diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index 8f8bb74aca..c0bb76e3c4 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -1,4 +1,4 @@
-# This file was generated on 2020-11-16T22:10:29+00:00 from the rspec-dev repo.
+# This file was generated on 2020-11-29T14:01:14+03:00 from the rspec-dev repo.
 # DO NOT modify it by hand as your changes will get lost the next time it is generated.
 
 name: RSpec CI
@@ -11,6 +11,8 @@ on:
   pull_request:
     branches:
       - '*'
+env:
+  RSPEC_CI: true
 jobs:
   test:
     name: Ruby ${{ matrix.ruby }}
@@ -24,8 +26,6 @@ jobs:
           - 2.5
           - 2.4
           - 2.3
-          - 2.2
-          - 2.1.9
           - ruby-head
       fail-fast: false
     continue-on-error: ${{ matrix.ruby == 'jruby-9.2.13.0' || endsWith(matrix.ruby, 'head') }}
@@ -40,3 +40,25 @@ jobs:
       - run: script/clone_all_rspec_repos
       - run: bundle install --binstubs --standalone
       - run: script/run_build
+
+  windows:
+    name: Ruby ${{ matrix.ruby }} (Windows)
+    runs-on: windows-latest
+    strategy:
+      matrix:
+        ruby:
+          - 2.7
+          - 2.6
+          - 2.5
+          - 2.4
+          - 2.3
+      fail-fast: false
+    steps:
+      - uses: actions/checkout@v2
+      - uses: ruby/setup-ruby@v1
+        with:
+          bundler: 2
+          ruby-version: ${{ matrix.ruby }}
+          bundler-cache: true
+      - run: cinst ansicon
+      - run: bundle exec rspec --backtrace
diff --git a/.rubocop_rspec_base.yml b/.rubocop_rspec_base.yml
index 00581e870f..3844aa0811 100644
--- a/.rubocop_rspec_base.yml
+++ b/.rubocop_rspec_base.yml
@@ -1,4 +1,4 @@
-# This file was generated on 2020-11-16T22:10:29+00:00 from the rspec-dev repo.
+# This file was generated on 2020-11-29T14:01:14+03:00 from the rspec-dev repo.
 # DO NOT modify it by hand as your changes will get lost the next time it is generated.
 
 # This file contains defaults for RSpec projects. Individual projects
diff --git a/.travis.yml b/.travis.yml
index 953515fb02..40e9215175 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -1,6 +1,3 @@
-# This file was generated on 2020-11-16T22:10:29+00:00 from the rspec-dev repo.
-# DO NOT modify it by hand as your changes will get lost the next time it is generated.
-
 # In order to install old Rubies, we need to use old Ubuntu distibution.
 dist: trusty
 language: ruby
@@ -15,29 +12,14 @@ before_install:
 bundler_args: "--binstubs --standalone --without documentation --path ../bundle"
 script: "script/run_build"
 rvm:
-  - 1.8.7
-  - 1.9.2
-  - 1.9.3
-  - 2.0.0
-  - ree
-  - rbx-3
   - jruby-9.1.7.0 # pin JRuby to this until travis/rvm can install later versions
   - jruby-head
-  - jruby-1.7
 env:
   - JRUBY_OPTS='--dev'
+  - RSPEC_CI='true'
 matrix:
-  include:
-    - rvm: jruby-1.7
-      env: JRUBY_OPTS='--dev --1.8'
-    - rvm: 2.7.1
-      env: DIFF_LCS_VERSION="~> 1.3.0"
-    - rvm: 2.7.1
-      env: DIFF_LCS_VERSION="1.4.3"
   allow_failures:
     - rvm: jruby-head
-    - rvm: ruby-head
-    - rvm: rbx-3
   fast_finish: true
 branches:
   only:
diff --git a/appveyor.yml b/appveyor.yml
deleted file mode 100644
index 79bc79a324..0000000000
--- a/appveyor.yml
+++ /dev/null
@@ -1,42 +0,0 @@
-# This file was generated on 2020-11-16T22:10:29+00:00 from the rspec-dev repo.
-# DO NOT modify it by hand as your changes will get lost the next time it is generated.
-
-version: "{build}"
-
-# This will build all PRs targetting matching branches.
-# Without this, each PR builds twice -- once for the PR branch HEAD,
-# and once for the merge commit that github creates for each mergable PR.
-branches:
-  only:
-    - main
-    - /.*-maintenance$/
-
-# Disable normal Windows builds in favor of our test script.
-build: off
-
-cache:
-  - vendor/bundle
-
-install:
-  - set PATH=C:\Ruby%RUBY_VERSION%\bin;%PATH%
-  - bundle config --local path vendor/bundle
-  - bundle install
-  - cinst ansicon
-
-before_test:
-  - ruby --version
-  - gem --version
-  - bundle --version
-
-test_script:
-  - bundle exec rspec --backtrace
-
-environment:
-  matrix:
-    - ruby_version: 200
-    - ruby_version: 21
-    - ruby_version: 22
-    - ruby_version: 23-x64
-    - ruby_version: 24-x64
-    - ruby_version: 25-x64
-    - ruby_version: 26-x64
diff --git a/lib/rspec/core/version.rb b/lib/rspec/core/version.rb
index 97a58aefe8..538ab02627 100644
--- a/lib/rspec/core/version.rb
+++ b/lib/rspec/core/version.rb
@@ -3,7 +3,7 @@ module Core
     # Version information for RSpec Core.
     module Version
       # Current version of RSpec Core, in semantic versioning format.
-      STRING = '3.11.0.pre'
+      STRING = '4.0.0.pre'
     end
   end
 end
diff --git a/maintenance-branch b/maintenance-branch
index ba2906d066..e6fbea6d90 100644
--- a/maintenance-branch
+++ b/maintenance-branch
@@ -1 +1 @@
-main
+4-0-dev
\ No newline at end of file
diff --git a/script/ci_functions.sh b/script/ci_functions.sh
index 38f4064ae3..8048ff472f 100644
--- a/script/ci_functions.sh
+++ b/script/ci_functions.sh
@@ -1,4 +1,4 @@
-# This file was generated on 2020-11-16T22:10:29+00:00 from the rspec-dev repo.
+# This file was generated on 2020-11-29T14:01:14+03:00 from the rspec-dev repo.
 # DO NOT modify it by hand as your changes will get lost the next time it is generated.
 
 # Taken from:
diff --git a/script/clone_all_rspec_repos b/script/clone_all_rspec_repos
index 9ba9631cd0..654b3ed060 100755
--- a/script/clone_all_rspec_repos
+++ b/script/clone_all_rspec_repos
@@ -1,5 +1,5 @@
 #!/bin/bash
-# This file was generated on 2020-11-16T22:10:29+00:00 from the rspec-dev repo.
+# This file was generated on 2020-11-29T14:01:14+03:00 from the rspec-dev repo.
 # DO NOT modify it by hand as your changes will get lost the next time it is generated.
 
 set -e
@@ -12,11 +12,8 @@ if is_mri; then
   clone_repo "rspec-core"
   clone_repo "rspec-expectations"
   clone_repo "rspec-mocks"
-  clone_repo "rspec-rails"
-
-  if rspec_support_compatible; then
-    clone_repo "rspec-support"
-  fi
+  clone_repo "rspec-rails" "main"
+  clone_repo "rspec-support"
 
   popd
 else
diff --git a/script/functions.sh b/script/functions.sh
index 0716529f39..29fe17ab10 100644
--- a/script/functions.sh
+++ b/script/functions.sh
@@ -1,4 +1,4 @@
-# This file was generated on 2020-11-16T22:10:29+00:00 from the rspec-dev repo.
+# This file was generated on 2020-11-29T14:01:14+03:00 from the rspec-dev repo.
 # DO NOT modify it by hand as your changes will get lost the next time it is generated.
 
 SCRIPT_DIR="$( cd "$( dirname "${BASH_SOURCE[0]}" )" && pwd )"
@@ -12,14 +12,20 @@ SPECS_HAVE_RUN_FILE=specs.out
 MAINTENANCE_BRANCH=`cat maintenance-branch`
 
 # Don't allow rubygems to pollute what's loaded. Also, things boot faster
-# without the extra load time of rubygems. Only works on MRI Ruby 1.9+
-if is_mri_192_plus; then
+# without the extra load time of rubygems. Only works on MRI.
+if is_mri; then
   export RUBYOPT="--disable=gem"
 fi
 
 function clone_repo {
   if [ ! -d $1 ]; then # don't clone if the dir is already there
-    travis_retry eval "git clone https://github.com/rspec/$1 --depth 1 --branch $MAINTENANCE_BRANCH"
+    if [ -z "$2" ]; then
+      BRANCH_TO_CLONE="$MAINTENANCE_BRANCH"
+    else
+      BRANCH_TO_CLONE="$2"
+    fi
+
+    travis_retry eval "git clone https://github.com/rspec/$1 --depth 1 --branch $BRANCH_TO_CLONE"
   fi;
 }
 
@@ -47,12 +53,7 @@ function run_cukes {
 
     echo "${PWD}/bin/cucumber"
 
-    if is_mri_192; then
-      # For some reason we get SystemStackError on 1.9.2 when using
-      # the bin/cucumber approach below. That approach is faster
-      # (as it avoids the bundler tax), so we use it on rubies where we can.
-      bundle exec cucumber --strict
-    elif is_jruby; then
+    if is_jruby; then
       # For some reason JRuby doesn't like our improved bundler setup
       RUBYOPT="-I${PWD}/../bundle -rbundler/setup" \
          PATH="${PWD}/bin:$PATH" \
@@ -187,11 +188,8 @@ function run_all_spec_suites {
   fold "rspec-core specs" run_spec_suite_for "rspec-core"
   fold "rspec-expectations specs" run_spec_suite_for "rspec-expectations"
   fold "rspec-mocks specs" run_spec_suite_for "rspec-mocks"
+  fold "rspec-support specs" run_spec_suite_for "rspec-support"
   if rspec_rails_compatible; then
     fold "rspec-rails specs" run_spec_suite_for "rspec-rails"
   fi
-
-  if rspec_support_compatible; then
-    fold "rspec-support specs" run_spec_suite_for "rspec-support"
-  fi
 }
diff --git a/script/predicate_functions.sh b/script/predicate_functions.sh
index ca2ca30018..eafb8a5d3f 100644
--- a/script/predicate_functions.sh
+++ b/script/predicate_functions.sh
@@ -1,10 +1,9 @@
-# This file was generated on 2020-11-16T22:10:29+00:00 from the rspec-dev repo.
+# This file was generated on 2020-11-29T14:01:14+03:00 from the rspec-dev repo.
 # DO NOT modify it by hand as your changes will get lost the next time it is generated.
 
 function is_mri {
-  if ruby -e "exit(!defined?(RUBY_ENGINE) || RUBY_ENGINE == 'ruby')"; then
-    # RUBY_ENGINE only returns 'ruby' on MRI.
-    # MRI 1.8.7 lacks the constant but all other rubies have it (including JRuby in 1.8 mode)
+  # RUBY_ENGINE only returns 'ruby' on MRI.
+  if ruby -e "exit(RUBY_ENGINE == 'ruby')"; then
     return 0
   else
     return 1
@@ -12,59 +11,14 @@ function is_mri {
 }
 
 function is_jruby {
-  if ruby -e "exit(defined?(RUBY_PLATFORM) && RUBY_PLATFORM == 'java')"; then
-    # RUBY_ENGINE only returns 'ruby' on MRI.
-    # MRI 1.8.7 lacks the constant but all other rubies have it (including JRuby in 1.8 mode)
+  # RUBY_PLATFORM only returns 'java' on JRuby.
+  if ruby -e "exit(RUBY_PLATFORM == 'java')"; then
     return 0
   else
     return 1
   fi;
 }
 
-function is_mri_192 {
-  if is_mri; then
-    if ruby -e "exit(RUBY_VERSION == '1.9.2')"; then
-      return 0
-    else
-      return 1
-    fi
-  else
-    return 1
-  fi
-}
-
-function is_mri_192_plus {
-  if is_mri; then
-    if ruby -e "exit(RUBY_VERSION.to_f > 1.8)"; then
-      return 0
-    else
-      return 1
-    fi
-  else
-    return 1
-  fi
-}
-
-function is_mri_2plus {
-  if is_mri; then
-    if ruby -e "exit(RUBY_VERSION.to_f > 2.0)"; then
-      return 0
-    else
-      return 1
-    fi
-  else
-    return 1
-  fi
-}
-
-function is_ruby_23_plus {
-  if ruby -e "exit(RUBY_VERSION.to_f >= 2.3)"; then
-    return 0
-  else
-    return 1
-  fi
-}
-
 function is_ruby_25_plus {
   if ruby -e "exit(RUBY_VERSION.to_f >= 2.5)"; then
     return 0
@@ -81,14 +35,6 @@ function rspec_rails_compatible {
   fi
 }
 
-function rspec_support_compatible {
-  if [ "$MAINTENANCE_BRANCH" != "2-99-maintenance" ] && [ "$MAINTENANCE_BRANCH" != "2-14-maintenance" ]; then
-    return 0
-  else
-    return 1
-  fi
-}
-
 function additional_specs_available {
   type run_additional_specs > /dev/null 2>&1
   return $?
@@ -96,7 +42,7 @@ function additional_specs_available {
 
 function documentation_enforced {
   if [ -x ./bin/yard ]; then
-    if is_mri_2plus; then
+    if is_mri; then
       return 0
     else
       return 1
diff --git a/script/run_build b/script/run_build
index a6aebb2bc1..4b1f8ef0e1 100755
--- a/script/run_build
+++ b/script/run_build
@@ -1,5 +1,5 @@
 #!/bin/bash
-# This file was generated on 2020-11-16T22:10:29+00:00 from the rspec-dev repo.
+# This file was generated on 2020-11-29T14:01:14+03:00 from the rspec-dev repo.
 # DO NOT modify it by hand as your changes will get lost the next time it is generated.
 
 set -e
diff --git a/script/update_rubygems_and_install_bundler b/script/update_rubygems_and_install_bundler
index f244a3f155..6ea8b36719 100755
--- a/script/update_rubygems_and_install_bundler
+++ b/script/update_rubygems_and_install_bundler
@@ -1,15 +1,9 @@
 #!/bin/bash
-# This file was generated on 2020-11-16T22:10:29+00:00 from the rspec-dev repo.
+# This file was generated on 2020-11-29T14:01:14+03:00 from the rspec-dev repo.
 # DO NOT modify it by hand as your changes will get lost the next time it is generated.
 
 set -e
 source script/functions.sh
 
-if is_ruby_23_plus; then
-  yes | gem update --system
-  yes | gem install bundler
-else
-  echo "Warning installing older versions of Rubygems / Bundler"
-  gem update --system '2.7.8'
-  gem install bundler -v '1.17.3'
-fi
+yes | gem update --system
+yes | gem install bundler
diff --git a/spec/integration/bisect_spec.rb b/spec/integration/bisect_spec.rb
index 820ca4d8c9..74fbf57995 100644
--- a/spec/integration/bisect_spec.rb
+++ b/spec/integration/bisect_spec.rb
@@ -4,10 +4,6 @@ module RSpec::Core
   RSpec.describe "Bisect", :slow, :simulate_shell_allowing_unquoted_ids do
     include FormatterSupport
 
-    before do
-      skip "These specs do not consistently pass or fail on AppVeyor on Ruby 2.1+"
-    end if ENV['APPVEYOR'] && RUBY_VERSION.to_f > 2.0
-
     def bisect(cli_args, expected_status=nil)
       options = ConfigurationOptions.new(cli_args)
 
diff --git a/spec/rspec/core/configuration_spec.rb b/spec/rspec/core/configuration_spec.rb
index 2ea3622817..f007fd3328 100644
--- a/spec/rspec/core/configuration_spec.rb
+++ b/spec/rspec/core/configuration_spec.rb
@@ -535,9 +535,7 @@ def stub_expectation_adapters
         expect(config.files_to_run).to contain_files("./spec/rspec/core/resources/a_spec.rb")
       end
 
-      it "supports absolute path patterns", :failing_on_appveyor,
-        :pending => false,
-        :skip => (ENV['APPVEYOR'] ? "Failing on AppVeyor but :pending isn't working for some reason" : false) do
+      it "supports absolute path patterns" do
         dir = File.expand_path("../resources", __FILE__)
         config.pattern = File.join(dir, "**/*_spec.rb")
         assign_files_or_directories_to_run "spec"
@@ -618,7 +616,8 @@ def stub_expectation_adapters
           expect(config.files_to_run).to contain_files("C:/path/to/project/spec/sub/foo_spec.rb")
         end
 
-        it "loads files in Windows when directory is specified", :failing_on_appveyor, :if => RSpec::Support::OS.windows? do
+        it "loads files in Windows when directory is specified", :if => RSpec::Support::OS.windows? do
+          pending "Fails for some reason yet to be discovered"
           assign_files_or_directories_to_run "spec\\rspec\\core\\resources"
           expect(config.files_to_run).to contain_files("spec/rspec/core/resources/a_spec.rb")
         end
diff --git a/spec/rspec/core/rake_task_spec.rb b/spec/rspec/core/rake_task_spec.rb
index ae2c9e636f..58fa66432e 100644
--- a/spec/rspec/core/rake_task_spec.rb
+++ b/spec/rspec/core/rake_task_spec.rb
@@ -308,9 +308,7 @@ def self.it_configures_rspec_load_path(description, path_template)
       end
 
       context "that is an absolute path file glob" do
-        it "loads the matching spec files", :failing_on_appveyor,
-        :pending => false,
-        :skip => (ENV['APPVEYOR'] ? "Failing on AppVeyor but :pending isn't working for some reason" : false) do
+        it "loads the matching spec files" do
           dir = File.expand_path("../resources", __FILE__)
           task.pattern = File.join(dir, "**/*_spec.rb")
 
@@ -443,7 +441,8 @@ def make_files_in_dir(dir)
     context "with paths with quotes or spaces" do
       include_context "isolated directory"
 
-      it "matches files with quotes and spaces", :failing_on_appveyor do
+      it "matches files with quotes and spaces" do
+        pending "Fails on Windows for some reason yet to be discovered" if RSpec::Support::OS.windows?
         spec_dir = File.join(Dir.getwd, "spec")
         task.pattern = "spec/*spec.rb"
         FileUtils.mkdir_p(spec_dir)