diff --git a/.github/workflows/release.yml b/.github/workflows/release.yml
index f1f747c..7c4e5c1 100644
--- a/.github/workflows/release.yml
+++ b/.github/workflows/release.yml
@@ -104,11 +104,11 @@ jobs:
             xcode_components: '"MetalToolchain"'
             disk_size: 380
           - macos_version: tahoe
-            xcode_versions: '"26.5","27-beta","26.4.1","26.3","26.2","26.1.1","26.0.1"'
+            xcode_versions: '"26.6","27-beta-2","26.5","27-beta","26.4.1","26.3","26.2","26.1.1","26.0.1"'
             additional_ios_builds: "18.6"
             additional_tvos_builds: ""
             xcode_components: '"MetalToolchain"'
-            disk_size: 330
+            disk_size: 520
     env:
       ADDITIONAL_IOS_BUILDS: ${{ matrix.additional_ios_builds }}
       ADDITIONAL_TVOS_BUILDS: ${{ matrix.additional_tvos_builds }}
diff --git a/.github/workflows/template-validation.yml b/.github/workflows/template-validation.yml
new file mode 100644
index 0000000..eb58199
--- /dev/null
+++ b/.github/workflows/template-validation.yml
@@ -0,0 +1,380 @@
+name: Template Builds
+
+on:
+  pull_request:
+    paths:
+      - ".github/workflows/monthly.yml"
+      - ".github/workflows/release.yml"
+      - ".github/workflows/template-validation.yml"
+      - "data/**"
+      - "scripts/**"
+      - "templates/**"
+
+permissions:
+  contents: read
+  packages: read
+
+concurrency:
+  group: template-builds-${{ github.event.pull_request.number || github.ref }}
+  cancel-in-progress: true
+
+env:
+  FASTLANE_SESSION: ${{ secrets.FASTLANE_SESSION }}
+  FASTLANE_USER: ${{ secrets.FASTLANE_USER }}
+  HOMEBREW_NO_AUTO_UPDATE: 1
+  HOMEBREW_NO_INSTALL_CLEANUP: 1
+  PACKER_GITHUB_API_TOKEN: ${{ secrets.GITHUB_TOKEN }}
+  TART_REGISTRY_HOSTNAME: ghcr.io
+  TART_REGISTRY_USERNAME: ${{ github.actor }}
+  TART_REGISTRY_PASSWORD: ${{ secrets.GITHUB_TOKEN }}
+
+jobs:
+  packer-validate:
+    name: Packer Validate
+    runs-on: macos-15
+    timeout-minutes: 30
+
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v4
+
+      - name: Setup Packer
+        uses: hashicorp/setup-packer@v3
+
+      - name: Install validation dependencies
+        run: |
+          brew install ansible
+
+      - name: Prepare validation inputs
+        run: |
+          mkdir -p "$HOME/XcodesCache"
+          touch "$HOME/XcodesCache/Xcode_26.6.xip"
+
+      - name: Validate templates
+        run: |
+          set -euo pipefail
+
+          validate() {
+            local template="$1"
+            shift
+
+            packer init "$template"
+            packer validate "$@" "$template"
+          }
+
+          for template in templates/vanilla-*.pkr.hcl; do
+            validate "$template"
+          done
+
+          validate templates/base.pkr.hcl \
+            -var vm_name=template-validation-base
+
+          validate templates/disable-sip.pkr.hcl \
+            -var vm_name=template-validation-disable-sip
+
+          validate templates/disable-sip-with-username.pkr.hcl \
+            -var vm_name=template-validation-disable-sip-user
+
+          validate templates/exex-script.pkr.hcl \
+            -var vm_name=template-validation-exec \
+            -var script_path=scripts/finalize-tahoe.sh
+
+          validate templates/resolve-macos-number.pkr.hcl \
+            -var vm_base_name=template-validation-base \
+            -var vm_name=template-validation-resolve \
+            -var resolve_file=macos-version.txt
+
+          validate templates/xcode.pkr.hcl \
+            -var macos_version=tahoe \
+            -var 'xcode_version=["26.6"]' \
+            -var expected_runtimes_file=data/expected.tahoe.runtimes.txt
+
+  build-vanilla:
+    name: Build Vanilla Image (${{ matrix.macos_version }})
+    needs: packer-validate
+    if: github.event.pull_request.head.repo.full_name == github.repository
+    runs-on: [self-hosted, macOS, ARM64]
+    timeout-minutes: 180
+    strategy:
+      fail-fast: false
+      max-parallel: 1
+      matrix:
+        macos_version:
+          - tahoe
+          - sequoia
+          - sonoma
+          - monterey
+    env:
+      MACOS_VERSION: ${{ matrix.macos_version }}
+
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v4
+        with:
+          fetch-depth: 0
+
+      - name: Select image
+        id: select
+        env:
+          BASE_SHA: ${{ github.event.pull_request.base.sha }}
+          HEAD_SHA: ${{ github.event.pull_request.head.sha }}
+        run: |
+          set -euo pipefail
+
+          git diff --name-only "$BASE_SHA" "$HEAD_SHA" > changed-files.txt
+
+          build=false
+          if grep -Fxq "templates/vanilla-$MACOS_VERSION.pkr.hcl" changed-files.txt; then
+            build=true
+          fi
+
+          echo "build=$build" >> "$GITHUB_OUTPUT"
+
+      - name: Tool versions
+        if: steps.select.outputs.build == 'true'
+        run: |
+          tart --version
+          packer --version
+
+      - name: Build vanilla image
+        if: steps.select.outputs.build == 'true'
+        run: |
+          packer init "templates/vanilla-$MACOS_VERSION.pkr.hcl"
+          packer build "templates/vanilla-$MACOS_VERSION.pkr.hcl"
+
+      - name: Cleanup
+        if: always() && steps.select.outputs.build == 'true'
+        run: |
+          tart delete "$MACOS_VERSION-vanilla" || true
+
+  build-base:
+    name: Build Base Image (${{ matrix.macos_version }})
+    needs: packer-validate
+    if: github.event.pull_request.head.repo.full_name == github.repository
+    runs-on: [self-hosted, macOS, ARM64]
+    timeout-minutes: 180
+    strategy:
+      fail-fast: false
+      max-parallel: 1
+      matrix:
+        include:
+          - macos_version: sonoma
+            disable_sip_template: disable-sip.pkr.hcl
+          - macos_version: sequoia
+            disable_sip_template: disable-sip-with-username.pkr.hcl
+          - macos_version: tahoe
+            disable_sip_template: disable-sip-with-username.pkr.hcl
+    env:
+      DISABLE_SIP_TEMPLATE: ${{ matrix.disable_sip_template }}
+      MACOS_VERSION: ${{ matrix.macos_version }}
+
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v4
+        with:
+          fetch-depth: 0
+
+      - name: Select image
+        id: select
+        env:
+          BASE_SHA: ${{ github.event.pull_request.base.sha }}
+          HEAD_SHA: ${{ github.event.pull_request.head.sha }}
+        run: |
+          set -euo pipefail
+
+          git diff --name-only "$BASE_SHA" "$HEAD_SHA" > changed-files.txt
+
+          build=false
+          if grep -Eq '^(templates/base\.pkr\.hcl|templates/disable-sip.*\.pkr\.hcl|data/(github_known_hosts|limit\.maxfiles\.plist|setup-info-template\.json|tart-guest-.*\.plist)|scripts/install-actions-runner\.sh|ansible/)' changed-files.txt; then
+            build=true
+          fi
+
+          echo "build=$build" >> "$GITHUB_OUTPUT"
+
+      - name: Tool versions
+        if: steps.select.outputs.build == 'true'
+        run: |
+          tart --version
+          packer --version
+
+      - name: Pull vanilla image
+        if: steps.select.outputs.build == 'true'
+        run: |
+          tart pull "ghcr.io/cirruslabs/macos-$MACOS_VERSION-vanilla:latest"
+          tart clone "ghcr.io/cirruslabs/macos-$MACOS_VERSION-vanilla:latest" "$MACOS_VERSION-base"
+
+      - name: Disable SIP
+        if: steps.select.outputs.build == 'true'
+        run: |
+          packer init "templates/$DISABLE_SIP_TEMPLATE"
+          packer build -var "vm_name=$MACOS_VERSION-base" "templates/$DISABLE_SIP_TEMPLATE"
+
+      - name: Build base image
+        if: steps.select.outputs.build == 'true'
+        run: |
+          packer init templates/base.pkr.hcl
+          packer build -var "vm_name=$MACOS_VERSION-base" templates/base.pkr.hcl
+
+      - name: Cleanup
+        if: always() && steps.select.outputs.build == 'true'
+        run: |
+          tart delete "$MACOS_VERSION-base" || true
+
+  build-runner:
+    name: Build Runner Image (${{ matrix.macos_version }})
+    needs: packer-validate
+    if: github.event.pull_request.head.repo.full_name == github.repository
+    runs-on: [self-hosted, macOS, ARM64]
+    timeout-minutes: 180
+    strategy:
+      fail-fast: false
+      max-parallel: 1
+      matrix:
+        include:
+          - macos_version: tahoe
+            xcode_versions: '"26.6","27-beta-2","26.5","27-beta","26.4.1","26.3","26.2","26.1.1","26.0.1"'
+            additional_ios_builds: "18.6"
+            additional_tvos_builds: ""
+            xcode_components: '"MetalToolchain"'
+            disk_size: 520
+          - macos_version: sequoia
+            xcode_versions: '"26.0.1",16.4,16.3,16.2,16.1,16'
+            additional_ios_builds: "18.5,18.4,18.2,17.5"
+            additional_tvos_builds: "17.5"
+            xcode_components: '"MetalToolchain"'
+            disk_size: 380
+    env:
+      ADDITIONAL_IOS_BUILDS: ${{ matrix.additional_ios_builds }}
+      ADDITIONAL_TVOS_BUILDS: ${{ matrix.additional_tvos_builds }}
+      DISK_SIZE: ${{ matrix.disk_size }}
+      MACOS_VERSION: ${{ matrix.macos_version }}
+      XCODE_COMPONENTS: ${{ matrix.xcode_components }}
+      XCODE_VERSIONS: ${{ matrix.xcode_versions }}
+
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v4
+        with:
+          fetch-depth: 0
+
+      - name: Select image
+        id: select
+        env:
+          BASE_SHA: ${{ github.event.pull_request.base.sha }}
+          HEAD_SHA: ${{ github.event.pull_request.head.sha }}
+        run: |
+          set -euo pipefail
+
+          git diff --name-only "$BASE_SHA" "$HEAD_SHA" > changed-files.txt
+
+          build=false
+          if grep -Fxq ".github/workflows/release.yml" changed-files.txt; then
+            build=true
+          elif grep -Fxq "data/expected.$MACOS_VERSION.runtimes.txt" changed-files.txt; then
+            build=true
+          elif grep -Fxq "scripts/finalize-$MACOS_VERSION.sh" changed-files.txt; then
+            build=true
+          elif grep -Eq '^(templates/xcode\.pkr\.hcl|data/setup-info-template\.json|scripts/install-actions-runner\.sh)$' changed-files.txt; then
+            build=true
+          fi
+
+          echo "build=$build" >> "$GITHUB_OUTPUT"
+
+      - name: Tool versions
+        if: steps.select.outputs.build == 'true'
+        run: |
+          tart --version
+          packer --version
+
+      - name: Pull base image
+        if: steps.select.outputs.build == 'true'
+        run: |
+          tart pull "ghcr.io/cirruslabs/macos-$MACOS_VERSION-base:latest"
+
+      - name: Prepare Xcode archives
+        if: steps.select.outputs.build == 'true'
+        run: |
+          set -euo pipefail
+
+          source ~/.zprofile || true
+
+          if ! command -v xcodes >/dev/null; then
+            brew install xcodes
+          fi
+
+          mkdir -p "$HOME/XcodesCache"
+          IFS=',' read -ra versions <<< "$XCODE_VERSIONS"
+
+          for raw_version in "${versions[@]}"; do
+            version="${raw_version//\"/}"
+            target="$HOME/XcodesCache/Xcode_${version}.xip"
+
+            if [[ -f "$target" ]]; then
+              echo "Using cached Xcode $version at $target"
+              continue
+            fi
+
+            echo "Downloading Xcode $version"
+            if [[ -z "${FASTLANE_SESSION:-}" ]]; then
+              echo "::error::Missing $target and FASTLANE_SESSION is not configured. Pre-cache the Xcode archive on the runner or add Apple Developer auth secrets."
+              exit 1
+            fi
+
+            download_args=(download "$version" --directory "$HOME/XcodesCache" --use-fastlane-auth)
+            if [[ -n "${FASTLANE_USER:-}" ]]; then
+              download_args+=(--fastlane-user "$FASTLANE_USER")
+            fi
+            xcodes "${download_args[@]}"
+
+            candidate=""
+            case "$version" in
+              27-beta-2)
+                candidate="$HOME/XcodesCache/Xcode_27_beta_2.xip"
+                ;;
+              27-beta)
+                candidate="$HOME/XcodesCache/Xcode_27_beta.xip"
+                ;;
+              *)
+                candidate="$(find "$HOME/XcodesCache" -maxdepth 1 -type f -name "Xcode_${version}*.xip" -print -quit)"
+                ;;
+            esac
+
+            if [[ -n "$candidate" && -f "$candidate" && "$candidate" != "$target" ]]; then
+              mv "$candidate" "$target"
+            fi
+
+            test -f "$target"
+          done
+
+      - name: Build runner image
+        if: steps.select.outputs.build == 'true'
+        run: |
+          packer init templates/xcode.pkr.hcl
+          packer build \
+            -var tag=runner \
+            -var "disk_size=$DISK_SIZE" \
+            -var disk_free_mb=100000 \
+            -var "macos_version=$MACOS_VERSION" \
+            -var "xcode_version=[$XCODE_VERSIONS]" \
+            -var "additional_ios_builds=[$ADDITIONAL_IOS_BUILDS]" \
+            -var "additional_tvos_builds=[$ADDITIONAL_TVOS_BUILDS]" \
+            -var "xcode_components=[$XCODE_COMPONENTS]" \
+            -var "expected_runtimes_file=data/expected.$MACOS_VERSION.runtimes.txt" \
+            templates/xcode.pkr.hcl
+
+      - name: Finalize runner image
+        if: steps.select.outputs.build == 'true'
+        run: |
+          if [[ -f "scripts/finalize-$MACOS_VERSION.sh" ]]; then
+            packer build \
+              -var "vm_name=$MACOS_VERSION-xcode:runner" \
+              -var "script_path=scripts/finalize-$MACOS_VERSION.sh" \
+              templates/exex-script.pkr.hcl
+          else
+            echo "Skipping prepare script for $MACOS_VERSION"
+          fi
+
+      - name: Cleanup
+        if: always() && steps.select.outputs.build == 'true'
+        run: |
+          tart delete "$MACOS_VERSION-xcode:runner" || true
diff --git a/data/expected.tahoe.runtimes.txt b/data/expected.tahoe.runtimes.txt
index f127beb..1f2ea35 100644
--- a/data/expected.tahoe.runtimes.txt
+++ b/data/expected.tahoe.runtimes.txt
@@ -5,12 +5,11 @@ iOS 26.1 (26.1 - 23B86) - com.apple.CoreSimulator.SimRuntime.iOS-26-1
 iOS 26.3 (26.3.1 - 23D8133) - com.apple.CoreSimulator.SimRuntime.iOS-26-3
 iOS 26.4 (26.4.1 - 23E254a) - com.apple.CoreSimulator.SimRuntime.iOS-26-4
 iOS 26.5 (26.5 - 23F77) - com.apple.CoreSimulator.SimRuntime.iOS-26-5
-tvOS 26.2 (26.2 - 23K51) - com.apple.CoreSimulator.SimRuntime.tvOS-26-2
-tvOS 26.4 (26.4 - 23L243a) - com.apple.CoreSimulator.SimRuntime.tvOS-26-4
+iOS 27.0 (27.0 - 24A5355p) - com.apple.CoreSimulator.SimRuntime.iOS-27-0
+iOS 27.0 (27.0 - 24A5370g) - com.apple.CoreSimulator.SimRuntime.iOS-27-0
 tvOS 26.5 (26.5 - 23L470) - com.apple.CoreSimulator.SimRuntime.tvOS-26-5
-watchOS 26.2 (26.2 - 23S303) - com.apple.CoreSimulator.SimRuntime.watchOS-26-2
-watchOS 26.4 (26.4 - 23T240b) - com.apple.CoreSimulator.SimRuntime.watchOS-26-4
+tvOS 27.0 (27.0 - 24J5305f) - com.apple.CoreSimulator.SimRuntime.tvOS-27-0
 watchOS 26.5 (26.5 - 23T570) - com.apple.CoreSimulator.SimRuntime.watchOS-26-5
-visionOS 26.2 (26.2 - 23N301) - com.apple.CoreSimulator.SimRuntime.xrOS-26-2
-visionOS 26.4 (26.4.1 - 23O249a) - com.apple.CoreSimulator.SimRuntime.xrOS-26-4
+watchOS 27.0 (27.0 - 24R5305f) - com.apple.CoreSimulator.SimRuntime.watchOS-27-0
 visionOS 26.5 (26.5 - 23O470) - com.apple.CoreSimulator.SimRuntime.xrOS-26-5
+visionOS 27.0 (27.0 - 24M5306g) - com.apple.CoreSimulator.SimRuntime.xrOS-27-0
diff --git a/templates/xcode.pkr.hcl b/templates/xcode.pkr.hcl
index 01ef7c5..f1f1990 100644
--- a/templates/xcode.pkr.hcl
+++ b/templates/xcode.pkr.hcl
@@ -16,39 +16,39 @@ variable "xcode_version" {
 }
 
 variable "additional_ios_builds" {
-  type = list(string)
+  type    = list(string)
   default = []
 }
 
 variable "additional_tvos_builds" {
-  type = list(string)
+  type    = list(string)
   default = []
 }
 
 variable "xcode_components" {
-  type    = list(string)
-  default = []
+  type        = list(string)
+  default     = []
   description = "Additional Xcode components to download."
 }
 
 variable "expected_runtimes_file" {
-  type    = string
-  default = ""
+  type        = string
+  default     = ""
   description = "Path to file containing expected simulator runtimes. If empty, runtime verification is skipped."
 }
 
 variable "tag" {
-  type = string
+  type    = string
   default = ""
 }
 
 variable "disk_size" {
-  type = number
+  type    = number
   default = 140
 }
 
 variable "disk_free_mb" {
-  type = number
+  type    = number
   default = 15000
 }
 
@@ -146,7 +146,7 @@ build {
   }
 
   provisioner "file" {
-    sources      = [ for version in var.xcode_version : pathexpand("~/XcodesCache/Xcode_${version}.xip")]
+    sources     = [for version in var.xcode_version : pathexpand("~/XcodesCache/Xcode_${version}.xip")]
     destination = "/Users/admin/Downloads/"
   }
 
@@ -161,7 +161,7 @@ build {
   // select the latest one as the default
   dynamic "provisioner" {
     for_each = local.xcode_install_provisioners
-    labels = ["shell"]
+    labels   = ["shell"]
     content {
       inline = provisioner.value.inline
     }
@@ -169,11 +169,11 @@ build {
 
   dynamic "provisioner" {
     for_each = length(var.xcode_version) > 2 ? [2] : []
-    labels = ["shell"]
+    labels   = ["shell"]
     content {
       inline = [
         "source ~/.zprofile",
-        "sudo xcodes select '${var.xcode_version[2]}'",
+        "sudo xcode-select -s /Applications/Xcode_${var.xcode_version[2]}.app/Contents/Developer",
         "xcodebuild -downloadAllPlatforms",
       ]
     }
@@ -181,11 +181,11 @@ build {
 
   dynamic "provisioner" {
     for_each = length(var.xcode_version) > 1 ? [1] : []
-    labels = ["shell"]
+    labels   = ["shell"]
     content {
       inline = [
         "source ~/.zprofile",
-        "sudo xcodes select '${var.xcode_version[1]}'",
+        "sudo xcode-select -s /Applications/Xcode_${var.xcode_version[1]}.app/Contents/Developer",
         "xcodebuild -downloadAllPlatforms",
       ]
     }
@@ -194,7 +194,7 @@ build {
   provisioner "shell" {
     inline = [
       "source ~/.zprofile",
-      "sudo xcodes select '${var.xcode_version[0]}'",
+      "sudo xcode-select -s /Applications/Xcode_${var.xcode_version[0]}.app/Contents/Developer",
       "xcodebuild -downloadAllPlatforms",
     ]
   }
@@ -232,8 +232,9 @@ build {
       "brew install libimobiledevice ideviceinstaller ios-deploy carthage",
       "brew install xcbeautify swiftformat swiftlint swiftgen licenseplist",
       "brew install mint",
-      "brew tap tuist/tuist",
-      "brew install --formula tuist",
+      "git clone --depth 1 https://github.com/tuist/homebrew-tuist.git \"$(brew --repository)/Library/Taps/tuist/homebrew-tuist\"",
+      "rm -rf \"$(brew --repository)/Library/Taps/tuist/homebrew-tuist/Casks\"",
+      "tuist_version=$(ruby -ne 'if $_ =~ %r{/download/([^/]+)/}; puts $1; exit; end' \"$(brew --repository)/Library/Taps/tuist/homebrew-tuist/Aliases/tuist\") && brew trust --formula \"tuist/tuist/tuist@$tuist_version\" && brew install --formula \"tuist/tuist/tuist@$tuist_version\"",
       "rbenv install 3.3.10",
       "rbenv global 3.3.10", # fastlane conflicts with 3.4.0+ https://github.com/fastlane/fastlane/issues/29527
       "gem update",
@@ -247,7 +248,7 @@ build {
   // Copy expected runtimes file if provided
   dynamic "provisioner" {
     for_each = var.expected_runtimes_file != "" ? [1] : []
-    labels = ["file"]
+    labels   = ["file"]
     content {
       source      = var.expected_runtimes_file
       destination = "/Users/admin/runtimes.expected.txt"
@@ -257,7 +258,7 @@ build {
   // Verify simulator runtimes match expected list if file was provided
   dynamic "provisioner" {
     for_each = var.expected_runtimes_file != "" ? [1] : []
-    labels = ["shell"]
+    labels   = ["shell"]
     content {
       inline = [
         "source ~/.zprofile",