diff --git a/ruby/.rubocop.yml b/ruby/.rubocop.yml
deleted file mode 100644
index c58f192..0000000
--- a/ruby/.rubocop.yml
+++ /dev/null
@@ -1,26 +0,0 @@
-AllCops:
-  NewCops: enable
-
-Layout/EmptyLineAfterGuardClause:
-  Enabled: false
-
-Layout/FirstHashElementIndentation:
-  EnforcedStyle: consistent
-
-Metrics/AbcSize:
-  Max: 25
-
-Metrics/MethodLength:
-  Max: 30
-
-Style/Documentation:
-  Enabled: false
-
-Style/FrozenStringLiteralComment:
-  Enabled: false
-
-Style/HashSyntax:
-  EnforcedShorthandSyntax: never
-
-Style/TrailingCommaInHashLiteral:
-  EnforcedStyleForMultiline: consistent_comma
diff --git a/ruby/.ruby-version b/ruby/.ruby-version
index be94e6f..fcdb2e1 100644
--- a/ruby/.ruby-version
+++ b/ruby/.ruby-version
@@ -1 +1 @@
-3.2.2
+4.0.0
diff --git a/ruby/.standard.yml b/ruby/.standard.yml
new file mode 100644
index 0000000..e084b5e
--- /dev/null
+++ b/ruby/.standard.yml
@@ -0,0 +1,4 @@
+fix: true
+parallel: true
+ignore:
+  - "test_bin/**/*"
diff --git a/ruby/Gemfile b/ruby/Gemfile
index bff8709..b1cdd0f 100644
--- a/ruby/Gemfile
+++ b/ruby/Gemfile
@@ -1,6 +1,8 @@
 source "https://rubygems.org"
 
-gem 'minitest', '~> 5.20'
-gem 'rake', '~> 13.0'
-gem 'rubocop', '1.56.4'
-gem 'wordexp', '~> 0.2'
+gem "minitest", "~> 6.0"
+gem "parser", "~> 3.3.10"
+gem "rake", "~> 13.0"
+gem "reline", "~> 0.6"
+gem "standard", "~> 1.52.0", require: false
+gem "wordexp", "~> 0.2"
diff --git a/ruby/Gemfile.lock b/ruby/Gemfile.lock
index 6a134fb..6c67645 100644
--- a/ruby/Gemfile.lock
+++ b/ruby/Gemfile.lock
@@ -1,47 +1,72 @@
 GEM
   remote: https://rubygems.org/
   specs:
-    ast (2.4.2)
-    base64 (0.1.1)
-    json (2.6.3)
-    language_server-protocol (3.17.0.3)
-    minitest (5.20.0)
-    parallel (1.23.0)
-    parser (3.2.2.4)
+    ast (2.4.3)
+    io-console (0.8.2)
+    json (2.18.0)
+    language_server-protocol (3.17.0.5)
+    lint_roller (1.1.0)
+    minitest (6.0.1)
+      prism (~> 1.5)
+    parallel (1.27.0)
+    parser (3.3.10.0)
       ast (~> 2.4.1)
       racc
-    racc (1.7.1)
+    prism (1.7.0)
+    racc (1.8.1)
     rainbow (3.1.1)
-    rake (13.0.6)
-    regexp_parser (2.8.1)
-    rexml (3.2.6)
-    rubocop (1.56.4)
-      base64 (~> 0.1.1)
+    rake (13.3.1)
+    regexp_parser (2.11.3)
+    reline (0.6.3)
+      io-console (~> 0.5)
+    rubocop (1.81.7)
       json (~> 2.3)
-      language_server-protocol (>= 3.17.0)
+      language_server-protocol (~> 3.17.0.2)
+      lint_roller (~> 1.1.0)
       parallel (~> 1.10)
-      parser (>= 3.2.2.3)
+      parser (>= 3.3.0.2)
       rainbow (>= 2.2.2, < 4.0)
-      regexp_parser (>= 1.8, < 3.0)
-      rexml (>= 3.2.5, < 4.0)
-      rubocop-ast (>= 1.28.1, < 2.0)
+      regexp_parser (>= 2.9.3, < 3.0)
+      rubocop-ast (>= 1.47.1, < 2.0)
       ruby-progressbar (~> 1.7)
-      unicode-display_width (>= 2.4.0, < 3.0)
-    rubocop-ast (1.29.0)
-      parser (>= 3.2.1.0)
+      unicode-display_width (>= 2.4.0, < 4.0)
+    rubocop-ast (1.49.0)
+      parser (>= 3.3.7.2)
+      prism (~> 1.7)
+    rubocop-performance (1.26.1)
+      lint_roller (~> 1.1)
+      rubocop (>= 1.75.0, < 2.0)
+      rubocop-ast (>= 1.47.1, < 2.0)
     ruby-progressbar (1.13.0)
-    unicode-display_width (2.5.0)
+    standard (1.52.0)
+      language_server-protocol (~> 3.17.0.2)
+      lint_roller (~> 1.0)
+      rubocop (~> 1.81.7)
+      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)
+    unicode-display_width (3.2.0)
+      unicode-emoji (~> 4.1)
+    unicode-emoji (4.2.0)
     wordexp (0.2.2)
 
 PLATFORMS
   arm64-darwin-21
   arm64-darwin-22
   arm64-darwin-23
+  arm64-darwin-25
 
 DEPENDENCIES
-  minitest (~> 5.20)
+  minitest (~> 6.0)
+  parser (~> 3.3.10)
   rake (~> 13.0)
-  rubocop (= 1.56.4)
+  reline (~> 0.6)
+  standard (~> 1.52.0)
   wordexp (~> 0.2)
 
 BUNDLED WITH
diff --git a/ruby/Rakefile b/ruby/Rakefile
index f16f3fa..a047cc4 100644
--- a/ruby/Rakefile
+++ b/ruby/Rakefile
@@ -1,11 +1,12 @@
-require 'rake/testtask'
+require "rake/testtask"
+require "standard/rake"
 
-task default: 'test'
+task default: %i[test standard]
 
 Rake::TestTask.new do |task|
-  task.pattern = 'test/*_test.rb'
+  task.pattern = "test/*_test.rb"
 end
 
 task :clean do
-  FileUtils.rm_rf('test_bin')
+  FileUtils.rm_rf("test_bin")
 end
diff --git a/ruby/a1 b/ruby/a1
index a87b29b..101dc04 100755
--- a/ruby/a1
+++ b/ruby/a1
@@ -1,6 +1,6 @@
 #!/usr/bin/env ruby -w
 
-require 'English'
-require_relative 'shell'
+require "English"
+require_relative "shell"
 
 Shell::CLI.new.run(args: ARGV) if $PROGRAM_NAME == __FILE__
diff --git a/ruby/shell.rb b/ruby/shell.rb
index c113b43..bbf5f68 100644
--- a/ruby/shell.rb
+++ b/ruby/shell.rb
@@ -1,7 +1,7 @@
 $LOAD_PATH << File.expand_path(__dir__)
 
-require 'shell/cli'
-require 'shell/repl'
+require "shell/cli"
+require "shell/repl"
 
 module Shell
 end
diff --git a/ruby/shell/builtins.rb b/ruby/shell/builtins.rb
index 6c7749f..4a39cd9 100644
--- a/ruby/shell/builtins.rb
+++ b/ruby/shell/builtins.rb
@@ -1,5 +1,5 @@
-require 'shell/job_control'
-require 'shell/logger'
+require "shell/job_control"
+require "shell/logger"
 
 module Shell
   class Builtins
@@ -34,14 +34,14 @@ module Shell
       jobs.each do |job|
         puts job_control.format_job(job)
       end
-      plural = jobs.count == 1 ? '' : 's'
+      plural = (jobs.count == 1) ? "" : "s"
       puts "#{jobs.count} background job#{plural}"
       0
     end
 
     def builtin_bgkill(args)
       if args.count != 1
-        logger.warn 'Usage: bgkill <job>'
+        logger.warn "Usage: bgkill <job>"
         return -1
       end
 
@@ -57,11 +57,11 @@ module Shell
 
     def builtin_export(args)
       # only supports one variable and doesn't support quoting
-      name, *value_parts = args.first.strip.split('=')
+      name, *value_parts = args.first.strip.split("=")
       if name.nil? || name.empty?
-        logger.warn "#{red('[ERROR]')} Invalid export command"
+        logger.warn "#{red("[ERROR]")} Invalid export command"
       else
-        ENV[name] = value_parts.join('=').gsub(/\$\w+/) { |m| ENV[m[1..]] || '' }
+        ENV[name] = value_parts.join("=").gsub(/\$\w+/) { |m| ENV[m[1..]] || "" }
       end
       0
     end
diff --git a/ruby/shell/cli.rb b/ruby/shell/cli.rb
index ac549d0..dde9cf5 100644
--- a/ruby/shell/cli.rb
+++ b/ruby/shell/cli.rb
@@ -1,6 +1,6 @@
-require 'shell/colours'
-require 'shell/logger'
-require 'shell/repl'
+require "shell/colours"
+require "shell/logger"
+require "shell/repl"
 
 module Shell
   class CLI
@@ -29,20 +29,20 @@ module Shell
 
     def parse_options(args)
       options = {
-        verbose: false,
+        verbose: false
       }
       while (arg = args.shift)
         case arg
-        when '-c'
+        when "-c"
           options[:command] = args.shift
           if options[:command].nil?
-            warn 'ERROR: expected string after -c'
+            warn "ERROR: expected string after -c"
             exit 1
           end
-        when '-v', '--verbose'
+        when "-v", "--verbose"
           options[:verbose] = true
         else
-          logger.warn "#{red('[ERROR]')} Unknown argument: #{arg}"
+          logger.warn "#{red("[ERROR]")} Unknown argument: #{arg}"
           exit 1
         end
       end
diff --git a/ruby/shell/job_control.rb b/ruby/shell/job_control.rb
index 5c95cb1..f116895 100644
--- a/ruby/shell/job_control.rb
+++ b/ruby/shell/job_control.rb
@@ -1,8 +1,8 @@
-require 'English'
+require "English"
 
-require 'shell/colours'
-require 'shell/job'
-require 'shell/logger'
+require "shell/colours"
+require "shell/job"
+require "shell/logger"
 
 module Shell
   class JobControl
@@ -17,7 +17,7 @@ module Shell
 
     def exec_command(cmd, args, background: false)
       unless (path = resolve_executable(cmd))
-        warn "#{red('[ERROR]')} command not found: #{cmd}"
+        warn "#{red("[ERROR]")} command not found: #{cmd}"
         return -2
       end
 
@@ -25,7 +25,7 @@ module Shell
       if background
         job = Job.new(next_job_id, pid, cmd, args)
         @jobs_by_pid[pid] = job
-        puts white('Running job ') + yellow(job.id) + white(" (pid #{pid}) in background")
+        puts white("Running job ") + yellow(job.id) + white(" (pid #{pid}) in background")
         Process.waitpid(pid, Process::WNOHANG)
         0
       else
@@ -38,8 +38,8 @@ module Shell
           0
         end
       end
-    rescue StandardError => e
-      warn "#{red('[ERROR]')} #{e.message} #{e.inspect}"
+    rescue => e
+      warn "#{red("[ERROR]")} #{e.message} #{e.inspect}"
       -5
     end
 
@@ -50,7 +50,7 @@ module Shell
         return
       end
 
-      Process.kill('TERM', job.pid)
+      Process.kill("TERM", job.pid)
     rescue Errno::ESRCH
       logger.warn "No such proccess: #{job.pid}"
     end
@@ -60,24 +60,24 @@ module Shell
     end
 
     def format_job(job)
-      args = job.args.join(' ')
-      "#{yellow(job.id)}: #{white('(pid ', job.pid, ')')} #{green(job.cmd)} #{args}"
+      args = job.args.join(" ")
+      "#{yellow(job.id)}: #{white("(pid ", job.pid, ")")} #{green(job.cmd)} #{args}"
     end
 
     def trap_sigchld
       # handler for SIGCHLD when a child's state changes
-      Signal.trap('CHLD') do |_signo|
+      Signal.trap("CHLD") do |_signo|
         pid = Process.waitpid(-1, Process::WNOHANG)
         if pid.nil?
           # no-op
         elsif (job = @jobs_by_pid[pid])
           @jobs_by_pid.delete(pid)
-          time = Time.now.strftime('%T')
-          job_text = yellow('job ', job.id, ' exited')
-          args = job.args.join(' ')
-          puts "\n[#{time}] #{job_text} #{white('(pid ', job.pid, ')')}: #{green(job.cmd)} #{args}"
+          time = Time.now.strftime("%T")
+          job_text = yellow("job ", job.id, " exited")
+          args = job.args.join(" ")
+          puts "\n[#{time}] #{job_text} #{white("(pid ", job.pid, ")")}: #{green(job.cmd)} #{args}"
         else
-          warn "\n#{yellow('[WARN]')} No job found for child with PID #{pid}"
+          warn "\n#{yellow("[WARN]")} No job found for child with PID #{pid}"
         end
         Readline.refresh_line
       end
@@ -88,11 +88,11 @@ module Shell
     # Returns nil when no such command was found.
     def resolve_executable(path_or_filename)
       # process absolute and relative paths directly
-      return path_or_filename if path_or_filename['/'] && \
-                                 File.executable?(path_or_filename)
+      return path_or_filename if path_or_filename["/"] &&
+        File.executable?(path_or_filename)
 
       filename = path_or_filename
-      ENV['PATH'].split(':').each do |dir|
+      ENV["PATH"].split(":").each do |dir|
         path = File.join(dir, filename)
         next unless File.exist?(path)
         return path if File.executable?(path)
diff --git a/ruby/shell/logger.rb b/ruby/shell/logger.rb
index a5b4954..5b38504 100644
--- a/ruby/shell/logger.rb
+++ b/ruby/shell/logger.rb
@@ -1,4 +1,4 @@
-require 'shell/colours'
+require "shell/colours"
 
 module Shell
   # Queues up messages to be printed out when readline is waiting for input, to prevent
@@ -19,16 +19,16 @@ module Shell
     end
 
     def log(message)
-      @logs << Log.new(:info, "#{white('[INFO]')} #{message}")
+      @logs << Log.new(:info, "#{white("[INFO]")} #{message}")
     end
-    alias info log
+    alias_method :info, :log
 
     def warn(message)
-      @logs << Log.new(:warning, "#{yellow('[WARN]')} #{message}")
+      @logs << Log.new(:warning, "#{yellow("[WARN]")} #{message}")
     end
 
     def error(message)
-      @logs << Log.new(:error, "#{red('[ERROR]')} #{message}")
+      @logs << Log.new(:error, "#{red("[ERROR]")} #{message}")
     end
 
     def verbose(message)
diff --git a/ruby/shell/repl.rb b/ruby/shell/repl.rb
index 1a46776..1136ec3 100644
--- a/ruby/shell/repl.rb
+++ b/ruby/shell/repl.rb
@@ -1,10 +1,14 @@
-require 'readline'
-require 'wordexp'
+begin
+  require "readline"
+rescue LoadError
+  require "reline"
+end
+require "wordexp"
 
-require 'shell/builtins'
-require 'shell/colours'
-require 'shell/job_control'
-require 'shell/logger'
+require "shell/builtins"
+require "shell/colours"
+require "shell/job_control"
+require "shell/logger"
 
 module Shell
   class REPL
@@ -55,13 +59,13 @@ module Shell
         job_control.exec_command(cmd, args)
       end
     rescue Errno => e
-      warn "#{red('[ERROR]')} #{e.message}"
+      warn "#{red("[ERROR]")} #{e.message}"
       -1
     end
 
     # Looks like this: /path/to/somewhere%
     def prompt(pwd)
-      "#{blue(pwd)}#{white('%')} #{CLEAR}"
+      "#{blue(pwd)}#{white("%")} #{CLEAR}"
     end
   end
 end
diff --git a/ruby/test/shell_test.rb b/ruby/test/shell_test.rb
index bbd31ea..1663bde 100644
--- a/ruby/test/shell_test.rb
+++ b/ruby/test/shell_test.rb
@@ -1,16 +1,16 @@
-require 'minitest/autorun'
+require "minitest/autorun"
 
 class ShellTest < Minitest::Test
   TRIVIAL_SHELL_SCRIPT = "#!/bin/sh\ntrue".freeze
 
-  A1_PATH = ENV.fetch('A1_PATH', './a1').freeze
+  A1_PATH = ENV.fetch("A1_PATH", "./a1").freeze
 
   def setup
-    FileUtils.mkdir_p('test_bin')
+    FileUtils.mkdir_p("test_bin")
   end
 
   def teardown
-    FileUtils.rm_rf('test_bin')
+    FileUtils.rm_rf("test_bin")
   end
 
   def unique_shell_script(code)
@@ -31,42 +31,42 @@ class ShellTest < Minitest::Test
   #################################
 
   def test_background_job
-    output = `#{A1_PATH} -c 'bg echo hello'`.gsub(/\e\[([;\d]+)?m/, '')
+    output = `#{A1_PATH} -c 'bg echo hello'`.gsub(/\e\[([;\d]+)?m/, "")
     pid = /\(pid (\d+)\)/.match(output)[1]
     assert_equal "Running job 1 (pid #{pid}) in background\nhello\n", output
   end
 
   def test_resolves_executables_with_absolute_paths
-    assert_equal '/usr/bin/which', `#{A1_PATH} -c '/usr/bin/which -a which'`.chomp
+    assert_equal "/usr/bin/which", `#{A1_PATH} -c '/usr/bin/which -a which'`.chomp
   end
 
   def test_resolves_executables_with_relative_paths
-    File.write('test_bin/something', TRIVIAL_SHELL_SCRIPT)
-    File.chmod(0o755, 'test_bin/something')
+    File.write("test_bin/something", TRIVIAL_SHELL_SCRIPT)
+    File.chmod(0o755, "test_bin/something")
     assert system("#{A1_PATH} -c ./test_bin/something")
   end
 
   def test_resolves_executables_in_absolute_paths
-    assert_equal '/usr/bin/which', `#{A1_PATH} -c 'which -a which'`.chomp
+    assert_equal "/usr/bin/which", `#{A1_PATH} -c 'which -a which'`.chomp
   end
 
   def test_resolves_executables_in_relative_paths
     code = rand(1_000_000).to_s
-    File.write('test_bin/definitely_executable', unique_shell_script(code))
-    File.chmod(0o755, 'test_bin/definitely_executable')
+    File.write("test_bin/definitely_executable", unique_shell_script(code))
+    File.chmod(0o755, "test_bin/definitely_executable")
     actual = `PATH="./test_bin:$PATH" #{A1_PATH} -c definitely_executable`.chomp
     assert_equal code, actual
   end
 
   def test_does_not_resolve_non_executable_files_in_path
-    File.write('test_bin/definitely_not_executable', TRIVIAL_SHELL_SCRIPT)
-    File.chmod(0o644, 'test_bin/definitely_not_executable')
+    File.write("test_bin/definitely_not_executable", TRIVIAL_SHELL_SCRIPT)
+    File.chmod(0o644, "test_bin/definitely_not_executable")
     actual = system("PATH=\"./test_bin:$PATH\" #{A1_PATH} -c definitely_not_executable 2>/dev/null")
     assert_equal false, actual
   end
 
   def test_refreshes_readline_after_bg_execution
-    skip 'unimplemented'
+    skip "unimplemented"
   end
 
   #########################
@@ -74,25 +74,25 @@ class ShellTest < Minitest::Test
   #########################
 
   def test_builtin_cd_no_args
-    skip 'cannot easily implement without sequencing with ; or &&'
+    skip "cannot easily implement without sequencing with ; or &&"
   end
 
   def test_builtin_cd
-    skip 'cannot easily implement without sequencing with ; or &&'
+    skip "cannot easily implement without sequencing with ; or &&"
   end
 
   def test_builtin_cd_dash
-    skip 'cannot easily implement without sequencing with ; or &&'
+    skip "cannot easily implement without sequencing with ; or &&"
   end
 
   def test_builtin_cd_parent
-    skip 'cannot easily implement without sequencing with ; or &&'
+    skip "cannot easily implement without sequencing with ; or &&"
   end
 
   def test_builtin_pwd
     assert_equal Dir.pwd, `#{A1_PATH} -c pwd`.chomp
 
     shell_path = File.expand_path(A1_PATH, Dir.pwd)
-    assert_equal '/usr/bin', `cd /usr/bin && '#{shell_path}' -c pwd`.chomp
+    assert_equal "/usr/bin", `cd /usr/bin && '#{shell_path}' -c pwd`.chomp
   end
 end