diff --git a/.github/workflows/rubocop.yml b/.github/workflows/rubocop.yml
new file mode 100644
index 0000000..655752d
--- /dev/null
+++ b/.github/workflows/rubocop.yml
@@ -0,0 +1,21 @@
+name: RuboCop
+
+on: [push, pull_request]
+
+permissions:
+  contents: read
+
+jobs:
+  rubocop:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@3d3c42e5aac5ba805825da76410c181273ba90b1 # v7.0.1
+        with:
+          persist-credentials: false
+      - name: Set up Ruby
+        uses: ruby/setup-ruby@95ef2b042f9d7a56d8268cba8559e2842e2ad01b # v1.321.0
+        with:
+          bundler-cache: true
+          ruby-version: "3.4"
+      - name: Run RuboCop
+        run: bundle exec rubocop
diff --git a/.github/workflows/standardrb.yaml b/.github/workflows/standardrb.yaml
deleted file mode 100644
index f79fbde..0000000
--- a/.github/workflows/standardrb.yaml
+++ /dev/null
@@ -1,15 +0,0 @@
-name: StandardRB
-
-on: [push]
-
-jobs:
-  standardrb:
-    runs-on: ubuntu-latest
-    permissions:
-      checks: write
-      contents: write
-    steps:
-    - name: StandardRB Linter
-      uses: standardrb/standard-ruby-action@v1
-      env:
-        GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}
diff --git a/.rubocop.yml b/.rubocop.yml
index da64f40..92f1761 100644
--- a/.rubocop.yml
+++ b/.rubocop.yml
@@ -1,12 +1,27 @@
+inherit_mode:
+  merge:
+    - Exclude
+    - Include
+
+inherit_gem:
+  rubocop-gusto:
+    - config/default.yml
+    - config/sidekiq.yml
+
+plugins:
+  - rubocop-gusto
+  - rubocop-rspec
+  - rubocop-performance
+  - rubocop-rake
+
 AllCops:
   TargetRubyVersion: 3.3
+  Exclude:
+    - 'vendor/**/*'
 
-require:
-  - standard
-  - standard-custom
-  - standard-performance
-
-inherit_gem:
-  standard: config/base.yml
-  standard-custom: config/base.yml
-  standard-performance: config/base.yml
+# singed does not use Sorbet: there is no sorbet/ config, no sorbet runtime dependency, and no
+# typecheck step. The Sorbet cops would only add `# typed:` sigils that nothing reads, and
+# `# typed: strict` would claim a level of typing this gem does not have. rubocop-gusto's own
+# .rubocop.yml disables the department for the same reason.
+Sorbet:
+  Enabled: false
diff --git a/.standard.yml b/.standard.yml
deleted file mode 100644
index f31800f..0000000
--- a/.standard.yml
+++ /dev/null
@@ -1,2 +0,0 @@
-fix: true
-format: progress
diff --git a/Gemfile b/Gemfile
index 29ee1a5..5fc3c87 100644
--- a/Gemfile
+++ b/Gemfile
@@ -8,6 +8,6 @@ gemspec
 gem "activejob"
 gem "rake", "~> 13.4"
 gem "rspec"
+gem "rubocop-gusto", require: false
 gem "rubyzip"
 gem "sidekiq"
-gem "standard"
diff --git a/Gemfile.lock b/Gemfile.lock
index 171a96d..e755e9d 100644
--- a/Gemfile.lock
+++ b/Gemfile.lock
@@ -26,10 +26,13 @@ GEM
     ast (2.4.3)
     base64 (0.3.0)
     bigdecimal (4.1.2)
+    code_teams (1.3.1)
+      sorbet-runtime
     concurrent-ruby (1.3.8)
     connection_pool (3.0.2)
     diff-lcs (1.6.2)
     drb (2.2.3)
+    erubi (1.13.1)
     globalid (1.4.0)
       activesupport (>= 6.1)
     i18n (1.15.2)
@@ -50,9 +53,17 @@ GEM
     rack (3.2.7)
     rainbow (3.1.1)
     rake (13.4.2)
+    rbi (0.4.3)
+      prism (~> 1.0)
+      rbs (>= 4.0.1)
+    rbs (4.2.0)
+      logger
+      prism (>= 1.6.0)
+      tsort
     redis-client (0.30.1)
       connection_pool
     regexp_parser (2.12.0)
+    rexml (3.4.4)
     rspec (3.13.2)
       rspec-core (~> 3.13.0)
       rspec-expectations (~> 3.13.0)
@@ -80,10 +91,32 @@ GEM
     rubocop-ast (1.50.0)
       parser (>= 3.3.7.2)
       prism (~> 1.7)
+    rubocop-gusto (11.9.0)
+      code_teams
+      lint_roller
+      rubocop (>= 1.76)
+      rubocop-performance
+      rubocop-rake
+      rubocop-rspec
+      rubocop-sorbet (>= 0.13.0)
+      smart_todo
+      thor
     rubocop-performance (1.26.1)
       lint_roller (~> 1.1)
       rubocop (>= 1.75.0, < 2.0)
       rubocop-ast (>= 1.47.1, < 2.0)
+    rubocop-rake (0.7.1)
+      lint_roller (~> 1.1)
+      rubocop (>= 1.72.1)
+    rubocop-rspec (3.10.2)
+      lint_roller (~> 1.1)
+      regexp_parser (>= 2.0)
+      rubocop (~> 1.86, >= 1.86.2)
+    rubocop-sorbet (0.16.0)
+      lint_roller
+      rbi (~> 0.4)
+      rubocop (>= 1.75.2)
+      spoom (~> 1.8)
     ruby-progressbar (1.13.0)
     rubyzip (3.5.0)
     securerandom (0.4.1)
@@ -93,19 +126,28 @@ GEM
       logger (>= 1.7.0)
       rack (>= 3.2.0)
       redis-client (>= 0.29.0)
+    smart_todo (1.11.0)
+      prism (~> 1.0)
+    sorbet (0.6.13508)
+      sorbet-static (= 0.6.13508)
+    sorbet-runtime (0.6.13508)
+    sorbet-static (0.6.13508-aarch64-linux)
+    sorbet-static (0.6.13508-universal-darwin)
+    sorbet-static (0.6.13508-x86_64-linux)
+    sorbet-static-and-runtime (0.6.13508)
+      sorbet (= 0.6.13508)
+      sorbet-runtime (= 0.6.13508)
+    spoom (1.8.9)
+      erubi (>= 1.10.0)
+      prism (>= 0.28.0)
+      rbi (>= 0.4.2)
+      rbs (>= 4.0.0.dev.5)
+      rexml (>= 3.2.6)
+      sorbet-static-and-runtime (>= 0.5.10187)
+      thor (>= 0.19.2)
     stackprof (0.2.28)
-    standard (1.56.0)
-      language_server-protocol (~> 3.17.0.2)
-      lint_roller (~> 1.0)
-      rubocop (~> 1.88.0)
-      standard-custom (~> 1.0.0)
-      standard-performance (~> 1.8)
-    standard-custom (1.0.2)
-      lint_roller (~> 1.0)
-      rubocop (~> 1.50)
-    standard-performance (1.9.0)
-      lint_roller (~> 1.1)
-      rubocop-performance (~> 1.26.0)
+    thor (1.5.0)
+    tsort (0.2.0)
     tzinfo (2.0.6)
       concurrent-ruby (~> 1.0)
     unicode-display_width (3.2.0)
@@ -114,16 +156,19 @@ GEM
     uri (1.1.1)
 
 PLATFORMS
-  ruby
+  aarch64-linux
+  arm64-darwin
+  x86_64-darwin
+  x86_64-linux
 
 DEPENDENCIES
   activejob
   rake (~> 13.4)
   rspec
+  rubocop-gusto
   rubyzip
   sidekiq
   singed!
-  standard
 
 BUNDLED WITH
    4.0.15
diff --git a/Rakefile b/Rakefile
index 638ee1b..d45be73 100644
--- a/Rakefile
+++ b/Rakefile
@@ -52,4 +52,4 @@ end
 Rake::Task[:build].enhance ["speedscope:vendor"]
 Rake::Task[:clobber].enhance ["speedscope:clobber"]
 
-task default: %i[]
+task default: %i()
diff --git a/bin/rspec b/bin/rspec
index cb53ebe..3fd48d8 100755
--- a/bin/rspec
+++ b/bin/rspec
@@ -16,8 +16,10 @@ if File.file?(bundle_binstub)
   if File.read(bundle_binstub, 300).include?("This file was generated by Bundler")
     load(bundle_binstub)
   else
-    abort("Your `bin/bundle` was not generated by Bundler, so this binstub cannot run.
-Replace `bin/bundle` by running `bundle binstubs bundler --force`, then run this command again.")
+    abort(
+      "Your `bin/bundle` was not generated by Bundler, so this binstub cannot run.
+Replace `bin/bundle` by running `bundle binstubs bundler --force`, then run this command again."
+    )
   end
 end
 
diff --git a/exe/singed b/exe/singed
index 3fc6b7c..4cf651a 100755
--- a/exe/singed
+++ b/exe/singed
@@ -1,4 +1,5 @@
 #!/usr/bin/env ruby
+# frozen_string_literal: true
 
 require "singed/cli"
 if Singed::CLI.chdir_rails_root
diff --git a/lib/singed.rb b/lib/singed.rb
index f2a48af..a3dabc7 100644
--- a/lib/singed.rb
+++ b/lib/singed.rb
@@ -4,7 +4,10 @@
 require "stackprof"
 
 module Singed
-  extend self
+  # Methods defined with plain `def` below are both module methods (Singed.start) and public
+  # instance methods of Singed, which is how the gem has shipped since its first release.
+  # `class << self` would remove those instance methods for anyone who includes or extends Singed.
+  extend self # rubocop:disable Style/ModuleFunction
 
   # Where should flamegraphs be saved?
   def output_directory=(directory)
@@ -49,7 +52,7 @@ def start(label = nil, ignore_gc: false, interval: 1000)
     return unless enabled?
     return if profiling?
 
-    @current_flamegraph = Flamegraph.new(label: label, ignore_gc: ignore_gc, interval: interval)
+    @current_flamegraph = Flamegraph.new(label:, ignore_gc:, interval:)
     @current_flamegraph.tap(&:start)
   end
 
diff --git a/lib/singed/backtrace_cleaner_ext.rb b/lib/singed/backtrace_cleaner_ext.rb
index 0042fed..52ae9a3 100644
--- a/lib/singed/backtrace_cleaner_ext.rb
+++ b/lib/singed/backtrace_cleaner_ext.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module ActiveSupport
   class BacktraceCleaner
     def filter_line(line)
diff --git a/lib/singed/cli.rb b/lib/singed/cli.rb
index 7976106..17c3232 100644
--- a/lib/singed/cli.rb
+++ b/lib/singed/cli.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require "shellwords"
 require "tmpdir"
 require "optionparser"
@@ -75,14 +77,14 @@ def run
         format: "speedscope",
         file: filename.to_s,
         rate: @rate,
-        silent: nil
+        silent: nil,
       }
 
       rbspy_args = [
         "record",
         *options.map { |k, v| ["--#{k}", v].compact }.flatten,
         "--",
-        *argv
+        *argv,
       ]
 
       loop do
@@ -92,9 +94,9 @@ def run
         prompt_password
       end
 
-      rbspy = lambda do
+      rbspy = -> do
         # don't run things with spring, because it forks and rbspy won't see it
-        sudo ["rbspy", *rbspy_args], reason: "Singed needs to run as root, but will drop permissions back to your user.", env: {"DISABLE_SPRING" => "1"}
+        sudo ["rbspy", *rbspy_args], reason: "Singed needs to run as root, but will drop permissions back to your user.", env: { "DISABLE_SPRING" => "1" }
       end
 
       if defined?(Bundler)
@@ -122,7 +124,7 @@ def run
       end
       filename.write(JSON.dump(json))
 
-      flamegraph = Singed::Flamegraph.new(filename: filename)
+      flamegraph = Singed::Flamegraph.new(filename:)
       flamegraph.open
     end
 
@@ -153,7 +155,7 @@ def sudo(system_args, reason:, env: {})
       sudo_args = [
         "sudo",
         "--preserve-env",
-        *system_args.map(&:to_s)
+        *system_args.map(&:to_s),
       ]
 
       puts "$ #{Shellwords.join(sudo_args)}"
diff --git a/lib/singed/controller_ext.rb b/lib/singed/controller_ext.rb
index f630fb5..2e51b0f 100644
--- a/lib/singed/controller_ext.rb
+++ b/lib/singed/controller_ext.rb
@@ -1,14 +1,16 @@
+# frozen_string_literal: true
+
+require "active_support/concern"
+
 module Singed
   module ControllerExt
-    def self.included(base)
-      base.extend(ClassMethods)
-    end
+    extend ActiveSupport::Concern
 
     module ClassMethods
       # Define an around_action to generate flamegraph for a controller action.
       def flamegraph(target_action, ignore_gc: false, interval: 1000)
         around_action(only: target_action) do |controller, action|
-          controller.flamegraph(ignore_gc: ignore_gc, interval: interval, &action)
+          controller.flamegraph(ignore_gc:, interval:, &action)
         end
       end
     end
diff --git a/lib/singed/flamegraph.rb b/lib/singed/flamegraph.rb
index d5d78ec..3f79bfa 100644
--- a/lib/singed/flamegraph.rb
+++ b/lib/singed/flamegraph.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module Singed
   class Flamegraph
     attr_accessor :profile, :filename
@@ -17,8 +19,8 @@ def initialize(label: nil, ignore_gc: false, interval: 1000, filename: nil)
       else
         @ignore_gc = ignore_gc
         @interval = interval
-        @time = Time.now # rubocop:disable Rails/TimeZone
-        @filename = self.class.generate_filename(label: label, time: @time)
+        @time = Time.now
+        @filename = self.class.generate_filename(label:, time: @time)
       end
     end
 
@@ -69,11 +71,11 @@ def open_command
       Singed::Speedscope.open_command(@filename)
     end
 
-    def self.generate_filename(label: nil, time: Time.now) # rubocop:disable Rails/TimeZone
+    def self.generate_filename(label: nil, time: Time.now)
       formatted_time = time.strftime("%Y%m%d%H%M%S-%6N")
       basename_parts = ["speedscope", label, formatted_time].compact
 
-      file = Singed.output_directory.join("#{basename_parts.join("-")}.json")
+      file = Singed.output_directory.join("#{basename_parts.join('-')}.json")
       # convert to relative directory if it's an absolute path and within the current
       pwd = Pathname.pwd
       file = file.relative_path_from(pwd) if file.absolute? && file.to_s.start_with?(pwd.to_s)
diff --git a/lib/singed/kernel_ext.rb b/lib/singed/kernel_ext.rb
index c566b92..e1cb741 100644
--- a/lib/singed/kernel_ext.rb
+++ b/lib/singed/kernel_ext.rb
@@ -1,6 +1,8 @@
+# frozen_string_literal: true
+
 module Kernel
   def flamegraph(label = nil, open: true, ignore_gc: false, interval: 1000, io: $stdout, &block)
-    fg = Singed::Flamegraph.new(label: label, ignore_gc: ignore_gc, interval: interval)
+    fg = Singed::Flamegraph.new(label:, ignore_gc:, interval:)
     result = fg.record(&block)
     fg.save
 
diff --git a/lib/singed/rack_middleware.rb b/lib/singed/rack_middleware.rb
index f267974..d497e62 100644
--- a/lib/singed/rack_middleware.rb
+++ b/lib/singed/rack_middleware.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 # Rack Middleware
 
 require "rack"
diff --git a/lib/singed/railtie.rb b/lib/singed/railtie.rb
index 5fae6e0..45a5ea6 100644
--- a/lib/singed/railtie.rb
+++ b/lib/singed/railtie.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require "singed/backtrace_cleaner_ext"
 require "singed/controller_ext"
 
diff --git a/lib/singed/report.rb b/lib/singed/report.rb
index cbf2753..53b90dd 100644
--- a/lib/singed/report.rb
+++ b/lib/singed/report.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module Singed
   class Report < StackProf::Report
     def filter!
@@ -27,7 +29,7 @@ def filter!
       # list.each{ |_addr, frame| frame[:edges]&.delete_if{ |k,v| list[k].nil? } }
       # end copy-pasted section
 
-      list.each do |_addr, frame|
+      list.each_value do |frame|
         frame[:file] = Singed.filter_line(frame[:file])
       end
 
diff --git a/lib/singed/rspec.rb b/lib/singed/rspec.rb
index 16aee70..4978bde 100644
--- a/lib/singed/rspec.rb
+++ b/lib/singed/rspec.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require "singed"
 
 RSpec.configure do |config|
diff --git a/lib/singed/sidekiq.rb b/lib/singed/sidekiq.rb
index ac478ba..e65f15f 100644
--- a/lib/singed/sidekiq.rb
+++ b/lib/singed/sidekiq.rb
@@ -5,7 +5,9 @@ module Sidekiq
     class ServerMiddleware
       include ::Sidekiq::ServerMiddleware
 
-      def call(job_instance, job_payload, queue, &block)
+      TRUTHY_STRINGS = %w(true 1 yes).freeze
+
+      def call(job_instance, job_payload, _queue, &block)
         return block.call unless capture_flamegraph?(job_instance, job_payload)
 
         flamegraph(flamegraph_label(job_instance, job_payload), &block)
@@ -13,8 +15,6 @@ def call(job_instance, job_payload, queue, &block)
 
       private
 
-      TRUTHY_STRINGS = %w[true 1 yes].freeze
-
       def capture_flamegraph?(job_instance, job_payload)
         return TRUTHY_STRINGS.include?(job_payload["x-singed"].to_s) if job_payload.key?("x-singed")
 
diff --git a/singed.gemspec b/singed.gemspec
index 8895069..050e805 100644
--- a/singed.gemspec
+++ b/singed.gemspec
@@ -13,12 +13,12 @@ Gem::Specification.new do |spec|
   spec.metadata = {
     "source_code_uri" => "https://github.com/rubyatscale/singed",
     "bug_tracker_uri" => "https://github.com/rubyatscale/singed/issues",
-    "homepage_uri" => "https://github.com/rubyatscale/singed"
+    "homepage_uri" => "https://github.com/rubyatscale/singed",
   }
 
   spec.files = Dir["README.md", "*.gemspec", "lib/**/*", "exe/**/*", "vendor/speedscope/**/*"]
   spec.bindir = "exe"
-  spec.executables = spec.files.grep(%r{\Aexe/}) { |f| File.basename(f) }
+  spec.executables = spec.files.grep(%r(\Aexe/)) { |f| File.basename(f) }
   spec.require_paths = ["lib"]
 
   spec.add_dependency "stackprof", ">= 0.2.13"
diff --git a/spec/singed/controller_ext_spec.rb b/spec/singed/controller_ext_spec.rb
new file mode 100644
index 0000000..c7a3672
--- /dev/null
+++ b/spec/singed/controller_ext_spec.rb
@@ -0,0 +1,41 @@
+# frozen_string_literal: true
+
+require "singed/controller_ext"
+
+RSpec.describe Singed::ControllerExt do
+  let(:controller_class) do
+    Class.new do
+      def self.around_action(**options, &block)
+        around_actions << [options, block]
+      end
+
+      def self.around_actions
+        @around_actions ||= []
+      end
+
+      include Singed::ControllerExt
+    end
+  end
+
+  # Kernel#flamegraph makes every object respond to :flamegraph, so check where the method comes from.
+  it "adds the flamegraph class method when included" do
+    expect(controller_class.method(:flamegraph).owner).to eq(Singed::ControllerExt::ClassMethods)
+  end
+
+  it "wraps the target action in a flamegraph" do
+    controller_class.flamegraph(:show, ignore_gc: true, interval: 500)
+
+    expect(controller_class.around_actions.size).to eq(1)
+    options, callback = controller_class.around_actions.first
+    expect(options).to eq(only: :show)
+
+    controller = controller_class.new
+    allow(controller).to receive(:flamegraph) { |**, &action| action.call }
+    action_ran = false
+
+    callback.call(controller, -> { action_ran = true })
+
+    expect(controller).to have_received(:flamegraph).with(ignore_gc: true, interval: 500)
+    expect(action_ran).to be(true)
+  end
+end
diff --git a/spec/singed/kernel_ext_spec.rb b/spec/singed/kernel_ext_spec.rb
index 98d8552..5d48999 100644
--- a/spec/singed/kernel_ext_spec.rb
+++ b/spec/singed/kernel_ext_spec.rb
@@ -1,7 +1,10 @@
-describe Kernel, "extension" do
-  let(:flamegraph) {
+# frozen_string_literal: true
+
+describe Kernel do
+  let(:flamegraph) do
     instance_double(Singed::Flamegraph)
-  }
+  end
+  let(:io) { StringIO.new }
 
   before do
     allow(Singed::Flamegraph).to receive(:new).and_return(flamegraph)
@@ -12,46 +15,44 @@
     allow(flamegraph).to receive(:filename)
   end
 
-  let(:io) { StringIO.new }
-
   it "works without any arguments" do
     # * except what's needed to test
-    # note: use Object.new to get the actual flamegraph kernel extension, instead of the rspec-specific flamegraph
-    Object.new.flamegraph io: io do
+    # NOTE: use Object.new to get the actual flamegraph kernel extension, instead of the rspec-specific flamegraph
+    Object.new.flamegraph(io:) do
     end
 
     expect(Singed::Flamegraph).to have_received(:new).with(label: nil, ignore_gc: false, interval: 1000)
   end
 
   it "works with explicit arguments" do
-    # note: use Object.new to get the actual flamegraph kernel extension, instead of the rspec-specific flamegraph
-    Object.new.flamegraph "yellowjackets", ignore_gc: true, interval: 2000, io: io do
+    # NOTE: use Object.new to get the actual flamegraph kernel extension, instead of the rspec-specific flamegraph
+    Object.new.flamegraph("yellowjackets", ignore_gc: true, interval: 2000, io:) do
     end
 
     expect(Singed::Flamegraph).to have_received(:new).with(label: "yellowjackets", ignore_gc: true, interval: 2000)
   end
 
-  context "default" do
+  context "with default options" do
     it "opens" do
-      Object.new.flamegraph open: true, io: io do
+      Object.new.flamegraph(io:) do
       end
 
       expect(flamegraph).to have_received(:open)
     end
   end
 
-  context "open: true" do
+  context "with open: true" do
     it "opens" do
-      Object.new.flamegraph open: true, io: io do
+      Object.new.flamegraph(open: true, io:) do
       end
 
       expect(flamegraph).to have_received(:open)
     end
   end
 
-  context "open: false" do
+  context "with open: false" do
     it "doesn't open" do
-      Object.new.flamegraph open: false, io: io do
+      Object.new.flamegraph(open: false, io:) do
       end
 
       expect(flamegraph).to_not have_received(:open)
diff --git a/spec/singed/middleware_spec.rb b/spec/singed/rack_middleware_spec.rb
similarity index 89%
rename from spec/singed/middleware_spec.rb
rename to spec/singed/rack_middleware_spec.rb
index 0e54183..037aa62 100644
--- a/spec/singed/middleware_spec.rb
+++ b/spec/singed/rack_middleware_spec.rb
@@ -5,8 +5,8 @@
     instance.call(env)
   end
 
-  let(:app_response) { [200, {"content-type" => "text/plain"}, ["OK"]] }
-  let(:app) { ->(*) { app_response } }
+  let(:app_response) { [200, { "content-type" => "text/plain" }, ["OK"]] }
+  let(:app) { -> (*) { app_response } }
   let(:instance) { described_class.new(app) }
   let(:env) { Rack::MockRequest.env_for("/", headers) }
   let(:headers) { {} }
@@ -22,7 +22,7 @@
 
   context "when enabled" do
     before do
-      allow_any_instance_of(Singed::Flamegraph).to receive(:open)
+      allow(Singed::Speedscope).to receive(:open)
       allow(instance).to receive(:capture_flamegraph?).and_return(true)
     end
 
@@ -47,7 +47,7 @@
     it { is_expected.to be false }
 
     context "when HTTP_X_SINGED is true" do
-      let(:headers) { {"HTTP_X_SINGED" => "true"} }
+      let(:headers) { { "HTTP_X_SINGED" => "true" } }
 
       it { is_expected.to be true }
     end
@@ -66,7 +66,7 @@
         described_class.remove_instance_variable(:@always_capture) if described_class.instance_variable_defined?(:@always_capture)
       end
 
-      %w[true 1 yes].each do |truthy_value|
+      %w(true 1 yes).each do |truthy_value|
         context "when SINGED_MIDDLEWARE_ALWAYS_CAPTURE=#{truthy_value}" do
           before { ENV["SINGED_MIDDLEWARE_ALWAYS_CAPTURE"] = truthy_value }
 
diff --git a/spec/singed/sidekiq_spec.rb b/spec/singed/sidekiq/server_middleware_spec.rb
similarity index 63%
rename from spec/singed/sidekiq_spec.rb
rename to spec/singed/sidekiq/server_middleware_spec.rb
index 72be9ae..eb93a13 100644
--- a/spec/singed/sidekiq_spec.rb
+++ b/spec/singed/sidekiq/server_middleware_spec.rb
@@ -1,36 +1,41 @@
 # frozen_string_literal: true
 
-require "spec_helper"
 require "sidekiq"
 require "active_job"
 require "singed/sidekiq"
-require_relative "../support/sidekiq"
+require_relative "../../support/sidekiq"
 
-RSpec.describe Singed::Sidekiq::ServerMiddleware, sidekiq: true do
+RSpec.describe Singed::Sidekiq::ServerMiddleware, :sidekiq do
   subject { job_class.set(job_modifiers).perform_async(*job_args) }
 
   let(:job_class) { SidekiqPlainJob }
   let(:job_args) { [] }
   let(:job_modifiers) { {} }
+  let(:middleware) { described_class.new }
+  let(:job) { job_class.new }
 
   before do
-    allow_any_instance_of(described_class).to receive(:flamegraph) { |*, &block| block.call }
-    allow_any_instance_of(job_class).to receive(:perform).and_call_original
+    # Sidekiq builds a new middleware instance per job, and both Sidekiq and ActiveJob build the
+    # job instance themselves, so hand them the instances the examples assert against.
+    allow(described_class).to receive(:new).and_return(middleware)
+    allow(middleware).to receive(:flamegraph) { |*, &block| block.call }
+    allow(job_class).to receive(:new).and_return(job)
+    allow(job).to receive(:perform).and_call_original
   end
 
   context "with plain Sidekiq jobs" do
     it "doesn't capture flamegraph by default" do
-      expect_any_instance_of(described_class).not_to receive(:flamegraph)
-      expect_any_instance_of(job_class).to receive(:perform)
+      expect(middleware).not_to receive(:flamegraph)
+      expect(job).to receive(:perform)
       subject
     end
 
     context "when x-singed payload is true" do
-      let(:job_modifiers) { {"x-singed" => true} }
+      let(:job_modifiers) { { "x-singed" => true } }
 
       it "wraps execution in flamegraph when x-singed is true" do
-        expect_any_instance_of(described_class).to receive(:flamegraph)
-        expect_any_instance_of(job_class).to receive(:perform)
+        expect(middleware).to receive(:flamegraph)
+        expect(job).to receive(:perform)
         subject
       end
     end
@@ -40,17 +45,17 @@
     let(:job_class) { SidekiqFlamegraphJob }
 
     it "doesn't capture when capture_flamegraph? returns false" do
-      expect_any_instance_of(described_class).not_to receive(:flamegraph)
-      expect_any_instance_of(job_class).to receive(:perform)
+      expect(middleware).not_to receive(:flamegraph)
+      expect(job).to receive(:perform)
       subject
     end
 
     context "when payload satisfies capture_flamegraph?" do
-      let(:job_modifiers) { {"x-flamegraph" => true} }
+      let(:job_modifiers) { { "x-flamegraph" => true } }
 
       it "wraps execution in flamegraph when capture_flamegraph? returns true" do
-        expect_any_instance_of(described_class).to receive(:flamegraph)
-        expect_any_instance_of(job_class).to receive(:perform)
+        expect(middleware).to receive(:flamegraph)
+        expect(job).to receive(:perform)
         subject
       end
     end
@@ -72,8 +77,8 @@
       before { ENV["SINGED_MIDDLEWARE_ALWAYS_CAPTURE"] = "true" }
 
       it "wraps execution in flamegraph" do
-        expect_any_instance_of(described_class).to receive(:flamegraph)
-        expect_any_instance_of(job_class).to receive(:perform)
+        expect(middleware).to receive(:flamegraph)
+        expect(job).to receive(:perform)
         subject
       end
     end
@@ -82,8 +87,8 @@
       before { ENV["SINGED_MIDDLEWARE_ALWAYS_CAPTURE"] = "false" }
 
       it "doesn't capture flamegraph" do
-        expect_any_instance_of(described_class).not_to receive(:flamegraph)
-        expect_any_instance_of(job_class).to receive(:perform)
+        expect(middleware).not_to receive(:flamegraph)
+        expect(job).to receive(:perform)
         subject
       end
     end
@@ -96,8 +101,8 @@
       let(:job_class) { ActiveJobPlainJob }
 
       it "doesn't capture flamegraph by default" do
-        expect_any_instance_of(described_class).not_to receive(:flamegraph)
-        expect_any_instance_of(job_class).to receive(:perform)
+        expect(middleware).not_to receive(:flamegraph)
+        expect(job).to receive(:perform)
         subject
       end
 
@@ -105,8 +110,8 @@
         let(:job_class) { ActiveJobFlamegraphJob }
 
         it "wraps execution in flamegraph when capture_flamegraph? returns true" do
-          expect_any_instance_of(described_class).to receive(:flamegraph)
-          expect_any_instance_of(job_class).to receive(:perform)
+          expect(middleware).to receive(:flamegraph)
+          expect(job).to receive(:perform)
           subject
         end
       end
@@ -115,8 +120,8 @@
         let(:job_class) { ActiveJobNoFlamegraphJob }
 
         it "doesn't capture when capture_flamegraph? returns false" do
-          expect_any_instance_of(described_class).not_to receive(:flamegraph)
-          expect_any_instance_of(job_class).to receive(:perform)
+          expect(middleware).not_to receive(:flamegraph)
+          expect(job).to receive(:perform)
           subject
         end
       end
@@ -137,8 +142,8 @@
           before { ENV["SINGED_MIDDLEWARE_ALWAYS_CAPTURE"] = "true" }
 
           it "wraps execution in flamegraph" do
-            expect_any_instance_of(described_class).to receive(:flamegraph)
-            expect_any_instance_of(job_class).to receive(:perform)
+            expect(middleware).to receive(:flamegraph)
+            expect(job).to receive(:perform)
             subject
           end
         end
@@ -147,8 +152,8 @@
           before { ENV["SINGED_MIDDLEWARE_ALWAYS_CAPTURE"] = "false" }
 
           it "doesn't capture flamegraph" do
-            expect_any_instance_of(described_class).not_to receive(:flamegraph)
-            expect_any_instance_of(job_class).to receive(:perform)
+            expect(middleware).not_to receive(:flamegraph)
+            expect(job).to receive(:perform)
             subject
           end
         end
diff --git a/spec/singed/speedscope_spec.rb b/spec/singed/speedscope_spec.rb
index ee292a8..24665d3 100644
--- a/spec/singed/speedscope_spec.rb
+++ b/spec/singed/speedscope_spec.rb
@@ -21,7 +21,7 @@
 
         described_class.open(profile_path)
 
-        expect(described_class).to have_received(:system).with(described_class.send(:os_open_command), %r{\Afile://})
+        expect(described_class).to have_received(:system).with(described_class.__send__(:os_open_command), %r(\Afile://))
       end
     end
 
@@ -42,36 +42,36 @@
 
   describe ".os_open_command" do
     it "returns a command and does not raise" do
-      expect { described_class.send(:os_open_command) }.not_to raise_error
-      expect(described_class.send(:os_open_command)).to match(/\A(start|open|xdg-open)\z/)
+      expect { described_class.__send__(:os_open_command) }.not_to raise_error
+      expect(described_class.__send__(:os_open_command)).to match(/\A(start|open|xdg-open)\z/)
     end
 
     context "when host_os is stubbed" do
-      subject { described_class.send(:os_open_command) }
+      subject { described_class.__send__(:os_open_command) }
 
       before do
         allow(RbConfig::CONFIG).to receive(:[]).with("host_os").and_return(stubbed_os)
       end
 
-      context "on Windows" do
+      context "when running on Windows" do
         let(:stubbed_os) { "mingw32" }
 
         it { is_expected.to eq("start") }
       end
 
-      context "on MacOS" do
+      context "when running on macOS" do
         let(:stubbed_os) { "darwin22.0" }
 
         it { is_expected.to eq("open") }
       end
 
-      context "on Linux" do
+      context "when running on Linux" do
         let(:stubbed_os) { "linux-gnu" }
 
         it { is_expected.to eq("xdg-open") }
       end
 
-      context "on unsupported OS" do
+      context "when running on an unsupported OS" do
         let(:stubbed_os) { "unknown-os" }
 
         it "raises error" do
diff --git a/spec/spec_helper.rb b/spec/spec_helper.rb
index 72cb8f2..4eeeb21 100644
--- a/spec/spec_helper.rb
+++ b/spec/spec_helper.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 # This file was generated by the `rspec --init` command. Conventionally, all
 # specs live under a `spec` directory, which RSpec adds to the `$LOAD_PATH`.
 # The generated `.rspec` file contains `--require spec_helper` which will cause
diff --git a/spec/support/sidekiq.rb b/spec/support/sidekiq.rb
index c813758..b386b58 100644
--- a/spec/support/sidekiq.rb
+++ b/spec/support/sidekiq.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require "singed/sidekiq"
 
 RSpec.configure do |config|
@@ -19,7 +21,6 @@
 
 # Sidekiq doesn't invoke middlewares in inline testingmode, so we need to invoke it oursleves
 module SidekiqTestingInlineWithMiddlewares
-  # rubocop:disable Metrics/AbcSize
   def push(job)
     return super unless Sidekiq::Testing.inline?
 
@@ -34,7 +35,6 @@ def push(job)
     end
     job["jid"]
   end
-  # rubocop:enable Metrics/AbcSize
 end
 
 class SidekiqPlainJob