body' })).not_to exist
-    end
-
-    it 'rejects frozen creation without modifying an existing page or history' do
-      create_wiki_page(title: 'Help:wiki_history_duplicate_title', body: 'first')
-
-      expect do
-        post '/wiki',
-             params: { title: 'Help:wiki_history_duplicate_title',
-                       body: 'second', message: 'duplicate' },
-             headers: auth_headers(user)
-      end.to change(WikiPage, :count).by(0)
-          .and change(WikiRevision, :count).by(0)
-          .and change(WikiVersion, :count).by(0)
-
-      expect(response.status).to be_between(400, 499)
-      expect(WikiPage.joins(:tag_name)
-          .where(tag_names: { name: 'Help:wiki_history_duplicate_title' }).count).to eq(1)
-    end
-  end
-
-  describe 'PUT /wiki/:id' do
-    it 'updates body and records wiki_revision and wiki_version' do
-      page = create_wiki_page(title: 'wiki_history_update_body', body: 'before')
-      current_id = page.current_revision.id
-
-      expect {
-        put "/wiki/#{ page.id }",
-            params: {
-              title: 'wiki_history_update_body',
-              body: 'after',
-              message: 'edit body',
-              base_revision_id: current_id,
-            },
-            headers: auth_headers(user)
-      }
-          .to change(WikiRevision, :count).by(1)
-          .and change(WikiVersion, :count).by(1)
-
-      expect(response).to have_http_status(:ok)
-
-      page.reload
-      version = page.wiki_versions.order(:version_no).last
-
-      expect(page.title).to eq('wiki_history_update_body')
-      expect(page.body).to eq('after')
-
-      expect(version).to have_attributes(
-        event_type: 'update',
-        title: 'wiki_history_update_body',
-        body: 'after',
-        reason: 'edit body',
-        created_by_user_id: user.id
-      )
-    end
-
-    it 'renames title and records wiki_version with new title' do
-      page = create_wiki_page(title: 'wiki_history_rename_before', body: 'before')
-      current_id = page.current_revision.id
-
-      expect {
-        put "/wiki/#{ page.id }",
-            params: {
-              title: 'wiki_history_rename_after',
-              body: 'after',
-              message: 'rename',
-              base_revision_id: current_id,
-            },
-            headers: auth_headers(user)
-      }
-          .to change(WikiRevision, :count).by(1)
-          .and change(WikiVersion, :count).by(1)
-
-      expect(response).to have_http_status(:ok)
-
-      page.reload
-      version = page.wiki_versions.order(:version_no).last
-
-      expect(page.title).to eq('wiki_history_rename_after')
-      expect(page.body).to eq('after')
-
-      expect(version).to have_attributes(
-        event_type: 'update',
-        title: 'wiki_history_rename_after',
-        body: 'after',
-        reason: 'rename',
-        created_by_user_id: user.id
-      )
-    end
-
-    it 'does not change title, body, revision, or version on stale base_revision_id' do
-      page = create_wiki_page(title: 'wiki_history_conflict_page', body: 'first')
-      stale_id = page.current_revision.id
-
-      Wiki::Commit.content!(
-          page:,
-          body: 'second',
-          created_user: user,
-          message: 'other edit',
-          base_revision_id: stale_id)
-
-      page.reload
-      current_title = page.title
-      current_body = page.body
-      revision_count = page.wiki_revisions.count
-      version_count = page.wiki_versions.count
-
-      put "/wiki/#{ page.id }",
-          params: {
-            title: 'wiki_history_conflict_renamed',
-            body: 'third',
-            message: 'stale edit',
-            base_revision_id: stale_id,
-          },
-          headers: auth_headers(user)
-
-      expect(response).to have_http_status(:conflict)
-
-      page.reload
-      expect(page.title).to eq(current_title)
-      expect(page.body).to eq(current_body)
-      expect(page.wiki_revisions.count).to eq(revision_count)
-      expect(page.wiki_versions.count).to eq(version_count)
-    end
-  end
-end
diff --git a/backend/spec/requests/wiki_index_order_spec.rb b/backend/spec/requests/wiki_index_order_spec.rb
index c5ce7e9..9d9dd24 100644
--- a/backend/spec/requests/wiki_index_order_spec.rb
+++ b/backend/spec/requests/wiki_index_order_spec.rb
@@ -28,15 +28,15 @@ RSpec.describe 'Wiki resource ordering', type: :request do
   it 'breaks timestamp ties by resource kind and ID while retaining legacy overlaps' do
     time = Time.utc(2026, 1, 1)
     tag = create(:tag, primary_name: 'tied')
-    TagDescription.create!(id: 51, tag:, language_code: 'ja', body: 'current',
+    description = TagDescription.create!(tag:, language_code: 'ja', body: 'current',
                            version_no: 1, updated_at: time)
-    group = TagGroup.find(seed_group(name: 'tied', id: 51))
+    group = TagGroup.find(seed_group(name: 'tied', id: description.id))
     group.update_columns(updated_at: time)
 
     2.times do
       get '/wiki', params: { title: 'tied' }
       expect(json.map { [_1.fetch('resource_type'), _1.fetch('id')] })
-          .to eq([['tag_description', 51], ['tag_group', 51]])
+          .to eq([['tag_description', description.id], ['tag_group', description.id]])
     end
   end
 end
diff --git a/backend/spec/requests/wiki_spec.rb b/backend/spec/requests/wiki_spec.rb
index 377f851..e3d7735 100644
--- a/backend/spec/requests/wiki_spec.rb
+++ b/backend/spec/requests/wiki_spec.rb
@@ -19,7 +19,7 @@ RSpec.describe 'Wiki API', type: :request do
         deprecated_at: Time.zone.local(2026, 6, 1))
   end
   let!(:page) do
-    seed_wiki_page(
+    seed_description(
         tag_name: tn,
         body: 'init',
         created_by_user: user,
@@ -113,9 +113,9 @@ RSpec.describe 'Wiki API', type: :request do
       it "rejects frozen creation of #{ title } without history writes" do
         expect do
           post endpoint, params: { title:, body: 'initial' }, headers: auth_headers(member)
-        end.to change(WikiPage, :count).by(0)
-            .and change(WikiRevision, :count).by(0)
-            .and change(WikiVersion, :count).by(0)
+        end.to change(TagDescription, :count).by(0)
+            .and change(TagDescriptionVersion, :count).by(0)
+
         expect(response.status).to be_between(400, 499)
       end
     end
@@ -132,7 +132,7 @@ RSpec.describe 'Wiki API', type: :request do
     let!(:test_tag_name) { create(:tag, primary_name: 'TestPage').tag_name('ja') }
 
     let!(:page) do
-      seed_wiki_page(
+      seed_description(
           tag_name: test_tag_name,
           body: "a\nb",
           created_by_user: member,
@@ -166,7 +166,7 @@ RSpec.describe 'Wiki API', type: :request do
 
     context 'when success' do
       it 'creates new revision and returns 200' do
-        current_id = page.wiki_revisions.maximum(:id)
+        current_id = description_versions(page).maximum(:id)
 
         expect do
           put "/wiki/#{page.id}",
@@ -174,26 +174,22 @@ RSpec.describe 'Wiki API', type: :request do
                         base_revision_id: current_id },
               headers: auth_headers(member)
         end
-            .to change(WikiRevision, :count).by(1)
-            .and change(WikiVersion, :count).by(1)
+            .to change(TagDescriptionVersion, :count).by(1)
 
-        version = page.wiki_versions.order(:version_no).last
+
+        version = description_versions(page).order(:version_no).last
 
         expect(version).to have_attributes(
           event_type: 'update',
-          title: 'TestPage',
           body: "x\ny",
-          created_by_user_id: member.id
-        )
+          created_by_user_id: member.id)
 
         expect(response).to have_http_status(:ok)
 
         page.reload
-        rev = page.current_revision
-        expect(rev).to be_content
-        expect(rev.message).to eq('edit')
+        rev = current_description_version(page)
         expect(page.body).to eq("x\ny")
-        expect(rev.base_revision_id).to eq(current_id)
+        expect(rev.version_no).to eq(2)
       end
 
       it 'wiki body だけを変更しても tag version は作成しない' do
@@ -206,13 +202,13 @@ RSpec.describe 'Wiki API', type: :request do
             created_by_user: member)
 
         linked_page =
-            seed_wiki_page(
+            seed_description(
                 tag_name: linked_tag_name,
                 body: 'before',
                 created_by_user: member,
                 message: 'init')
 
-        current_id = linked_page.current_revision.id
+        current_id = current_description_version(linked_page).id
         before_count = linked_tag.reload.tag_versions.count
 
         expect {
@@ -225,8 +221,8 @@ RSpec.describe 'Wiki API', type: :request do
               },
               headers: auth_headers(member)
         }
-            .to change(WikiRevision, :count).by(1)
-            .and change(WikiVersion, :count).by(1)
+            .to change(TagDescriptionVersion, :count).by(1)
+
 
         expect(response).to have_http_status(:ok)
         expect(linked_tag.reload.tag_versions.count).to eq(before_count)
@@ -236,10 +232,10 @@ 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
-        Wiki::Commit.content!(page: page, body: "zzz", created_user: member, message: 'other edit')
+        TagDescriptionOperation.update!(tag: page.tag, body: "zzz", updated_by_user: member, message: 'other edit')
         page.reload
 
-        stale_id = page.wiki_revisions.order(:id).first.id # わざと古い id
+        stale_id = description_versions(page).order(:id).first.id # わざと古い id
         put "/wiki/#{page.id}",
             params: { title: 'TestPage', body: 'x', base_revision_id: stale_id },
             headers: auth_headers(member)
@@ -281,13 +277,13 @@ RSpec.describe 'Wiki API', type: :request do
   describe 'GET /wiki/search' do
     before do
       search_tag = create(:tag, primary_name: 'spec_wiki_title_2')
-      seed_wiki_page(
+      seed_description(
           tag_name: search_tag.tag_name('ja'),
           body: 'search body 2',
           created_by_user: user,
           message: 'init')
 
-      seed_wiki_page(
+      seed_description(
           tag_name: create(:tag_name, name: 'unrelated_title'),
           body: 'unrelated body',
           created_by_user: user,
@@ -318,13 +314,13 @@ RSpec.describe 'Wiki API', type: :request do
 
   describe 'GET /wiki/changes' do
     let!(:rev1) do
-      Wiki::Commit.content!(page: page, body: "a\nb", created_user: user, message: 'r1')
-      page.current_revision
+      TagDescriptionOperation.update!(tag: page.tag, body: "a\nb", updated_by_user: user, message: 'r1')
+      current_description_version(page)
     end
 
     let!(:rev2) do
-      Wiki::Commit.content!(page: page, body: "a\nc", created_user: user, message: 'r2')
-      page.current_revision
+      TagDescriptionOperation.update!(tag: page.tag, body: "a\nc", updated_by_user: user, message: 'r2')
+      current_description_version(page)
     end
 
     it 'returns latest revisions (optionally filtered by page id)' do
@@ -359,11 +355,8 @@ RSpec.describe 'Wiki API', type: :request 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
-      p2 = WikiPage.create!(
-          tag_name: tn2,
-          body: 'init',
-          created_user: user,
-          updated_user: user)
+      p2 = TagDescription.create!(
+          tag: tn2.tag, language_code: 'ja', body: 'init', version_no: 1)
 
       get "/wiki/changes?id=#{p2.id}"
       expect(response).to have_http_status(:ok)
@@ -399,13 +392,13 @@ RSpec.describe 'Wiki API', type: :request do
 
   describe 'GET /wiki/:id/diff' do
     let!(:rev_a) do
-      Wiki::Commit.content!(page: page, body: "a\nb\nc", created_user: user, message: 'A')
-      page.current_revision
+      TagDescriptionOperation.update!(tag: page.tag, body: "a\nb\nc", updated_by_user: user, message: 'A')
+      current_description_version(page)
     end
 
     let!(:rev_b) do
-      Wiki::Commit.content!(page: page, body: "a\nx\nc", created_user: user, message: 'B')
-      page.current_revision
+      TagDescriptionOperation.update!(tag: page.tag, body: "a\nx\nc", updated_by_user: user, message: 'B')
+      current_description_version(page)
     end
 
     it 'returns diff json between revisions' do
@@ -431,44 +424,23 @@ RSpec.describe 'Wiki API', type: :request do
 
       expect(response).to have_http_status(:ok)
       expect(json['older_revision_id']).to eq(rev_a.id)
-      expect(json['newer_revision_id']).to eq(page.current_revision.id)
+      expect(json['newer_revision_id']).to eq(current_description_version(page).id)
     end
   end
 
-  describe 'Wiki::Commit.redirect!' do
-    it 'raises because redirect revisions are deprecated' do
-      target_tag_name = create(:tag_name, name: 'redirect_deprecated_target')
-      target =
-          seed_wiki_page(
-              tag_name: target_tag_name,
-              body: 'target',
-              created_by_user: user,
-              message: 'init')
-
-      expect {
-        Wiki::Commit.redirect!(
-          page: page,
-          redirect_page: target,
-          created_user: user,
-          message: 'redirect',
-          base_revision_id: page.current_revision.id
-        )
-      }.to raise_error(RuntimeError, '廃止しました．')
-    end
-  end
 
   it 'wiki title を変更すると対応する tag の version を作成する' do
     linked_tag_name = create(:tag_name, name: 'wiki_linked_tag_for_version')
     linked_tag = create(:tag, primary_tag_name: linked_tag_name, category: :general)
 
     linked_page =
-        seed_wiki_page(
+        seed_description(
             tag_name: linked_tag_name,
             body: 'before',
             created_by_user: user,
             message: 'init')
 
-    current_id = linked_page.current_revision.id
+    current_id = current_description_version(linked_page).id
 
     expect {
       put "/wiki/#{ linked_page.id }",
@@ -480,8 +452,8 @@ RSpec.describe 'Wiki API', type: :request do
           },
           headers: auth_headers(user)
     }
-        .to change(WikiRevision, :count).by(1)
-        .and change(WikiVersion, :count).by(1)
+        .to change(TagDescriptionVersion, :count).by(1)
+
         .and change { linked_tag.reload.tag_versions.count }.by(2)
 
     expect(response).to have_http_status(:ok)
diff --git a/backend/spec/requests/wiki_title_collision_spec.rb b/backend/spec/requests/wiki_title_collision_spec.rb
index d61122f..f6f3011 100644
--- a/backend/spec/requests/wiki_title_collision_spec.rb
+++ b/backend/spec/requests/wiki_title_collision_spec.rb
@@ -9,7 +9,7 @@ RSpec.describe 'Wiki title collision', type: :request do
   end
 
   def create_wiki_page title:, body:
-    seed_wiki_page(
+    seed_description(
         tag_name: create(:tag_name, name: title),
         body:,
         created_by_user: user,
@@ -20,9 +20,9 @@ RSpec.describe 'Wiki title collision', type: :request do
     source = create_wiki_page(title: 'wiki_collision_source', body: 'source body')
     create_wiki_page(title: 'wiki_collision_target', body: 'target body')
 
-    source_revision_count = source.wiki_revisions.count
-    source_version_count = source.wiki_versions.count
-    old_title = source.title
+    source_revision_count = description_versions(source).count
+    source_version_count = description_versions(source).count
+    old_title = source.tag.reload.name('ja')
     old_body = source.body
 
     put "/wiki/#{ source.id }",
@@ -30,7 +30,7 @@ RSpec.describe 'Wiki title collision', type: :request do
           title: 'wiki_collision_target',
           body: 'new body',
           message: 'rename collision',
-          base_revision_id: source.current_revision.id,
+          base_revision_id: current_description_version(source).id,
         },
         headers: auth_headers(user)
 
@@ -38,10 +38,10 @@ RSpec.describe 'Wiki title collision', type: :request do
 
     source.reload
 
-    expect(source.title).to eq(old_title)
+    expect(source.tag.reload.name('ja')).to eq(old_title)
     expect(source.body).to eq(old_body)
-    expect(source.wiki_revisions.count).to eq(source_revision_count)
-    expect(source.wiki_versions.count).to eq(source_version_count)
+    expect(description_versions(source).count).to eq(source_revision_count)
+    expect(description_versions(source).count).to eq(source_version_count)
   end
 
   it 'rejects frozen creation with an existing title without adding history' do
@@ -52,9 +52,8 @@ RSpec.describe 'Wiki title collision', type: :request do
            params: { title: 'Help:wiki_collision_create', body: 'new body',
                      message: 'duplicate create' },
            headers: auth_headers(user)
-    end.to change(WikiPage, :count).by(0)
-        .and change(WikiRevision, :count).by(0)
-        .and change(WikiVersion, :count).by(0)
+    end.to change(TagDescription, :count).by(0)
+        .and change(TagDescriptionVersion, :count).by(0)
 
     expect(response.status).to be_between(400, 499)
   end
diff --git a/backend/spec/requests/wiki_unmigrated_contract_spec.rb b/backend/spec/requests/wiki_unmigrated_contract_spec.rb
index e60c8e0..869be12 100644
--- a/backend/spec/requests/wiki_unmigrated_contract_spec.rb
+++ b/backend/spec/requests/wiki_unmigrated_contract_spec.rb
@@ -1,78 +1,25 @@
 require 'rails_helper'
 
-RSpec.describe 'Unmigrated Wiki compatibility', type: :request do
-  include WikiRecords
-  let!(:user) { create_member_user! }
-  let!(:tag_name) { create(:tag_name, name: 'Help_contract') }
-  let!(:page) do
-    seed_wiki_page(tag_name:, body: 'before', created_by_user: user)
-  end
-  let!(:first_revision) { page.current_revision }
-  let!(:last_revision) do
-    Wiki::Commit.legacy_content!(page:, body: 'after', created_user: user,
-                                 message: 'legacy edit', base_revision_id: first_revision.id)
-  end
-
-  before { expect(TagDescription.exists?(id: page.id)).to be(false) }
-
-  it 'rejects standalone updates even after a Tag is linked to the legacy page' do
-    create(:tag, primary_tag_name: tag_name)
-    original = page.reload.attributes
-
-    expect do
-      put "/wiki/#{ page.id }",
-          params: { title: 'legacy_tag_renamed', body: 'changed legacy body',
-                    message: 'legacy rename', base_revision_id: last_revision.id },
-          headers: { 'X-Transfer-Code' => user.inheritance_code }
-    end.to change(WikiRevision, :count).by(0)
-        .and change(WikiVersion, :count).by(0)
-        .and change(TagDescription, :count).by(0)
-        .and change(TagDescriptionVersion, :count).by(0)
-
-    expect(response).to have_http_status(:unprocessable_entity)
-    expect(page.reload.attributes).to eq(original)
-    expect(page.current_revision).to have_attributes(message: 'legacy edit')
-  end
-
+RSpec.describe 'Removed standalone Wiki resources', type: :request do
   include TagGroupRecords
+  let(:user) { create_member_user! }
 
-  [:id, :title].each do |lookup|
-    [nil, :historical].each do |edition|
-      it "rejects legacy #{ lookup } #{ edition || 'current' } without legacy SELECTs" do
-        path = lookup == :id ? "/wiki/#{ page.id }" : "/wiki/title/#{ tag_name.name }"
-        params = edition ? { version: first_revision.id } : { }
-        without_group_legacy_reads { get path, params: }
-        expect(response).to have_http_status(:not_found)
-      end
-    end
-
-    it "does not recognise legacy #{ lookup } existence" do
-      path = lookup == :id ? "/wiki/#{ page.id }" : "/wiki/title/#{ tag_name.name }"
-      without_group_legacy_reads { get "#{ path }/exists" }
-      expect(response).to have_http_status(:not_found)
-    end
-  end
-
-  ['/wiki', '/wiki/search', '/wiki/changes'].each do |path|
-    it "excludes unmigrated content from #{ path } without legacy SELECTs" do
+  ['Help:old', 'ヘルプ:旧ページ'].each do |title|
+    it "does not resolve #{ title } as a Wiki resource" do
+      path = "/wiki/title/#{ CGI.escapeURIComponent(title) }"
       without_group_legacy_reads { get path }
-      expect(response).to have_http_status(:ok)
-      expect(json).to eq([])
-    end
-  end
-
-  it 'returns empty scoped history without legacy SELECTs' do
-    without_group_legacy_reads { get '/wiki/changes', params: { id: page.id } }
-    expect(response).to have_http_status(:ok)
-    expect(json).to eq([])
-  end
-
-  [false, true].each do |explicit|
-    it "rejects legacy diff with #{ explicit ? 'explicit' : 'current' } target" do
-      params = { from: first_revision.id }
-      params[:to] = last_revision.id if explicit
-      without_group_legacy_reads { get "/wiki/#{ page.id }/diff", params: }
       expect(response).to have_http_status(:not_found)
+      get "#{ path }/exists"
+      expect(response).to have_http_status(:not_found)
+    end
+
+    it "rejects standalone creation of #{ title } without writes" do
+      user
+      before_state = group_state
+      post '/wiki', params: { title:, body: 'body' },
+           headers: { 'X-Transfer-Code' => user.inheritance_code }
+      expect(response).to have_http_status(:unprocessable_entity)
+      expect(group_state).to eq(before_state)
     end
   end
 end
diff --git a/backend/spec/services/shared_resource_id_allocator_mysql_spec.rb b/backend/spec/services/shared_resource_id_allocator_mysql_spec.rb
index 40f9559..a6d908f 100644
--- a/backend/spec/services/shared_resource_id_allocator_mysql_spec.rb
+++ b/backend/spec/services/shared_resource_id_allocator_mysql_spec.rb
@@ -9,9 +9,9 @@ RSpec.describe 'Shared resource IDs across MySQL connections', type: :model do
     expect(ApplicationRecord.connection.adapter_name).to match(/mysql/i)
     expect(ApplicationRecord.connection_pool.size).to be >= 3
     @prefix = "shared_ids_#{ SecureRandom.hex(8) }"
-    @names = [0, 1].map { create(:tag_name, name: "#{ @prefix }_#{ _1 }") }
-    @tag = Tag.create!(tag_name_id: @names.first.id, category: :general)
-    @names.first.update!(tag_id: @tag.id)
+    @tag = create(:tag, primary_name: "#{ @prefix }_owner")
+    @group = TagGroup.create!(name: "#{ @prefix }_owner", version_no: 1)
+    @tag_ids = Queue.new
     @threads = []
     @release = Queue.new
   end
@@ -23,17 +23,21 @@ RSpec.describe 'Shared resource IDs across MySQL connections', type: :model do
         raise 'Shared ID worker did not finish' unless thread.join(15)
       end
     ensure
+      TagDescriptionVersion.where(tag_id: @tag.id).delete_all if @tag
+      if @group
+        TagGroupVersion.where(tag_group_id: @group.id).delete_all
+        @group.delete
+      end
       if @prefix
         ExternalTag.where(name: "#{ @prefix }_external").delete_all
         TagGroup.where(name: "#{ @prefix }_group").delete_all
       end
       TagDescription.where(tag_id: @tag.id).delete_all if @tag
-      if @names
-        ids = @names.map(&:id)
-        TagName.where(id: ids).update_all(tag_id: nil)
-        Tag.where(tag_name_id: ids).delete_all
-        TagName.where(id: ids).delete_all
-      end
+      ids = []
+      ids << @tag_ids.pop until @tag_ids.empty? if @tag_ids
+      ids << @tag.id if @tag
+      TagName.where(tag_id: ids).delete_all
+      Tag.where(id: ids).delete_all
     end
   end
 
@@ -51,11 +55,19 @@ RSpec.describe 'Shared resource IDs across MySQL connections', type: :model do
   def create_resource kind
     case kind
     when :tag
-      Tag.create!(tag_name_id: @names.last.id, category: :general)
+      Tag.create!(category: :general).tap { @tag_ids << _1.id }
     when :external
       ExternalTag.create!(platform: :nico, name: "#{ @prefix }_external")
     when :description
       TagDescription.create!(tag: @tag, language_code: 'ja', body: '', version_no: 1)
+    when :description_version
+      TagDescriptionVersion.create!(
+          tag_id: @tag.id, language_code: 'ja', body: 'body', version_no: 1,
+          event_type: 'create', created_at: Time.current)
+    when :group_version
+      TagGroupVersion.create!(
+          tag_group: @group, name: @group.name, version_no: 1, event_type: 'create',
+          members: [], placements: [], created_at: Time.current)
     when :group
       TagGroup.create!(name: "#{ @prefix }_group", version_no: 1)
     end
@@ -88,7 +100,8 @@ RSpec.describe 'Shared resource IDs across MySQL connections', type: :model do
     thread.value
   end
 
-  { tags: [:external, :tag], wiki: [:description, :group] }.each do |space, kinds|
+  { tags: [:external, :tag], wiki: [:description, :group],
+    wiki_history: [:description_version, :group_version] }.each do |space, kinds|
     [false, true].each do |rollback|
       it "serialises #{ space } inserts through #{ rollback ? 'rollback' : 'commit' }" do
         tables = SharedResourceIdAllocator::SPACES.fetch(space.to_s)
@@ -96,7 +109,7 @@ RSpec.describe 'Shared resource IDs across MySQL connections', type: :model do
           ApplicationRecord.connection.select_value("SELECT MAX(id) FROM #{ table }").to_i
         end
         first, (first_id, connection_id, lock_name) = hold_creation(kinds.first, rollback:)
-        expect(first_id).to eq(maxima.max + 1)
+        expect(first_id).to be > maxima.max
         connection = ApplicationRecord.connection
         quoted_lock = connection.quote(lock_name)
         expect(connection.select_value("SELECT IS_USED_LOCK(#{ quoted_lock })").to_i)
@@ -110,7 +123,7 @@ RSpec.describe 'Shared resource IDs across MySQL connections', type: :model do
         expect(await_queue(started)).not_to eq(connection_id)
         @release << true
         expect(result(first)).to eq(first_id)
-        expect(result(second)).to eq(rollback ? first_id : first_id + 1)
+        expect(result(second)).to be > first_id
         expect(connection.select_value("SELECT IS_FREE_LOCK(#{ quoted_lock })").to_i).to eq(1)
       end
     end
diff --git a/backend/spec/services/shared_resource_id_allocator_spec.rb b/backend/spec/services/shared_resource_id_allocator_spec.rb
index 823fb4a..a972036 100644
--- a/backend/spec/services/shared_resource_id_allocator_spec.rb
+++ b/backend/spec/services/shared_resource_id_allocator_spec.rb
@@ -1,6 +1,100 @@
 require 'rails_helper'
 
 RSpec.describe SharedResourceIdAllocator do
+  let(:tag) { create(:tag) }
+
+  def resource table, id: nil, number: 1
+    case table
+    when 'tags'
+      Tag.new(id:, category: :general)
+    when 'external_tags'
+      ExternalTag.new(id:, platform: :nico, name: "external #{ number }")
+    when 'tag_descriptions'
+      TagDescription.new(id:, tag:, language_code: 'ja', body: 'body', version_no: number)
+    when 'tag_groups'
+      TagGroup.new(id:, name: "group #{ number }", version_no: number)
+    when 'tag_description_versions'
+      TagDescriptionVersion.new(
+          id:, tag_id: tag.id, language_code: 'ja', body: 'body', version_no: number,
+          event_type: 'create', created_at: Time.current)
+    when 'tag_group_versions'
+      TagGroupVersion.new(
+          id:, tag_group_id: group.id, name: group.name, version_no: number,
+          event_type: 'create', members: [], placements: [], created_at: Time.current)
+    end
+  end
+
+  let(:group) { TagGroup.create!(name: 'history owner', version_no: 1) }
+
+  described_class::SPACES.each do |space, tables|
+    tables.permutation.each do |first_table, second_table|
+      it "keeps deleted #{ first_table } IDs reserved for #{ second_table }" do
+        first = resource(first_table)
+        first.save!
+        used_id = first.id
+        first.class.where(id: first.id).delete_all
+        second = resource(second_table)
+        second.save!
+        expect(second.id).to be > used_id
+      end
+
+      it "advances #{ space } after an explicit INSERT in #{ first_table }" do
+        first = resource(first_table)
+        first.save!
+        high = first.id + 100
+        explicit = resource(first_table, id: high, number: 2)
+        first.class.where(id: first.id).delete_all
+        explicit.save!
+        explicit.class.where(id: explicit.id).delete_all
+        second = resource(second_table)
+        second.save!
+        expect(second.id).to be > high
+      end
+    end
+
+    it "rejects explicit IDs below the reserved #{ space } position" do
+      first = resource(tables.first)
+      first.save!
+      first.class.where(id: first.id).delete_all
+      expect { resource(tables.last, id: first.id).save! }
+          .to raise_error(ActiveRecord::RecordNotUnique)
+    end
+
+    it "preserves historical #{ space } overlaps without repairing them" do
+      first = resource(tables.first)
+      first.save!
+      second = resource(tables.last)
+      second.save!
+      second.class.where(id: second.id).update_all(id: first.id)
+      second = second.class.find(first.id)
+      snapshots = [first.reload.attributes, second.reload.attributes]
+      next_record = resource(tables.last, number: 2)
+      next_record.save!
+      expect(next_record.id).to be > first.id
+      expect(first.reload.attributes).to eq(snapshots.first)
+      expect(second.reload.attributes).to eq(snapshots.last)
+    end
+  end
+
+  it 'reserves a Tag ID referenced only by remaining description history' do
+    high = [Tag.maximum(:id).to_i, ExternalTag.maximum(:id).to_i].max + 1000
+    TagDescriptionVersion.create!(
+        tag_id: high, language_code: 'ja', version_no: 1, body: 'history',
+        event_type: 'create', created_at: Time.current)
+    expect(create(:tag).id).to be > high
+    expect(create(:external_tag).id).to be > high
+  end
+
+  it 'reserves a group ID referenced only by remaining group history' do
+    high = [TagGroup.maximum(:id).to_i, TagDescription.maximum(:id).to_i].max + 1000
+    version = resource('tag_group_versions')
+    version.save!
+    TagGroupVersion.where(id: version.id).update_all(tag_group_id: high)
+    expect(TagGroup.create!(name: 'replacement', version_no: 1).id).to be > high
+  end
+end
+
+RSpec.describe SharedResourceIdAllocator, 'lock lifecycle' do
   let(:record) { build(:external_tag) }
   let(:connection) { double('connection') }
   let(:transaction) { double('transaction', open?: true) }
@@ -11,6 +105,14 @@ RSpec.describe SharedResourceIdAllocator do
     config = double('config', database: 'test_shared_ids')
     allow(connection).to receive_message_chain(:pool, :db_config).and_return(config)
     allow(connection).to receive(:quote) { "'#{ _1 }'" }
+    allow(connection).to receive(:quote_column_name) { "`#{ _1 }`" }
+    allow(connection).to receive(:execute) { sql << _1 }
+    allow(connection).to receive(:select_all) do |statement|
+      tables = described_class::SPACES.values.flatten.select do |table|
+        statement.include?("'#{ table }'")
+      end
+      tables.map { { 'TABLE_NAME' => _1, 'ENGINE' => 'InnoDB', 'AUTO_INCREMENT' => 9 } }
+    end
     allow(connection).to receive(:quote_table_name) { "`#{ _1 }`" }
     allow(connection).to receive(:select_value) do |statement|
       sql << statement
@@ -35,7 +137,6 @@ RSpec.describe SharedResourceIdAllocator do
       described_class.assign!(record)
       expect(record.id).to eq(9)
       expect(sql.grep(/RELEASE_LOCK/)).to be_empty
-      expect(sql.grep(/FOR UPDATE/).size).to eq(2)
       callbacks.fetch(event).call
       expect(sql.grep(/RELEASE_LOCK/).size).to eq(1)
     end
@@ -49,22 +150,22 @@ RSpec.describe SharedResourceIdAllocator do
   end
 
   it 'releases a successfully acquired lock when allocation fails and rolls back' do
-    allow(connection).to receive(:select_value).with(/FOR UPDATE/).and_raise('query failed')
+    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
     expect(sql.grep(/RELEASE_LOCK/).size).to eq(1)
   end
 
-  it 'preserves explicitly supplied historical IDs' do
-    record.id = 5
+  it 'accepts an explicit ID above the reserved position' do
+    record.id = 50
     described_class.assign!(record)
-    expect(record.id).to eq(5)
+    expect(record.id).to eq(50)
     expect(sql.grep(/FOR UPDATE/)).to be_empty
     callbacks.fetch(:after_commit).call
   end
 
   it 'uses the same named lock within each space and different locks between spaces' do
-    locks = [Tag, ExternalTag, TagDescription, TagGroup].map do |model|
+    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
@@ -76,7 +177,8 @@ RSpec.describe SharedResourceIdAllocator do
     end
     expect(locks[0]).to eq(locks[1])
     expect(locks[2]).to eq(locks[3])
-    expect(locks[0]).not_to eq(locks[2])
+    expect(locks[4]).to eq(locks[5])
+    expect([locks[0], locks[2], locks[4]].uniq.size).to eq(3)
   end
 
   it 'reports lock release failures' do
diff --git a/backend/spec/services/wiki/commit_integrity_spec.rb b/backend/spec/services/wiki/commit_integrity_spec.rb
deleted file mode 100644
index e58a60c..0000000
--- a/backend/spec/services/wiki/commit_integrity_spec.rb
+++ /dev/null
@@ -1,185 +0,0 @@
-require 'digest'
-require 'rails_helper'
-
-RSpec.describe Wiki::Commit do
-  include WikiRecords
-  let(:user) { create_member_user! }
-
-  def create_page title:, body: 'initial body'
-    seed_wiki_page(
-        tag_name: create(:tag, primary_name: title).tag_name('ja'),
-        body:,
-        created_by_user: user,
-        message: 'init')
-  end
-
-  describe '.create_content!' do
-    it 'rejects standalone Help creation without adding page or history' do
-      name = create(:tag_name, name: 'Help:frozen_service')
-      counts = [WikiPage.count, WikiRevision.count, WikiVersion.count]
-      expect do
-        described_class.create_content!(tag_name: name, body: 'initial', created_by_user: user)
-      end.to raise_error(ActiveRecord::RecordInvalid)
-      expect([WikiPage.count, WikiRevision.count, WikiVersion.count]).to eq(counts)
-    end
-
-    it 'keeps the internal compatibility writer available' do
-      name = create(:tag_name, name: 'タググループ:compatibility_service')
-      page = nil
-      expect do
-        page = described_class.create_legacy_content!(
-            tag_name: name, body: 'initial', created_by_user: user)
-      end.to change(WikiPage, :count).by(1)
-          .and change(WikiRevision, :count).by(1)
-          .and change(WikiVersion, :count).by(1)
-      expect(page.current_revision.body).to eq('initial')
-      expect(page.wiki_versions.sole.body).to eq('initial')
-    end
-
-    it 'rejects body that becomes blank after normalisation' do
-      tag_name = create(:tag, primary_name: 'commit_integrity_blank').tag_name('ja')
-
-      expect {
-        described_class.create_content!(
-            tag_name:,
-            body: "\r\n\r\n",
-            created_by_user: user,
-            message: 'blank')
-      }
-          .to raise_error(ActiveRecord::RecordInvalid)
-
-      expect(WikiPage.where(tag_name:)).not_to exist
-    end
-  end
-
-  describe '.content!' do
-    it 'rejects standalone Help updates without modifying histories' do
-      page = seed_wiki_page(tag_name: create(:tag_name, name: 'Help:standalone'),
-                            body: 'before', created_by_user: user)
-      counts = [WikiRevision.count, WikiVersion.count]
-      expect do
-        described_class.content!(page:, body: 'after', created_user: user)
-      end.to raise_error(ActiveRecord::RecordInvalid)
-      expect(page.reload.body).to eq('before')
-      expect([WikiRevision.count, WikiVersion.count]).to eq(counts)
-    end
-
-    it 'updates page body, revision, and version' do
-      page = create_page(title: 'commit_integrity_update', body: 'before')
-      current_id = page.current_revision.id
-
-      expect {
-        described_class.content!(
-            page:,
-            body: 'after',
-            created_user: user,
-            message: 'edit',
-            base_revision_id: current_id)
-      }
-          .to change(WikiRevision, :count).by(1)
-          .and change(WikiVersion, :count).by(1)
-
-      page.reload
-      version = page.wiki_versions.order(:version_no).last
-
-      expect(page.body).to eq('after')
-      expect(version.body).to eq('after')
-      expect(version.reason).to eq('edit')
-    end
-
-    it 'does not record tag_version on body-only wiki update' do
-      tag_name = create(:tag_name, name: 'commit_integrity_linked_tag')
-      tag = create(:tag, primary_tag_name: tag_name, category: :general)
-
-      page =
-          seed_wiki_page(
-              tag_name:,
-              body: 'before',
-              created_by_user: user,
-              message: 'init')
-
-      TagVersionRecorder.record!(
-          tag:,
-          event_type: :create,
-          created_by_user: user)
-
-      before_count = tag.reload.tag_versions.count
-
-      described_class.content!(
-          page:,
-          body: 'after',
-          created_user: user,
-          message: 'edit',
-          base_revision_id: page.current_revision.id)
-
-      expect(tag.reload.tag_versions.count).to eq(before_count)
-    end
-
-    it 'raises conflict and leaves page, revision, and version unchanged' do
-      page = create_page(title: 'commit_integrity_conflict', body: 'first')
-      stale_id = page.current_revision.id
-
-      described_class.content!(
-          page:,
-          body: 'second',
-          created_user: user,
-          message: 'second',
-          base_revision_id: stale_id)
-
-      page.reload
-      before_body = page.body
-      before_revision_count = page.wiki_revisions.count
-      before_version_count = page.wiki_versions.count
-
-      expect {
-        described_class.content!(
-            page:,
-            body: 'third',
-            created_user: user,
-            message: 'stale',
-            base_revision_id: stale_id)
-      }
-          .to raise_error(Wiki::Commit::Conflict)
-
-      page.reload
-      expect(page.body).to eq(before_body)
-      expect(page.wiki_revisions.count).to eq(before_revision_count)
-      expect(page.wiki_versions.count).to eq(before_version_count)
-    end
-
-    it 'deduplicates duplicated missing wiki lines' do
-      page = create_page(title: 'commit_integrity_dedup', body: 'before')
-      duplicated = 'commit_integrity_duplicate_line'
-
-      described_class.content!(
-          page:,
-          body: "#{ duplicated }\n#{ duplicated }",
-          created_user: user,
-          message: 'dedup',
-          base_revision_id: page.current_revision.id)
-
-      revision = page.reload.current_revision
-
-      expect(WikiLine.where(body: duplicated).count).to eq(1)
-      expect(revision.wiki_revision_lines.count).to eq(2)
-      expect(revision.wiki_revision_lines.pluck(:wiki_line_id).uniq.size).to eq(1)
-    end
-  end
-
-  describe '.redirect!' do
-    it 'raises because redirect revisions are deprecated' do
-      page = create_page(title: 'commit_integrity_redirect_source', body: 'source')
-      target = create_page(title: 'commit_integrity_redirect_target', body: 'target')
-
-      expect {
-        described_class.redirect!(
-            page:,
-            redirect_page: target,
-            created_user: user,
-            message: 'redirect',
-            base_revision_id: page.current_revision.id)
-      }
-          .to raise_error(RuntimeError, '廃止しました．')
-    end
-  end
-end
diff --git a/backend/spec/services/wiki/commit_spec.rb b/backend/spec/services/wiki/commit_spec.rb
deleted file mode 100644
index 6acd297..0000000
--- a/backend/spec/services/wiki/commit_spec.rb
+++ /dev/null
@@ -1,151 +0,0 @@
-require 'rails_helper'
-
-RSpec.describe Wiki::Commit do
-  include WikiRecords
-  let(:user) { create_member_user! }
-
-  def create_page(title: 'commit_spec_page', body: 'initial body')
-    tag_name = create(:tag, primary_name: title).tag_name('ja')
-
-    seed_wiki_page(
-        tag_name:,
-        body:,
-        created_by_user: user,
-        message: 'init')
-  end
-
-  describe '.content!' do
-    it 'stores normalised body in wiki_pages and wiki_versions' do
-      page = create_page(title: 'commit_normalised_page')
-
-      described_class.content!(
-        page:,
-        body: "a\r\nb\r\n\r\n",
-        created_user: user,
-        message: 'init'
-      )
-
-      page.reload
-      version = page.wiki_versions.order(:version_no).last
-
-      expect(page.body).to eq("a\nb")
-      expect(version.body).to eq("a\nb")
-      expect(page.current_revision.lines_count).to eq(2)
-    end
-
-    it 'deduplicates duplicated missing wiki lines before upsert' do
-      page = create_page(title: 'commit_duplicate_line_page')
-      duplicated = 'commit_duplicate_line'
-
-      described_class.content!(
-        page:,
-        body: "#{ duplicated }\n#{ duplicated }",
-        created_user: user,
-        message: 'init'
-      )
-
-      page.reload
-
-      expect(WikiLine.where(body: duplicated).count).to eq(1)
-      expect(page.current_revision.lines_count).to eq(2)
-      expect(page.current_revision.wiki_revision_lines.count).to eq(2)
-    end
-
-    it 'raises conflict when base_revision_id is stale' do
-      page = create_page(title: 'commit_conflict_page')
-
-      first = described_class.content!(
-        page:,
-        body: 'first',
-        created_user: user,
-        message: 'first'
-      )
-
-      described_class.content!(
-        page:,
-        body: 'second',
-        created_user: user,
-        message: 'second',
-        base_revision_id: first.id
-      )
-
-      expect {
-        described_class.content!(
-          page:,
-          body: 'third',
-          created_user: user,
-          message: 'third',
-          base_revision_id: first.id
-        )
-      }.to raise_error(Wiki::Commit::Conflict)
-    end
-
-    it 'does not record tag version when corresponding tag has no versions' do
-      tag_name = create(:tag_name, name: 'commit_linked_tag_without_versions')
-      tag = create(:tag, primary_tag_name: tag_name, category: :general)
-
-      page =
-          seed_wiki_page(
-              tag_name:,
-              body: 'before',
-              created_by_user: user,
-              message: 'init')
-
-      expect(tag.reload.tag_versions.count).to eq(0)
-
-      current_revision_id = page.current_revision.id
-
-      expect {
-        described_class.content!(
-            page:,
-            body: 'after',
-            created_user: user,
-            message: 'edit',
-            base_revision_id: current_revision_id)
-      }.to change(WikiVersion, :count).by(1)
-
-      expect(tag.reload.tag_versions.count).to eq(0)
-    end
-
-    it 'does not record tag version when corresponding tag has no versions' do
-      tag_name = create(:tag_name, name: 'commit_linked_tag_without_versions')
-      tag = create(:tag, primary_tag_name: tag_name, category: :general)
-
-      page =
-          seed_wiki_page(
-              tag_name:,
-              body: 'before',
-              created_by_user: user,
-              message: 'init')
-
-      current_revision_id = page.current_revision.id
-
-      expect {
-        described_class.content!(
-            page:,
-            body: 'after',
-            created_user: user,
-            message: 'edit',
-            base_revision_id: current_revision_id)
-      }.to change(WikiVersion, :count).by(1)
-
-      expect(tag.reload.tag_versions.count).to eq(0)
-    end
-  end
-
-  describe '.redirect!' do
-    it 'raises because redirect revisions are deprecated' do
-      page = create_page(title: 'commit_redirect_source')
-      target = create_page(title: 'commit_redirect_target')
-
-      expect {
-        described_class.redirect!(
-          page:,
-          redirect_page: target,
-          created_user: user,
-          message: 'redirect'
-        )
-      }.to raise_error(RuntimeError, '廃止しました．')
-    end
-  end
-end
diff --git a/backend/spec/services/wiki_version_recorder_spec.rb b/backend/spec/services/wiki_version_recorder_spec.rb
deleted file mode 100644
index 6c1457c..0000000
--- a/backend/spec/services/wiki_version_recorder_spec.rb
+++ /dev/null
@@ -1,100 +0,0 @@
-require 'rails_helper'
-
-RSpec.describe WikiVersionRecorder do
-  include WikiRecords
-  let(:user) { create_member_user! }
-
-  def create_page title:, body: 'body'
-    seed_wiki_page(
-        tag_name: create(:tag_name, name: title),
-        body:,
-        created_by_user: user,
-        message: 'init')
-  end
-
-  describe '.record!' do
-    it 'records title, body, reason, user, and version number' do
-      page = create_page(title: 'wiki_version_recorder_basic', body: 'body')
-
-      expect {
-        described_class.record!(
-            page:,
-            event_type: :update,
-            reason: 'manual reason',
-            created_by_user: user)
-      }
-          .to change { page.reload.wiki_versions.count }.by(1)
-
-      version = page.wiki_versions.order(:version_no).last
-
-      expect(version).to have_attributes(
-        version_no: 2,
-        event_type: 'update',
-        title: 'wiki_version_recorder_basic',
-        body: 'body',
-        reason: 'manual reason',
-        created_by_user_id: user.id
-      )
-    end
-
-    it 'does not create duplicated update version for identical snapshot' do
-      page = create_page(title: 'wiki_version_recorder_duplicate', body: 'body')
-
-      described_class.record!(
-          page:,
-          event_type: :update,
-          reason: nil,
-          created_by_user: user)
-
-      before_count = page.reload.wiki_versions.count
-
-      described_class.record!(
-          page:,
-          event_type: :update,
-          reason: nil,
-          created_by_user: user)
-
-      expect(page.reload.wiki_versions.count).to eq(before_count)
-    end
-
-    it 'creates update version when title changes' do
-      page = create_page(title: 'wiki_version_recorder_title_before', body: 'body')
-      page.tag_name.update!(name: 'wiki_version_recorder_title_after')
-
-      expect {
-        described_class.record!(
-            page:,
-            event_type: :update,
-            reason: 'rename',
-            created_by_user: user)
-      }
-          .to change { page.reload.wiki_versions.count }.by(1)
-
-      version = page.wiki_versions.order(:version_no).last
-
-      expect(version.title).to eq('wiki_version_recorder_title_after')
-      expect(version.body).to eq('body')
-      expect(version.reason).to eq('rename')
-    end
-
-    it 'creates update version when body changes' do
-      page = create_page(title: 'wiki_version_recorder_body', body: 'before')
-      page.update!(body: 'after')
-
-      expect {
-        described_class.record!(
-            page:,
-            event_type: :update,
-            reason: 'body',
-            created_by_user: user)
-      }
-          .to change { page.reload.wiki_versions.count }.by(1)
-
-      version = page.wiki_versions.order(:version_no).last
-
-      expect(version.title).to eq('wiki_version_recorder_body')
-      expect(version.body).to eq('after')
-      expect(version.reason).to eq('body')
-    end
-  end
-end
diff --git a/backend/spec/support/tag_group_records.rb b/backend/spec/support/tag_group_records.rb
index ed3a929..9d370c7 100644
--- a/backend/spec/support/tag_group_records.rb
+++ b/backend/spec/support/tag_group_records.rb
@@ -7,8 +7,7 @@ module TagGroupRecords
       'tag_groups', 'tag_group_tags', 'tag_group_groups',
       'tag_group_placements', 'tag_group_versions'].freeze
   WRITE_TABLES = GROUP_TABLES + [
-      'wiki_pages', 'wiki_revisions', 'wiki_versions', 'wiki_lines',
-      'wiki_revision_lines', 'tag_names', 'tag_description_versions',
+      'tag_names', 'tag_description_versions',
       'tag_descriptions']
 
   def group_connection = ApplicationRecord.connection
@@ -34,13 +33,11 @@ module TagGroupRecords
     WRITE_TABLES.to_h { |table| [table, group_rows(table)] }
   end
 
-  def expect_noop_group_update group_id:, page:
+  def expect_noop_group_update group_id:
     before_state = group_state
     group = TagGroup.find(group_id)
     version_id = TagGroupVersion.find_by!(
         tag_group_id: group_id, version_no: group.version_no).id
-    revision_id = page.reload.current_revision.id
-    wiki_version_id = page.wiki_versions.order(version_no: :desc).first.id
     writes = []
     tables = Regexp.union(WRITE_TABLES)
     subscriber = lambda do |*args|
@@ -59,8 +56,6 @@ module TagGroupRecords
       end
       expect(TagGroupVersion.find_by!(
           tag_group_id: group_id, version_no: group.reload.version_no).id).to eq(version_id)
-      expect(page.reload.current_revision.id).to eq(revision_id)
-      expect(page.wiki_versions.order(version_no: :desc).first.id).to eq(wiki_version_id)
       expect(writes).to be_empty
     end
   end
@@ -99,25 +94,13 @@ module TagGroupRecords
     tag.reload
   end
 
-  def legacy_group name, body
-    # Historical fixtures preserve blank lines independently of today's writer.
-    body = body.sub(/\n+\z/, '')
-    page = WikiPage.create!(
-        tag_name: create(:tag_name, name: "タググループ:#{ name }"),
-        body:, created_user: user, updated_user: user)
-    WikiVersionRecorder.record!(page:, event_type: :create, created_by_user: user)
-    lines = body.split("\n")
-    shas = lines.map { Digest::SHA256.hexdigest(_1) }
-    revision = WikiRevision.create!(
-        wiki_page: page, kind: :content, created_user: user, lines_count: lines.size,
-        tree_sha256: Digest::SHA256.hexdigest(shas.join(',')))
-    lines.each_with_index do |line, position|
-      sha = shas.fetch(position)
-      line_id = WikiLine.find_by(sha256: sha)&.id || insert_group_row('wiki_lines', {
-          body: line, sha256: sha, created_at: Time.current, updated_at: Time.current })
-      WikiRevisionLine.create!(wiki_revision: revision, wiki_line_id: line_id, position:)
-    end
-    page
+  def create_markdown_group name, body
+    parsed = TagGroupMarkdownParser.parse(body:)
+    TagGroupOperation.create!(name:, actor: user, **parsed.slice(:description, :members, :placements))
+  end
+
+  def group_markdown group
+    TagGroupMarkdownRenderer.render(TagGroupRepr.one(group.reload))
   end
 
   def seed_group name:, placements: [], members: [], description: nil, id: nil
@@ -176,16 +159,6 @@ module TagGroupRecords
     "/wiki/title/#{ CGI.escapeURIComponent("タググループ:#{ name }") }"
   end
 
-  def migrate_groups
-    require_relative '../../db/migrate/20261008010000_migrate_tag_groups_from_wiki_pages'
-    migration = MigrateTagGroupsFromWikiPages.new
-    @group_migration_messages = []
-    allow(migration).to receive(:say) do |message, *_args|
-      @group_migration_messages << message if message.start_with?('Wiki #', 'Tag Group')
-    end
-    migration.suppress_messages { migration.up }
-  end
-
   def expect_group_snapshot group_id, number:, placements:, members:, description: nil
     current = group_rows('tag_groups', id: group_id).sole
     version = group_version(group_id, number)
diff --git a/backend/spec/support/wiki_records.rb b/backend/spec/support/wiki_records.rb
index f321aba..4dbcfb1 100644
--- a/backend/spec/support/wiki_records.rb
+++ b/backend/spec/support/wiki_records.rb
@@ -1,20 +1,14 @@
-# Historical records must remain seedable after application creation is frozen.
 module WikiRecords
-  def seed_wiki_page(tag_name:, body:, created_by_user:, message: nil)
-    page = WikiPage.create!(tag_name:, body:,
-                            created_user: created_by_user, updated_user: created_by_user)
-    revision = Wiki::Commit.legacy_content!(
-        page:, body:, created_user: created_by_user, message:)
-    if tag_name.tag && tag_name.language_code == 'ja'
-      TagDescription.create!(
-          id: page.id, tag: tag_name.tag, language_code: 'ja', body: page.reload.body,
-          version_no: 1, created_by_user_id: created_by_user.id,
-          updated_by_user_id: created_by_user.id)
-      TagDescriptionVersion.create!(
-          id: revision.id, tag_id: tag_name.tag_id, language_code: 'ja',
-          version_no: 1, event_type: 'create', body: page.body,
-          created_by_user_id: created_by_user.id, created_at: revision.created_at)
-    end
-    page
+  def seed_description(tag_name:, body:, created_by_user:, message: nil)
+    TagDescriptionOperation.create!(tag: tag_name.tag, body:, created_by_user:, message:)
+  end
+
+  def description_versions(description)
+    TagDescriptionVersion.where(
+        tag_id: description.tag_id, language_code: description.language_code)
+  end
+
+  def current_description_version(description)
+    description_versions(description).find_by!(version_no: description.reload.version_no)
   end
 end