diff --git a/Library/Homebrew/github_runner_matrix.rb b/Library/Homebrew/github_runner_matrix.rb
index d4dab5766d349d..17f5355da041fe 100644
--- a/Library/Homebrew/github_runner_matrix.rb
+++ b/Library/Homebrew/github_runner_matrix.rb
@@ -60,6 +60,7 @@ def initialize(testing_formulae, deleted_formulae, all_supported:, dependent_mat
     @dependent_matrix = T.let(dependent_matrix, T::Boolean)
     @compatible_testing_formulae = T.let({}, T::Hash[GitHubRunner, T::Array[TestRunnerFormula]])
     @formulae_with_untested_dependents = T.let({}, T::Hash[GitHubRunner, T::Array[TestRunnerFormula]])
+    @deploy_new_x86_64_runner = T.let(all_supported, T::Boolean)
 
     @runners = T.let([], T::Array[GitHubRunner])
     generate_runners!
@@ -122,7 +123,7 @@ def create_runner(platform, arch, spec, macos_version = nil)
 
   NEWEST_HOMEBREW_CORE_MACOS_RUNNER = :sequoia
   OLDEST_HOMEBREW_CORE_MACOS_RUNNER = :ventura
-  NEWEST_HOMEBREW_CORE_INTEL_MACOS_RUNNER = :sonoma
+  NEWEST_DEFAULT_HOMEBREW_CORE_INTEL_MACOS_RUNNER = :sonoma
 
   sig { params(macos_version: MacOSVersion).returns(T::Boolean) }
   def runner_enabled?(macos_version)
@@ -175,10 +176,6 @@ def generate_runners!
     ephemeral_suffix << "-long" if runner_timeout == GITHUB_ACTIONS_LONG_TIMEOUT
     ephemeral_suffix.freeze
 
-    # `#deploy_new_x86_64_runner?` is expensive, so:
-    #  - avoid calling it if we don't have to
-    #  - cache the result to a variable to avoid calling it multiple times
-    deploy_new_x86_64_runner = @all_supported || deploy_new_x86_64_runner?
     MacOSVersion::SYMBOLS.each_value do |version|
       macos_version = MacOSVersion.new(version)
       next unless runner_enabled?(macos_version)
@@ -202,7 +199,13 @@ def generate_runners!
       )
       @runners << create_runner(:macos, :arm64, spec, macos_version)
 
-      next if macos_version > NEWEST_HOMEBREW_CORE_INTEL_MACOS_RUNNER && !deploy_new_x86_64_runner
+      # `#deploy_new_x86_64_runner?` is expensive, so:
+      #  - avoid calling it if we don't have to
+      #  - cache the result to a variable to avoid calling it multiple times
+      if macos_version > NEWEST_DEFAULT_HOMEBREW_CORE_INTEL_MACOS_RUNNER &&
+         !(@deploy_new_x86_64_runner ||= deploy_new_x86_64_runner?)
+        next
+      end
 
       github_runner_available = macos_version <= NEWEST_GITHUB_ACTIONS_INTEL_MACOS_RUNNER &&
                                 macos_version >= OLDEST_GITHUB_ACTIONS_INTEL_MACOS_RUNNER