backend/app/controllers/theatre_programmes_controller.rb

@@ -12,6 +12,8 @@ class TheatreProgrammesController < ApplicationController
                  .order(position: :desc).limit(100)
                  .limit(limit)
 
-    render json: programmes.as_json(include: { post: PostRepr::BASE })
+    render json: programmes.map { |programme|
+      programme.as_json.merge(post: PostRepr.base(programme.post))
+    }
   end
 end

backend/app/controllers/theatre_skip_events_controller.rb

@@ -0,0 +1,24 @@
+class TheatreSkipEventsController < ApplicationController
+  def index
+    limit = params[:limit].to_i
+    limit = 50 if limit <= 0
+
+    events =
+        TheatreSkipEvent
+        .where(theatre_id: params[:theatre_id])
+        .includes(:skipped_by_user, :users, :tags, post: { tags: :tag_name })
+        .order(created_at: :desc)
+        .limit(limit)
+
+    render json: events.map { |event|
+      { id: event.id,
+        theatre_id: event.theatre_id,
+        post: PostRepr.base(event.post),
+        skipped_by_user: UserRepr.base(event.skipped_by_user),
+        voters: event.users.map { |user| UserRepr.base(user) },
+        tags: event.tags.map { |tag| TagRepr.inline(tag) },
+        programme_position: event.programme_position,
+        created_at: event.created_at }
+    }
+  end
+end

backend/app/controllers/theatres_controller.rb

@@ -31,9 +31,7 @@ class TheatresController < ApplicationController
       post_started_at = theatre.current_post_started_at
     end
 
-    render json: {
-        host_flg:, post_id:, post_started_at:,
-        watching_users: theatre.watching_users.as_json(only: [:id, :name]) }
+    render json: theatre_info_json(theatre, host_flg:, post_id:, post_started_at:)
   end
 
   def next_post
@@ -44,14 +42,95 @@ class TheatresController < ApplicationController
     return head :forbidden if theatre.host_user != current_user
 
     ApplicationRecord.transaction do
-      post = Post.where("url LIKE '%nicovideo.jp%'")
-             .order('RAND()')
-             .first
-      theatre.update!(current_post: post, current_post_started_at: Time.current)
-      position = (theatre.programmes.maximum(:position) || 0) + 1
-      theatre.programmes.create!(position:, post:)
+      theatre.lock!
+      TheatrePostAdvancer.call(theatre:)
     end
 
     head :no_content
   end
+
+  def skip_vote
+    return head :unauthorized unless current_user
+
+    theatre = Theatre.find_by(id: params[:id])
+    return head :not_found unless theatre
+
+    skipped = false
+
+    ApplicationRecord.transaction do
+      theatre.lock!
+      if theatre.current_post
+        TheatreWatchingUser.find_or_initialize_by(theatre:, user: current_user).tap {
+          _1.expires_at = 30.seconds.from_now
+        }.save!
+
+        TheatreSkipVote.find_or_create_by!(theatre:, post: theatre.current_post, user: current_user)
+
+        vote_status = skip_vote_status(theatre)
+        if vote_status[:votes_count] >= vote_status[:required_count]
+          TheatreSkipFinalizer.call(theatre:, user: current_user)
+          TheatrePostAdvancer.call(theatre:)
+          skipped = true
+        end
+      end
+    end
+
+    theatre.reload
+    render json: theatre_info_json(theatre, skipped:)
+  end
+
+  def unskip_vote
+    return head :unauthorized unless current_user
+
+    theatre = Theatre.find_by(id: params[:id])
+    return head :not_found unless theatre
+
+    if theatre.current_post
+      TheatreSkipVote.where(theatre:, post: theatre.current_post, user: current_user).delete_all
+    end
+
+    render json: theatre_info_json(theatre, skipped: false)
+  end
+
+  def post_selection_weights
+    theatre = Theatre.find_by(id: params[:id])
+    return head :not_found unless theatre
+
+    render json: TheatrePostSelector.new(theatre:).weight_json
+  end
+
+  private
+
+  def theatre_info_json(theatre, host_flg: nil, post_id: nil, post_started_at: nil, skipped: nil)
+    host_flg = theatre.host_user_id == current_user&.id if host_flg.nil?
+    post_id = theatre.current_post_id if post_id.nil?
+    post_started_at = theatre.current_post_started_at if post_started_at.nil?
+
+    json = { host_flg:,
+             post_id:,
+             post_started_at:,
+             post_elapsed_ms: post_started_at ? ((Time.current - post_started_at) * 1000).floor : nil,
+             watching_users: theatre.watching_users.as_json(only: [:id, :name]),
+             skip_vote: skip_vote_status(theatre) }
+    json[:skipped] = skipped unless skipped.nil?
+    json
+  end
+
+  def skip_vote_status(theatre)
+    watching_user_ids = theatre.watching_users.ids
+    watching_users_count = watching_user_ids.size
+    required_count = (watching_users_count / 2) + 1
+    post = theatre.current_post
+    votes =
+        if post
+          TheatreSkipVote.where(theatre:, post:, user_id: watching_user_ids)
+        else
+          TheatreSkipVote.none
+        end
+
+    { votes_count: post ? votes.count : 0,
+      required_count:,
+      watching_users_count:,
+      voted: post && current_user ? votes.exists?(user_id: current_user.id) : false }
+  end
 end

backend/app/models/theatre.rb

@@ -8,6 +8,8 @@ class Theatre < ApplicationRecord
   has_many :watching_users, through: :active_theatre_watching_users, source: :user
 
   has_many :programmes, class_name: 'TheatreProgramme'
+  has_many :skip_votes, class_name: 'TheatreSkipVote', dependent: :delete_all
+  has_many :skip_events, class_name: 'TheatreSkipEvent', dependent: :delete_all
 
   belongs_to :host_user, class_name: 'User', optional: true
   belongs_to :current_post, class_name: 'Post', optional: true

backend/app/models/theatre_skip_event.rb

@@ -0,0 +1,10 @@
+class TheatreSkipEvent < ApplicationRecord
+  belongs_to :theatre
+  belongs_to :post
+  belongs_to :skipped_by_user, class_name: 'User'
+
+  has_many :voters, class_name: 'TheatreSkipEventVoter', dependent: :delete_all
+  has_many :event_tags, class_name: 'TheatreSkipEventTag', dependent: :delete_all
+  has_many :users, through: :voters
+  has_many :tags, through: :event_tags
+end

backend/app/models/theatre_skip_event_tag.rb

@@ -0,0 +1,6 @@
+class TheatreSkipEventTag < ApplicationRecord
+  self.primary_key = :theatre_skip_event_id, :tag_id
+
+  belongs_to :theatre_skip_event
+  belongs_to :tag
+end

backend/app/models/theatre_skip_event_voter.rb

@@ -0,0 +1,6 @@
+class TheatreSkipEventVoter < ApplicationRecord
+  self.primary_key = :theatre_skip_event_id, :user_id
+
+  belongs_to :theatre_skip_event
+  belongs_to :user
+end

backend/app/models/theatre_skip_vote.rb

@@ -0,0 +1,7 @@
+class TheatreSkipVote < ApplicationRecord
+  self.primary_key = :theatre_id, :post_id, :user_id
+
+  belongs_to :theatre
+  belongs_to :post
+  belongs_to :user
+end

backend/app/services/theatre_post_advancer.rb

@@ -0,0 +1,29 @@
+class TheatrePostAdvancer
+  def self.call(theatre:)
+    new(theatre:).call
+  end
+
+  def initialize(theatre:)
+    @theatre = theatre
+  end
+
+  def call
+    previous_post = theatre.current_post
+    post = TheatrePostSelector.new(theatre:).select
+
+    TheatreSkipVote.where(theatre:, post: previous_post).delete_all if previous_post
+
+    theatre.update!(current_post: post, current_post_started_at: post ? Time.current : nil)
+
+    if post
+      position = (theatre.programmes.maximum(:position) || 0) + 1
+      theatre.programmes.create!(position:, post:)
+    end
+
+    post
+  end
+
+  private
+
+  attr_reader :theatre
+end

backend/app/services/theatre_post_selector.rb

@@ -0,0 +1,92 @@
+class TheatrePostSelector
+  Candidate = Struct.new(:post, :weight, :penalty, :tags, keyword_init: true)
+
+  def initialize(theatre:)
+    @theatre = theatre
+  end
+
+  def select
+    candidates = weighted_candidates
+    return nil if candidates.empty?
+
+    total = candidates.sum(&:weight)
+    target = rand * total
+
+    candidates.each do |candidate|
+      target -= candidate.weight
+      return candidate.post if target <= 0
+    end
+
+    candidates.last.post
+  end
+
+  def weight_json(limit: 20)
+    candidates = weighted_candidates
+    sorted = candidates.sort_by { |candidate| [candidate.weight, candidate.post.id] }
+
+    { tag_penalties: tag_penalty_json,
+      lightest_posts: post_weight_json(sorted.first(limit)),
+      heaviest_posts: post_weight_json(sorted.reverse.first(limit)) }
+  end
+
+  private
+
+  attr_reader :theatre
+
+  def weighted_candidates
+    @weighted_candidates ||= begin
+      penalties = tag_penalties
+      posts = eligible_posts.includes(tags: :tag_name).to_a
+
+      posts.map do |post|
+        post_tags = post.tags.to_a
+        penalty = post_tags.sum { |tag| penalties[tag.id].to_i }
+        Candidate.new(post:, penalty:, tags: post_tags, weight: 1.0 / (1.0 + penalty))
+      end
+    end
+  end
+
+  def eligible_posts
+    posts = Post.where("url LIKE '%nicovideo.jp%'")
+    posts = posts.where.not(id: theatre.current_post_id) if theatre.current_post_id
+    posts
+  end
+
+  def active_user_ids
+    @active_user_ids ||= theatre.watching_users.ids
+  end
+
+  def tag_penalties
+    @tag_penalties ||=
+        if active_user_ids.empty?
+          {}
+        else
+          TheatreSkipEventVoter
+          .joins(theatre_skip_event: :event_tags)
+          .where(user_id: active_user_ids)
+          .group('theatre_skip_event_tags.tag_id')
+          .count
+        end
+  end
+
+  def tag_penalty_json
+    return [] if tag_penalties.empty?
+
+    tags = Tag.where(id: tag_penalties.keys).includes(:tag_name).index_by(&:id)
+    tag_penalties.map { |tag_id, penalty|
+      tag = tags[tag_id]
+      next unless tag
+
+      { tag: TagRepr.inline(tag), penalty: }
+    }.compact.sort_by { |row| [-row[:penalty], row[:tag]['name'].to_s] }
+  end
+
+  def post_weight_json(candidates)
+    candidates.map { |candidate|
+      { post: PostRepr.base(candidate.post),
+        weight: candidate.weight,
+        penalty: candidate.penalty,
+        tags: candidate.tags.map { |tag| TagRepr.inline(tag) } }
+    }
+  end
+end

backend/app/services/theatre_skip_finalizer.rb

@@ -0,0 +1,40 @@
+class TheatreSkipFinalizer
+  def self.call(theatre:, user:)
+    new(theatre:, user:).call
+  end
+
+  def initialize(theatre:, user:)
+    @theatre = theatre
+    @user = user
+  end
+
+  def call
+    return unless theatre.current_post
+
+    post = theatre.current_post
+    voters = TheatreSkipVote.where(theatre:, post:).includes(:user).map(&:user)
+    return if voters.empty?
+
+    event = TheatreSkipEvent.create!(
+        theatre:,
+        post:,
+        skipped_by_user: user,
+        programme_position: theatre.programmes.maximum(:position))
+
+    voters.uniq(&:id).each do |voter|
+      TheatreSkipEventVoter.create!(theatre_skip_event: event, user: voter)
+    end
+
+    post.tags.find_each do |tag|
+      TheatreSkipEventTag.create!(theatre_skip_event: event, tag:)
+    end
+
+    TheatreSkipVote.where(theatre:, post:).delete_all
+
+    event
+  end
+
+  private
+
+  attr_reader :theatre, :user
+end

backend/config/routes.rb

@@ -85,10 +85,14 @@ Rails.application.routes.draw do
     member do
       put :watching
       patch :next_post
+      put :skip_vote
+      delete :skip_vote, action: :unskip_vote
+      get :post_selection_weights
     end
 
     resources :comments, controller: :theatre_comments, only: [:index, :create, :destroy]
     resources :programmes, controller: :theatre_programmes, only: [:index]
+    resources :skip_events, controller: :theatre_skip_events, only: [:index]
   end
 
   resources :materials, only: [:index, :show, :create, :update, :destroy]

backend/db/migrate/20260606000000_create_theatre_skip_votes_and_events.rb

@@ -0,0 +1,36 @@
+class CreateTheatreSkipVotesAndEvents < ActiveRecord::Migration[8.0]
+  def change
+    create_table :theatre_skip_votes, primary_key: [:theatre_id, :post_id, :user_id] do |t|
+      t.references :theatre, null: false, foreign_key: true
+      t.references :post, null: false, foreign_key: true
+      t.references :user, null: false, foreign_key: true
+      t.timestamps
+    end
+
+    create_table :theatre_skip_events do |t|
+      t.references :theatre, null: false, foreign_key: true
+      t.references :post, null: false, foreign_key: true
+      t.references :skipped_by_user, null: false, foreign_key: { to_table: :users }
+      t.integer :programme_position
+      t.datetime :created_at, null: false
+    end
+
+    create_table :theatre_skip_event_voters, primary_key: [:theatre_skip_event_id, :user_id] do |t|
+      t.references :theatre_skip_event, null: false, foreign_key: true
+      t.references :user, null: false, foreign_key: true
+    end
+
+    create_table :theatre_skip_event_tags, primary_key: [:theatre_skip_event_id, :tag_id] do |t|
+      t.references :theatre_skip_event, null: false, foreign_key: true
+      t.references :tag, null: false, foreign_key: true
+    end
+
+    add_index :theatre_skip_events, [:theatre_id, :created_at]
+    add_index :theatre_skip_votes, [:theatre_id, :post_id, :created_at],
+              name: 'idx_theatre_skip_votes_theatre_post_created'
+    add_index :theatre_skip_event_voters, [:user_id, :theatre_skip_event_id],
+              name: 'idx_theatre_skip_event_voters_user_event'
+    add_index :theatre_skip_event_tags, [:tag_id, :theatre_skip_event_id],
+              name: 'idx_theatre_skip_event_tags_tag_event'
+  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_05_14_221900) do
+ActiveRecord::Schema[8.0].define(version: 2026_06_06_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
@@ -137,6 +137,19 @@ ActiveRecord::Schema[8.0].define(version: 2026_05_14_221900) 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 +200,11 @@ ActiveRecord::Schema[8.0].define(version: 2026_05_14_221900) 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
 
@@ -292,6 +308,46 @@ ActiveRecord::Schema[8.0].define(version: 2026_05_14_221900) do
     t.index ["theatre_id"], name: "index_theatre_programmes_on_theatre_id"
   end
 
+  create_table "theatre_skip_event_tags", primary_key: ["theatre_skip_event_id", "tag_id"], charset: "utf8mb4", collation: "utf8mb4_0900_ai_ci", force: :cascade do |t|
+    t.bigint "theatre_skip_event_id", null: false
+    t.bigint "tag_id", null: false
+    t.index ["tag_id", "theatre_skip_event_id"], name: "idx_theatre_skip_event_tags_tag_event"
+    t.index ["tag_id"], name: "index_theatre_skip_event_tags_on_tag_id"
+    t.index ["theatre_skip_event_id"], name: "index_theatre_skip_event_tags_on_theatre_skip_event_id"
+  end
+
+  create_table "theatre_skip_event_voters", primary_key: ["theatre_skip_event_id", "user_id"], charset: "utf8mb4", collation: "utf8mb4_0900_ai_ci", force: :cascade do |t|
+    t.bigint "theatre_skip_event_id", null: false
+    t.bigint "user_id", null: false
+    t.index ["theatre_skip_event_id"], name: "index_theatre_skip_event_voters_on_theatre_skip_event_id"
+    t.index ["user_id", "theatre_skip_event_id"], name: "idx_theatre_skip_event_voters_user_event"
+    t.index ["user_id"], name: "index_theatre_skip_event_voters_on_user_id"
+  end
+
+  create_table "theatre_skip_events", charset: "utf8mb4", collation: "utf8mb4_0900_ai_ci", force: :cascade do |t|
+    t.bigint "theatre_id", null: false
+    t.bigint "post_id", null: false
+    t.bigint "skipped_by_user_id", null: false
+    t.integer "programme_position"
+    t.datetime "created_at", null: false
+    t.index ["post_id"], name: "index_theatre_skip_events_on_post_id"
+    t.index ["skipped_by_user_id"], name: "index_theatre_skip_events_on_skipped_by_user_id"
+    t.index ["theatre_id", "created_at"], name: "index_theatre_skip_events_on_theatre_id_and_created_at"
+    t.index ["theatre_id"], name: "index_theatre_skip_events_on_theatre_id"
+  end
+
+  create_table "theatre_skip_votes", primary_key: ["theatre_id", "post_id", "user_id"], charset: "utf8mb4", collation: "utf8mb4_0900_ai_ci", force: :cascade do |t|
+    t.bigint "theatre_id", null: false
+    t.bigint "post_id", null: false
+    t.bigint "user_id", null: false
+    t.datetime "created_at", null: false
+    t.datetime "updated_at", null: false
+    t.index ["post_id"], name: "index_theatre_skip_votes_on_post_id"
+    t.index ["theatre_id", "post_id", "created_at"], name: "idx_theatre_skip_votes_theatre_post_created"
+    t.index ["theatre_id"], name: "index_theatre_skip_votes_on_theatre_id"
+    t.index ["user_id"], name: "index_theatre_skip_votes_on_user_id"
+  end
+
   create_table "theatre_watching_users", primary_key: ["theatre_id", "user_id"], charset: "utf8mb4", collation: "utf8mb4_0900_ai_ci", force: :cascade do |t|
     t.bigint "theatre_id", null: false
     t.bigint "user_id", null: false
@@ -456,6 +512,8 @@ ActiveRecord::Schema[8.0].define(version: 2026_05_14_221900) 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"
@@ -476,6 +534,16 @@ ActiveRecord::Schema[8.0].define(version: 2026_05_14_221900) do
   add_foreign_key "theatre_comments", "users"
   add_foreign_key "theatre_programmes", "posts"
   add_foreign_key "theatre_programmes", "theatres"
+  add_foreign_key "theatre_skip_event_tags", "tags"
+  add_foreign_key "theatre_skip_event_tags", "theatre_skip_events"
+  add_foreign_key "theatre_skip_event_voters", "theatre_skip_events"
+  add_foreign_key "theatre_skip_event_voters", "users"
+  add_foreign_key "theatre_skip_events", "posts"
+  add_foreign_key "theatre_skip_events", "theatres"
+  add_foreign_key "theatre_skip_events", "users", column: "skipped_by_user_id"
+  add_foreign_key "theatre_skip_votes", "posts"
+  add_foreign_key "theatre_skip_votes", "theatres"
+  add_foreign_key "theatre_skip_votes", "users"
   add_foreign_key "theatre_watching_users", "theatres"
   add_foreign_key "theatre_watching_users", "users"
   add_foreign_key "theatres", "posts", column: "current_post_id"

backend/spec/requests/theatre_programmes_spec.rb

@@ -0,0 +1,31 @@
+require 'rails_helper'
+
+RSpec.describe 'TheatreProgrammes', type: :request do
+  describe 'GET /theatres/:theatre_id/programmes' do
+    let(:theatre) { create(:theatre) }
+    let(:other_theatre) { create(:theatre) }
+    let(:post_1) { Post.create!(title: 'first', url: 'https://www.nicovideo.jp/watch/sm1') }
+    let(:post_2) { Post.create!(title: 'second', url: 'https://www.nicovideo.jp/watch/sm2') }
+    let(:other_post) { Post.create!(title: 'other', url: 'https://www.nicovideo.jp/watch/sm3') }
+
+    before do
+      TheatreProgramme.create!(theatre:, position: 1, post: post_1, created_at: 2.minutes.ago)
+      TheatreProgramme.create!(theatre:, position: 2, post: post_2, created_at: 1.minute.ago)
+      TheatreProgramme.create!(
+        theatre: other_theatre,
+        position: 1,
+        post: other_post,
+        created_at: 1.minute.ago
+      )
+    end
+
+    it 'returns programmes for the theatre in descending position with post json' do
+      get "/theatres/#{theatre.id}/programmes"
+
+      expect(response).to have_http_status(:ok)
+      expect(json.map { _1['position'] }).to eq([2, 1])
+      expect(json.map { _1.dig('post', 'title') }).to eq(['second', 'first'])
+      expect(json.first['post']).to include('id' => post_2.id, 'url' => post_2.url)
+    end
+  end
+end

backend/spec/requests/theatres_spec.rb

@@ -14,10 +14,17 @@ RSpec.describe 'Theatres API', type: :request do
   let(:member) { create(:user, :member, name: 'member user') }
   let(:other_user) { create(:user, :member, name: 'other user') }
 
-  let!(:youtube_post) do
+  let!(:niconico_post) do
     Post.create!(
-      title: 'youtube post',
-      url: 'https://www.youtube.com/watch?v=spec123'
+      title: 'niconico post',
+      url: 'https://www.nicovideo.jp/watch/sm123'
+    )
+  end
+
+  let!(:second_niconico_post) do
+    Post.create!(
+      title: 'second niconico post',
+      url: 'https://www.nicovideo.jp/watch/sm456'
     )
   end
 
@@ -120,7 +127,8 @@ RSpec.describe 'Theatres API', type: :request do
         expect(json).to include(
           'host_flg' => true,
           'post_id' => nil,
-          'post_started_at' => nil
+          'post_started_at' => nil,
+          'post_elapsed_ms' => nil
         )
 
         expect(json.fetch('watching_users')).to contain_exactly(
@@ -177,7 +185,8 @@ RSpec.describe 'Theatres API', type: :request do
         expect(json).to include(
           'host_flg' => false,
           'post_id' => nil,
-          'post_started_at' => nil
+          'post_started_at' => nil,
+          'post_elapsed_ms' => nil
         )
 
         expect(json.fetch('watching_users')).to contain_exactly(
@@ -204,7 +213,7 @@ RSpec.describe 'Theatres API', type: :request do
         )
         theatre.update!(
           host_user: other_user,
-          current_post: youtube_post,
+          current_post: niconico_post,
           current_post_started_at: started_at
         )
         sign_in_as(member)
@@ -220,9 +229,11 @@ RSpec.describe 'Theatres API', type: :request do
         expect(theatre.host_user_id).to eq(member.id)
 
         expect(json['host_flg']).to eq(true)
-        expect(json['post_id']).to eq(youtube_post.id)
+        expect(json['post_id']).to eq(niconico_post.id)
         expect(Time.zone.parse(json['post_started_at']))
           .to be_within(1.second).of(started_at)
+        expect(json['post_elapsed_ms'])
+          .to be_within(1_000).of(120_000)
       end
     end
   end
@@ -273,17 +284,20 @@ RSpec.describe 'Theatres API', type: :request do
       it 'sets current_post to an eligible post and updates current_post_started_at' do
         expect { do_request }
           .to change { theatre.reload.current_post_id }
-          .from(nil).to(youtube_post.id)
 
         expect(response).to have_http_status(:no_content)
+        expect([niconico_post.id, second_niconico_post.id])
+          .to include(theatre.reload.current_post_id)
         expect(theatre.reload.current_post_started_at)
           .to be_within(1.second).of(Time.current)
+        expect(theatre.programmes.count).to eq(1)
       end
     end
 
     context 'when current user is host and no eligible post exists' do
       before do
-        youtube_post.destroy!
+        niconico_post.destroy!
+        second_niconico_post.destroy!
         theatre.update!(
           host_user: member,
           current_post: other_post,
@@ -299,9 +313,117 @@ RSpec.describe 'Theatres API', type: :request do
 
         theatre.reload
         expect(theatre.current_post_id).to be_nil
-        expect(theatre.current_post_started_at)
-          .to be_within(1.second).of(Time.current)
+        expect(theatre.current_post_started_at).to be_nil
       end
     end
   end
+
+  describe 'PUT /theatres/:id/skip_vote' do
+    subject(:do_request) do
+      put "/theatres/#{theatre.id}/skip_vote"
+    end
+
+    let(:third_user) { create(:user, :member, name: 'third user') }
+
+    before do
+      theatre.update!(current_post: niconico_post, current_post_started_at: 10.seconds.ago)
+      [member, other_user, third_user].each do |user|
+        TheatreWatchingUser.create!(
+          theatre:,
+          user:,
+          expires_at: 10.seconds.from_now
+        )
+      end
+    end
+
+    it 'records a vote and returns the current vote status before majority' do
+      sign_in_as(member)
+
+      expect { do_request }.to change(TheatreSkipVote, :count).by(1)
+
+      expect(response).to have_http_status(:ok)
+      expect(json['skipped']).to eq(false)
+      expect(json['post_id']).to eq(niconico_post.id)
+      expect(json['skip_vote']).to include(
+        'votes_count' => 1,
+        'required_count' => 2,
+        'watching_users_count' => 3,
+        'voted' => true
+      )
+    end
+
+    it 'finalizes skip when votes reach majority and stores voters and tag snapshots' do
+      tag = create(:tag, name: 'skip-target')
+      PostTag.create!(post: niconico_post, tag:)
+
+      TheatreSkipVote.create!(theatre:, post: niconico_post, user: member)
+      sign_in_as(other_user)
+
+      expect { do_request }
+        .to change(TheatreSkipEvent, :count).by(1)
+        .and change(TheatreSkipEventVoter, :count).by(2)
+        .and change(TheatreSkipEventTag, :count).by(1)
+
+      expect(response).to have_http_status(:ok)
+      expect(json['skipped']).to eq(true)
+      expect(json['post_id']).to eq(second_niconico_post.id)
+
+      event = TheatreSkipEvent.last
+      expect(event.post).to eq(niconico_post)
+      expect(event.users).to contain_exactly(member, other_user)
+      expect(event.tags).to contain_exactly(tag)
+      expect(TheatreSkipVote.where(theatre:, post: niconico_post)).to be_empty
+    end
+  end
+
+  describe 'DELETE /theatres/:id/skip_vote' do
+    before do
+      theatre.update!(current_post: niconico_post, current_post_started_at: 10.seconds.ago)
+      TheatreWatchingUser.create!(theatre:, user: member, expires_at: 10.seconds.from_now)
+      TheatreSkipVote.create!(theatre:, post: niconico_post, user: member)
+      sign_in_as(member)
+    end
+
+    it 'removes the current user vote' do
+      expect {
+        delete "/theatres/#{theatre.id}/skip_vote"
+      }.to change(TheatreSkipVote, :count).by(-1)
+
+      expect(response).to have_http_status(:ok)
+      expect(json['skip_vote']).to include(
+        'votes_count' => 0,
+        'required_count' => 1,
+        'watching_users_count' => 1,
+        'voted' => false
+      )
+    end
+  end
+
+  describe 'GET /theatres/:id/post_selection_weights' do
+    before do
+      theatre.update!(current_post: niconico_post)
+      TheatreWatchingUser.create!(theatre:, user: member, expires_at: 10.seconds.from_now)
+      sign_in_as(member)
+    end
+
+    it 'returns tag penalties and candidate weights for the current watchers' do
+      tag = create(:tag, name: 'heavy-tag')
+      PostTag.create!(post: second_niconico_post, tag:)
+      event = TheatreSkipEvent.create!(
+        theatre:,
+        post: niconico_post,
+        skipped_by_user: member,
+        created_at: Time.current
+      )
+      TheatreSkipEventVoter.create!(theatre_skip_event: event, user: member)
+      TheatreSkipEventTag.create!(theatre_skip_event: event, tag:)
+
+      get "/theatres/#{theatre.id}/post_selection_weights"
+
+      expect(response).to have_http_status(:ok)
+      expect(json['tag_penalties'].first['penalty']).to eq(1)
+      expect(json['lightest_posts'].first['post']['id']).to eq(second_niconico_post.id)
+      expect(json['lightest_posts'].first['penalty']).to eq(1)
+    end
+  end
 end

frontend/src/components/NicoViewer.tsx

@@ -37,11 +37,12 @@ type Props = {
     height:             number
     style?:             CSSProperties
     onLoadComplete?:    (info: NiconicoVideoInfo) => void
-    onMetadataChange?:  (meta: NiconicoMetadata) => void }
+    onMetadataChange?:  (meta: NiconicoMetadata) => void
+    onError?:           (data: unknown) => void }
 
 
 export default forwardRef ((props: Props, ref: ForwardedRef<NiconicoViewerHandle>) => {
-  const { id, width, height, style = { }, onLoadComplete, onMetadataChange } = props
+  const { id, width, height, style = { }, onLoadComplete, onMetadataChange, onError } = props
 
   const iframeRef = useRef<HTMLIFrameElement> (null)
   const playerId = useMemo (() => `nico-${ id }-${ Math.random ().toString (36).slice (2) }`, [id])
@@ -173,13 +174,16 @@ export default forwardRef ((props: Props, ref: ForwardedRef<NiconicoViewerHandle
 	}
 
       if (data.eventName === 'error')
-        console.error ('niconico player error:', data)
+        {
+          console.error ('niconico player error:', data)
+          onError?.(data)
+        }
     }
 
     addEventListener ('message', onMessage)
 
     return () => removeEventListener ('message', onMessage)
-  }, [onLoadComplete, onMetadataChange, playerId])
+  }, [onError, onLoadComplete, onMetadataChange, playerId])
 
   useLayoutEffect (() => {
     if (!(fullScreen))

frontend/src/components/PostEmbed.tsx

@@ -13,10 +13,11 @@ type Props = {
     ref?:               RefObject<NiconicoViewerHandle | null>
     post:               Post
     onLoadComplete?:    (info: NiconicoVideoInfo) => void
-    onMetadataChange?:  (meta: NiconicoMetadata) => void }
+    onMetadataChange?:  (meta: NiconicoMetadata) => void
+    onError?:           (data: unknown) => void }
 
 
-const PostEmbed: FC<Props> = ({ ref, post, onLoadComplete, onMetadataChange }) => {
+const PostEmbed: FC<Props> = ({ ref, post, onLoadComplete, onMetadataChange, onError }) => {
   const dialogue = useDialogue ()
   const [framed, setFramed] = useState (false)
 
@@ -39,7 +40,8 @@ const PostEmbed: FC<Props> = ({ ref, post, onLoadComplete, onMetadataChange }) =
 	      width={640}
 	      height={360}
 	      onLoadComplete={onLoadComplete}
-	      onMetadataChange={onMetadataChange}/>)
+	      onMetadataChange={onMetadataChange}
+	      onError={onError}/>)
     }
 
   case 'twitter.com':

frontend/src/components/TopNav.tsx

@@ -128,8 +128,12 @@ const TopNav: FC<Props> = ({ user }) => {
 
   const menu = menuOutline ({ tag, wikiId, user, pathName: location.pathname })
   const visibleMenu = menu.filter ((item): item is MenuVisibleItem => item.visible ?? true)
+  const moreMenu = menu.filter (item =>
+      !(item.visible ?? true)
+      || item.subMenu.filter (subItem => subItem.visible ?? true).length > 0)
   const activeIdx =
       visibleMenu.findIndex (item => location.pathname.startsWith (item.base || item.to))
+  const submenuHeight = moreVsbl ? 40 * moreMenu.length : (activeIdx < 0 ? 0 : 40)
 
   const prevActiveIdxRef = useRef<number> (activeIdx)
 
@@ -240,9 +244,9 @@ const TopNav: FC<Props> = ({ user }) => {
 	  <motion.div
 	      key="submenu-shell"
 	      layout
-	      className="relative hidden md:block overflow-hidden
+	      className="relative z-20 hidden md:block overflow-hidden
 			 bg-yellow-200 dark:bg-red-950"
-	      style={{ height: moreVsbl ? 40 * menu.length : (activeIdx < 0 ? 0 : 40) }}
+	      animate={{ height: submenuHeight }}
 	      onMouseLeave={() => {
 		if (moreVsbl)
 		  setMoreVsbl (false)
@@ -253,7 +257,7 @@ const TopNav: FC<Props> = ({ user }) => {
 	      }}>
 	  {moreVsbl
 	   ? (
-	      menu.map ((item, i) => (
+	      moreMenu.map ((item, i) => (
 		  <div key={i} className="relative h-[40px]">
 		    <div className="absolute inset-0 flex items-center px-3">
 		      <motion.div

frontend/src/lib/api.ts

@@ -64,11 +64,14 @@ export const apiPatch = async <T> (
 ): Promise<T> => apiP ('patch', path, body, opt)
 
 
-export const apiDelete = async (
+export const apiDelete = async <T = void> (
     path: string,
     opt?: Opt,
-): Promise<void> => {
-  await client.delete (path, withUserCode (opt))
+): Promise<T> => {
+  const res = await client.delete (path, withUserCode (opt))
+  if (res.data == null || res.data === '')
+    return undefined as T
+  return toCamel (res.data as Record<string, unknown>, { deep: true }) as T
 }
 
 

frontend/src/types.ts

@@ -226,7 +226,7 @@ export type Theatre = {
 export type TheatreComment =
     | { theatreId:  number
 	no:         number
-	deteled:    false
+	deleted:    false
 	user:       { id: number, name: string } | null
 	content:    string
 	createdAt:  string }
@@ -234,7 +234,7 @@ export type TheatreComment =
 	no:         number
 	deleted:    true
 	user:       { id: number, name: string } | null
-	content     null,
+	content:    null,
 	createdAt:  string }
 
 export type TheatreProgramme = {
@@ -243,6 +243,46 @@ export type TheatreProgramme = {
     post:       Post
     createdAt:  string }
 
+export type TheatreSkipVoteStatus = {
+    votesCount:          number
+    requiredCount:       number
+    watchingUsersCount:  number
+    voted:               boolean }
+
+export type TheatreInfo = {
+    hostFlg:        boolean
+    postId:         number | null
+    postStartedAt:  string | null
+    postElapsedMs:  number | null
+    watchingUsers:  Pick<User, 'id' | 'name'>[]
+    skipVote:       TheatreSkipVoteStatus
+    skipped?:       boolean }
+
+export type TheatreSkipEvent = {
+    id:                 number
+    theatreId:          number
+    post:               Post
+    skippedByUser:      Pick<User, 'id' | 'name'>
+    voters:             Pick<User, 'id' | 'name'>[]
+    tags:               Tag[]
+    programmePosition:  number | null
+    createdAt:          string }
+
+export type TheatrePostWeight = {
+    post:     Post
+    weight:   number
+    penalty:  number
+    tags:     Tag[] }
+
+export type TheatreTagPenalty = {
+    tag:      Tag
+    penalty:  number }
+
+export type TheatrePostSelectionWeights = {
+    tagPenalties:  TheatreTagPenalty[]
+    lightestPosts: TheatrePostWeight[]
+    heaviestPosts: TheatrePostWeight[] }
+
 export type User = {
     id:               number
     name:             string | null