diff --git a/.github/workflows/gem_push.yml b/.github/workflows/gem_push.yml
index 9e22ccf27..691475212 100644
--- a/.github/workflows/gem_push.yml
+++ b/.github/workflows/gem_push.yml
@@ -20,7 +20,7 @@ jobs:
       id-token: write
     steps:
       - uses: actions/checkout@v6
-      - uses: ruby/setup-ruby@v1
+      - uses: ruby/setup-ruby@v1.302.0
         with:
           ruby-version: ruby
           bundler-cache: true
diff --git a/.github/workflows/lint.yml b/.github/workflows/lint.yml
index 386f03e46..6db9d37b0 100644
--- a/.github/workflows/lint.yml
+++ b/.github/workflows/lint.yml
@@ -16,7 +16,7 @@ jobs:
     steps:
       - uses: actions/checkout@v6
       - name: Set up Ruby
-        uses: ruby/setup-ruby@v1
+        uses: ruby/setup-ruby@v1.302.0
         with:
           ruby-version: "3.4"
           bundler-cache: true
diff --git a/.github/workflows/mutant.yml b/.github/workflows/mutant.yml
index 7c0819f1e..01b3a9945 100644
--- a/.github/workflows/mutant.yml
+++ b/.github/workflows/mutant.yml
@@ -16,7 +16,7 @@ jobs:
     steps:
     - uses: actions/checkout@v6
     - name: Set up Ruby
-      uses: ruby/setup-ruby@v1
+      uses: ruby/setup-ruby@v1.302.0
       with:
         ruby-version: '3.4'
         bundler-cache: true
diff --git a/.github/workflows/test.yml b/.github/workflows/test.yml
index 1e1fe605c..e91d689a1 100644
--- a/.github/workflows/test.yml
+++ b/.github/workflows/test.yml
@@ -19,7 +19,7 @@ jobs:
     steps:
     - uses: actions/checkout@v6
     - name: Set up Ruby
-      uses: ruby/setup-ruby@v1
+      uses: ruby/setup-ruby@v1.302.0
       with:
         ruby-version: ${{ matrix.ruby-version }}
         bundler-cache: true # runs 'bundle install' and caches installed gems automatically
diff --git a/.github/workflows/typecheck.yml b/.github/workflows/typecheck.yml
index 4caa209ad..6808a6440 100644
--- a/.github/workflows/typecheck.yml
+++ b/.github/workflows/typecheck.yml
@@ -16,7 +16,7 @@ jobs:
     steps:
     - uses: actions/checkout@v6
     - name: Set up Ruby
-      uses: ruby/setup-ruby@v1
+      uses: ruby/setup-ruby@v1.302.0
       with:
         ruby-version: '3.4'
         bundler-cache: true
diff --git a/.github/workflows/yardstick.yml b/.github/workflows/yardstick.yml
index 823619873..36a8f8321 100644
--- a/.github/workflows/yardstick.yml
+++ b/.github/workflows/yardstick.yml
@@ -16,7 +16,7 @@ jobs:
     steps:
     - uses: actions/checkout@v6
     - name: Set up Ruby
-      uses: ruby/setup-ruby@v1
+      uses: ruby/setup-ruby@v1.302.0
       with:
         ruby-version: '3.4'
         bundler-cache: true
diff --git a/.mutant.yml b/.mutant.yml
index 887f1f2ed..85b8cc167 100644
--- a/.mutant.yml
+++ b/.mutant.yml
@@ -13,6 +13,9 @@ includes:
 
 usage: opensource
 
+mutation:
+  operators: full
+
 matcher:
   subjects:
     - Twitter*
diff --git a/lib/twitter/base.rb b/lib/twitter/base.rb
index 606863099..4d9cb985c 100644
--- a/lib/twitter/base.rb
+++ b/lib/twitter/base.rb
@@ -165,7 +165,7 @@ def initialize(attrs = nil)
     # @param method [String, Symbol] Message to send to the object
     # @return [Object, nil]
     def [](method)
-      location = caller_locations(1, 1)&.first
+      location, = caller_locations(1, 1)
       warn "#{location&.path}:#{location&.lineno}: [DEPRECATION] #[#{method.inspect}] is deprecated. Use ##{method} to fetch the value."
       public_send(method.to_sym)
     rescue NoMethodError
diff --git a/lib/twitter/profile.rb b/lib/twitter/profile.rb
index bf7c8f97b..14d2eb007 100644
--- a/lib/twitter/profile.rb
+++ b/lib/twitter/profile.rb
@@ -145,7 +145,7 @@ def insecure_uri(uri)
     # @param size [Symbol] The size
     # @return [String]
     def profile_image_suffix(size)
-      (size.to_sym == :original) ? '\\1' : "_#{size}\\1"
+      {original: '\\1'}.fetch(size.to_sym) { "_#{size}\\1" }
     end
   end
 end
diff --git a/lib/twitter/rest/direct_messages.rb b/lib/twitter/rest/direct_messages.rb
index 580af966f..d8435f74d 100644
--- a/lib/twitter/rest/direct_messages.rb
+++ b/lib/twitter/rest/direct_messages.rb
@@ -68,7 +68,7 @@ def direct_messages_list(options = {})
       # @return [Array<Twitter::DirectMessage>] Direct messages received
       def direct_messages_received(options = {})
         limit = options.fetch(:count, 20)
-        direct_messages_list(options).select { |dm| dm.recipient_id == user_id }.first(limit)
+        direct_messages_list(options).select { |dm| dm.recipient_id.eql?(user_id) }.first(limit)
       end
 
       # Returns Direct Messages sent by the authenticated user
@@ -87,7 +87,7 @@ def direct_messages_received(options = {})
       # @return [Array<Twitter::DirectMessage>] Direct messages sent
       def direct_messages_sent(options = {})
         limit = options.fetch(:count, 20)
-        direct_messages_list(options).select { |dm| dm.sender_id == user_id }.first(limit)
+        direct_messages_list(options).select { |dm| dm.sender_id.eql?(user_id) }.first(limit)
       end
 
       # Returns a direct message
@@ -241,7 +241,7 @@ def create_direct_message(user_id, text, options = {})
       def create_direct_message_event(*args)
         arguments = Arguments.new(args)
         options = arguments.options
-        options[:event] = {type: "message_create", message_create: {target: {recipient_id: extract_id(arguments.fetch(0))}, message_data: {text: arguments.fetch(1)}}} if arguments.length == 2
+        options[:event] = {type: "message_create", message_create: {target: {recipient_id: extract_id(arguments.fetch(0))}, message_data: {text: arguments.fetch(1)}}} if arguments.length.eql?(2)
         response = Request.new(self, :json_post, "/1.1/direct_messages/events/new.json", options).perform
         DirectMessageEvent.new(response)
       end
diff --git a/lib/twitter/rest/favorites.rb b/lib/twitter/rest/favorites.rb
index b00ad2f60..ee50876da 100644
--- a/lib/twitter/rest/favorites.rb
+++ b/lib/twitter/rest/favorites.rb
@@ -37,7 +37,7 @@ module Favorites
       #   @option options [Integer] :since_id Returns results with an ID greater than (that is, more recent than) the specified ID.
       def favorites(*args)
         arguments = Arguments.new(args)
-        merge_user!(arguments.options, arguments.pop) if arguments.last
+        merge_user!(arguments.options, arguments.pop) if arguments.any?
         perform_get_with_objects("/1.1/favorites/list.json", arguments.options, Tweet)
       end
 
diff --git a/lib/twitter/rest/lists.rb b/lib/twitter/rest/lists.rb
index e9116e7fb..7ea308008 100644
--- a/lib/twitter/rest/lists.rb
+++ b/lib/twitter/rest/lists.rb
@@ -526,9 +526,10 @@ def list_from_response_with_users(path, args)
         members = arguments.pop
         merge_list!(options, arguments.pop)
         merge_owner!(options, arguments.pop)
-        pmap(members.each_slice(MAX_USERS_PER_REQUEST)) do |users|
+        *, result = pmap(members.each_slice(MAX_USERS_PER_REQUEST)) do |users|
           perform_post_with_object(path, merge_users(options, users), List)
-        end.last
+        end
+        result
       end
 
       # Take a list and merge it into the hash with the correct key
diff --git a/lib/twitter/rest/premium_search.rb b/lib/twitter/rest/premium_search.rb
index 059aaa38b..3418e09f7 100644
--- a/lib/twitter/rest/premium_search.rb
+++ b/lib/twitter/rest/premium_search.rb
@@ -28,7 +28,7 @@ module PremiumSearch
       def premium_search(query, options = {}, request_config = {})
         options = options.clone
         options[:maxResults] ||= MAX_TWEETS_PER_REQUEST
-        request_config[:request_method] = :json_post if request_config[:request_method].nil? || request_config.fetch(:request_method) == :post
+        request_config[:request_method] = :json_post if request_config[:request_method].nil? || request_config.fetch(:request_method).eql?(:post)
         request_config[:product] ||= "30day"
         path = "/1.1/tweets/search/#{request_config.fetch(:product)}/#{dev_environment}.json" # steep:ignore NoMethod
         request = Request.new(self, request_config.fetch(:request_method), path, options.merge(query:))
diff --git a/lib/twitter/rest/request.rb b/lib/twitter/rest/request.rb
index 22c472529..f5271902c 100644
--- a/lib/twitter/rest/request.rb
+++ b/lib/twitter/rest/request.rb
@@ -124,7 +124,7 @@ def perform
       # @api private
       # @return [Hash]
       def request_options
-        options = if @options_key == :form
+        options = if @options_key.eql?(:form)
           {form: HTTP::FormData.create(@options, encoder: FormEncoder.public_method(:encode))}
         else
           {@options_key => @options}
@@ -158,10 +158,10 @@ def merge_multipart_file!(options)
       # @return [void]
       def set_multipart_options!(request_method, options)
         if %i[multipart_post json_post].include?(request_method)
-          merge_multipart_file!(options) if request_method == :multipart_post
+          merge_multipart_file!(options) if request_method.eql?(:multipart_post)
           options = {} # : Hash[Symbol, untyped]
           @request_method = :post
-        elsif request_method == :json_put
+        elsif request_method.eql?(:json_put)
           @request_method = :put
         else
           @request_method = request_method
@@ -212,7 +212,7 @@ def fail_or_return_response_body(code, body, response)
       # @return [Twitter::Error, nil]
       def error(code, body, response)
         klass = Error::ERRORS[code]
-        if klass == Error::Forbidden
+        if klass.eql?(Error::Forbidden)
           forbidden_error(body, response)
         elsif !klass.nil?
           klass.from_response(body, response)
diff --git a/lib/twitter/rest/suggested_users.rb b/lib/twitter/rest/suggested_users.rb
index a0c0022fd..e094e3e4d 100644
--- a/lib/twitter/rest/suggested_users.rb
+++ b/lib/twitter/rest/suggested_users.rb
@@ -31,7 +31,7 @@ module SuggestedUsers
       #   @param options [Hash] A customizable set of options.
       def suggestions(*args)
         arguments = Arguments.new(args)
-        if arguments.last
+        if arguments.any?
           perform_get_with_object("/1.1/users/suggestions/#{arguments.pop}.json", arguments.options, Suggestion)
         else
           perform_get_with_objects("/1.1/users/suggestions.json", arguments.options, Suggestion)
diff --git a/lib/twitter/rest/trends.rb b/lib/twitter/rest/trends.rb
index ae09cc1f1..12b9599e4 100644
--- a/lib/twitter/rest/trends.rb
+++ b/lib/twitter/rest/trends.rb
@@ -25,7 +25,7 @@ module Trends
       def trends(id = 1, options = {})
         options = options.dup
         options[:id] = id
-        response = perform_get("/1.1/trends/place.json", options).first
+        response, = perform_get("/1.1/trends/place.json", options)
         TrendResults.new(response)
       end
       # @!method local_trends
diff --git a/lib/twitter/rest/tweets.rb b/lib/twitter/rest/tweets.rb
index 0d8336435..4ad21065d 100644
--- a/lib/twitter/rest/tweets.rb
+++ b/lib/twitter/rest/tweets.rb
@@ -335,7 +335,8 @@ def oembeds(*args)
       #   @param options [Hash] A customizable set of options.
       def retweeters_ids(*args)
         arguments = Arguments.new(args)
-        arguments.options[:id] ||= extract_id(arguments.first)
+        id, = arguments
+        arguments.options[:id] ||= extract_id(id)
         perform_get_with_cursor("/1.1/statuses/retweeters/ids.json", arguments.options, :ids)
       end
 
diff --git a/lib/twitter/rest/upload_utils.rb b/lib/twitter/rest/upload_utils.rb
index 23f430378..85856dd52 100644
--- a/lib/twitter/rest/upload_utils.rb
+++ b/lib/twitter/rest/upload_utils.rb
@@ -15,9 +15,9 @@ module UploadUtils
       # @return [Hash]
       def upload(media, media_category_prefix: "tweet")
         ext = File.extname(media)
-        return chunk_upload(media, "video/mp4", "#{media_category_prefix}_video") if ext == ".mp4"
-        return chunk_upload(media, "video/quicktime", "#{media_category_prefix}_video") if ext == ".mov"
-        return chunk_upload(media, "image/gif", "#{media_category_prefix}_gif") if ext == ".gif" && File.size(media) > 5_000_000
+        return chunk_upload(media, "video/mp4", "#{media_category_prefix}_video") if ext.eql?(".mp4")
+        return chunk_upload(media, "video/quicktime", "#{media_category_prefix}_video") if ext.eql?(".mov")
+        return chunk_upload(media, "image/gif", "#{media_category_prefix}_gif") if ext.eql?(".gif") && File.size(media) > 5_000_000
 
         Request.new(self, :multipart_post, "https://upload.twitter.com/1.1/media/upload.json", key: :media, file: media).perform
       end
diff --git a/lib/twitter/rest/users.rb b/lib/twitter/rest/users.rb
index 6a03a80e6..6d7d6f5ac 100644
--- a/lib/twitter/rest/users.rb
+++ b/lib/twitter/rest/users.rb
@@ -40,8 +40,8 @@ def settings(options = {})
         request_method = options.empty? ? :get : :post
         response = perform_request(request_method, "/1.1/account/settings.json", options)
         # https://dev.twitter.com/issues/59
-        empty_array = [] # : Array[untyped]
-        response[:trend_location] = response.fetch(:trend_location, empty_array).first
+        trend_location, = response[:trend_location]
+        response[:trend_location] = trend_location
         Settings.new(response)
       end
 
@@ -272,7 +272,7 @@ def users(*args)
       #   @option options [Boolean, String, Integer] :skip_status Do not include user's Tweets when set to true, 't' or 1.
       def user(*args)
         arguments = Arguments.new(args)
-        if arguments.last || user_id?
+        if arguments.any? || user_id?
           merge_user!(arguments.options, arguments.pop || user_id)
           perform_get_with_object("/1.1/users/show.json", arguments.options, User)
         else
diff --git a/lib/twitter/search_results.rb b/lib/twitter/search_results.rb
index bb2b007a0..7054f9ce2 100644
--- a/lib/twitter/search_results.rb
+++ b/lib/twitter/search_results.rb
@@ -116,7 +116,7 @@ def query_string_to_hash(query_string)
       return {} if parsed_query.nil?
 
       query = CGI.parse(parsed_query)
-      query.to_h { |key, value| [key.to_sym, value.first] }
+      query.to_h { |key, (value, *)| [key.to_sym, value] }
     end
   end
 end
diff --git a/lib/twitter/streaming/connection.rb b/lib/twitter/streaming/connection.rb
index ea5070c41..a0b876fee 100644
--- a/lib/twitter/streaming/connection.rb
+++ b/lib/twitter/streaming/connection.rb
@@ -49,7 +49,8 @@ def stream(request, response) # rubocop:disable Metrics/MethodLength
         read_pipe, @write_pipe = IO.pipe
         loop do
           read_ios, _write_ios, _exception_ios = IO.select([read_pipe, client])
-          case read_ios.first
+          first_io, = read_ios
+          case first_io
           when client
             response << client.readpartial(1024)
           when read_pipe
diff --git a/test/twitter/rest/direct_messages_test.rb b/test/twitter/rest/direct_messages_test.rb
index 1d24290f2..47f955250 100644
--- a/test/twitter/rest/direct_messages_test.rb
+++ b/test/twitter/rest/direct_messages_test.rb
@@ -250,7 +250,7 @@
 
     it "defaults to returning at most 20 matching sent messages" do
       message_class = Struct.new(:sender_id, :recipient_id)
-      matching = Array.new(25) { message_class.new(22_095_868, 1) }
+      matching = Array.new(25) { |i| message_class.new(22_095_868, i) }
 
       @client.stub(:direct_messages_list, matching) do
         assert_equal(matching.first(20), @client.direct_messages_sent)