diff --git a/.buildkite/shared-pipeline-vars b/.buildkite/shared-pipeline-vars
index d455cab46..4e1f767fc 100644
--- a/.buildkite/shared-pipeline-vars
+++ b/.buildkite/shared-pipeline-vars
@@ -1,8 +1,9 @@
 #!/bin/bash
 
-export IMAGE_ID="xcode-26.1.1"
+export IMAGE_ID="xcode-26.6"
 export CI_TOOLKIT="automattic/a8c-ci-toolkit#5.7.0"
 export DOCKER_PLUGIN="docker#v5.13.0"
 SCRIPT_DIR="$(cd "$(dirname "${BASH_SOURCE[0]}")" && pwd)"
-export RUBY_VERSION="$(cat "$SCRIPT_DIR/../.ruby-version")"
+RUBY_VERSION="$(cat "$SCRIPT_DIR/../.ruby-version")"
+export RUBY_VERSION
 export DOCKER_RUBY_IMAGE="public.ecr.aws/docker/library/ruby:$RUBY_VERSION"
diff --git a/.ruby-version b/.ruby-version
index 19ef286ee..7bcbb3808 100644
--- a/.ruby-version
+++ b/.ruby-version
@@ -1,2 +1 @@
-3.2.2
-
+3.4.9
diff --git a/CHANGELOG.md b/CHANGELOG.md
index 12bed920d..a9c70a380 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -25,6 +25,7 @@ _None_
 - Added regression coverage for `upload_github_release_assets` direct release lookup errors. [#755]
 - Centralized `.strings` duplicate-key detection behind `StringsFileValidationHelper.scan_for_duplicate_keys`, returning a `[:scanned | :unsupported_format | :unscannable, payload]` tri-state that callers can map to their own warn-and-skip vs fail-closed policy. [#741]
 - `L10nHelper.strings_file_type` and `StringsFileValidationHelper.scan_for_duplicate_keys` accept `assume_valid:` to skip a redundant `plutil -lint` when the caller has already parsed the file. [#741]
+- Bumped development Ruby version to 3.4.9 [#729]
 
 ## 14.10.0
 
diff --git a/Gemfile b/Gemfile
index 426cb96e8..f21e6827b 100644
--- a/Gemfile
+++ b/Gemfile
@@ -4,14 +4,27 @@ source('https://rubygems.org')
 
 gemspec
 
+# Only needed for specs (Time.use_zone, String#to_time, Hash#slice!)
+gem 'activesupport', '~> 8.1'
 gem 'buildkite-test_collector', '~> 2.3'
 gem 'codecov', require: false
 gem 'danger-dangermattic', '~> 1.0'
-gem 'webmock', require: false
-gem 'yard'
-
 # Security:
 # - https://github.com/lostisland/faraday/pull/1665
 # - https://github.com/lostisland/faraday/pull/1681
+#
 # Faraday 2.0 is not compatible with Fastlane
+#
+# See also:
+# - https://github.com/fastlane/fastlane/issues/21334
+# - https://github.com/fastlane/fastlane/pull/30089
 gem 'faraday', '~> 1.10', '>= 1.10.6'
+gem 'pry', '~> 0.12.2'
+gem 'rmagick', '~> 5.3'
+gem 'rspec', '~> 3.8'
+gem 'rspec_junit_formatter', '~> 0.4.1'
+gem 'rubocop', '~> 1.65'
+gem 'rubocop-rspec', '3.0'
+gem 'simplecov', '~> 0.16.1'
+gem 'webmock', require: false
+gem 'yard'
diff --git a/Gemfile.lock b/Gemfile.lock
index f54cdf336..09f38f741 100644
--- a/Gemfile.lock
+++ b/Gemfile.lock
@@ -438,11 +438,9 @@ PLATFORMS
 DEPENDENCIES
   activesupport (~> 8.1)
   buildkite-test_collector (~> 2.3)
-  bundler (~> 2.0)
   codecov
   danger-dangermattic (~> 1.0)
   faraday (~> 1.10, >= 1.10.6)
-  fastlane (~> 2.210)
   fastlane-plugin-wpmreleasetoolkit!
   pry (~> 0.12.2)
   rmagick (~> 5.3)
@@ -455,4 +453,4 @@ DEPENDENCIES
   yard
 
 BUNDLED WITH
-   2.6.8
+  4.0.17
diff --git a/fastlane-plugin-wpmreleasetoolkit.gemspec b/fastlane-plugin-wpmreleasetoolkit.gemspec
index a4d84aae7..a19815b54 100644
--- a/fastlane-plugin-wpmreleasetoolkit.gemspec
+++ b/fastlane-plugin-wpmreleasetoolkit.gemspec
@@ -42,18 +42,4 @@ Gem::Specification.new do |spec|
 
   # `google-cloud-storage` is required by fastlane, but we pin it in case it's not in the future
   spec.add_dependency 'google-cloud-storage', '~> 1.31'
-
-  # Only needed for specs (Time.use_zone, String#to_time, Hash#slice!)
-  spec.add_development_dependency 'activesupport', '~> 8.1'
-  spec.add_development_dependency 'bundler', '~> 2.0'
-  # Use at least Fastlane 2.210.0 to ensure compatibility with the Xcode 14 toolchain
-  # See https://github.com/fastlane/fastlane/releases/tag/2.210.0
-  spec.add_development_dependency 'fastlane', '~> 2.210'
-  spec.add_development_dependency 'pry', '~> 0.12.2'
-  spec.add_development_dependency 'rmagick', '~> 5.3'
-  spec.add_development_dependency 'rspec', '~> 3.8'
-  spec.add_development_dependency 'rspec_junit_formatter', '~> 0.4.1'
-  spec.add_development_dependency 'rubocop', '~> 1.65'
-  spec.add_development_dependency 'rubocop-rspec', '3.0'
-  spec.add_development_dependency 'simplecov', '~> 0.16.1'
 end