diff --git a/.github/actions/setup/action.yml b/.github/actions/setup/action.yml
index 68adc1d7..96ee9cd7 100644
--- a/.github/actions/setup/action.yml
+++ b/.github/actions/setup/action.yml
@@ -12,11 +12,17 @@ inputs:
 runs:
   using: composite
   steps:
+    # JRuby 10 requires Java 21. The runner image defaults to an older Java.
+    - uses: actions/setup-java@dd06d9cba3e5552c54d9f8ea23572deb30010f7c # v6.0.0
+      if: ${{ startsWith(inputs.version, 'jruby') }}
+      with:
+        distribution: temurin
+        java-version: "21"
+
     - uses: ruby/setup-ruby@95ef2b042f9d7a56d8268cba8559e2842e2ad01b # v1.321.0
       with:
         ruby-version: ${{ inputs.version }}
-        # The Gemfile cooldown needs Bundler 4, which requires Ruby 3.2 or later.
-        bundler: ${{ startsWith(inputs.version, 'jruby-9') && '2' || '4.0.19' }}
+        bundler: "4.0.19"
 
     - name: Install dependencies
       if: ${{ inputs.install-dependencies == 'true' }}
diff --git a/.github/workflows/build-gem.yml b/.github/workflows/build-gem.yml
index 86fd1eca..fa70a6ea 100644
--- a/.github/workflows/build-gem.yml
+++ b/.github/workflows/build-gem.yml
@@ -6,7 +6,7 @@ on:
       version:
         description: "The version of ruby to build against"
         type: string
-        default: "3.2"
+        default: "3.4"
       upload-artifact:
         description: "Whether to upload the gem as an artifact"
         type: boolean
diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index d69b4995..088b1785 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -15,7 +15,7 @@ jobs:
     strategy:
       fail-fast: false
       matrix:
-        version: ["3.2", "3.4", "jruby-9.4"]
+        version: ["3.4", "4.0", "jruby-10.0"]
     with:
       version: ${{ matrix.version }}
 
@@ -27,7 +27,7 @@ jobs:
 
       - uses: ./.github/actions/setup
         with:
-          version: "3.2"
+          version: "3.4"
 
       - uses: ./.github/actions/build-docs
 
@@ -46,7 +46,7 @@ jobs:
 
       - uses: ./.github/actions/setup
         with:
-          version: "3.2"
+          version: "3.4"
 
       - name: Run tests
         run: bundle exec rspec spec
diff --git a/.github/workflows/manual-publish-docs.yml b/.github/workflows/manual-publish-docs.yml
index 08c26b95..7ab57c1a 100644
--- a/.github/workflows/manual-publish-docs.yml
+++ b/.github/workflows/manual-publish-docs.yml
@@ -14,7 +14,7 @@ jobs:
 
       - uses: ./.github/actions/setup
         with:
-          version: "3.2"
+          version: "3.4"
           install-dependencies: false
 
       - uses: ./.github/actions/build-docs
diff --git a/.github/workflows/manual-publish.yml b/.github/workflows/manual-publish.yml
index b50942d9..654a8e72 100644
--- a/.github/workflows/manual-publish.yml
+++ b/.github/workflows/manual-publish.yml
@@ -11,12 +11,12 @@ jobs:
   build-ruby-gem:
     uses: ./.github/workflows/build-gem.yml
     with:
-      version: "3.2"
+      version: "3.4"
 
   build-jruby-gem:
     uses: ./.github/workflows/build-gem.yml
     with:
-      version: "jruby-9.4"
+      version: "jruby-10.0"
 
   publish:
     runs-on: ubuntu-latest
@@ -32,7 +32,7 @@ jobs:
 
       - uses: ./.github/actions/setup
         with:
-          version: "3.2"
+          version: "3.4"
           install-dependencies: false
 
       - uses: launchdarkly/gh-actions/actions/release-secrets@release-secrets-v1
diff --git a/.github/workflows/release-please.yml b/.github/workflows/release-please.yml
index 3d1d044d..7b32d95e 100644
--- a/.github/workflows/release-please.yml
+++ b/.github/workflows/release-please.yml
@@ -25,14 +25,14 @@ jobs:
     if: ${{ needs.release-package.outputs.release-created == 'true' }}
     uses: ./.github/workflows/build-gem.yml
     with:
-      version: "3.2"
+      version: "3.4"
 
   build-jruby-gem:
     needs: ["release-package"]
     if: ${{ needs.release-package.outputs.release-created == 'true' }}
     uses: ./.github/workflows/build-gem.yml
     with:
-      version: "jruby-9.4"
+      version: "jruby-10.0"
 
   publish:
     runs-on: ubuntu-latest
@@ -49,7 +49,7 @@ jobs:
 
       - uses: ./.github/actions/setup
         with:
-          version: "3.2"
+          version: "3.4"
           install-dependencies: false
 
       - uses: launchdarkly/gh-actions/actions/release-secrets@release-secrets-v1
diff --git a/.rubocop.yml b/.rubocop.yml
index 0d93de48..988437dd 100644
--- a/.rubocop.yml
+++ b/.rubocop.yml
@@ -2,7 +2,7 @@ plugins:
   - rubocop-performance
 
 AllCops:
-  TargetRubyVersion: 3.1
+  TargetRubyVersion: 3.4
   Include:
     - lib/**/*.rb
     - spec/**/*.rb
diff --git a/README.md b/README.md
index 20ff5d72..6acadf29 100644
--- a/README.md
+++ b/README.md
@@ -16,7 +16,7 @@ LaunchDarkly overview
 Supported Ruby versions
 -----------------------
 
-This version of the LaunchDarkly SDK has a minimum Ruby version of 3.1.0.
+This version of the LaunchDarkly SDK has a minimum Ruby version of 3.4.0. On JRuby, the minimum is JRuby 10.0, which requires Java 21.
 
 Getting started
 -----------
diff --git a/launchdarkly-server-sdk.gemspec b/launchdarkly-server-sdk.gemspec
index 0940d6bc..ec9b6722 100644
--- a/launchdarkly-server-sdk.gemspec
+++ b/launchdarkly-server-sdk.gemspec
@@ -23,7 +23,7 @@ Gem::Specification.new do |spec|
   spec.files         = Dir["lib/**/*.rb", "README.md", "LICENSE.txt"]
   spec.executables   = spec.files.grep(%r{^bin/}) { |f| File.basename(f) }
   spec.require_paths = ["lib"]
-  spec.required_ruby_version = ">= 3.1.0"
+  spec.required_ruby_version = ">= 3.4.0"
 
   spec.add_development_dependency "aws-sdk-dynamodb", "~> 1.57"
   spec.add_development_dependency "bigdecimal", "~> 3.1.1" # Neccessary for aws-sdk-dynamodb https://github.com/aws/aws-sdk-ruby/issues/3271