diff --git a/.gitlab/ci/base.yml b/.gitlab/ci/base.yml
index 79a2e6479..1339ce02b 100644
--- a/.gitlab/ci/base.yml
+++ b/.gitlab/ci/base.yml
@@ -22,6 +22,7 @@
   variables:
     REMOTE_URL: "http://selenium-firefox:4444/wd/hub"
     BROWSER: "firefox"
+    START_XVFB: "false" # not needed for headless mode
     SE_NODE_MAX_SESSIONS: "5"
     SE_NODE_OVERRIDE_MAX_SESSIONS: "true"
 
@@ -29,6 +30,7 @@
   variables:
     REMOTE_URL: "http://selenium-chrome:4444/wd/hub"
     BROWSER: chrome
+    START_XVFB: "false" # not needed for headless mode
     SE_NODE_MAX_SESSIONS: "5"
     SE_NODE_OVERRIDE_MAX_SESSIONS: "true"
 
diff --git a/spec/support/capybara/custom_extensions.rb b/spec/support/capybara/custom_extensions.rb
index 05e82855c..b8a65287a 100644
--- a/spec/support/capybara/custom_extensions.rb
+++ b/spec/support/capybara/custom_extensions.rb
@@ -152,16 +152,6 @@ module CapybaraCustomExtensions
   def page(...)
     ZammadCapybaraSessionDelegator.new(element: super, context: self)
   end
-
-  # Work around an issue with failures in Capybara if different specs of the same rspec run
-  #   use using_session with the same name, e.g. :second_browser. Solve by prepending the test name.
-  def using_session(name_or_session, &block)
-    if !(name_or_session.is_a? Capybara::Session)
-      # self.class.name refers to the RSpec test case.
-      name_or_session = (self.class.name + "::#{name_or_session}").to_sym
-    end
-    Capybara.using_session(name_or_session, &block)
-  end
 end
 
 RSpec.configure do |config|
diff --git a/spec/support/capybara/driven_by.rb b/spec/support/capybara/driven_by.rb
index c33083671..dc1cadcad 100644
--- a/spec/support/capybara/driven_by.rb
+++ b/spec/support/capybara/driven_by.rb
@@ -35,10 +35,19 @@ RSpec.configure do |config|
       browser_height = 1000
     end
 
-    # Firefox and Chrome effective screen sizes are slightly different
-    # accomodate that by reducing declared screen size on Firefox
-    browser_height -= 44 if browser_name == 'firefox'
-
     page.driver.browser.manage.window.resize_to(browser_width, browser_height)
   end
+
+  config.after(:each, type: :system) do
+    # Make sure additional sessions (from using_sessions) are always ended
+    #   after every test and not kept alive. Selenium will automatically close
+    #   idle sessions which can cause 404 errors later.
+    #   (see https://github.com/teamcapybara/capybara/issues/2237)
+    Capybara.send(:session_pool).reverse_each do |_mode, session|
+      if !session.eql?(Capybara.current_session)
+        session.quit
+      end
+    end
+  end
+
 end
diff --git a/spec/support/capybara/selenium_driver.rb b/spec/support/capybara/selenium_driver.rb
index 2f6091cf7..27f1f7010 100644
--- a/spec/support/capybara/selenium_driver.rb
+++ b/spec/support/capybara/selenium_driver.rb
@@ -8,13 +8,15 @@ Capybara.register_driver(:zammad_chrome) do |app|
 
   # Turn on browser logs
   options = Selenium::WebDriver::Chrome::Options.new(
-    logging_prefs: {
+    logging_prefs:   {
       browser: 'ALL'
     },
-    prefs:         {
+    prefs:           {
       'intl.accept_languages'                                => 'en-US',
       'profile.default_content_setting_values.notifications' => 1, # ALLOW notifications
     },
+    # Disable the "Chrome is controlled by automation software" info bar.
+    excludeSwitches: ['enable-automation'],
   )
 
   options = {
@@ -25,6 +27,7 @@ Capybara.register_driver(:zammad_chrome) do |app|
   if ENV['REMOTE_URL'].present?
     options[:browser] = :remote
     options[:url]     = ENV['REMOTE_URL']
+    options[:options].headless!
   end
 
   ENV['FAKE_SELENIUM_LOGIN_USER_ID'] = nil
@@ -51,6 +54,7 @@ Capybara.register_driver(:zammad_firefox) do |app|
   if ENV['REMOTE_URL'].present?
     options[:browser] = :remote
     options[:url]     = ENV['REMOTE_URL']
+    options[:options].headless!
   end
 
   ENV['FAKE_SELENIUM_LOGIN_USER_ID'] = nil
@@ -60,16 +64,3 @@ Capybara.register_driver(:zammad_firefox) do |app|
     driver.browser.file_detector = nil if ENV['REMOTE_URL'].present?
   end
 end
-
-class Capybara::Selenium::Driver
-  alias original_quit quit
-
-  def quit
-    original_quit
-  rescue Selenium::WebDriver::Error::ServerError
-    # Work around a possible capybara/Selenium bug. driver.quit() fails because there is already no session any more;
-    #   not sure why that happens.
-  ensure
-    @browser = nil
-  end
-end
diff --git a/spec/system/chat_spec.rb b/spec/system/chat_spec.rb
index 9660bd246..08ba371ec 100644
--- a/spec/system/chat_spec.rb
+++ b/spec/system/chat_spec.rb
@@ -37,7 +37,12 @@ RSpec.describe 'Chat Handling', type: :system do
   end
 
   def send_agent_message(message)
-    find('.active .chat-window .js-customerChatInput').send_keys(message)
+    input = find('.active .chat-window .js-customerChatInput')
+    input.send_keys(message)
+    # Work around an obsure bug of send_keys sometimes not working on Firefox headless.
+    if input.text != message
+      input.execute_script("this.textContent = '#{message}'")
+    end
     click '.active .chat-window .js-send'
   end
 
@@ -45,13 +50,13 @@ RSpec.describe 'Chat Handling', type: :system do
     it 'check that button is hidden after idle timeout', authenticated_as: :authenticate do
       click agent_chat_switch_selector
 
-      open_window_and_switch
+      using_session :customer do
+        visit chat_url
 
-      visit chat_url
-
-      expect(page).to have_css('.zammad-chat', visible: :all)
-      expect(page).to have_css('.zammad-chat-is-hidden', visible: :all)
-      expect(page).to have_no_css('.open-zammad-chat:not([style*="display: none"]', visible: :all)
+        expect(page).to have_css('.zammad-chat', visible: :all)
+        expect(page).to have_css('.zammad-chat-is-hidden', visible: :all)
+        expect(page).to have_no_css('.open-zammad-chat:not([style*="display: none"]', visible: :all)
+      end
     end
   end
 
@@ -59,13 +64,10 @@ RSpec.describe 'Chat Handling', type: :system do
     it 'messages in each direction, starting on agent side', authenticated_as: :authenticate do
       enable_agent_chat
 
-      open_window_and_switch
-
-      visit chat_url
-
-      open_chat_dialog
-
-      switch_to_window_index(1)
+      using_session :customer do
+        visit chat_url
+        open_chat_dialog
+      end
 
       click '.active .js-acceptChat'
 
@@ -74,14 +76,11 @@ RSpec.describe 'Chat Handling', type: :system do
 
       send_agent_message('my name is me')
 
-      switch_to_window_index(2)
-
-      check_content('.zammad-chat .zammad-chat-agent-status', 'Online')
-      check_content('.zammad-chat', 'my name is me')
-
-      send_customer_message('my name is customer')
-
-      switch_to_window_index(1)
+      using_session :customer do
+        check_content('.zammad-chat .zammad-chat-agent-status', 'Online')
+        check_content('.zammad-chat', 'my name is me')
+        send_customer_message('my name is customer')
+      end
 
       check_content('.active .chat-window', 'my name is customer')
       expect(page).to have_css('.active .chat-window .chat-status.is-modified')
@@ -90,11 +89,9 @@ RSpec.describe 'Chat Handling', type: :system do
 
       expect(page).to have_no_css('.active .chat-window .chat-status.is-modified')
 
-      switch_to_window_index(2)
-
-      click '.js-chat-toggle .zammad-chat-header-icon'
-
-      switch_to_window_index(1)
+      using_session :customer do
+        click '.js-chat-toggle .zammad-chat-header-icon'
+      end
 
       check_content('.active .chat-window', 'closed the conversation')
     end
@@ -102,13 +99,12 @@ RSpec.describe 'Chat Handling', type: :system do
     it 'messages in each direction, starting on customer side', authenticated_as: :authenticate do
       enable_agent_chat
 
-      open_window_and_switch
+      using_session :customer do
 
-      visit chat_url
+        visit chat_url
 
-      open_chat_dialog
-
-      switch_to_window_index(1)
+        open_chat_dialog
+      end
 
       click '.active .js-acceptChat'
 
@@ -117,13 +113,10 @@ RSpec.describe 'Chat Handling', type: :system do
       # Keep focus outside of chat window to check .chat-status.is-modified later.
       click '#global-search'
 
-      switch_to_window_index(2)
-
-      check_content('.zammad-chat .zammad-chat-agent-status', 'Online')
-
-      send_customer_message('my name is customer')
-
-      switch_to_window_index(1)
+      using_session :customer do
+        check_content('.zammad-chat .zammad-chat-agent-status', 'Online')
+        send_customer_message('my name is customer')
+      end
 
       expect(page).to have_css('.active .chat-window .chat-status.is-modified')
       check_content('.active .chat-window', 'my name is customer')
@@ -131,27 +124,24 @@ RSpec.describe 'Chat Handling', type: :system do
       send_agent_message('my name is me')
       expect(page).to have_no_css('.active .chat-window .chat-status.is-modified')
 
-      switch_to_window_index(2)
-
-      check_content('.zammad-chat', 'my name is me')
-
-      switch_to_window_index(1)
+      using_session :customer do
+        check_content('.zammad-chat', 'my name is me')
+      end
 
       click '.active .chat-window .js-disconnect:not(.is-hidden)'
       click '.active .chat-window .js-close'
 
-      switch_to_window_index(2)
+      using_session :customer do
 
-      check_content('.zammad-chat .zammad-chat-agent-status', 'Offline')
-      check_content('.zammad-chat', %r{(Chat closed by|Chat beendet von)})
+        check_content('.zammad-chat .zammad-chat-agent-status', 'Offline')
+        check_content('.zammad-chat', %r{(Chat closed by|Chat beendet von)})
 
-      click '.zammad-chat .js-chat-toggle .zammad-chat-header-icon'
+        click '.zammad-chat .js-chat-toggle .zammad-chat-header-icon'
 
-      expect(page).to have_no_css('.zammad-chat-is-open')
+        expect(page).to have_no_css('.zammad-chat-is-open')
 
-      open_chat_dialog
-
-      switch_to_window_index(1)
+        open_chat_dialog
+      end
 
       click '.active .js-acceptChat'
 
@@ -163,25 +153,25 @@ RSpec.describe 'Chat Handling', type: :system do
     it 'open the chat', authenticated_as: :authenticate do
       enable_agent_chat
 
-      open_window_and_switch
+      using_session :customer do
+        visit chat_url
 
-      visit chat_url
+        expect(page).to have_css('.zammad-chat', visible: :all)
+        expect(page).to have_css('.zammad-chat-is-hidden', visible: :all)
+        expect(page).to have_no_css('.zammad-chat-is-shown', visible: :all)
+        expect(page).to have_no_css('.zammad-chat-is-open', visible: :all)
 
-      expect(page).to have_css('.zammad-chat', visible: :all)
-      expect(page).to have_css('.zammad-chat-is-hidden', visible: :all)
-      expect(page).to have_no_css('.zammad-chat-is-shown', visible: :all)
-      expect(page).to have_no_css('.zammad-chat-is-open', visible: :all)
+        click '.open-zammad-chat'
 
-      click '.open-zammad-chat'
+        expect(page).to have_css('.zammad-chat-is-shown', visible: :all)
+        expect(page).to have_css('.zammad-chat-is-open', visible: :all)
+        check_content('.zammad-chat-modal-text', %r{(waiting|Warte)})
 
-      expect(page).to have_css('.zammad-chat-is-shown', visible: :all)
-      expect(page).to have_css('.zammad-chat-is-open', visible: :all)
-      check_content('.zammad-chat-modal-text', %r{(waiting|Warte)})
+        click '.zammad-chat-header-icon-close'
 
-      click '.zammad-chat-header-icon-close'
-
-      expect(page).to have_no_css('.zammad-chat-is-shown', visible: :all)
-      expect(page).to have_no_css('.zammad-chat-is-open', visible: :all)
+        expect(page).to have_no_css('.zammad-chat-is-shown', visible: :all)
+        expect(page).to have_no_css('.zammad-chat-is-open', visible: :all)
+      end
     end
   end
 
@@ -189,60 +179,56 @@ RSpec.describe 'Chat Handling', type: :system do
     it 'check different timeouts', authenticated_as: :authenticate do
       enable_agent_chat
 
-      open_window_and_switch
+      using_session :customer do
 
-      visit chat_url
+        visit chat_url
 
-      # No customer action, hide the widget.
-      expect(page).to have_css('.zammad-chat')
+        # No customer action, hide the widget.
+        expect(page).to have_css('.zammad-chat')
 
-      expect(page).to have_no_css('.zammad-chat')
+        expect(page).to have_no_css('.zammad-chat')
 
-      refresh
+        refresh
 
-      # No agent action, show sorry screen.
-      open_chat_dialog
+        # No agent action, show sorry screen.
+        open_chat_dialog
 
-      check_content('.zammad-chat-modal-text', %r{(waiting|Warte)})
-      check_content('.zammad-chat-modal-text', %r{(takes longer|dauert länger)})
+        check_content('.zammad-chat-modal-text', %r{(waiting|Warte)})
+        check_content('.zammad-chat-modal-text', %r{(takes longer|dauert länger)})
 
-      refresh
+        refresh
 
-      # No customer action, show sorry screen.
-      open_chat_dialog
-
-      switch_to_window_index(1)
+        # No customer action, show sorry screen.
+        open_chat_dialog
+      end
 
       click '.active .js-acceptChat'
 
       send_agent_message('agent is asking')
 
-      switch_to_window_index(2)
+      using_session :customer do
 
-      check_content('.zammad-chat', 'agent is asking')
+        check_content('.zammad-chat', 'agent is asking')
 
-      check_content('.zammad-chat-modal-text', %r{(Since you didn't respond|Da Sie in den letzten)}, wait: 30)
+        check_content('.zammad-chat-modal-text', %r{(Since you didn't respond|Da Sie in den letzten)}, wait: 30)
+      end
 
       # Test the restart of inactive chat.
-      switch_to_window_index(1)
-
       click '.active .chat-window .js-close'
 
-      switch_to_window_index(2)
+      using_session :customer do
 
-      click '.js-restart'
-
-      open_chat_dialog
-
-      switch_to_window_index(1)
+        click '.js-restart'
+        open_chat_dialog
+      end
 
       click '.active .js-acceptChat'
 
       send_agent_message('my name is me')
 
-      switch_to_window_index(2)
-
-      check_content('.zammad-chat', 'my name is me')
+      using_session :customer do
+        check_content('.zammad-chat', 'my name is me')
+      end
     end
   end
 
@@ -254,55 +240,51 @@ RSpec.describe 'Chat Handling', type: :system do
 
       expect(page).to have_no_css(agent_chat_switch_selector)
 
-      open_window_and_switch
+      using_session :customer do
 
-      visit chat_url
+        visit chat_url
 
-      check_content('.settings', '{"state":"chat_disabled"}')
-
-      switch_to_window_index(1)
+        check_content('.settings', '{"state":"chat_disabled"}')
+      end
 
       click '.content.active .js-chatSetting'
 
       expect(page).to have_css(agent_chat_switch_selector)
 
-      switch_to_window_index(2)
+      using_session :customer do
 
-      refresh
+        refresh
 
-      expect(page).to have_no_css('.zammad-chat')
-      check_content('.settings', '{"state":"chat_disabled"}', should_match: false)
-      check_content('.settings', '{"event":"chat_status_customer","data":{"state":"offline"}}')
-
-      switch_to_window_index(1)
+        expect(page).to have_no_css('.zammad-chat')
+        check_content('.settings', '{"state":"chat_disabled"}', should_match: false)
+        check_content('.settings', '{"event":"chat_status_customer","data":{"state":"offline"}}')
+      end
 
       click agent_chat_switch_selector
       click 'a[href="#customer_chat"]'
 
-      switch_to_window_index(2)
+      using_session :customer do
 
-      refresh
+        refresh
 
-      expect(page).to have_css('.zammad-chat')
-      check_content('.settings', '{"event":"chat_status_customer","data":{"state":"offline"}}', should_match: false)
-      check_content('.settings', '{"state":"online"}')
+        expect(page).to have_css('.zammad-chat')
+        check_content('.settings', '{"event":"chat_status_customer","data":{"state":"offline"}}', should_match: false)
+        check_content('.settings', '{"state":"online"}')
 
-      click '.zammad-chat .js-chat-open'
+        click '.zammad-chat .js-chat-open'
 
-      expect(page).to have_css('.zammad-chat-is-shown')
-      check_content('.zammad-chat-modal-text', %r{(waiting|Warte)})
-
-      switch_to_window_index(1)
+        expect(page).to have_css('.zammad-chat-is-shown')
+        check_content('.zammad-chat-modal-text', %r{(waiting|Warte)})
+      end
 
       check_content('.js-chatMenuItem .counter', '1')
 
-      switch_to_window_index(2)
+      using_session :customer do
 
-      click '.zammad-chat .js-chat-toggle .zammad-chat-header-icon'
+        click '.zammad-chat .js-chat-toggle .zammad-chat-header-icon'
 
-      check_content('.zammad-chat-modal-text', %r{(waiting|Warte)}, should_match: false)
-
-      switch_to_window_index(1)
+        check_content('.zammad-chat-modal-text', %r{(waiting|Warte)}, should_match: false)
+      end
 
       expect(page).to have_no_css('.js-chatMenuItem .counter')
     end
@@ -321,39 +303,35 @@ RSpec.describe 'Chat Handling', type: :system do
 
       modal_disappear
 
-      open_window_and_switch
+      using_session :customer do
 
-      visit chat_url
+        visit chat_url
 
-      open_chat_dialog
-
-      switch_to_window_index(1)
+        open_chat_dialog
+      end
 
       click '.active .js-acceptChat'
 
       expect(page).to have_css('.active .chat-window .chat-status')
 
-      switch_to_window_index(2)
-
-      check_content('.zammad-chat', %r{(Hi Stranger|My Greeting)})
-
-      switch_to_window_index(1)
+      using_session :customer do
+        check_content('.zammad-chat', %r{(Hi Stranger|My Greeting)})
+      end
 
       send_agent_message('my name is me')
 
-      switch_to_window_index(2)
+      using_session :customer do
 
-      check_content('.zammad-chat', 'my name is me')
+        check_content('.zammad-chat', 'my name is me')
 
-      refresh
+        refresh
 
-      expect(page).to have_css('.zammad-chat')
-      check_content('.zammad-chat', %r{(Hi Stranger|My Greeting)})
-      check_content('.zammad-chat', 'my name is me')
+        expect(page).to have_css('.zammad-chat')
+        check_content('.zammad-chat', %r{(Hi Stranger|My Greeting)})
+        check_content('.zammad-chat', 'my name is me')
 
-      visit "#{chat_url}#new_hash"
-
-      switch_to_window_index(1)
+        visit "#{chat_url}#new_hash"
+      end
 
       check_content('.active .chat-window .js-body', "#{chat_url}#new_hash")
     end
@@ -373,7 +351,7 @@ RSpec.describe 'Chat Handling', type: :system do
     end
   end
 
-  context 'when none jquery variant is used' do
+  context 'when no-jquery variant is used' do
     let(:chat_url_type) { 'znuny-no-jquery' }
 
     context 'when normal mode is used' do
@@ -393,13 +371,14 @@ RSpec.describe 'Chat Handling', type: :system do
     shared_examples 'test issue #2471' do
       it 'is able to close to the dialog after a idleTimeout happened' do
         click agent_chat_switch_selector
-        open_window_and_switch
+        using_session :customer do
 
-        visit chat_url
-        click '.zammad-chat .js-chat-open'
-        expect(page).to have_selector('.js-restart', wait: 60)
-        click '.js-chat-toggle .zammad-chat-header-icon'
-        expect(page).to have_no_selector('zammad-chat-is-open', wait: 60)
+          visit chat_url
+          click '.zammad-chat .js-chat-open'
+          expect(page).to have_selector('.js-restart', wait: 60)
+          click '.js-chat-toggle .zammad-chat-header-icon'
+          expect(page).to have_no_selector('zammad-chat-is-open', wait: 60)
+        end
       end
     end
 
@@ -407,7 +386,7 @@ RSpec.describe 'Chat Handling', type: :system do
       include_examples 'test issue #2471'
     end
 
-    context 'wihtout jquery' do
+    context 'without jquery' do
       let(:chat_url_type) { 'znuny-no-jquery' }
 
       include_examples 'test issue #2471'
diff --git a/test/browser/agent_organization_profile_test.rb b/test/browser/agent_organization_profile_test.rb
index 66f1ae3a2..1e7ea4aa4 100644
--- a/test/browser/agent_organization_profile_test.rb
+++ b/test/browser/agent_organization_profile_test.rb
@@ -146,9 +146,7 @@ class AgentOrganizationProfileTest < TestCase
       css:     '.active .profile [data-name="note"]',
       slow:    true,
       value:   message,
-    )
-    empty_search(
-      browser: browser1,
+      blur:    true
     )
 
     # verify
diff --git a/test/browser/agent_user_profile_test.rb b/test/browser/agent_user_profile_test.rb
index 105185627..1a57df472 100644
--- a/test/browser/agent_user_profile_test.rb
+++ b/test/browser/agent_user_profile_test.rb
@@ -139,9 +139,7 @@ class AgentUserProfileTest < TestCase
       browser: browser1,
       css:     '.active [data-name="note"]',
       value:   message,
-    )
-    empty_search(
-      browser: browser1,
+      blur:    true,
     )
 
     watch_for(
diff --git a/test/browser_test_helper.rb b/test/browser_test_helper.rb
index e69e2bb27..3e14b3a66 100644
--- a/test/browser_test_helper.rb
+++ b/test/browser_test_helper.rb
@@ -91,16 +91,6 @@ class TestCase < ActiveSupport::TestCase
       params = {
         profile: profile,
       }
-      if ENV['BROWSER_HEADLESS'].present?
-        case browser
-        when 'firefox'
-          params[:options] = Selenium::WebDriver::Firefox::Options.new
-          params[:options].add_argument('-headless')
-        when 'chrome'
-          params[:options] = Selenium::WebDriver::Chrome::Options.new
-          params[:options].add_argument('-headless')
-        end
-      end
       local_browser = Selenium::WebDriver.for(browser.to_sym, params)
       @browsers[local_browser.hash] = local_browser
       browser_instance_preferences(local_browser)
@@ -135,12 +125,24 @@ class TestCase < ActiveSupport::TestCase
       open_timeout: 120,
       read_timeout: 120
     )
+    case browser
+    when 'firefox'
+      options = Selenium::WebDriver::Firefox::Options.new
+      options.headless!
+    when 'chrome'
+      options = Selenium::WebDriver::Chrome::Options.new(
+        # Disable the "Chrome is controlled by automation software" info bar.
+        excludeSwitches: ['enable-automation'],
+      )
+      options.headless!
+    end
 
     local_browser = Selenium::WebDriver.for(
       :remote,
       url:                  ENV['REMOTE_URL'],
       desired_capabilities: caps,
       http_client:          http_client,
+      options:              options,
     )
     @browsers[local_browser.hash] = local_browser
     browser_instance_preferences(local_browser)