diff --git a/.github/workflows/lint.yml b/.github/workflows/lint.yml
index 4f01d81..edf64dc 100644
--- a/.github/workflows/lint.yml
+++ b/.github/workflows/lint.yml
@@ -1,21 +1,18 @@
 name: Lint
 
-on: [pull_request]
+on:
+  pull_request:
+  push:
+    branches: [main]
 
 jobs:
   standardrb:
-    name: runner / standardrb
+    name: standardrb
     runs-on: ubuntu-latest
     steps:
-      - name: Check out code
-        uses: actions/checkout@v1
-      - name: Give permissions
-        run: |
-          sudo chown -R root:root $GITHUB_WORKSPACE
-      - name: standardrb
-        uses: SennaLabs/action-standardrb@v0.0.3
+      - uses: actions/checkout@v4
+      - uses: ruby/setup-ruby@v1
         with:
-          github_token: ${{ secrets.github_token }}
-          reporter: github-pr-review # Default is github-pr-check
-          rubocop_version: 1.1.6 # note: this actually refers to standardb version, not Rubocop
-          rubocop_flags: --format progress
+          ruby-version: "3.4"
+          bundler-cache: true
+      - run: bundle exec standardrb --format progress
diff --git a/.github/workflows/specs.yml b/.github/workflows/specs.yml
index d818479..d2db36e 100644
--- a/.github/workflows/specs.yml
+++ b/.github/workflows/specs.yml
@@ -35,11 +35,15 @@ jobs:
             rails: "8.0"
           - ruby: "3.4"
             rails: "8.0"
+          - ruby: "4.0"
+            rails: "8.0"
           # Rails 8.1
           - ruby: "3.3"
             rails: "8.1"
           - ruby: "3.4"
             rails: "8.1"
+          - ruby: "4.0"
+            rails: "8.1"
     steps:
       - uses: actions/checkout@v4
       - name: Set up Ruby ${{ matrix.ruby }}
diff --git a/.standard.yml b/.standard.yml
new file mode 100644
index 0000000..50ffdc2
--- /dev/null
+++ b/.standard.yml
@@ -0,0 +1,3 @@
+ignore:
+  - "gemfiles/vendor/**/*"
+  - "vendor/**/*"
diff --git a/Appraisals b/Appraisals
deleted file mode 100644
index 1fe4f57..0000000
--- a/Appraisals
+++ /dev/null
@@ -1,23 +0,0 @@
-appraise "rails-6.0" do
-  gem "railties", "~> 6.0"
-end
-
-appraise "rails-6.1" do
-  gem "railties", "~> 6.1"
-end
-
-appraise "rails-7.0" do
-  gem "railties", "~> 7.0"
-end
-
-appraise "rails-7.1" do
-  gem "railties", "~> 7.1"
-end
-
-appraise "rails-7.2" do
-  gem "railties", "~> 7.2"
-end
-
-appraise "rails-8.0" do
-  gem "railties", "~> 8.0"
-end
diff --git a/CHANGELOG.md b/CHANGELOG.md
index ee6dbaa..1a25010 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -2,6 +2,20 @@
 
 ## [Unreleased][main]
 
+## [0.6.0] - 2026-05-25
+- Add support for Rails 8.1
+- Add support for Devise 5
+- Allow `castle-rb` 9.x (constraint widened to `>= 7.2, < 10.0`); verified
+  against the upcoming 9.0 release — castle_devise uses only the
+  `#risk` / `#filter` / `#log` Client APIs and the `Castle::Error` /
+  `InvalidParametersError` / `InvalidRequestTokenError` classes, all of
+  which remain in 9.0.
+- Add Ruby 3.3, 3.4, and 4.0 to the CI matrix
+- Bump minimum required Ruby version to 3.2
+- Replace deprecated `ActiveSupport::Configurable` with plain Ruby attribute accessors (drops the Rails 8.2 deprecation warning)
+- Drop `appraisal` development dependency in favor of hand-maintained `gemfiles/*.gemfile`
+- Bump development Gemfile to Rails 8.1, Devise 5, sqlite3 ~> 2.1, Bundler 2.7.x
+
 ## [0.5.0] - 2025-06-17
 - Throw a warning instead of an error for the `$login.failed` event when an exception is raised
 - Security fixes and dependency updates
@@ -33,7 +47,8 @@
 
 - Initial release
 
-[main]: https://github.com/castle/castle_devise/compare/v0.5.0...HEAD
+[main]: https://github.com/castle/castle_devise/compare/v0.6.0...HEAD
+[0.6.0]: https://github.com/castle/castle_devise/compare/v0.5.0...v0.6.0
 [0.5.0]: https://github.com/castle/castle_devise/compare/v0.4.3...v0.5.0
 [0.4.3]: https://github.com/castle/castle_devise/compare/v0.4.2...v0.4.3
 [0.4.2]: https://github.com/castle/castle_devise/compare/v0.4.1...v0.4.2
diff --git a/Gemfile b/Gemfile
index 955a72e..6809524 100644
--- a/Gemfile
+++ b/Gemfile
@@ -7,15 +7,16 @@ gemspec
 
 gem "actionmailer"
 gem "activerecord"
+# Dev/test: track castle-rb upstream develop. Gemspec uses rubygems.
+gem "castle-rb", github: "castle/castle-ruby", branch: "develop"
 gem "byebug"
-gem "railties", "~> 7.2"
+gem "devise", "~> 5.0"
+gem "railties", "~> 8.1"
 gem "rake"
 gem "rspec"
 gem "rspec-rails"
 gem "simplecov"
+gem "sqlite3", "~> 2.1"
 gem "standard"
-gem "sqlite3", "~> 1.7"
 gem "vcr"
 gem "webmock"
-gem "mutex_m"
-gem "logger"
diff --git a/Gemfile.lock b/Gemfile.lock
index 97c101c..e2f4ff7 100644
--- a/Gemfile.lock
+++ b/Gemfile.lock
@@ -1,121 +1,123 @@
+GIT
+  remote: https://github.com/castle/castle-ruby.git
+  revision: 9dce01b248cc10c3e1321c417bd9b5a24aabd5bf
+  branch: develop
+  specs:
+    castle-rb (9.0.0)
+      base64 (~> 0.2)
+
 PATH
   remote: .
   specs:
-    castle_devise (0.5.0)
+    castle_devise (0.6.0)
       activesupport (>= 6.0)
-      castle-rb (>= 7.2, < 9.0)
-      devise (>= 4.3.0, < 5.0)
+      castle-rb (>= 7.2, < 10.0)
+      devise (>= 4.3.0, < 6.0)
 
 GEM
   remote: https://rubygems.org/
   specs:
-    actionmailer (7.2.3)
-      actionpack (= 7.2.3)
-      actionview (= 7.2.3)
-      activejob (= 7.2.3)
-      activesupport (= 7.2.3)
+    actionmailer (8.1.3)
+      actionpack (= 8.1.3)
+      actionview (= 8.1.3)
+      activejob (= 8.1.3)
+      activesupport (= 8.1.3)
       mail (>= 2.8.0)
       rails-dom-testing (~> 2.2)
-    actionpack (7.2.3)
-      actionview (= 7.2.3)
-      activesupport (= 7.2.3)
-      cgi
+    actionpack (8.1.3)
+      actionview (= 8.1.3)
+      activesupport (= 8.1.3)
       nokogiri (>= 1.8.5)
-      racc
-      rack (>= 2.2.4, < 3.3)
+      rack (>= 2.2.4)
       rack-session (>= 1.0.1)
       rack-test (>= 0.6.3)
       rails-dom-testing (~> 2.2)
       rails-html-sanitizer (~> 1.6)
       useragent (~> 0.16)
-    actionview (7.2.3)
-      activesupport (= 7.2.3)
+    actionview (8.1.3)
+      activesupport (= 8.1.3)
       builder (~> 3.1)
-      cgi
       erubi (~> 1.11)
       rails-dom-testing (~> 2.2)
       rails-html-sanitizer (~> 1.6)
-    activejob (7.2.3)
-      activesupport (= 7.2.3)
+    activejob (8.1.3)
+      activesupport (= 8.1.3)
       globalid (>= 0.3.6)
-    activemodel (7.2.3)
-      activesupport (= 7.2.3)
-    activerecord (7.2.3)
-      activemodel (= 7.2.3)
-      activesupport (= 7.2.3)
+    activemodel (8.1.3)
+      activesupport (= 8.1.3)
+    activerecord (8.1.3)
+      activemodel (= 8.1.3)
+      activesupport (= 8.1.3)
       timeout (>= 0.4.0)
-    activesupport (7.2.3)
+    activesupport (8.1.3)
       base64
-      benchmark (>= 0.3)
       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)
-    addressable (2.8.7)
-      public_suffix (>= 2.0.2, < 7.0)
-    appraisal (2.5.0)
-      bundler
-      rake
-      thor (>= 0.14.0)
+      uri (>= 0.13.1)
+    addressable (2.9.0)
+      public_suffix (>= 2.0.2, < 8.0)
     ast (2.4.3)
     base64 (0.3.0)
-    bcrypt (3.1.20)
-    benchmark (0.4.1)
-    bigdecimal (3.2.3)
+    bcrypt (3.1.22)
+    bigdecimal (4.1.2)
     builder (3.3.0)
-    byebug (12.0.0)
-    castle-rb (8.1.0)
-    cgi (0.5.0)
-    concurrent-ruby (1.3.5)
-    connection_pool (2.5.5)
-    crack (1.0.0)
+    byebug (13.0.0)
+      reline (>= 0.6.0)
+    concurrent-ruby (1.3.6)
+    connection_pool (3.0.2)
+    crack (1.0.1)
       bigdecimal
       rexml
     crass (1.0.6)
-    date (3.4.1)
-    devise (4.9.4)
+    date (3.5.1)
+    devise (5.0.4)
       bcrypt (~> 3.0)
       orm_adapter (~> 0.1)
-      railties (>= 4.1.0)
+      railties (>= 7.0)
       responders
       warden (~> 1.2.3)
     diff-lcs (1.6.2)
     docile (1.4.1)
     drb (2.2.3)
-    erb (5.0.1)
+    erb (6.0.4)
     erubi (1.13.1)
-    globalid (1.2.1)
+    globalid (1.3.0)
       activesupport (>= 6.1)
-    hashdiff (1.2.0)
-    i18n (1.14.7)
+    hashdiff (1.2.1)
+    i18n (1.14.8)
       concurrent-ruby (~> 1.0)
-    io-console (0.8.0)
-    irb (1.15.2)
+    io-console (0.8.2)
+    irb (1.18.0)
       pp (>= 0.6.0)
+      prism (>= 1.3.0)
       rdoc (>= 4.0.0)
       reline (>= 0.4.2)
-    json (2.12.2)
+    json (2.19.5)
     language_server-protocol (3.17.0.5)
     lint_roller (1.1.0)
     logger (1.7.0)
-    loofah (2.24.1)
+    loofah (2.25.1)
       crass (~> 1.0.2)
       nokogiri (>= 1.12.0)
-    mail (2.8.1)
+    mail (2.9.0)
+      logger
       mini_mime (>= 0.1.1)
       net-imap
       net-pop
       net-smtp
     mini_mime (1.1.5)
-    mini_portile2 (2.8.9)
-    minitest (5.25.5)
-    mutex_m (0.3.0)
-    net-imap (0.5.12)
+    minitest (6.0.6)
+      drb (~> 2.0)
+      prism (~> 1.5)
+    net-imap (0.6.4)
       date
       net-protocol
     net-pop (0.1.2)
@@ -124,45 +126,54 @@ GEM
       timeout
     net-smtp (0.5.1)
       net-protocol
-    nokogiri (1.18.10-aarch64-linux-gnu)
+    nokogiri (1.19.3-aarch64-linux-gnu)
+      racc (~> 1.4)
+    nokogiri (1.19.3-aarch64-linux-musl)
+      racc (~> 1.4)
+    nokogiri (1.19.3-arm-linux-gnu)
       racc (~> 1.4)
-    nokogiri (1.18.10-arm64-darwin)
+    nokogiri (1.19.3-arm-linux-musl)
       racc (~> 1.4)
-    nokogiri (1.18.10-x86_64-darwin)
+    nokogiri (1.19.3-arm64-darwin)
+      racc (~> 1.4)
+    nokogiri (1.19.3-x86_64-darwin)
+      racc (~> 1.4)
+    nokogiri (1.19.3-x86_64-linux-gnu)
+      racc (~> 1.4)
+    nokogiri (1.19.3-x86_64-linux-musl)
       racc (~> 1.4)
     orm_adapter (0.5.0)
-    parallel (1.27.0)
-    parser (3.3.8.0)
+    parallel (1.28.0)
+    parser (3.3.11.1)
       ast (~> 2.4.1)
       racc
-    pp (0.6.2)
+    pp (0.6.3)
       prettyprint
     prettyprint (0.2.0)
-    prism (1.4.0)
-    psych (5.2.6)
+    prism (1.9.0)
+    psych (5.3.1)
       date
       stringio
-    public_suffix (6.0.2)
+    public_suffix (7.0.5)
     racc (1.8.1)
-    rack (3.1.19)
-    rack-session (2.1.1)
+    rack (3.2.6)
+    rack-session (2.1.2)
       base64 (>= 0.1.0)
       rack (>= 3.0.0)
     rack-test (2.2.0)
       rack (>= 1.3)
-    rackup (2.2.1)
+    rackup (2.3.1)
       rack (>= 3)
     rails-dom-testing (2.3.0)
       activesupport (>= 5.0.0)
       minitest
       nokogiri (>= 1.6)
-    rails-html-sanitizer (1.6.2)
-      loofah (~> 2.21)
+    rails-html-sanitizer (1.7.0)
+      loofah (~> 2.25)
       nokogiri (>= 1.15.7, != 1.16.7, != 1.16.6, != 1.16.5, != 1.16.4, != 1.16.3, != 1.16.2, != 1.16.1, != 1.16.0.rc1, != 1.16.0)
-    railties (7.2.3)
-      actionpack (= 7.2.3)
-      activesupport (= 7.2.3)
-      cgi
+    railties (8.1.3)
+      actionpack (= 8.1.3)
+      activesupport (= 8.1.3)
       irb (~> 1.13)
       rackup (>= 1.0.0)
       rake (>= 12.2)
@@ -170,39 +181,40 @@ GEM
       tsort (>= 0.2)
       zeitwerk (~> 2.6)
     rainbow (3.1.1)
-    rake (13.3.0)
-    rdoc (6.14.0)
+    rake (13.4.2)
+    rdoc (7.2.0)
       erb
       psych (>= 4.0.0)
-    regexp_parser (2.10.0)
-    reline (0.6.1)
+      tsort
+    regexp_parser (2.12.0)
+    reline (0.6.3)
       io-console (~> 0.5)
-    responders (3.1.1)
-      actionpack (>= 5.2)
-      railties (>= 5.2)
-    rexml (3.4.1)
-    rspec (3.13.1)
+    responders (3.2.0)
+      actionpack (>= 7.0)
+      railties (>= 7.0)
+    rexml (3.4.4)
+    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-rails (8.0.0)
+    rspec-rails (8.0.4)
       actionpack (>= 7.2)
       activesupport (>= 7.2)
       railties (>= 7.2)
-      rspec-core (~> 3.13)
-      rspec-expectations (~> 3.13)
-      rspec-mocks (~> 3.13)
-      rspec-support (~> 3.13)
-    rspec-support (3.13.4)
-    rubocop (1.75.8)
+      rspec-core (>= 3.13.0, < 5.0.0)
+      rspec-expectations (>= 3.13.0, < 5.0.0)
+      rspec-mocks (>= 3.13.0, < 5.0.0)
+      rspec-support (>= 3.13.0, < 5.0.0)
+    rspec-support (3.13.7)
+    rubocop (1.84.2)
       json (~> 2.3)
       language_server-protocol (~> 3.17.0.2)
       lint_roller (~> 1.1.0)
@@ -210,87 +222,90 @@ GEM
       parser (>= 3.3.0.2)
       rainbow (>= 2.2.2, < 4.0)
       regexp_parser (>= 2.9.3, < 3.0)
-      rubocop-ast (>= 1.44.0, < 2.0)
+      rubocop-ast (>= 1.49.0, < 2.0)
       ruby-progressbar (~> 1.7)
       unicode-display_width (>= 2.4.0, < 4.0)
-    rubocop-ast (1.45.1)
+    rubocop-ast (1.49.1)
       parser (>= 3.3.7.2)
-      prism (~> 1.4)
-    rubocop-performance (1.25.0)
+      prism (~> 1.7)
+    rubocop-performance (1.26.1)
       lint_roller (~> 1.1)
       rubocop (>= 1.75.0, < 2.0)
-      rubocop-ast (>= 1.38.0, < 2.0)
+      rubocop-ast (>= 1.47.1, < 2.0)
     ruby-progressbar (1.13.0)
     securerandom (0.4.1)
     simplecov (0.22.0)
       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)
-    sqlite3 (1.7.3)
-      mini_portile2 (~> 2.8.0)
-    sqlite3 (1.7.3-aarch64-linux)
-    sqlite3 (1.7.3-arm64-darwin)
-    sqlite3 (1.7.3-x86_64-darwin)
-    standard (1.50.0)
+    sqlite3 (2.9.4-aarch64-linux-gnu)
+    sqlite3 (2.9.4-aarch64-linux-musl)
+    sqlite3 (2.9.4-arm-linux-gnu)
+    sqlite3 (2.9.4-arm-linux-musl)
+    sqlite3 (2.9.4-arm64-darwin)
+    sqlite3 (2.9.4-x86_64-darwin)
+    sqlite3 (2.9.4-x86_64-linux-gnu)
+    sqlite3 (2.9.4-x86_64-linux-musl)
+    standard (1.54.0)
       language_server-protocol (~> 3.17.0.2)
       lint_roller (~> 1.0)
-      rubocop (~> 1.75.5)
+      rubocop (~> 1.84.0)
       standard-custom (~> 1.0.0)
       standard-performance (~> 1.8)
     standard-custom (1.0.2)
       lint_roller (~> 1.0)
       rubocop (~> 1.50)
-    standard-performance (1.8.0)
+    standard-performance (1.9.0)
       lint_roller (~> 1.1)
-      rubocop-performance (~> 1.25.0)
-    stringio (3.1.7)
-    thor (1.3.2)
-    timeout (0.4.4)
+      rubocop-performance (~> 1.26.0)
+    stringio (3.2.0)
+    thor (1.5.0)
+    timeout (0.6.1)
     tsort (0.2.0)
     tzinfo (2.0.6)
       concurrent-ruby (~> 1.0)
-    unicode-display_width (3.1.4)
-      unicode-emoji (~> 4.0, >= 4.0.4)
-    unicode-emoji (4.0.4)
+    unicode-display_width (3.2.0)
+      unicode-emoji (~> 4.1)
+    unicode-emoji (4.2.0)
+    uri (1.1.1)
     useragent (0.16.11)
-    vcr (6.3.1)
-      base64
+    vcr (6.4.0)
     warden (1.2.9)
       rack (>= 2.0.9)
-    webmock (3.25.1)
+    webmock (3.26.2)
       addressable (>= 2.8.0)
       crack (>= 0.3.2)
       hashdiff (>= 0.4.0, < 2.0.0)
-    zeitwerk (2.7.3)
+    zeitwerk (2.8.2)
 
 PLATFORMS
-  aarch64-linux
-  arm64-darwin-21
-  arm64-darwin-24
-  x86_64-darwin-18
-  x86_64-darwin-19
-  x86_64-darwin-20
-  x86_64-darwin-22
+  aarch64-linux-gnu
+  aarch64-linux-musl
+  arm-linux-gnu
+  arm-linux-musl
+  arm64-darwin
+  x86_64-darwin
+  x86_64-linux-gnu
+  x86_64-linux-musl
 
 DEPENDENCIES
   actionmailer
   activerecord
-  appraisal (~> 2.5.0)
   byebug
+  castle-rb!
   castle_devise!
-  logger
-  mutex_m
-  railties (~> 7.2)
+  devise (~> 5.0)
+  railties (~> 8.1)
   rake
   rspec
   rspec-rails
   simplecov
-  sqlite3 (~> 1.7)
+  sqlite3 (~> 2.1)
   standard
   vcr
   webmock
 
 BUNDLED WITH
-   2.6.9
+   2.7.2
diff --git a/README.md b/README.md
index 6ca5c1c..361df0d 100644
--- a/README.md
+++ b/README.md
@@ -1,9 +1,5 @@
 [![Gem Version](https://badge.fury.io/rb/castle_devise.svg)](https://badge.fury.io/rb/castle_devise)
 
-**Disclaimer:** CastleDevise is currently in beta. There might be some upcoming breaking changes to the gem before we stabilize the API.
-
----
-
 # CastleDevise
 
 CastleDevise is a [Devise](https://github.com/heartcombo/devise) plugin that integrates [Castle](https://castle.io).
diff --git a/bin/console b/bin/console
index d778b90..7d2320f 100755
--- a/bin/console
+++ b/bin/console
@@ -2,7 +2,7 @@
 # frozen_string_literal: true
 
 require "bundler/setup"
-require "castle/devise"
+require "castle_devise"
 
 # You can add fixtures and/or initialization code here to make experimenting
 # with your gem easier. You can also use a different console, if you like.
diff --git a/castle_devise.gemspec b/castle_devise.gemspec
index c653007..d010c01 100644
--- a/castle_devise.gemspec
+++ b/castle_devise.gemspec
@@ -28,8 +28,6 @@ Gem::Specification.new do |spec|
   spec.require_paths = ["lib"]
 
   spec.add_dependency "activesupport", ">= 6.0"
-  spec.add_dependency "castle-rb", ">= 7.2", "< 9.0"
-  spec.add_dependency "devise", ">= 4.3.0", "< 5.0"
-
-  spec.add_development_dependency "appraisal", "~> 2.5.0"
+  spec.add_dependency "castle-rb", ">= 7.2", "< 10.0"
+  spec.add_dependency "devise", ">= 4.3.0", "< 6.0"
 end
diff --git a/gemfiles/rails_6.0.gemfile b/gemfiles/rails_6.0.gemfile
index 02475ce..fecc541 100644
--- a/gemfiles/rails_6.0.gemfile
+++ b/gemfiles/rails_6.0.gemfile
@@ -1,5 +1,3 @@
-# This file was generated by Appraisal
-
 source "https://rubygems.org"
 
 gem "actionmailer"
diff --git a/gemfiles/rails_6.1.gemfile b/gemfiles/rails_6.1.gemfile
index aa24e9a..b3c29d7 100644
--- a/gemfiles/rails_6.1.gemfile
+++ b/gemfiles/rails_6.1.gemfile
@@ -1,5 +1,3 @@
-# This file was generated by Appraisal
-
 source "https://rubygems.org"
 
 gem "actionmailer"
diff --git a/gemfiles/rails_7.0.gemfile b/gemfiles/rails_7.0.gemfile
index 5255342..8a9d966 100644
--- a/gemfiles/rails_7.0.gemfile
+++ b/gemfiles/rails_7.0.gemfile
@@ -1,5 +1,3 @@
-# This file was generated by Appraisal
-
 source "https://rubygems.org"
 
 gem "actionmailer"
diff --git a/gemfiles/rails_7.1.gemfile b/gemfiles/rails_7.1.gemfile
index 49f6e0c..a0b3173 100644
--- a/gemfiles/rails_7.1.gemfile
+++ b/gemfiles/rails_7.1.gemfile
@@ -1,5 +1,3 @@
-# This file was generated by Appraisal
-
 source "https://rubygems.org"
 
 gem "actionmailer"
diff --git a/gemfiles/rails_7.2.gemfile b/gemfiles/rails_7.2.gemfile
index 953124a..4a56e56 100644
--- a/gemfiles/rails_7.2.gemfile
+++ b/gemfiles/rails_7.2.gemfile
@@ -1,5 +1,3 @@
-# This file was generated by Appraisal
-
 source "https://rubygems.org"
 
 gem "actionmailer"
diff --git a/gemfiles/rails_8.0.gemfile b/gemfiles/rails_8.0.gemfile
index 2e6436b..6250e65 100644
--- a/gemfiles/rails_8.0.gemfile
+++ b/gemfiles/rails_8.0.gemfile
@@ -1,5 +1,3 @@
-# This file was generated by Appraisal
-
 source "https://rubygems.org"
 
 gem "actionmailer"
diff --git a/gemfiles/rails_8.1.gemfile b/gemfiles/rails_8.1.gemfile
index 49c6310..9413c8e 100644
--- a/gemfiles/rails_8.1.gemfile
+++ b/gemfiles/rails_8.1.gemfile
@@ -1,10 +1,9 @@
-# This file was generated by Appraisal
-
 source "https://rubygems.org"
 
 gem "actionmailer"
 gem "activerecord"
 gem "byebug"
+gem "devise", "~> 5.0"
 gem "railties", "~> 8.1.0"
 gem "rake"
 gem "rspec"
@@ -14,7 +13,5 @@ gem "standard"
 gem "sqlite3"
 gem "vcr"
 gem "webmock"
-gem "mutex_m"
-gem "logger"
 
 gemspec path: "../"
diff --git a/lib/castle_devise/configuration.rb b/lib/castle_devise/configuration.rb
index 98fdf25..2545b81 100644
--- a/lib/castle_devise/configuration.rb
+++ b/lib/castle_devise/configuration.rb
@@ -1,20 +1,20 @@
 # frozen_string_literal: true
 
-require "active_support/configurable"
 require "logger"
 
 module CastleDevise
-  # Configuration object using {ActiveSupport::Configurable}
+  # Plain Ruby configuration object for CastleDevise.
+  #
+  # Previously this used +ActiveSupport::Configurable+, which is deprecated
+  # and slated for removal in Rails 8.2.
   class Configuration
-    include ActiveSupport::Configurable
-
     # @!attribute api_secret
     #   @return [String] Your API secret
-    config_accessor(:api_secret)
+    attr_accessor :api_secret
 
     # @!attribute app_id
     #   @return [String] Your Castle App ID
-    config_accessor(:app_id)
+    attr_accessor :app_id
 
     # @!attribute monitoring_mode
     #   When CastleDevise is in monitoring mode, it sends requests to Castle
@@ -25,27 +25,41 @@ class Configuration
     #   from logging in/registering.
     #
     #   @return [true, false] whether to act on deny requests or not
-    config_accessor(:monitoring_mode) { false }
-
-    # @!attribute logger
-    #   @return [Logger] A Logger instance. You might want to use Rails.logger here.
-    config_accessor(:logger) { Logger.new("/dev/null") }
+    attr_accessor :monitoring_mode
 
     # @!attribute before_request_hooks
     #   @return [Array<Proc>] Array of procs that will get called before a request to the Castle API
-    config_accessor(:before_request_hooks) { [] }
+    attr_accessor :before_request_hooks
 
     # @!attribute after_request_hooks
     #   @return [Array<Proc>] Array of procs that will get called after a request to the Castle API
-    config_accessor(:after_request_hooks) { [] }
+    attr_accessor :after_request_hooks
+
+    attr_writer :logger, :castle_sdk_facade_class, :castle_client
+
+    def initialize
+      @monitoring_mode = false
+      @before_request_hooks = []
+      @after_request_hooks = []
+    end
+
+    # @!attribute logger
+    #   @return [Logger] A Logger instance. You might want to use Rails.logger here.
+    def logger
+      @logger ||= Logger.new(File::NULL)
+    end
 
     # @!attribute castle_sdk_facade_class
     #   @return [Class] Castle API implementation
-    config_accessor(:castle_sdk_facade_class) { ::CastleDevise::SdkFacade }
+    def castle_sdk_facade_class
+      @castle_sdk_facade_class ||= ::CastleDevise::SdkFacade
+    end
 
     # @!attribute castle_client
-    #   @return [Class] Castle SDK client
-    config_accessor(:castle_client) { ::Castle::Client.new }
+    #   @return [Castle::Client] Castle SDK client
+    def castle_client
+      @castle_client ||= ::Castle::Client.new
+    end
 
     # Adds a new before_request hook
     # @param blk [Proc]
diff --git a/lib/castle_devise/version.rb b/lib/castle_devise/version.rb
index adea5aa..4aaa8c5 100644
--- a/lib/castle_devise/version.rb
+++ b/lib/castle_devise/version.rb
@@ -1,5 +1,5 @@
 # frozen_string_literal: true
 
 module CastleDevise
-  VERSION = "0.5.0"
+  VERSION = "0.6.0"
 end
diff --git a/spec/castle_devise/integration/profile_update_spec.rb b/spec/castle_devise/integration/profile_update_spec.rb
index 7e930ac..6f3b9be 100644
--- a/spec/castle_devise/integration/profile_update_spec.rb
+++ b/spec/castle_devise/integration/profile_update_spec.rb
@@ -129,7 +129,7 @@
         call_risk_count = 0
         allow(facade).to receive(:risk) do
           call_risk_count += 1
-          call_risk_count >= 2 ? raise(Castle::InvalidParametersError) : login_castle_risk_response
+          (call_risk_count >= 2) ? raise(Castle::InvalidParametersError) : login_castle_risk_response
         end
 
         allow(CastleDevise.logger).to receive(:warn)
@@ -151,7 +151,7 @@
         call_risk_count = 0
         allow(facade).to receive(:risk) do
           call_risk_count += 1
-          call_risk_count >= 2 ? raise(Castle::Error) : login_castle_risk_response
+          (call_risk_count >= 2) ? raise(Castle::Error) : login_castle_risk_response
         end
 
         allow(CastleDevise.logger).to receive(:error)
diff --git a/spec/dummy_app/.ruby-version b/spec/dummy_app/.ruby-version
deleted file mode 100644
index 57cf282..0000000
--- a/spec/dummy_app/.ruby-version
+++ /dev/null
@@ -1 +0,0 @@
-2.6.5
diff --git a/spec/dummy_app/app/javascript/packs/application.js b/spec/dummy_app/app/javascript/packs/application.js
deleted file mode 100644
index 67ce467..0000000
--- a/spec/dummy_app/app/javascript/packs/application.js
+++ /dev/null
@@ -1,15 +0,0 @@
-// This is a manifest file that'll be compiled into application.js, which will include all the files
-// listed below.
-//
-// Any JavaScript/Coffee file within this directory, lib/assets/javascripts, vendor/assets/javascripts,
-// or any plugin's vendor/assets/javascripts directory can be referenced here using a relative path.
-//
-// It's not advisable to add code directly here, but if you do, it'll appear at the bottom of the
-// compiled file. JavaScript code in this file should be added after the last require_* statement.
-//
-// Read Sprockets README (https://github.com/rails/sprockets#sprockets-directives) for details
-// about supported directives.
-//
-//= require rails-ujs
-//= require activestorage
-//= require_tree .
diff --git a/spec/dummy_app/config/application.rb b/spec/dummy_app/config/application.rb
index 105dd21..0f17b32 100644
--- a/spec/dummy_app/config/application.rb
+++ b/spec/dummy_app/config/application.rb
@@ -6,8 +6,9 @@
 
 module DummyApp
   class Application < Rails::Application
-    # Initialize configuration defaults for originally generated Rails version.
-    config.load_defaults 5.2
+    # Load defaults for the Rails version we're running against. This keeps the dummy
+    # app exercising each appraisal gemfile against that Rails version's own defaults.
+    config.load_defaults Rails::VERSION::STRING.to_f
 
     # Settings in config/environments/* take precedence over those specified here.
     # Application configuration can go into files in config/initializers
diff --git a/spec/dummy_app/config/spring.rb b/spec/dummy_app/config/spring.rb
deleted file mode 100644
index db5bf13..0000000
--- a/spec/dummy_app/config/spring.rb
+++ /dev/null
@@ -1,6 +0,0 @@
-Spring.watch(
-  ".ruby-version",
-  ".rbenv-vars",
-  "tmp/restart.txt",
-  "tmp/caching-dev.txt"
-)
diff --git a/spec/dummy_app/log/development.log b/spec/dummy_app/log/development.log
deleted file mode 100644
index e69de29..0000000
diff --git a/spec/dummy_app/tmp/development_secret.txt b/spec/dummy_app/tmp/development_secret.txt
deleted file mode 100644
index 3083eb4..0000000
--- a/spec/dummy_app/tmp/development_secret.txt
+++ /dev/null
@@ -1 +0,0 @@
-42b8cc9a42dc828fc51c7b3ea484e1618ee282ddb7a52dde03b25636aa53080254fd7ad38f1eba180dc71b59471652be21d491d1c01dbc45584a512e6eba5b00
\ No newline at end of file