diff --git a/app/controllers/authorizations_controller.rb b/app/controllers/authorizations_controller.rb
index b91699b..93d14ac 100644
--- a/app/controllers/authorizations_controller.rb
+++ b/app/controllers/authorizations_controller.rb
@@ -43,7 +43,7 @@ def new
     # ログインしていなければ、または max_age を経過していたら, ログインを求め
     # る. 
     # 本来は, 実際にログインするユーザ.
-    if logged_in? && (max_age = @request_object.max_age) &&
+    if logged_in? && (max_age = @request_object.params['max_age']) &&
                      current_user.last_login_at < max_age.seconds.ago
       flash[:alert] = 'Exceeded Max Age, Login Again'
       logout() # ここでセッションがリセットされる
@@ -69,12 +69,15 @@ def new
   # POST
   # ユーザの approve/deny を受けて、RPにリダイレクトバックする.
   def create
-    req = session[params['_viewstate']][:params]
+    req = session[params['_viewstate']]['params'] # ここは key が文字列
+    session.delete(params['_viewstate'])
     @request_object = RequestObject.find_or_build_from_params req
 
     @fake_user = FakeUser.find params[:fake_user]
-    @authorized_scopes = params[:scope]  # ● 配列になるか?
-    raise "check"
+    # {"openid"=>"1", "email"=>"1", "profile"=>"1"}
+    @authorized_scopes = params[:scope].keys.map do |n|
+      Scope.find_by_name(n) || raise
+    end
     approved = params[:approve]
     
     call_authorization_endpoint(@request_object) do |req, res|
@@ -107,9 +110,10 @@ def create
   def call_authorization_endpoint(request_obj, &block)
     endpoint = Rack::OAuth2::Server::Authorize.new &block
     req = {
-      Rack::RACK_REQUEST_QUERY_HASH => request_obj,
+      Rack::RACK_REQUEST_QUERY_HASH => request_obj.params,
       Rack::RACK_REQUEST_QUERY_STRING => "X",
       Rack::QUERY_STRING => "X",
+      Rack::RACK_INPUT => "X",
     }
     # 戻り値 = [ 200, {"Content-Type" => "text/plain"}, ["Hello Rack!\n\n"] ]
     status, header, res_body = endpoint.call(req)
@@ -180,7 +184,8 @@ def request_validation req, res
   # 'code id_token',      # Hybrid Flow              認可コード + IDトークン #fragment. エラーも fragment で.
   def consent_and_redirect_back(req, res)
     response_types = Array(req.response_type)
-    redirect_uri = req.verify_redirect_uri!(@request_object.client.redirect_uris)
+    res.redirect_uri = redirect_uri =
+                req.verify_redirect_uri!(@request_object.client.redirect_uris)
 
     if response_types.include? :code
       # Authentication Response では code (と state) しか返さない.
@@ -198,8 +203,9 @@ def consent_and_redirect_back(req, res)
         end
         authorization.save!
         authorization.scopes << @authorized_scopes # ユーザ (fake_user) が認可した scope
+        
+        res.code = authorization.code
       end
-      res.code = authorization.code
     end
 
     # 事前検査済みなので、これでよい.
@@ -215,8 +221,9 @@ def consent_and_redirect_back(req, res)
         end
         access_token.save!
         access_token.scopes << @authorized_scopes
+
+        res.access_token = access_token.to_bearer_token        
       end
-      res.access_token = access_token.to_bearer_token
     end
 
     if response_types.include? :id_token
@@ -231,12 +238,12 @@ def consent_and_redirect_back(req, res)
           end
         end
         _id_token_.save!
+
+        res.id_token = _id_token_.to_jwt(
+          code: (res.respond_to?(:code) ? res.code : nil),
+          access_token: (res.respond_to?(:access_token) ? res.access_token : nil)
+        )
       end
-      
-      res.id_token = _id_token_.to_jwt(
-        code: (res.respond_to?(:code) ? res.code : nil),
-        access_token: (res.respond_to?(:access_token) ? res.access_token : nil)
-      )
     end
     
     res.approve!
diff --git a/app/controllers/discovery_controller.rb b/app/controllers/discovery_controller.rb
index 9ee4742..32b6286 100644
--- a/app/controllers/discovery_controller.rb
+++ b/app/controllers/discovery_controller.rb
@@ -57,7 +57,9 @@ def webfinger_discovery
 
 
   def openid_configuration
-    config = OpenIDConnect::Discovery::Provider::Config::Response.new(
+    # `OpenIDConnect::Discovery::Provider::Config::Response` はクライアントが
+    # 使うクラス.
+    config = {
       issuer: IdToken.config[:issuer],
       authorization_endpoint: new_authorization_url,
       token_endpoint: access_tokens_url,
@@ -81,8 +83,8 @@ def openid_configuration
       claims_supported: ['sub', 'iss',
                          'name', 'email', 'email_verified', 'address', 'profile', 'locale', 'phone_number'], 
       # PKCE
-      code_challenge_methods_supported: ['S256']  ●●これが表示されない
-    )
+      code_challenge_methods_supported: ['S256'] 
+    }
     render json: config
   end
 end
diff --git a/app/models/request_object.rb b/app/models/request_object.rb
index 1c02d75..0afbc44 100644
--- a/app/models/request_object.rb
+++ b/app/models/request_object.rb
@@ -44,33 +44,35 @@ def to_request_object
   
   
   def self.find_or_build_from_params(params, defaults = {})
-    client = Client.find_by_identifier(params[:client_id]) ||
-             raise(Rack::OAuth2::Server::Authorize::BadRequest)
+    raise TypeError if params.nil?
+    
+    client = Client.find_by_identifier(params['client_id']) ||
+             raise(Rack::OAuth2::Server::Authorize::BadRequest.new('client_id'))
     # 両方は不可
-    if !params[:request].blank? && !params[:request_uri].blank?
-      raise(Rack::OAuth2::Server::Authorize::BadRequest)
+    if !params['request'].blank? && !params['request_uri'].blank?
+      raise Rack::OAuth2::Server::Authorize::BadRequest.new("Both of `request` and `request_uri`")
     end
     
-    if !params[:request].blank?
+    if !params['request'].blank?
       # リクエストオブジェクト外のパラメータは全部無視. JAR section 6.3
       # 署名アルゴリズムは `PS256` もしくは `ES256` のどちらか FAPI 1.0 Part 2, Section 8.6
       # `OpenIDConnect::RequestObject.decode()` メソッドもよくない。alg を制限できない。
       # `params` を差し替え
-      params = JSON::JWT.decode(params[:request], client.client_public_keys,
+      params = JSON::JWT.decode(params['request'], client.client_public_keys,
                                 SIGNING_ALG_VALUES_SUPPORTED) 
       if params.client_id != client.identifier
         raise(Rack::OAuth2::Server::Authorize::BadRequest)
       end
-    elsif !params[:request_uri].blank?
+    elsif !params['request_uri'].blank?
       # ここで `OpenIDConnect::RequestObject.fetch()` を呼び出してはいけない
       # DDoS 攻撃してしまう.
       #  -> かならず PAR <https://www.rfc-editor.org/rfc/rfc9126.html> として
       #     扱わなければならない.
-      if params[:request_uri].index(REQUEST_URI_SCHEME) != 0
-        raise(Rack::OAuth2::Server::Authorize::BadRequest)
+      if params['request_uri'].index(REQUEST_URI_SCHEME) != 0
+        raise Rack::OAuth2::Server::Authorize::BadRequest.new('uri scheme')
       end
       ret = find_by_reference_value(
-                        params[:request_uri][REQUEST_URI_SCHEME.length .. -1] )
+                        params['request_uri'][REQUEST_URI_SCHEME.length .. -1] )
       if !ret || ret.client_id != client.identifier
         raise(Rack::OAuth2::Server::Authorize::BadRequest)
       end