@@ -2,6 +2,7 @@
 
 ### 2.2.2 (Next)
 
+* Add a configurable API application and separately mountable team read/registration endpoints, preserving the default API while supporting custom routes and registration-only applications - [@dblock](https://github.com/dblock), [@Copilot](https://github.com/apps/copilot-swe-agent).
 * Your contribution here.
 
 ### 2.2.1 (2026/10/24)
 
@@ -20,6 +20,8 @@ Build a complete Slack bot service with Slack button integration, in Ruby.
   - [OAuth Version and Scopes](#oauth-version-and-scopes)
   - [Slack App](#slack-app)
   - [API](#api)
+    - [Custom Endpoints](#custom-endpoints)
+    - [Team Endpoint Visibility](#team-endpoint-visibility)
     - [App](#app)
     - [Service Manager](#service-manager)
       - [Lifecycle Callbacks](#lifecycle-callbacks)
@@ -151,6 +153,58 @@ Navigate to either [localhost:9292](http://localhost:9292) or the ngrok URL abov
 
 This library implements an app, [SlackRubyBotServer::App](lib/slack-ruby-bot-server/app.rb) and a service manager, [SlackRubyBotServer::Service](lib/slack-ruby-bot-server/service.rb). It also provides [default HTML templates and JS scripts](public) for Slack integration.
 
+#### Custom Endpoints
+
+Set `config.api` to a Rack application, typically a `Grape::API` class, to customize the API without reopening the framework's classes. The default is `nil`, which uses `SlackRubyBotServer::Api::Endpoints::RootEndpoint`, including extensions mounted there by other gems. `SlackRubyBotServer::Config.reset!` restores this default.
+
+To add an endpoint alongside the default API:
+
+```ruby
+class ExtraApi < Grape::API
+  prefix 'api'
+  format :json
+
+  get :foobar do
+    { ok: true }
+  end
+end
+
+class ApplicationApi < Grape::API
+  mount SlackRubyBotServer::Api::Endpoints::RootEndpoint
+  mount ExtraApi
+end
+
+SlackRubyBotServer.configure do |config|
+  config.api = ApplicationApi
+end
+```
+
+Configure this before starting the application. In `config.ru`, continue running `SlackRubyBotServer::Api::Middleware.instance`; both `/api/foobar` and the existing `/api` routes then share the framework's CORS, URL-rewrite, and page middleware. A separate `Rack::Cascade` stack is unnecessary.
+
+In Rails, require the file defining `ApplicationApi` from your initializer before assigning `config.api`. For reloadable classes, make the assignment inside `Rails.application.config.to_prepare` so it references the current class. Mount `SlackRubyBotServer::Api::Middleware.instance` in your routes, for example `mount SlackRubyBotServer::Api::Middleware.instance => '/'`, rather than bypassing that middleware stack.
+
+#### Team Endpoint Visibility
+
+The default API exposes `GET /api/teams` and `GET /api/teams/:id` publicly. To retain OAuth registration without those read endpoints, use the separately mountable `TeamsEndpoint::Create`. `TeamsEndpoint::Read` contains the list and detail routes; `TeamsEndpoint` continues to mount both for backward compatibility.
+
+```ruby
+class RegistrationApi < Grape::API
+  include SlackRubyBotServer::Api::Helpers::ErrorHelpers
+
+  prefix 'api'
+  format :json
+  formatter :json, Grape::Formatter::Roar
+
+  mount SlackRubyBotServer::Api::Endpoints::TeamsEndpoint::Create
+end
+
+SlackRubyBotServer.configure do |config|
+  config.api = RegistrationApi
+end
+```
+
+This replaces the default root API: it does not expose its status, root discovery, Swagger, or team-read routes. Do not also mount `RootEndpoint` or `TeamsEndpoint`, since either would restore the public team reads. If you use the Events extension or other custom endpoints, explicitly mount their routes with their required signature verification too. Add your own authentication before mounting `TeamsEndpoint::Read` if you need protected team queries. OAuth registration still requires a valid Slack authorization code; this configuration does not add a general authentication layer.
+
 #### App
 
 The app instance checks for a working database connection, ensures indexes, performs migrations, sets up bot aliases and log levels. You can introduce custom behavior into the app lifecycle by subclassing `SlackRubyBotServer::App` and creating an instance of the child class in `config.ru`.
 
@@ -2,118 +2,129 @@ module SlackRubyBotServer
   module Api
     module Endpoints
       class TeamsEndpoint < Grape::API
-        format :json
-        helpers Helpers::CursorHelpers
-        helpers Helpers::SortHelpers
-        helpers Helpers::PaginationParameters
-
-        namespace :teams do
-          desc 'Get a team.'
-          params do
-            requires :id, type: String, desc: 'Team ID.'
-          end
-          get ':id' do
-            team = Team.find(params[:id]) || error!('Not Found', 404)
-            present team, with: Presenters::TeamPresenter
-          end
+        class Read < Grape::API
+          format :json
+          helpers Helpers::CursorHelpers
+          helpers Helpers::SortHelpers
+          helpers Helpers::PaginationParameters
 
-          desc 'Get all the teams.'
-          params do
-            optional :active, type: ::Grape::API::Boolean, desc: 'Return active teams only.'
-            use :pagination
-          end
-          sort Team::SORT_ORDERS
-          get do
-            teams = Team.all
-            teams = teams.active if params[:active]
-            teams = paginate_and_sort_by_cursor(teams, default_sort_order: '-id')
-            present teams, with: Presenters::TeamsPresenter
-          end
+          namespace :teams do
+            desc 'Get a team.'
+            params do
+              requires :id, type: String, desc: 'Team ID.'
+            end
+            get ':id' do
+              team = Team.find(params[:id]) || error!('Not Found', 404)
+              present team, with: Presenters::TeamPresenter
+            end
 
-          desc 'Create a team using an OAuth token.'
-          params do
-            requires :code, type: String
-            optional :state, type: String
-          end
-          post do
-            client = Slack::Web::Client.new
-
-            raise 'Missing SLACK_CLIENT_ID or SLACK_CLIENT_SECRET.' unless ENV.key?('SLACK_CLIENT_ID') && ENV.key?('SLACK_CLIENT_SECRET')
-
-            options = {
-              client_id: ENV.fetch('SLACK_CLIENT_ID', nil),
-              client_secret: ENV.fetch('SLACK_CLIENT_SECRET', nil),
-              code: params[:code]
-            }
-
-            rc = client.send(SlackRubyBotServer.config.oauth_access_method, options)
-
-            token = nil
-            access_token = nil
-            user_id = nil
-            bot_user_id = nil
-            team_id = nil
-            team_name = nil
-            oauth_scope = nil
-            oauth_version = SlackRubyBotServer::Config.oauth_version
-
-            case oauth_version
-            when :v2
-              access_token = rc.access_token
-              token = rc.access_token
-              user_id = rc.authed_user&.id
-              bot_user_id = rc.bot_user_id
-              team_id = rc.team&.id
-              team_name = rc.team&.name
-              oauth_scope = rc.scope
-            when :v1
-              access_token = rc.access_token
-              bot = rc.bot if rc.key?(:bot)
-              token = bot ? bot.bot_access_token : access_token
-              user_id = rc.user_id
-              bot_user_id = bot ? bot.bot_user_id : nil
-              team_id = rc.team_id
-              team_name = rc.team_name
-              oauth_scope = rc.scope
+            desc 'Get all the teams.'
+            params do
+              optional :active, type: ::Grape::API::Boolean, desc: 'Return active teams only.'
+              use :pagination
+            end
+            sort Team::SORT_ORDERS
+            get do
+              teams = Team.all
+              teams = teams.active if params[:active]
+              teams = paginate_and_sort_by_cursor(teams, default_sort_order: '-id')
+              present teams, with: Presenters::TeamsPresenter
             end
+          end
+        end
+
+        class Create < Grape::API
+          format :json
 
-            team = Team.where(token: token).first
-            team ||= Team.where(team_id: team_id, oauth_version: oauth_version).first
-            team ||= Team.where(team_id: team_id).first
-
-            if team
-              team.ping_if_active!
-
-              team.update!(
-                oauth_version: oauth_version,
-                oauth_scope: oauth_scope,
-                activated_user_id: user_id,
-                activated_user_access_token: access_token,
-                bot_user_id: bot_user_id
-              )
-
-              raise "Team #{team.name} is already registered." if team.active?
-
-              team.activate!(token)
-            else
-              team = Team.create!(
-                token: token,
-                oauth_version: oauth_version,
-                oauth_scope: oauth_scope,
-                team_id: team_id,
-                name: team_name,
-                activated_user_id: user_id,
-                activated_user_access_token: access_token,
-                bot_user_id: bot_user_id
-              )
+          namespace :teams do
+            desc 'Create a team using an OAuth token.'
+            params do
+              requires :code, type: String
+              optional :state, type: String
             end
+            post do
+              client = Slack::Web::Client.new
+
+              raise 'Missing SLACK_CLIENT_ID or SLACK_CLIENT_SECRET.' unless ENV.key?('SLACK_CLIENT_ID') && ENV.key?('SLACK_CLIENT_SECRET')
 
-            options = params.slice(:state)
+              options = {
+                client_id: ENV.fetch('SLACK_CLIENT_ID', nil),
+                client_secret: ENV.fetch('SLACK_CLIENT_SECRET', nil),
+                code: params[:code]
+              }
 
-            Service.instance.create!(team, options)
-            present team, with: Presenters::TeamPresenter
+              rc = client.send(SlackRubyBotServer.config.oauth_access_method, options)
+
+              token = nil
+              access_token = nil
+              user_id = nil
+              bot_user_id = nil
+              team_id = nil
+              team_name = nil
+              oauth_scope = nil
+              oauth_version = SlackRubyBotServer::Config.oauth_version
+
+              case oauth_version
+              when :v2
+                access_token = rc.access_token
+                token = rc.access_token
+                user_id = rc.authed_user&.id
+                bot_user_id = rc.bot_user_id
+                team_id = rc.team&.id
+                team_name = rc.team&.name
+                oauth_scope = rc.scope
+              when :v1
+                access_token = rc.access_token
+                bot = rc.bot if rc.key?(:bot)
+                token = bot ? bot.bot_access_token : access_token
+                user_id = rc.user_id
+                bot_user_id = bot ? bot.bot_user_id : nil
+                team_id = rc.team_id
+                team_name = rc.team_name
+                oauth_scope = rc.scope
+              end
+
+              team = Team.where(token: token).first
+              team ||= Team.where(team_id: team_id, oauth_version: oauth_version).first
+              team ||= Team.where(team_id: team_id).first
+
+              if team
+                team.ping_if_active!
+
+                team.update!(
+                  oauth_version: oauth_version,
+                  oauth_scope: oauth_scope,
+                  activated_user_id: user_id,
+                  activated_user_access_token: access_token,
+                  bot_user_id: bot_user_id
+                )
+
+                raise "Team #{team.name} is already registered." if team.active?
+
+                team.activate!(token)
+              else
+                team = Team.create!(
+                  token: token,
+                  oauth_version: oauth_version,
+                  oauth_scope: oauth_scope,
+                  team_id: team_id,
+                  name: team_name,
+                  activated_user_id: user_id,
+                  activated_user_access_token: access_token,
+                  bot_user_id: bot_user_id
+                )
+              end
+
+              options = params.slice(:state)
+
+              Service.instance.create!(team, options)
+              present team, with: Presenters::TeamPresenter
+            end
           end
         end
+
+        mount Read
+        mount Create
       end
     end
   end
 
@@ -37,7 +37,7 @@ def self.instance
       end
 
       def call(env)
-        Endpoints::RootEndpoint.call(env)
+        (SlackRubyBotServer::Config.api || Endpoints::RootEndpoint).call(env)
       end
     end
   end
 
@@ -8,12 +8,14 @@ module Config
     attr_accessor :view_paths
     attr_accessor :oauth_scope
     attr_accessor :oauth_version
+    attr_accessor :api
 
     def reset!
       self.logger = nil
       self.service_class = SlackRubyBotServer::Service
       self.oauth_scope = nil
       self.oauth_version = :v2
+      self.api = nil
 
       self.view_paths = [
         'views',