backend/app/models/post.rb

@@ -7,7 +7,8 @@ class Post < ApplicationRecord
   has_many :active_post_tags, -> { kept }, class_name: 'PostTag', inverse_of: :post
   has_many :post_tags_with_discarded, -> { with_discarded }, class_name: 'PostTag'
   has_many :tags, through: :active_post_tags
-  has_many :active_tags, -> { where(deprecated_at: nil) }, through: :active_post_tags, source: :tag
+  has_many :active_tags, -> { where(tags: { deprecated_at: nil }) },
+           through: :active_post_tags, source: :tag
 
   has_many :user_post_views, dependent: :delete_all
   has_many :post_similarities, dependent: :delete_all

backend/spec/requests/gekanator_learning_spec.rb

@@ -897,6 +897,37 @@ RSpec.describe 'Gekanator learning API', type: :request do
   end
 
   describe 'GET /gekanator/questions' do
+    it 'omits questions for deprecated tags' do
+      active_tag = Tag.create!(name: 'active_question_tag', category: :general)
+      deprecated_tag = Tag.create!(
+        name: 'deprecated_question_tag',
+        category: :general,
+        deprecated_at: Time.current
+      )
+
+      [active_tag, deprecated_tag].each do |question_tag|
+        GekanatorQuestion.create!(
+          text: "#{ question_tag.name }?",
+          kind: 'tag',
+          source: 'admin_curated',
+          status: 'accepted',
+          priority_weight: 1.0,
+          condition: {
+            type: 'tag',
+            key: "#{ question_tag.category }:#{ question_tag.name }"
+          },
+          created_by: admin
+        )
+      end
+
+      get '/gekanator/questions'
+
+      expect(response).to have_http_status(:ok)
+      question_ids = json.fetch('questions').map { |question| question.fetch('id') }
+      expect(question_ids).to include('tag:general:active_question_tag')
+      expect(question_ids).not_to include('tag:general:deprecated_question_tag')
+    end
+
     it 'returns accepted questions only and includes example_answers for post_similarity questions' do
       sign_in_as admin
 

backend/spec/requests/gekanator_posts_spec.rb

@@ -0,0 +1,33 @@
+require 'rails_helper'
+
+
+RSpec.describe 'Gekanator posts API', type: :request do
+  describe 'GET /gekanator/posts' do
+    it 'omits deprecated tags and returns the stored similarity cosine' do
+      active_tag = Tag.create!(name: 'active tag', category: :general)
+      deprecated_tag = Tag.create!(
+        name: 'deprecated tag',
+        category: :general,
+        deprecated_at: Time.current
+      )
+      post_record = Post.create!(title: 'source', url: 'https://example.com/source')
+      target_post = Post.create!(title: 'target', url: 'https://example.com/target')
+
+      PostTag.create!(post: post_record, tag: active_tag)
+      PostTag.create!(post: post_record, tag: deprecated_tag)
+      PostTag.create!(post: target_post, tag: deprecated_tag)
+      PostSimilarity.create!(post: post_record, target_post:, cos: 0.375)
+
+      get '/gekanator/posts'
+
+      expect(response).to have_http_status(:ok)
+
+      post_json = json.fetch('posts').find { |post| post.fetch('id') == post_record.id }
+      expect(post_json.fetch('tags').map { |tag| tag.fetch('name') }).to eq(['active tag'])
+      expect(post_json.fetch('post_similarity_edges')).to contain_exactly(
+        'target_post_id' => target_post.id,
+        'cos' => 0.375
+      )
+    end
+  end
+end

backend/spec/requests/posts_spec.rb

@@ -517,6 +517,24 @@ RSpec.describe 'Posts API', type: :request do
         expect([true, false]).to include(json['viewed'])
       end
 
+      it 'omits deprecated tags' do
+        deprecated_tag = Tag.create!(
+          name: 'deprecated_post_tag',
+          category: :general,
+          deprecated_at: Time.current
+        )
+        PostTag.create!(post: post_record, tag: deprecated_tag)
+
+        request
+
+        expect(response).to have_http_status(:ok)
+        tag_names = json.fetch('tags').flat_map { |node|
+          [node.fetch('name')] + node.fetch('children').map { |child| child.fetch('name') }
+        }
+        expect(tag_names).to include('spec_tag')
+        expect(tag_names).not_to include('deprecated_post_tag')
+      end
+
       context 'when post has parent, child, and sibling posts' do
         let!(:parent_post) do
           create_parent_post!(
@@ -697,6 +715,52 @@ RSpec.describe 'Posts API', type: :request do
       expect(names).not_to include('manko')
     end
 
+    it 'rejects a deprecated tag specified directly' do
+      Tag.create!(
+        name: 'deprecated_direct_tag',
+        category: :general,
+        deprecated_at: Time.current
+      )
+      sign_in_as(member)
+
+      post '/posts', params: post_write_params(
+        title: 'new post',
+        url: 'https://example.com/deprecated-direct-tag',
+        tags: 'deprecated_direct_tag',
+        thumbnail: dummy_upload
+      )
+
+      expect(response).to have_http_status(:unprocessable_entity)
+      expect(json.fetch('errors')).to include(
+        'tags' => ['廃止済みタグは付与できません．']
+      )
+    end
+
+    it 'expands through 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
+      )
+      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)
+      sign_in_as(member)
+
+      post '/posts', params: post_write_params(
+        title: 'expanded post',
+        url: 'https://example.com/expanded-deprecated-parent',
+        tags: 'active_child',
+        thumbnail: dummy_upload
+      )
+
+      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')
+    end
+
     context "when nico tag already exists in tags" do
       before do
         Tag.find_undiscard_or_create_by!(
@@ -930,6 +994,26 @@ RSpec.describe 'Posts API', type: :request do
       expect(names).to include('spec_tag_2')
     end
 
+    it 'rejects a deprecated tag specified directly' do
+      Tag.create!(
+        name: 'deprecated_update_tag',
+        category: :general,
+        deprecated_at: Time.current
+      )
+      sign_in_as(member)
+
+      put "/posts/#{ post_record.id }", params: post_update_params(
+        post_record,
+        title: 'updated title',
+        tags: 'deprecated_update_tag'
+      )
+
+      expect(response).to have_http_status(:unprocessable_entity)
+      expect(json.fetch('errors')).to include(
+        'tags' => ['廃止済みタグは付与できません．']
+      )
+    end
+
     context "when nico tag already exists in tags" do
       before do
         Tag.find_undiscard_or_create_by!(

backend/spec/requests/tag_wiki_history_integrity_spec.rb

@@ -89,6 +89,7 @@ RSpec.describe 'Tag and wiki history integrity', type: :request do
           category: 'general',
           aliases: '',
           parent_tags: '',
+          deprecated: '0',
         }
       }
           .to change(TagVersion, :count).by(2)
@@ -123,6 +124,7 @@ RSpec.describe 'Tag and wiki history integrity', type: :request do
           category: 'meme',
           aliases: '',
           parent_tags: '',
+          deprecated: '0',
         }
       }
           .to change(TagVersion, :count).by(2)
@@ -149,6 +151,7 @@ RSpec.describe 'Tag and wiki history integrity', type: :request do
           category: 'general',
           aliases: 'put_tag_alias_only_alias',
           parent_tags: '',
+          deprecated: '0',
         }
       }
           .to change(TagVersion, :count).by(2)

backend/spec/requests/tags_spec.rb

@@ -76,6 +76,27 @@ RSpec.describe 'Tags API', type: :request do
       expect(response_tags.first['id']).to eq(meme.id)
     end
 
+    it 'filters tags by deprecated state' do
+      deprecated_tag = Tag.create!(
+        name: 'deprecated_filter',
+        category: :general,
+        deprecated_at: Time.current
+      )
+      active_tag = Tag.create!(name: 'active_filter', category: :general)
+
+      get '/tags', params: { name: '_filter', deprecated: '1' }
+
+      expect(response).to have_http_status(:ok)
+      expect(response_names).to include(deprecated_tag.name)
+      expect(response_names).not_to include(active_tag.name)
+
+      get '/tags', params: { name: '_filter', deprecated: '0' }
+
+      expect(response).to have_http_status(:ok)
+      expect(response_names).to include(active_tag.name)
+      expect(response_names).not_to include(deprecated_tag.name)
+    end
+
     it 'filters tags by post_count range' do
       low = Tag.create!(tag_name: TagName.create!(name: 'pc_low'), category: :general)
       mid = Tag.create!(tag_name: TagName.create!(name: 'pc_mid'), category: :general)
@@ -301,6 +322,21 @@ RSpec.describe 'Tags API', type: :request do
       expect(t['matched_alias']).to eq('unko')
       expect(json.map { |x| x['name'] }).not_to include('unknown')
     end
+
+    it 'omits deprecated tags' do
+      deprecated_tag = Tag.create!(
+        name: 'spec_deprecated',
+        category: :general,
+        deprecated_at: Time.current
+      )
+      deprecated_tag.update_columns(post_count: 1)
+
+      get '/tags/autocomplete', params: { q: 'spec_', present: '0' }
+
+      expect(response).to have_http_status(:ok)
+      expect(json.map { |item| item.fetch('name') }).to include('spec_tag')
+      expect(json.map { |item| item.fetch('name') }).not_to include('spec_deprecated')
+    end
   end
 
   describe 'GET /tags/name/:name' do
@@ -585,6 +621,26 @@ RSpec.describe 'Tags API', type: :request do
       expect(row['has_children']).to eq(true)
       expect(row['children']).to eq([])
     end
+
+    it 'passes through deprecated tags when finding children' do
+      deprecated_middle = Tag.create!(
+        name: 'depth_deprecated_middle',
+        category: :character,
+        deprecated_at: Time.current
+      )
+      visible_descendant = Tag.create!(
+        name: 'depth_visible_descendant',
+        category: :material
+      )
+      TagImplication.create!(parent_tag: root_material, tag: deprecated_middle)
+      TagImplication.create!(parent_tag: deprecated_middle, tag: visible_descendant)
+
+      get '/tags/with-depth', params: { parent: root_material.id }
+
+      expect(response).to have_http_status(:ok)
+      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
   end
 
   describe 'GET /tags/name/:name/materials' do
@@ -732,6 +788,20 @@ RSpec.describe 'Tags API', type: :request do
         expect(tag.category).to eq('general')
       end
 
+      it 'deprecated がなければ 422 を返す' do
+        put "/tags/#{ tag.id }", params: {
+          name: 'new',
+          category: 'general',
+          aliases: '',
+          parent_tags: '',
+        }
+
+        expect(response).to have_http_status(:unprocessable_entity)
+        expect(json.fetch('errors')).to include(
+          'deprecated' => ['廃止状態は必須です．']
+        )
+      end
+
       it 'name, category, aliases, parent tags をまとめて更新できる' do
         old_parent = Tag.create!(
           tag_name: TagName.create!(name: 'put_old_parent'),
@@ -749,6 +819,7 @@ RSpec.describe 'Tags API', type: :request do
           category: 'meme',
           aliases: 'put_alias_a put_alias_b put_alias_a',
           parent_tags: 'put_kept_parent put_new_parent',
+          deprecated: '0',
         }
 
         expect(response).to have_http_status(:ok)
@@ -793,6 +864,7 @@ RSpec.describe 'Tags API', type: :request do
           category: 'general',
           aliases: 'spec_tag put_alias_self_test',
           parent_tags: '',
+          deprecated: '0',
         }
 
         expect(response).to have_http_status(:ok)
@@ -810,6 +882,7 @@ RSpec.describe 'Tags API', type: :request do
           category: 'general',
           aliases: 'unko',
           parent_tags: 'spec_tag',
+          deprecated: '0',
         }
 
         expect(response).to have_http_status(:ok)
@@ -825,6 +898,7 @@ RSpec.describe 'Tags API', type: :request do
             category: 'meta',
             aliases: '',
             parent_tags: '',
+            deprecated: '0',
           }
         }.to change(TagVersion, :count).by(2)
 
@@ -860,6 +934,7 @@ RSpec.describe 'Tags API', type: :request do
           category: 'general',
           aliases: 'unko',
           parent_tags: new_parent.name,
+          deprecated: '0',
         }
 
         expect(response).to have_http_status(:ok)
@@ -875,6 +950,7 @@ RSpec.describe 'Tags API', type: :request do
             category: 'nico',
             aliases: '',
             parent_tags: '',
+            deprecated: '0',
           }
         }.not_to change(TagVersion, :count)
 
@@ -896,6 +972,7 @@ RSpec.describe 'Tags API', type: :request do
             category: 'nico',
             aliases: '',
             parent_tags: '',
+            deprecated: '0',
           }
         }.not_to change(NicoTagVersion, :count)
 
@@ -916,6 +993,7 @@ RSpec.describe 'Tags API', type: :request do
             category: old_category,
             aliases: '',
             parent_tags: '',
+            deprecated: '0',
           }
         }.not_to change(TagVersion, :count)
 
@@ -946,6 +1024,7 @@ RSpec.describe 'Tags API', type: :request do
             category: 'meme',
             aliases: 'unko',
             parent_tags: '',
+            deprecated: '0',
           }
         }
             .to change(TagVersion, :count).by(2)
@@ -981,6 +1060,7 @@ RSpec.describe 'Tags API', type: :request do
             category: 'general',
             aliases: 'unko put_stolen_alias',
             parent_tags: '',
+            deprecated: '0',
           }
         }
             .to change { tag.reload.tag_versions.count }.by(2)
@@ -1015,6 +1095,7 @@ RSpec.describe 'Tags API', type: :request do
           category: 'general',
           aliases: 'unko',
           parent_tags: child.name,
+          deprecated: '0',
         }
 
         expect(response).to have_http_status(:unprocessable_entity)
@@ -1036,6 +1117,7 @@ RSpec.describe 'Tags API', type: :request do
             category: 'general',
             aliases: 'unko',
             parent_tags: '',
+            deprecated: '0',
           }
         }
             .to change(TagVersion, :count).by(2)

backend/spec/tasks/post_similarity_calc_spec.rb

@@ -4,11 +4,12 @@ require 'rails_helper'
 RSpec.describe 'post_similarity:calc' do
   include RakeTaskHelper
 
-  it 'calls Similarity::Calc with Post and :tags' do
+  it 'calculates similarities from active tags only' do
     # 必要最低限のデータ
     t1 = Tag.create!(name: "t1")
     t2 = Tag.create!(name: "t2")
     t3 = Tag.create!(name: "t3")
+    deprecated_tag = Tag.create!(name: 'deprecated', deprecated_at: Time.current)
 
     p1 = Post.create!(url: "https://example.com/1")
     p2 = Post.create!(url: "https://example.com/2")
@@ -22,6 +23,8 @@ RSpec.describe 'post_similarity:calc' do
     PostTag.create!(post: p2, tag: t3)
 
     PostTag.create!(post: p3, tag: t3)
+    PostTag.create!(post: p1, tag: deprecated_tag)
+    PostTag.create!(post: p2, tag: deprecated_tag)
 
     expect { run_rake_task("post_similarity:calc") }
       .to change { PostSimilarity.count }.from(0)
@@ -29,6 +32,6 @@ RSpec.describe 'post_similarity:calc' do
     ps = PostSimilarity.find_by!(post_id: p1.id, target_post_id: p2.id)
     ps_rev = PostSimilarity.find_by!(post_id: p2.id, target_post_id: p1.id)
     expect(ps_rev.cos).to eq(ps.cos)
+    expect(ps.cos).to be_within(0.0001).of(0.5)
   end
 end
-

backend/spec/tasks/tag_similarity_calc_spec.rb

@@ -4,11 +4,12 @@ require 'rails_helper'
 RSpec.describe 'tag_similarity:calc' do
   include RakeTaskHelper
 
-  it 'calls Similarity::Calc with Tag and :posts' do
+  it 'calculates similarities for active tags only' do
     # 必要最低限のデータ
     t1 = Tag.create!(name: "t1")
     t2 = Tag.create!(name: "t2")
     t3 = Tag.create!(name: "t3")
+    deprecated_tag = Tag.create!(name: 'deprecated', deprecated_at: Time.current)
 
     p1 = Post.create!(url: "https://example.com/1")
     p2 = Post.create!(url: "https://example.com/2")
@@ -22,6 +23,7 @@ RSpec.describe 'tag_similarity:calc' do
     PostTag.create!(post: p2, tag: t3)
 
     PostTag.create!(post: p3, tag: t3)
+    PostTag.create!(post: p1, tag: deprecated_tag)
 
     expect { run_rake_task("tag_similarity:calc") }
       .to change { TagSimilarity.count }.from(0)
@@ -29,6 +31,7 @@ RSpec.describe 'tag_similarity:calc' do
     ps = TagSimilarity.find_by!(tag_id: t1.id, target_tag_id: t2.id)
     ps_rev = TagSimilarity.find_by!(tag_id: t2.id, target_tag_id: t1.id)
     expect(ps_rev.cos).to eq(ps.cos)
+    expect(TagSimilarity.where(tag_id: deprecated_tag.id)).to be_empty
+    expect(TagSimilarity.where(target_tag_id: deprecated_tag.id)).to be_empty
   end
 end
-

frontend/src/lib/gekanator.test.ts

@@ -1,9 +1,11 @@
 import { beforeEach, describe, expect, it, vi } from 'vitest'
 
-import { apiPost } from '@/lib/api'
+import { apiGet, apiPost } from '@/lib/api'
 import {
   buildGekanatorQuestions,
   expectedAnswerForQuestion,
+  fetchGekanatorPosts,
+  fetchGekanatorQuestions,
   learnedSemanticSideForPost,
   questionIdForCondition,
   restoreGekanatorQuestion,
@@ -24,6 +26,7 @@ vi.mock('@/lib/api', () => ({
 }))
 
 const mockedApiPost = vi.mocked(apiPost)
+const mockedApiGet = vi.mocked(apiGet)
 
 const post = (overrides: Partial<Post> = {}): Post => ({
   id: 1,
@@ -43,6 +46,24 @@ const post = (overrides: Partial<Post> = {}): Post => ({
   ...overrides,
 })
 
+describe('Gekanator API functions', () => {
+  it('returns posts from the Gekanator posts endpoint', async () => {
+    const posts = [post()]
+    mockedApiGet.mockResolvedValueOnce({ posts })
+
+    await expect(fetchGekanatorPosts()).resolves.toEqual(posts)
+    expect(mockedApiGet).toHaveBeenCalledWith('/gekanator/posts')
+  })
+
+  it('returns questions from the Gekanator questions endpoint', async () => {
+    const questions: StoredGekanatorQuestion[] = []
+    mockedApiGet.mockResolvedValueOnce({ questions })
+
+    await expect(fetchGekanatorQuestions()).resolves.toEqual(questions)
+    expect(mockedApiGet).toHaveBeenCalledWith('/gekanator/questions')
+  })
+})
+
 describe('expectedAnswerForQuestion', () => {
   it('returns a direct example answer when present', () => {
     const question: StoredGekanatorQuestion = {
@@ -126,6 +147,7 @@ describe('expectedAnswerForQuestion', () => {
               postCount: 1,
               createdAt: '2026-06-10T00:00:00.000Z',
               updatedAt: '2026-06-10T00:00:00.000Z',
+              deprecatedAt: null,
               hasWiki: false,
               hasDeerjikists: false,
               materialId: null,

frontend/src/lib/tags.test.ts

@@ -58,6 +58,20 @@ describe ('tags API functions', () => {
     )
   })
 
+  it.each ([
+    [true, '1'],
+    [false, '0'],
+  ] as const) ('maps deprecated=%s to %s', async (deprecated, expected) => {
+    api.apiGet.mockResolvedValueOnce ({ tags: [], count: 0 })
+
+    await fetchTags ({ ...baseParams, deprecated })
+
+    expect (api.apiGet).toHaveBeenCalledWith (
+        '/tags',
+        { params: expect.objectContaining ({ deprecated: expected }) },
+    )
+  })
+
   it ('returns null when tag fetches fail', async () => {
     api.apiGet.mockRejectedValueOnce (new Error ('missing'))
     api.apiGet.mockRejectedValueOnce (new Error ('missing'))

frontend/src/pages/tags/TagListPage.test.tsx

@@ -14,13 +14,22 @@ vi.mock ('@/lib/tags', () => tagsApi)
 describe ('TagListPage', () => {
   it ('loads tags from URL filters and renders the results table', async () => {
     tagsApi.fetchTags.mockResolvedValueOnce ({
-      tags: [buildTag ({ id: 7, name: '虹夏', category: 'character', postCount: 99 })],
+      tags: [buildTag ({
+        id: 7,
+        name: '虹夏',
+        category: 'character',
+        postCount: 99,
+        deprecatedAt: '2026-06-01T00:00:00.000Z',
+      })],
       count: 1,
     })
 
     renderWithProviders (
         <TagListPage/>,
-        { route: '/tags?name=%E8%99%B9&category=character&page=3&post_count_gte=5' },
+        {
+          route:
+              '/tags?name=%E8%99%B9&category=character&page=3&post_count_gte=5&deprecated=1',
+        },
     )
 
     await waitFor (() => {
@@ -30,6 +39,7 @@ describe ('TagListPage', () => {
             category:     'character',
             page:         3,
             postCountGTE: 5,
+            deprecated:   true,
           }),
       )
     })
@@ -38,6 +48,8 @@ describe ('TagListPage', () => {
         '/tags/7',
     )
     expect (screen.getAllByText ('キャラクター').length).toBeGreaterThan (0)
+    expect (screen.getAllByRole ('combobox')[1]).toHaveValue ('1')
+    expect (screen.getAllByText ('廃止')).toHaveLength (2)
   })
 
   it ('navigates to a normalized search URL on submit', async () => {
@@ -46,7 +58,9 @@ describe ('TagListPage', () => {
     renderWithProviders (<TagListPage/>, { route: '/tags' })
 
     fireEvent.change (screen.getByRole ('textbox'), { target: { value: '虹夏' } })
-    fireEvent.change (screen.getByRole ('combobox'), { target: { value: 'character' } })
+    fireEvent.change (screen.getAllByRole ('combobox')[0], {
+      target: { value: 'character' },
+    })
     fireEvent.submit (screen.getByRole ('button', { name: '検索' }).closest ('form')!)
 
     await waitFor (() => {

frontend/tsconfig.app.json

@@ -27,5 +27,6 @@
       "@/*": ["*"]
     }
   },
-  "include": ["src"]
+  "include": ["src"],
+  "exclude": ["src/**/*.test.ts", "src/**/*.test.tsx", "src/test"]
 }