#378

AGENTS.md

@@ -107,11 +107,16 @@ npm run preview
 - Prefer single quotes for strings unless interpolation or escaping makes
   double quotes better.
 - Ruby: never put a space before method-call parentheses.
+- Ruby: `render` 系メソッド呼び出しでは、keyword 引数付きでも括弧を書かない。
 - Ruby: never put a line break immediately before `)`.
 - Ruby: do not use `%w` or `%i`.
+- In Ruby, when an `if` condition is split across multiple lines and combines
+  clauses with `&&` or `||`, wrap the whole condition in parentheses.
 - Ruby hashes are not blocks; keep `}` on the same line as the final pair.
 - Ruby hashes keep the first pair on the same line as `{` unless line length
   requires a break.
+- Short Ruby hashes may stay visually compact across two lines with the first
+  pair kept on the opening line and aligned continuation pairs below it.
 - Ruby blocks use separate `{ ... }` rules from hashes, with 2-space body
   indentation.
 - For arrays, never put whitespace or a line break immediately before `]`.

backend/AGENTS.md

@@ -72,17 +72,23 @@ service, representation, and spec.
 - Prefer precise, minimal changes.
 - Use single quotes unless interpolation or escaping makes double quotes better.
 - Do not put a space before Ruby method-call parentheses.
+- For `render`-family method calls, omit parentheses even when passing
+  keyword arguments.
 - Never put a line break immediately before `)` in Ruby.
 - Do not use `%w` or `%i` in new Ruby code.
 - Never write a Ruby line longer than 99 characters.
 - Aim to keep Ruby lines within 79 characters where practical.
 - For small Ruby method definitions that take keyword arguments, match the
   local no-parentheses style when nearby code uses it.
+- When an `if` condition is split across multiple lines and combines clauses
+  with `&&` or `||`, wrap the whole condition in parentheses.
 - Treat Ruby hash `{ ... }` style and Ruby block `{ ... }` style as separate
   rules.
 - Do not format Ruby hashes like Ruby blocks.
 - For Ruby hashes, keep the closing `}` on the same line as the final pair.
 - Keep the first pair on the same line as `{` by default.
+- Short Ruby hashes may stay visually compact across two lines with the first
+  pair kept on the opening line and aligned continuation pairs below it.
 - If the hash would exceed the line limit, break after `{` and indent pairs
   by 4 spaces.
 - Put one logical pair per line when the expression would otherwise become

backend/app/controllers/posts_controller.rb

@@ -148,10 +148,10 @@ class PostsController < ApplicationController
     ApplicationRecord.transaction do
       post.save!
 
-      tags = Tag.normalise_tags!(tag_names)
+      tags = Tag.normalise_tags!(tag_names, deny_deprecated: true)
       TagVersioning.record_tag_snapshots!(tags, created_by_user: current_user)
 
-      tags = Tag.expand_parent_tags(tags)
+      tags = Tag.expand_parent_tags(tags).reject(&:deprecated?)
       sync_post_tags!(post, tags)
 
       sync_parent_posts!(post, parent_post_ids)
@@ -165,6 +165,8 @@ class PostsController < ApplicationController
     render json: PostRepr.base(post), status: :created
   rescue Tag::NicoTagNormalisationError
     render_validation_error fields: { tags: 'ニコニコ・タグは直接指定できません．' }
+  rescue Tag::DeprecatedTagNormalisationError
+    render_unprocessable_entity '廃止済みタグは付与できません．', field: :tags
   rescue ArgumentError => e
     render_validation_error fields: { parent_post_ids: [e.message] }
   rescue ActiveRecord::RecordInvalid => e
@@ -255,6 +257,8 @@ class PostsController < ApplicationController
     render json:, status: :ok
   rescue Tag::NicoTagNormalisationError
     render_validation_error fields: { tags: ['ニコニコ・タグは直接指定できません．'] }
+  rescue Tag::DeprecatedTagNormalisationError
+    render_unprocessable_entity '廃止済みタグは付与できません．', field: :tags
   rescue ArgumentError => e
     render_validation_error fields: { parent_post_ids: [e.message] }
   rescue ActiveRecord::RecordInvalid => e
@@ -378,7 +382,7 @@ class PostsController < ApplicationController
   end
 
   def build_tag_tree_for tags
-    tags = tags.to_a
+    tags = tags.reject(&:deprecated?).to_a
     tag_ids = tags.map(&:id)
 
     implications = TagImplication.where(parent_tag_id: tag_ids, tag_id: tag_ids)
@@ -501,7 +505,8 @@ class PostsController < ApplicationController
   end
 
   def editable_tag_names_from_post post
-    post.tags.not_nico.joins(:tag_name).order('tag_names.name').pluck('tag_names.name')
+    post.tags.not_nico.where(deprecated_at: nil)
+        .joins(:tag_name).order('tag_names.name').pluck('tag_names.name')
   end
 
   def post_incoming_snapshot title:, original_created_from:, original_created_before:,
@@ -533,9 +538,10 @@ class PostsController < ApplicationController
   end
 
   def incoming_tag_names_for_snapshot raw_tag_names
-    tags = Tag.normalise_tags!(raw_tag_names, with_tagme: false)
+    tags = Tag.normalise_tags!(raw_tag_names, with_tagme: false,
+                                              deny_deprecated: true)
 
-    Tag.expand_parent_tags(tags).map(&:name).uniq.sort
+    Tag.expand_parent_tags(tags).reject(&:deprecated?).map(&:name).uniq.sort
   end
 
   def post_conflict_json post:, base_version_no:, base_snapshot:,
@@ -622,13 +628,14 @@ class PostsController < ApplicationController
                  original_created_from: snapshot[:original_created_from],
                  original_created_before: snapshot[:original_created_before])
 
-    editable_tags = Tag.normalise_tags!(snapshot[:tag_names], with_tagme: false)
+    editable_tags = Tag.normalise_tags!(snapshot[:tag_names], with_tagme: false,
+                                                               deny_deprecated: true)
     TagVersioning.record_tag_snapshots!(editable_tags, created_by_user: current_user)
 
     readonly_tags = post.tags.nico.to_a
 
     tags = readonly_tags + editable_tags
-    tags = Tag.expand_parent_tags(tags)
+    tags = Tag.expand_parent_tags(tags).reject(&:deprecated?)
 
     sync_post_tags!(post, tags)
     sync_parent_posts!(post, snapshot[:parent_post_ids])

backend/app/controllers/tag_versions_controller.rb

@@ -17,6 +17,7 @@ class TagVersionsController < ApplicationController
               AND prev.version_no = tag_versions.version_no - 1
         SQL
       .select('tag_versions.*', 'prev.name AS prev_name', 'prev.category AS prev_category',
+              'prev.deprecated_at AS prev_deprecated_at',
               'prev.aliases AS prev_aliases', 'prev.parent_tag_ids AS prev_parent_tag_ids')
     q = q.where('tag_versions.tag_id = ?', tag_id) if tag_id
 
@@ -62,6 +63,8 @@ class TagVersionsController < ApplicationController
         event_type: row.event_type,
         name: { current: row.name, prev: row.attributes['prev_name'] },
         category: { current: row.category, prev: row.attributes['prev_category'] },
+        deprecated_at: { current: row.deprecated_at&.iso8601,
+                         prev: row.attributes['prev_deprecated_at']&.iso8601 },
         aliases: build_version_values(cur_aliases, prev_aliases, key: :name),
         parent_tags:,
         created_at: row.created_at.iso8601,

backend/app/controllers/tags_controller.rb

@@ -1,5 +1,6 @@
 require 'net/http'
 require 'uri'
+require 'set'
 
 
 class TagsController < ApplicationController
@@ -14,6 +15,8 @@ class TagsController < ApplicationController
     post_count_between[1] = nil if post_count_between[1] < 0
     created_between = params[:created_from].presence, params[:created_to].presence
     updated_between = params[:updated_from].presence, params[:updated_to].presence
+    deprecated_given = params.key?(:deprecated)
+    deprecated = bool?(:deprecated)
 
     order = params[:order].to_s.split(':', 2).map(&:strip)
     unless order[0].in?(['name', 'category', 'post_count', 'created_at', 'updated_at'])
@@ -48,6 +51,9 @@ class TagsController < ApplicationController
     q = q.where('tags.created_at <= ?', created_between[1]) if created_between[1]
     q = q.where('tags.updated_at >= ?', updated_between[0]) if updated_between[0]
     q = q.where('tags.updated_at <= ?', updated_between[1]) if updated_between[1]
+    if deprecated_given
+      q = deprecated ? q.where.not(deprecated_at: nil) : q.where(deprecated_at: nil)
+    end
 
     sort_sql =
         case order[0]
@@ -77,37 +83,27 @@ class TagsController < ApplicationController
     parent_tag_id = params[:parent].to_i
     parent_tag_id = nil if parent_tag_id <= 0
 
+    graph = build_with_depth_graph
+
     tag_ids =
         if parent_tag_id
-          TagImplication.where(parent_tag_id:).select(:tag_id)
+          visible_child_tag_ids(parent_tag_id, graph)
         else
-          Tag.where.not(id: TagImplication.select(:tag_id)).select(:id)
+          visible_root_tag_ids(graph)
         end
 
     tags =
         Tag
         .joins(:tag_name)
         .includes(:tag_name, :materials, tag_name: :wiki_page)
-        .where(category: [:meme, :character, :material])
         .where(id: tag_ids)
         .order('tag_names.name')
         .distinct
         .to_a
 
-    has_children_tag_ids =
-        if tags.empty?
-          []
-        else
-          TagImplication
-              .joins(:tag)
-              .where(parent_tag_id: tags.map(&:id),
-                     tags: { category: [:meme, :character, :material] })
-              .distinct
-              .pluck(:parent_tag_id)
-        end
-
     render json: tags.map { |tag|
-      TagRepr.base(tag).merge(has_children: has_children_tag_ids.include?(tag.id), children: [])
+      TagRepr.base(tag).merge(has_children: visible_child_tag_ids(tag.id, graph).present?,
+                              children: [])
     }
   end
 
@@ -133,6 +129,7 @@ class TagsController < ApplicationController
 
     base = Tag.joins(:tag_name)
               .includes(:tag_name, :materials, tag_name: :wiki_page)
+              .where(deprecated_at: nil)
     base = base.where('tags.post_count > 0') if present_only
 
     canonical_hit =
@@ -252,18 +249,24 @@ class TagsController < ApplicationController
     category = params[:category].to_s.strip
     return render_unprocessable_entity('名前は必須です．', field: :name) if name.blank?
     return render_unprocessable_entity('カテゴリは必須です．', field: :category) if category.blank?
+    return render_unprocessable_entity '廃止状態は必須です．', field: :deprecated unless params.key?(:deprecated)
 
-    if name != tag.name &&
-        tag.in?([Tag.tagme, Tag.bot, Tag.no_deerjikist, Tag.video, Tag.niconico])
-      return render_unprocessable_entity('システム・タグの名称は変更できません．', field: :name)
-    end
-
-    if tag.nico? || category == 'nico'
-      return render_unprocessable_entity('ニコタグは変更できません．', field: :category)
+    if (name != tag.name &&
+        tag.in?([Tag.tagme, Tag.bot, Tag.no_deerjikist, Tag.video, Tag.niconico]))
+      return render_unprocessable_entity 'システム・タグの名称は変更できません．', field: :name
     end
 
     alias_names = params[:aliases].to_s.split.uniq
     parent_names = params[:parent_tags].to_s.split.uniq
+    deprecated = bool?(:deprecated)
+
+    if tag.nico? && deprecated
+      return render_unprocessable_entity 'ニコタグは廃止できません．', field: :deprecated
+    end
+
+    if tag.nico? || category == 'nico'
+      return render_unprocessable_entity 'ニコタグは変更できません．', field: :category
+    end
 
     ApplicationRecord.transaction do
       TagVersioning.ensure_snapshot!(tag, created_by_user: current_user)
@@ -272,7 +275,11 @@ class TagsController < ApplicationController
       name_changed = name != old_name
       wiki_page = tag.tag_name.wiki_page if name_changed
 
-      tag.update!(category:)
+      if tag.deprecated? == deprecated
+        tag.update!(category:)
+      else
+        tag.update!(category:, deprecated_at: deprecated ? Time.current : nil)
+      end
       tag.tag_name.update!(name:)
 
       alias_names << old_name if name_changed
@@ -300,11 +307,17 @@ class TagsController < ApplicationController
 
     name = params[:name].presence
     category = params[:category].presence
+    deprecated_given = params.key?(:deprecated)
+    deprecated = bool?(:deprecated)
 
     tag = Tag.find(params[:id])
 
+    if tag.nico? && deprecated_given && deprecated
+      return render_unprocessable_entity 'ニコタグは廃止できません．', field: :deprecated
+    end
+
     if tag.nico? || (category.present? && category == 'nico')
-      return render_unprocessable_entity('ニコタグは変更できません．', field: :category)
+      return render_unprocessable_entity 'ニコタグは変更できません．', field: :category
     end
 
     ApplicationRecord.transaction do
@@ -316,6 +329,9 @@ class TagsController < ApplicationController
 
       tag.tag_name.update!(name:) if name.present?
       tag.update!(category:) if category.present?
+      if deprecated_given && tag.deprecated? != deprecated
+        tag.update!(deprecated_at: deprecated ? Time.current : nil)
+      end
 
       tag.reload
 
@@ -332,6 +348,93 @@ class TagsController < ApplicationController
 
   private
 
+  def build_with_depth_graph
+    children_by_parent_id = Hash.new { |h, k| h[k] = [] }
+    parent_ids_by_child_id = Hash.new { |h, k| h[k] = [] }
+
+    TagImplication.pluck(:parent_tag_id, :tag_id).each do |parent_id, child_id|
+      children_by_parent_id[parent_id] << child_id
+      parent_ids_by_child_id[child_id] << parent_id
+    end
+
+    tag_ids = (children_by_parent_id.keys +
+               parent_ids_by_child_id.keys +
+               Tag.where(category: ['meme', 'character', 'material']).pluck(:id)).uniq
+
+    tags_by_id = Tag.where(id: tag_ids)
+                    .pluck(:id, :category, :deprecated_at)
+                    .each_with_object({ }) do |(id, category, deprecated_at), h|
+      h[id] = { category:, deprecated: deprecated_at.present? }
+    end
+
+    { children_by_parent_id:, parent_ids_by_child_id:, tags_by_id:,
+      visible_child_tag_ids_by_parent_id: { } }
+  end
+
+  def visible_root_tag_ids graph
+    graph[:tags_by_id].filter_map do |tag_id, attrs|
+      next unless with_depth_visible_tag?(attrs)
+      next unless visible_root_tag?(tag_id, graph)
+
+      tag_id
+    end
+  end
+
+  def visible_root_tag? tag_id, graph
+    seen = Set.new([tag_id])
+    stack = graph[:parent_ids_by_child_id][tag_id].dup
+
+    until stack.empty?
+      parent_id = stack.pop
+      next if seen.include?(parent_id)
+
+      seen << parent_id
+
+      parent = graph[:tags_by_id][parent_id]
+      next unless parent
+
+      return false unless parent[:deprecated]
+
+      stack.concat(graph[:parent_ids_by_child_id][parent_id])
+    end
+
+    true
+  end
+
+  def visible_child_tag_ids parent_tag_id, graph
+    cache = graph[:visible_child_tag_ids_by_parent_id]
+    return cache[parent_tag_id] if cache.key?(parent_tag_id)
+
+    visible_ids = Set.new
+
+    graph[:children_by_parent_id][parent_tag_id].each do |child_tag_id|
+      collect_visible_child_tag_ids(child_tag_id, graph, visible_ids, Set.new([parent_tag_id]))
+    end
+
+    cache[parent_tag_id] = visible_ids.to_a
+  end
+
+  def collect_visible_child_tag_ids tag_id, graph, visible_ids, seen
+    return if seen.include?(tag_id)
+
+    seen = seen.dup << tag_id
+    tag = graph[:tags_by_id][tag_id]
+    return unless tag
+
+    if tag[:deprecated]
+      graph[:children_by_parent_id][tag_id].each do |child_tag_id|
+        collect_visible_child_tag_ids(child_tag_id, graph, visible_ids, seen)
+      end
+      return
+    end
+
+    visible_ids << tag_id if with_depth_visible_tag?(tag)
+  end
+
+  def with_depth_visible_tag? tag
+    tag[:category].in?(['meme', 'character', 'material']) && !tag[:deprecated]
+  end
+
   def build_tag_children tag
     material = tag.materials.first
     file = nil

backend/app/models/tag.rb

@@ -8,6 +8,15 @@ class Tag < ApplicationRecord
     ;
   end
 
+  class DeprecatedTagNormalisationError < ArgumentError
+    attr_reader :tag_names
+
+    def initialize tag_names
+      @tag_names = Array(tag_names)
+      super('deprecated tags are not allowed')
+    end
+  end
+
   has_many :post_tags, inverse_of: :tag
   has_many :active_post_tags, -> { kept }, class_name: 'PostTag', inverse_of: :tag
   has_many :post_tags_with_discarded, -> { with_discarded }, class_name: 'PostTag'
@@ -58,6 +67,7 @@ class Tag < ApplicationRecord
   validate :nico_tag_name_must_start_with_nico
   validate :tag_name_must_be_canonical
   validate :category_must_be_deerjikist_with_deerjikists
+  validate :nico_tags_cannot_be_deprecated
 
   scope :nico_tags, -> { nico }
 
@@ -77,6 +87,8 @@ class Tag < ApplicationRecord
     (self.tag_name ||= build_tag_name).name = val
   end
 
+  def deprecated? = deprecated_at?
+
   def has_wiki = wiki_page.present?
 
   def material_id = materials.first&.id
@@ -92,7 +104,8 @@ class Tag < ApplicationRecord
 
   def self.normalise_tags! tag_names, with_tagme: true,
                                       with_no_deerjikist: true,
-                                      deny_nico: true
+                                      deny_nico: true,
+                                      deny_deprecated: false
     if deny_nico && tag_names.any? { |n| n.downcase.start_with?('nico:') }
       raise NicoTagNormalisationError
     end
@@ -101,6 +114,10 @@ class Tag < ApplicationRecord
       pf, cat = CATEGORY_PREFIXES.find { |p, _| name.downcase.start_with?(p) } || ['', nil]
       name = TagName.canonicalise(name.sub(/\A#{ pf }/i, '')).first
       find_or_create_by_tag_name!(name, category: (cat || :general)).tap do |tag|
+        if deny_deprecated && tag.deprecated?
+          raise DeprecatedTagNormalisationError, [tag.name]
+        end
+
         tag.update!(category: cat) if cat && tag.category != cat
       end
     end
@@ -228,4 +245,10 @@ class Tag < ApplicationRecord
       errors.add :category, 'ニジラーと紐づいてゐるタグはニジラー・カテゴリである必要があります．'
     end
   end
+
+  def nico_tags_cannot_be_deprecated
+    if nico? && deprecated_at.present?
+      errors.add :deprecated_at, 'ニコタグは廃止できません．'
+    end
+  end
 end

backend/app/representations/post_repr.rb

@@ -53,7 +53,7 @@ module PostRepr
   end
 
   def tag_json tags
-    tags.map { |tag| TagRepr.inline(tag) }
+    tags.reject(&:deprecated?).map { |tag| TagRepr.inline(tag) }
   end
 
   def thumbnail_url post

backend/app/representations/tag_repr.rb

@@ -2,7 +2,7 @@
 
 
 module TagRepr
-  BASE = { only: [:id, :category, :post_count, :created_at, :updated_at],
+  BASE = { only: [:id, :category, :post_count, :created_at, :updated_at, :deprecated_at],
            methods: [:name, :has_wiki, :material_id, :has_deerjikists] }.freeze
 
   module_function

backend/app/services/tag_version_recorder.rb

@@ -16,6 +16,7 @@ class TagVersionRecorder < VersionRecorder
   def snapshot_attributes
     { name: @record.name,
       category: @record.category,
+      deprecated_at: @record.deprecated_at,
       aliases: @record.snapshot_aliases.join(' '),
       parent_tag_ids: @record.snapshot_parent_tag_ids.join(' ') }
   end

backend/db/migrate/20260621000000_add_deprecated_at_to_tags.rb

@@ -0,0 +1,20 @@
+class AddDeprecatedAtToTags < ActiveRecord::Migration[8.0]
+  def up
+    add_column :tags, :deprecated_at, :datetime, after: :category
+    add_column :tag_versions, :deprecated_at, :datetime, after: :parent_tag_ids
+
+    add_index :tags, :deprecated_at
+
+    add_check_constraint :tags, "deprecated_at IS NULL OR category <> 'nico'",
+                         name: 'chk_tags_deprecated_at_not_nico'
+  end
+
+  def down
+    remove_check_constraint :tags, name: 'chk_tags_deprecated_at_not_nico'
+
+    remove_index :tags, :deprecated_at
+
+    remove_column :tag_versions, :deprecated_at, :datetime
+    remove_column :tags, :deprecated_at
+  end
+end

backend/db/schema.rb

@@ -10,7 +10,7 @@
 #
 # It's strongly recommended that you check this file into your version control system.
 
-ActiveRecord::Schema[8.0].define(version: 2026_06_12_000000) do
+ActiveRecord::Schema[8.0].define(version: 2026_06_21_000000) do
   create_table "active_storage_attachments", charset: "utf8mb4", collation: "utf8mb4_0900_ai_ci", force: :cascade do |t|
     t.string "name", null: false
     t.string "record_type", null: false
@@ -319,6 +319,7 @@ ActiveRecord::Schema[8.0].define(version: 2026_06_12_000000) do
     t.string "event_type", null: false
     t.string "name", null: false
     t.string "category", null: false
+    t.datetime "deprecated_at"
     t.text "aliases", null: false
     t.text "parent_tag_ids", null: false
     t.datetime "created_at", null: false
@@ -336,10 +337,13 @@ ActiveRecord::Schema[8.0].define(version: 2026_06_12_000000) do
     t.datetime "created_at", null: false
     t.datetime "updated_at", null: false
     t.integer "post_count", default: 0, null: false
+    t.datetime "deprecated_at"
     t.datetime "discarded_at"
     t.integer "version_no", null: false
+    t.index ["deprecated_at"], name: "index_tags_on_deprecated_at"
     t.index ["discarded_at"], name: "index_tags_on_discarded_at"
     t.index ["tag_name_id"], name: "index_tags_on_tag_name_id", unique: true
+    t.check_constraint "(`deprecated_at` is null) or (`category` <> _utf8mb4'nico')", name: "chk_tags_deprecated_at_not_nico"
     t.check_constraint "`version_no` > 0", name: "chk_tags_version_no_positive"
   end
 

frontend/src/lib/prefetchers.ts

@@ -17,6 +17,10 @@ const mWiki = match<{ title: string }> ('/wiki/:title')
 const mTag = match<{ id: string }> ('/tags/:id')
 
 
+const boolFromQuery = (value: string | null): boolean =>
+    ['1', 'true', 'on', 'yes', ''].includes ((value ?? '').toLowerCase ())
+
+
 const prefetchWikiPagesIndex: Prefetcher = async (qc, url) => {
   const title = url.searchParams.get ('title') ?? ''
 
@@ -156,13 +160,16 @@ const prefetchTagsIndex: Prefetcher = async (qc, url) => {
   const createdTo = url.searchParams.get ('created_to') ?? ''
   const updatedFrom = url.searchParams.get ('updated_from') ?? ''
   const updatedTo = url.searchParams.get ('updated_to') ?? ''
+  const deprecated = url.searchParams.has ('deprecated')
+      ? boolFromQuery (url.searchParams.get ('deprecated'))
+      : null
   const page = Number (url.searchParams.get ('page') || 1)
   const limit = Number (url.searchParams.get ('limit') || 20)
   const order = (url.searchParams.get ('order') ?? 'post_count:desc') as FetchTagsOrder
 
   const keys = {
       post, name, category, postCountGTE, postCountLTE, createdFrom, createdTo,
-      updatedFrom, updatedTo, page, limit, order }
+      updatedFrom, updatedTo, deprecated, page, limit, order }
 
   await qc.prefetchQuery ({
       queryKey: tagsKeys.index (keys),

frontend/src/lib/tags.test.ts

@@ -20,6 +20,7 @@ const baseParams: FetchTagsParams = {
   createdTo:    '',
   updatedFrom:  '',
   updatedTo:    '',
+  deprecated:   null,
   page:         1,
   limit:        30,
   order:        'updated_at:desc',

frontend/src/lib/tags.ts

@@ -10,7 +10,8 @@ import type { Deerjikist,
 
 export const fetchTags = async (
     { post, name, category, postCountGTE, postCountLTE, createdFrom, createdTo,
-      updatedFrom, updatedTo, page, limit, order }: FetchTagsParams,
+      updatedFrom, updatedTo, deprecated,
+      page, limit, order }: FetchTagsParams,
 ): Promise<{ tags:  Tag[]
 	     count: number }> =>
     await apiGet ('/tags', { params: {
@@ -23,6 +24,7 @@ export const fetchTags = async (
 	...(createdTo && { created_to: createdTo }),
 	...(updatedFrom && { updated_from: updatedFrom }),
 	...(updatedTo && { updated_to: updatedTo }),
+	...(deprecated != null && { deprecated: deprecated ? '1' : '0' }),
 	...(page && { page }),
 	...(limit && { limit }),
 	...(order && { order }) } })

frontend/src/pages/tags/TagDetailPage.tsx

@@ -19,7 +19,12 @@ import type { FC, FormEvent } from 'react'
 
 import type { Category, Tag } from '@/types'
 
-type TagFormField = 'name' | 'category' | 'aliases' | 'parentTags'
+type TagFormField =
+    | 'name'
+    | 'category'
+    | 'aliases'
+    | 'parentTags'
+    | 'deprecated'
 
 
 const TagDetailPage: FC = () => {
@@ -35,6 +40,7 @@ const TagDetailPage: FC = () => {
   const [category, setCategory] = useState<Category> ('general')
   const [aliases, setAliases] = useState ('')
   const [parentTags, setParentTags] = useState ('')
+  const [deprecated, setDeprecated] = useState (false)
   const [disabled, setDisabled] = useState (true)
   const { baseErrors, fieldErrors, clearValidationErrors, applyValidationError } =
       useValidationErrors<TagFormField> ()
@@ -50,6 +56,7 @@ const TagDetailPage: FC = () => {
     formData.append ('category', category)
     formData.append ('aliases', aliases)
     formData.append ('parent_tags', parentTags)
+    formData.append ('deprecated', deprecated ? '1' : '0')
 
     try
     {
@@ -59,6 +66,7 @@ const TagDetailPage: FC = () => {
       setCategory (data.category as Category)
       setAliases (data.aliases.join (' '))
       setParentTags (data.parents.map (t => t.name).join (' '))
+      setDeprecated (Boolean (data.deprecatedAt))
 
       qc.invalidateQueries ({ queryKey: postsKeys.root })
       qc.invalidateQueries ({ queryKey: tagsKeys.root })
@@ -82,6 +90,7 @@ const TagDetailPage: FC = () => {
     setCategory (tag.category as Category)
     setAliases (tag.aliases.join (' '))
     setParentTags (tag.parents.map (t => t.name).join (' '))
+    setDeprecated (Boolean (tag.deprecatedAt))
     setDisabled (tag.category === 'nico')
   }, [tag])
 
@@ -165,6 +174,17 @@ const TagDetailPage: FC = () => {
 		      </>)}
 		</FormField>
 
+		<FormField label="廃止済" messages={fieldErrors.deprecated}>
+		  {({ describedBy, invalid }) => (
+		      <input
+			  type="checkbox"
+			  disabled={disabled}
+			  checked={deprecated}
+			  onChange={e => setDeprecated (e.target.checked)}
+			  aria-describedby={describedBy}
+			  aria-invalid={invalid}/>)}
+		</FormField>
+
 		<div className="py-3">
 		  <button
 		      type="submit"

frontend/src/pages/tags/TagHistoryPage.tsx

@@ -20,17 +20,28 @@ import type { FC } from 'react'
 
 const renderDiff = (diff: { current: string | null; prev: string | null }) => (
     <>
-      {(diff.prev && diff.prev !== diff.current) && (
+      {diff.prev !== diff.current
+       ? (
 	  <>
 	    <del className="text-red-600 dark:text-red-400">
-	      {diff.prev}
+	      {diff.prev && <>{diff.prev}<br/></>}
 	    </del>
-	    {diff.current && <br/>}
-	  </>)}
-      {diff.current}
+	    <ins className="text-green-600 dark:text-green-400">
+	      {diff.current}
+	    </ins>
+	  </>)
+       : diff.current}
     </>)
 
 
+const tagStateLabel = (deprecatedAt: string | null) => deprecatedAt ? '廃止' : ''
+
+
+const renderStateDiff = (diff: { current: string | null; prev: string | null }) =>
+    renderDiff ({ current: tagStateLabel (diff.current),
+		  prev: tagStateLabel (diff.prev) })
+
+
 const TagHistoryPage: FC = () => {
   const location = useLocation ()
   const query = new URLSearchParams (location.search)
@@ -72,6 +83,8 @@ const TagHistoryPage: FC = () => {
 		    <col className="w-96"/>
 		    {/* カテゴリ */}
 		    <col className="w-96"/>
+		    {/* 状態 */}
+		    <col className="w-32"/>
 		    {/* 別名 */}
 		    <col className="w-[48rem]"/>
 		    {/* 上位タグ */}
@@ -87,6 +100,7 @@ const TagHistoryPage: FC = () => {
 		      <th className="p-2 text-left">版</th>
 		      <th className="p-2 text-left">名称</th>
 		      <th className="p-2 text-left">カテゴリ</th>
+		      <th className="p-2 text-left">状態</th>
 		      <th className="p-2 text-left">別名</th>
 		      <th className="p-2 text-left">上位タグ</th>
 		      <th className="p-2 text-left">更新日時</th>
@@ -106,6 +120,9 @@ const TagHistoryPage: FC = () => {
 				prev: (change.category.prev
 				       && CATEGORY_NAMES[change.category.prev]) })}
 			  </td>
+			  <td className="p-2 break-all">
+			    {renderStateDiff (change.deprecatedAt)}
+			  </td>
 			  <td className="p-2">
 			    {change.aliases.map ((tag, i) => (
 				tag.type === 'added'
@@ -178,6 +195,7 @@ const TagHistoryPage: FC = () => {
 					`/tags/${ change.tagId }`,
 					{ name: change.name.current,
 					  category: change.category.current,
+					  deprecated: change.deprecatedAt.current ? '1' : '0',
 					  aliases:
 					      change.aliases
 					      .filter (t => t.type !== 'removed')
@@ -211,4 +229,5 @@ const TagHistoryPage: FC = () => {
       </MainArea>)
 }
 
+
 export default TagHistoryPage

frontend/src/pages/tags/TagListPage.tsx

@@ -29,6 +29,13 @@ const setIf = (qs: URLSearchParams, k: string, v: string | null) => {
 }
 
 
+const boolFromQuery = (value: string | null): boolean =>
+    ['1', 'true', 'on', 'yes', ''].includes ((value ?? '').toLowerCase ())
+
+
+const tagStateLabel = (deprecatedAt: string | null) => deprecatedAt ? '廃止' : ''
+
+
 const TagListPage: FC = () => {
   const location = useLocation ()
 
@@ -48,6 +55,9 @@ const TagListPage: FC = () => {
   const qCreatedTo = query.get ('created_to') ?? ''
   const qUpdatedFrom = query.get ('updated_from') ?? ''
   const qUpdatedTo = query.get ('updated_to') ?? ''
+  const qDeprecated = query.has ('deprecated')
+      ? boolFromQuery (query.get ('deprecated'))
+      : null
   const order = (query.get ('order') || 'post_count:desc') as FetchTagsOrder
 
   const [name, setName] = useState ('')
@@ -58,6 +68,7 @@ const TagListPage: FC = () => {
   const [createdTo, setCreatedTo] = useState<string | null> (null)
   const [updatedFrom, setUpdatedFrom] = useState<string | null> (null)
   const [updatedTo, setUpdatedTo] = useState<string | null> (null)
+  const [deprecated, setDeprecated] = useState<boolean | null> (null)
 
   const keys = {
       page, limit, order,
@@ -69,7 +80,8 @@ const TagListPage: FC = () => {
       createdFrom: qCreatedFrom,
       createdTo: qCreatedTo,
       updatedFrom: qUpdatedFrom,
-      updatedTo: qUpdatedTo }
+      updatedTo: qUpdatedTo,
+      deprecated: qDeprecated }
   const { data, isLoading: loading } = useQuery ({
       queryKey: tagsKeys.index (keys),
       queryFn: () => fetchTags (keys) })
@@ -85,10 +97,11 @@ const TagListPage: FC = () => {
     setCreatedTo (qCreatedTo)
     setUpdatedFrom (qUpdatedFrom)
     setUpdatedTo (qUpdatedTo)
+    setDeprecated (qDeprecated)
 
     document.querySelector ('table')?.scrollIntoView ({ behavior: 'smooth' })
   }, [location.search, qCategory, qCreatedFrom, qCreatedTo, qName, qPostCountGTE,
-      qPostCountLTE, qUpdatedFrom, qUpdatedTo])
+      qPostCountLTE, qUpdatedFrom, qUpdatedTo, qDeprecated])
 
   const handleSearch = (e: FormEvent) => {
     e.preventDefault ()
@@ -104,6 +117,8 @@ const TagListPage: FC = () => {
     setIf (qs, 'created_to', createdTo)
     setIf (qs, 'updated_from', updatedFrom)
     setIf (qs, 'updated_to', updatedTo)
+    if (deprecated != null)
+      qs.set ('deprecated', deprecated ? '1' : '0')
     qs.set ('page', '1')
     qs.set ('order', order)
 
@@ -201,6 +216,21 @@ const TagListPage: FC = () => {
 		  </>)}
 	    </FormField>
 
+	    <FormField label="状態">
+	      {({ invalid }) => (
+		  <select
+		      value={deprecated == null ? '' : (deprecated ? '1' : '0')}
+		      onChange={e => setDeprecated (
+			  e.target.value === ''
+			  ? null
+			  : e.target.value === '1')}
+		      className={inputClass (invalid)}>
+		    <option value="">&nbsp;</option>
+		    <option value="0">有効</option>
+		    <option value="1">廃止</option>
+		  </select>)}
+	    </FormField>
+
 	    <div className="py-3">
 	      <button
 		  type="submit"
@@ -219,6 +249,7 @@ const TagListPage: FC = () => {
 		    <col className="w-72"/>
 		    <col className="w-16"/>
 		    <col className="w-48"/>
+		    <col className="w-32"/>
 		    <col className="w-72"/>
 		    <col className="w-48"/>
 		    <col className="w-56"/>
@@ -249,6 +280,7 @@ const TagListPage: FC = () => {
 			    currentOrder={order}
 			    defaultDirection={defaultDirection}/>
 		      </th>
+		      <th className="p-2 text-left whitespace-nowrap">状態</th>
 		      <th className="p-2 text-left whitespace-nowrap">別名</th>
 		      <th className="p-2 text-left whitespace-nowrap">上位タグ</th>
 		      <th className="p-2 text-left whitespace-nowrap">
@@ -280,6 +312,7 @@ const TagListPage: FC = () => {
 			  </td>
 			  <td className="p-2 text-right">{row.postCount}</td>
 			  <td className="p-2">{CATEGORY_NAMES[row.category]}</td>
+			  <td className="p-2">{tagStateLabel (row.deprecatedAt)}</td>
 			  <td className="p-2">{row.aliases.join (' ')}</td>
 			  <td className="p-2">
 			    {row.parents.map (t => (

frontend/src/test/factories.ts

@@ -13,6 +13,7 @@ export const buildTag = (overrides: Partial<Tag> = {}): Tag => ({
   id:             1,
   name:           'テストタグ',
   category:       'general',
+  deprecatedAt:   null,
   aliases:        [],
   parents:        [],
   postCount:      12,

frontend/src/types.ts

@@ -39,18 +39,19 @@ export type FetchTagsOrderField =
     | 'updated_at'
 
 export type FetchTagsParams = {
-    post:         number | null
-    name:         string
-    category:     Category | null
-    postCountGTE: number
-    postCountLTE: number | null
-    createdFrom:  string
-    createdTo:    string
-    updatedFrom:  string
-    updatedTo:    string
-    page:         number
-    limit:        number
-    order:        FetchTagsOrder }
+    post:           number | null
+    name:           string
+    category:       Category | null
+    postCountGTE:   number
+    postCountLTE:   number | null
+    createdFrom:    string
+    createdTo:      string
+    updatedFrom:    string
+    updatedTo:      string
+    deprecated:     boolean | null
+    page:           number
+    limit:          number
+    order:          FetchTagsOrder }
 
 export type FetchNicoTagsParams = {
     name:       string
@@ -196,6 +197,7 @@ export type Tag = {
     id:             number
     name:           string
     category:       Category
+    deprecatedAt:   string | null
     aliases:        string[]
     parents:        Tag[]
     postCount:      number
@@ -213,6 +215,7 @@ export type TagVersion = {
     eventType:              'create' | 'update' | 'discard' | 'restore'
     name:                   { current: string; prev: string | null }
     category:               { current: Category; prev: Category | null }
+    deprecatedAt:           { current: string | null; prev: string | null }
     aliases:                { name: string; type: 'context' | 'added' | 'removed' }[]
     parentTags:             { tag: Tag; type: 'context' | 'added' | 'removed' }[]
     createdAt:              string