diff --git a/config/boot.rb b/config/boot.rb
index 7479b5aff..f21c8e585 100644
--- a/config/boot.rb
+++ b/config/boot.rb
@@ -1,5 +1,15 @@
 # frozen_string_literal: true
 
+# Rack 3.1.14 or later limits query parameters to 4096 by default, which can
+# prevent saving workflows with many statuses.
+# Setting RACK_QUERY_PARSER_PARAMS_LIMIT to 65536 allows handling up to
+# approximately 100 statuses.
+#
+# See also:
+# - https://www.redmine.org/issues/42875
+# - https://github.com/rack/rack/blob/v3.1.16/README.md#configuration
+ENV['RACK_QUERY_PARSER_PARAMS_LIMIT'] ||= '65536'
+
 # Set up gems listed in the Gemfile.
 ENV['BUNDLE_GEMFILE'] ||= File.expand_path('../../Gemfile', __FILE__)
 
diff --git a/test/functional/workflows_controller_test.rb b/test/functional/workflows_controller_test.rb
index b30559d80..dcdc8d5bb 100644
--- a/test/functional/workflows_controller_test.rb
+++ b/test/functional/workflows_controller_test.rb
@@ -211,6 +211,45 @@ class WorkflowsControllerTest < Redmine::ControllerTest
     assert w.assignee
   end
 
+  def test_post_edit_with_large_number_of_statuses
+    # This test ensures that workflows with many statuses can be saved.
+    # Without setting `ENV['RACK_QUERY_PARSER_PARAMS_LIMIT']`, this raises
+    # ActionController::BadRequest exception due to exceeding the default
+    # query parameter limit of 4096.
+    WorkflowTransition.delete_all
+
+    num_statuses = 40
+    transitions_data = {}
+
+    # Allowed statuses for a new issue (status_id = 0)
+    transitions_data['0'] = {}
+    (1..num_statuses).each do |status_id|
+      transitions_data['0'][status_id.to_s] = {'always' => '1'}
+    end
+
+    # Status transitions between statuses
+    (1..num_statuses).each do |status_id_from| # rubocop:disable RuboCopStyle/CombinableLoops
+      transitions_data[status_id_from.to_s] = {}
+      (1..num_statuses).each do |status_id_to|
+        # skip self-transitions
+        next if status_id_from == status_id_to
+
+        transitions_data[status_id_from.to_s][status_id_to.to_s] = {
+          'always' => '1', 'author' => '1', 'assignee' => '1'
+        }
+      end
+    end
+
+    assert_nothing_raised do
+      patch :update, :params => {
+        :role_id => 2,
+        :tracker_id => 1,
+        :transitions => transitions_data
+      }
+    end
+    assert_response :found
+  end
+
   def test_get_permissions
     get :permissions