diff --git a/.github/workflows/ubuntu-lint.yml b/.github/workflows/ubuntu-lint.yml
index dde74cadc8a5..f4455d63fbe2 100644
--- a/.github/workflows/ubuntu-lint.yml
+++ b/.github/workflows/ubuntu-lint.yml
@@ -131,7 +131,9 @@ jobs:
           bin/rake dev:deps version:update_locked_bundler
           git config user.name "github-actions[bot]"
           git config user.email "github-actions[bot]@users.noreply.github.com"
-          git commit -am "Simulate release version"
+          # On release branches the version constants already have no .dev suffix,
+          # so there is nothing to simulate and nothing to commit.
+          git diff --quiet || git commit -am "Simulate release version"
       - name: Check lockfiles do not depend on the local gem cache
         run: |
           version=$(ruby -Ilib -rbundler/version -e 'puts Bundler::VERSION')
diff --git a/CHANGELOG.md b/CHANGELOG.md
index b70a4148a033..2795893675f6 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -2,6 +2,103 @@
 
 Bundler's changelog before 4.0.0, when it was versioned separately from RubyGems, is in [doc/CHANGELOG-bundler-2.x.md](https://github.com/ruby/rubygems/blob/master/doc/CHANGELOG-bundler-2.x.md).
 
+## 4.1.0.beta1 / 2026-09-09
+
+### RubyGems
+
+Changes already released in 4.0.x are not repeated here.
+
+#### Features:
+
+* Add content addressable gems support. Pull request [#9773](https://github.com/ruby/rubygems/pull/9773) by Jenny Shen
+* Let the gem and bundle cooldown settings cover each other. Pull request [#9852](https://github.com/ruby/rubygems/pull/9852) by Hiroshi SHIBATA
+* Rubygems: Add PQC ML-DSA support for cryptographically signed gems workflow. Pull request [#9697](https://github.com/ruby/rubygems/pull/9697) by Jun Aruga
+* Preserve non-UTF-8 legacy gem metadata. Pull request [#9835](https://github.com/ruby/rubygems/pull/9835) by Stanislav (Stas) Katkov
+* Add an opt-in OS credential store for gem and bundler credentials. Pull request [#9671](https://github.com/ruby/rubygems/pull/9671) by Hiroshi SHIBATA
+* Add --cooldown to gem install, update and outdated. Pull request [#9734](https://github.com/ruby/rubygems/pull/9734) by Hiroshi SHIBATA
+* Adopt the compact index for gem commands. Pull request [#9606](https://github.com/ruby/rubygems/pull/9606) by Hiroshi SHIBATA
+* Replace Molinillo with PubGrub for dependency resolution. Pull request [#9402](https://github.com/ruby/rubygems/pull/9402) by Matt Larraz
+* Replace the rubygems-specific lockfile parser with Bundler's parser. Pull request [#9564](https://github.com/ruby/rubygems/pull/9564) by Hiroshi SHIBATA
+* Remove pessimistic versioning in gem command output. Pull request [#9550](https://github.com/ruby/rubygems/pull/9550) by Jeremy Evans
+* Change Gem::Version#approximate_recommendation to be optimistic. Pull request [#9537](https://github.com/ruby/rubygems/pull/9537) by Jeremy Evans
+* Add `--no-build-extension` and `--no-install-plugin` options to gem install. Pull request [#9473](https://github.com/ruby/rubygems/pull/9473) by Hiroshi SHIBATA
+* Push with auto-attestation. Pull request [#9325](https://github.com/ruby/rubygems/pull/9325) by Hiroshi SHIBATA
+* Implement yaml parser written by pure ruby instead of Psych. Pull request [#9352](https://github.com/ruby/rubygems/pull/9352) by Hiroshi SHIBATA
+* Honor concurrent_downloads from .gemrc in Gem::ConfigFile. Pull request [#9339](https://github.com/ruby/rubygems/pull/9339) by Andrii Furmanets
+* Add support for custom error response from external registries. Pull request [#9270](https://github.com/ruby/rubygems/pull/9270) by Luis J. Gonzalez
+* Add global gem cache shared by RubyGems and Bundler. Pull request [#9230](https://github.com/ruby/rubygems/pull/9230) by Anthony Panozzo
+* Write gem files atomically. Pull request [#9154](https://github.com/ruby/rubygems/pull/9154) by Eileen
+
+#### Performance:
+
+* Remove `verify_gz`. Pull request [#9093](https://github.com/ruby/rubygems/pull/9093) by Eileen
+
+#### Enhancements:
+
+* Normalize absolute symlink targets during gem extraction. Pull request [#9860](https://github.com/ruby/rubygems/pull/9860) by Hiroshi SHIBATA
+* Installs bundler 4.1.0.beta1 as a default gem.
+
+#### Breaking changes:
+
+* Stop installing native extension build logs. Pull request [#9700](https://github.com/ruby/rubygems/pull/9700) by Hiroshi SHIBATA
+* Remove Gem::BasicSpecification#datadir and check minor-release deprecation horizons. Pull request [#9842](https://github.com/ruby/rubygems/pull/9842) by Hiroshi SHIBATA
+* Raise an error when building a gem that has a self reference. Pull request [#9392](https://github.com/ruby/rubygems/pull/9392) by Edouard CHIN
+* Revert `DEFAULT_INSTALL_EXTENSION_IN_LIB` and warn `require_relative` with C ext. Pull request [#9390](https://github.com/ruby/rubygems/pull/9390) by Hiroshi SHIBATA
+* Remove deprecated and unused `Gem::List`. Pull request [#9161](https://github.com/ruby/rubygems/pull/9161) by Hiroshi SHIBATA
+
+### Bundler
+
+Changes already released in 4.0.x are not repeated here.
+
+#### Features:
+
+* Add content addressable gems support. Pull request [#9773](https://github.com/ruby/rubygems/pull/9773) by Jenny Shen
+* Let the gem and bundle cooldown settings cover each other. Pull request [#9852](https://github.com/ruby/rubygems/pull/9852) by Hiroshi SHIBATA
+* Add a `prune` setting to drop rebuildable install artifacts. Pull request [#9815](https://github.com/ruby/rubygems/pull/9815) by Hiroshi SHIBATA
+* Add an opt-in OS credential store for gem and bundler credentials. Pull request [#9671](https://github.com/ruby/rubygems/pull/9671) by Hiroshi SHIBATA
+* Fetch Bundler metadata through Gem::Request instead of net-http-persistent. Pull request [#9786](https://github.com/ruby/rubygems/pull/9786) by Hiroshi SHIBATA
+* Reuse RubyGems' compact index client in Bundler. Pull request [#9753](https://github.com/ruby/rubygems/pull/9753) by Hiroshi SHIBATA
+* Reuse RubyGems' vendored PubGrub in Bundler. Pull request [#9752](https://github.com/ruby/rubygems/pull/9752) by Hiroshi SHIBATA
+* Use RubyGems' YAML serializer in Bundler. Pull request [#9751](https://github.com/ruby/rubygems/pull/9751) by Hiroshi SHIBATA
+* Reuse RubyGems' vendored SecureRandom in Bundler. Pull request [#9651](https://github.com/ruby/rubygems/pull/9651) by Hiroshi SHIBATA
+* Reuse RubyGems' vendored URI in Bundler. Pull request [#9650](https://github.com/ruby/rubygems/pull/9650) by Hiroshi SHIBATA
+* Fix two issues by including the ruby platform variants in the lock file. Pull request [#9556](https://github.com/ruby/rubygems/pull/9556) by Randy Stauner
+* Fix plugin installation from gemfile. Pull request [#6957](https://github.com/ruby/rubygems/pull/6957) by Cody Cutrer
+* Add plugin hooks for Gemfile evaluation and source fetching. Pull request [#9488](https://github.com/ruby/rubygems/pull/9488) by Hiroshi SHIBATA
+* Use optimistic version constraints in bundle gem output. Pull request [#9533](https://github.com/ruby/rubygems/pull/9533) by Jeremy Evans
+* Extend Gemfile `override` DSL with `:all` target and metadata fields (Phase 2). Pull request [#9530](https://github.com/ruby/rubygems/pull/9530) by Hiroshi SHIBATA
+* Switch bundle add to use optimistic versioning by default. Pull request [#9526](https://github.com/ruby/rubygems/pull/9526) by Jeremy Evans
+* Add Gemfile `override` DSL for version constraints (Phase 1). Pull request [#9517](https://github.com/ruby/rubygems/pull/9517) by Hiroshi SHIBATA
+* Add `--no-build-extension` and `--no-install-plugin` options to gem install. Pull request [#9473](https://github.com/ruby/rubygems/pull/9473) by Hiroshi SHIBATA
+* Include detailed dependencies when gemfile and lockfile are conflicts. Pull request [#9332](https://github.com/ruby/rubygems/pull/9332) by Hiroshi SHIBATA
+* Implement relative path handling for plugin paths. Pull request [#9299](https://github.com/ruby/rubygems/pull/9299) by Hiroshi SHIBATA
+* Bundler/inline: perform installation from a forked child. Pull request [#7941](https://github.com/ruby/rubygems/pull/7941) by Jean byroot Boussier
+* Add global gem cache shared by RubyGems and Bundler. Pull request [#9230](https://github.com/ruby/rubygems/pull/9230) by Anthony Panozzo
+* Update custom errors with Exception#full_message. Pull request [#8488](https://github.com/ruby/rubygems/pull/8488) by neimadTL
+
+#### Performance:
+
+* Use separate Bundler download and installation workers. Pull request [#9777](https://github.com/ruby/rubygems/pull/9777) by Joshua Young
+* Cache a shared git source only once per command. Pull request [#9689](https://github.com/ruby/rubygems/pull/9689) by Hiroshi SHIBATA
+
+#### Enhancements:
+
+* Reject Bundler redirects that downgrade https to http. Pull request [#9859](https://github.com/ruby/rubygems/pull/9859) by Hiroshi SHIBATA
+
+#### Bug fixes:
+
+* Expand the git source gemspec path before the chdir. Pull request [#9845](https://github.com/ruby/rubygems/pull/9845) by Hiroshi SHIBATA
+
+#### Breaking changes:
+
+* Remove external tool version checks from `bundle env`. Pull request [#9593](https://github.com/ruby/rubygems/pull/9593) by Hiroshi SHIBATA
+* Bundler: ignore patchlevel kwarg in ruby DSL. Pull request [#6023](https://github.com/ruby/rubygems/pull/6023) by Takuya N
+* Unify RubyGems and Bundler documentation. Pull request [#9237](https://github.com/ruby/rubygems/pull/9237) by Hiroshi SHIBATA
+
+#### Deprecations:
+
+* Rename the no_prune setting to keep_outdated_cache. Pull request [#9816](https://github.com/ruby/rubygems/pull/9816) by Hiroshi SHIBATA
+
 ## 4.0.20 / 2026-09-02
 
 ### RubyGems
diff --git a/lib/bundler/version.rb b/lib/bundler/version.rb
index ca7bb0719aac..6a1de4efc6ba 100644
--- a/lib/bundler/version.rb
+++ b/lib/bundler/version.rb
@@ -1,7 +1,7 @@
 # frozen_string_literal: false
 
 module Bundler
-  VERSION = "4.1.0.dev".freeze
+  VERSION = "4.1.0.beta1".freeze
 
   def self.bundler_major_version
     @bundler_major_version ||= gem_version.segments.first
diff --git a/lib/rubygems.rb b/lib/rubygems.rb
index 0ff3beaea1f8..85b405595164 100644
--- a/lib/rubygems.rb
+++ b/lib/rubygems.rb
@@ -9,7 +9,7 @@
 require "rbconfig"
 
 module Gem
-  VERSION = "4.1.0.dev"
+  VERSION = "4.1.0.beta1"
 end
 
 require_relative "rubygems/defaults"
diff --git a/spec/realworld/fixtures/tapioca/Gemfile.lock b/spec/realworld/fixtures/tapioca/Gemfile.lock
index a08089a6f7b3..9bf8b9585bc1 100644
--- a/spec/realworld/fixtures/tapioca/Gemfile.lock
+++ b/spec/realworld/fixtures/tapioca/Gemfile.lock
@@ -46,4 +46,4 @@ DEPENDENCIES
   tapioca
 
 BUNDLED WITH
-  4.1.0.dev
+  4.1.0.beta1
diff --git a/spec/realworld/fixtures/warbler/Gemfile.lock b/spec/realworld/fixtures/warbler/Gemfile.lock
index 05f3bc4e3f1d..9e6c2fe23d7d 100644
--- a/spec/realworld/fixtures/warbler/Gemfile.lock
+++ b/spec/realworld/fixtures/warbler/Gemfile.lock
@@ -32,4 +32,4 @@ DEPENDENCIES
   warbler (~> 2.1)
 
 BUNDLED WITH
-  4.1.0.dev
+  4.1.0.beta1
diff --git a/tool/bundler/dev_gems.rb.lock b/tool/bundler/dev_gems.rb.lock
index 72916fb1e1d9..0e715aa3c559 100644
--- a/tool/bundler/dev_gems.rb.lock
+++ b/tool/bundler/dev_gems.rb.lock
@@ -132,4 +132,4 @@ CHECKSUMS
   turbo_tests (2.2.5) sha256=3fa31497d12976d11ccc298add29107b92bda94a90d8a0a5783f06f05102509f
 
 BUNDLED WITH
-  4.1.0.dev
+  4.1.0.beta1
diff --git a/tool/bundler/lint_gems.rb.lock b/tool/bundler/lint_gems.rb.lock
index 173ae3476c25..b9df1904cce9 100644
--- a/tool/bundler/lint_gems.rb.lock
+++ b/tool/bundler/lint_gems.rb.lock
@@ -129,4 +129,4 @@ CHECKSUMS
   wmi-lite (1.0.7) sha256=116ef5bb470dbe60f58c2db9047af3064c16245d6562c646bc0d90877e27ddda
 
 BUNDLED WITH
-  4.1.0.dev
+  4.1.0.beta1
diff --git a/tool/bundler/release_gems.rb.lock b/tool/bundler/release_gems.rb.lock
index a9d5e9496db4..e8755070d66f 100644
--- a/tool/bundler/release_gems.rb.lock
+++ b/tool/bundler/release_gems.rb.lock
@@ -87,4 +87,4 @@ CHECKSUMS
   uri (1.1.1) sha256=379fa58d27ffb1387eaada68c749d1426738bd0f654d812fcc07e7568f5c57c6
 
 BUNDLED WITH
-  4.1.0.dev
+  4.1.0.beta1
diff --git a/tool/bundler/rubocop_gems.rb.lock b/tool/bundler/rubocop_gems.rb.lock
index f265e7c9ebd5..b0b2899f3f8d 100644
--- a/tool/bundler/rubocop_gems.rb.lock
+++ b/tool/bundler/rubocop_gems.rb.lock
@@ -157,4 +157,4 @@ CHECKSUMS
   unicode-emoji (4.2.0) sha256=519e69150f75652e40bf736106cfbc8f0f73aa3fb6a65afe62fefa7f80b0f80f
 
 BUNDLED WITH
-  4.1.0.dev
+  4.1.0.beta1
diff --git a/tool/bundler/standard_gems.rb.lock b/tool/bundler/standard_gems.rb.lock
index 8ef7806bcc80..9b3ecaa36a90 100644
--- a/tool/bundler/standard_gems.rb.lock
+++ b/tool/bundler/standard_gems.rb.lock
@@ -177,4 +177,4 @@ CHECKSUMS
   unicode-emoji (4.2.0) sha256=519e69150f75652e40bf736106cfbc8f0f73aa3fb6a65afe62fefa7f80b0f80f
 
 BUNDLED WITH
-  4.1.0.dev
+  4.1.0.beta1
diff --git a/tool/bundler/test_gems.rb.lock b/tool/bundler/test_gems.rb.lock
index 0b9ac341625e..9ca68b3d9883 100644
--- a/tool/bundler/test_gems.rb.lock
+++ b/tool/bundler/test_gems.rb.lock
@@ -99,4 +99,4 @@ CHECKSUMS
   tilt (2.7.0) sha256=0d5b9ba69f6a36490c64b0eee9f6e9aad517e20dcc848800a06eb116f08c6ab3
 
 BUNDLED WITH
-  4.1.0.dev
+  4.1.0.beta1
diff --git a/tool/bundler/vendor_gems.rb.lock b/tool/bundler/vendor_gems.rb.lock
index 802c43cb4ed2..658650507209 100644
--- a/tool/bundler/vendor_gems.rb.lock
+++ b/tool/bundler/vendor_gems.rb.lock
@@ -57,4 +57,4 @@ CHECKSUMS
   uri (1.1.1) sha256=379fa58d27ffb1387eaada68c749d1426738bd0f654d812fcc07e7568f5c57c6
 
 BUNDLED WITH
-  4.1.0.dev
+  4.1.0.beta1