diff --git a/app/channels/application_cable/channel.rb b/app/channels/application_cable/channel.rb
new file mode 100644
index 0000000..d672697
--- /dev/null
+++ b/app/channels/application_cable/channel.rb
@@ -0,0 +1,4 @@
+module ApplicationCable
+  class Channel < ActionCable::Channel::Base
+  end
+end
diff --git a/app/channels/application_cable/connection.rb b/app/channels/application_cable/connection.rb
new file mode 100644
index 0000000..4a43d2f
--- /dev/null
+++ b/app/channels/application_cable/connection.rb
@@ -0,0 +1,37 @@
+module ApplicationCable
+  class Connection < ActionCable::Connection::Base
+    identified_by :current_user
+
+    def connect
+      self.current_user = find_verified_user
+    end
+
+    private
+      def find_verified_user
+        # セッションからuser_idを取得してUserを特定する
+        # 注: セッションストアの設定に依存するが、CookieStore（デフォルト）を想定
+
+        if verified_user = User.find_by(id: session_user_id)
+          verified_user
+        else
+          reject_unauthorized_connection
+        end
+      end
+
+      def session_user_id
+        # RailsのセッションCookieからuser_idを復元する
+        # _dip_front_session は config/initializers/session_store.rb で設定されているキー名、またはデフォルトの _app_session
+        # ここでは汎用的に取得を試みる
+
+        session_key = Rails.application.config.session_options[:key]
+        encrypted_session = cookies.encrypted[session_key]
+
+        if encrypted_session && encrypted_session["user_id"]
+          encrypted_session["user_id"]
+        else
+          # デバッグ用: 認証失敗時はnilを返す
+          nil
+        end
+      end
+  end
+end
diff --git a/app/channels/board_channel.rb b/app/channels/board_channel.rb
new file mode 100644
index 0000000..010c261
--- /dev/null
+++ b/app/channels/board_channel.rb
@@ -0,0 +1,34 @@
+class BoardChannel < ApplicationCable::Channel
+  def subscribed
+    board = Board.find_by(id: params[:board_id])
+
+    unless board
+      reject
+      return
+    end
+
+    # 権限チェック
+    # ゲーム参加者を取得（current_userから）
+    current_participant = board.game.participants.find_by(user: current_user)
+
+    # 参加権限があるか（メンバー、または終了済み、または公開ボード）
+    # コントローラの判定ロジックと合わせる
+    # 共通掲示板は誰でも購読OK（ただしゲーム参加者に限る）
+
+    if board.global?
+      stream_from "board_#{board.id}" if current_participant
+    elsif board.is_public?
+      stream_from "board_#{board.id}" if current_participant
+    elsif board.member?(current_participant)
+      stream_from "board_#{board.id}"
+    elsif board.history_mode?
+      stream_from "board_#{board.id}" if current_participant
+    else
+      reject
+    end
+  end
+
+  def unsubscribed
+    # Any cleanup needed when channel is unsubscribed
+  end
+end
diff --git a/app/controllers/board_memberships_controller.rb b/app/controllers/board_memberships_controller.rb
new file mode 100644
index 0000000..65f4974
--- /dev/null
+++ b/app/controllers/board_memberships_controller.rb
@@ -0,0 +1,66 @@
+class BoardMembershipsController < ApplicationController
+  before_action :require_login
+  before_action :set_game
+  before_action :set_board
+  before_action :set_current_participant
+
+  def create
+    # メンバー追加処理
+    unless @board.negotiation? && @board.member?(@current_participant)
+      return redirect_to game_board_path(@game, @board), alert: "権限がありません"
+    end
+
+    target_participant_id = params[:participant_id]
+
+    # 重複チェック（既に参加しているか）
+    if @board.board_memberships.where(participant_id: target_participant_id, left_at: nil).exists?
+      return redirect_to game_board_path(@game, @board), alert: "そのプレイヤーは既に参加しています"
+    end
+
+    # 退出済みの場合は再参加（left_atをクリア）
+    membership = @board.board_memberships.find_by(participant_id: target_participant_id)
+    if membership
+      membership.update!(left_at: nil, joined_at: Time.current)
+    else
+      @board.board_memberships.create!(participant_id: target_participant_id, joined_at: Time.current)
+    end
+
+    # メンバー構成が変わったので、他の掲示板と重複していないかチェックが必要だが、
+    # モデルのバリデーションは「作成時」を想定しているため、ここでは簡易チェックに留めるか、
+    # あるいはバリデーションエラーをハンドリングする。
+    # ここではsave成功/失敗で判断
+
+    redirect_to game_board_path(@game, @board), notice: "メンバーを追加しました"
+  rescue ActiveRecord::RecordInvalid => e
+    redirect_to game_board_path(@game, @board), alert: "メンバー追加に失敗しました: #{e.message}"
+  end
+
+  def leave
+    # 退出処理
+    unless @board.negotiation? && @board.member?(@current_participant)
+      return redirect_to game_board_path(@game, @board), alert: "退出できません"
+    end
+
+    membership = @board.board_memberships.find_by(participant: @current_participant)
+    if membership
+      membership.leave!
+      redirect_to game_boards_path(@game), notice: "掲示板から退出しました"
+    else
+      redirect_to game_board_path(@game, @board), alert: "退出に失敗しました"
+    end
+  end
+
+  private
+
+  def set_game
+    @game = Game.find(params[:game_id])
+  end
+
+  def set_board
+    @board = @game.boards.find(params[:board_id])
+  end
+
+  def set_current_participant
+    @current_participant = @game.participants.find_by(user: current_user)
+  end
+end
diff --git a/app/controllers/board_posts_controller.rb b/app/controllers/board_posts_controller.rb
new file mode 100644
index 0000000..d9a6e51
--- /dev/null
+++ b/app/controllers/board_posts_controller.rb
@@ -0,0 +1,47 @@
+class BoardPostsController < ApplicationController
+  before_action :require_login
+  before_action :set_game
+  before_action :set_board
+  before_action :set_current_participant
+
+  def create
+    # 参加チェック
+    unless @board.member?(@current_participant) && @game.status == "in_progress"
+      return redirect_to game_board_path(@game, @board), alert: "投稿権限がありません"
+    end
+
+    @post = @board.board_posts.new(post_params)
+    @post.participant = @current_participant
+
+    # フェーズ情報の付与
+    # 最新のターン情報を取得してセットする
+    latest_turn = @game.turns.order(number: :desc).first
+    if latest_turn
+      @post.phase = latest_turn.phase
+    end
+
+    if @post.save
+      redirect_to game_board_path(@game, @board) # noticeはチャット的にうるさいので省略
+    else
+      redirect_to game_board_path(@game, @board), alert: "投稿に失敗しました"
+    end
+  end
+
+  private
+
+  def set_game
+    @game = Game.find(params[:game_id])
+  end
+
+  def set_board
+    @board = @game.boards.find(params[:board_id])
+  end
+
+  def set_current_participant
+    @current_participant = @game.participants.find_by(user: current_user)
+  end
+
+  def post_params
+    params.require(:board_post).permit(:body)
+  end
+end
diff --git a/app/controllers/board_proposals_controller.rb b/app/controllers/board_proposals_controller.rb
new file mode 100644
index 0000000..8d5d4cf
--- /dev/null
+++ b/app/controllers/board_proposals_controller.rb
@@ -0,0 +1,71 @@
+class BoardProposalsController < ApplicationController
+  before_action :require_login
+  before_action :set_game
+  before_action :set_board
+  before_action :set_current_participant
+
+  def create
+    unless @board.member?(@current_participant)
+      return redirect_to game_board_path(@game, @board), alert: "権限がありません"
+    end
+
+    @proposal = @board.board_proposals.new(proposal_params)
+    @proposal.proposer = @current_participant
+    @proposal.status = "pending"
+
+    # フェーズ情報の保存
+    latest_turn = @game.turns.max_by(&:number)
+    if latest_turn
+      @proposal.phase = latest_turn.phase
+    else
+      @proposal.phase = "S1901M" # 初期値
+    end
+
+    if @proposal.save
+      redirect_to game_board_path(@game, @board), notice: "提案を作成しました"
+    else
+      redirect_to game_board_path(@game, @board), alert: "提案の作成に失敗しました"
+    end
+  end
+
+  def update
+    @proposal = @board.board_proposals.find(params[:id])
+
+    # 承認・拒否権限：
+    # 提案者本人以外が承認/拒否できるべきか、あるいは全員できるべきか？
+    # 通常は「相手」が承認するものだが、多国間の場合は？
+    # ここでは「メンバーであれば誰でもステータス変更可能」とする（簡易実装）
+    # ただし、提案者本人が自分で承認するのは変なので、他者のみとするのがベター
+
+    unless @board.member?(@current_participant)
+      return redirect_to game_board_path(@game, @board), alert: "権限がありません"
+    end
+
+    new_status = params[:board_proposal][:status]
+    if %w[accepted rejected].include?(new_status)
+      @proposal.update!(status: new_status)
+      # ログにも残す（投稿として自動投稿しても良いが、今回はステータス変更のみ）
+      redirect_to game_board_path(@game, @board), notice: "提案を#{new_status == 'accepted' ? '承認' : '拒否'}しました"
+    else
+      redirect_to game_board_path(@game, @board), alert: "不正なステータスです"
+    end
+  end
+
+  private
+
+  def set_game
+    @game = Game.find(params[:game_id])
+  end
+
+  def set_board
+    @board = @game.boards.find(params[:board_id])
+  end
+
+  def set_current_participant
+    @current_participant = @game.participants.find_by(user: current_user)
+  end
+
+  def proposal_params
+    params.require(:board_proposal).permit(:body)
+  end
+end
diff --git a/app/controllers/boards_controller.rb b/app/controllers/boards_controller.rb
new file mode 100644
index 0000000..111e572
--- /dev/null
+++ b/app/controllers/boards_controller.rb
@@ -0,0 +1,186 @@
+class BoardsController < ApplicationController
+  before_action :require_login
+  before_action :set_game
+  before_action :set_board, only: [ :show, :toggle_public ]
+
+  def index
+    # 参加中の掲示板（共通掲示板含む）を取得
+    # ゲーム終了後は履歴モードとして、過去に参加していた掲示板もすべて表示
+    @current_participant = @game.participants.find_by(user: current_user)
+
+    # マップ表示用：各国がどの掲示板（交渉）を持っているかのデータを作成
+    # { "FRANCE" => ["GERMANY", "ENGLAND"], ... } のような形式でビューに渡す
+    @diplomacy_matrix = build_diplomacy_matrix
+
+    if @game.status == "finished"
+      # 履歴モード：かつて参加していた掲示板をすべて表示
+      # （共通掲示板は全員参加扱いなので含む）
+      @boards = @game.boards.select { |b| b.member?(@current_participant) || b.global? }
+                            .sort_by { |b| [ b.global? ? 0 : 1, b.created_at ] }
+    else
+      return redirect_to game_path(@game), alert: "参加者ではないためアクセスできません" unless @current_participant
+
+      # 進行中：参加中の掲示板のみ
+      @boards = @current_participant.boards.includes(:participants, :board_posts).order(created_at: :desc)
+      # 共通掲示板がまだ紐付いていない場合のフォールバック（通常は作成時に紐づくはずだが念の為）
+      global_board = @game.boards.global.first
+      if global_board && !@boards.include?(global_board)
+        # 表示上追加するが、DBには保存しない（閲覧時に参加処理をする作りも考えられるが、createタイミングで保証する前提）
+        @boards = [ global_board ] + @boards
+      end
+      # 先頭に共通掲示板を持ってくる
+      @boards = @boards.sort_by { |b| b.global? ? 0 : 1 }
+    end
+  end
+
+  def show
+    @current_participant = @game.participants.find_by(user: current_user)
+
+    # アクセス制御
+    # アクセス制御
+    access_allowed = false
+
+    if @board.global?
+      # 共通掲示板はゲーム参加者なら誰でもアクセス可能
+      # 未読管理のためにメンバーシップがない場合は作成する
+      access_allowed = true
+      unless @board.board_memberships.exists?(participant: @current_participant)
+        @board.board_memberships.create(participant: @current_participant, joined_at: Time.current)
+      end
+    elsif @board.member?(@current_participant)
+      access_allowed = true
+    elsif @game.status == "finished"
+      # ゲーム終了後は、元メンバーならアクセス可能（共通掲示板は上記でカバー済み）
+      is_past_member = @board.board_memberships.exists?(participant: @current_participant)
+      access_allowed = is_past_member
+    elsif @board.is_public?
+      # 公開掲示板は誰でも閲覧可能
+      access_allowed = true
+    end
+
+    unless access_allowed
+      return redirect_to game_boards_path(@game), alert: "権限がありません"
+    end
+
+    # 既読更新
+    if @current_participant && @board.active_memberships.exists?(participant: @current_participant)
+      last_post = @board.board_posts.last
+      if last_post
+        membership = @board.board_memberships.find_by(participant: @current_participant)
+        membership.mark_read!(last_post.id)
+      end
+    end
+
+    @posts = @board.board_posts.includes(:participant).order(created_at: :desc)
+    @new_post = BoardPost.new
+    @new_proposal = BoardProposal.new
+    @active_members = @board.active_memberships.includes(:participant).map(&:participant)
+
+    # メンバー追加用：招待可能なプレイヤー一覧（自分と既に参加している人を除く）
+    if @board.negotiation? && !@board.history_mode?
+      existing_member_ids = @board.board_memberships.where(left_at: nil).pluck(:participant_id)
+      @candidates = @game.participants.where.not(id: existing_member_ids).where.not(power: nil)
+    end
+  end
+
+  def new
+    @board = Board.new(board_type: "negotiation")
+    @current_participant = @game.participants.find_by(user: current_user)
+    # 自分以外の参加者一覧
+    @participants = @game.participants.where.not(id: @current_participant.id).where.not(power: nil)
+  end
+
+  def create
+    @current_participant = @game.participants.find_by(user: current_user)
+
+    # トランザクションで掲示板作成とメンバー追加を一括実行
+    ActiveRecord::Base.transaction do
+      @board = @game.boards.new(board_params)
+      @board.board_type = "negotiation"
+      @board.created_by_participant_id = @current_participant.id
+
+      if @board.save
+        # 作成者をメンバーに追加
+        @board.board_memberships.create!(participant: @current_participant, joined_at: Time.current)
+
+        # 招待されたメンバーを追加
+        if params[:invited_participant_ids].present?
+          params[:invited_participant_ids].each do |pid|
+            @board.board_memberships.create!(participant_id: pid, joined_at: Time.current)
+          end
+        end
+
+        redirect_to game_board_path(@game, @board), notice: "交渉用掲示板を作成しました"
+      else
+        @participants = @game.participants.where.not(id: @current_participant.id).where.not(power: nil)
+        render :new, status: :unprocessable_entity
+      end
+    end
+  rescue ActiveRecord::RecordInvalid
+    @participants = @game.participants.where.not(id: @current_participant.id).where.not(power: nil)
+    render :new, status: :unprocessable_entity
+  end
+
+  def toggle_public
+    # 公開宣言機能（追加提案）
+    @current_participant = @game.participants.find_by(user: current_user)
+    unless @board.member?(@current_participant)
+      return redirect_to game_board_path(@game, @board), alert: "権限がありません"
+    end
+
+    @board.update(is_public: !@board.is_public)
+    status = @board.is_public ? "公開" : "非公開"
+    redirect_to game_board_path(@game, @board), notice: "掲示板を#{status}に設定しました"
+  end
+
+  private
+
+  def set_game
+    @game = Game.find(params[:game_id])
+  end
+
+  def set_board
+    @board = @game.boards.find(params[:id])
+  end
+
+  def board_params
+    # パラメータは特にないが、将来的にタイトルなど追加するかも
+    params.fetch(:board, {}).permit(:is_public)
+  end
+
+  def build_diplomacy_matrix
+    # 外交関係マップ構築
+    # Matrix: { "FRANCE" => { "GERMANY" => true, "ENGLAND" => false }, ... }
+    # 全組み合わせの初期化
+    powers = @game.participants.where.not(power: nil).pluck(:power)
+    matrix = {}
+    powers.each { |p| matrix[p] = [] }
+
+    # 参加中の全掲示板を走査（自分が参加していないものも含めたいが、
+    # DB設計上 board_memberships を見る必要がある）
+    # is_publicなもの、または自分が参加しているものについて情報を開示？
+    # 仕様書には「どの国とどの国が掲示板を持っているか」とあるが、
+    # 秘密交渉なので、本来は「自分が見えている範囲」あるいは「公開宣言されたもの」のみ？
+    # ここでは「自分が参加している掲示板」および「公開された掲示板」の関係を表示する。
+
+    visible_boards = @game.boards.negotiation.includes(:participants)
+
+    visible_boards.each do |board|
+      # アクセス権チェック（簡易）
+      is_member = board.board_memberships.exists?(participant: @current_participant, left_at: nil)
+      next unless is_member || board.is_public || @game.status == "finished"
+
+      # メンバー間のリンクを作成
+      members = board.participants.pluck(:power)
+      members.each do |p1|
+        members.each do |p2|
+          next if p1 == p2
+          matrix[p1] ||= []
+          matrix[p1] << p2 unless matrix[p1].include?(p2)
+        end
+      end
+    end
+
+    matrix
+  end
+end
diff --git a/app/javascript/controllers/board_channel_controller.js b/app/javascript/controllers/board_channel_controller.js
new file mode 100644
index 0000000..a68d7bc
--- /dev/null
+++ b/app/javascript/controllers/board_channel_controller.js
@@ -0,0 +1,73 @@
+import { Controller } from "@hotwired/stimulus"
+import { createConsumer } from "@rails/actioncable"
+
+export default class extends Controller {
+  static values = {
+    boardId: Number,
+    currentParticipantId: Number
+  }
+
+  connect() {
+    this.channel = createConsumer().subscriptions.create(
+      { channel: "BoardChannel", board_id: this.boardIdValue },
+      {
+        received: (data) => {
+          this._insertMessage(data)
+        }
+      }
+    )
+    this.element.scrollTop = this.element.scrollHeight
+  }
+
+  disconnect() {
+    if (this.channel) {
+      this.channel.unsubscribe()
+    }
+  }
+
+  _insertMessage(data) {
+    const isMe = data.participant_id === this.currentParticipantIdValue
+
+    // 最初の投稿の場合、"まだ投稿がありません"メッセージを消す
+    const noPostsMessage = document.getElementById("no-posts-message")
+    if (noPostsMessage) {
+      noPostsMessage.remove()
+    }
+
+    const html = `
+      <div class="flex ${isMe ? 'justify-end' : 'justify-start'} mb-4 message-item" id="post_${data.post_id}">
+        ${!isMe ? `
+          <div class="flex-shrink-0 mr-3">
+            <span class="inline-flex items-center justify-center h-8 w-8 rounded-full text-xs font-bold border border-gray-300 bg-white text-gray-700 shadow-sm" title="${data.power}">
+              ${data.power ? data.power.substring(0, 2) : '?'}
+            </span>
+          </div>
+        ` : ''}
+
+        <div class="max-w-lg ${isMe ? 'order-1' : 'order-2'}">
+          <div class="flex items-baseline space-x-2 mb-1 ${isMe ? 'justify-end' : 'justify-start'}">
+            ${!isMe ? `<span class="text-xs font-bold text-gray-900">${data.power}</span>` : ''}
+            <span class="text-xs text-gray-500">${data.created_at}</span>
+            ${data.phase ? `<span class="text-xs bg-gray-100 px-1 rounded text-gray-600 border border-gray-200">${data.phase}</span>` : ''}
+          </div>
+          
+          <div class="px-4 py-2 rounded-lg shadow-sm text-sm ${isMe ? 'bg-indigo-600 text-white rounded-br-none' : 'bg-white border border-gray-200 text-gray-900 rounded-bl-none'}">
+            <div>${this._escapeHtml(data.body).replace(/\n/g, '<br>')}</div>
+          </div>
+        </div>
+      </div>
+    `
+
+    this.element.insertAdjacentHTML('afterbegin', html)
+    // this.element.scrollTop = 0 // 必要ならトップへスクロール
+  }
+
+  _escapeHtml(unsafe) {
+    return unsafe
+      .replace(/&/g, "&amp;")
+      .replace(/</g, "&lt;")
+      .replace(/>/g, "&gt;")
+      .replace(/"/g, "&quot;")
+      .replace(/'/g, "&#039;")
+  }
+}
diff --git a/app/models/board.rb b/app/models/board.rb
new file mode 100644
index 0000000..0e80b4a
--- /dev/null
+++ b/app/models/board.rb
@@ -0,0 +1,61 @@
+class Board < ApplicationRecord
+  belongs_to :game
+  belongs_to :creator, class_name: "Participant",
+             foreign_key: "created_by_participant_id", optional: true
+  has_many :board_memberships, dependent: :destroy
+  has_many :active_memberships, -> { where(left_at: nil) },
+           class_name: "BoardMembership"
+  has_many :participants, through: :board_memberships
+  has_many :board_posts, dependent: :destroy
+  has_many :board_proposals, dependent: :destroy
+
+  enum :board_type, { global: "global", negotiation: "negotiation" }
+
+  validate :no_duplicate_member_combination, if: :negotiation?
+
+  # メンバーかどうか判定（退出済みはfalse）
+  def member?(participant)
+    return false unless participant
+    board_memberships.exists?(participant_id: participant.id, left_at: nil)
+  end
+
+  # 履歴モードかどうか（ゲーム終了後は常にtrue）
+  def history_mode?
+    game.status == "finished"
+  end
+
+  # 指定した参加者の未読件数を取得
+  def unread_count_for(participant)
+    return 0 unless participant
+
+    membership = board_memberships.find_by(participant_id: participant.id)
+    # メンバーでない、または退出済みの場合は未読なしとする（あるいは全件とするか要検討だが、一旦0）
+    return 0 unless membership && membership.active?
+
+    last_id = membership.last_read_post_id || 0
+    board_posts.where("id > ?", last_id).count
+  end
+
+  private
+
+  def no_duplicate_member_combination
+    # 新規作成時のみチェック（更新時はメンバー変動があるため別途考慮が必要だが、今回は作成時のみ想定）
+    # ただしメンバー追加時にもチェックが必要になる可能性があるため、Boardモデルのバリデーションとして定義
+
+    # 比較対象のメンバーIDリスト（ソート済み）
+    current_member_ids = board_memberships.map(&:participant_id).sort
+
+    # 同じゲーム内の他の交渉用掲示板を検索
+    game.boards.negotiation.where.not(id: id).each do |other_board|
+      # 退出者を含めた全メンバー構成で比較するか、アクティブメンバーのみで比較するか
+      # 仕様書「同じメンバー構成の掲示板は作成できない」
+      # ここでは「現在参加しているメンバー」の構成が重複しないようにする
+      other_member_ids = other_board.board_memberships.where(left_at: nil).pluck(:participant_id).sort
+
+      if other_member_ids == current_member_ids
+        errors.add(:base, "同じメンバー構成の掲示板がすでに存在します")
+        return
+      end
+    end
+  end
+end
diff --git a/app/models/board_membership.rb b/app/models/board_membership.rb
new file mode 100644
index 0000000..7bd77fc
--- /dev/null
+++ b/app/models/board_membership.rb
@@ -0,0 +1,21 @@
+class BoardMembership < ApplicationRecord
+  belongs_to :board
+  belongs_to :participant
+
+  # 参加中かどうか（退出していない）
+  def active?
+    left_at.nil?
+  end
+
+  # 退出処理
+  def leave!
+    update!(left_at: Time.current)
+  end
+
+  # 既読位置を更新
+  def mark_read!(post_id)
+    # 既存の既読位置より新しい場合のみ更新（巻き戻り防止）
+    # ただし今回は単純に最新をセットする形で良い
+    update!(last_read_post_id: post_id)
+  end
+end
diff --git a/app/models/board_post.rb b/app/models/board_post.rb
new file mode 100644
index 0000000..106613e
--- /dev/null
+++ b/app/models/board_post.rb
@@ -0,0 +1,26 @@
+class BoardPost < ApplicationRecord
+  belongs_to :board
+  belongs_to :participant
+
+  validates :body, presence: true
+
+  # 作成後にAction Cableで配信
+  after_create_commit :broadcast_to_board
+
+  private
+
+  def broadcast_to_board
+    # ボードごとのチャンネルに配信
+    ActionCable.server.broadcast(
+      "board_#{board_id}",
+      {
+        post_id: id,
+        participant_id: participant.id,
+        power: participant.power, # 国名
+        body: body,
+        phase: phase, # フェーズ情報
+        created_at: created_at.in_time_zone("Asia/Tokyo").strftime("%Y-%m-%d %H:%M")
+      }
+    )
+  end
+end
diff --git a/app/models/board_proposal.rb b/app/models/board_proposal.rb
new file mode 100644
index 0000000..7d2db4c
--- /dev/null
+++ b/app/models/board_proposal.rb
@@ -0,0 +1,9 @@
+class BoardProposal < ApplicationRecord
+  belongs_to :board
+  belongs_to :proposer, class_name: "Participant",
+             foreign_key: "proposer_participant_id"
+
+  enum :status, { pending: "pending", accepted: "accepted", rejected: "rejected" }
+
+  validates :body, presence: true
+end
diff --git a/app/models/game.rb b/app/models/game.rb
index a48820f..3a58e50 100644
--- a/app/models/game.rb
+++ b/app/models/game.rb
@@ -2,6 +2,8 @@ class Game < ApplicationRecord
   has_many :turns, dependent: :destroy
   has_many :participants, dependent: :destroy
   has_many :users, through: :participants
+  has_many :boards, dependent: :destroy
+  has_one :latest_turn, -> { order(number: :desc) }, class_name: "Turn"
 
   # パスワード保護
   has_secure_password :password, validations: false
@@ -26,6 +28,9 @@ class Game < ApplicationRecord
   # ターンスケジュールバリデーション
   validate :validate_turn_schedule
 
+  # コールバック
+  after_create :create_global_board
+
   # ヘルパーメソッド
   def password_protected?
     password_digest.present?
@@ -162,4 +167,8 @@ class Game < ApplicationRecord
       errors.add(:turn_schedule, "は0〜23の数値をカンマ区切りで入力してください（例: 0,18）")
     end
   end
+
+  def create_global_board
+    boards.create!(board_type: "global", is_public: true)
+  end
 end
diff --git a/app/models/participant.rb b/app/models/participant.rb
index 53013d4..3329e3d 100644
--- a/app/models/participant.rb
+++ b/app/models/participant.rb
@@ -1,19 +1,23 @@
 class Participant < ApplicationRecord
   belongs_to :user
   belongs_to :game
-  
+
+  has_many :board_memberships, dependent: :destroy
+  has_many :boards, through: :board_memberships
+  has_many :board_posts, dependent: :destroy
+
   # バリデーション
-  validates :user_id, uniqueness: { 
+  validates :user_id, uniqueness: {
     scope: :game_id,
     message: "既にこのゲームに参加しています"
   }
-  
-  validates :power, uniqueness: { 
+
+  validates :power, uniqueness: {
     scope: :game_id,
     message: "この国は既に選択されています"
   }, allow_nil: true
-  
-  validates :power, inclusion: { 
+
+  validates :power, inclusion: {
     in: %w[AUSTRIA ENGLAND FRANCE GERMANY ITALY RUSSIA TURKEY],
     message: "無効な国です"
   }, allow_nil: true
diff --git a/app/views/boards/_post.html.erb b/app/views/boards/_post.html.erb
new file mode 100644
index 0000000..3b8e4ce
--- /dev/null
+++ b/app/views/boards/_post.html.erb
@@ -0,0 +1,27 @@
+<% is_me = post.participant == current_participant %>
+<div class="flex <%= is_me ? 'justify-end' : 'justify-start' %> mb-4 message-item" id="post_<%= post.id %>">
+  <% unless is_me %>
+    <div class="flex-shrink-0 mr-3">
+      <!-- アバター代わりの国名バッジ -->
+      <span class="inline-flex items-center justify-center h-8 w-8 rounded-full text-xs font-bold border border-gray-300 bg-white text-gray-700 shadow-sm" title="<%= post.participant.power %>">
+        <%= post.participant.power ? post.participant.power[0..1] : '?' %>
+      </span>
+    </div>
+  <% end %>
+
+  <div class="max-w-lg <%= is_me ? 'order-1' : 'order-2' %>">
+    <div class="flex items-baseline space-x-2 mb-1 <%= is_me ? 'justify-end' : 'justify-start' %>">
+      <% unless is_me %>
+        <span class="text-xs font-bold text-gray-900"><%= post.participant.power %></span>
+      <% end %>
+      <span class="text-xs text-gray-500"><%= l post.created_at, format: :short %></span>
+      <% if post.phase.present? %>
+        <span class="text-xs bg-gray-100 px-1 rounded text-gray-600 border border-gray-200"><%= post.phase %></span>
+      <% end %>
+    </div>
+    
+    <div class="px-4 py-2 rounded-lg shadow-sm text-sm <%= is_me ? 'bg-indigo-600 text-white rounded-br-none' : 'bg-white border border-gray-200 text-gray-900 rounded-bl-none' %>">
+      <%= simple_format(h(post.body), {}, wrapper_tag: "div") %>
+    </div>
+  </div>
+</div>
diff --git a/app/views/boards/index.html.erb b/app/views/boards/index.html.erb
new file mode 100644
index 0000000..950546a
--- /dev/null
+++ b/app/views/boards/index.html.erb
@@ -0,0 +1,194 @@
+<div class="max-w-7xl mx-auto px-4 sm:px-6 lg:px-8 py-8">
+  <%= render "games/header", game: @game, display_turn: @game.latest_turn, current_participant: @current_participant, hide_controls: true %>
+
+  <div class="md:flex md:items-center md:justify-between mb-6">
+    <div class="flex-1 min-w-0">
+      <h2 class="text-2xl font-bold leading-7 text-gray-900 sm:text-3xl sm:truncate">
+        外交・交渉掲示板
+      </h2>
+      <p class="mt-1 text-sm text-gray-500">
+        他国との秘密交渉や全体へのアナウンスを行います。
+      </p>
+    </div>
+    <div class="mt-4 flex md:mt-0 md:ml-4">
+      <%= link_to game_path(@game), class: "inline-flex items-center px-4 py-2 border border-gray-300 rounded-md shadow-sm text-sm font-medium text-gray-700 bg-white hover:bg-gray-50 focus:outline-none focus:ring-2 focus:ring-offset-2 focus:ring-indigo-500" do %>
+        <i class="fa-solid fa-map mr-2"></i> マップに戻る
+      <% end %>
+      
+      <% if @game.status == 'in_progress' %>
+        <%= link_to new_game_board_path(@game), class: "ml-3 inline-flex items-center px-4 py-2 border border-transparent rounded-md shadow-sm text-sm font-medium text-white bg-indigo-600 hover:bg-indigo-700 focus:outline-none focus:ring-2 focus:ring-offset-2 focus:ring-indigo-500" do %>
+          <i class="fa-solid fa-plus mr-2"></i> 新しい掲示板を作成
+        <% end %>
+      <% end %>
+    </div>
+  </div>
+
+  <% if @game.status == 'finished' %>
+    <div class="mb-6 bg-yellow-50 border-l-4 border-yellow-400 p-4">
+      <div class="flex">
+        <div class="flex-shrink-0">
+          <i class="fa-solid fa-history text-yellow-400"></i>
+        </div>
+        <div class="ml-3">
+          <p class="text-sm text-yellow-700">
+            このゲームは終了しています。すべての掲示板は履歴モード（閲覧専用）です。
+          </p>
+        </div>
+      </div>
+    </div>
+  <% end %>
+
+  <div class="grid grid-cols-1 lg:grid-cols-3 gap-6">
+    <!-- 左カラム: 掲示板一覧 -->
+    <div class="lg:col-span-2 space-y-6">
+      
+      <!-- 掲示板リスト -->
+      <div class="bg-white shadow overflow-hidden sm:rounded-md">
+        <ul role="list" class="divide-y divide-gray-200">
+          <% if @boards.empty? %>
+            <li class="px-4 py-4 sm:px-6 text-center text-gray-500 text-sm">
+              掲示板がありません
+            </li>
+          <% else %>
+            <% @boards.each do |board| %>
+              <li>
+                <%= link_to game_board_path(@game, board), class: "block hover:bg-gray-50" do %>
+                  <div class="px-4 py-4 sm:px-6">
+                    <div class="flex items-center justify-between">
+                      <div class="flex items-center">
+                        <% if board.global? %>
+                          <span class="flex-shrink-0 inline-flex items-center px-2 py-0.5 rounded text-xs font-medium bg-blue-100 text-blue-800 mr-3">
+                            <i class="fa-solid fa-earth-americas mr-1"></i> 共通
+                          </span>
+                          <p class="text-sm font-medium text-indigo-600 truncate">
+                            Global Board (全体掲示板)
+                          </p>
+                        <% else %>
+                          <span class="flex-shrink-0 inline-flex items-center px-2 py-0.5 rounded text-xs font-medium bg-green-100 text-green-800 mr-3">
+                            <i class="fa-solid fa-handshake mr-1"></i> 交渉
+                          </span>
+                          <p class="text-sm font-medium text-indigo-600 truncate">
+                            <% members = board.participants.map(&:power).compact.sort %>
+                            <%= members.join(' / ') %>
+                          </p>
+                        <% end %>
+                        
+                        <% if board.is_public? %>
+                          <span class="ml-2 inline-flex items-center px-2 py-0.5 rounded text-xs font-medium bg-gray-100 text-gray-800">
+                            <i class="fa-solid fa-bullhorn mr-1"></i> 公開中
+                          </span>
+                        <% end %>
+                      </div>
+                      <div class="ml-2 flex-shrink-0 flex">
+                        <% unread_count = board.unread_count_for(@current_participant) %>
+                        <% if unread_count > 0 %>
+                          <span class="inline-flex items-center px-2.5 py-0.5 rounded-full text-xs font-medium bg-red-100 text-red-800">
+                            <%= unread_count %> 未読
+                          </span>
+                        <% end %>
+                      </div>
+                    </div>
+                    <div class="mt-2 sm:flex sm:justify-between">
+                      <div class="sm:flex">
+                        <p class="flex items-center text-sm text-gray-500">
+                          <% last_post = board.board_posts.last %>
+                          <% if last_post %>
+                            <i class="fa-solid fa-comment-dots flex-shrink-0 mr-1.5 text-gray-400"></i>
+                            <span class="truncate max-w-xs"><%= last_post.body.truncate(30) %></span>
+                            <span class="ml-2 text-xs text-gray-400">- <%= last_post.participant.power %></span>
+                          <% else %>
+                            <span class="text-gray-400">投稿なし</span>
+                          <% end %>
+                        </p>
+                      </div>
+                      <div class="mt-2 flex items-center text-sm text-gray-500 sm:mt-0">
+                        <% if last_post %>
+                          <i class="fa-regular fa-clock flex-shrink-0 mr-1.5 text-gray-400"></i>
+                          <p>
+                            <%= time_ago_in_words(last_post.created_at) %>前
+                          </p>
+                        <% else %>
+                          <p>
+                            作成: <%= l board.created_at, format: :short %>
+                          </p>
+                        <% end %>
+                      </div>
+                    </div>
+                  </div>
+                <% end %>
+              </li>
+            <% end %>
+          <% end %>
+        </ul>
+      </div>
+    </div>
+
+    <!-- 右カラム: 外交関係マップ -->
+    <div class="space-y-6">
+      <div class="bg-white shadow rounded-lg border border-gray-200">
+        <div class="px-4 py-3 bg-gray-50 border-b border-gray-200">
+          <h3 class="text-lg font-medium text-gray-900">外交関係マップ</h3>
+          <p class="text-xs text-gray-500 mt-1">
+            交渉チャンネルを持つ国同士の繋がり（相互のみ表示）
+          </p>
+        </div>
+        <div class="p-4">
+          <!-- 簡易的なマトリックス表示 -->
+          <div class="overflow-x-auto">
+            <table class="min-w-full divide-y divide-gray-200 text-xs">
+              <thead>
+                <tr>
+                  <th class="px-2 py-1"></th>
+                  <% @diplomacy_matrix.keys.sort.each do |power| %>
+                    <th class="px-2 py-1 font-bold text-gray-500 rotate-45 origin-bottom-left transform translate-x-2"><%= power[0..2] %></th>
+                  <% end %>
+                </tr>
+              </thead>
+              <tbody class="divide-y divide-gray-200">
+                <% @diplomacy_matrix.keys.sort.each do |row_power| %>
+                  <tr>
+                    <th class="px-2 py-1 font-bold text-gray-500 text-left"><%= row_power[0..2] %></th>
+                    <% @diplomacy_matrix.keys.sort.each do |col_power| %>
+                      <td class="px-2 py-1 text-center">
+                        <% if row_power == col_power %>
+                          <span class="text-gray-200">-</span>
+                        <% elsif @diplomacy_matrix[row_power]&.include?(col_power) %>
+                          <span class="text-green-600 font-bold">●</span>
+                        <% else %>
+                          <span class="text-gray-200">・</span>
+                        <% end %>
+                      </td>
+                    <% end %>
+                  </tr>
+                <% end %>
+              </tbody>
+            </table>
+          </div>
+          
+          <div class="mt-4 text-xs text-gray-500">
+            <p>※ あなたが参加している掲示板、または公開された掲示板の関係のみ表示されます。</p>
+          </div>
+        </div>
+      </div>
+      
+      <!-- ヒント -->
+      <div class="bg-blue-50 border border-blue-200 rounded-md p-4">
+        <div class="flex">
+          <div class="flex-shrink-0">
+            <i class="fa-solid fa-circle-info text-blue-400"></i>
+          </div>
+          <div class="ml-3">
+            <h3 class="text-sm font-medium text-blue-800">交渉のヒント</h3>
+            <div class="mt-2 text-sm text-blue-700">
+              <ul role="list" class="list-disc pl-5 space-y-1">
+                <li>共通掲示板は全員が見ています。外交方針の発表に使いましょう。</li>
+                <li>特定の国と密約を結ぶには「新しい掲示板を作成」から招待してください。</li>
+                <li>交渉用掲示板の内容は、メンバー以外には秘密です（「公開」設定にしない限り）。</li>
+              </ul>
+            </div>
+          </div>
+        </div>
+      </div>
+    </div>
+  </div>
+</div>
diff --git a/app/views/boards/new.html.erb b/app/views/boards/new.html.erb
new file mode 100644
index 0000000..a43b08e
--- /dev/null
+++ b/app/views/boards/new.html.erb
@@ -0,0 +1,72 @@
+<div class="max-w-2xl mx-auto px-4 sm:px-6 lg:px-8 py-8">
+  <div class="mb-6">
+    <%= link_to game_boards_path(@game), class: "text-gray-500 hover:text-gray-700" do %>
+      <i class="fa-solid fa-arrow-left mr-1"></i> 掲示板一覧に戻る
+    <% end %>
+  </div>
+
+  <div class="bg-white shadow overflow-hidden sm:rounded-lg border border-gray-200">
+    <div class="px-4 py-5 sm:px-6 bg-gray-50 border-b border-gray-200">
+      <h3 class="text-lg leading-6 font-medium text-gray-900">新しい交渉用掲示板を作成</h3>
+      <p class="mt-1 text-sm text-gray-500">
+        交渉したい相手（国）を選択してください。選択した相手とあなただけの秘密の掲示板が作成されます。
+      </p>
+    </div>
+    
+    <div class="px-4 py-5 sm:p-6">
+      <%= form_with model: [@game, @board], local: true, class: "space-y-6" do |f| %>
+        <% if @board.errors.any? %>
+          <div class="rounded-md bg-red-50 p-4 mb-4">
+            <div class="flex">
+              <div class="flex-shrink-0">
+                <i class="fa-solid fa-circle-xmark text-red-400"></i>
+              </div>
+              <div class="ml-3">
+                <h3 class="text-sm font-medium text-red-800">入力内容にエラーがあります</h3>
+                <div class="mt-2 text-sm text-red-700">
+                  <ul role="list" class="list-disc pl-5 space-y-1">
+                    <% @board.errors.full_messages.each do |message| %>
+                      <li><%= message %></li>
+                    <% end %>
+                  </ul>
+                </div>
+              </div>
+            </div>
+          </div>
+        <% end %>
+
+        <div>
+           <label class="text-base font-medium text-gray-900">招待するメンバー</label>
+           <p class="text-sm text-gray-500 mb-3">少なくとも1人以上選択してください。</p>
+           
+           <div class="mt-2 grid grid-cols-1 sm:grid-cols-2 gap-4">
+             <% if @participants.empty? %>
+               <p class="text-sm text-gray-500 italic">招待可能な他のプレイヤーがいません。</p>
+             <% else %>
+               <% @participants.each do |participant| %>
+                 <div class="relative flex items-start py-2 border rounded p-3 hover:bg-gray-50 cursor-pointer">
+                   <div class="min-w-0 flex-1 text-sm">
+                     <label for="participant_<%= participant.id %>" class="font-medium text-gray-700 select-none cursor-pointer flex items-center">
+                       <span class="inline-flex items-center px-2 py-0.5 rounded text-xs font-bold border border-gray-200 mr-2 <%= power_color_class(participant.power) %>">
+                         <%= participant.power %>
+                       </span>
+                       <%= participant.user.username %>
+                     </label>
+                   </div>
+                   <div class="ml-3 flex items-center h-5">
+                     <input id="participant_<%= participant.id %>" name="invited_participant_ids[]" value="<%= participant.id %>" type="checkbox" class="focus:ring-indigo-500 h-4 w-4 text-indigo-600 border-gray-300 rounded">
+                   </div>
+                 </div>
+               <% end %>
+             <% end %>
+           </div>
+        </div>
+
+        <div class="pt-5 border-t border-gray-200 flex justify-end">
+          <%= link_to "キャンセル", game_boards_path(@game), class: "bg-white py-2 px-4 border border-gray-300 rounded-md shadow-sm text-sm font-medium text-gray-700 hover:bg-gray-50 focus:outline-none focus:ring-2 focus:ring-offset-2 focus:ring-indigo-500 mr-3" %>
+          <%= f.submit "掲示板を作成", class: "inline-flex justify-center py-2 px-4 border border-transparent shadow-sm text-sm font-medium rounded-md text-white bg-indigo-600 hover:bg-indigo-700 focus:outline-none focus:ring-2 focus:ring-offset-2 focus:ring-indigo-500" %>
+        </div>
+      <% end %>
+    </div>
+  </div>
+</div>
diff --git a/app/views/boards/show.html.erb b/app/views/boards/show.html.erb
new file mode 100644
index 0000000..62ec4ef
--- /dev/null
+++ b/app/views/boards/show.html.erb
@@ -0,0 +1,221 @@
+<div class="max-w-7xl mx-auto px-4 sm:px-6 lg:px-8 py-8 h-screen-minus-header flex flex-col">
+  <%= render "games/header", game: @game, display_turn: @game.latest_turn, current_participant: @current_participant, hide_controls: true %>
+
+  <!-- ヘッダー -->
+  <div class="md:flex md:items-center md:justify-between mb-4 border-b pb-4">
+    <div class="flex-1 min-w-0">
+      <div class="flex items-center">
+        <%= link_to game_boards_path(@game), class: "mr-4 text-gray-500 hover:text-gray-700" do %>
+          <i class="fa-solid fa-arrow-left"></i>
+        <% end %>
+        
+        <h2 class="text-2xl font-bold leading-7 text-gray-900 sm:text-3xl sm:truncate">
+          <% if @board.global? %>
+            <i class="fa-solid fa-earth-americas text-blue-500 mr-2"></i> Global Board
+          <% else %>
+            <i class="fa-solid fa-handshake text-green-500 mr-2"></i> Negotiation Board
+          <% end %>
+        </h2>
+        
+        <% if @board.is_public? %>
+          <span class="ml-3 inline-flex items-center px-2.5 py-0.5 rounded-full text-xs font-medium bg-gray-100 text-gray-800">
+            <i class="fa-solid fa-bullhorn mr-1"></i> 公開中
+          </span>
+        <% end %>
+        
+        <% if @board.history_mode? %>
+          <span class="ml-3 inline-flex items-center px-2.5 py-0.5 rounded-full text-xs font-medium bg-yellow-100 text-yellow-800">
+            <i class="fa-solid fa-scroll mr-1"></i> 履歴モード
+          </span>
+        <% end %>
+      </div>
+      
+      <div class="mt-1 flex flex-col sm:flex-row sm:flex-wrap sm:mt-0 sm:space-x-6">
+        <div class="mt-2 flex items-center text-sm text-gray-500">
+          <i class="fa-solid fa-users flex-shrink-0 mr-1.5 text-gray-400"></i>
+          メンバー: 
+          <% @active_members.each do |m| %>
+            <span class="ml-1 inline-flex items-center px-2 py-0.5 rounded text-xs font-medium border <%= power_color_class(m.power) %>">
+              <%= m.power %>
+            </span>
+          <% end %>
+        </div>
+      </div>
+    </div>
+    
+    <div class="mt-4 flex md:mt-0 md:ml-4 space-x-2">
+      <!-- 公開設定切り替え (交渉用かつ参加中のみ) -->
+      <% if @board.negotiation? && @board.member?(@current_participant) && !@board.history_mode? %>
+        <%= button_to toggle_public_game_board_path(@game, @board), method: :patch, class: "inline-flex items-center px-3 py-1.5 border border-gray-300 shadow-sm text-sm font-medium rounded text-gray-700 bg-white hover:bg-gray-50 focus:outline-none focus:ring-2 focus:ring-offset-2 focus:ring-indigo-500" do %>
+          <% if @board.is_public? %>
+            <i class="fa-solid fa-lock mr-1"></i> 非公開にする
+          <% else %>
+            <i class="fa-solid fa-bullhorn mr-1"></i> 公開する
+          <% end %>
+        <% end %>
+      <% end %>
+
+      <!-- 退出ボタン (交渉用かつ参加中のみ) -->
+      <% if @board.negotiation? && @board.member?(@current_participant) && !@board.history_mode? %>
+        <%= button_to leave_game_board_board_memberships_path(@game, @board), method: :delete, data: { turbo_confirm: "本当に退出しますか？退出後はこの掲示板に投稿できなくなります。" }, class: "inline-flex items-center px-3 py-1.5 border border-transparent shadow-sm text-sm font-medium rounded text-white bg-red-600 hover:bg-red-700 focus:outline-none focus:ring-2 focus:ring-offset-2 focus:ring-red-500" do %>
+          <i class="fa-solid fa-right-from-bracket mr-1"></i> 退出
+        <% end %>
+      <% end %>
+    </div>
+  </div>
+
+  <div class="flex flex-1 overflow-hidden">
+    <!-- 左: チャットエリア -->
+    <!-- 左: チャットエリア -->
+    <div class="flex-1 flex flex-col bg-white border border-gray-200 rounded-lg shadow-sm mr-4 overflow-hidden">
+      
+      <!-- 投稿フォーム (上部に移動) -->
+      <% if @board.member?(@current_participant) && !@board.history_mode? %>
+        <div class="p-4 bg-gray-50 border-b border-gray-200">
+          <%= form_with model: [@game, @board, @new_post], local: true, class: "flex items-end space-x-2" do |f| %>
+            <div class="flex-1">
+              <%= f.text_area :body, rows: 2, placeholder: "メッセージを入力...", class: "shadow-sm focus:ring-indigo-500 focus:border-indigo-500 block w-full sm:text-sm border-gray-300 rounded-md", required: true %>
+            </div>
+            <button type="submit" class="inline-flex items-center px-4 py-2 border border-transparent shadow-sm text-sm font-medium rounded-md text-white bg-indigo-600 hover:bg-indigo-700 focus:outline-none focus:ring-2 focus:ring-offset-2 focus:ring-indigo-500 h-10">
+              <i class="fa-solid fa-paper-plane"></i>
+            </button>
+          <% end %>
+        </div>
+      <% elsif @board.history_mode? %>
+        <div class="p-4 bg-gray-100 border-b border-gray-200 text-center text-gray-500 text-sm">
+          履歴モードのため投稿できません
+        </div>
+      <% else %>
+        <div class="p-4 bg-gray-100 border-b border-gray-200 text-center text-gray-500 text-sm">
+          この掲示板には参加していません
+        </div>
+      <% end %>
+
+      <!-- メッセージリスト -->
+      <div id="board-posts" 
+           class="flex-1 p-4 overflow-y-auto space-y-4" 
+           data-controller="board-channel" 
+           data-board-channel-board-id-value="<%= @board.id %>"
+           data-board-channel-current-participant-id-value="<%= @current_participant&.id %>">
+        <% if @posts.empty? %>
+          <div class="text-center text-gray-400 py-10" id="no-posts-message">
+            <p>まだ投稿がありません。最初のメッセージを投稿しましょう。</p>
+          </div>
+        <% else %>
+          <% @posts.each do |post| %>
+            <%= render partial: "post", locals: { post: post, current_participant: @current_participant } %>
+          <% end %>
+        <% end %>
+      </div>
+      
+    </div>
+
+    <!-- 右: サイドパネル（メンバー管理・提案） -->
+    <div class="w-80 flex flex-col space-y-4 overflow-y-auto">
+      
+      <!-- 提案 (Proposals) -->
+      <% if @board.negotiation? %>
+        <div class="bg-white border border-gray-200 rounded-lg shadow-sm overflow-hidden">
+          <div class="px-3 py-2 bg-gray-50 border-b border-gray-200 font-medium text-sm text-gray-700">
+            条約・提案
+          </div>
+          <div class="p-3 space-y-3">
+            <% @board.board_proposals.order(created_at: :desc).each do |proposal| %>
+              <div class="border rounded p-2 text-sm <%= proposal.status == 'accepted' ? 'bg-green-50 border-green-200' : (proposal.status == 'rejected' ? 'bg-red-50 border-red-200' : 'bg-white border-gray-200') %>">
+                <div class="flex justify-between items-start mb-1">
+                  <div>
+                    <span class="font-bold text-xs mr-1"><%= proposal.proposer.power %></span>
+                    <% if proposal.phase %>
+                      <span class="text-xs bg-gray-100 text-gray-500 px-1 rounded border border-gray-200"><%= proposal.phase %></span>
+                    <% end %>
+                  </div>
+                  <span class="text-xs text-gray-400"><%= l proposal.created_at, format: :short %></span>
+                </div>
+                <p class="mb-2"><%= proposal.body %></p>
+                
+                <div class="flex justify-between items-center">
+                  <span class="text-xs font-medium px-2 py-0.5 rounded
+                    <%= case proposal.status
+                        when 'pending' then 'bg-yellow-100 text-yellow-800'
+                        when 'accepted' then 'bg-green-100 text-green-800'
+                        when 'rejected' then 'bg-red-100 text-red-800'
+                        end %>">
+                    <%= proposal.status.upcase %>
+                  </span>
+                  
+                  <% if proposal.pending? && @board.member?(@current_participant) && !@board.history_mode? %>
+                    <div class="flex space-x-1">
+                      <%= button_to "承認", game_board_board_proposal_path(@game, @board, proposal, board_proposal: { status: 'accepted' }), method: :patch, class: "text-xs bg-green-100 hover:bg-green-200 text-green-800 px-2 py-1 rounded" %>
+                      <%= button_to "拒否", game_board_board_proposal_path(@game, @board, proposal, board_proposal: { status: 'rejected' }), method: :patch, class: "text-xs bg-red-100 hover:bg-red-200 text-red-800 px-2 py-1 rounded" %>
+                    </div>
+                  <% end %>
+                </div>
+              </div>
+            <% end %>
+
+            <% if @board.member?(@current_participant) && !@board.history_mode? %>
+              <div class="mt-2 pt-2 border-t text-center">
+                <button type="button" onclick="document.getElementById('new-proposal-form').classList.toggle('hidden')" class="text-xs text-indigo-600 hover:text-indigo-800">
+                  + 新しい提案を作成
+                </button>
+                <div id="new-proposal-form" class="hidden mt-2">
+                  <%= form_with model: [@game, @board, @new_proposal], local: true do |f| %>
+                    <%= f.text_area :body, rows: 2, class: "w-full text-xs border-gray-300 rounded mb-2", placeholder: "提案内容 (例: 1901秋冬は不可侵)" %>
+                    <%= f.submit "提案する", class: "w-full bg-indigo-600 text-white text-xs py-1 rounded hover:bg-indigo-700" %>
+                  <% end %>
+                </div>
+              </div>
+            <% end %>
+          </div>
+        </div>
+      <% end %>
+
+      <!-- メンバー招待 -->
+      <% if @board.negotiation? && @board.member?(@current_participant) && !@board.history_mode? %>
+        <div class="bg-white border border-gray-200 rounded-lg shadow-sm overflow-hidden">
+          <div class="px-3 py-2 bg-gray-50 border-b border-gray-200 font-medium text-sm text-gray-700">
+            メンバー追加
+          </div>
+          <div class="p-3">
+            <% if @candidates.present? %>
+              <%= form_with url: game_board_board_memberships_path(@game, @board), local: true do |f| %>
+                <div class="flex space-x-2">
+                  <%= f.collection_select :participant_id, @candidates, :id, :power, { prompt: "国を選択" }, { class: "block w-full text-xs border-gray-300 rounded" } %>
+                  <%= f.submit "招待", class: "bg-indigo-600 text-white text-xs px-3 py-1 rounded hover:bg-indigo-700" %>
+                </div>
+              <% end %>
+            <% else %>
+              <p class="text-xs text-gray-500">招待可能なプレイヤーがいません</p>
+            <% end %>
+          </div>
+        </div>
+      <% end %>
+
+      <!-- メンバー一覧 -->
+      <div class="bg-white border border-gray-200 rounded-lg shadow-sm overflow-hidden">
+        <div class="px-3 py-2 bg-gray-50 border-b border-gray-200 font-medium text-sm text-gray-700">
+          参加メンバー
+        </div>
+        <ul class="divide-y divide-gray-200">
+          <% @board.board_memberships.includes(:participant).each do |membership| %>
+            <li class="px-3 py-2 flex items-center justify-between text-sm">
+              <div class="flex items-center">
+                <span class="<%= 'line-through text-gray-400' if membership.left_at %>">
+                  <%= membership.participant.power %>
+                </span>
+                <% if membership.participant.user == current_user %>
+                  <span class="ml-1 text-xs text-indigo-500">(YOU)</span>
+                <% end %>
+              </div>
+              <% if membership.left_at %>
+                <span class="text-xs text-red-500">退出済</span>
+              <% end %>
+            </li>
+          <% end %>
+        </ul>
+      </div>
+
+    </div>
+  </div>
+</div>
+
diff --git a/app/views/games/_header.html.erb b/app/views/games/_header.html.erb
new file mode 100644
index 0000000..9d392c3
--- /dev/null
+++ b/app/views/games/_header.html.erb
@@ -0,0 +1,133 @@
+<div class="mb-6 flex items-center justify-between">
+  <div>
+    <h1 class="text-3xl font-bold text-gray-900"><%= h(game.title) %></h1>
+    <% if game.memo.present? %>
+      <p class="mt-1 text-sm text-gray-500"><%= h(game.memo) %></p>
+    <% end %>
+    <div class="mt-2 flex items-center space-x-4 text-sm text-gray-600">
+      <span class="inline-flex items-center px-2.5 py-0.5 rounded-full text-xs font-medium
+        <%= game.solo_mode? ? 'bg-purple-100 text-purple-800' : 'bg-blue-100 text-blue-800' %>">
+        <%= game.solo_mode? ? 'ソロモード' : 'マルチプレイヤーモード' %>
+      </span>
+      <% if game.administrator %>
+        <span>管理者: <%= h(game.administrator.username) %></span>
+      <% end %>
+      <span>状態: <%= game.status %></span>
+    </div>
+    <% if game.year_limit.present? || game.victory_sc_count != 18 || game.scoring_system != "none" || game.auto_turn? %>
+      <div class="mt-2 flex flex-wrap items-center gap-2 text-xs">
+        <span class="font-medium text-gray-500">ハウスルール:</span>
+        <% if game.auto_turn? %>
+          <span class="inline-flex items-center px-2 py-0.5 rounded-full bg-blue-100 text-blue-800">
+            <i class="fa-solid fa-clock mr-1"></i> <%= game.schedule_display %>
+          </span>
+        <% end %>
+        <% if game.year_limit.present? %>
+          <span class="inline-flex items-center px-2 py-0.5 rounded-full bg-amber-100 text-amber-800">
+            <i class="fa-solid fa-hourglass-half mr-1"></i> <%= game.year_limit %>年制限
+          </span>
+        <% end %>
+        <% if game.victory_sc_count != 18 %>
+          <span class="inline-flex items-center px-2 py-0.5 rounded-full bg-green-100 text-green-800">
+            <i class="fa-solid fa-crown mr-1"></i> 目標SC: <%= game.victory_sc_count %>
+          </span>
+        <% end %>
+        <% if game.scoring_system != "none" %>
+          <span class="inline-flex items-center px-2 py-0.5 rounded-full bg-indigo-100 text-indigo-800">
+            <i class="fa-solid fa-chart-bar mr-1"></i> <%= game.scoring_system_name %>
+          </span>
+        <% end %>
+      </div>
+    <% end %>
+    <% if game.auto_turn? && game.next_deadline_at.present? && game.status == "in_progress" %>
+      <div class="mt-2 px-3 py-1.5 rounded-md bg-blue-50 border border-blue-200 text-sm text-blue-800 flex items-center gap-2">
+        <i class="fa-solid fa-clock"></i>
+        <span>次のターン締切: <strong><%= game.next_deadline_at.in_time_zone("Asia/Tokyo").strftime("%Y-%m-%d %H:%M") %></strong></span>
+        <span class="text-blue-600" id="deadline-countdown"></span>
+      </div>
+      <script>
+        (function() {
+          const deadline = new Date("<%= game.next_deadline_at.iso8601 %>");
+          const countdownEl = document.getElementById('deadline-countdown');
+          function updateCountdown() {
+            const now = new Date();
+            const diff = deadline - now;
+            if (diff <= 0) {
+              countdownEl.textContent = '（締切済み — まもなく処理されます）';
+              return;
+            }
+            const hours = Math.floor(diff / (1000 * 60 * 60));
+            const minutes = Math.floor((diff % (1000 * 60 * 60)) / (1000 * 60));
+            countdownEl.textContent = `（残り ${hours}時間 ${minutes}分）`;
+          }
+          if (countdownEl) {
+            updateCountdown();
+            setInterval(updateCountdown, 60000);
+          }
+        })();
+      </script>
+    <% end %>
+    
+  </div>
+  
+  <% unless local_assigns[:hide_controls] %>
+    <div class="flex space-x-3">
+      <% if current_user&.admin? || game.administrator == current_user %>
+        <%= link_to "設定", edit_game_path(game), class: "inline-flex items-center px-4 py-2 border border-gray-300 shadow-sm text-sm font-medium rounded-md text-gray-700 bg-white hover:bg-gray-50 focus:outline-none focus:ring-2 focus:ring-offset-2 focus:ring-indigo-500" %>
+        <%= button_to "削除", game, method: :delete, class: "inline-flex items-center px-4 py-2 border border-transparent text-sm font-medium rounded-md text-white bg-red-600 hover:bg-red-700 focus:outline-none focus:ring-2 focus:ring-offset-2 focus:ring-red-500", data: { turbo_confirm: "本当に削除しますか？" } %>
+      <% end %>
+    </div>
+  <% end %>
+</div>
+
+<% # ゲーム画面（games/show）と統一されたデザインでターン情報を表示 %>
+<% 
+   target_turn = defined?(display_turn) && display_turn ? display_turn : game.latest_turn
+%>
+<% if target_turn && target_turn.phase.present? %>
+  <%
+    # フェーズ名パース (例: S1901M)
+    phase = target_turn.phase
+    year = phase[1..4]
+    season_code = phase[0]
+    type_code = phase[-1]
+    
+    season = case season_code
+             when 'S' then '春'
+             when 'F' then '秋'
+             when 'W' then '冬'
+             else ''
+             end
+             
+    type = case type_code
+           when 'M' then '移動'
+           when 'R' then '撤退'
+           when 'A' then '調整'
+           else ''
+           end
+           
+    display_date = "#{year}年 #{season} (#{type})"
+  %>
+  
+  <div class="bg-white shadow overflow-hidden sm:rounded-lg border border-gray-200 mb-6">
+    <div class="px-6 py-4 border-b border-gray-200 flex justify-between items-center bg-gray-50">
+      <div>
+        <h2 class="text-2xl font-bold text-gray-900"><%= display_date %></h2>
+        <div class="mt-1 flex items-center space-x-4 text-sm text-gray-600">
+           <span>ターン: <%= target_turn.number %></span>
+           <span class="text-gray-400">|</span>
+           <span>フェーズ: <%= phase %></span>
+        </div>
+      </div>
+      
+      <div class="flex items-center space-x-4">
+        <% if defined?(current_participant) && current_participant&.power %>
+          <div class="flex items-center bg-white px-4 py-2 rounded border border-gray-300 shadow-sm">
+            <span class="mr-2 text-sm text-gray-500">あなたの担当国:</span>
+            <span class="text-lg font-bold text-indigo-700"><%= current_participant.power %></span>
+          </div>
+        <% end %>
+      </div>
+    </div>
+  </div>
+<% end %>
diff --git a/app/views/games/show.html.erb b/app/views/games/show.html.erb
index 524b0e8..3ddd5cf 100644
--- a/app/views/games/show.html.erb
+++ b/app/views/games/show.html.erb
@@ -414,6 +414,45 @@
 
     <!-- 右カラム: 情報パネル (1/3) -->
     <div class="space-y-6">
+      <!-- 掲示板リンク -->
+      <div class="bg-white shadow rounded-lg border border-gray-200 overflow-hidden">
+        <div class="p-4 flex items-center justify-between">
+          <div class="flex items-center">
+            <div class="flex-shrink-0 bg-indigo-100 rounded-md p-3">
+              <i class="fa-solid fa-comments text-indigo-600 text-xl"></i>
+            </div>
+            <div class="ml-4">
+              <h3 class="text-lg font-medium text-gray-900">外交・交渉掲示板</h3>
+              <p class="text-sm text-gray-500">
+                秘密交渉や全体アナウンスはこちら
+              </p>
+            </div>
+          </div>
+          <div>
+            <%= link_to game_boards_path(@game), class: "inline-flex items-center px-4 py-2 border border-transparent text-sm font-medium rounded-md shadow-sm text-white bg-indigo-600 hover:bg-indigo-700 focus:outline-none focus:ring-2 focus:ring-offset-2 focus:ring-indigo-500" do %>
+              掲示板へ
+              <% 
+                # 未読件数取得（参加中の全掲示板の合計）
+                current_participant = @game.participants.find_by(user: current_user)
+                if current_participant
+                  total_unread = 0
+                  current_participant.boards.each do |board|
+                    total_unread += board.unread_count_for(current_participant)
+                  end
+                  if total_unread > 0 
+              %>
+                <span class="ml-2 inline-flex items-center justify-center px-2 py-1 text-xs font-bold leading-none text-red-100 bg-red-600 rounded-full">
+                  <%= total_unread %>
+                </span>
+              <% 
+                  end
+                end
+              %>
+            <% end %>
+          </div>
+        </div>
+      </div>
+
       <!-- 国ステータス表 -->
       <div class="bg-white shadow rounded-lg border border-gray-200 overflow-hidden">
         <div class="px-4 py-3 bg-gray-50 border-b border-gray-200">
diff --git a/app/views/layouts/application.html.erb b/app/views/layouts/application.html.erb
index ee20209..cf206fd 100644
--- a/app/views/layouts/application.html.erb
+++ b/app/views/layouts/application.html.erb
@@ -8,6 +8,7 @@
     <meta name="mobile-web-app-capable" content="yes">
     <%= csrf_meta_tags %>
     <%= csp_meta_tag %>
+    <%= action_cable_meta_tag %>
 
     <%= yield :head %>
 
diff --git a/config/cable.yml b/config/cable.yml
index b9adc5a..b2b9685 100644
--- a/config/cable.yml
+++ b/config/cable.yml
@@ -3,7 +3,9 @@
 # not a terminal started via bin/rails console! Add "console" to any action or any ERB template view
 # to make the web console appear.
 development:
-  adapter: async
+  adapter: solid_cable
+  polling_interval: 0.1.seconds
+  message_retention: 1.day
 
 test:
   adapter: test
diff --git a/config/importmap.rb b/config/importmap.rb
index 909dfc5..7579217 100644
--- a/config/importmap.rb
+++ b/config/importmap.rb
@@ -5,3 +5,5 @@ pin "@hotwired/turbo-rails", to: "turbo.min.js"
 pin "@hotwired/stimulus", to: "stimulus.min.js"
 pin "@hotwired/stimulus-loading", to: "stimulus-loading.js"
 pin_all_from "app/javascript/controllers", under: "controllers"
+pin "actioncable" # @5.2.8
+pin "@rails/actioncable", to: "@rails--actioncable.js" # @8.1.200
diff --git a/config/routes.rb b/config/routes.rb
index 2819e17..2f7f8ca 100644
--- a/config/routes.rb
+++ b/config/routes.rb
@@ -21,6 +21,19 @@ Rails.application.routes.draw do
         patch :select_power
       end
     end
+
+    resources :boards, only: [ :index, :new, :create, :show ] do
+      member do
+        patch :toggle_public
+      end
+      resources :board_posts, only: [ :create ], path: "posts"
+      resources :board_memberships, only: [ :create ], path: "members" do
+        collection do
+          delete :leave
+        end
+      end
+      resources :board_proposals, only: [ :create, :update ], path: "proposals"
+    end
   end
 
   # Define your application routes per the DSL in https://guides.rubyonrails.org/routing.html
diff --git a/db/migrate/20260218084831_create_boards.rb b/db/migrate/20260218084831_create_boards.rb
new file mode 100644
index 0000000..651805a
--- /dev/null
+++ b/db/migrate/20260218084831_create_boards.rb
@@ -0,0 +1,16 @@
+class CreateBoards < ActiveRecord::Migration[8.1]
+  def change
+    create_table :boards do |t|
+      t.integer :game_id, null: false
+      t.string :board_type, null: false, default: 'negotiation'
+      t.integer :created_by_participant_id
+      t.boolean :is_public, null: false, default: false
+
+      t.timestamps
+    end
+
+    add_index :boards, :game_id
+    add_index :boards, :board_type
+    add_foreign_key :boards, :games
+  end
+end
diff --git a/db/migrate/20260218084842_create_board_memberships.rb b/db/migrate/20260218084842_create_board_memberships.rb
new file mode 100644
index 0000000..2487da0
--- /dev/null
+++ b/db/migrate/20260218084842_create_board_memberships.rb
@@ -0,0 +1,19 @@
+class CreateBoardMemberships < ActiveRecord::Migration[8.1]
+  def change
+    create_table :board_memberships do |t|
+      t.integer :board_id, null: false
+      t.integer :participant_id, null: false
+      t.datetime :joined_at, null: false
+      t.datetime :left_at
+      t.integer :last_read_post_id
+
+      t.timestamps
+    end
+
+    add_index :board_memberships, :board_id
+    add_index :board_memberships, :participant_id
+    add_index :board_memberships, [ :board_id, :participant_id ], unique: true
+    add_foreign_key :board_memberships, :boards
+    add_foreign_key :board_memberships, :participants
+  end
+end
diff --git a/db/migrate/20260218084851_create_board_posts.rb b/db/migrate/20260218084851_create_board_posts.rb
new file mode 100644
index 0000000..7e19a3c
--- /dev/null
+++ b/db/migrate/20260218084851_create_board_posts.rb
@@ -0,0 +1,17 @@
+class CreateBoardPosts < ActiveRecord::Migration[8.1]
+  def change
+    create_table :board_posts do |t|
+      t.integer :board_id, null: false
+      t.integer :participant_id, null: false
+      t.text :body, null: false
+      t.string :phase
+
+      t.timestamps
+    end
+
+    add_index :board_posts, :board_id
+    add_index :board_posts, :participant_id
+    add_foreign_key :board_posts, :boards
+    add_foreign_key :board_posts, :participants
+  end
+end
diff --git a/db/migrate/20260218084903_create_board_proposals.rb b/db/migrate/20260218084903_create_board_proposals.rb
new file mode 100644
index 0000000..4cc9232
--- /dev/null
+++ b/db/migrate/20260218084903_create_board_proposals.rb
@@ -0,0 +1,17 @@
+class CreateBoardProposals < ActiveRecord::Migration[8.1]
+  def change
+    create_table :board_proposals do |t|
+      t.integer :board_id, null: false
+      t.integer :proposer_participant_id, null: false
+      t.text :body, null: false
+      t.string :status, null: false, default: 'pending'
+
+      t.timestamps
+    end
+
+    add_index :board_proposals, :board_id
+    add_index :board_proposals, :proposer_participant_id
+    add_foreign_key :board_proposals, :boards
+    add_foreign_key :board_proposals, :participants, column: :proposer_participant_id
+  end
+end
diff --git a/db/migrate/20260218130000_create_solid_cable_messages.rb b/db/migrate/20260218130000_create_solid_cable_messages.rb
new file mode 100644
index 0000000..61e90a5
--- /dev/null
+++ b/db/migrate/20260218130000_create_solid_cable_messages.rb
@@ -0,0 +1,13 @@
+class CreateSolidCableMessages < ActiveRecord::Migration[7.1]
+  def change
+    create_table "solid_cable_messages" do |t|
+      t.binary "channel", limit: 1024, null: false
+      t.binary "payload", limit: 536870912, null: false
+      t.datetime "created_at", null: false
+      t.integer "channel_hash", limit: 8, null: false
+      t.index [ "channel" ], name: "index_solid_cable_messages_on_channel"
+      t.index [ "channel_hash" ], name: "index_solid_cable_messages_on_channel_hash"
+      t.index [ "created_at" ], name: "index_solid_cable_messages_on_created_at"
+    end
+  end
+end
diff --git a/db/migrate/20260218134459_add_phase_to_board_proposals.rb b/db/migrate/20260218134459_add_phase_to_board_proposals.rb
new file mode 100644
index 0000000..4c647ef
--- /dev/null
+++ b/db/migrate/20260218134459_add_phase_to_board_proposals.rb
@@ -0,0 +1,5 @@
+class AddPhaseToBoardProposals < ActiveRecord::Migration[8.1]
+  def change
+    add_column :board_proposals, :phase, :string
+  end
+end
diff --git a/db/schema.rb b/db/schema.rb
index 413988c..dbdc45d 100644
--- a/db/schema.rb
+++ b/db/schema.rb
@@ -10,7 +10,54 @@
 #
 # It's strongly recommended that you check this file into your version control system.
 
-ActiveRecord::Schema[8.1].define(version: 2026_02_13_122531) do
+ActiveRecord::Schema[8.1].define(version: 2026_02_18_134459) do
+  create_table "board_memberships", force: :cascade do |t|
+    t.integer "board_id", null: false
+    t.datetime "created_at", null: false
+    t.datetime "joined_at", null: false
+    t.integer "last_read_post_id"
+    t.datetime "left_at"
+    t.integer "participant_id", null: false
+    t.datetime "updated_at", null: false
+    t.index ["board_id", "participant_id"], name: "index_board_memberships_on_board_id_and_participant_id", unique: true
+    t.index ["board_id"], name: "index_board_memberships_on_board_id"
+    t.index ["participant_id"], name: "index_board_memberships_on_participant_id"
+  end
+
+  create_table "board_posts", force: :cascade do |t|
+    t.integer "board_id", null: false
+    t.text "body", null: false
+    t.datetime "created_at", null: false
+    t.integer "participant_id", null: false
+    t.string "phase"
+    t.datetime "updated_at", null: false
+    t.index ["board_id"], name: "index_board_posts_on_board_id"
+    t.index ["participant_id"], name: "index_board_posts_on_participant_id"
+  end
+
+  create_table "board_proposals", force: :cascade do |t|
+    t.integer "board_id", null: false
+    t.text "body", null: false
+    t.datetime "created_at", null: false
+    t.string "phase"
+    t.integer "proposer_participant_id", null: false
+    t.string "status", default: "pending", null: false
+    t.datetime "updated_at", null: false
+    t.index ["board_id"], name: "index_board_proposals_on_board_id"
+    t.index ["proposer_participant_id"], name: "index_board_proposals_on_proposer_participant_id"
+  end
+
+  create_table "boards", force: :cascade do |t|
+    t.string "board_type", default: "negotiation", null: false
+    t.datetime "created_at", null: false
+    t.integer "created_by_participant_id"
+    t.integer "game_id", null: false
+    t.boolean "is_public", default: false, null: false
+    t.datetime "updated_at", null: false
+    t.index ["board_type"], name: "index_boards_on_board_type"
+    t.index ["game_id"], name: "index_boards_on_game_id"
+  end
+
   create_table "games", force: :cascade do |t|
     t.string "auto_order_mode", default: "hold", null: false
     t.datetime "created_at", null: false
@@ -43,6 +90,16 @@ ActiveRecord::Schema[8.1].define(version: 2026_02_13_122531) do
     t.index ["user_id"], name: "index_participants_on_user_id"
   end
 
+  create_table "solid_cable_messages", force: :cascade do |t|
+    t.binary "channel", limit: 1024, null: false
+    t.integer "channel_hash", limit: 8, null: false
+    t.datetime "created_at", null: false
+    t.binary "payload", limit: 536870912, null: false
+    t.index ["channel"], name: "index_solid_cable_messages_on_channel"
+    t.index ["channel_hash"], name: "index_solid_cable_messages_on_channel_hash"
+    t.index ["created_at"], name: "index_solid_cable_messages_on_created_at"
+  end
+
   create_table "solid_queue_blocked_executions", force: :cascade do |t|
     t.string "concurrency_key", null: false
     t.datetime "created_at", null: false
@@ -189,6 +246,13 @@ ActiveRecord::Schema[8.1].define(version: 2026_02_13_122531) do
     t.index ["email"], name: "index_users_on_email", unique: true
   end
 
+  add_foreign_key "board_memberships", "boards"
+  add_foreign_key "board_memberships", "participants"
+  add_foreign_key "board_posts", "boards"
+  add_foreign_key "board_posts", "participants"
+  add_foreign_key "board_proposals", "boards"
+  add_foreign_key "board_proposals", "participants", column: "proposer_participant_id"
+  add_foreign_key "boards", "games"
   add_foreign_key "participants", "games"
   add_foreign_key "participants", "users"
   add_foreign_key "solid_queue_blocked_executions", "solid_queue_jobs", column: "job_id", on_delete: :cascade
diff --git a/test/controllers/boards_controller_test.rb b/test/controllers/boards_controller_test.rb
new file mode 100644
index 0000000..e069c54
--- /dev/null
+++ b/test/controllers/boards_controller_test.rb
@@ -0,0 +1,79 @@
+require "test_helper"
+
+class BoardsControllerTest < ActionDispatch::IntegrationTest
+  setup do
+    @game = games(:one)
+    # fixtureのgames(:one)はtitleだけの状態から修正されている前提だが、
+    # 念のためupdateして整合性を取る
+    @game.update!(
+      status: "in_progress",
+      participants_count: 7,
+      victory_sc_count: 18,
+      scoring_system: "none",
+      turn_schedule: "0,12"
+    )
+
+    @user = users(:austria)
+    @user_germany = users(:germany)
+
+    # 参加者作成
+    # BoardTest同様、fixtureに依存せずParticipantを作る
+    @p_austria = Participant.create!(game: @game, user: @user, power: "AUSTRIA")
+    @p_germany = Participant.create!(game: @game, user: @user_germany, power: "GERMANY")
+
+    # 共通掲示板作成
+    @game.boards.create!(board_type: "global", is_public: true)
+  end
+
+  test "should get index" do
+    login_as(@user)
+    get game_boards_url(@game)
+    assert_response :success
+    assert_select "h2", "外交・交渉掲示板"
+  end
+
+  test "should get new negotiation board" do
+    login_as(@user)
+    get new_game_board_url(@game)
+    assert_response :success
+  end
+
+  test "should create negotiation board" do
+    login_as(@user)
+    assert_difference("Board.count") do
+      post game_boards_url(@game), params: {
+        invited_participant_ids: [ @p_germany.id ]
+      }
+    end
+
+    assert_redirected_to game_board_url(@game, Board.last)
+    assert Board.last.member?(@p_austria)
+    assert Board.last.member?(@p_germany)
+  end
+
+  test "should show board" do
+    login_as(@user)
+    board = @game.boards.global.first
+    get game_board_url(@game, board)
+    assert_response :success
+  end
+
+  test "should not show board to non-member" do
+    # 第三者作成
+    user_russia = users(:russia)
+    p_russia = Participant.create!(game: @game, user: user_russia, power: "RUSSIA")
+
+    # オーストリアとドイツの掲示板
+    board = @game.boards.create!(board_type: "negotiation", created_by_participant_id: @p_austria.id)
+    board.board_memberships.create!(participant: @p_austria, joined_at: Time.current)
+    board.board_memberships.create!(participant: @p_germany, joined_at: Time.current)
+
+    # ロシアでログイン
+    login_as(user_russia)
+    get game_board_url(@game, board)
+
+    assert_redirected_to game_boards_url(@game)
+    follow_redirect!
+    assert_select "div[role='alert']", /権限がありません/
+  end
+end
diff --git a/test/fixtures/games.yml b/test/fixtures/games.yml
index 7f69ebe..7918216 100644
--- a/test/fixtures/games.yml
+++ b/test/fixtures/games.yml
@@ -1,11 +1,13 @@
 # Read about fixtures at https://api.rubyonrails.org/classes/ActiveRecord/FixtureSet.html
 
 one:
-  title: MyString
-  participants_count: 1
-  memo: MyText
+  title: GameOne
+  status: in_progress
+  turn_schedule: "0,12"
+  participants_count: 7
 
 two:
-  title: MyString
+  title: GameTwo
+  status: recruiting
+  turn_schedule: "0,12"
   participants_count: 1
-  memo: MyText
diff --git a/test/fixtures/users.yml b/test/fixtures/users.yml
index 2dc9d23..7aec0d1 100644
--- a/test/fixtures/users.yml
+++ b/test/fixtures/users.yml
@@ -9,3 +9,21 @@ two:
   email: two@example.com
   password_digest: <%= BCrypt::Password.create('password') %>
   admin: false
+
+austria:
+  username: AustriaUser
+  email: austria@example.com
+  password_digest: <%= BCrypt::Password.create('password') %>
+  admin: false
+
+germany:
+  username: GermanyUser
+  email: germany@example.com
+  password_digest: <%= BCrypt::Password.create('password') %>
+  admin: false
+
+russia:
+  username: RussiaUser
+  email: russia@example.com
+  password_digest: <%= BCrypt::Password.create('password') %>
+  admin: false
diff --git a/test/models/board_test.rb b/test/models/board_test.rb
new file mode 100644
index 0000000..a594876
--- /dev/null
+++ b/test/models/board_test.rb
@@ -0,0 +1,85 @@
+require "test_helper"
+
+class BoardTest < ActiveSupport::TestCase
+  def setup
+    @game = games(:one) # fixturesから取得
+    @austria = users(:austria)
+    @germany = users(:germany)
+    @russia = users(:russia)
+
+    # 参加者作成（fixtureに依存せず動的に作る方が安全だが簡略化）
+    @p_austria = Participant.create!(game: @game, user: @austria, power: "AUSTRIA")
+    @p_germany = Participant.create!(game: @game, user: @germany, power: "GERMANY")
+    @p_russia = Participant.create!(game: @game, user: @russia, power: "RUSSIA")
+  end
+
+  test "should create global board automatically" do
+    new_game = Game.create!(
+      title: "New Game",
+      status: "recruiting",
+      turn_schedule: "0,12",
+      participants_count: 7,
+      victory_sc_count: 18,
+      scoring_system: "none"
+    )
+    assert new_game.boards.global.exists?
+  end
+
+  test "should create negotiation board" do
+    board = @game.boards.new(board_type: "negotiation", created_by_participant_id: @p_austria.id)
+    assert board.save
+
+    # メンバー追加
+    board.board_memberships.create!(participant: @p_austria, joined_at: Time.current)
+    board.board_memberships.create!(participant: @p_germany, joined_at: Time.current)
+
+    assert board.member?(@p_austria)
+    assert board.member?(@p_germany)
+    assert_not board.member?(@p_russia)
+  end
+
+  test "should not allow duplicate member combination" do
+    # 既存のボード: Austria & Germany
+    board1 = @game.boards.create!(board_type: "negotiation", created_by_participant_id: @p_austria.id)
+    board1.board_memberships.create!(participant: @p_austria, joined_at: Time.current)
+    board1.board_memberships.create!(participant: @p_germany, joined_at: Time.current)
+
+    # 新しいボード: Austria & Germany (重複)
+    board2 = @game.boards.new(board_type: "negotiation", created_by_participant_id: @p_austria.id)
+    board2.board_memberships.build(participant: @p_austria, joined_at: Time.current)
+    board2.board_memberships.build(participant: @p_germany, joined_at: Time.current)
+
+    assert_not board2.valid?
+    assert_includes board2.errors[:base], "同じメンバー構成の掲示板がすでに存在します"
+
+    # メンバーが違えばOK: Austria & Russia
+    board3 = @game.boards.new(board_type: "negotiation", created_by_participant_id: @p_austria.id)
+    board3.board_memberships.build(participant: @p_austria, joined_at: Time.current)
+    board3.board_memberships.build(participant: @p_russia, joined_at: Time.current)
+
+    assert board3.valid?
+  end
+
+  test "unread count" do
+    board = @game.boards.create!(board_type: "negotiation", created_by_participant_id: @p_austria.id)
+    m_austria = board.board_memberships.create!(participant: @p_austria, joined_at: Time.current)
+
+    # 投稿前の未読は0
+    assert_equal 0, board.unread_count_for(@p_austria)
+
+    # 投稿作成
+    post1 = board.board_posts.create!(participant: @p_austria, body: "Hello")
+    post2 = board.board_posts.create!(participant: @p_austria, body: "World")
+
+    # Last read が nil なので全件未読扱いにはならない（ロジック上は last_read_post_id || 0 なので `id > 0` の件数になる）
+    # `id` はauto incrementで正の数なので、全件カウントされるはず
+    assert_equal 2, board.unread_count_for(@p_austria)
+
+    # 既読更新
+    m_austria.mark_read!(post1.id)
+    assert_equal 1, board.unread_count_for(@p_austria)
+
+    m_austria.mark_read!(post2.id)
+    assert_equal 0, board.unread_count_for(@p_austria)
+  end
+end
diff --git a/test/test_helper.rb b/test/test_helper.rb
index 0c22470..8a696f8 100644
--- a/test/test_helper.rb
+++ b/test/test_helper.rb
@@ -11,5 +11,8 @@ module ActiveSupport
     fixtures :all
 
     # Add more helper methods to be used by all tests here...
+    def login_as(user, password: "password")
+      post login_url, params: { email: user.email, password: password }
+    end
   end
 end
diff --git a/vendor/javascript/@rails--actioncable.js b/vendor/javascript/@rails--actioncable.js
new file mode 100644
index 0000000..093687a
--- /dev/null
+++ b/vendor/javascript/@rails--actioncable.js
@@ -0,0 +1,4 @@
+// @rails/actioncable@8.1.200 downloaded from https://ga.jspm.io/npm:@rails/actioncable@8.1.200/app/assets/javascripts/actioncable.esm.js
+
+var t={logger:typeof console!=="undefined"?console:void 0,WebSocket:typeof WebSocket!=="undefined"?WebSocket:void 0};var e={log(...e){if(this.enabled){e.push(Date.now());t.logger.log("[ActionCable]",...e)}}};const n=()=>(new Date).getTime();const i=t=>(n()-t)/1e3;class ConnectionMonitor{constructor(t){this.visibilityDidChange=this.visibilityDidChange.bind(this);this.connection=t;this.reconnectAttempts=0}start(){if(!this.isRunning()){this.startedAt=n();delete this.stoppedAt;this.startPolling();addEventListener("visibilitychange",this.visibilityDidChange);e.log(`ConnectionMonitor started. stale threshold = ${this.constructor.staleThreshold} s`)}}stop(){if(this.isRunning()){this.stoppedAt=n();this.stopPolling();removeEventListener("visibilitychange",this.visibilityDidChange);e.log("ConnectionMonitor stopped")}}isRunning(){return this.startedAt&&!this.stoppedAt}recordMessage(){this.pingedAt=n()}recordConnect(){this.reconnectAttempts=0;delete this.disconnectedAt;e.log("ConnectionMonitor recorded connect")}recordDisconnect(){this.disconnectedAt=n();e.log("ConnectionMonitor recorded disconnect")}startPolling(){this.stopPolling();this.poll()}stopPolling(){clearTimeout(this.pollTimeout)}poll(){this.pollTimeout=setTimeout((()=>{this.reconnectIfStale();this.poll()}),this.getPollInterval())}getPollInterval(){const{staleThreshold:t,reconnectionBackoffRate:e}=this.constructor;const n=Math.pow(1+e,Math.min(this.reconnectAttempts,10));const i=this.reconnectAttempts===0?1:e;const s=i*Math.random();return t*1e3*n*(1+s)}reconnectIfStale(){if(this.connectionIsStale()){e.log(`ConnectionMonitor detected stale connection. reconnectAttempts = ${this.reconnectAttempts}, time stale = ${i(this.refreshedAt)} s, stale threshold = ${this.constructor.staleThreshold} s`);this.reconnectAttempts++;if(this.disconnectedRecently())e.log(`ConnectionMonitor skipping reopening recent disconnect. time disconnected = ${i(this.disconnectedAt)} s`);else{e.log("ConnectionMonitor reopening");this.connection.reopen()}}}get refreshedAt(){return this.pingedAt?this.pingedAt:this.startedAt}connectionIsStale(){return i(this.refreshedAt)>this.constructor.staleThreshold}disconnectedRecently(){return this.disconnectedAt&&i(this.disconnectedAt)<this.constructor.staleThreshold}visibilityDidChange(){document.visibilityState==="visible"&&setTimeout((()=>{if(this.connectionIsStale()||!this.connection.isOpen()){e.log(`ConnectionMonitor reopening stale connection on visibilitychange. visibilityState = ${document.visibilityState}`);this.connection.reopen()}}),200)}}ConnectionMonitor.staleThreshold=6;ConnectionMonitor.reconnectionBackoffRate=.15;var s={message_types:{welcome:"welcome",disconnect:"disconnect",ping:"ping",confirmation:"confirm_subscription",rejection:"reject_subscription"},disconnect_reasons:{unauthorized:"unauthorized",invalid_request:"invalid_request",server_restart:"server_restart",remote:"remote"},default_mount_path:"/cable",protocols:["actioncable-v1-json","actioncable-unsupported"]};const{message_types:o,protocols:r}=s;const c=r.slice(0,r.length-1);const u=[].indexOf;class Connection{constructor(t){this.open=this.open.bind(this);this.consumer=t;this.subscriptions=this.consumer.subscriptions;this.monitor=new ConnectionMonitor(this);this.disconnected=true}send(t){if(this.isOpen()){this.webSocket.send(JSON.stringify(t));return true}return false}open(){if(this.isActive()){e.log(`Attempted to open WebSocket, but existing socket is ${this.getState()}`);return false}{const n=[...r,...this.consumer.subprotocols||[]];e.log(`Opening WebSocket, current state is ${this.getState()}, subprotocols: ${n}`);this.webSocket&&this.uninstallEventHandlers();this.webSocket=new t.WebSocket(this.consumer.url,n);this.installEventHandlers();this.monitor.start();return true}}close({allowReconnect:t}={allowReconnect:true}){t||this.monitor.stop();if(this.isOpen())return this.webSocket.close()}reopen(){e.log(`Reopening WebSocket, current state is ${this.getState()}`);if(!this.isActive())return this.open();try{return this.close()}catch(t){e.log("Failed to reopen WebSocket",t)}finally{e.log(`Reopening WebSocket in ${this.constructor.reopenDelay}ms`);setTimeout(this.open,this.constructor.reopenDelay)}}getProtocol(){if(this.webSocket)return this.webSocket.protocol}isOpen(){return this.isState("open")}isActive(){return this.isState("open","connecting")}triedToReconnect(){return this.monitor.reconnectAttempts>0}isProtocolSupported(){return u.call(c,this.getProtocol())>=0}isState(...t){return u.call(t,this.getState())>=0}getState(){if(this.webSocket)for(let e in t.WebSocket)if(t.WebSocket[e]===this.webSocket.readyState)return e.toLowerCase();return null}installEventHandlers(){for(let t in this.events){const e=this.events[t].bind(this);this.webSocket[`on${t}`]=e}}uninstallEventHandlers(){for(let t in this.events)this.webSocket[`on${t}`]=function(){}}}Connection.reopenDelay=500;Connection.prototype.events={message(t){if(!this.isProtocolSupported())return;const{identifier:n,message:i,reason:s,reconnect:r,type:c}=JSON.parse(t.data);this.monitor.recordMessage();switch(c){case o.welcome:this.triedToReconnect()&&(this.reconnectAttempted=true);this.monitor.recordConnect();return this.subscriptions.reload();case o.disconnect:e.log(`Disconnecting. Reason: ${s}`);return this.close({allowReconnect:r});case o.ping:return null;case o.confirmation:this.subscriptions.confirmSubscription(n);if(this.reconnectAttempted){this.reconnectAttempted=false;return this.subscriptions.notify(n,"connected",{reconnected:true})}return this.subscriptions.notify(n,"connected",{reconnected:false});case o.rejection:return this.subscriptions.reject(n);default:return this.subscriptions.notify(n,"received",i)}},open(){e.log(`WebSocket onopen event, using '${this.getProtocol()}' subprotocol`);this.disconnected=false;if(!this.isProtocolSupported()){e.log("Protocol is unsupported. Stopping monitor and disconnecting.");return this.close({allowReconnect:false})}},close(t){e.log("WebSocket onclose event");if(!this.disconnected){this.disconnected=true;this.monitor.recordDisconnect();return this.subscriptions.notifyAll("disconnected",{willAttemptReconnect:this.monitor.isRunning()})}},error(){e.log("WebSocket onerror event")}};const h=function(t,e){if(e!=null)for(let n in e){const i=e[n];t[n]=i}return t};class Subscription{constructor(t,e={},n){this.consumer=t;this.identifier=JSON.stringify(e);h(this,n)}perform(t,e={}){e.action=t;return this.send(e)}send(t){return this.consumer.send({command:"message",identifier:this.identifier,data:JSON.stringify(t)})}unsubscribe(){return this.consumer.subscriptions.remove(this)}}class SubscriptionGuarantor{constructor(t){this.subscriptions=t;this.pendingSubscriptions=[]}guarantee(t){if(this.pendingSubscriptions.indexOf(t)==-1){e.log(`SubscriptionGuarantor guaranteeing ${t.identifier}`);this.pendingSubscriptions.push(t)}else e.log(`SubscriptionGuarantor already guaranteeing ${t.identifier}`);this.startGuaranteeing()}forget(t){e.log(`SubscriptionGuarantor forgetting ${t.identifier}`);this.pendingSubscriptions=this.pendingSubscriptions.filter((e=>e!==t))}startGuaranteeing(){this.stopGuaranteeing();this.retrySubscribing()}stopGuaranteeing(){clearTimeout(this.retryTimeout)}retrySubscribing(){this.retryTimeout=setTimeout((()=>{this.subscriptions&&typeof this.subscriptions.subscribe==="function"&&this.pendingSubscriptions.map((t=>{e.log(`SubscriptionGuarantor resubscribing ${t.identifier}`);this.subscriptions.subscribe(t)}))}),500)}}class Subscriptions{constructor(t){this.consumer=t;this.guarantor=new SubscriptionGuarantor(this);this.subscriptions=[]}create(t,e){const n=t;const i=typeof n==="object"?n:{channel:n};const s=new Subscription(this.consumer,i,e);return this.add(s)}add(t){this.subscriptions.push(t);this.consumer.ensureActiveConnection();this.notify(t,"initialized");this.subscribe(t);return t}remove(t){this.forget(t);this.findAll(t.identifier).length||this.sendCommand(t,"unsubscribe");return t}reject(t){return this.findAll(t).map((t=>{this.forget(t);this.notify(t,"rejected");return t}))}forget(t){this.guarantor.forget(t);this.subscriptions=this.subscriptions.filter((e=>e!==t));return t}findAll(t){return this.subscriptions.filter((e=>e.identifier===t))}reload(){return this.subscriptions.map((t=>this.subscribe(t)))}notifyAll(t,...e){return this.subscriptions.map((n=>this.notify(n,t,...e)))}notify(t,e,...n){let i;i=typeof t==="string"?this.findAll(t):[t];return i.map((t=>typeof t[e]==="function"?t[e](...n):void 0))}subscribe(t){this.sendCommand(t,"subscribe")&&this.guarantor.guarantee(t)}confirmSubscription(t){e.log(`Subscription confirmed ${t}`);this.findAll(t).map((t=>this.guarantor.forget(t)))}sendCommand(t,e){const{identifier:n}=t;return this.consumer.send({command:e,identifier:n})}}class Consumer{constructor(t){this._url=t;this.subscriptions=new Subscriptions(this);this.connection=new Connection(this);this.subprotocols=[]}get url(){return l(this._url)}send(t){return this.connection.send(t)}connect(){return this.connection.open()}disconnect(){return this.connection.close({allowReconnect:false})}ensureActiveConnection(){if(!this.connection.isActive())return this.connection.open()}addSubProtocol(t){this.subprotocols=[...this.subprotocols,t]}}function l(t){typeof t==="function"&&(t=t());if(t&&!/^wss?:/i.test(t)){const e=document.createElement("a");e.href=t;e.href=e.href;e.protocol=e.protocol.replace("http","ws");return e.href}return t}function a(t=d("url")||s.default_mount_path){return new Consumer(t)}function d(t){const e=document.head.querySelector(`meta[name='action-cable-${t}']`);if(e)return e.getAttribute("content")}export{Connection,ConnectionMonitor,Consumer,s as INTERNAL,Subscription,SubscriptionGuarantor,Subscriptions,t as adapters,a as createConsumer,l as createWebSocketURL,d as getConfig,e as logger};
+
diff --git a/vendor/javascript/actioncable.js b/vendor/javascript/actioncable.js
new file mode 100644
index 0000000..36ebaf5
--- /dev/null
+++ b/vendor/javascript/actioncable.js
@@ -0,0 +1,4 @@
+// actioncable@5.2.8 downloaded from https://ga.jspm.io/npm:actioncable@5.2.8-1/lib/assets/compiled/action_cable.js
+
+var t="undefined"!==typeof globalThis?globalThis:"undefined"!==typeof self?self:global;var n={};(function(){var o=this||t;(function(){(function(){var n=[].slice;(this||t).ActionCable={INTERNAL:{message_types:{welcome:"welcome",ping:"ping",confirmation:"confirm_subscription",rejection:"reject_subscription"},default_mount_path:"/cable",protocols:["actioncable-v1-json","actioncable-unsupported"]},WebSocket:window.WebSocket,logger:window.console,createConsumer:function(n){var o;null==n&&(n=null!=(o=this.getConfig("url"))?o:(this||t).INTERNAL.default_mount_path);return new e.Consumer(this.createWebSocketURL(n))},getConfig:function(t){var n;n=document.head.querySelector("meta[name='action-cable-"+t+"']");return null!=n?n.getAttribute("content"):void 0},createWebSocketURL:function(t){var n;if(t&&!/^wss?:/i.test(t)){n=document.createElement("a");n.href=t;n.href=n.href;n.protocol=n.protocol.replace("http","ws");return n.href}return t},startDebugging:function(){return(this||t).debugging=true},stopDebugging:function(){return(this||t).debugging=null},log:function(){var o,e;o=1<=arguments.length?n.call(arguments,0):[];if((this||t).debugging){o.push(Date.now());return(e=(this||t).logger).log.apply(e,["[ActionCable]"].concat(n.call(o)))}}}}).call(this||t)}).call(o);var e=o.ActionCable;(function(){(function(){var bind=function(t,n){return function(){return t.apply(n,arguments)}};e.ConnectionMonitor=function(){var n,o,i;ConnectionMonitor.pollInterval={min:3,max:30};ConnectionMonitor.staleThreshold=6;function ConnectionMonitor(n){(this||t).connection=n;(this||t).visibilityDidChange=bind((this||t).visibilityDidChange,this||t);(this||t).reconnectAttempts=0}ConnectionMonitor.prototype.start=function(){if(!this.isRunning()){(this||t).startedAt=o();delete(this||t).stoppedAt;this.startPolling();document.addEventListener("visibilitychange",(this||t).visibilityDidChange);return e.log("ConnectionMonitor started. pollInterval = "+this.getPollInterval()+" ms")}};ConnectionMonitor.prototype.stop=function(){if(this.isRunning()){(this||t).stoppedAt=o();this.stopPolling();document.removeEventListener("visibilitychange",(this||t).visibilityDidChange);return e.log("ConnectionMonitor stopped")}};ConnectionMonitor.prototype.isRunning=function(){return null!=(this||t).startedAt&&null==(this||t).stoppedAt};ConnectionMonitor.prototype.recordPing=function(){return(this||t).pingedAt=o()};ConnectionMonitor.prototype.recordConnect=function(){(this||t).reconnectAttempts=0;this.recordPing();delete(this||t).disconnectedAt;return e.log("ConnectionMonitor recorded connect")};ConnectionMonitor.prototype.recordDisconnect=function(){(this||t).disconnectedAt=o();return e.log("ConnectionMonitor recorded disconnect")};ConnectionMonitor.prototype.startPolling=function(){this.stopPolling();return this.poll()};ConnectionMonitor.prototype.stopPolling=function(){return clearTimeout((this||t).pollTimeout)};ConnectionMonitor.prototype.poll=function(){return(this||t).pollTimeout=setTimeout(function(t){return function(){t.reconnectIfStale();return t.poll()}}(this||t),this.getPollInterval())};ConnectionMonitor.prototype.getPollInterval=function(){var o,e,i,r;r=(this||t).constructor.pollInterval,i=r.min,e=r.max;o=5*Math.log((this||t).reconnectAttempts+1);return Math.round(1e3*n(o,i,e))};ConnectionMonitor.prototype.reconnectIfStale=function(){if(this.connectionIsStale()){e.log("ConnectionMonitor detected stale connection. reconnectAttempts = "+(this||t).reconnectAttempts+", pollInterval = "+this.getPollInterval()+" ms, time disconnected = "+i((this||t).disconnectedAt)+" s, stale threshold = "+(this||t).constructor.staleThreshold+" s");(this||t).reconnectAttempts++;if(this.disconnectedRecently())return e.log("ConnectionMonitor skipping reopening recent disconnect");e.log("ConnectionMonitor reopening");return(this||t).connection.reopen()}};ConnectionMonitor.prototype.connectionIsStale=function(){var n;return i(null!=(n=(this||t).pingedAt)?n:(this||t).startedAt)>(this||t).constructor.staleThreshold};ConnectionMonitor.prototype.disconnectedRecently=function(){return(this||t).disconnectedAt&&i((this||t).disconnectedAt)<(this||t).constructor.staleThreshold};ConnectionMonitor.prototype.visibilityDidChange=function(){if("visible"===document.visibilityState)return setTimeout(function(t){return function(){if(t.connectionIsStale()||!t.connection.isOpen()){e.log("ConnectionMonitor reopening stale connection on visibilitychange. visbilityState = "+document.visibilityState);return t.connection.reopen()}}}(this||t),200)};o=function(){return(new Date).getTime()};i=function(t){return(o()-t)/1e3};n=function(t,n,o){return Math.max(n,Math.min(o,t))};return ConnectionMonitor}()}).call(this||t);(function(){var n,o,i,r,s,c=[].slice,bind=function(t,n){return function(){return t.apply(n,arguments)}},u=[].indexOf||function(n){for(var o=0,e=(this||t).length;o<e;o++)if(o in(this||t)&&(this||t)[o]===n)return o;return-1};r=e.INTERNAL,o=r.message_types,i=r.protocols;s=2<=i.length?c.call(i,0,n=i.length-1):(n=0,[]),i[n++];e.Connection=function(){Connection.reopenDelay=500;function Connection(n){(this||t).consumer=n;(this||t).open=bind((this||t).open,this||t);(this||t).subscriptions=(this||t).consumer.subscriptions;(this||t).monitor=new e.ConnectionMonitor(this||t);(this||t).disconnected=true}Connection.prototype.send=function(n){if(this.isOpen()){(this||t).webSocket.send(JSON.stringify(n));return true}return false};Connection.prototype.open=function(){if(this.isActive()){e.log("Attempted to open WebSocket, but existing socket is "+this.getState());return false}e.log("Opening WebSocket, current state is "+this.getState()+", subprotocols: "+i);null!=(this||t).webSocket&&this.uninstallEventHandlers();(this||t).webSocket=new e.WebSocket((this||t).consumer.url,i);this.installEventHandlers();(this||t).monitor.start();return true};Connection.prototype.close=function(n){var o,e;o=(null!=n?n:{allowReconnect:true}).allowReconnect;o||(this||t).monitor.stop();if(this.isActive())return null!=(e=(this||t).webSocket)?e.close():void 0};Connection.prototype.reopen=function(){var n;e.log("Reopening WebSocket, current state is "+this.getState());if(!this.isActive())return this.open();try{return this.close()}catch(t){n=t;return e.log("Failed to reopen WebSocket",n)}finally{e.log("Reopening WebSocket in "+(this||t).constructor.reopenDelay+"ms");setTimeout((this||t).open,(this||t).constructor.reopenDelay)}};Connection.prototype.getProtocol=function(){var n;return null!=(n=(this||t).webSocket)?n.protocol:void 0};Connection.prototype.isOpen=function(){return this.isState("open")};Connection.prototype.isActive=function(){return this.isState("open","connecting")};Connection.prototype.isProtocolSupported=function(){var t;return t=this.getProtocol(),u.call(s,t)>=0};Connection.prototype.isState=function(){var t,n;n=1<=arguments.length?c.call(arguments,0):[];return t=this.getState(),u.call(n,t)>=0};Connection.prototype.getState=function(){var n,o,e;for(o in WebSocket){e=WebSocket[o];if(e===(null!=(n=(this||t).webSocket)?n.readyState:void 0))return o.toLowerCase()}return null};Connection.prototype.installEventHandlers=function(){var n,o;for(n in(this||t).events){o=(this||t).events[n].bind(this||t);(this||t).webSocket["on"+n]=o}};Connection.prototype.uninstallEventHandlers=function(){var n;for(n in(this||t).events)(this||t).webSocket["on"+n]=function(){}};Connection.prototype.events={message:function(n){var e,i,r,s;if(this.isProtocolSupported()){r=JSON.parse(n.data),e=r.identifier,i=r.message,s=r.type;switch(s){case o.welcome:(this||t).monitor.recordConnect();return(this||t).subscriptions.reload();case o.ping:return(this||t).monitor.recordPing();case o.confirmation:return(this||t).subscriptions.notify(e,"connected");case o.rejection:return(this||t).subscriptions.reject(e);default:return(this||t).subscriptions.notify(e,"received",i)}}},open:function(){e.log("WebSocket onopen event, using '"+this.getProtocol()+"' subprotocol");(this||t).disconnected=false;if(!this.isProtocolSupported()){e.log("Protocol is unsupported. Stopping monitor and disconnecting.");return this.close({allowReconnect:false})}},close:function(n){e.log("WebSocket onclose event");if(!(this||t).disconnected){(this||t).disconnected=true;(this||t).monitor.recordDisconnect();return(this||t).subscriptions.notifyAll("disconnected",{willAttemptReconnect:(this||t).monitor.isRunning()})}},error:function(){return e.log("WebSocket onerror event")}};return Connection}()}).call(this||t);(function(){var n=[].slice;e.Subscriptions=function(){function Subscriptions(n){(this||t).consumer=n;(this||t).subscriptions=[]}Subscriptions.prototype.create=function(n,o){var i,r,s;i=n;r="object"===typeof i?i:{channel:i};s=new e.Subscription((this||t).consumer,r,o);return this.add(s)};Subscriptions.prototype.add=function(n){(this||t).subscriptions.push(n);(this||t).consumer.ensureActiveConnection();this.notify(n,"initialized");this.sendCommand(n,"subscribe");return n};Subscriptions.prototype.remove=function(t){this.forget(t);this.findAll(t.identifier).length||this.sendCommand(t,"unsubscribe");return t};Subscriptions.prototype.reject=function(t){var n,o,e,i,r;e=this.findAll(t);i=[];for(n=0,o=e.length;n<o;n++){r=e[n];this.forget(r);this.notify(r,"rejected");i.push(r)}return i};Subscriptions.prototype.forget=function(n){var o;(this||t).subscriptions=function(){var e,i,r,s;r=(this||t).subscriptions;s=[];for(e=0,i=r.length;e<i;e++){o=r[e];o!==n&&s.push(o)}return s}.call(this||t);return n};Subscriptions.prototype.findAll=function(n){var o,e,i,r,s;i=(this||t).subscriptions;r=[];for(o=0,e=i.length;o<e;o++){s=i[o];s.identifier===n&&r.push(s)}return r};Subscriptions.prototype.reload=function(){var n,o,e,i,r;e=(this||t).subscriptions;i=[];for(n=0,o=e.length;n<o;n++){r=e[n];i.push(this.sendCommand(r,"subscribe"))}return i};Subscriptions.prototype.notifyAll=function(){var o,e,i,r,s,c,u;e=arguments[0],o=2<=arguments.length?n.call(arguments,1):[];s=(this||t).subscriptions;c=[];for(i=0,r=s.length;i<r;i++){u=s[i];c.push((this||t).notify.apply(this||t,[u,e].concat(n.call(o))))}return c};Subscriptions.prototype.notify=function(){var t,o,e,i,r,s,c;s=arguments[0],o=arguments[1],t=3<=arguments.length?n.call(arguments,2):[];c="string"===typeof s?this.findAll(s):[s];r=[];for(e=0,i=c.length;e<i;e++){s=c[e];r.push("function"===typeof s[o]?s[o].apply(s,t):void 0)}return r};Subscriptions.prototype.sendCommand=function(n,o){var e;e=n.identifier;return(this||t).consumer.send({command:o,identifier:e})};return Subscriptions}()}).call(this||t);(function(){e.Subscription=function(){var n;function Subscription(o,e,i){(this||t).consumer=o;null==e&&(e={});(this||t).identifier=JSON.stringify(e);n(this||t,i)}Subscription.prototype.perform=function(t,n){null==n&&(n={});n.action=t;return this.send(n)};Subscription.prototype.send=function(n){return(this||t).consumer.send({command:"message",identifier:(this||t).identifier,data:JSON.stringify(n)})};Subscription.prototype.unsubscribe=function(){return(this||t).consumer.subscriptions.remove(this||t)};n=function(t,n){var o,e;if(null!=n)for(o in n){e=n[o];t[o]=e}return t};return Subscription}()}).call(this||t);(function(){e.Consumer=function(){function Consumer(n){(this||t).url=n;(this||t).subscriptions=new e.Subscriptions(this||t);(this||t).connection=new e.Connection(this||t)}Consumer.prototype.send=function(n){return(this||t).connection.send(n)};Consumer.prototype.connect=function(){return(this||t).connection.open()};Consumer.prototype.disconnect=function(){return(this||t).connection.close({allowReconnect:false})};Consumer.prototype.ensureActiveConnection=function(){if(!(this||t).connection.isActive())return(this||t).connection.open()};return Consumer}()}).call(this||t)}).call(this||t);n&&(n=e)}).call(n);var o=n;export{o as default};
+