diff --git a/.rubocop.yml b/.rubocop.yml
index 0a0acb02..1769177e 100644
--- a/.rubocop.yml
+++ b/.rubocop.yml
@@ -29,6 +29,11 @@ Layout/LineLength:
 Layout/MultilineMethodCallIndentation:
   EnforcedStyle: indented_relative_to_receiver
 
+# Hash brace spacing is handled by prettier-ruby (@prettier/plugin-ruby), which
+# breaks empty hashes onto two lines and would otherwise conflict with rubocop.
+Layout/SpaceInsideHashLiteralBraces:
+  Enabled: false
+
 Lint/AmbiguousBlockAssociation:
   AllowedMethods: [change]
 
@@ -96,6 +101,11 @@ Style/Documentation:
 Style/DoubleNegation:
   Enabled: false
 
+# prettier-ruby always expands empty methods to `def foo\nend`. Disable
+# rubocop's preference for `def foo; end` so the two stay aligned.
+Style/EmptyMethod:
+  Enabled: false
+
 Style/FormatStringToken:
   Enabled: false
 
diff --git a/.ruby-version b/.ruby-version
index 1cf82530..7bcbb380 100644
--- a/.ruby-version
+++ b/.ruby-version
@@ -1 +1 @@
-3.4.6
+3.4.9
diff --git a/.tool-versions b/.tool-versions
index cc2bdd4b..52b82276 100644
--- a/.tool-versions
+++ b/.tool-versions
@@ -1,3 +1,3 @@
-ruby 3.4.6
-nodejs 24.14.1
+ruby 3.4.9
+nodejs 24.16.0
 yarn 1.22.22
diff --git a/CHANGELOG.md b/CHANGELOG.md
index d7865e2e..fe7a9c9e 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -2,6 +2,11 @@
 
 ## master
 
+- Bump dependencies (rack 3.1.19 → 3.2.6, rake, rspec-\*, timecop, simplecov-html, diff-lcs)
+- Bump Ruby to 3.4.9 (zlib CVE-2026-27820)
+- Bump Node.js to 24.16.0 in `.tool-versions`
+- Repair `yarn format:check`: add `syntax_tree` to the dev group (required by `@prettier/plugin-ruby` 4.x), reformat 11 spec files, and disable rubocop cops that conflict with prettier-ruby (`Layout/SpaceInsideHashLiteralBraces`, `Style/EmptyMethod`)
+
 ## 9.0.0
 
 **BREAKING CHANGES:**
diff --git a/Gemfile b/Gemfile
index 9c0b5c45..3a3f17ec 100644
--- a/Gemfile
+++ b/Gemfile
@@ -12,6 +12,7 @@ group :development do
   gem 'rubocop-performance', require: false
   gem 'rubocop-rake', require: false
   gem 'rubocop-rspec', require: false
+  gem 'syntax_tree', require: false
 end
 
 group :development, :test do
diff --git a/Gemfile.lock b/Gemfile.lock
index fbf95232..41252592 100644
--- a/Gemfile.lock
+++ b/Gemfile.lock
@@ -19,7 +19,7 @@ GEM
     debug (1.11.1)
       irb (~> 1.10)
       reline (>= 0.3.8)
-    diff-lcs (1.5.1)
+    diff-lcs (1.6.2)
     docile (1.4.1)
     erb (6.0.4)
     hashdiff (1.2.1)
@@ -38,6 +38,7 @@ GEM
       racc
     pp (0.6.3)
       prettyprint
+    prettier_print (1.2.1)
     prettyprint (0.2.0)
     prism (1.9.0)
     psych (5.3.1)
@@ -45,9 +46,9 @@ GEM
       stringio
     public_suffix (7.0.5)
     racc (1.8.1)
-    rack (3.1.19)
+    rack (3.2.6)
     rainbow (3.1.1)
-    rake (13.2.1)
+    rake (13.4.2)
     rdoc (7.2.0)
       erb
       psych (>= 4.0.0)
@@ -56,19 +57,19 @@ GEM
     reline (0.6.3)
       io-console (~> 0.5)
     rexml (3.4.4)
-    rspec (3.13.0)
+    rspec (3.13.2)
       rspec-core (~> 3.13.0)
       rspec-expectations (~> 3.13.0)
       rspec-mocks (~> 3.13.0)
-    rspec-core (3.13.4)
+    rspec-core (3.13.6)
       rspec-support (~> 3.13.0)
     rspec-expectations (3.13.5)
       diff-lcs (>= 1.2.0, < 2.0)
       rspec-support (~> 3.13.0)
-    rspec-mocks (3.13.5)
+    rspec-mocks (3.13.8)
       diff-lcs (>= 1.2.0, < 2.0)
       rspec-support (~> 3.13.0)
-    rspec-support (3.13.1)
+    rspec-support (3.13.7)
     rubocop (1.86.2)
       json (~> 2.3)
       language_server-protocol (~> 3.17.0.2)
@@ -98,10 +99,12 @@ GEM
       docile (~> 1.1)
       simplecov-html (~> 0.11)
       simplecov_json_formatter (~> 0.1)
-    simplecov-html (0.13.1)
+    simplecov-html (0.13.2)
     simplecov_json_formatter (0.1.4)
     stringio (3.2.0)
-    timecop (0.9.10)
+    syntax_tree (6.3.0)
+      prettier_print (>= 1.2.0)
+    timecop (0.9.11)
     tsort (0.2.0)
     unicode-display_width (3.2.0)
       unicode-emoji (~> 4.1)
@@ -125,6 +128,7 @@ DEPENDENCIES
   rubocop-rake
   rubocop-rspec
   simplecov
+  syntax_tree
   timecop
   webmock
 
diff --git a/castle-rb.gemspec b/castle-rb.gemspec
index 77ed2767..fad325bc 100644
--- a/castle-rb.gemspec
+++ b/castle-rb.gemspec
@@ -28,7 +28,7 @@ Gem::Specification.new do |s|
     'rubygems_mfa_required' => 'true'
   }
 
-  s.files = Dir['{lib}/**/*'] + ['README.md', 'LICENSE', 'CHANGELOG.md']
+  s.files = Dir['{lib}/**/*'] + %w[README.md LICENSE CHANGELOG.md]
   s.require_paths = ['lib']
 
   s.required_ruby_version = '>= 3.2'
diff --git a/spec/integration/rails/support/home_controller.rb b/spec/integration/rails/support/home_controller.rb
index 06013a4f..a7827a75 100644
--- a/spec/integration/rails/support/home_controller.rb
+++ b/spec/integration/rails/support/home_controller.rb
@@ -4,12 +4,7 @@ class HomeController < ActionController::Base
   # prepare context and call risk via the client
   def index1
     request_context = ::Castle::Context::Prepare.call(request)
-    payload = {
-      event: '$login',
-      status: '$succeeded',
-      user: { id: '123' },
-      properties: { key: 'value' }
-    }
+    payload = { event: '$login', status: '$succeeded', user: { id: '123' }, properties: { key: 'value' } }
     client = ::Castle::Client.new(context: request_context)
     client.risk(payload)
 
@@ -18,10 +13,11 @@ def index1
 
   # prepare payload via Payload::Prepare and call risk via the client
   def index2
-    payload = ::Castle::Payload::Prepare.call(
-      { event: '$login', status: '$succeeded', user: { id: '123' }, properties: { key: 'value' } },
-      request
-    )
+    payload =
+      ::Castle::Payload::Prepare.call(
+        { event: '$login', status: '$succeeded', user: { id: '123' }, properties: { key: 'value' } },
+        request
+      )
     client = ::Castle::Client.new
     client.risk(payload)
 
@@ -30,10 +26,11 @@ def index2
 
   # prepare payload via Payload::Prepare and call Castle::API::Risk directly
   def index3
-    payload = ::Castle::Payload::Prepare.call(
-      { event: '$login', status: '$succeeded', user: { id: '123' }, properties: { key: 'value' } },
-      request
-    )
+    payload =
+      ::Castle::Payload::Prepare.call(
+        { event: '$login', status: '$succeeded', user: { id: '123' }, properties: { key: 'value' } },
+        request
+      )
 
     Castle::API::Risk.call(payload)
 
diff --git a/spec/lib/castle/api/filter_spec.rb b/spec/lib/castle/api/filter_spec.rb
index 31c2ed33..cc4acc12 100644
--- a/spec/lib/castle/api/filter_spec.rb
+++ b/spec/lib/castle/api/filter_spec.rb
@@ -2,14 +2,7 @@
 
 RSpec.describe Castle::API::Filter do
   describe '.call' do
-    let(:options) do
-      {
-        type: '$login',
-        status: '$attempted',
-        request_token: 'token',
-        params: { email: 'foo@bar.com' }
-      }
-    end
+    let(:options) { { type: '$login', status: '$attempted', request_token: 'token', params: { email: 'foo@bar.com' } } }
 
     context 'when the request fails and the failover strategy is not :throw' do
       before do
diff --git a/spec/lib/castle/api/log_spec.rb b/spec/lib/castle/api/log_spec.rb
index aabee8df..4060debb 100644
--- a/spec/lib/castle/api/log_spec.rb
+++ b/spec/lib/castle/api/log_spec.rb
@@ -3,12 +3,7 @@
 RSpec.describe Castle::API::Log do
   describe '.call' do
     let(:options) do
-      {
-        type: '$profile_update',
-        status: '$succeeded',
-        user: { id: 'u-42' },
-        context: { ip: '1.2.3.4' }
-      }
+      { type: '$profile_update', status: '$succeeded', user: { id: 'u-42' }, context: { ip: '1.2.3.4' } }
     end
 
     context 'when the request succeeds' do
@@ -16,7 +11,9 @@
         stub_request(:post, 'https://api.castle.io/v1/log').to_return(
           status: 201,
           body: '{}',
-          headers: { 'Content-Type' => 'application/json' }
+          headers: {
+            'Content-Type' => 'application/json'
+          }
         )
       end
 
diff --git a/spec/lib/castle/api/risk_spec.rb b/spec/lib/castle/api/risk_spec.rb
index 967c9810..1b008025 100644
--- a/spec/lib/castle/api/risk_spec.rb
+++ b/spec/lib/castle/api/risk_spec.rb
@@ -3,13 +3,7 @@
 RSpec.describe Castle::API::Risk do
   describe '.call' do
     let(:options) do
-      {
-        type: '$login',
-        status: '$succeeded',
-        request_token: 'token',
-        user: { id: 'u-42' },
-        context: { ip: '1.2.3.4' }
-      }
+      { type: '$login', status: '$succeeded', request_token: 'token', user: { id: 'u-42' }, context: { ip: '1.2.3.4' } }
     end
 
     context 'when the request succeeds' do
@@ -17,7 +11,9 @@
         stub_request(:post, 'https://api.castle.io/v1/risk').to_return(
           status: 201,
           body: { policy: { action: 'allow' } }.to_json,
-          headers: { 'Content-Type' => 'application/json' }
+          headers: {
+            'Content-Type' => 'application/json'
+          }
         )
       end
 
diff --git a/spec/lib/castle/client_spec.rb b/spec/lib/castle/client_spec.rb
index adc8c994..a1009811 100644
--- a/spec/lib/castle/client_spec.rb
+++ b/spec/lib/castle/client_spec.rb
@@ -44,7 +44,8 @@
     stub_request(:any, /api.castle.io/).with(basic_auth: ['', 'secret']).to_return(
       status: response_code,
       body: response_body,
-      headers: {}
+      headers: {
+      }
     )
   end
 
diff --git a/spec/lib/castle/core/process_webhook_spec.rb b/spec/lib/castle/core/process_webhook_spec.rb
index f2002fed..a5d25776 100644
--- a/spec/lib/castle/core/process_webhook_spec.rb
+++ b/spec/lib/castle/core/process_webhook_spec.rb
@@ -17,13 +17,19 @@
           device_token: 'token',
           user_id: '',
           trigger: '$login.succeeded',
-          context: {},
-          location: {},
-          user_agent: {}
+          context: {
+          },
+          location: {
+          },
+          user_agent: {
+          }
         },
-        user_traits: {},
-        properties: {},
-        policy: {}
+        user_traits: {
+        },
+        properties: {
+        },
+        policy: {
+        }
       }.to_json
     end
 
diff --git a/spec/lib/castle/core/send_request_spec.rb b/spec/lib/castle/core/send_request_spec.rb
index 1ff17b05..ed4cb084 100644
--- a/spec/lib/castle/core/send_request_spec.rb
+++ b/spec/lib/castle/core/send_request_spec.rb
@@ -57,12 +57,8 @@
 
     context 'when post' do
       let(:time) { Time.now.utc.iso8601(3) }
-      let(:command) do
-        Castle::Commands::Risk.build(event: '$login.succeeded', user: { id: '1' }, name: "\xC4")
-      end
-      let(:expected_body) do
-        { event: '$login.succeeded', user: { id: '1' }, name: '�', context: {}, sent_at: time }
-      end
+      let(:command) { Castle::Commands::Risk.build(event: '$login.succeeded', user: { id: '1' }, name: "\xC4") }
+      let(:expected_body) { { event: '$login.succeeded', user: { id: '1' }, name: '�', context: {}, sent_at: time } }
 
       before { allow(Castle::Utils::GetTimestamp).to receive(:call).and_return(time) }
 
diff --git a/spec/lib/castle/logger_spec.rb b/spec/lib/castle/logger_spec.rb
index 31ab4169..49750880 100644
--- a/spec/lib/castle/logger_spec.rb
+++ b/spec/lib/castle/logger_spec.rb
@@ -3,7 +3,8 @@
 # tmp logger for testing
 class TmpLogger
   # @param _message [String]
-  def info(_message); end
+  def info(_message)
+  end
 end
 
 RSpec.describe Castle::Logger do
diff --git a/spec/lib/castle/webhooks/verify_spec.rb b/spec/lib/castle/webhooks/verify_spec.rb
index 53abf24d..d6a93371 100644
--- a/spec/lib/castle/webhooks/verify_spec.rb
+++ b/spec/lib/castle/webhooks/verify_spec.rb
@@ -19,13 +19,19 @@
           device_token: 'token',
           user_id: user_id,
           trigger: '$login.succeeded',
-          context: {},
-          location: {},
-          user_agent: {}
+          context: {
+          },
+          location: {
+          },
+          user_agent: {
+          }
         },
-        user_traits: {},
-        properties: {},
-        policy: {}
+        user_traits: {
+        },
+        properties: {
+        },
+        policy: {
+        }
       }.to_json
     end
 
diff --git a/spec/spec_helper.rb b/spec/spec_helper.rb
index a11bea0f..21866b55 100644
--- a/spec/spec_helper.rb
+++ b/spec/spec_helper.rb
@@ -1,9 +1,7 @@
 # frozen_string_literal: true
 
 require 'simplecov'
-SimpleCov.start do
-  add_filter '/spec/'
-end
+SimpleCov.start { add_filter '/spec/' }
 
 require 'rubygems'
 require 'bundler/setup'