Use new GitHub Actions macOS Tahoe (26) runner

Let's use this in the specific places where we use a specific macOS
version for the runner.

Author: MikeMcQuaid

.github/workflows/pkg-installer.yml

@@ -25,7 +25,7 @@ defaults:
 jobs:
   build:
     if: github.repository_owner == 'Homebrew' && github.actor != 'dependabot[bot]'
-    runs-on: macos-15
+    runs-on: macos-26
     outputs:
       installer_path: "Homebrew-${{ steps.homebrew-version.outputs.version }}.pkg"
     env:
@@ -154,8 +154,8 @@ jobs:
         include:
           - runner: macos-14
             name: macos-14-arm64
-          - runner: macos-15
-            name: macos-15-arm64
+          - runner: macos-26
+            name: macos-26-arm64
     steps:
       - name: Download installer from GitHub Actions
         uses: actions/download-artifact@634f93cb2916e3fdff6788551b99b062d0335ce0 # v5.0.0
@@ -205,7 +205,7 @@ jobs:
 
   upload:
     needs: [build, test]
-    runs-on: macos-15
+    runs-on: macos-26
     permissions:
       # To write assets to GitHub release
       contents: write

.github/workflows/sorbet.yml

@@ -26,7 +26,7 @@ defaults:
 jobs:
   tapioca:
     if: github.repository == 'Homebrew/brew'
-    runs-on: macos-15
+    runs-on: macos-26
     steps:
       - name: Set up Homebrew
         id: set-up-homebrew

.github/workflows/tests.yml

@@ -81,7 +81,7 @@ jobs:
     name: tap syntax
     needs: syntax
     if: github.repository_owner == 'Homebrew'
-    runs-on: macos-15
+    runs-on: macos-26
     steps:
       - name: Set up Homebrew
         id: set-up-homebrew
@@ -155,7 +155,7 @@ jobs:
     name: cask audit
     needs: syntax
     if: github.repository_owner == 'Homebrew' && github.event_name != 'push'
-    runs-on: macos-15
+    runs-on: macos-26
     steps:
       - name: Set up Homebrew
         id: set-up-homebrew
@@ -248,7 +248,7 @@ jobs:
             runs-on: ubuntu-24.04
           - name: tests (macOS)
             test-flags: --coverage
-            runs-on: macos-15
+            runs-on: macos-26
     steps:
       - name: Set up Homebrew
         id: set-up-homebrew
@@ -360,7 +360,7 @@ jobs:
           - name: test-bot (macOS x86_64)
             runs-on: macos-13
           - name: test-bot (macOS arm64)
-            runs-on: macos-15
+            runs-on: macos-26
     env:
       HOMEBREW_TEST_BOT_ANALYTICS: 1
       HOMEBREW_ENFORCE_SBOM: 1

.github/workflows/vendor-gems.yml

@@ -28,7 +28,7 @@ defaults:
 jobs:
   vendor-gems:
     if: github.repository_owner == 'Homebrew'
-    runs-on: macos-15
+    runs-on: macos-26
     steps:
       - name: Set up Homebrew
         id: set-up-homebrew

Library/Homebrew/dev-cmd/generate-cask-ci-matrix.rb

@@ -17,8 +17,9 @@ class GenerateCaskCiMatrix < AbstractCommand
         { symbol: :ventura, name: "macos-13", arch: :intel } => 1.0,
       }.freeze, T::Hash[T::Hash[Symbol, T.any(Symbol, String)], Float])
       ARM_RUNNERS = T.let({
-        { symbol: :sonoma, name: "macos-14", arch: :arm }  => 0.0,
-        { symbol: :sequoia, name: "macos-15", arch: :arm } => 1.0,
+        { symbol: :sonoma,  name: "macos-14", arch: :arm } => 0.0,
+        { symbol: :sequoia, name: "macos-15", arch: :arm } => 0.0,
+        { symbol: :tahoe,   name: "macos-26", arch: :arm } => 1.0,
       }.freeze, T::Hash[T::Hash[Symbol, T.any(Symbol, String)], Float])
       RUNNERS = T.let(INTEL_RUNNERS.merge(ARM_RUNNERS).freeze,
                       T::Hash[T::Hash[Symbol, T.any(Symbol, String)], Float])

Library/Homebrew/dev-cmd/tap-new.rb

@@ -83,7 +83,7 @@ def run
             test-bot:
               strategy:
                 matrix:
-                  os: [ ubuntu-22.04, macos-13, macos-15 ]
+                  os: [ ubuntu-22.04, macos-13, macos-26 ]
               runs-on: ${{ matrix.os }}
               permissions:
                 actions: read