diff --git a/Gemfile b/Gemfile
index 5c42f52..54772fa 100644
--- a/Gemfile
+++ b/Gemfile
@@ -8,7 +8,7 @@ group :development, :test do
   gem 'async-rspec', '~> 1.17', require: false
   gem 'bundler-audit', require: false
   gem 'rake', '~> 13.0'
-  gem 'rbs', '~> 3.6', require: false
+  gem 'rbs', '~> 4.0', require: false
   gem 'redcarpet', '~> 3.6', require: false
   gem 'rspec', '~> 3.13'
   gem 'rubocop', '~> 1.68', require: false
@@ -16,6 +16,6 @@ group :development, :test do
   gem 'rubocop-rake', require: false
   gem 'rubocop-rspec', require: false
   gem 'simplecov', '~> 0.22', require: false
-  gem 'steep', '~> 1.9', require: false
+  gem 'steep', '~> 2.0', require: false
   gem 'yard', '~> 0.9', require: false
 end
diff --git a/Gemfile.lock b/Gemfile.lock
index 7a6cd17..b5c4764 100644
--- a/Gemfile.lock
+++ b/Gemfile.lock
@@ -5,7 +5,8 @@ PATH
       async (~> 2.20)
       async-http (~> 0.86)
       async-websocket (~> 0.30)
-      bigdecimal (~> 3.1)
+      base64 (~> 0.3)
+      bigdecimal (>= 3.1, < 5.0)
       logger (~> 1.6)
       opentelemetry-api (~> 1.5)
       sqlite3 (~> 2.0)
@@ -13,19 +14,6 @@ PATH
 GEM
   remote: https://rubygems.org/
   specs:
-    activesupport (8.1.3)
-      base64
-      bigdecimal
-      concurrent-ruby (~> 1.0, >= 1.3.1)
-      connection_pool (>= 2.2.5)
-      drb
-      i18n (>= 1.6, < 2)
-      json
-      logger (>= 1.4.2)
-      minitest (>= 5.1)
-      securerandom (>= 0.3)
-      tzinfo (~> 2.0, >= 2.0.5)
-      uri (>= 0.13.1)
     ast (2.4.3)
     async (2.39.0)
       console (~> 1.29)
@@ -56,12 +44,11 @@ GEM
       protocol-rack (~> 0.7)
       protocol-websocket (~> 0.17)
     base64 (0.3.0)
-    bigdecimal (3.3.1)
+    bigdecimal (4.1.2)
     bundler-audit (0.9.3)
       bundler (>= 1.2.0)
       thor (~> 1.0)
     concurrent-ruby (1.3.6)
-    connection_pool (3.0.2)
     console (1.34.3)
       fiber-annotation
       fiber-local (~> 1.1)
@@ -69,7 +56,6 @@ GEM
     csv (3.3.5)
     diff-lcs (1.6.2)
     docile (1.4.1)
-    drb (2.2.3)
     ffi (1.17.4)
     ffi (1.17.4-aarch64-linux-gnu)
     ffi (1.17.4-aarch64-linux-musl)
@@ -86,8 +72,6 @@ GEM
       fiber-storage
     fiber-storage (1.0.1)
     fileutils (1.8.0)
-    i18n (1.14.8)
-      concurrent-ruby (~> 1.0)
     io-endpoint (0.17.2)
     io-event (1.16.0)
     io-stream (0.13.0)
@@ -101,10 +85,6 @@ GEM
     logger (1.7.0)
     metrics (0.15.0)
     mini_portile2 (2.8.9)
-    minitest (6.0.6)
-      drb (~> 2.0)
-      prism (~> 1.5)
-    mutex_m (0.3.0)
     opentelemetry-api (1.10.0)
       logger
     parallel (2.1.0)
@@ -133,8 +113,9 @@ GEM
     rb-fsevent (0.11.2)
     rb-inotify (0.11.1)
       ffi (~> 1.0)
-    rbs (3.10.4)
+    rbs (4.0.2)
       logger
+      prism (>= 1.6.0)
       tsort
     redcarpet (3.6.1)
     regexp_parser (2.12.0)
@@ -199,8 +180,7 @@ GEM
     sqlite3 (2.9.4-x86_64-darwin)
     sqlite3 (2.9.4-x86_64-linux-gnu)
     sqlite3 (2.9.4-x86_64-linux-musl)
-    steep (1.10.0)
-      activesupport (>= 5.1)
+    steep (2.0.0)
       concurrent-ruby (>= 1.1.10)
       csv (>= 3.0.9)
       fileutils (>= 1.1.0)
@@ -208,10 +188,10 @@ GEM
       language_server-protocol (>= 3.17.0.4, < 4.0)
       listen (~> 3.0)
       logger (>= 1.3.0)
-      mutex_m (>= 0.3.0)
-      parser (>= 3.1)
+      parser (>= 3.2)
+      prism (>= 0.25.0)
       rainbow (>= 2.2.2, < 4.0)
-      rbs (~> 3.9)
+      rbs (~> 4.0)
       securerandom (>= 0.1)
       strscan (>= 1.0.0)
       terminal-table (>= 2, < 5)
@@ -222,8 +202,6 @@ GEM
     thor (1.5.0)
     traces (0.18.2)
     tsort (0.2.0)
-    tzinfo (2.0.6)
-      concurrent-ruby (~> 1.0)
     unicode-display_width (3.2.0)
       unicode-emoji (~> 4.1)
     unicode-emoji (4.2.0)
@@ -248,7 +226,7 @@ DEPENDENCIES
   async-rspec (~> 1.17)
   bundler-audit
   rake (~> 13.0)
-  rbs (~> 3.6)
+  rbs (~> 4.0)
   redcarpet (~> 3.6)
   rspec (~> 3.13)
   rubocop (~> 1.68)
@@ -256,7 +234,7 @@ DEPENDENCIES
   rubocop-rake
   rubocop-rspec
   simplecov (~> 0.22)
-  steep (~> 1.9)
+  steep (~> 2.0)
   yard (~> 0.9)
 
 BUNDLED WITH
diff --git a/arcp.gemspec b/arcp.gemspec
index c2c210a..0c307b6 100644
--- a/arcp.gemspec
+++ b/arcp.gemspec
@@ -38,7 +38,8 @@ Gem::Specification.new do |spec|
   spec.add_dependency 'async', '~> 2.20'
   spec.add_dependency 'async-http', '~> 0.86'
   spec.add_dependency 'async-websocket', '~> 0.30'
-  spec.add_dependency 'bigdecimal', '~> 3.1'
+  spec.add_dependency 'base64', '~> 0.3'
+  spec.add_dependency 'bigdecimal', '>= 3.1', '< 5.0'
   spec.add_dependency 'logger', '~> 1.6'
   spec.add_dependency 'opentelemetry-api', '~> 1.5'
   spec.add_dependency 'sqlite3', '~> 2.0'