#424

backend/spec/db/tag_description_migration_spec.rb

@@ -5,11 +5,11 @@ 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_content!(
+    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.content!(
+      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)

backend/spec/models/shared_tag_ids_spec.rb

@@ -2,6 +2,7 @@ require 'rails_helper'
 
 RSpec.describe 'Shared Tag and ExternalTag IDs', type: :model do
   include TagGroupRecords
+  let(:user) { create_member_user! }
 
   def create_resource resource
     if resource == :tag
@@ -25,6 +26,12 @@ RSpec.describe 'Shared Tag and ExternalTag IDs', type: :model do
       expect(create_resource(resource).id).to eq(21)
     end
 
+    it "uses the current maximum after deleting earlier #{ resource } records" do
+      create(:tag, id: 100).destroy!
+      create(:external_tag, id: 200).destroy!
+      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) }

backend/spec/requests/tag_description_wiki_spec.rb

@@ -10,8 +10,8 @@ RSpec.describe 'Tag description Wiki compatibility', type: :request do
   end
   let!(:revisions) do
     first = page.current_revision
-    second = Wiki::Commit.content!(page:, body: 'old-second', created_user: user)
-    third = Wiki::Commit.content!(page:, body: 'old-third', created_user: user)
+    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) }

backend/spec/requests/tag_description_wiki_write_spec.rb

@@ -32,20 +32,38 @@ RSpec.describe 'Tag description Wiki dual writes', type: :request do
            headers: headers
     end
 
-    it 'creates a description without implicitly creating Wiki records' do
+    it 'creates a description with matching Wiki content and histories' do
       expect { create_description }
-          .to change(WikiPage, :count).by(0)
-          .and change(WikiRevision, :count).by(0)
-          .and change(WikiVersion, :count).by(0)
+          .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'
@@ -70,7 +88,7 @@ RSpec.describe 'Tag description Wiki dual writes', type: :request do
       end
     end
 
-    [TagDescription, TagDescriptionVersion].each do |model|
+    [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
@@ -81,6 +99,28 @@ RSpec.describe 'Tag description Wiki dual writes', type: :request do
     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
+    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)
+  end
+
   describe 'PUT /wiki/:id' do
     let!(:page) do
       tag
@@ -144,10 +184,10 @@ RSpec.describe 'Tag description Wiki dual writes', type: :request do
       page_state = page.attributes
       description_state = description.attributes
 
-      update_description(body: 'before', title: 'Help:description_renamed')
+      update_description(body: 'before', title: 'description_renamed')
 
       expect(response).to have_http_status(:ok)
-      expect(tag_name.reload.name).to eq('Help:description_renamed')
+      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)

backend/spec/requests/tag_group_wiki_write_spec.rb

@@ -33,11 +33,11 @@ RSpec.describe 'Tag group Wiki facade writes', type: :request do
     end
   end
 
-  it 'creates the group and first snapshot without new Wiki records' do
+  it 'creates the group, snapshot and matching compatibility histories' do
     expect { create_group }
-        .to change(WikiPage, :count).by(0)
-        .and change(WikiRevision, :count).by(0)
-        .and change(WikiVersion, :count).by(0)
+        .to change(WikiPage, :count).by(1)
+        .and change(WikiRevision, :count).by(1)
+        .and change(WikiVersion, :count).by(1)
     expect(response).to have_http_status(:created)
     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')
@@ -45,6 +45,10 @@ 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)
   end
 
   it 'keeps repeated placements but only one membership and one snapshot member' do
@@ -292,7 +296,7 @@ RSpec.describe 'Tag group Wiki facade writes', type: :request do
       end
 
       tables = TagGroupRecords::GROUP_TABLES
-      tables += ['wiki_pages', 'wiki_revisions', 'wiki_versions'] if operation == :update
+      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) }

backend/spec/requests/tag_group_write_integrity_spec.rb

@@ -71,17 +71,16 @@ RSpec.describe 'Tag group write integrity', type: :request do
       expect(page.body).to eq('- 伊地知ニジカ')
     end
 
-    it 'updates Help with a colliding group ID without altering the group' do
+    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)
 
-      put_wiki(id, title: 'Help:改名', body: 'Help after')
+      expect_no_writes { put_wiki(id, title: 'Help:改名', body: 'Help after') }
 
-      expect(response).to have_http_status(:ok)
-      expect(page.reload.body).to eq('Help after')
-      expect(page.title).to eq('Help:改名')
+      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
@@ -99,7 +98,8 @@ RSpec.describe 'Tag group write integrity', type: :request do
     it 'keeps a description update separate from a colliding group' do
       page = Wiki::Commit.create_content!(
           tag_name: tag.tag_name('ja'), body: 'description before', created_by_user: user)
-      id = seed_group(name: '更新', id: page.id, members:, placements:)
+      description = TagDescription.find_by!(tag_id: tag.id)
+      id = seed_group(name: '更新', id: description.id, members:, placements:)
       group_before = TagGroup.find(id).attributes
 
       put_wiki(id, title: '洗澡鹿', body: 'description after')
@@ -116,18 +116,19 @@ RSpec.describe 'Tag group write integrity', type: :request do
       description = TagDescription.create!(
           id:, tag:, language_code: 'ja', version_no: 1, body: 'description')
 
-      put_wiki(id, title: 'Help:既存', body: 'Help after')
+      expect_no_writes { put_wiki(id, title: 'Help:既存', body: 'Help after') }
 
-      expect(response).to have_http_status(:ok)
-      expect(page.reload.body).to eq('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)
-      expect_no_writes { put_wiki(id, title: '洗澡鹿', body: 'description after') }
+      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 after')
-      expect(description.reload.body).to eq('description')
+      expect(page.reload.body).to eq('Help before')
+      expect(description.reload.body).to eq('description after')
     end
   end
 
@@ -139,9 +140,9 @@ RSpec.describe 'Tag group write integrity', type: :request do
 
       expect do
         put "/tag_groups/#{ id }", params: native_payload(name: '改名'), headers:, as: :json
-      end.to change(WikiPage, :count).by(0)
-          .and change(WikiRevision, :count).by(0)
-          .and change(WikiVersion, :count).by(0)
+      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')

backend/spec/requests/tag_groups_spec.rb

@@ -391,18 +391,18 @@ RSpec.describe 'Tag group native API', type: :request do
         end
       end
 
-      it 'creates native state without adding compatibility Wiki records' do
+      it 'creates native state and its compatibility histories' do
         expect { native_write(:create) }
-            .to change(WikiPage, :count).by(0)
-            .and change(WikiRevision, :count).by(0)
-            .and change(WikiVersion, :count).by(0)
+            .to change(WikiPage, :count).by(1)
+            .and change(WikiRevision, :count).by(1)
+            .and change(WikiVersion, :count).by(1)
         expect(response).to have_http_status(:created)
         expect_group_snapshot(
             json.fetch('id'), number: 1, members: snapshot_members,
             placements:, description: '全体の説明')
       end
 
-      [:update].each do |operation|
+      [:create, :update].each do |operation|
         it "synchronises Wiki current state and histories on native #{ operation }" do
           native_write(operation)
           expect(response).to have_http_status(operation == :create ? :created : :ok)

backend/spec/requests/wiki_conflict_spec.rb

@@ -11,7 +11,7 @@ RSpec.describe 'Wiki conflict handling', type: :request do
   it 'returns 409 when base_revision_id is stale' do
     page =
         seed_wiki_page(
-            tag_name: create(:tag_name, name: 'wiki_conflict_request'),
+            tag_name: create(:tag, primary_name: 'wiki_conflict_request').tag_name('ja'),
             body: 'first',
             created_by_user: user,
             message: 'init')
@@ -26,12 +26,10 @@ RSpec.describe 'Wiki conflict handling', type: :request do
         base_revision_id: stale_id)
 
     put "/wiki/#{ page.id }",
-        params: {
-          title: 'wiki_conflict_request',
-          body: 'third',
-          message: 'stale',
-          base_revision_id: stale_id,
-        },
+        params: { title: 'wiki_conflict_request',
+                  body: 'third',
+                  message: 'stale',
+                  base_revision_id: stale_id },
         headers: auth_headers(user)
 
     expect(response).to have_http_status(:conflict)

backend/spec/requests/wiki_creation_freeze_spec.rb

@@ -7,17 +7,21 @@ RSpec.describe 'Wiki creation freeze', type: :request do
   let!(:user) { create_member_user! }
   let(:headers) { { 'X-Transfer-Code' => user.inheritance_code } }
 
-  it 'updates an independent group without implicitly creating a legacy page' do
+  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(0)
-        .and change(WikiRevision, :count).by(0)
-        .and change(WikiVersion, :count).by(0)
+    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

backend/spec/requests/wiki_history_integrity_spec.rb

@@ -11,7 +11,7 @@ RSpec.describe 'Wiki history integrity', type: :request do
 
   def create_wiki_page title:, body: 'body', message: 'init', user: self.user
     seed_wiki_page(
-        tag_name: create(:tag_name, name: title),
+        tag_name: create(:tag, primary_name: title).tag_name('ja'),
         body:,
         created_by_user: user,
         message:)

backend/spec/requests/wiki_index_order_spec.rb

@@ -0,0 +1,42 @@
+require 'rails_helper'
+
+RSpec.describe 'Wiki resource ordering', type: :request do
+  include TagGroupRecords
+  let(:user) { create_member_user! }
+
+  it 'selects the latest twenty across both resources before applying the global limit' do
+    start = Time.utc(2026, 1, 1)
+    descriptions = 24.times.map do |index|
+      tag = create(:tag, primary_name: "rank_#{ index }")
+      TagDescription.create!(tag:, language_code: 'ja', body: 'current', version_no: 1,
+                             updated_at: start + index.hours)
+    end
+    groups = [24, 25].map do |hour|
+      group = TagGroup.find(seed_group(name: "rank_group_#{ hour }"))
+      group.update_columns(updated_at: start + hour.hours)
+      group
+    end
+
+    get '/wiki', params: { title: 'rank' }
+
+    expect(response).to have_http_status(:ok)
+    expected = groups.reverse.map { ['tag_group', _1.id] } +
+        descriptions.last(18).reverse.map { ['tag_description', _1.id] }
+    expect(json.map { [_1.fetch('resource_type'), _1.fetch('id')] }).to eq(expected)
+  end
+
+  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',
+                           version_no: 1, updated_at: time)
+    group = TagGroup.find(seed_group(name: 'tied', id: 51))
+    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]])
+    end
+  end
+end

backend/spec/requests/wiki_spec.rb

@@ -129,7 +129,7 @@ RSpec.describe 'Wiki API', type: :request do
       { 'X-Transfer-Code' => user.inheritance_code }
     end
 
-    let!(:test_tag_name) { create(:tag_name, name: 'TestPage') }
+    let!(:test_tag_name) { create(:tag, primary_name: 'TestPage').tag_name('ja') }
 
     let!(:page) do
       seed_wiki_page(

backend/spec/requests/wiki_unmigrated_contract_spec.rb

@@ -9,29 +9,29 @@ RSpec.describe 'Unmigrated Wiki compatibility', type: :request do
   end
   let!(:first_revision) { page.current_revision }
   let!(:last_revision) do
-    Wiki::Commit.content!(page:, body: 'after', created_user: user,
-                          message: 'legacy edit', base_revision_id: first_revision.id)
+    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 'keeps a Tag-linked legacy page in the legacy domain when its title changes' do
+  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(1)
-        .and change(WikiVersion, :count).by(1)
+    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(:ok)
-    expect(page.reload).to have_attributes(body: 'changed legacy body')
-    expect(page.title).to eq('legacy_tag_renamed')
-    expect(page.current_revision).to have_attributes(message: 'legacy rename')
+    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
 
   include TagGroupRecords

backend/spec/services/shared_resource_id_allocator_spec.rb

@@ -0,0 +1,65 @@
+require 'rails_helper'
+
+RSpec.describe SharedResourceIdAllocator do
+  let(:record) { build(:external_tag) }
+  let(:connection) { double('connection') }
+  let(:transaction) { double('transaction', open?: true) }
+  let(:callbacks) { { } }
+  let(:sql) { [] }
+
+  before 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_table_name) { "`#{ _1 }`" }
+    allow(connection).to receive(:select_value) do |statement|
+      sql << statement
+      if statement.include?('GET_LOCK') || statement.include?('RELEASE_LOCK')
+        1
+      elsif statement.include?('`tags`')
+        8
+      else
+        3
+      end
+    end
+    allow(ExternalTag).to receive(:connection).and_return(connection)
+    allow(ExternalTag).to receive(:current_transaction).and_return(transaction)
+    allow(ExternalTag).to receive(:uncached).and_yield
+    [:after_commit, :after_rollback].each do |event|
+      allow(transaction).to receive(event) { |&callback| callbacks[event] = callback }
+    end
+  end
+
+  [:after_commit, :after_rollback].each do |event|
+    it "holds the shared lock until #{ event }" do
+      described_class.assign!(record)
+      expect(record.id).to eq(9)
+      expect(sql.grep(/RELEASE_LOCK/)).to be_empty
+      expect(sql.grep(/FOR UPDATE/).size).to eq(2)
+      callbacks.fetch(event).call
+      expect(sql.grep(/RELEASE_LOCK/).size).to eq(1)
+    end
+  end
+
+  it 'does not silently proceed after an acquisition timeout' do
+    allow(connection).to receive(:select_value).and_return(0)
+    expect { described_class.assign!(record) }.to raise_error(ActiveRecord::LockWaitTimeout)
+    expect(record.id).to be_nil
+    expect(callbacks).to be_empty
+  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')
+    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
+    described_class.assign!(record)
+    expect(record.id).to eq(5)
+    expect(sql.grep(/FOR UPDATE/)).to be_empty
+    callbacks.fetch(:after_commit).call
+  end
+end

backend/spec/services/wiki/commit_integrity_spec.rb

@@ -7,29 +7,37 @@ RSpec.describe Wiki::Commit do
 
   def create_page title:, body: 'initial body'
     seed_wiki_page(
-        tag_name: create(:tag_name, name: title),
+        tag_name: create(:tag, primary_name: title).tag_name('ja'),
         body:,
         created_by_user: user,
         message: 'init')
   end
 
   describe '.create_content!' do
-    [:create_content!, :create_legacy_content!].each do |operation|
-      it "freezes #{ operation } without adding page or history" do
-        name = create(:tag_name, name: 'Help:frozen_service')
-        counts = [WikiPage.count, WikiRevision.count, WikiVersion.count]
-        begin
-          described_class.public_send(operation, tag_name: name, body: 'initial',
-                                      created_by_user: user)
-        rescue ActiveRecord::RecordInvalid
-          # A validation rejection is allowed; persistence is not.
-        end
-        expect([WikiPage.count, WikiRevision.count, WikiVersion.count]).to eq(counts)
-      end
+    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_name, name: 'commit_integrity_blank')
+      tag_name = create(:tag, primary_name: 'commit_integrity_blank').tag_name('ja')
 
       expect {
         described_class.create_content!(
@@ -45,6 +53,17 @@ RSpec.describe Wiki::Commit do
   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

backend/spec/services/wiki/commit_spec.rb

@@ -5,7 +5,7 @@ RSpec.describe Wiki::Commit do
   let(:user) { create_member_user! }
 
   def create_page(title: 'commit_spec_page', body: 'initial body')
-    tag_name = create(:tag_name, name: title)
+    tag_name = create(:tag, primary_name: title).tag_name('ja')
 
     seed_wiki_page(
         tag_name:,