#41

AGENTS.md

@@ -126,12 +126,16 @@ npm run preview
 - In TypeScript and TSX only, replace every leading run of 8 spaces with a tab.
 - Tabs are only for leading indentation, never for spaces after non-space text.
 - Do not add production dependencies without explicit approval.
+- Do not create, modify, or run tests unless the user explicitly asks for
+  test work. When the user asks for tests, keep working and rerun them until
+  they pass or the remaining failure is clearly blocked.
 
 ## Backend rules
 
 - Inspect existing routes, controllers, models, services, and specs before
   editing backend behavior.
-- For API behavior changes, add or update request specs under `backend/spec/requests`.
+- For API behavior changes, add or update request specs under
+  `backend/spec/requests` only when the user explicitly asks for tests.
 - Prefer RSpec for new backend tests; existing minitest files under
   `backend/test` do not make minitest the default for new coverage.
 - Do not weaken authentication, BAN user checks, or IP BAN checks.
@@ -211,10 +215,11 @@ function PostFormTagsArea ({ tags, setTags }: Props) {
   `node_modules`, `dist`, `tmp`, `log`, and `storage` unless explicitly needed.
 - Before touching wiki, tag, versioning, BAN, IP BAN, or authentication
   behavior, inspect the related request specs and service objects.
-- If frontend code changes, run the existing frontend verification commands
-  that apply: `npm run build`, `npm run lint`, and `npm run test:run`.
-- If backend code changes, run the relevant RSpec command; for broad backend
-  changes, run `bundle exec rspec`.
+- If frontend code changes, run only non-test verification commands that
+  apply, such as `npm run build` and `npm run lint`. Run `npm run test:run`
+  only when the user explicitly asks for tests.
+- If backend code changes, do not run RSpec unless the user explicitly asks
+  for tests.
 - If a verification command cannot be run or fails, report the exact command and failure.
 
 ## Completion criteria
@@ -222,7 +227,8 @@ function PostFormTagsArea ({ tags, setTags }: Props) {
 A task is complete only when:
 
 - implementation is complete,
-- relevant verification commands pass, or failures are clearly explained,
+- relevant non-test verification commands pass, or failures are clearly
+  explained,
 - unrelated files are not changed,
 - migrations and schema are consistent when schema changes are made,
 - user-facing behavior is documented when needed.

backend/AGENTS.md

@@ -47,6 +47,10 @@ bundle exec rspec
 
 If a command cannot be run or fails, report the exact command and failure.
 
+Do not create, modify, or run tests unless the user explicitly asks for test
+work. When the user asks for tests, keep working and rerun them until they
+pass or the remaining failure is clearly blocked.
+
 ## Rails structure
 
 - `app/controllers`: API controllers.
@@ -116,7 +120,8 @@ service, representation, and spec.
 - `User#banned?` and `IpAddress#banned?` check `banned_at.present?`.
 - Do not weaken BAN or IP BAN behavior.
 - If changing request authentication or controller before actions, add or
-  update request specs covering banned users and banned IP addresses.
+  update request specs covering banned users and banned IP addresses only when
+  the user explicitly asks for tests.
 
 ## RSpec
 
@@ -130,8 +135,9 @@ service, representation, and spec.
 - `AuthHelper#sign_in_as(user)` stubs
   `ApplicationController#current_user`; use it when matching existing
   request spec style.
-- Add or update request specs for API behavior changes, especially status
-  codes, permissions, response shape, and version conflict behavior.
+- Add or update request specs for API behavior changes only when the user
+  explicitly asks for tests, especially status codes, permissions, response
+  shape, and version conflict behavior.
 
 ## Migrations
 
@@ -164,7 +170,8 @@ service, representation, and spec.
   the record `version_no`.
 - Do not update versioned records without considering whether a version snapshot must be created.
 - For optimistic concurrency paths, preserve `base_version_no`, `force`, and
-  `merge` semantics and cover conflicts in request specs.
+  `merge` semantics. Cover conflicts in request specs only when the user
+  explicitly asks for tests.
 
 ## Domain cautions
 

backend/app/controllers/gekanator_games_controller.rb

@@ -0,0 +1,23 @@
+class GekanatorGamesController < ApplicationController
+  def create
+    return head :not_found unless current_user&.admin?
+
+    guessed_post_id = params.require(:guessed_post_id)
+    correct_post_id = params[:correct_post_id].presence
+    answers = params.require(:answers).as_json
+
+    game = GekanatorGame.new(
+        user: current_user,
+        guessed_post_id:,
+        correct_post_id:,
+        won: correct_post_id.present? && guessed_post_id.to_i == correct_post_id.to_i,
+        question_count: answers.length,
+        answers:)
+
+    if game.save
+      render json: { id: game.id }, status: :created
+    else
+      render json: { errors: game.errors.full_messages }, status: :unprocessable_entity
+    end
+  end
+end

backend/app/controllers/gekanator_posts_controller.rb

@@ -0,0 +1,46 @@
+class GekanatorPostsController < ApplicationController
+  def index
+    return head :not_found unless current_user&.admin?
+
+    posts =
+        Post
+        .preload(tags: :tag_name)
+        .with_attached_thumbnail
+        .order(Arel.sql(
+            'COALESCE(posts.original_created_before - INTERVAL 1 MINUTE, ' \
+            'posts.original_created_from, posts.created_at) DESC, posts.id DESC'))
+
+    render json: { posts: posts.map { |post| post_json(post) } }
+  end
+
+  private
+
+  def post_json post
+    {
+      id: post.id,
+      url: post.url,
+      title: post.title,
+      thumbnail: thumbnail_url(post),
+      thumbnail_base: post.thumbnail_base,
+      original_created_from: post.original_created_from,
+      original_created_before: post.original_created_before,
+      tags: post.tags.map { |tag| tag_json(tag) }
+    }
+  end
+
+  def tag_json tag
+    {
+      id: tag.id,
+      name: tag.name,
+      category: tag.category
+    }
+  end
+
+  def thumbnail_url post
+    return nil unless post.thumbnail.attached?
+
+    rails_storage_proxy_url(post.thumbnail, only_path: false)
+  rescue
+    nil
+  end
+end

backend/app/controllers/gekanator_question_suggestions_controller.rb

@@ -0,0 +1,46 @@
+class GekanatorQuestionSuggestionsController < ApplicationController
+  def create
+    return head :not_found unless current_user&.admin?
+
+    game = GekanatorGame.find_by(id: params.require(:gekanator_game_id))
+    return head :not_found unless game
+
+    suggestion = GekanatorQuestionSuggestion.new(
+        gekanator_game: game,
+        user: current_user,
+        question_text: params.require(:question_text),
+        answer: params.require(:answer))
+
+    if suggestion.save
+      render json: {
+        id: suggestion.id,
+        count: game.question_suggestions.count
+      }, status: :created
+    else
+      render_validation_error suggestion
+    end
+  end
+
+  def ai_convert
+    return head :not_found unless current_user&.admin?
+
+    suggestion = GekanatorQuestionSuggestion.find_by(id: params[:id])
+    return head :not_found unless suggestion
+    if Gekanator::AiRunBudget.exceeded_after_next_run?
+      suggestion.gekanator_ai_runs.create!(
+          model: 'budget_guard',
+          status: 'blocked_budget',
+          input_tokens: 0,
+          output_tokens: 0,
+          estimated_cost_jpy: 0)
+      return head :payment_required
+    end
+
+    Gekanator::QuestionSuggestionAiConverter.call(
+        suggestion: suggestion,
+        user: current_user)
+    head :no_content
+  rescue NotImplementedError
+    head :not_implemented
+  end
+end

backend/app/controllers/gekanator_questions_controller.rb

@@ -0,0 +1,57 @@
+class GekanatorQuestionsController < ApplicationController
+  def index
+    return head :not_found unless current_user&.admin?
+
+    questions = GekanatorQuestion.accepted.order(priority_weight: :desc, id: :asc)
+
+    render json: {
+      questions: questions.map { |question| question_json(question) }
+    }
+  end
+
+  private
+
+  def question_json question
+    {
+      id: question_id_for(question),
+      text: question.text,
+      kind: question.kind,
+      condition: condition_json(question.condition),
+      source: question.source,
+      priority_weight: question.priority_weight
+    }
+  end
+
+  def question_id_for question
+    condition = condition_json(question.condition).deep_symbolize_keys
+
+    case condition[:type]
+    when 'tag'
+      "tag:#{ condition[:key] }"
+    when 'source'
+      "source:#{ condition[:host] }"
+    when 'original-year'
+      "original-year:#{ condition[:year] }"
+    when 'original-month'
+      "original-month:#{ condition[:month] }"
+    when 'original-month-day'
+      "original-month-day:#{ condition[:monthDay] || condition[:month_day] }"
+    when 'title-length-greater-than'
+      "title:length-greater-than:#{ condition[:length] }"
+    when 'title-has-ascii'
+      'title:ascii'
+    else
+      "catalog:#{ question.id }"
+    end
+  end
+
+  def condition_json condition
+    json = condition.deep_dup.as_json
+
+    if json['type'] == 'original-month-day' && json['monthDay'].blank?
+      json['monthDay'] = json.delete('month_day')
+    end
+
+    json
+  end
+end

backend/app/models/gekanator_ai_run.rb

@@ -0,0 +1,21 @@
+class GekanatorAiRun < ApplicationRecord
+  STATUSES = ['pending', 'running', 'succeeded', 'failed', 'blocked_budget'].freeze
+
+  belongs_to :gekanator_question_suggestion
+
+  validates :model, presence: true, length: { maximum: 255 }
+  validates :status, presence: true, inclusion: { in: STATUSES }
+  validates :input_tokens,
+            presence: true,
+            numericality: { only_integer: true, greater_than_or_equal_to: 0 }
+  validates :output_tokens,
+            presence: true,
+            numericality: { only_integer: true, greater_than_or_equal_to: 0 }
+  validates :estimated_cost_jpy,
+            presence: true,
+            numericality: { greater_than_or_equal_to: 0 }
+
+  scope :this_month, lambda {
+    where(created_at: Time.current.beginning_of_month..Time.current.end_of_month)
+  }
+end

backend/app/models/gekanator_game.rb

@@ -0,0 +1,12 @@
+class GekanatorGame < ApplicationRecord
+  belongs_to :user
+  belongs_to :guessed_post, class_name: 'Post'
+  belongs_to :correct_post, class_name: 'Post'
+  has_many :question_suggestions,
+           class_name: 'GekanatorQuestionSuggestion',
+           dependent: :delete_all
+
+  validates :answers, presence: true
+  validates :question_count, numericality: { greater_than_or_equal_to: 0 }
+  validates :won, inclusion: { in: [true, false] }
+end

backend/app/models/gekanator_question.rb

@@ -0,0 +1,22 @@
+class GekanatorQuestion < ApplicationRecord
+  KINDS = ['tag', 'source', 'title', 'original_date'].freeze
+  SOURCES = ['user_suggested', 'ai_generated', 'admin_curated'].freeze
+  STATUSES = ['pending', 'accepted', 'rejected'].freeze
+
+  belongs_to :gekanator_question_suggestion, optional: true
+  belongs_to :created_by, class_name: 'User', optional: true
+
+  validates :kind, presence: true, inclusion: { in: KINDS }
+  validates :source, presence: true, inclusion: { in: SOURCES }
+  validates :status, presence: true, inclusion: { in: STATUSES }
+  validates :text, presence: true, length: { maximum: 1000 }
+  validates :condition, presence: true
+  validates :priority_weight,
+            presence: true,
+            numericality: {
+              greater_than: 0,
+              less_than_or_equal_to: 3
+            }
+
+  scope :accepted, -> { where(status: 'accepted') }
+end

backend/app/models/gekanator_question_suggestion.rb

@@ -0,0 +1,25 @@
+class GekanatorQuestionSuggestion < ApplicationRecord
+  MAX_QUESTIONS_PER_GAME = 3
+  ANSWERS = ['yes', 'no', 'partial', 'probably_no', 'unknown'].freeze
+
+  belongs_to :gekanator_game
+  belongs_to :user
+  has_many :gekanator_questions, dependent: :nullify
+  has_many :gekanator_ai_runs, dependent: :destroy
+
+  validates :question_text, presence: true, length: { maximum: 1000 }
+  validates :answer, presence: true, inclusion: { in: ANSWERS }
+  validates :processed, inclusion: { in: [true, false] }
+  validate :question_suggestion_limit_per_game, on: :create
+
+  private
+
+  def question_suggestion_limit_per_game
+    return if gekanator_game_id.blank?
+
+    count = GekanatorQuestionSuggestion.where(gekanator_game_id:).count
+    if count >= MAX_QUESTIONS_PER_GAME
+      errors.add(:base, '質問追加数を超えてゐます．')
+    end
+  end
+end

backend/app/models/post.rb

@@ -11,6 +11,16 @@ class Post < ApplicationRecord
   has_many :user_post_views, dependent: :delete_all
   has_many :post_similarities, dependent: :delete_all
   has_many :post_versions
+  has_many :gekanator_guessed_games,
+           class_name: 'GekanatorGame',
+           foreign_key: :guessed_post_id,
+           dependent: :delete_all,
+           inverse_of: :guessed_post
+  has_many :gekanator_correct_games,
+           class_name: 'GekanatorGame',
+           foreign_key: :correct_post_id,
+           dependent: :delete_all,
+           inverse_of: :correct_post
 
   has_many :parent_post_implications,
            class_name: 'PostImplication',

backend/app/services/gekanator/ai_run_budget.rb

@@ -0,0 +1,22 @@
+module Gekanator
+  class AiRunBudget
+    MONTHLY_LIMIT_JPY = BigDecimal('450').freeze
+    MAX_RUN_ESTIMATED_COST_JPY = BigDecimal('5').freeze
+
+    def self.remaining_monthly_budget_jpy
+      MONTHLY_LIMIT_JPY - monthly_cost_jpy
+    end
+
+    def self.monthly_cost_jpy
+      GekanatorAiRun.this_month.sum(:estimated_cost_jpy)
+    end
+
+    def self.exceeded?
+      monthly_cost_jpy >= MONTHLY_LIMIT_JPY
+    end
+
+    def self.exceeded_after_next_run?
+      monthly_cost_jpy + MAX_RUN_ESTIMATED_COST_JPY >= MONTHLY_LIMIT_JPY
+    end
+  end
+end

backend/app/services/gekanator/question_suggestion_ai_converter.rb

@@ -0,0 +1,18 @@
+module Gekanator
+  class QuestionSuggestionAiConverter
+    def self.call(...) = new(...).call
+
+    def initialize suggestion:, user:
+      @suggestion = suggestion
+      @user = user
+    end
+
+    def call
+      raise NotImplementedError, 'AI question conversion is not implemented yet.'
+    end
+
+    private
+
+    attr_reader :suggestion, :user
+  end
+end

backend/config/routes.rb

@@ -63,6 +63,19 @@ Rails.application.routes.draw do
     end
   end
 
+  namespace :gekanator do
+    resources :games, only: [:create], controller: '/gekanator_games'
+    resources :posts, only: [:index], controller: '/gekanator_posts'
+    resources :questions, only: [:index], controller: '/gekanator_questions'
+    resources :question_suggestions,
+              only: [:create],
+              controller: '/gekanator_question_suggestions' do
+      member do
+        post :ai_convert
+      end
+    end
+  end
+
   resources :users, only: [:create, :update] do
     collection do
       post :verify

backend/db/migrate/20260607000000_create_gekanator_games.rb

@@ -0,0 +1,18 @@
+class CreateGekanatorGames < ActiveRecord::Migration[8.0]
+  def change
+    create_table :gekanator_games do |t|
+      t.references :user, null: false, foreign_key: true
+      t.references :guessed_post, null: false, foreign_key: { to_table: :posts }
+      t.references :correct_post, null: false, foreign_key: { to_table: :posts }
+      t.boolean :won, null: false
+      t.integer :question_count, null: false
+      t.json :answers, null: false
+
+      t.timestamps
+    end
+
+    add_check_constraint :gekanator_games,
+                         'question_count >= 0',
+                         name: 'chk_gekanator_games_question_count_nonnegative'
+  end
+end

backend/db/migrate/20260608000000_create_gekanator_question_suggestions.rb

@@ -0,0 +1,14 @@
+class CreateGekanatorQuestionSuggestions < ActiveRecord::Migration[8.0]
+  def change
+    create_table :gekanator_question_suggestions do |t|
+      t.references :gekanator_game,
+                   null: false,
+                   foreign_key: { on_delete: :cascade }
+      t.references :user, null: false, foreign_key: true
+      t.text :question_text, null: false
+      t.boolean :processed, null: false, default: false
+
+      t.timestamps
+    end
+  end
+end

backend/db/migrate/20260608002000_add_answer_to_gekanator_question_suggestions.rb

@@ -0,0 +1,5 @@
+class AddAnswerToGekanatorQuestionSuggestions < ActiveRecord::Migration[8.0]
+  def change
+    add_column :gekanator_question_suggestions, :answer, :string, null: false
+  end
+end

backend/db/migrate/20260609000000_create_gekanator_questions.rb

@@ -0,0 +1,19 @@
+class CreateGekanatorQuestions < ActiveRecord::Migration[8.0]
+  def change
+    create_table :gekanator_questions do |t|
+      t.string :text, null: false
+      t.string :kind, null: false
+      t.json :condition, null: false
+      t.string :source, null: false, default: 'ai_generated'
+      t.string :status, null: false, default: 'pending'
+      t.float :priority_weight, null: false, default: 1.0
+      t.references :gekanator_question_suggestion,
+                   null: true,
+                   foreign_key: true
+      t.references :created_by,
+                   null: true,
+                   foreign_key: { to_table: :users }
+      t.timestamps
+    end
+  end
+end

backend/db/migrate/20260609001000_create_gekanator_ai_runs.rb

@@ -0,0 +1,13 @@
+class CreateGekanatorAiRuns < ActiveRecord::Migration[8.0]
+  def change
+    create_table :gekanator_ai_runs do |t|
+      t.string :model, null: false
+      t.integer :input_tokens, null: false, default: 0
+      t.integer :output_tokens, null: false, default: 0
+      t.decimal :estimated_cost_jpy, precision: 8, scale: 3, null: false, default: 0
+      t.string :status, null: false, default: 'pending'
+      t.references :gekanator_question_suggestion, null: false, foreign_key: true
+      t.timestamps
+    end
+  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_06_000000) do
+ActiveRecord::Schema[8.0].define(version: 2026_06_09_001000) 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
@@ -48,6 +48,60 @@ ActiveRecord::Schema[8.0].define(version: 2026_06_06_000000) do
     t.index ["tag_id"], name: "index_deerjikists_on_tag_id"
   end
 
+  create_table "gekanator_ai_runs", charset: "utf8mb4", collation: "utf8mb4_0900_ai_ci", force: :cascade do |t|
+    t.string "model", null: false
+    t.integer "input_tokens", default: 0, null: false
+    t.integer "output_tokens", default: 0, null: false
+    t.decimal "estimated_cost_jpy", precision: 8, scale: 3, default: "0.0", null: false
+    t.string "status", default: "pending", null: false
+    t.bigint "gekanator_question_suggestion_id", null: false
+    t.datetime "created_at", null: false
+    t.datetime "updated_at", null: false
+    t.index ["gekanator_question_suggestion_id"], name: "index_gekanator_ai_runs_on_gekanator_question_suggestion_id"
+  end
+
+  create_table "gekanator_games", charset: "utf8mb4", collation: "utf8mb4_0900_ai_ci", force: :cascade do |t|
+    t.bigint "user_id", null: false
+    t.bigint "guessed_post_id", null: false
+    t.bigint "correct_post_id", null: false
+    t.boolean "won", null: false
+    t.integer "question_count", null: false
+    t.json "answers", null: false
+    t.datetime "created_at", null: false
+    t.datetime "updated_at", null: false
+    t.index ["correct_post_id"], name: "index_gekanator_games_on_correct_post_id"
+    t.index ["guessed_post_id"], name: "index_gekanator_games_on_guessed_post_id"
+    t.index ["user_id"], name: "index_gekanator_games_on_user_id"
+    t.check_constraint "`question_count` >= 0", name: "chk_gekanator_games_question_count_nonnegative"
+  end
+
+  create_table "gekanator_question_suggestions", charset: "utf8mb4", collation: "utf8mb4_0900_ai_ci", force: :cascade do |t|
+    t.bigint "gekanator_game_id", null: false
+    t.bigint "user_id", null: false
+    t.text "question_text", null: false
+    t.boolean "processed", default: false, null: false
+    t.datetime "created_at", null: false
+    t.datetime "updated_at", null: false
+    t.string "answer", null: false
+    t.index ["gekanator_game_id"], name: "index_gekanator_question_suggestions_on_gekanator_game_id"
+    t.index ["user_id"], name: "index_gekanator_question_suggestions_on_user_id"
+  end
+
+  create_table "gekanator_questions", charset: "utf8mb4", collation: "utf8mb4_0900_ai_ci", force: :cascade do |t|
+    t.string "text", null: false
+    t.string "kind", null: false
+    t.json "condition", null: false
+    t.string "source", default: "ai_generated", null: false
+    t.string "status", default: "pending", null: false
+    t.float "priority_weight", default: 1.0, null: false
+    t.bigint "gekanator_question_suggestion_id"
+    t.bigint "created_by_id"
+    t.datetime "created_at", null: false
+    t.datetime "updated_at", null: false
+    t.index ["created_by_id"], name: "index_gekanator_questions_on_created_by_id"
+    t.index ["gekanator_question_suggestion_id"], name: "index_gekanator_questions_on_gekanator_question_suggestion_id"
+  end
+
   create_table "ip_addresses", charset: "utf8mb4", collation: "utf8mb4_0900_ai_ci", force: :cascade do |t|
     t.binary "ip_address", limit: 16, null: false
     t.datetime "banned_at"
@@ -137,6 +191,19 @@ ActiveRecord::Schema[8.0].define(version: 2026_06_06_000000) do
     t.index ["target_post_id"], name: "index_post_similarities_on_target_post_id"
   end
 
+  create_table "post_tag_sections", primary_key: ["post_id", "tag_id", "begin_ms"], charset: "utf8mb4", collation: "utf8mb4_0900_ai_ci", force: :cascade do |t|
+    t.bigint "post_id", null: false
+    t.bigint "tag_id", null: false
+    t.integer "begin_ms", null: false
+    t.integer "end_ms", null: false
+    t.datetime "created_at", null: false
+    t.datetime "updated_at", null: false
+    t.index ["post_id", "begin_ms"], name: "idx_post_tag_sections_post_id_begin_ms"
+    t.index ["tag_id"], name: "fk_rails_8be3847903"
+    t.check_constraint "`begin_ms` < `end_ms`", name: "chk_post_tag_sections_end_ms_after_begin_ms"
+    t.check_constraint "`begin_ms` >= 0", name: "chk_post_tag_sections_begin_ms_natural"
+  end
+
   create_table "post_tags", charset: "utf8mb4", collation: "utf8mb4_0900_ai_ci", force: :cascade do |t|
     t.bigint "post_id", null: false
     t.bigint "tag_id", null: false
@@ -187,8 +254,11 @@ ActiveRecord::Schema[8.0].define(version: 2026_06_06_000000) do
     t.datetime "original_created_before"
     t.datetime "updated_at", null: false
     t.integer "version_no", null: false
+    t.integer "video_ms"
     t.index ["uploaded_user_id"], name: "index_posts_on_uploaded_user_id"
     t.index ["url"], name: "index_posts_on_url", unique: true
+    t.index ["video_ms", "id"], name: "idx_posts_video_ms_id"
+    t.check_constraint "(`video_ms` is null) or (`video_ms` > 0)", name: "chk_posts_video_ms_positive"
     t.check_constraint "`version_no` > 0", name: "chk_posts_version_no_positive"
   end
 
@@ -339,6 +409,7 @@ ActiveRecord::Schema[8.0].define(version: 2026_06_06_000000) do
     t.datetime "created_at", null: false
     t.datetime "updated_at", null: false
     t.index ["expires_at"], name: "index_theatre_watching_users_on_expires_at"
+    t.index ["theatre_id", "expires_at"], name: "idx_on_theatre_id_skip_expires_at_4c8de1dd42"
     t.index ["theatre_id", "expires_at"], name: "index_theatre_watching_users_on_theatre_id_and_expires_at"
     t.index ["theatre_id"], name: "index_theatre_watching_users_on_theatre_id"
     t.index ["user_id"], name: "index_theatre_watching_users_on_user_id"
@@ -478,6 +549,14 @@ ActiveRecord::Schema[8.0].define(version: 2026_06_06_000000) do
 
   add_foreign_key "active_storage_attachments", "active_storage_blobs", column: "blob_id"
   add_foreign_key "active_storage_variant_records", "active_storage_blobs", column: "blob_id"
+  add_foreign_key "gekanator_ai_runs", "gekanator_question_suggestions"
+  add_foreign_key "gekanator_games", "posts", column: "correct_post_id"
+  add_foreign_key "gekanator_games", "posts", column: "guessed_post_id"
+  add_foreign_key "gekanator_games", "users"
+  add_foreign_key "gekanator_question_suggestions", "gekanator_games", on_delete: :cascade
+  add_foreign_key "gekanator_question_suggestions", "users"
+  add_foreign_key "gekanator_questions", "gekanator_question_suggestions"
+  add_foreign_key "gekanator_questions", "users", column: "created_by_id"
   add_foreign_key "material_versions", "materials"
   add_foreign_key "material_versions", "materials", column: "parent_id"
   add_foreign_key "material_versions", "tags"
@@ -495,6 +574,8 @@ ActiveRecord::Schema[8.0].define(version: 2026_06_06_000000) do
   add_foreign_key "post_implications", "posts", column: "parent_post_id"
   add_foreign_key "post_similarities", "posts"
   add_foreign_key "post_similarities", "posts", column: "target_post_id"
+  add_foreign_key "post_tag_sections", "posts"
+  add_foreign_key "post_tag_sections", "tags"
   add_foreign_key "post_tags", "posts"
   add_foreign_key "post_tags", "tags"
   add_foreign_key "post_tags", "users", column: "created_user_id"

backend/spec/requests/gekanator_games_spec.rb

@@ -0,0 +1,75 @@
+require 'rails_helper'
+
+RSpec.describe 'Gekanator games API', type: :request do
+  let!(:admin) { create_admin_user! }
+  let!(:user) { create_member_user! }
+  let!(:guessed_post) { Post.create!(title: 'guess', url: 'https://example.com/guess') }
+  let!(:correct_post) { Post.create!(title: 'correct', url: 'https://example.com/correct') }
+
+  describe 'POST /gekanator/games' do
+    it 'stores a won game' do
+      sign_in_as admin
+
+      post '/gekanator/games', params: {
+          guessed_post_id: guessed_post.id,
+          correct_post_id: guessed_post.id,
+          answers: [{ question_id: 'tag:1', answer: 'yes' }] }
+
+      expect(response).to have_http_status(:created)
+      game = GekanatorGame.find(json['id'])
+      expect(game.user).to eq(admin)
+      expect(game.guessed_post).to eq(guessed_post)
+      expect(game.correct_post).to eq(guessed_post)
+      expect(game.won).to eq(true)
+      expect(game.question_count).to eq(1)
+      expect(game.answers).to eq([{ 'question_id' => 'tag:1', 'answer' => 'yes' }])
+    end
+
+    it 'stores a lost game with the correct post' do
+      sign_in_as admin
+
+      post '/gekanator/games', params: {
+          guessed_post_id: guessed_post.id,
+          correct_post_id: correct_post.id,
+          question_count: 4,
+          answers: [{ question_id: 'tag:1', answer: 'no' }] }
+
+      expect(response).to have_http_status(:created)
+      game = GekanatorGame.find(json['id'])
+      expect(game.correct_post).to eq(correct_post)
+      expect(game.won).to eq(false)
+      expect(game.question_count).to eq(1)
+    end
+
+    it 'rejects a game without the correct post' do
+      sign_in_as admin
+
+      post '/gekanator/games', params: {
+          guessed_post_id: guessed_post.id,
+          question_count: 4,
+          answers: [{ question_id: 'tag:1', answer: 'no' }] }
+
+      expect(response).to have_http_status(:unprocessable_entity)
+    end
+
+    it 'returns not found without an admin user' do
+      post '/gekanator/games', params: {
+          guessed_post_id: guessed_post.id,
+          correct_post_id: guessed_post.id,
+          answers: [] }
+
+      expect(response).to have_http_status(:not_found)
+    end
+
+    it 'returns not found for a non-admin user' do
+      sign_in_as user
+
+      post '/gekanator/games', params: {
+          guessed_post_id: guessed_post.id,
+          correct_post_id: guessed_post.id,
+          answers: [{ question_id: 'tag:1', answer: 'yes' }] }
+
+      expect(response).to have_http_status(:not_found)
+    end
+  end
+end

frontend/AGENTS.md

@@ -33,6 +33,10 @@ npm run lint
 
 If either command cannot be run or fails, report the exact command and failure.
 
+Do not create, modify, or run tests unless the user explicitly asks for test
+work. When the user asks for tests, keep working and rerun them until they
+pass or the remaining failure is clearly blocked.
+
 ## TypeScript
 
 - TypeScript is strict. `tsconfig.app.json` enables `strict`,

frontend/src/App.tsx

@@ -18,6 +18,7 @@ import MaterialListPage from '@/pages/materials/MaterialListPage'
 import MaterialNewPage from '@/pages/materials/MaterialNewPage'
 // import MaterialSearchPage from '@/pages/materials/MaterialSearchPage'
 import MorePage from '@/pages/MorePage'
+import GekanatorPage from '@/pages/GekanatorPage'
 import NicoTagListPage from '@/pages/tags/NicoTagListPage'
 import NotFound from '@/pages/NotFound'
 import TOSPage from '@/pages/TOSPage.mdx'
@@ -39,7 +40,7 @@ import WikiHistoryPage from '@/pages/wiki/WikiHistoryPage'
 import WikiNewPage from '@/pages/wiki/WikiNewPage'
 import WikiSearchPage from '@/pages/wiki/WikiSearchPage'
 
-import type { Dispatch, FC, SetStateAction } from 'react'
+import type { Dispatch, FC, ReactNode, SetStateAction } from 'react'
 
 import type { User } from '@/types'
 
@@ -80,6 +81,10 @@ const RouteTransitionWrapper = ({ user, setUser }: {
 	  <Route path="/users/settings" element={<SettingPage user={user} setUser={setUser}/>}/>
 	  <Route path="/settings" element={<Navigate to="/users/settings" replace/>}/>
 	  <Route path="/tos" element={<TOSPage/>}/>
+	  <Route path="/gekanator" element={
+	      <AdminOnly user={user}>
+		<GekanatorPage/>
+	      </AdminOnly>}/>
 	  <Route path="/more" element={<MorePage/>}/>
 	  <Route path="*" element={<NotFound/>}/>
 	</Routes>
@@ -87,6 +92,16 @@ const RouteTransitionWrapper = ({ user, setUser }: {
 }
 
 
+const AdminOnly = ({ user, children }: {
+    user:      User | null
+    children:  ReactNode }) => {
+  if (user?.role !== 'admin')
+    return <NotFound/>
+
+  return <>{children}</>
+}
+
+
 const PostDetailRoute = ({ user }: { user: User | null }) => {
   const location = useLocation ()
   const key = location.pathname

frontend/src/lib/gekanator.ts

@@ -0,0 +1,395 @@
+import { apiGet, apiPost } from '@/lib/api'
+
+import type { Post } from '@/types'
+
+export type GekanatorAnswerValue =
+    | 'yes'
+    | 'no'
+    | 'partial'
+    | 'probably_no'
+    | 'unknown'
+
+export type GekanatorAnswerLog = {
+    questionId:       string
+    questionText:     string
+    questionCondition?:  GekanatorQuestionCondition
+    answer:           GekanatorAnswerValue
+    originalAnswer:   GekanatorAnswerValue }
+
+export type GekanatorQuestionKind =
+    | 'tag'
+    | 'source'
+    | 'title'
+    | 'original_date'
+
+export type GekanatorQuestionSource =
+    | 'default'
+    | 'user_suggested'
+    | 'ai_generated'
+    | 'admin_curated'
+
+export type GekanatorQuestionCondition =
+    | { type: 'tag'; key: string }
+    | { type: 'source'; host: string }
+    | { type: 'original-year'; year: number }
+    | { type: 'original-month'; month: number }
+    | { type: 'original-month-day'; monthDay: string }
+    | { type: 'title-length-greater-than'; length: number }
+    | { type: 'title-has-ascii' }
+
+export type StoredGekanatorQuestion = {
+    id:              string
+    text:            string
+    kind:            GekanatorQuestionKind
+    condition:       GekanatorQuestionCondition
+    source?:         GekanatorQuestionSource
+    priorityWeight?: number }
+
+export type GekanatorQuestion = {
+    id:              string
+    text:            string
+    kind:            GekanatorQuestionKind
+    condition:       GekanatorQuestionCondition
+    source:          GekanatorQuestionSource
+    priorityWeight:  number
+    test:            (post: Post) => boolean }
+
+const countBy = <T extends string | number> (values: T[]): Map<T, number> => {
+  const counts = new Map<T, number> ()
+  values.forEach (value => counts.set (value, (counts.get (value) ?? 0) + 1))
+  return counts
+}
+
+
+const median = (values: number[]): number => {
+  const sorted = [...values].sort ((a, b) => a - b)
+  return sorted[Math.floor (sorted.length / 2)] ?? 0
+}
+
+
+const hostOf = (post: Post): string | null => {
+  try
+  {
+    return new URL (post.url).hostname.replace (/^www\./, '')
+  }
+  catch
+  {
+    return null
+  }
+}
+
+
+const originalYearOf = (post: Post): number | null => {
+  const value = post.originalCreatedFrom || post.originalCreatedBefore
+  if (!(value))
+    return null
+
+  const date = new Date (value)
+  if (Number.isNaN (date.getTime ()))
+    return null
+
+  return date.getFullYear ()
+}
+
+
+const originalDateOf = (post: Post): Date | null => {
+  const value = post.originalCreatedFrom || post.originalCreatedBefore
+  if (!(value))
+    return null
+
+  const date = new Date (value)
+  if (Number.isNaN (date.getTime ()))
+    return null
+
+  return date
+}
+
+
+const originalMonthOf = (post: Post): number | null => {
+  const date = originalDateOf (post)
+  if (!(date))
+    return null
+
+  return date.getMonth () + 1
+}
+
+
+const originalMonthDayOf = (post: Post): string | null => {
+  const date = originalDateOf (post)
+  if (!(date))
+    return null
+
+  return `${ date.getMonth () + 1 }-${ date.getDate () }`
+}
+
+
+const tagQuestionKey = ({ category, name }: { category: string; name: string }): string =>
+    `${ category }:${ name }`
+
+
+const tagFromQuestionKey = (key: string): { category: string; name: string } => {
+  const [category, ...rest] = key.split (':')
+  return { category: category ?? '', name: rest.join (':') }
+}
+
+
+const nicoTagLabel = (name: string): string => name.replace (/^nico:/, '')
+
+
+const tagQuestionText = (category: string, label: string): string => {
+  switch (category)
+  {
+  case 'deerjikist':
+    return `作者・ニジラーとして「${ label }」に関係してゐる?`
+  case 'meme':
+    return `元ネタ・ミームとして「${ label }」に関係しさう?`
+  case 'character':
+    return `「${ label }」といふキャラクターが関係してゐる?`
+  case 'material':
+    return `素材として「${ label }」に関係してゐる?`
+  case 'nico':
+    return `ニコニコに「${ label }」といふタグが付いてゐる?`
+  case 'general':
+  case 'meta':
+  default:
+    return `内容として「${ label }」に関係しさう?`
+  }
+}
+
+
+const questionableTag = (post: Post, key: string): boolean => {
+  const { category, name } = tagFromQuestionKey (key)
+
+  return (
+    post.tags.some (tag =>
+	tag.name === name
+	&& tag.category === category
+	&& !(tag.category === 'meta')
+	&& !(tag.name.includes ('タグ希望'))
+	&& !(tag.name.includes ('bot操作'))))
+}
+
+
+const questionMatches = (
+    post:       Post,
+    condition:  GekanatorQuestionCondition,
+): boolean => {
+  switch (condition.type)
+  {
+  case 'tag':
+    return questionableTag (post, condition.key)
+  case 'source':
+    return hostOf (post) === condition.host
+  case 'original-year':
+    return originalYearOf (post) === condition.year
+  case 'original-month':
+    return originalMonthOf (post) === condition.month
+  case 'original-month-day':
+    return originalMonthDayOf (post) === condition.monthDay
+  case 'title-length-greater-than':
+    return (post.title?.length ?? 0) > condition.length
+  case 'title-has-ascii':
+    return /[A-Za-z0-9]/.test (post.title ?? '')
+  }
+}
+
+
+export const restoreGekanatorQuestion = (
+    question:  StoredGekanatorQuestion,
+): GekanatorQuestion => ({
+  ...question,
+  source: question.source ?? 'default',
+  priorityWeight: question.priorityWeight ?? 1,
+  test: (post: Post) => questionMatches (post, question.condition) })
+
+
+export const storeGekanatorQuestion = (
+    question:  GekanatorQuestion,
+): StoredGekanatorQuestion => ({
+  id: question.id,
+  text: question.text,
+  kind: question.kind,
+  condition: question.condition,
+  source: question.source,
+  priorityWeight: question.priorityWeight })
+
+
+export const fetchGekanatorPosts = async (): Promise<Post[]> => {
+  const data = await apiGet<{ posts: Post[] }> ('/gekanator/posts')
+  return data.posts
+}
+
+
+export const fetchGekanatorQuestions = async (): Promise<StoredGekanatorQuestion[]> => {
+  const data = await apiGet<{ questions: StoredGekanatorQuestion[] }> ('/gekanator/questions')
+  return data.questions
+}
+
+
+export const buildGekanatorQuestions = (posts: Post[]): GekanatorQuestion[] => {
+  const tagCounts = countBy (posts.flatMap (post =>
+      post.tags
+      .filter (tag =>
+	  !(tag.category === 'meta')
+	  && !(tag.name.includes ('タグ希望'))
+	  && !(tag.name.includes ('bot操作')))
+      .map (tag => tagQuestionKey (tag))))
+  const hosts = countBy (posts.map (hostOf).filter ((host): host is string => Boolean (host)))
+  const originalYears = countBy (
+      posts
+      .map (originalYearOf)
+      .filter ((year): year is number => year !== null))
+  const originalMonths = countBy (
+      posts
+      .map (originalMonthOf)
+      .filter ((month): month is number => month !== null))
+  const originalMonthDays = countBy (
+      posts
+      .map (originalMonthDayOf)
+      .filter ((monthDay): monthDay is string => monthDay !== null))
+  const titleLengthMedian = median (posts.map (post => post.title?.length ?? 0))
+
+  const usefulEntries = <T extends string | number> (counts: Map<T, number>) =>
+      [...counts.entries ()]
+      .filter (([, count]) => count > 0 && count < posts.length)
+      .sort ((a, b) => Math.abs (posts.length / 2 - a[1])
+	       - Math.abs (posts.length / 2 - b[1]))
+      .slice (0, 80)
+
+  const tagQuestions = usefulEntries (tagCounts)
+      .filter (([, count]) => count >= 2 && count <= Math.max (2, posts.length * .7))
+      .slice (0, 80)
+      .map (([key]) => {
+	const { category, name } = tagFromQuestionKey (String (key))
+	const label = category === 'nico' ? nicoTagLabel (name) : name
+
+	return {
+	    id:   `tag:${ key }`,
+	    text: tagQuestionText (category, label),
+	    kind: 'tag' as const,
+	    condition: { type: 'tag' as const, key: String (key) },
+	    source: 'default' as const,
+	    priorityWeight: 1,
+	    test: (post: Post) => questionableTag (post, String (key)) }
+      })
+
+  const sourceQuestions = usefulEntries (hosts)
+      .filter (([, count]) => count >= 2 && count <= Math.max (2, posts.length * .7))
+      .slice (0, 20)
+      .map (([host]) => ({
+	  id:   `source:${ host }`,
+	  text: `${ host } の投稿を思ひ浮かべてゐる?`,
+	  kind: 'source' as const,
+	  condition: { type: 'source' as const, host },
+	  source: 'default' as const,
+	  priorityWeight: 1,
+	  test: (post: Post) => hostOf (post) === host }))
+
+  const originalYearQuestions = usefulEntries (originalYears)
+      .filter (([, count]) => count >= 2 && count <= Math.max (2, posts.length * .7))
+      .slice (0, 20)
+      .map (([year]) => ({
+	  id:   `original-year:${ year }`,
+	  text: `オリジナルの投稿年は ${ year } 年?`,
+	  kind: 'original_date' as const,
+	  condition: { type: 'original-year' as const, year },
+	  source: 'default' as const,
+	  priorityWeight: 1,
+	  test: (post: Post) => originalYearOf (post) === year }))
+
+  const originalMonthQuestions = usefulEntries (originalMonths)
+      .filter (([, count]) => count >= 2 && count <= Math.max (2, posts.length * .7))
+      .slice (0, 20)
+      .map (([month]) => ({
+	  id:   `original-month:${ month }`,
+	  text: `オリジナルの投稿月は ${ month } 月?`,
+	  kind: 'original_date' as const,
+	  condition: { type: 'original-month' as const, month },
+	  source: 'default' as const,
+	  priorityWeight: 1,
+	  test: (post: Post) => originalMonthOf (post) === month }))
+
+  const originalMonthDayQuestions = usefulEntries (originalMonthDays)
+      .filter (([, count]) => count >= 2 && count <= Math.max (2, posts.length * .7))
+      .slice (0, 20)
+      .map (([monthDay]) => {
+	const [month, day] = String (monthDay).split ('-')
+
+	return {
+	    id:   `original-month-day:${ monthDay }`,
+	    text: `オリジナルの投稿日は ${ month } 月 ${ day } 日?`,
+	    kind: 'original_date' as const,
+	    condition: { type: 'original-month-day' as const, monthDay: String (monthDay) },
+	    source: 'default' as const,
+	    priorityWeight: 1,
+	    test: (post: Post) => originalMonthDayOf (post) === monthDay }
+      })
+
+  const titleQuestions = [
+      {
+	  id:   'title:long',
+	  text: '題名が長めの投稿?',
+	  kind: 'title' as const,
+	  condition: {
+	      type: 'title-length-greater-than' as const,
+	      length: titleLengthMedian },
+	  source: 'default' as const,
+	  priorityWeight: 1,
+	  test: (post: Post) => (post.title?.length ?? 0) > titleLengthMedian },
+      {
+	  id:   'title:ascii',
+	  text: '題名に英数字が混じってゐる?',
+	  kind: 'title' as const,
+	  condition: { type: 'title-has-ascii' as const },
+	  source: 'default' as const,
+	  priorityWeight: 1,
+	  test: (post: Post) => /[A-Za-z0-9]/.test (post.title ?? '') }]
+      .filter (question => {
+	const yes = posts.filter (post => question.test (post)).length
+	const no = posts.length - yes
+	return yes >= 2 && no >= 2 && yes <= posts.length * .7 && no <= posts.length * .7
+      })
+
+  return [
+      ...sourceQuestions,
+      ...originalYearQuestions,
+      ...originalMonthQuestions,
+      ...originalMonthDayQuestions,
+      ...titleQuestions,
+      ...tagQuestions]
+}
+
+
+export const saveGekanatorGame = async ({
+    guessedPostId,
+    correctPostId,
+    answers,
+}: {
+    guessedPostId:  number
+    correctPostId:  number
+    answers:        GekanatorAnswerLog[]
+}): Promise<{ id: number }> =>
+    await apiPost ('/gekanator/games', {
+	guessed_post_id: guessedPostId,
+	correct_post_id: correctPostId,
+	answers: answers.map (answer => ({
+	    question_id: answer.questionId,
+	    question_text: answer.questionText,
+	    question_condition: answer.questionCondition ?? null,
+	    answer: answer.answer,
+	    original_answer: answer.originalAnswer })) })
+
+
+export const saveGekanatorQuestionSuggestion = async ({
+    gekanatorGameId,
+    questionText,
+    answer,
+}: {
+    gekanatorGameId:  number
+    questionText:     string
+    answer:           GekanatorAnswerValue
+}): Promise<{ id: number; count: number }> =>
+    await apiPost ('/gekanator/question_suggestions', {
+	gekanator_game_id: gekanatorGameId,
+	question_text: questionText,
+	answer })

frontend/src/lib/queryKeys.ts

@@ -8,6 +8,11 @@ export const postsKeys = {
     changes:  (p: { post?: string; tag?: string; page: number; limit: number }) =>
 		  ['posts', 'changes', p] as const }
 
+export const gekanatorKeys = {
+    root:      ['gekanator'] as const,
+    posts:     () => ['gekanator', 'posts'] as const,
+    questions: () => ['gekanator', 'questions'] as const }
+
 export const tagsKeys = {
     root:         ['tags'] as const,
     index:        (p: FetchTagsParams) => ['tags', 'index', p] as const,