diff --git a/backend/app/controllers/tags_controller.rb b/backend/app/controllers/tags_controller.rb
index 7fdcc22..8613bd0 100644
--- a/backend/app/controllers/tags_controller.rb
+++ b/backend/app/controllers/tags_controller.rb
@@ -302,10 +302,9 @@ class TagsController < ApplicationController
       NicoTagVersionRecorder.record!(tag:, event_type:, created_by_user:)
     else
       TagVersionRecorder.record!(tag:, event_type:, created_by_user:)
-      if tag.has_wiki
-        WikiVersionRecorder.record!(page: tag.tag_name.wiki_page,
-                                    event_type: :update,
-                                    created_by_user:)
+      wiki_page = tag.tag_name.wiki_page
+      if wiki_page&.wiki_versions&.exists?
+        WikiVersionRecorder.record!(page: wiki_page, event_type: :update, created_by_user:)
       end
     end
   end
diff --git a/backend/app/models/wiki_page.rb b/backend/app/models/wiki_page.rb
index 83a7f1b..b725706 100644
--- a/backend/app/models/wiki_page.rb
+++ b/backend/app/models/wiki_page.rb
@@ -17,6 +17,7 @@ class WikiPage < ApplicationRecord
 
   belongs_to :tag_name
   validates :tag_name, presence: true
+  validates :body, presence: true
 
   def title = tag_name.name
 
@@ -26,11 +27,6 @@ class WikiPage < ApplicationRecord
 
   def current_revision = wiki_revisions.order(id: :desc).first
 
-  def body
-    rev = current_revision
-    rev.body if rev&.content?
-  end
-
   def resolve_redirect limit: 10
     page = self
     visited = Set.new
diff --git a/backend/app/services/wiki/commit.rb b/backend/app/services/wiki/commit.rb
index f3e325d..4f22fc3 100644
--- a/backend/app/services/wiki/commit.rb
+++ b/backend/app/services/wiki/commit.rb
@@ -7,6 +7,31 @@ module Wiki
       ;
     end
 
+    def self.create_content! tag_name:, body:, created_by_user:, message: nil
+      normalised = normalise_body(body)
+
+      page = WikiPage.new(tag_name:,
+                          body: normalised,
+                          created_user: created_by_user,
+                          updated_user: created_by_user)
+
+      if normalised.blank?
+        page.errors.add(:body, :blank)
+        raise ActiveRecord::RecordInvalid, page
+      end
+
+      ActiveRecord::Base.transaction do
+        page.save!
+
+        new(page:, created_user: created_by_user).content!(
+            body: normalised,
+            message:,
+            base_revision_id: nil)
+
+        page
+      end
+    end
+
     def self.content! page:, body:, created_user:, message: nil, base_revision_id: nil
       new(page:, created_user:).content!(body:, message:, base_revision_id:)
     end
@@ -21,7 +46,12 @@ module Wiki
     end
 
     def content! body:, message:, base_revision_id:
-      normalised = normalise_body(body).gsub(/\n+$/, '')
+      normalised = self.class.normalise_body(body)
+      if normalised.blank?
+        @page.errors.add(:body, :blank)
+        raise ActiveRecord::RecordInvalid, @page
+      end
+
       lines = split_lines(normalised)
 
       line_shas = lines.map { |line| Digest::SHA256.hexdigest(line) }
@@ -45,11 +75,12 @@ module Wiki
         @page.update!(body: normalised)
 
         WikiVersionRecorder.record!(
-            page: { title: @page.title, body: normalised },
+            page: @page,
             event_type: @page.wiki_versions.exists? ? :update : :create,
+            reason: message,
             created_by_user: @created_user)
         tag = @page.tag_name.tag
-        if tag
+        if tag&.tag_versions&.exists?
           TagVersionRecorder.record!(tag:, event_type: :update, created_by_user: @created_user)
         end
 
@@ -74,14 +105,15 @@ module Wiki
 
     def redirect!(redirect_page:, message:, base_revision_id:) = raise '廃止しました．'
 
-    private
-
-    def normalise_body body
+    def self.normalise_body body
       s = body.to_s
       s.gsub!(/\r\n?/, "\n")
       s.encode('UTF-8', invalid: :replace, undef: :replace, replace: '🖕')
+      s.gsub(/\n+$/, '')
     end
 
+    private
+
     def split_lines(body) = body.split("\n")
 
     def upsert_lines! lines, line_shas
diff --git a/backend/app/services/wiki_version_recorder.rb b/backend/app/services/wiki_version_recorder.rb
index a9bebe4..f6aa09e 100644
--- a/backend/app/services/wiki_version_recorder.rb
+++ b/backend/app/services/wiki_version_recorder.rb
@@ -1,9 +1,10 @@
 class WikiVersionRecorder < VersionRecorder
-  def self.record! page:, event_type:, created_by_user:
+  def self.record! page:, event_type:, reason: nil, created_by_user:
     new(page:, event_type:, created_by_user:).record!
   end
 
-  def initialize page:, event_type:, created_by_user:
+  def initialize page:, event_type:, reason: nil, created_by_user:
+    @reason = reason
     super(record: page, event_type:, created_by_user:)
   end
 
@@ -13,5 +14,8 @@ class WikiVersionRecorder < VersionRecorder
   def version_association = :wiki_versions
   def record_key = :wiki_page
 
-  def snapshot_attributes = { title: @record.title, body: @record.body }
+  def snapshot_attributes = {
+      title: @record.title,
+      body: @record.body,
+      reason: @reason }
 end
diff --git a/backend/spec/factories/wiki_pages.rb b/backend/spec/factories/wiki_pages.rb
index b4f1496..7f5f41a 100644
--- a/backend/spec/factories/wiki_pages.rb
+++ b/backend/spec/factories/wiki_pages.rb
@@ -3,5 +3,7 @@ FactoryBot.define do
     title { "TestPage" }
     association :created_user, factory: :user
     association :updated_user, factory: :user
+
+    body { ' ' }
   end
 end
diff --git a/backend/spec/models/tag_spec.rb b/backend/spec/models/tag_spec.rb
index 1dee732..1a1714b 100644
--- a/backend/spec/models/tag_spec.rb
+++ b/backend/spec/models/tag_spec.rb
@@ -107,11 +107,13 @@ RSpec.describe Tag, type: :model do
     context 'when the source tag_name has a wiki_page' do
       let!(:source_post_tag) { PostTag.create!(post: post_record, tag: source_tag) }
       let!(:wiki_page) do
-        WikiPage.create!(
-          tag_name: source_tag_name,
-          created_user: create_admin_user!,
-          updated_user: create_admin_user!
-        )
+        admin = create_admin_user!
+
+        Wiki::Commit.create_content!(
+            tag_name: source_tag_name,
+            body: 'source wiki body',
+            created_by_user: admin,
+            message: 'init')
       end
 
       it 'rolls back the transaction' do
diff --git a/backend/spec/requests/tag_versions_spec.rb b/backend/spec/requests/tag_versions_spec.rb
index f1d92e7..0175704 100644
--- a/backend/spec/requests/tag_versions_spec.rb
+++ b/backend/spec/requests/tag_versions_spec.rb
@@ -214,5 +214,34 @@ RSpec.describe 'TagVersions API', type: :request do
       expect(versions.size).to eq(1)
       expect(versions.first['version_no']).to eq(2)
     end
+
+    it 'includes tag versions created by wiki updates' do
+      wiki_tag_name = TagName.create!(name: 'tag_versions_from_wiki')
+      wiki_tag = Tag.create!(tag_name: wiki_tag_name, category: :general)
+
+      wiki_page =
+          Wiki::Commit.create_content!(
+              tag_name: wiki_tag_name,
+              body: 'before',
+              created_by_user: member,
+              message: 'init')
+
+      Wiki::Commit.content!(
+          page: wiki_page,
+          body: 'after',
+          created_user: member,
+          message: 'edit',
+          base_revision_id: wiki_page.current_revision.id)
+
+      get '/tags/versions', params: { id: wiki_tag.id }
+
+      expect(response).to have_http_status(:ok)
+
+      versions = json.fetch('versions')
+
+      expect(json.fetch('count')).to eq(2)
+      expect(versions.map { |v| v['event_type'] }).to eq(['update', 'create'])
+      expect(versions.map { |v| v['name']['current'] }.uniq).to eq(['tag_versions_from_wiki'])
+    end
   end
 end
diff --git a/backend/spec/requests/tags_spec.rb b/backend/spec/requests/tags_spec.rb
index d3bc594..e186582 100644
--- a/backend/spec/requests/tags_spec.rb
+++ b/backend/spec/requests/tags_spec.rb
@@ -876,6 +876,105 @@ RSpec.describe 'Tags API', type: :request do
         expect(system_tag.reload.name).to eq(old_name)
         expect(system_tag.category).to eq(old_category)
       end
+
+      it 'wiki を持つ tag を更新すると wiki version も作成する' do
+        wiki_page =
+            Wiki::Commit.create_content!(
+                tag_name: tag.tag_name,
+                body: 'wiki body before',
+                created_by_user: member_user,
+                message: 'init')
+
+        Wiki::Commit.content!(
+          page: wiki_page,
+          body: 'wiki body before',
+          created_user: member_user,
+          message: 'init'
+        )
+
+        expect {
+          put "/tags/#{ tag.id }", params: {
+            name: 'put_wiki_version_tag',
+            category: 'meme',
+            aliases: 'unko',
+            parent_tags: '',
+          }
+        }
+            .to change(TagVersion, :count).by(2)
+            .and change(WikiVersion, :count).by(1)
+
+        expect(response).to have_http_status(:ok)
+
+        version = wiki_page.reload.wiki_versions.order(:version_no).last
+
+        expect(version).to have_attributes(
+          event_type: 'update',
+          title: 'put_wiki_version_tag',
+          body: 'wiki body before',
+          created_by_user_id: member_user.id
+        )
+      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
+        pending '#329 で対応予定'
+
+        old_owner = Tag.create!(
+          tag_name: TagName.create!(name: 'put_alias_old_owner'),
+          category: :general
+        )
+        stolen_alias = TagName.create!(
+          name: 'put_stolen_alias',
+          canonical: old_owner.tag_name
+        )
+
+        expect(old_owner.tag_name.aliases.map(&:name)).to include('put_stolen_alias')
+
+        expect {
+          put "/tags/#{ tag.id }", params: {
+            name: 'spec_tag',
+            category: 'general',
+            aliases: 'unko put_stolen_alias',
+            parent_tags: '',
+          }
+        }
+            .to change { tag.reload.tag_versions.count }.by(2)
+            .and change { old_owner.reload.tag_versions.count }.by(2)
+
+        expect(response).to have_http_status(:ok)
+
+        expect(stolen_alias.reload.canonical).to eq(tag.tag_name)
+        expect(old_owner.reload.tag_name.aliases.map(&:name)).not_to include('put_stolen_alias')
+
+        old_owner_versions = old_owner.tag_versions.order(:version_no)
+
+        expect(old_owner_versions.first.event_type).to eq('create')
+        expect(old_owner_versions.first.aliases.split).to include('put_stolen_alias')
+
+        expect(old_owner_versions.second.event_type).to eq('update')
+        expect(old_owner_versions.second.aliases.split).not_to include('put_stolen_alias')
+      end
+
+      it 'parent_tags に指定すると循環する tag は 422 にする' do
+        pending '#332 で対応予定'
+
+        child = Tag.create!(
+          tag_name: TagName.create!(name: 'put_cycle_child'),
+          category: :general
+        )
+
+        TagImplication.create!(tag: child, parent_tag: tag)
+
+        put "/tags/#{ tag.id }", params: {
+          name: 'spec_tag',
+          category: 'general',
+          aliases: 'unko',
+          parent_tags: child.name,
+        }
+
+        expect(response).to have_http_status(:unprocessable_entity)
+
+        expect(TagImplication.where(tag:, parent_tag: child)).not_to exist
+      end
     end
   end
 end
diff --git a/backend/spec/requests/wiki_spec.rb b/backend/spec/requests/wiki_spec.rb
index 4541501..020e412 100644
--- a/backend/spec/requests/wiki_spec.rb
+++ b/backend/spec/requests/wiki_spec.rb
@@ -8,7 +8,12 @@ RSpec.describe 'Wiki API', type: :request do
 
   let!(:tn) { TagName.create!(name: 'spec_wiki_title') }
   let!(:page) do
-    WikiPage.create!(tag_name: tn, created_user: user, updated_user: user).tap do |p|
+    WikiPage.create!(
+      tag_name: tn,
+      body: 'init',
+      created_user: user,
+      updated_user: user
+    ).tap do |p|
       Wiki::Commit.content!(page: p, body: 'init', created_user: user, message: 'init')
     end
   end
@@ -99,6 +104,17 @@ RSpec.describe 'Wiki API', type: :request do
         end
             .to change(WikiPage, :count).by(1)
             .and change(WikiRevision, :count).by(1)
+            .and change(WikiVersion, :count).by(1)
+
+        version = page.wiki_versions.order(:version_no).last
+
+        expect(version).to have_attributes(
+          version_no: 1,
+          event_type: 'create',
+          title: 'TestPage',
+          body: "a\nb\nc",
+          created_by_user_id: member.id
+        )
 
         expect(response).to have_http_status(:created)
 
@@ -135,6 +151,41 @@ RSpec.describe 'Wiki API', type: :request do
         # "a" の WikiLine が増殖しない（1行のはず）
         expect(WikiLine.where(body: 'a').count).to eq(1)
       end
+
+      it 'deduplicates duplicated new lines before upsert' do
+        duplicated = 'duplicated_line_for_wiki_line_upsert_spec'
+
+        post endpoint,
+             params: { title: 'DuplicateNewLine', body: "#{ duplicated }\n#{ duplicated }" },
+             headers: auth_headers(member)
+
+        expect(response).to have_http_status(:created)
+
+        page = WikiPage.find(json.fetch('id'))
+        rev = page.current_revision
+
+        expect(rev.lines_count).to eq(2)
+        expect(WikiLine.where(body: duplicated).count).to eq(1)
+        expect(rev.wiki_lines.where(body: duplicated).count).to eq(1)
+        expect(rev.wiki_revision_lines.count).to eq(2)
+      end
+
+      it 'normalises CRLF and strips trailing newlines' do
+        post endpoint,
+             params: { title: 'NormalisedBody', body: "a\r\nb\r\n\r\n", message: 'normalise' },
+             headers: auth_headers(member)
+
+        expect(response).to have_http_status(:created)
+
+        page = WikiPage.find(json.fetch('id'))
+        rev = page.current_revision
+        version = page.wiki_versions.order(:version_no).last
+
+        expect(page.body).to eq("a\nb")
+        expect(version.body).to eq("a\nb")
+        expect(rev.lines_count).to eq(2)
+        expect(rev.wiki_lines.order('wiki_revision_lines.position').map(&:body)).to eq(['a', 'b'])
+      end
     end
   end
 
@@ -146,17 +197,14 @@ RSpec.describe 'Wiki API', type: :request do
       { 'X-Transfer-Code' => user.inheritance_code }
     end
 
-    #let!(:page) { create(:wiki_page, title: 'TestPage') }
-    let!(:page) do
-      build(:wiki_page, title: 'TestPage').tap do |p|
-        puts p.errors.full_messages unless p.valid?
-        p.save!
-      end
-    end
+    let!(:test_tag_name) { TagName.create!(name: 'TestPage') }
 
-    before do
-      # 初期版を 1 つ作っておく（更新が“2版目”になるように）
-      Wiki::Commit.content!(page: page, body: "a\nb", created_user: member, message: 'init')
+    let!(:page) do
+      Wiki::Commit.create_content!(
+          tag_name: test_tag_name,
+          body: "a\nb",
+          created_by_user: member,
+          message: 'init')
     end
 
     context 'when not logged in' do
@@ -200,7 +248,18 @@ RSpec.describe 'Wiki API', type: :request do
           put "/wiki/#{page.id}",
               params: { title: 'TestPage', body: "x\ny", message: 'edit', base_revision_id: current_id },
               headers: auth_headers(member)
-        end.to change(WikiRevision, :count).by(1)
+        end
+            .to change(WikiRevision, :count).by(1)
+            .and change(WikiVersion, :count).by(1)
+
+        version = page.wiki_versions.order(:version_no).last
+
+        expect(version).to have_attributes(
+          event_type: 'update',
+          title: 'TestPage',
+          body: "x\ny",
+          created_by_user_id: member.id
+        )
 
         expect(response).to have_http_status(:ok)
 
@@ -211,6 +270,48 @@ RSpec.describe 'Wiki API', type: :request do
         expect(page.body).to eq("x\ny")
         expect(rev.base_revision_id).to eq(current_id)
       end
+
+      it 'wiki page に対応する tag があれば tag version も作成する' do
+        linked_tag_name = TagName.create!(name: 'wiki_linked_tag_for_version')
+        linked_tag = Tag.create!(tag_name: linked_tag_name, category: :general)
+        linked_page = WikiPage.create!(
+          tag_name: linked_tag_name,
+          body: 'before',
+          created_user: member,
+          updated_user: member
+        )
+
+        Wiki::Commit.content!(
+          page: linked_page,
+          body: 'before',
+          created_user: member,
+          message: 'init'
+        )
+
+        current_id = linked_page.wiki_revisions.maximum(:id)
+
+        expect {
+          put "/wiki/#{ linked_page.id }",
+              params: {
+                title: 'wiki_linked_tag_for_version',
+                body: 'after',
+                message: 'edit',
+                base_revision_id: current_id,
+              },
+              headers: auth_headers(member)
+        }
+            .to change(WikiRevision, :count).by(1)
+            .and change(WikiVersion, :count).by(1)
+            .and change { linked_tag.reload.tag_versions.count }.by(1)
+
+        expect(response).to have_http_status(:ok)
+
+        version = linked_tag.reload.tag_versions.order(:version_no).last
+
+        expect(version.event_type).to eq('update')
+        expect(version.name).to eq('wiki_linked_tag_for_version')
+        expect(version.created_by_user_id).to eq(member.id)
+      end
     end
 
     # TODO: コンフリクト未実装のため，実装したらコメント外す．
@@ -263,11 +364,11 @@ RSpec.describe 'Wiki API', type: :request do
     before do
       # 追加で検索ヒット用
       TagName.create!(name: 'spec_wiki_title_2')
-      WikiPage.create!(tag_name: TagName.find_by!(name: 'spec_wiki_title_2'),
+      WikiPage.create!(tag_name: TagName.find_by!(name: 'spec_wiki_title_2'), body: 'init',
                        created_user: user, updated_user: user)
 
       TagName.create!(name: 'unrelated_title')
-      WikiPage.create!(tag_name: TagName.find_by!(name: 'unrelated_title'),
+      WikiPage.create!(tag_name: TagName.find_by!(name: 'unrelated_title'), body: 'init',
                        created_user: user, updated_user: user)
     end
 
@@ -329,7 +430,7 @@ RSpec.describe 'Wiki API', type: :request do
     it 'returns empty array when page has no revisions and filtered by id' do
       # 別ページを作って revision 無し
       tn2 = TagName.create!(name: 'spec_no_rev')
-      p2 = WikiPage.create!(tag_name: tn2, created_user: user, updated_user: user)
+      p2 = WikiPage.create!(tag_name: tn2, body: 'init', created_user: user, updated_user: user)
 
       get "/wiki/changes?id=#{p2.id}"
       expect(response).to have_http_status(:ok)
@@ -398,29 +499,27 @@ RSpec.describe 'Wiki API', type: :request do
       expect(json['older_revision_id']).to eq(rev_a.id)
       expect(json['newer_revision_id']).to eq(page.current_revision.id)
     end
+  end
 
-    it 'returns 422 when "to" is redirect revision' do
-      # redirect revision を作る
-      tn2 = TagName.create!(name: 'redirect_target')
-      target = WikiPage.create!(tag_name: tn2, created_user: user, updated_user: user)
-
-      Wiki::Commit.redirect!(page: page, redirect_page: target, created_user: user, message: 'redir')
-      redirect_rev = page.current_revision
-      expect(redirect_rev).to be_redirect
-
-      get "/wiki/#{page.id}/diff?from=#{rev_a.id}&to=#{redirect_rev.id}"
-      expect(response).to have_http_status(:unprocessable_entity)
-    end
-
-    it 'returns 422 when "from" is redirect revision' do
-      tn2 = TagName.create!(name: 'redirect_target2')
-      target = WikiPage.create!(tag_name: tn2, created_user: user, updated_user: user)
-
-      Wiki::Commit.redirect!(page: page, redirect_page: target, created_user: user, message: 'redir2')
-      redirect_rev = page.current_revision
+  describe 'Wiki::Commit.redirect!' do
+    it 'raises because redirect revisions are deprecated' do
+      target_tag_name = TagName.create!(name: 'redirect_deprecated_target')
+      target = WikiPage.create!(
+        tag_name: target_tag_name,
+        body: 'target',
+        created_user: user,
+        updated_user: user
+      )
 
-      get "/wiki/#{page.id}/diff?from=#{redirect_rev.id}&to=#{rev_b.id}"
-      expect(response).to have_http_status(:unprocessable_entity)
+      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
 end
diff --git a/backend/spec/services/wiki/commit_spec.rb b/backend/spec/services/wiki/commit_spec.rb
new file mode 100644
index 0000000..d8513c5
--- /dev/null
+++ b/backend/spec/services/wiki/commit_spec.rb
@@ -0,0 +1,120 @@
+require 'rails_helper'
+
+RSpec.describe Wiki::Commit do
+  let(:user) { create_member_user! }
+
+  def create_page(title: 'commit_spec_page', body: 'initial body')
+    tag_name = TagName.create!(name: title)
+
+    Wiki::Commit.create_content!(
+        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 'records tag version when page has corresponding tag' do
+      tag_name = TagName.create!(name: 'commit_linked_tag')
+      tag = Tag.create!(tag_name:, category: :general)
+      page = WikiPage.create!(
+        tag_name:,
+        body: '',
+        created_user: user,
+        updated_user: user
+      )
+
+      expect {
+        described_class.content!(
+          page:,
+          body: 'body',
+          created_user: user,
+          message: 'init'
+        )
+      }
+          .to change(WikiVersion, :count).by(1)
+          .and change { tag.reload.tag_versions.count }.by(1)
+    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