diff --git a/.ruby-version b/.ruby-version
index 7bcbb38..c5106e6 100644
--- a/.ruby-version
+++ b/.ruby-version
@@ -1 +1 @@
-3.4.9
+4.0.4
diff --git a/.tool-versions b/.tool-versions
index c0d6a1e..75d5860 100644
--- a/.tool-versions
+++ b/.tool-versions
@@ -1,2 +1,2 @@
-ruby 3.4.9
+ruby 4.0.4
 nodejs 24.18.0
diff --git a/Dockerfile b/Dockerfile
index 3b72ba2..a96077a 100644
--- a/Dockerfile
+++ b/Dockerfile
@@ -1,4 +1,4 @@
-FROM ruby:3.4.9
+FROM ruby:4.0.4
 
 RUN dpkg --add-architecture i386 \
   && apt-get update -qq \
diff --git a/Gemfile b/Gemfile
index 02c894e..67018eb 100644
--- a/Gemfile
+++ b/Gemfile
@@ -23,6 +23,7 @@ end
 
 gem "bundler-audit"
 gem "next_rails"
+gem "ostruct"
 gem "concurrent-ruby", "< 1.3.5"
 gem "puma", "~> 3.7"
 # minitest 6.0 dropped minitest/mock.rb into a separate minitest-mock gem;
diff --git a/Gemfile.lock b/Gemfile.lock
index 0e66e25..0339fe1 100644
--- a/Gemfile.lock
+++ b/Gemfile.lock
@@ -251,6 +251,7 @@ GEM
     nokogiri (1.19.4)
       mini_portile2 (~> 2.8.2)
       racc (~> 1.4)
+    ostruct (0.6.3)
     parallel (2.1.0)
     parser (3.3.11.1)
       ast (~> 2.4.1)
@@ -442,6 +443,7 @@ DEPENDENCIES
   minitest (< 6)
   next_rails
   nokogiri (>= 1.13.0)
+  ostruct
   pg (~> 1.1)
   puma (~> 3.7)
   rails (>= 8.1.0, < 8.2.0)
@@ -460,7 +462,7 @@ DEPENDENCIES
   wkhtmltopdf-binary (= 0.12.3.1)
 
 RUBY VERSION
-  ruby 3.4.9p82
+  ruby 4.0.4
 
 BUNDLED WITH
   4.0.15
diff --git a/Gemfile.next.lock b/Gemfile.next.lock
index 0e66e25..0339fe1 100644
--- a/Gemfile.next.lock
+++ b/Gemfile.next.lock
@@ -251,6 +251,7 @@ GEM
     nokogiri (1.19.4)
       mini_portile2 (~> 2.8.2)
       racc (~> 1.4)
+    ostruct (0.6.3)
     parallel (2.1.0)
     parser (3.3.11.1)
       ast (~> 2.4.1)
@@ -442,6 +443,7 @@ DEPENDENCIES
   minitest (< 6)
   next_rails
   nokogiri (>= 1.13.0)
+  ostruct
   pg (~> 1.1)
   puma (~> 3.7)
   rails (>= 8.1.0, < 8.2.0)
@@ -460,7 +462,7 @@ DEPENDENCIES
   wkhtmltopdf-binary (= 0.12.3.1)
 
 RUBY VERSION
-  ruby 3.4.9p82
+  ruby 4.0.4
 
 BUNDLED WITH
   4.0.15