diff --git a/.github/workflows/test.yml b/.github/workflows/test.yml
index 361db704..459dc8b9 100644
--- a/.github/workflows/test.yml
+++ b/.github/workflows/test.yml
@@ -14,7 +14,7 @@ jobs:
       LC_ALL: en_US.UTF-8 
 
     strategy:
-      matrix: { ruby: ['3.2', '3.3', '3.4'] }
+      matrix: { ruby: ['3.2', '3.3', '3.4', '4.0'] }
 
     steps:
     - name: Checkout code
diff --git a/bashly.gemspec b/bashly.gemspec
index 6074b865..a45fabc9 100644
--- a/bashly.gemspec
+++ b/bashly.gemspec
@@ -17,16 +17,17 @@ Gem::Specification.new do |s|
 
   s.add_dependency 'colsole', '~> 1.0'
   s.add_dependency 'completely', '~> 0.7.0'
-  s.add_dependency 'filewatcher', '~> 2.0'
   s.add_dependency 'gtx', '~> 0.1.1'
+  s.add_dependency 'listen', '~> 3.9'
   s.add_dependency 'lp', '~> 0.2.0'
-  s.add_dependency 'mister_bin', '~> 0.8.1'
+  s.add_dependency 'mister_bin', '~> 0.9.0'
   s.add_dependency 'requires', '~> 1.1'
   s.add_dependency 'tty-markdown', '~> 0.7.2'
 
-  # Sub-dependenceis (Ruby 3.3.5 warnings)
-  s.add_dependency 'logger', '>= 1', '< 3'    # required by filewatcher
-  s.add_dependency 'ostruct', '>= 0', '< 2'   # required by json
+  # Missing sub-dependencies
+  # logger: required and not bundled by `listen` 3.9.0
+  #         ref: https://github.com/guard/listen/issues/591
+  s.add_dependency 'logger', '~> 1.7'
 
   s.metadata = {
     'bug_tracker_uri'       => 'https://github.com/bashly-framework/bashly/issues',
diff --git a/examples/render-mandoc/docs/download.1 b/examples/render-mandoc/docs/download.1
index 76e19da7..94d4cf11 100644
--- a/examples/render-mandoc/docs/download.1
+++ b/examples/render-mandoc/docs/download.1
@@ -1,6 +1,6 @@
 .\" Automatically generated by Pandoc 3.2
 .\"
-.TH "download" "1" "December 2025" "Version 0.1.0" "Sample application"
+.TH "download" "1" "January 2026" "Version 0.1.0" "Sample application"
 .SH NAME
 \f[B]download\f[R] \- Sample application
 .SH SYNOPSIS
diff --git a/examples/render-mandoc/docs/download.md b/examples/render-mandoc/docs/download.md
index 552fac15..77792c34 100644
--- a/examples/render-mandoc/docs/download.md
+++ b/examples/render-mandoc/docs/download.md
@@ -1,6 +1,6 @@
 % download(1) Version 0.1.0 | Sample application
 % Lana Lang
-% December 2025
+% January 2026
 
 NAME
 ==================================================
diff --git a/lib/bashly.rb b/lib/bashly.rb
index a934b5c1..e82d8593 100644
--- a/lib/bashly.rb
+++ b/lib/bashly.rb
@@ -12,7 +12,7 @@ module Bashly
 
   autoloads 'bashly', %i[
     CLI Config ConfigValidator Library LibrarySource LibrarySourceConfig
-    MessageStrings RenderContext RenderSource Settings VERSION
+    MessageStrings RenderContext RenderSource Settings VERSION Watch
   ]
 
   autoloads 'bashly/concerns', %i[
diff --git a/lib/bashly/commands/generate.rb b/lib/bashly/commands/generate.rb
index 0cdb673f..daf259c8 100644
--- a/lib/bashly/commands/generate.rb
+++ b/lib/bashly/commands/generate.rb
@@ -1,5 +1,3 @@
-require 'filewatcher'
-
 module Bashly
   module Commands
     class Generate < Base
@@ -41,7 +39,7 @@ def run
       def watch
         quiet_say "g`watching` #{Settings.source_dir}\n"
 
-        Filewatcher.new([Settings.source_dir]).watch do
+        Watch.new(Settings.source_dir).on_change do
           reset
           generate
         rescue Bashly::ConfigurationError => e
diff --git a/lib/bashly/commands/render.rb b/lib/bashly/commands/render.rb
index 0e5aafb8..83c1c3bb 100644
--- a/lib/bashly/commands/render.rb
+++ b/lib/bashly/commands/render.rb
@@ -1,4 +1,3 @@
-require 'filewatcher'
 require 'tty-markdown'
 
 module Bashly
@@ -75,7 +74,7 @@ def render
       def watch
         say "g`watching`\n"
 
-        Filewatcher.new(watchables).watch do
+        Watch.new(*watchables).on_change do
           render
           say "g`waiting`\n"
         end
diff --git a/lib/bashly/watch.rb b/lib/bashly/watch.rb
new file mode 100644
index 00000000..f4b53e0c
--- /dev/null
+++ b/lib/bashly/watch.rb
@@ -0,0 +1,52 @@
+require 'listen'
+
+module Bashly
+  # File system watcher - an ergonomic wrapper around the Listen gem
+  class Watch
+    attr_reader :dirs, :options
+
+    DEFAULT_OPTIONS = {
+      force_polling: true,
+      latency:       1.0,
+    }.freeze
+
+    def initialize(*dirs, **options)
+      @options = DEFAULT_OPTIONS.merge(options).freeze
+      @dirs = dirs.empty? ? ['.'] : dirs
+    end
+
+    def on_change(&)
+      start(&)
+      wait
+    ensure
+      stop
+    end
+
+  private
+
+    def build_listener
+      listen.to(*dirs, **options) do |modified, added, removed|
+        yield changes(modified, added, removed)
+      end
+    end
+
+    def start(&block)
+      raise ArgumentError, 'block required' unless block
+
+      @listener = build_listener(&block)
+      @listener.start
+    end
+
+    def stop
+      @listener&.stop
+      @listener = nil
+    end
+
+    def changes(modified, added, removed)
+      { modified:, added:, removed: }
+    end
+
+    def listen = Listen
+    def wait = sleep
+  end
+end
diff --git a/spec/approvals/examples/dependencies-alt b/spec/approvals/examples/dependencies-alt
index 25b7ef40..60f5ebb2 100644
--- a/spec/approvals/examples/dependencies-alt
+++ b/spec/approvals/examples/dependencies-alt
@@ -24,4 +24,4 @@ args: none
 deps:
 - ${deps[git]} = /usr/bin/git
 - ${deps[http_client]} = /usr/bin/curl
-- ${deps[ruby]} = /home/vagrant/.rbenv/versions/3.4.1/bin/ruby
+- ${deps[ruby]} = /home/vagrant/.rbenv/versions/4.0.0/bin/ruby
diff --git a/spec/bashly/commands/generate_spec.rb b/spec/bashly/commands/generate_spec.rb
index d1ba9c5b..811808b6 100644
--- a/spec/bashly/commands/generate_spec.rb
+++ b/spec/bashly/commands/generate_spec.rb
@@ -229,11 +229,11 @@
 
     let(:bashly_config_path) { "#{source_dir}/bashly.yml" }
     let(:bashly_config) { YAML.load_file bashly_config_path }
-    let(:watcher_double) { instance_double Filewatcher, watch: nil }
+    let(:watch_double) { instance_double Watch, on_change: nil }
 
     it 'generates immediately and on change' do
-      allow(Filewatcher).to receive(:new).and_return(watcher_double)
-      allow(watcher_double).to receive(:watch).and_yield
+      allow(Watch).to receive(:new).and_return(watch_double)
+      allow(watch_double).to receive(:on_change).and_yield
 
       expect { subject.execute %w[generate --watch] }
         .to output_approval('cli/generate/watch')
@@ -241,8 +241,8 @@
 
     context 'when ConfigurationError is raised during watch' do
       it 'shows the error gracefully and continues to watch' do
-        allow(Filewatcher).to receive(:new).and_return(watcher_double)
-        allow(watcher_double).to receive(:watch) do |&block|
+        allow(Watch).to receive(:new).and_return(watch_double)
+        allow(watch_double).to receive(:on_change) do |&block|
           bashly_config['invalid_option'] = 'error this'
           File.write bashly_config_path, bashly_config.to_yaml
           block.call
diff --git a/spec/bashly/commands/render_spec.rb b/spec/bashly/commands/render_spec.rb
index 77d34b1d..8e736654 100644
--- a/spec/bashly/commands/render_spec.rb
+++ b/spec/bashly/commands/render_spec.rb
@@ -68,11 +68,11 @@
   describe 'SOURCE TARGET --watch' do
     let(:bashly_config_path) { "#{source_dir}/bashly.yml" }
     let(:bashly_config) { YAML.load_file bashly_config_path }
-    let(:watcher_double) { instance_double Filewatcher, watch: nil }
+    let(:watch_double) { instance_double Watch, on_change: nil }
 
     it 'generates immediately and on change' do
-      allow(Filewatcher).to receive(:new).and_return(watcher_double)
-      allow(watcher_double).to receive(:watch).and_yield
+      allow(Watch).to receive(:new).and_return(watch_double)
+      allow(watch_double).to receive(:on_change).and_yield
 
       expect(subject).to receive(:render).twice
 
diff --git a/spec/bashly/commands/shell_spec.rb b/spec/bashly/commands/shell_spec.rb
index bbf16335..feee4a93 100644
--- a/spec/bashly/commands/shell_spec.rb
+++ b/spec/bashly/commands/shell_spec.rb
@@ -20,7 +20,7 @@
   describe 'in-terminal commands' do
     before do
       ENV['BASHLY_SHELL'] = nil
-      allow(Readline).to receive(:readline).and_return(*input)
+      allow(Reline).to receive(:readline).and_return(*input)
     end
 
     context 'with exit command' do
diff --git a/spec/bashly/concerns/completions_command_spec.rb b/spec/bashly/concerns/completions_command_spec.rb
index c5553faf..4b3cefa3 100644
--- a/spec/bashly/concerns/completions_command_spec.rb
+++ b/spec/bashly/concerns/completions_command_spec.rb
@@ -1,8 +1,7 @@
 describe Script::Command do
-  fixtures = load_fixture 'script/commands'
-
   subject { described_class.new fixtures[fixture] }
 
+  let(:fixtures) { load_fixture('script/commands') }
   let(:fixture) { :completions_simple }
 
   describe '#completion_data' do
diff --git a/spec/bashly/concerns/completions_flag_spec.rb b/spec/bashly/concerns/completions_flag_spec.rb
index 7a19f153..dcb71b9d 100644
--- a/spec/bashly/concerns/completions_flag_spec.rb
+++ b/spec/bashly/concerns/completions_flag_spec.rb
@@ -1,8 +1,7 @@
 describe Script::Flag do
-  fixtures = load_fixture 'script/flags'
-
   subject { described_class.new fixtures[fixture] }
 
+  let(:fixtures) { load_fixture 'script/flags' }
   let(:fixture) { :basic_flag }
   let(:command) { 'some command' }
 
diff --git a/spec/bashly/config_validator_spec.rb b/spec/bashly/config_validator_spec.rb
index 9d091fea..b4f77fd7 100644
--- a/spec/bashly/config_validator_spec.rb
+++ b/spec/bashly/config_validator_spec.rb
@@ -1,13 +1,14 @@
 describe ConfigValidator do
-  fixtures = load_fixture 'script/validations'
+  fixtures = load_fixture('script/validations')
 
   describe '#validate' do
     fixtures.each do |fixture, options|
-      validator = described_class.new options
-
       context "with :#{fixture}" do
+        let(:validator) { described_class.new(options) }
+
         it 'raises an error' do
-          expect { validator.validate }.to raise_approval("validations/#{fixture}")
+          expect { validator.validate }
+            .to raise_approval("validations/#{fixture}")
         end
       end
     end
diff --git a/spec/bashly/integration/examples_spec.rb b/spec/bashly/integration/examples_spec.rb
index 6285fc1a..c3a851bf 100644
--- a/spec/bashly/integration/examples_spec.rb
+++ b/spec/bashly/integration/examples_spec.rb
@@ -5,41 +5,44 @@
 #
 # To only test examples containing a certain string in their path, run:
 # EXAMPLE=yaml bundle exec run spec examples
-
 describe 'generated bash scripts', :slow do
   # Make sure all examples are generated with strict mode
   before { ENV['BASHLY_STRICT'] = 'yes' }
   after { ENV['BASHLY_STRICT'] = nil }
 
   # Test public examples from the examples folder...
-  examples = Dir['examples/*'].select { |f| File.directory? f }
+  examples = Dir['examples/*'].select { |f| File.directory?(f) }
 
   # ...as well as internal examples, not suitable for public view
   fixtures = Dir['spec/fixtures/workspaces/*'].select do |f|
-    File.directory? f and File.exist? "#{f}/test.sh"
+    File.directory?(f) && File.exist?("#{f}/test.sh")
   end
 
   test_cases = fixtures + examples
 
   # Allow up to a certain string distance from the approval text in CI
-  leeway = ENV['CI'] ? 40 : 0
+  let(:leeway) { ENV['CI'] ? 40 : 0 }
 
   # For certain examples, allow some exceptions (replacements) since they
   # are too volatile (e.g. line number changes)
-  exceptions = {
-    'examples/stacktrace'    => [/download:\d+/, 'download:<line>'],
-    'examples/render-mandoc' => [/Version 0.1.0.*download\(1\)/, '<footer>'],
-  }
+  let(:exceptions) do
+    {
+      'examples/stacktrace'    => [/download:\d+/, 'download:<line>'],
+      'examples/render-mandoc' => [/Version 0.1.0.*download\(1\)/, '<footer>'],
+    }
+  end
 
   test_cases.each do |example|
-    approval_name = example.gsub 'spec/fixtures/workspaces', 'fixtures'
-
     next if ENV['EXAMPLE'] && !example.include?(ENV['EXAMPLE'])
 
     describe example do
+      let(:approval_name) do
+        example.gsub('spec/fixtures/workspaces', 'fixtures')
+      end
+
       it 'is executed properly' do
         output = 'not executed'
-        Dir.chdir example do
+        Dir.chdir(example) do
           output = `bash test.sh 2>&1`
         end
 
diff --git a/spec/bashly/integration/rendering_mandoc_spec.rb b/spec/bashly/integration/rendering_mandoc_spec.rb
index 6e9678e1..2a4a0e0f 100644
--- a/spec/bashly/integration/rendering_mandoc_spec.rb
+++ b/spec/bashly/integration/rendering_mandoc_spec.rb
@@ -4,8 +4,9 @@
   subject { Commands::Render.new }
 
   let(:source_dir) { Settings.source_dir }
+  let(:leeway) { ENV['CI'] ? 20 : 0 }
+  let(:target) { 'spec/tmp' }
 
-  target = 'spec/tmp'
   examples = %w[
     catch-all-advanced
     dependencies-alt
@@ -15,9 +16,6 @@
     render-mandoc
   ]
 
-  # Allow up to a certain string distance from the approval text in CI
-  leeway = ENV['CI'] ? 20 : 0
-
   examples.each do |example|
     describe example do
       before do
diff --git a/spec/bashly/integration/rendering_markdown_spec.rb b/spec/bashly/integration/rendering_markdown_spec.rb
index 8593b232..a73ef862 100644
--- a/spec/bashly/integration/rendering_markdown_spec.rb
+++ b/spec/bashly/integration/rendering_markdown_spec.rb
@@ -4,8 +4,9 @@
   subject { Commands::Render.new }
 
   let(:source_dir) { Settings.source_dir }
+  let(:target) { 'spec/tmp' }
+  let(:leeway) { ENV['CI'] ? 20 : 0 }
 
-  target = 'spec/tmp'
   examples = %w[
     catch-all-advanced
     dependencies-alt
@@ -15,9 +16,6 @@
     render-markdown
   ]
 
-  # Allow up to a certain string distance from the approval text in CI
-  leeway = ENV['CI'] ? 20 : 0
-
   examples.each do |example|
     describe example do
       before do
@@ -31,8 +29,10 @@
 
         Dir["#{target}/*.md"].each do |file|
           puts "    => #{file}"
-          basename = File.basename file
-          expect(File.read file).to match_approval("rendering/markdown/#{example}/#{basename}")
+          basename = File.basename(file)
+
+          expect(File.read(file))
+            .to match_approval("rendering/markdown/#{example}/#{basename}")
             .diff(leeway)
         end
       end
diff --git a/spec/bashly/library_source_config_spec.rb b/spec/bashly/library_source_config_spec.rb
index da03f8f5..0ce9fb51 100644
--- a/spec/bashly/library_source_config_spec.rb
+++ b/spec/bashly/library_source_config_spec.rb
@@ -13,12 +13,13 @@
 
   describe '#validate' do
     fixtures.each do |path|
-      fixture_name = File.basename path, '.yml'
-      config = described_class.new path
+      context "with #{File.basename(path)}" do
+        let(:fixture_name) { File.basename(path, '.yml') }
+        let(:config)       { described_class.new(path) }
 
-      context "with #{fixture_name}.yml" do
         it 'raises an error' do
-          expect { config.validate }.to raise_approval("libraries_validation/#{fixture_name}")
+          expect { config.validate }
+            .to raise_approval("libraries_validation/#{fixture_name}")
         end
       end
     end
diff --git a/spec/bashly/settings_spec.rb b/spec/bashly/settings_spec.rb
index e669b072..fc8d74e9 100644
--- a/spec/bashly/settings_spec.rb
+++ b/spec/bashly/settings_spec.rb
@@ -50,7 +50,7 @@
     end
 
     context 'when its corresponding env var is set' do
-      original_value = ENV['BASHLY_TAB_INDENT']
+      let(:original_value) { ENV['BASHLY_TAB_INDENT'] }
 
       before { described_class.tab_indent = nil }
       after { ENV['BASHLY_TAB_INDENT'] = original_value }
diff --git a/spec/bashly/watch_spec.rb b/spec/bashly/watch_spec.rb
new file mode 100644
index 00000000..830eea15
--- /dev/null
+++ b/spec/bashly/watch_spec.rb
@@ -0,0 +1,64 @@
+describe Watch do
+  subject { described_class.new(*dirs, **options) }
+
+  let(:dirs)     { [] }
+  let(:options)  { {} }
+  let(:listener) { double(start: nil, stop: nil) }
+  let(:listen)   { class_double(Listen) }
+  let(:changes)  { [['modified file'], ['added file'], ['removed file']] }
+
+  before do
+    allow(subject).to receive(:listen).and_return(listen)
+    allow(listen).to receive(:to).and_yield(*changes).and_return(listener)
+    allow(subject).to receive(:sleep) # prevent blocking
+  end
+
+  describe '#on_change' do
+    it 'starts and stops the listener' do
+      expect(listener).to receive(:start)
+      expect(listener).to receive(:stop)
+
+      subject.on_change { |_| nil }
+    end
+
+    it 'passes normalized changes to the block' do
+      received_changes = nil
+
+      subject.on_change { |payload| received_changes = payload }
+
+      expect(received_changes).to eq({
+        modified: ['modified file'],
+        added:    ['added file'],
+        removed:  ['removed file'],
+      })
+    end
+
+    it 'stops the listener if waiting raises' do
+      allow(subject).to receive(:sleep).and_raise('boom')
+
+      expect(listener).to receive(:stop)
+      expect { subject.on_change { |_| nil } }.to raise_error('boom')
+    end
+
+    context 'with custom dirs and options' do
+      let(:dirs)    { %w[lib spec] }
+      let(:options) { { latency: 0.25 } }
+
+      it 'passes them through to Listen' do
+        expect(listen).to receive(:to).with(
+          'lib',
+          'spec',
+          **described_class::DEFAULT_OPTIONS, **options
+        )
+
+        subject.on_change { |_| nil }
+      end
+    end
+
+    context 'when no block is provided' do
+      it 'raises ArgumentError' do
+        expect { subject.on_change }.to raise_error(ArgumentError, 'block required')
+      end
+    end
+  end
+end