#41 ウィニング・ラン修正

Reviewed-on: #365
Co-authored-by: miteruzo <miteruzo@naver.com>
Co-committed-by: miteruzo <miteruzo@naver.com>

backend/app/controllers/gekanator_games_controller.rb

@@ -27,26 +27,20 @@ class GekanatorGamesController < ApplicationController
     game = GekanatorGame.find_by(id: params[:id])
     return head :not_found unless game
 
-    asked_ids = Array(game.answers).filter_map { |answer| answer_question_id(answer) }
-    existing_example_ids =
-        GekanatorQuestionExample.where(post_id: game.correct_post_id)
-                                .select(:gekanator_question_id)
-    # Direct examples only for now; post_similarity-based expansion is deferred.
     questions =
         GekanatorQuestion
         .accepted
+        .includes(:gekanator_question_examples)
         .where(kind: 'post_similarity', source: 'user_suggested')
-        .where.not(id: existing_example_ids)
+        .to_a
-        .order(priority_weight: :desc, id: :asc)
+
+    selected = weighted_sample_questions(
+        questions,
+        post_id: game.correct_post_id,
+        limit: 2)
 
     render json: {
-      questions: questions.filter_map { |question|
+      questions: selected.map { |question| extra_question_json(question) }
-        json = extra_question_json(question)
-        next if asked_ids.include?(json[:id].to_s)
-        next if asked_ids.include?("post-similarity:#{ json[:id] }")
-
-        json
-      }.first(2)
     }
   end
 
@@ -84,11 +78,10 @@ class GekanatorGamesController < ApplicationController
                 gekanator_question: question,
                 post: game.correct_post,
                 user: current_user)
-        example.assign_attributes(
+        example.record_answer!(
-            gekanator_game: game,
             answer: item[:answer],
             source: 'post_game_extra',
-            weight: 1.0)
+            gekanator_game: game)
         example.save!
       end
     end
@@ -107,12 +100,41 @@ class GekanatorGamesController < ApplicationController
     }
   end
 
-  def answer_question_id answer
+  def weighted_sample_questions questions, post_id:, limit:
-    value = if answer.is_a?(Hash)
+    remaining = questions.uniq(&:id)
-      answer['question_id'].presence || answer[:question_id].presence ||
+    selected = []
-        answer['questionId'].presence || answer[:questionId].presence
+
+    while selected.length < limit && remaining.any?
+      weighted =
+          remaining.map { |question|
+            [question, selection_weight_for(question, post_id: post_id)]
+          }
+      total_weight = weighted.sum { |_question, weight| weight }
+      break if total_weight <= 0
+
+      target = rand * total_weight
+      cumulative = 0.0
+      chosen =
+          weighted.find do |_question, weight|
+            cumulative += weight
+            cumulative >= target
+          end&.first || weighted.first.first
+
+      selected << chosen
+      remaining.reject! { |question| question.id == chosen.id }
     end
 
-    value&.to_s
+    selected
+  end
+
+  def selection_weight_for question, post_id:
+    sample_count =
+        question.gekanator_question_examples.sum { |example|
+          next 0 unless example.post_id == post_id
+
+          example.sample_count.presence || 1
+        }
+
+    question.priority_weight.to_f / (1.0 + sample_count * 0.15)
   end
 end

backend/app/models/gekanator_question_example.rb

@@ -1,5 +1,6 @@
 class GekanatorQuestionExample < ApplicationRecord
   ANSWERS = GekanatorQuestionSuggestion::ANSWERS
+  NON_UNKNOWN_ANSWERS = ANSWERS - ['unknown']
   SOURCES = ['initial_suggestion', 'post_game_extra'].freeze
 
   belongs_to :gekanator_question
@@ -8,10 +9,89 @@ class GekanatorQuestionExample < ApplicationRecord
   belongs_to :gekanator_game, optional: true
 
   validates :answer, presence: true, inclusion: { in: ANSWERS }
+  validates :answer_counts, presence: true
+  validates :sample_count,
+            presence: true,
+            numericality: {
+              only_integer: true,
+              greater_than: 0
+            }
   validates :source, presence: true, inclusion: { in: SOURCES }
   validates :weight,
             presence: true,
             numericality: {
               greater_than: 0
             }
+
+  before_validation :normalize_learning_state
+
+  def record_answer!(answer:, source:, gekanator_game: nil)
+    answer = answer.to_s
+    raise ArgumentError, 'invalid answer' unless ANSWERS.include?(answer)
+
+    counts = normalized_answer_counts
+    counts[answer] += 1
+
+    self.answer_counts = counts
+    self.sample_count = counts.values.sum
+    self.gekanator_game = gekanator_game if gekanator_game.present?
+    self.source = source if new_record?
+
+    apply_aggregated_answer!(preferred_answer: answer)
+    self
+  end
+
+  private
+
+  def normalize_learning_state
+    counts = normalized_answer_counts
+
+    if counts.values.sum.zero? && answer.present?
+      counts[answer] = 1
+    end
+
+    self.answer_counts = counts
+    self.sample_count = counts.values.sum
+
+    apply_aggregated_answer!
+  end
+
+  def apply_aggregated_answer!(preferred_answer: nil)
+    counts = normalized_answer_counts
+    known_counts = counts.slice(*NON_UNKNOWN_ANSWERS)
+    known_total = known_counts.values.sum
+
+    if known_total.zero?
+      self.answer = 'unknown'
+      self.weight = 0.1
+      return
+    else
+      max_count = known_counts.values.max
+      candidates = known_counts.select { |_answer, count| count == max_count }.keys
+      self.answer =
+          if preferred_answer.present? && candidates.include?(preferred_answer)
+            preferred_answer
+          elsif answer.present? && candidates.include?(answer)
+            answer
+          else
+            candidates.first
+          end
+    end
+
+    consensus = max_count.to_f / known_total
+    self.weight = Math.sqrt(known_total) * consensus
+  end
+
+  def normalized_answer_counts
+    base = ANSWERS.index_with(0)
+
+    answer_counts.to_h.each do |key, value|
+      answer_key = key.to_s
+      next unless ANSWERS.include?(answer_key)
+
+      base[answer_key] = value.to_i
+    end
+
+    base
+  end
 end

backend/app/services/gekanator/question_suggestion_promoter.rb

@@ -26,13 +26,16 @@ module Gekanator
             },
             gekanator_question_suggestion: suggestion,
             created_by: user)
-        GekanatorQuestionExample.create!(
+        example =
-            gekanator_question: question,
+            GekanatorQuestionExample.new(
-            post: suggestion.gekanator_game.correct_post,
+                gekanator_question: question,
-            user: user,
+                post: suggestion.gekanator_game.correct_post,
-            gekanator_game: suggestion.gekanator_game,
+                user: user)
+        example.record_answer!(
             answer: suggestion.answer,
-            source: 'initial_suggestion')
+            source: 'initial_suggestion',
+            gekanator_game: suggestion.gekanator_game)
+        example.save!
         suggestion.update!(processed: true)
         question
       end

backend/db/migrate/20260612000000_add_answer_statistics_to_gekanator_question_examples.rb

@@ -0,0 +1,40 @@
+class AddAnswerStatisticsToGekanatorQuestionExamples < ActiveRecord::Migration[8.0]
+  class MigrationGekanatorQuestionExample < ApplicationRecord
+    self.table_name = 'gekanator_question_examples'
+  end
+
+  def up
+    add_column :gekanator_question_examples,
+               :answer_counts,
+               :json,
+               null: true
+    add_column :gekanator_question_examples,
+               :sample_count,
+               :integer,
+               null: false,
+               default: 1
+
+    MigrationGekanatorQuestionExample.reset_column_information
+    MigrationGekanatorQuestionExample.find_each do |example|
+      counts = {
+        'yes' => 0,
+        'no' => 0,
+        'partial' => 0,
+        'probably_no' => 0,
+        'unknown' => 0
+      }
+      counts[example.answer] = 1 if counts.key?(example.answer)
+
+      example.update_columns(
+        answer_counts: counts,
+        sample_count: 1)
+    end
+
+    change_column_null :gekanator_question_examples, :answer_counts, false
+  end
+
+  def down
+    remove_column :gekanator_question_examples, :sample_count
+    remove_column :gekanator_question_examples, :answer_counts
+  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_10_000000) do
+ActiveRecord::Schema[8.0].define(version: 2026_06_12_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
@@ -85,6 +85,8 @@ ActiveRecord::Schema[8.0].define(version: 2026_06_10_000000) do
     t.float "weight", default: 1.0, null: false
     t.datetime "created_at", null: false
     t.datetime "updated_at", null: false
+    t.json "answer_counts", null: false
+    t.integer "sample_count", default: 1, null: false
     t.index ["gekanator_game_id"], name: "index_gekanator_question_examples_on_gekanator_game_id"
     t.index ["gekanator_question_id", "post_id", "user_id"], name: "idx_gekanator_question_examples_on_question_post_user", unique: true
     t.index ["gekanator_question_id"], name: "index_gekanator_question_examples_on_gekanator_question_id"

backend/spec/requests/gekanator_learning_spec.rb

@@ -275,7 +275,7 @@ RSpec.describe 'Gekanator learning API', type: :request do
   end
 
   describe 'GET /gekanator/games/:id/extra_questions' do
-    it 'returns at most two accepted user_suggested post_similarity questions' do
+    it 'returns at most two accepted user_suggested post_similarity questions without duplicates' do
       sign_in_as admin
 
       low = create_post_similarity_question!(
@@ -295,15 +295,14 @@ RSpec.describe 'Gekanator learning API', type: :request do
 
       expect(response).to have_http_status(:ok)
       expect(json['questions'].length).to eq(2)
-      expect(json['questions'].map { _1['id'] }).to eq([high.id, middle.id])
+      expect(json['questions'].map { _1['id'] }.uniq.length).to eq(2)
-      expect(json['questions'].map { _1['id'] }).not_to include(low.id)
+      expect(json['questions'].map { _1['id'] }).to all(be_in([low.id, high.id, middle.id]))
     end
 
-    it 'does not return questions that already have an example for the correct post' do
+    it 'can return questions that already have an example for the correct post' do
       sign_in_as admin
 
       existing = create_post_similarity_question!(text: 'already learned?')
-      fresh = create_post_similarity_question!(text: 'fresh?')
 
       GekanatorQuestionExample.create!(
         gekanator_question: existing,
@@ -317,15 +316,13 @@ RSpec.describe 'Gekanator learning API', type: :request do
       get "/gekanator/games/#{game.id}/extra_questions"
 
       expect(response).to have_http_status(:ok)
-      expect(json['questions'].map { _1['id'] }).to include(fresh.id)
+      expect(json['questions'].map { _1['id'] }).to include(existing.id)
-      expect(json['questions'].map { _1['id'] }).not_to include(existing.id)
     end
 
-    it 'does not return questions already asked in the game using snake_case question_id' do
+    it 'can return questions already asked in the game using snake_case question_id' do
       sign_in_as admin
 
       asked = create_post_similarity_question!(text: 'already asked?')
-      fresh = create_post_similarity_question!(text: 'fresh?')
       game.update!(
         answers: [
           {
@@ -338,15 +335,13 @@ RSpec.describe 'Gekanator learning API', type: :request do
       get "/gekanator/games/#{game.id}/extra_questions"
 
       expect(response).to have_http_status(:ok)
-      expect(json['questions'].map { _1['id'] }).to include(fresh.id)
+      expect(json['questions'].map { _1['id'] }).to include(asked.id)
-      expect(json['questions'].map { _1['id'] }).not_to include(asked.id)
     end
 
-    it 'does not return questions already asked in the game using camelCase questionId' do
+    it 'can return questions already asked in the game using camelCase questionId' do
       sign_in_as admin
 
       asked = create_post_similarity_question!(text: 'already asked?')
-      fresh = create_post_similarity_question!(text: 'fresh?')
       game.update!(
         answers: [
           {
@@ -359,8 +354,7 @@ RSpec.describe 'Gekanator learning API', type: :request do
       get "/gekanator/games/#{game.id}/extra_questions"
 
       expect(response).to have_http_status(:ok)
-      expect(json['questions'].map { _1['id'] }).to include(fresh.id)
+      expect(json['questions'].map { _1['id'] }).to include(asked.id)
-      expect(json['questions'].map { _1['id'] }).not_to include(asked.id)
     end
 
     it 'does not return non-accepted, non-user_suggested, or non-post_similarity questions' do
@@ -584,5 +578,35 @@ RSpec.describe 'Gekanator learning API', type: :request do
         other_post.id.to_s => 'no'
       )
     end
+
+    it 'normalizes legacy title length questions' do
+      sign_in_as admin
+
+      GekanatorQuestion.create!(
+        text: '題名が長めの投稿?',
+        kind: 'title',
+        source: 'admin_curated',
+        status: 'accepted',
+        priority_weight: 1.0,
+        condition: {
+          type: 'title-length-greater-than',
+          length: 20
+        },
+        created_by: admin
+      )
+
+      get '/gekanator/questions'
+
+      expect(response).to have_http_status(:ok)
+      question_json = json['questions'].find { _1['id'] == 'title:length-at-least:21' }
+      expect(question_json).to include(
+        'text' => 'タイトルは 21 文字以上?',
+        'kind' => 'title'
+      )
+      expect(question_json['condition']).to include(
+        'type' => 'title-length-at-least',
+        'length' => 21
+      )
+    end
   end
 end

frontend/src/lib/gekanator.test.ts

@@ -2,6 +2,7 @@ import { beforeEach, describe, expect, it, vi } from 'vitest'
 
 import { apiPost } from '@/lib/api'
 import {
+  buildGekanatorQuestions,
   expectedAnswerForQuestion,
   restoreGekanatorQuestion,
   saveGekanatorExtraQuestionAnswers,
@@ -146,6 +147,23 @@ describe('expectedAnswerForQuestion', () => {
 
     expect(expectedAnswerForQuestion(question, post({ tags: [] }))).toBe('no')
   })
+
+  it('ignores example answers for direct title facts', () => {
+    const question: StoredGekanatorQuestion = {
+      id: 'title:length-at-least:20',
+      text: 'タイトルは 20 文字以上?',
+      kind: 'title',
+      condition: {
+        type: 'title-length-at-least',
+        length: 20,
+      },
+      exampleAnswers: {
+        1: 'yes',
+      },
+    }
+
+    expect(expectedAnswerForQuestion(question, post({ id: 1, title: 'short' }))).toBe('no')
+  })
 })
 
 describe('restoreGekanatorQuestion', () => {
@@ -187,6 +205,65 @@ describe('restoreGekanatorQuestion', () => {
     expect(question.test(post({ id: 2 }))).toBe(false)
     expect(question.test(post({ id: 3 }))).toBe(false)
   })
+
+  it('tests a post_similarity question against its configured partial answer', () => {
+    const question = restoreGekanatorQuestion({
+      id: 'post-similarity:10',
+      text: '喜多ちゃんが泣いてる?',
+      kind: 'post_similarity',
+      source: 'user_suggested',
+      priorityWeight: 1.2,
+      condition: {
+        type: 'post-similarity',
+        postId: 999,
+        answer: 'partial',
+        threshold: 0.65,
+      },
+      exampleAnswers: {
+        1: 'partial',
+        2: 'yes',
+      },
+    })
+
+    expect(question.test(post({ id: 1 }))).toBe(true)
+    expect(question.test(post({ id: 2 }))).toBe(false)
+  })
+
+  it('normalizes legacy title-length-greater-than questions', () => {
+    const question = restoreGekanatorQuestion({
+      id: 'title:length-greater-than:20',
+      text: '題名が長めの投稿?',
+      kind: 'title',
+      condition: {
+        type: 'title-length-greater-than',
+        length: 20,
+      },
+    })
+
+    expect(question.id).toBe('title:length-at-least:21')
+    expect(question.condition).toEqual({
+      type: 'title-length-at-least',
+      length: 21,
+    })
+    expect(question.test(post({ title: 'x'.repeat(20) }))).toBe(false)
+    expect(question.test(post({ title: 'x'.repeat(21) }))).toBe(true)
+  })
+})
+
+describe('buildGekanatorQuestions', () => {
+  it('builds quantitative title length questions', () => {
+    const questions = buildGekanatorQuestions([
+      post({ id: 1, title: 'a' }),
+      post({ id: 2, title: 'bb' }),
+      post({ id: 3, title: 'ccc' }),
+      post({ id: 4, title: 'dddd' }),
+    ])
+    const titleQuestion = questions.find(question =>
+      question.condition.type === 'title-length-at-least')
+
+    expect(titleQuestion?.text).toMatch(/^タイトルは \d+ 文字以上\?$/)
+    expect(titleQuestion?.id).toMatch(/^title:length-at-least:\d+$/)
+  })
 })
 
 describe('Gekanator API writers', () => {

frontend/src/lib/gekanator.ts

@@ -372,10 +372,12 @@ export const fetchGekanatorQuestions = async (): Promise<StoredGekanatorQuestion
 
 
 export const fetchGekanatorExtraQuestions = async (
-    gameId: number,
+    gameId:  number,
+    nonce?: string,
 ): Promise<GekanatorExtraQuestion[]> => {
   const data = await apiGet<{ questions: GekanatorExtraQuestion[] }> (
-      `/gekanator/games/${ gameId }/extra_questions`)
+      `/gekanator/games/${ gameId }/extra_questions`,
+      { params: nonce ? { nonce } : undefined })
   return data.questions
 }
 

frontend/src/lib/gekanatorCandidateRecovery.test.ts

@@ -0,0 +1,151 @@
+import { describe, expect, it } from 'vitest'
+
+import {
+    candidatePostsFor,
+    hardFilteredPostsForAnswer,
+    recoverCandidatePosts,
+} from '@/lib/gekanatorCandidateRecovery'
+
+import type {
+    GekanatorAnswerLog,
+    GekanatorAnswerValue,
+    GekanatorQuestion,
+} from '@/lib/gekanator'
+import type { Post } from '@/types'
+
+
+const post = (id: number): Post => ({
+  id,
+  versionNo: 1,
+  url: `https://example.com/posts/${ id }`,
+  title: `post ${ id }`,
+  thumbnail: null,
+  thumbnailBase: null,
+  tags: [],
+  viewed: false,
+  related: [],
+  originalCreatedFrom: null,
+  originalCreatedBefore: null,
+  createdAt: '2026-06-10T00:00:00.000Z',
+  updatedAt: '2026-06-10T00:00:00.000Z',
+  uploadedUser: null,
+})
+
+
+const postSimilarityQuestion = (
+    id:       string,
+    answers:  Record<`${ number }`, GekanatorAnswerValue>,
+): GekanatorQuestion => ({
+  id,
+  text: `${ id }?`,
+  kind: 'post_similarity',
+  condition: {
+      type: 'post-similarity',
+      postId: 9999,
+      answer: 'yes',
+      threshold: 0.65 },
+  source: 'user_suggested',
+  priorityWeight: 1,
+  exampleAnswers: answers,
+  test: candidate => answers[String (candidate.id) as `${ number }`] === 'yes',
+})
+
+
+const answer = (
+    question:  GekanatorQuestion,
+    value:     GekanatorAnswerValue,
+): GekanatorAnswerLog => ({
+  questionId: question.id,
+  questionText: question.text,
+  questionCondition: question.condition,
+  answer: value,
+  originalAnswer: value,
+})
+
+
+describe('candidatePostsFor', () => {
+  it('lets recovered candidates ignore old answers but not later answers', () => {
+    const posts = [post (1), post (2), post (3)]
+    const oldQuestion = postSimilarityQuestion ('old', {
+	1: 'no',
+	2: 'yes',
+	3: 'yes',
+    })
+    const laterQuestion = postSimilarityQuestion ('later', {
+	1: 'no',
+	2: 'no',
+	3: 'yes',
+    })
+
+    const candidates = candidatePostsFor ({
+	posts,
+	questions: [oldQuestion, laterQuestion],
+	answers: [answer (oldQuestion, 'yes'), answer (laterQuestion, 'yes')],
+	softenedQuestionIds: new Set (),
+	rejectedPostIds: new Set (),
+	recoveredCandidatePosts: new Map ([
+	    [1, 1],
+	    [3, 1],
+	]) })
+
+    expect(candidates.map (candidate => candidate.id)).toEqual ([3])
+  })
+
+  it('does not let recovered candidates bypass explicit rejected posts', () => {
+    const posts = [post (1), post (2)]
+    const question = postSimilarityQuestion ('question', {
+	1: 'yes',
+	2: 'yes',
+    })
+
+    const candidates = candidatePostsFor ({
+	posts,
+	questions: [question],
+	answers: [answer (question, 'yes')],
+	softenedQuestionIds: new Set (),
+	rejectedPostIds: new Set ([1]),
+	recoveredCandidatePosts: new Map ([[1, 1]]) })
+
+    expect(candidates.map (candidate => candidate.id)).toEqual ([2])
+  })
+})
+
+
+describe('hardFilteredPostsForAnswer', () => {
+  it('returns zero candidates without falling back to the original pool', () => {
+    const posts = [post (1), post (2)]
+    const question = postSimilarityQuestion ('question', {
+	1: 'yes',
+	2: 'yes',
+    })
+
+    expect(hardFilteredPostsForAnswer ({
+	posts,
+	question,
+	answer: 'no',
+    })).toEqual ([])
+  })
+})
+
+
+describe('recoverCandidatePosts', () => {
+  it('recovers high-score non-rejected, non-eligible candidates in staged batches', () => {
+    const posts = Array.from ({ length: 10 }, (_value, index) => post (index + 1))
+    const scores = new Map (posts.map (candidate => [candidate.id, candidate.id]))
+
+    const recovered = recoverCandidatePosts ({
+	posts,
+	scores,
+	rejectedPostIds: new Set ([10]),
+	recoveredCandidatePosts: new Map ([[8, 1]]),
+	eligiblePostIds: new Set ([9]),
+	answerCountAtRecovery: 2,
+	recoveryStepCount: 0,
+    })
+
+    expect(recovered?.recoveryStepCount).toBe (1)
+    expect([...(recovered?.recoveredCandidatePosts.keys () ?? [])])
+      .toEqual ([8, 7, 6, 5, 4, 3, 2])
+    expect(recovered?.recoveredCandidatePosts.get (7)).toBe (2)
+  })
+})

frontend/src/lib/gekanatorCandidateRecovery.ts

@@ -0,0 +1,146 @@
+import { expectedAnswerForQuestion } from '@/lib/gekanator'
+
+import type {
+    GekanatorAnswerLog,
+    GekanatorAnswerValue,
+    GekanatorQuestion,
+} from '@/lib/gekanator'
+import type { Post } from '@/types'
+
+
+export type RecoveredCandidatePost = {
+    postId:                number
+    answerCountAtRecovery: number }
+
+
+export const candidatePostsFor = ({
+    posts,
+    questions,
+    answers,
+    softenedQuestionIds,
+    rejectedPostIds,
+    recoveredCandidatePosts,
+}: {
+    posts:                   Post[]
+    questions:               GekanatorQuestion[]
+    answers:                 GekanatorAnswerLog[]
+    softenedQuestionIds:     Set<string>
+    rejectedPostIds:         Set<number>
+    recoveredCandidatePosts: Map<number, number>
+}): Post[] => {
+  const questionById = new Map (questions.map (question => [question.id, question]))
+
+  return posts.filter (post => {
+    if (rejectedPostIds.has (post.id))
+      return false
+
+    const answerCountAtRecovery = recoveredCandidatePosts.get (post.id)
+
+    return answers.every ((answer, index) => {
+      if (answerCountAtRecovery !== undefined && index < answerCountAtRecovery)
+	return true
+
+      if (softenedQuestionIds.has (answer.questionId))
+	return true
+
+      const question = questionById.get (answer.questionId)
+      if (!(question))
+	return true
+
+      switch (answer.answer)
+      {
+      case 'yes':
+      case 'no': {
+	const expected = expectedAnswerForQuestion (question, post)
+	return expected === null || expected === 'unknown' || expected === answer.answer
+      }
+      default:
+	return true
+      }
+    })
+  })
+}
+
+
+export const hardFilteredPostsForAnswer = ({
+    posts,
+    question,
+    answer,
+}: {
+    posts:     Post[]
+    question:  GekanatorQuestion
+    answer:    GekanatorAnswerValue
+}): Post[] => {
+  if (answer === 'unknown')
+    return posts
+
+  return posts.filter (post => {
+    const expected = expectedAnswerForQuestion (question, post)
+    return expected === null || expected === 'unknown' || expected === answer
+  })
+}
+
+
+const concreteAnswerOptions: GekanatorAnswerValue[] = [
+    'yes',
+    'no',
+    'partial',
+    'probably_no']
+
+
+export const allConcreteAnswerOptionsExhausted = (
+    posts:      Post[],
+    question:   GekanatorQuestion | null,
+): boolean => {
+  if (!(question))
+    return false
+
+  return concreteAnswerOptions.every (answer =>
+      hardFilteredPostsForAnswer ({ posts, question, answer }).length === 0)
+}
+
+
+const nextRecoveryBatchSize = (recoveryStepCount: number): number =>
+    6 * (2 ** recoveryStepCount)
+
+
+export const recoverCandidatePosts = ({
+    posts,
+    scores,
+    rejectedPostIds,
+    recoveredCandidatePosts,
+    eligiblePostIds,
+    answerCountAtRecovery,
+    recoveryStepCount,
+}: {
+    posts:                   Post[]
+    scores:                  Map<number, number>
+    rejectedPostIds:         Set<number>
+    recoveredCandidatePosts: Map<number, number>
+    eligiblePostIds:         Set<number>
+    answerCountAtRecovery:   number
+    recoveryStepCount:       number
+}): {
+    recoveredCandidatePosts: Map<number, number>
+    recoveryStepCount:       number
+} | null => {
+  const recovered = new Map (recoveredCandidatePosts)
+  const candidates = posts
+      .filter (post =>
+	  !(rejectedPostIds.has (post.id))
+	  && !(eligiblePostIds.has (post.id))
+	  && !(recovered.has (post.id)))
+      .sort ((a, b) =>
+	  (scores.get (b.id) ?? Number.NEGATIVE_INFINITY)
+	      - (scores.get (a.id) ?? Number.NEGATIVE_INFINITY))
+      .slice (0, nextRecoveryBatchSize (recoveryStepCount))
+
+  if (candidates.length === 0)
+    return null
+
+  candidates.forEach (post => recovered.set (post.id, answerCountAtRecovery))
+
+  return {
+      recoveredCandidatePosts: recovered,
+      recoveryStepCount: recoveryStepCount + 1 }
+}

frontend/src/lib/gekanatorQuestionFilters.ts

@@ -0,0 +1,167 @@
+import { titleLengthMinimumForCondition } from '@/lib/gekanator'
+
+import type {
+    GekanatorAnswerLog,
+    GekanatorAnswerValue,
+    GekanatorQuestion,
+} from '@/lib/gekanator'
+
+
+export const monthForCondition = (
+    condition:  GekanatorQuestion['condition'],
+): number | null => {
+  if (condition.type === 'original-month')
+    return condition.month
+
+  if (condition.type !== 'original-month-day')
+    return null
+
+  const month = Number (condition.monthDay.split ('-')[0])
+  return Number.isInteger (month) ? month : null
+}
+
+
+const isTitleLengthContradiction = (
+    candidate:  GekanatorQuestion['condition'],
+    previous:   GekanatorQuestion['condition'],
+    answer:     GekanatorAnswerValue,
+): boolean => {
+  const candidateLength = titleLengthMinimumForCondition (candidate)
+  const previousLength = titleLengthMinimumForCondition (previous)
+  if (candidateLength === null || previousLength === null)
+    return false
+
+  switch (answer)
+  {
+  case 'yes':
+    return candidateLength <= previousLength
+  case 'no':
+    return candidateLength >= previousLength
+  default:
+    return false
+  }
+}
+
+
+const isQuestionRedundantAfterAnswers = (
+    question:  GekanatorQuestion,
+    answers:   GekanatorAnswerLog[],
+): boolean => answers.some (answer => {
+  const previous = answer.questionCondition
+  return previous !== undefined
+      && isTitleLengthContradiction (question.condition, previous, answer.answer)
+})
+
+
+const isSourceFactBlocked = (
+    candidate:  GekanatorQuestion['condition'],
+    previous:   GekanatorQuestion['condition'],
+    answer:     GekanatorAnswerValue,
+): boolean => {
+  if (candidate.type !== 'source' || previous.type !== 'source')
+    return false
+
+  switch (answer)
+  {
+  case 'yes':
+    return true
+  case 'no':
+    return candidate.host === previous.host
+  default:
+    return false
+  }
+}
+
+
+const isOriginalYearFactBlocked = (
+    candidate:  GekanatorQuestion['condition'],
+    previous:   GekanatorQuestion['condition'],
+    answer:     GekanatorAnswerValue,
+): boolean => {
+  if (candidate.type !== 'original-year' || previous.type !== 'original-year')
+    return false
+
+  switch (answer)
+  {
+  case 'yes':
+    return true
+  case 'no':
+    return candidate.year === previous.year
+  default:
+    return false
+  }
+}
+
+
+const isOriginalMonthFactBlocked = (
+    candidate:  GekanatorQuestion['condition'],
+    previous:   GekanatorQuestion['condition'],
+    answer:     GekanatorAnswerValue,
+): boolean => {
+  switch (answer)
+  {
+  case 'yes':
+    if (previous.type === 'original-month')
+      {
+	if (candidate.type === 'original-month')
+	  return true
+
+	if (candidate.type === 'original-month-day')
+	  return monthForCondition (candidate) !== previous.month
+
+	return false
+      }
+
+    if (previous.type === 'original-month-day')
+      return candidate.type === 'original-month'
+	  || candidate.type === 'original-month-day'
+
+    return false
+  case 'no':
+    if (previous.type === 'original-month')
+      {
+	if (candidate.type === 'original-month')
+	  return candidate.month === previous.month
+
+	if (candidate.type === 'original-month-day')
+	  return monthForCondition (candidate) === previous.month
+
+	return false
+      }
+
+    if (previous.type === 'original-month-day')
+      return candidate.type === 'original-month-day'
+	  && candidate.monthDay === previous.monthDay
+
+    return false
+  default:
+    return false
+  }
+}
+
+
+const isFactQuestionBlocked = (
+    candidate:  GekanatorQuestion['condition'],
+    previous:   GekanatorQuestion['condition'],
+    answer:     GekanatorAnswerValue,
+): boolean => {
+  if (!(answer === 'yes' || answer === 'no'))
+    return false
+
+  return isSourceFactBlocked (candidate, previous, answer)
+      || isOriginalYearFactBlocked (candidate, previous, answer)
+      || isOriginalMonthFactBlocked (candidate, previous, answer)
+}
+
+
+export const isQuestionHardFilteredAfterAnswers = (
+    question:  GekanatorQuestion,
+    answers:   GekanatorAnswerLog[],
+): boolean => answers.some (answer => {
+  const previous = answer.questionCondition
+  if (previous === undefined)
+    return false
+
+  return isQuestionRedundantAfterAnswers (question, [answer])
+      || isFactQuestionBlocked (question.condition, previous, answer.answer)
+})

frontend/src/lib/queryKeys.ts

@@ -12,8 +12,8 @@ export const gekanatorKeys = {
     root:      ['gekanator'] as const,
     posts:     () => ['gekanator', 'posts'] as const,
     questions: () => ['gekanator', 'questions'] as const,
-    extraQuestions: (gameId: number) =>
+    extraQuestions: (gameId: number, nonce: string) =>
-		       ['gekanator', 'games', gameId, 'extra-questions'] as const }
+		       ['gekanator', 'games', gameId, 'extra-questions', nonce] as const }
 
 export const tagsKeys = {
     root:         ['tags'] as const,

frontend/src/pages/GekanatorPage.test.tsx

@@ -0,0 +1,154 @@
+import { describe, expect, it } from 'vitest'
+
+import { isQuestionHardFilteredAfterAnswers } from '@/lib/gekanatorQuestionFilters'
+
+import type {
+    GekanatorAnswerLog,
+    GekanatorAnswerValue,
+    GekanatorQuestion,
+    GekanatorQuestionCondition,
+} from '@/lib/gekanator'
+
+
+const question = (
+    condition:  GekanatorQuestionCondition,
+): GekanatorQuestion => ({
+  id: `${ condition.type }:candidate`,
+  text: 'candidate?',
+  kind: condition.type === 'source'
+      ? 'source'
+      : condition.type.startsWith ('original-')
+	? 'original_date'
+	: condition.type.startsWith ('title-')
+	  ? 'title'
+	  : 'tag',
+  condition,
+  source: 'default',
+  priorityWeight: 1,
+  test: () => false,
+})
+
+
+const answer = (
+    condition:  GekanatorQuestionCondition,
+    value:      GekanatorAnswerValue,
+): GekanatorAnswerLog => ({
+  questionId: 'previous',
+  questionText: 'previous?',
+  questionCondition: condition,
+  answer: value,
+  originalAnswer: value,
+})
+
+
+const blocked = (
+    candidate:  GekanatorQuestionCondition,
+    previous:   GekanatorQuestionCondition,
+    value:      GekanatorAnswerValue,
+): boolean =>
+    isQuestionHardFilteredAfterAnswers (question (candidate), [answer (previous, value)])
+
+
+describe('isQuestionHardFilteredAfterAnswers', () => {
+  it('blocks only contradictory or redundant month questions after a yes answer', () => {
+    const previous: GekanatorQuestionCondition = { type: 'original-month', month: 12 }
+
+    expect(blocked ({ type: 'original-month', month: 12 }, previous, 'yes')).toBe(true)
+    expect(blocked ({ type: 'original-month', month: 2 }, previous, 'yes')).toBe(true)
+    expect(blocked ({ type: 'original-month-day', monthDay: '2-14' }, previous, 'yes'))
+      .toBe(true)
+    expect(blocked ({ type: 'original-month-day', monthDay: '12-25' }, previous, 'yes'))
+      .toBe(false)
+    expect(blocked ({ type: 'original-year', year: 2024 }, previous, 'yes')).toBe(false)
+    expect(blocked ({ type: 'source', host: 'example.com' }, previous, 'yes')).toBe(false)
+    expect(blocked ({ type: 'tag', key: 'character:喜多郁代' }, previous, 'yes')).toBe(false)
+  })
+
+  it('blocks same-month facts after a no answer', () => {
+    const previous: GekanatorQuestionCondition = { type: 'original-month', month: 12 }
+
+    expect(blocked ({ type: 'original-month', month: 12 }, previous, 'no')).toBe(true)
+    expect(blocked ({ type: 'original-month', month: 2 }, previous, 'no')).toBe(false)
+    expect(blocked ({ type: 'original-month-day', monthDay: '12-25' }, previous, 'no'))
+      .toBe(true)
+    expect(blocked ({ type: 'original-month-day', monthDay: '2-14' }, previous, 'no'))
+      .toBe(false)
+  })
+
+  it('blocks all month and month-day questions after a month-day yes answer', () => {
+    const previous: GekanatorQuestionCondition = {
+      type: 'original-month-day',
+      monthDay: '12-25',
+    }
+
+    expect(blocked ({ type: 'original-month', month: 12 }, previous, 'yes')).toBe(true)
+    expect(blocked ({ type: 'original-month', month: 2 }, previous, 'yes')).toBe(true)
+    expect(blocked ({ type: 'original-month-day', monthDay: '12-25' }, previous, 'yes'))
+      .toBe(true)
+    expect(blocked ({ type: 'original-month-day', monthDay: '12-26' }, previous, 'yes'))
+      .toBe(true)
+  })
+
+  it('blocks the same month-day only after a month-day no answer', () => {
+    const previous: GekanatorQuestionCondition = {
+      type: 'original-month-day',
+      monthDay: '12-25',
+    }
+
+    expect(blocked ({ type: 'original-month-day', monthDay: '12-25' }, previous, 'no'))
+      .toBe(true)
+    expect(blocked ({ type: 'original-month-day', monthDay: '12-26' }, previous, 'no'))
+      .toBe(false)
+    expect(blocked ({ type: 'original-month', month: 12 }, previous, 'no')).toBe(false)
+  })
+
+  it('blocks year and source as single-value facts', () => {
+    expect(blocked (
+      { type: 'original-year', year: 2025 },
+      { type: 'original-year', year: 2024 },
+      'yes',
+    )).toBe(true)
+    expect(blocked (
+      { type: 'original-year', year: 2024 },
+      { type: 'original-year', year: 2024 },
+      'no',
+    )).toBe(true)
+    expect(blocked (
+      { type: 'source', host: 'b.example' },
+      { type: 'source', host: 'a.example' },
+      'yes',
+    )).toBe(true)
+    expect(blocked (
+      { type: 'source', host: 'b.example' },
+      { type: 'source', host: 'a.example' },
+      'no',
+    )).toBe(false)
+  })
+
+  it('does not hard-filter partial, probably_no, or unknown fact answers', () => {
+    const previous: GekanatorQuestionCondition = { type: 'original-month', month: 12 }
+    const candidate: GekanatorQuestionCondition = { type: 'original-month', month: 2 }
+
+    expect(blocked (candidate, previous, 'partial')).toBe(false)
+    expect(blocked (candidate, previous, 'probably_no')).toBe(false)
+    expect(blocked (candidate, previous, 'unknown')).toBe(false)
+  })
+
+  it('keeps title-length hard redundancy for yes and no only', () => {
+    const previous: GekanatorQuestionCondition = {
+      type: 'title-length-at-least',
+      length: 30,
+    }
+
+    expect(blocked ({ type: 'title-length-at-least', length: 20 }, previous, 'yes'))
+      .toBe(true)
+    expect(blocked ({ type: 'title-length-at-least', length: 40 }, previous, 'yes'))
+      .toBe(false)
+    expect(blocked ({ type: 'title-length-at-least', length: 40 }, previous, 'no'))
+      .toBe(true)
+    expect(blocked ({ type: 'title-length-at-least', length: 20 }, previous, 'no'))
+      .toBe(false)
+    expect(blocked ({ type: 'title-length-at-least', length: 20 }, previous, 'partial'))
+      .toBe(false)
+  })
+})