#378

backend/app/controllers/wiki_pages_controller.rb

@@ -4,17 +4,18 @@ class WikiPagesController < ApplicationController
   def index
     title = params[:title].to_s.strip
     if title.blank?
-      return render json: WikiPageRepr.base(WikiPage.joins(:tag_name).includes(:tag_name))
+      return render json: WikiPageRepr.base(
+          WikiPage.joins(:tag_name).includes(tag_name: :tag))
     end
 
-    q = WikiPage.joins(:tag_name).includes(:tag_name)
+    q = WikiPage.joins(:tag_name).includes(tag_name: :tag)
         .where('tag_names.name LIKE ?', "%#{ WikiPage.sanitize_sql_like(title) }%")
     render json: WikiPageRepr.base(q.limit(20))
   end
 
   def show
     page = WikiPage.joins(:tag_name)
-                   .includes(:tag_name)
+                   .includes(tag_name: :tag)
                    .find_by(id: params[:id])
     render_wiki_page_or_404 page
   end
@@ -22,7 +23,7 @@ class WikiPagesController < ApplicationController
   def show_by_title
     title = params[:title].to_s.strip
     page = WikiPage.joins(:tag_name)
-                   .includes(:tag_name)
+                   .includes(tag_name: :tag)
                    .find_by(tag_name: { name: title })
     render_wiki_page_or_404 page
   end
@@ -51,7 +52,7 @@ class WikiPagesController < ApplicationController
     from = params[:from].presence
     to = params[:to].presence
 
-    page = WikiPage.joins(:tag_name).includes(:tag_name).find(id)
+    page = WikiPage.joins(:tag_name).includes(tag_name: :tag).find(id)
 
     from_rev = from && page.wiki_revisions.find(from)
     to_rev = to ? page.wiki_revisions.find(to) : page.current_revision
@@ -76,6 +77,7 @@ class WikiPagesController < ApplicationController
 
     render json: { wiki_page_id:      page.id,
                    title:             page.title,
+                   deprecated_at:     page.deprecated_at,
                    older_revision_id: from_rev&.id,
                    newer_revision_id: to_rev.id,
                    diff:              diff_json }
@@ -157,7 +159,7 @@ class WikiPagesController < ApplicationController
   def changes
     id = params[:id].presence
     q = WikiRevision.joins(wiki_page: :tag_name)
-                    .includes(:created_user, wiki_page: :tag_name)
+                    .includes(:created_user, wiki_page: { tag_name: :tag })
                     .order(id: :desc)
     q = q.where(wiki_page_id: id) if id
 
@@ -165,7 +167,9 @@ class WikiPagesController < ApplicationController
       { revision_id:  rev.id,
         pred:         rev.base_revision_id,
         succ:         nil,
-        wiki_page:    { id: rev.wiki_page_id, title: rev.wiki_page.title },
+        wiki_page:    { id: rev.wiki_page_id,
+                        title: rev.wiki_page.title,
+                        deprecated_at: rev.wiki_page.deprecated_at },
         user:         rev.created_user && { id: rev.created_user.id, name: rev.created_user.name },
         kind:         rev.kind,
         message:      rev.message,

backend/app/models/wiki_page.rb

@@ -22,6 +22,7 @@ class WikiPage < ApplicationRecord
   validates :body, presence: true
 
   def title = tag_name.name
+  def deprecated_at = tag_name.tag&.deprecated_at
 
   def title= val
     (self.tag_name ||= build_tag_name).name = val

backend/app/representations/wiki_page_repr.rb

@@ -2,7 +2,7 @@
 
 
 module WikiPageRepr
-  BASE = { methods: [:title] }.freeze
+  BASE = { methods: [:title, :deprecated_at] }.freeze
 
   module_function
 

backend/spec/models/tag_spec.rb

@@ -1,6 +1,79 @@
 require 'rails_helper'
 
 RSpec.describe Tag, type: :model do
+  describe '.normalise_tags!' do
+    it 'rejects deprecated tags when deny_deprecated is enabled' do
+      tag_name = TagName.create!(name: 'normalise deprecated tag')
+      deprecated_tag = Tag.create!(
+        tag_name:,
+        category: :general,
+        deprecated_at: 1.day.from_now
+      )
+
+      expect {
+        described_class.normalise_tags!(
+          [deprecated_tag.name],
+          deny_deprecated: true
+        )
+      }.to raise_error(Tag::DeprecatedTagNormalisationError) { |error|
+        expect(error.tag_names).to eq([deprecated_tag.name])
+      }
+    end
+  end
+
+  describe '.expand_parent_tags' do
+    it 'expands through multiple deprecated parents to an active ancestor' do
+      child = create(:tag, name: 'expand_child')
+      deprecated_parent = create(
+        :tag,
+        name: 'expand_deprecated_parent',
+        deprecated_at: Time.current
+      )
+      deprecated_grandparent = create(
+        :tag,
+        name: 'expand_deprecated_grandparent',
+        deprecated_at: Time.current
+      )
+      active_ancestor = create(:tag, name: 'expand_active_ancestor')
+      TagImplication.create!(tag: child, parent_tag: deprecated_parent)
+      TagImplication.create!(tag: deprecated_parent, parent_tag: deprecated_grandparent)
+      TagImplication.create!(tag: deprecated_grandparent, parent_tag: active_ancestor)
+
+      expanded = described_class.expand_parent_tags([child])
+
+      expect(expanded).to include(
+        child,
+        deprecated_parent,
+        deprecated_grandparent,
+        active_ancestor
+      )
+      expect(expanded.reject(&:deprecated?)).to contain_exactly(child, active_ancestor)
+    end
+
+    it 'terminates when implications contain a cycle' do
+      first = create(:tag, name: 'expand_cycle_first')
+      second = create(:tag, name: 'expand_cycle_second')
+      TagImplication.create!(tag: first, parent_tag: second)
+      TagImplication.create!(tag: second, parent_tag: first)
+
+      expect(described_class.expand_parent_tags([first])).to contain_exactly(first, second)
+    end
+  end
+
+  describe 'deprecated validation' do
+    it 'rejects deprecated nico tags' do
+      tag = build(
+        :tag,
+        name: 'nico:deprecated_validation',
+        category: :nico,
+        deprecated_at: Time.current
+      )
+
+      expect(tag).not_to be_valid
+      expect(tag.errors[:deprecated_at]).to include('ニコタグは廃止できません．')
+    end
+  end
+
   describe '.merge_tags!' do
     let!(:target_tag) { create(:tag, category: :general) }
     let!(:source_tag) { create(:tag, category: :general) }

backend/spec/requests/posts_spec.rb

@@ -736,16 +736,22 @@ RSpec.describe 'Posts API', type: :request do
       )
     end
 
-    it 'expands through deprecated parent tags and saves active ancestors' do
+    it 'expands through multiple deprecated parent tags and saves active ancestors' do
       child = Tag.create!(name: 'active_child', category: :general)
       deprecated_parent = Tag.create!(
         name: 'deprecated_parent',
         category: :general,
         deprecated_at: Time.current
       )
+      deprecated_grandparent = Tag.create!(
+        name: 'deprecated_grandparent',
+        category: :general,
+        deprecated_at: Time.current
+      )
       active_grandparent = Tag.create!(name: 'active_grandparent', category: :general)
       TagImplication.create!(tag: child, parent_tag: deprecated_parent)
-      TagImplication.create!(tag: deprecated_parent, parent_tag: active_grandparent)
+      TagImplication.create!(tag: deprecated_parent, parent_tag: deprecated_grandparent)
+      TagImplication.create!(tag: deprecated_grandparent, parent_tag: active_grandparent)
       sign_in_as(member)
 
       post '/posts', params: post_write_params(
@@ -758,7 +764,7 @@ RSpec.describe 'Posts API', type: :request do
       expect(response).to have_http_status(:created)
       saved_names = Post.find(json.fetch('id')).tags.map(&:name)
       expect(saved_names).to include('active_child', 'active_grandparent')
-      expect(saved_names).not_to include('deprecated_parent')
+      expect(saved_names).not_to include('deprecated_parent', 'deprecated_grandparent')
     end
 
     context "when nico tag already exists in tags" do

backend/spec/requests/tag_versions_spec.rb

@@ -21,6 +21,7 @@ RSpec.describe 'TagVersions API', type: :request do
     event_type:,
     name:,
     category:,
+    deprecated_at: nil,
     aliases: [],
     parent_tags: [],
     created_by_user:,
@@ -33,6 +34,7 @@ RSpec.describe 'TagVersions API', type: :request do
             event_type: event_type,
             name: name,
             category: category,
+            deprecated_at: deprecated_at,
             aliases: Array(aliases).join(' '),
             parent_tag_ids: Array(parent_tags).map(&:id).join(' '),
             created_by_user: created_by_user,
@@ -65,6 +67,7 @@ RSpec.describe 'TagVersions API', type: :request do
       event_type: 'update',
       name: 'new_tag_name',
       category: 'meme',
+      deprecated_at: t_v2,
       aliases: ['alias_shared', 'alias_new'],
       parent_tags: [parent_shared, parent_new],
       created_by_user: member,
@@ -133,6 +136,10 @@ RSpec.describe 'TagVersions API', type: :request do
         'current' => 'meme',
         'prev' => 'general'
       )
+      expect(latest.fetch('deprecated_at')).to eq(
+        'current' => t_v2.iso8601,
+        'prev' => nil
+      )
       expect(latest.fetch('aliases')).to include(
         { 'name' => 'alias_shared', 'type' => 'context' },
         { 'name' => 'alias_new', 'type' => 'added' },
@@ -178,6 +185,10 @@ RSpec.describe 'TagVersions API', type: :request do
         'current' => 'general',
         'prev' => nil
       )
+      expect(first.fetch('deprecated_at')).to eq(
+        'current' => nil,
+        'prev' => nil
+      )
       expect(first.fetch('aliases')).to include(
         { 'name' => 'alias_shared', 'type' => 'added' },
         { 'name' => 'alias_old', 'type' => 'added' }

backend/spec/requests/tags_spec.rb

@@ -80,7 +80,7 @@ RSpec.describe 'Tags API', type: :request do
       deprecated_tag = Tag.create!(
         name: 'deprecated_filter',
         category: :general,
-        deprecated_at: Time.current
+        deprecated_at: 1.day.from_now
       )
       active_tag = Tag.create!(name: 'active_filter', category: :general)
 
@@ -473,6 +473,32 @@ RSpec.describe 'Tags API', type: :request do
         expect(versions.second.created_by_user_id).to eq(member_user.id)
       end
 
+      it 'updates deprecated state and records it in tag versions' do
+        expect {
+          patch "/tags/#{ tag.id }", params: { deprecated: '1' }
+        }.to change(TagVersion, :count).by(2)
+
+        expect(response).to have_http_status(:ok)
+        expect(tag.reload.deprecated_at).to be_present
+
+        versions = tag.tag_versions.order(:version_no)
+        expect(versions.first.deprecated_at).to be_nil
+        expect(versions.second.deprecated_at).to eq(tag.deprecated_at)
+        expect(json.fetch('deprecated_at')).to be_present
+      end
+
+      it 'rejects deprecating a nico tag' do
+        nico_tag = Tag.create!(name: 'nico:deprecated_update', category: :nico)
+
+        patch "/tags/#{ nico_tag.id }", params: { deprecated: '1' }
+
+        expect(response).to have_http_status(:unprocessable_entity)
+        expect(nico_tag.reload.deprecated_at).to be_nil
+        expect(json.fetch('errors')).to include(
+          'deprecated' => ['ニコタグは廃止できません．']
+        )
+      end
+
       it 'returns 422 when changing normal tag category to nico' do
         expect {
           patch "/tags/#{tag.id}", params: { category: 'nico' }
@@ -641,6 +667,91 @@ RSpec.describe 'Tags API', type: :request do
       expect(json.map { |item| item.fetch('name') }).to eq(['depth_visible_descendant'])
       expect(json.map { |item| item.fetch('name') }).not_to include('depth_deprecated_middle')
     end
+
+    it 'passes through multiple deprecated tags for roots and has_children' do
+      active_child = Tag.create!(
+        name: 'depth_active_child_below_deprecated',
+        category: :character
+      )
+      deprecated_parent = Tag.create!(
+        name: 'depth_deprecated_parent',
+        category: :character,
+        deprecated_at: Time.current
+      )
+      deprecated_grandparent = Tag.create!(
+        name: 'depth_deprecated_grandparent',
+        category: :material,
+        deprecated_at: Time.current
+      )
+      active_ancestor = Tag.create!(
+        name: 'depth_active_ancestor',
+        category: :meme
+      )
+      TagImplication.create!(tag: active_child, parent_tag: deprecated_parent)
+      TagImplication.create!(tag: deprecated_parent, parent_tag: deprecated_grandparent)
+      TagImplication.create!(tag: deprecated_grandparent, parent_tag: active_ancestor)
+
+      get '/tags/with-depth'
+
+      root_names = json.map { |item| item.fetch('name') }
+      expect(root_names).to include('depth_active_ancestor')
+      expect(root_names).not_to include('depth_active_child_below_deprecated')
+      ancestor_json = json.find { |item| item.fetch('id') == active_ancestor.id }
+      expect(ancestor_json.fetch('has_children')).to eq(true)
+
+      get '/tags/with-depth', params: { parent: active_ancestor.id }
+
+      expect(json.map { |item| item.fetch('name') }).to include(
+        'depth_active_child_below_deprecated'
+      )
+      expect(json.map { |item| item.fetch('name') }).not_to include(
+        'depth_deprecated_parent',
+        'depth_deprecated_grandparent'
+      )
+    end
+
+    it 'treats an active tag with only deprecated ancestors as a root' do
+      active_child = Tag.create!(
+        name: 'depth_root_below_deprecated',
+        category: :character
+      )
+      deprecated_parent = Tag.create!(
+        name: 'depth_root_deprecated_parent',
+        category: :material,
+        deprecated_at: Time.current
+      )
+      TagImplication.create!(tag: active_child, parent_tag: deprecated_parent)
+
+      get '/tags/with-depth'
+
+      expect(json.map { |item| item.fetch('name') }).to include(
+        'depth_root_below_deprecated'
+      )
+      expect(json.map { |item| item.fetch('name') }).not_to include(
+        'depth_root_deprecated_parent'
+      )
+    end
+
+    it 'terminates when deprecated implications contain a cycle' do
+      first = Tag.create!(
+        name: 'depth_cycle_first',
+        category: :character,
+        deprecated_at: Time.current
+      )
+      second = Tag.create!(
+        name: 'depth_cycle_second',
+        category: :material,
+        deprecated_at: Time.current
+      )
+      TagImplication.create!(tag: first, parent_tag: root_material)
+      TagImplication.create!(tag: second, parent_tag: first)
+      TagImplication.create!(tag: first, parent_tag: second)
+
+      get '/tags/with-depth', params: { parent: root_material.id }
+
+      expect(response).to have_http_status(:ok)
+      expect(json).to eq([])
+    end
   end
 
   describe 'GET /tags/name/:name/materials' do

backend/spec/requests/wiki_spec.rb

@@ -18,6 +18,13 @@ RSpec.describe 'Wiki API', type: :request do
         created_by_user: user,
         message: 'init')
   end
+  let!(:tag) do
+    Tag.create!(
+      tag_name: tn,
+      category: :general,
+      deprecated_at: Time.zone.local(2026, 6, 1)
+    )
+  end
 
   describe 'GET /wiki' do
     it 'returns wiki pages with title' do
@@ -30,6 +37,8 @@ RSpec.describe 'Wiki API', type: :request do
 
       expect(json[0]).to have_key('title')
       expect(json.map { |p| p['title'] }).to include('spec_wiki_title')
+      wiki_json = json.find { |item| item.fetch('id') == page.id }
+      expect(wiki_json.fetch('deprecated_at')).to eq(tag.deprecated_at.iso8601(3))
     end
   end
 
@@ -48,7 +57,8 @@ RSpec.describe 'Wiki API', type: :request do
 
         expect(json).to include(
             'id' => page.id,
-            'title' => 'spec_wiki_title')
+            'title' => 'spec_wiki_title',
+            'deprecated_at' => tag.deprecated_at.iso8601(3))
       end
     end
 
@@ -409,7 +419,11 @@ RSpec.describe 'Wiki API', type: :request do
         'kind' => 'content',
         'message' => 'r2'
       )
-      expect(top['wiki_page']).to include('id' => page.id, 'title' => 'spec_wiki_title')
+      expect(top['wiki_page']).to include(
+        'id' => page.id,
+        'title' => 'spec_wiki_title',
+        'deprecated_at' => tag.deprecated_at.iso8601(3)
+      )
       expect(top['user']).to include('id' => user.id, 'name' => user.name)
       expect(top).to have_key('timestamp')
 
@@ -479,6 +493,7 @@ RSpec.describe 'Wiki API', type: :request do
       expect(json).to include(
         'wiki_page_id' => page.id,
         'title' => 'spec_wiki_title',
+        'deprecated_at' => tag.deprecated_at.iso8601(3),
         'older_revision_id' => rev_a.id,
         'newer_revision_id' => rev_b.id
       )

frontend/src/components/TagLink.test.tsx

@@ -18,6 +18,21 @@ describe ('TagLink', () => {
     expect (screen.getByText ('4')).toBeInTheDocument ()
   })
 
+  it ('does not append deprecated state to the rendered tag name', () => {
+    renderWithProviders (
+        <TagLink
+            tag={buildTag ({
+                name:         '旧タグ',
+                deprecatedAt: '2026-06-01T00:00:00.000Z',
+            })}
+            withWiki={false}
+            withCount={false}/>,
+    )
+
+    expect (screen.getByRole ('link', { name: '旧タグ' })).toBeInTheDocument ()
+    expect (screen.queryByText ('（廃止）')).not.toBeInTheDocument ()
+  })
+
   it ('links wiki markers to the correct detail route', () => {
     renderWithProviders (
         <TagLink tag={buildTag ({ hasWiki: true, name: 'a/b' })}/>,

frontend/src/components/TagLink.tsx

@@ -128,4 +128,4 @@ const TagLink: FC<Props> = ({ tag,
       </>)
 }
 
-export default TagLink
+export default TagLink

frontend/src/lib/tags.ts

@@ -66,7 +66,6 @@ export const fetchTagByName = async (name: string): Promise<Tag | null> => {
   }
 }
 
-
 export const fetchTagChanges = async (
     { id, page, limit }: {
 	id?:    string

frontend/src/pages/wiki/WikiDetailPage.test.tsx

@@ -0,0 +1,54 @@
+import { screen } from '@testing-library/react'
+import { Route, Routes } from 'react-router-dom'
+import { describe, expect, it, vi } from 'vitest'
+
+import WikiDetailPage from '@/pages/wiki/WikiDetailPage'
+import { buildTag, buildWikiPage } from '@/test/factories'
+import { renderWithProviders } from '@/test/render'
+
+const wikiApi = vi.hoisted (() => ({
+  fetchWikiPage:        vi.fn (),
+  fetchWikiPageByTitle: vi.fn (),
+}))
+
+const tagsApi = vi.hoisted (() => ({
+  fetchTagByName: vi.fn (),
+}))
+
+const postsApi = vi.hoisted (() => ({
+  fetchPosts: vi.fn (),
+}))
+
+vi.mock ('@/lib/wiki', () => wikiApi)
+vi.mock ('@/lib/tags', () => tagsApi)
+vi.mock ('@/lib/posts', () => postsApi)
+
+describe ('WikiDetailPage', () => {
+  it ('renders deprecated state outside the wiki title link', async () => {
+    wikiApi.fetchWikiPageByTitle.mockResolvedValueOnce (buildWikiPage ({
+      title:        '旧タグ',
+      deprecatedAt: '2026-06-01T00:00:00.000Z',
+    }))
+    tagsApi.fetchTagByName.mockResolvedValueOnce (buildTag ({
+      name:         '旧タグ',
+      deprecatedAt: '2026-06-01T00:00:00.000Z',
+    }))
+    postsApi.fetchPosts.mockResolvedValueOnce ({ posts: [], count: 0 })
+
+    renderWithProviders (
+        <Routes>
+          <Route path="/wiki/:title" element={<WikiDetailPage/>}/>
+        </Routes>,
+        { route: '/wiki/%E6%97%A7%E3%82%BF%E3%82%B0' },
+    )
+
+    const marker = await screen.findByText ('（廃止）')
+    const heading = marker.closest ('h1')
+    const link = screen.getByRole ('link', { name: '旧タグ' })
+
+    expect (heading).not.toBeNull ()
+    expect (heading!).toHaveTextContent ('旧タグ（廃止）')
+    expect (link).toBeInTheDocument ()
+    expect (marker.closest ('a')).toBeNull ()
+  })
+})

frontend/src/pages/wiki/WikiDetailPage.tsx

@@ -39,6 +39,7 @@ const WikiDetailPage: FC = () => {
       queryFn:  () => fetchWikiPageByTitle (title, { version }) })
 
   const effectiveTitle = wikiPage?.title ?? title
+  const deprecated = wikiPage?.deprecatedAt != null
 
   const { data: tag } = useQuery ({
       enabled:  Boolean (effectiveTitle),
@@ -88,7 +89,7 @@ const WikiDetailPage: FC = () => {
   return (
       <MainArea>
 	<Helmet>
-	  <title>{`${ title } Wiki | ${ SITE_TITLE }`}</title>
+	  <title>{`${ effectiveTitle }${ deprecated ? '（廃止）' : '' } Wiki | ${ SITE_TITLE }`}</title>
 	  {!(wikiPage?.body) && <meta name="robots" content="noindex"/>}
 	</Helmet>
 
@@ -110,10 +111,13 @@ const WikiDetailPage: FC = () => {
 
 	<article className="prose dark:prose-invert mx-auto p-4">
 	  <h1 className="prose-a:no-underline">
-	    <TagLink tag={tag ?? defaultTag}
+	    <TagLink tag={tag ?? { ...defaultTag,
+				   name: effectiveTitle,
+				   deprecatedAt: wikiPage?.deprecatedAt ?? null }}
 		     withWiki={false}
 		     withCount={false}
 		     {...(version && { to: `/wiki/${ encodeURIComponent (title) }` })}/>
+	    {deprecated && <span>（廃止）</span>}
 	  </h1>
 	  {loading ? <div>Loading...</div> : <WikiBody title={title} body={wikiPage?.body}/>}
 

frontend/src/pages/wiki/WikiDiffPage.test.tsx

@@ -16,6 +16,7 @@ describe ('WikiDiffPage', () => {
     api.apiGet.mockResolvedValueOnce ({
       wikiPageId:      3,
       title:           '差分対象',
+      deprecatedAt:    null,
       olderRevisionId: 1,
       newerRevisionId: 2,
       diff: [
@@ -43,4 +44,26 @@ describe ('WikiDiffPage', () => {
     expect (screen.getByText ('added line')).toBeInTheDocument ()
     expect (screen.getByText ('removed line')).toBeInTheDocument ()
   })
+
+  it ('appends deprecated state to the wiki title', async () => {
+    api.apiGet.mockResolvedValueOnce ({
+      wikiPageId:      3,
+      title:           '廃止 Wiki',
+      deprecatedAt:    '2026-06-01T00:00:00.000Z',
+      olderRevisionId: 1,
+      newerRevisionId: 2,
+      diff:            [],
+    })
+
+    renderWithProviders (
+        <Routes>
+          <Route path="/wiki/:id/diff" element={<WikiDiffPage/>}/>
+        </Routes>,
+        { route: '/wiki/3/diff?from=1&to=2' },
+    )
+
+    expect (await screen.findByRole ('heading', {
+      name: '廃止 Wiki（廃止）',
+    })).toBeInTheDocument ()
+  })
 })

frontend/src/pages/wiki/WikiDiffPage.tsx

@@ -23,6 +23,9 @@ const WikiDiffPage: FC = () => {
   const query = new URLSearchParams (location.search)
   const from = query.get ('from')
   const to = query.get ('to')
+  const displayTitle = diff
+      ? `${ diff.title }${ diff.deprecatedAt != null ? '（廃止）' : '' }`
+      : ''
 
   useEffect (() => {
     void (async () => {
@@ -33,9 +36,9 @@ const WikiDiffPage: FC = () => {
   return (
       <MainArea>
 	<Helmet>
-	  <title>{`Wiki 差分: ${ diff?.title } | ${ SITE_TITLE }`}</title>
+	  <title>{`Wiki 差分: ${ displayTitle } | ${ SITE_TITLE }`}</title>
 	</Helmet>
-	<PageTitle>{diff?.title}</PageTitle>
+	<PageTitle>{displayTitle}</PageTitle>
 	<div className="prose mx-auto p-4">
 	  {diff
 	   ? (

frontend/src/pages/wiki/WikiHistoryPage.test.tsx

@@ -0,0 +1,38 @@
+import { screen } from '@testing-library/react'
+import { describe, expect, it, vi } from 'vitest'
+
+import WikiHistoryPage from '@/pages/wiki/WikiHistoryPage'
+import { renderWithProviders } from '@/test/render'
+
+const api = vi.hoisted (() => ({
+  apiGet: vi.fn (),
+}))
+
+vi.mock ('@/lib/api', () => api)
+
+describe ('WikiHistoryPage', () => {
+  it ('renders deprecated state outside the wiki title link', async () => {
+    api.apiGet.mockResolvedValueOnce ([{
+      revisionId:  2,
+      pred:        1,
+      succ:        null,
+      wikiPage:    {
+	id:           3,
+	title:        '旧タグ',
+	deprecatedAt: '2026-06-01T00:00:00.000Z',
+      },
+      user:        { id: 4, name: 'tester' },
+      kind:        'content',
+      message:     'updated',
+      timestamp:   '2026-06-02T00:00:00.000Z',
+    }])
+
+    renderWithProviders (<WikiHistoryPage/>)
+
+    const link = await screen.findByRole ('link', { name: '旧タグ' })
+    const marker = screen.getByText ('（廃止）')
+
+    expect (link).toHaveAttribute ('href', '/wiki/%E6%97%A7%E3%82%BF%E3%82%B0?version=2')
+    expect (marker.closest ('a')).toBeNull ()
+  })
+})

frontend/src/pages/wiki/WikiHistoryPage.tsx

@@ -59,6 +59,7 @@ const WikiHistoryPage: FC = () => {
 			to={`/wiki/${ encodeURIComponent (change.wikiPage.title) }?version=${ change.revisionId }`}>
 		      {change.wikiPage.title}
 		    </PrefetchLink>
+		    {change.wikiPage.deprecatedAt != null && <span>（廃止）</span>}
 		  </td>
 		  <td className="p-2">
 		    {change.pred == null ? '新規' : '更新'}

frontend/src/pages/wiki/WikiSearchPage.test.tsx

@@ -42,4 +42,21 @@ describe ('WikiSearchPage', () => {
     })
     expect (await screen.findByRole ('link', { name: '検索結果' })).toBeInTheDocument ()
   })
+
+  it ('marks deprecated wiki tags in the result title', async () => {
+    api.apiGet.mockResolvedValueOnce ([
+        buildWikiPage ({
+            title:        '旧タグ',
+            deprecatedAt: '2026-06-01T00:00:00.000Z',
+        }),
+    ])
+
+    renderWithProviders (<WikiSearchPage/>)
+
+    const link = await screen.findByRole ('link', { name: '旧タグ' })
+    const marker = screen.getByText ('（廃止）')
+
+    expect (link).toBeInTheDocument ()
+    expect (marker.closest ('a')).toBeNull ()
+  })
 })

frontend/src/pages/wiki/WikiSearchPage.tsx

@@ -86,6 +86,7 @@ const WikiSearchPage: FC = () => {
 		      <PrefetchLink to={`/wiki/${ encodeURIComponent (page.title) }`}>
 			{page.title}
 		      </PrefetchLink>
+		      {page.deprecatedAt != null && <span>（廃止）</span>}
 		    </td>
 		    <td className="p-2">
 		      {dateString (page.updatedAt)}

frontend/src/test/factories.ts

@@ -58,6 +58,7 @@ export const buildUser = (overrides: Partial<User> = {}): User => ({
 export const buildWikiPage = (overrides: Partial<WikiPage> = {}): WikiPage => ({
   id:            1,
   title:         'テストWiki',
+  deprecatedAt:  null,
   createdUserId: 1,
   updatedUserId: 1,
   createdAt:     '2026-01-02T03:04:05.000Z',

frontend/src/types.ts

@@ -299,6 +299,7 @@ export type ViewFlagBehavior = typeof ViewFlagBehavior[keyof typeof ViewFlagBeha
 export type WikiPage = {
     id:             number
     title:          string
+    deprecatedAt:   string | null
     createdUserId:  number
     updatedUserId:  number
     createdAt:      string
@@ -312,7 +313,7 @@ export type WikiPageChange = {
     revisionId: number
     pred:       number | null
     succ:       null
-    wikiPage:   Pick<WikiPage, 'id' | 'title'>
+    wikiPage:   Pick<WikiPage, 'id' | 'title' | 'deprecatedAt'>
     user:       Pick<User, 'id' | 'name'>
     kind:       'content' | 'redirect'
     message:    string | null
@@ -321,6 +322,7 @@ export type WikiPageChange = {
 export type WikiPageDiff = {
     wikiPageId:       number
     title:            string
+    deprecatedAt:     string | null
     olderRevisionId:  number | null
     newerRevisionId:  number
     diff:             WikiPageDiffDiff[] }