ci: move iOS/Mac Catalyst sample jobs from macos-15 to macos-26 (#626)

macOS arm64 jobs on macos-15 repeatedly failed to acquire a runner due to
capacity constraints. Switch the MAUI, Avalonia and Uno iOS jobs to
macos-26, keep the existing workload set and Xcode 26.3 pins (Xcode 26.3 is
still installed on macos-26), and update the explanatory comments.

Closes #622

Author: adrianhall

.github/workflows/build-samples-todoapp-avalonia.yml

@@ -86,24 +86,25 @@ jobs:
 
   ios:
     # iOS builds require Xcode, which is only available on macOS runners.
-    # Pinned to macos-15 (rather than macos-latest) while that label migrates to macos-26
-    # (see https://github.com/actions/runner-images/issues/14167, rollout through
-    # 2026-07-15): macos-latest can currently land on either image at random, each with a
-    # different default Xcode (16.4 vs 26.4.1), and macos-15's *default* Xcode (16.4) doesn't
-    # match what any currently-published net10.0 iOS SDK pack requires (see WorkloadSetVersion
-    # below) - so this job also explicitly selects a non-default Xcode already installed on
-    # the image (see the "Select Xcode" step) to match. See
-    # https://github.com/CommunityToolkit/Datasync/issues/529. Revisit this whole job once we
-    # deliberately upgrade to a newer, Xcode-26-compatible workload set.
-    runs-on: macos-15
+    # Pinned to macos-26 (rather than macos-latest) so the Xcode toolchain doesn't change
+    # underneath us when the macos-latest label moves. macos-26 replaced the previous
+    # (older) macOS image because macOS arm64 jobs on that image repeatedly failed to acquire
+    # a runner due to capacity constraints (see
+    # https://github.com/CommunityToolkit/Datasync/issues/622). macos-26's default Xcode
+    # (26.6) is newer than what the pinned iOS SDK pack requires (see
+    # WorkloadSetVersion below), so this job explicitly selects an older Xcode that is
+    # already installed on the image (see the "Select Xcode" step) to match. See
+    # https://github.com/CommunityToolkit/Datasync/issues/529. Revisit this whole job
+    # once we deliberately drop the workload set pin and move to a newer Xcode.
+    runs-on: macos-26
     env:
       # `dotnet workload install ios` alone always resolves the newest published
       # Microsoft.iOS.Sdk.net10.0_* pack. As of workload set 10.0.108, that's 26.5.10284,
-      # which requires Xcode 26.5 - not installed on macos-15 (even as a non-default Xcode).
+      # which requires Xcode 26.5 (installed on macos-26, but not the Xcode this job selects).
       # Pinning to 10.0.107 (the last set before the iOS/MacCatalyst/macOS/tvOS manifest moved
       # to the 26.4/26.5 pack line; see workload-set history for package id
       # Microsoft.NET.Workloads.10.0.100 on nuget.org) resolves 26.2.10233 instead, which
-      # requires Xcode 26.3 - installed (non-default) on macos-15 as of image 20260629.0276.1
+      # requires Xcode 26.3 - installed (non-default) on macos-26 as of image 20261026.0455.2
       # (see the "Select Xcode" step below). This also keeps other manifests (e.g. Android) at
       # their latest versions. `--version` pins only this job's `dotnet workload install`
       # invocation and the `restore`/`build` steps that follow it in the same runner - it's
@@ -118,7 +119,7 @@ jobs:
         uses: actions/checkout@v7
 
       - name: Select Xcode ${{ env.RequiredXcodeVersion }}
-        # macos-15 defaults to Xcode 16.4, which doesn't satisfy what the pinned iOS
+        # macos-26 defaults to Xcode 26.6, which doesn't match what the pinned iOS
         # workload (see WorkloadSetVersion above) requires. Xcode 26.3 is already installed
         # on the image, just not selected by default - so switch to it explicitly rather
         # than installing anything extra.

.github/workflows/build-samples-todoapp-maui.yml

@@ -57,24 +57,25 @@ jobs:
 
   ios:
     # iOS builds require Xcode, which is only available on macOS runners.
-    # Pinned to macos-15 (rather than macos-latest) while that label migrates to macos-26
-    # (see https://github.com/actions/runner-images/issues/14167, rollout through
-    # 2026-07-15): macos-latest can currently land on either image at random, each with a
-    # different default Xcode (16.4 vs 26.4.1), and macos-15's *default* Xcode (16.4) doesn't
-    # match what any currently-published net10.0 iOS SDK pack requires (see WorkloadSetVersion
-    # below) - so this job also explicitly selects a non-default Xcode already installed on
-    # the image (see the "Select Xcode" step) to match. See
-    # https://github.com/CommunityToolkit/Datasync/issues/529. Revisit this whole job once we
-    # deliberately upgrade to a newer, Xcode-26-compatible workload set.
-    runs-on: macos-15
+    # Pinned to macos-26 (rather than macos-latest) so the Xcode toolchain doesn't change
+    # underneath us when the macos-latest label moves. macos-26 replaced the previous
+    # (older) macOS image because macOS arm64 jobs on that image repeatedly failed to acquire
+    # a runner due to capacity constraints (see
+    # https://github.com/CommunityToolkit/Datasync/issues/622). macos-26's default Xcode
+    # (26.6) is newer than what the pinned iOS SDK pack requires (see
+    # WorkloadSetVersion below), so this job explicitly selects an older Xcode that is
+    # already installed on the image (see the "Select Xcode" step) to match. See
+    # https://github.com/CommunityToolkit/Datasync/issues/529. Revisit this whole job
+    # once we deliberately drop the workload set pin and move to a newer Xcode.
+    runs-on: macos-26
     env:
       # `dotnet workload install maui-ios` alone always resolves the newest published
       # Microsoft.iOS.Sdk.net10.0_* pack. As of workload set 10.0.108, that's 26.5.10284,
-      # which requires Xcode 26.5 - not installed on macos-15 (even as a non-default Xcode).
+      # which requires Xcode 26.5 (installed on macos-26, but not the Xcode this job selects).
       # Pinning to 10.0.107 (the last set before the iOS/MacCatalyst/macOS/tvOS manifest moved
       # to the 26.4/26.5 pack line; see workload-set history for package id
       # Microsoft.NET.Workloads.10.0.100 on nuget.org) resolves 26.2.10233 instead, which
-      # requires Xcode 26.3 - installed (non-default) on macos-15 as of image 20260629.0276.1
+      # requires Xcode 26.3 - installed (non-default) on macos-26 as of image 20261026.0455.2
       # (see the "Select Xcode" step below). This also keeps other manifests (e.g. MAUI,
       # Android) at their latest versions. `--version` pins only this job's
       # `dotnet workload install` invocation and the `restore`/`build` steps that follow it in
@@ -89,7 +90,7 @@ jobs:
         uses: actions/checkout@v7
 
       - name: Select Xcode ${{ env.RequiredXcodeVersion }}
-        # macos-15 defaults to Xcode 16.4, which doesn't satisfy what the pinned iOS
+        # macos-26 defaults to Xcode 26.6, which doesn't match what the pinned iOS
         # workload (see WorkloadSetVersion above) requires. Xcode 26.3 is already installed
         # on the image, just not selected by default - so switch to it explicitly rather
         # than installing anything extra.

.github/workflows/build-samples-todoapp-uno.yml

@@ -58,24 +58,25 @@ jobs:
 
   ios-maccatalyst:
     # iOS and Mac Catalyst builds both require Xcode, which is only available on macOS runners.
-    # Pinned to macos-15 (rather than macos-latest) while that label migrates to macos-26
-    # (see https://github.com/actions/runner-images/issues/14167, rollout through
-    # 2026-07-15): macos-latest can currently land on either image at random, each with a
-    # different default Xcode (16.4 vs 26.4.1), and macos-15's *default* Xcode (16.4) doesn't
-    # match what any currently-published net10.0 iOS SDK pack requires (see WorkloadSetVersion
-    # below) - so this job also explicitly selects a non-default Xcode already installed on
-    # the image (see the "Select Xcode" step) to match. See
+    # Pinned to macos-26 (rather than macos-latest) so the Xcode toolchain doesn't change
+    # underneath us when the macos-latest label moves. macos-26 replaced the previous
+    # (older) macOS image because macOS arm64 jobs on that image repeatedly failed to acquire
+    # a runner due to capacity constraints (see
+    # https://github.com/CommunityToolkit/Datasync/issues/622). macos-26's default Xcode
+    # (26.6) is newer than what the pinned iOS SDK pack requires (see
+    # WorkloadSetVersion below), so this job explicitly selects an older Xcode that is
+    # already installed on the image (see the "Select Xcode" step) to match. See
     # https://github.com/CommunityToolkit/Datasync/issues/529 and #559. Revisit this whole job
-    # once we deliberately upgrade to a newer, Xcode-26-compatible workload set.
-    runs-on: macos-15
+    # once we deliberately drop the workload set pin and move to a newer Xcode.
+    runs-on: macos-26
     env:
       # `dotnet workload install ios maccatalyst` alone always resolves the newest published
       # Microsoft.iOS.Sdk.net10.0_* pack. As of workload set 10.0.108, that's 26.5.10284,
-      # which requires Xcode 26.5 - not installed on macos-15 (even as a non-default Xcode).
+      # which requires Xcode 26.5 (installed on macos-26, but not the Xcode this job selects).
       # Pinning to 10.0.107 (the last set before the iOS/MacCatalyst/macOS/tvOS manifest moved
       # to the 26.4/26.5 pack line; see workload-set history for package id
       # Microsoft.NET.Workloads.10.0.100 on nuget.org) resolves 26.2.10233 instead, which
-      # requires Xcode 26.3 - installed (non-default) on macos-15 as of image 20260629.0276.1
+      # requires Xcode 26.3 - installed (non-default) on macos-26 as of image 20261026.0455.2
       # (see the "Select Xcode" step below). `--version` pins only this job's
       # `dotnet workload install` invocation and the `restore`/`build` steps that follow it in
       # the same runner - it's intentionally not a repo-wide global.json pin, which would
@@ -89,7 +90,7 @@ jobs:
         uses: actions/checkout@v7
 
       - name: Select Xcode ${{ env.RequiredXcodeVersion }}
-        # macos-15 defaults to Xcode 16.4, which doesn't satisfy what the pinned iOS/Mac
+        # macos-26 defaults to Xcode 26.6, which doesn't match what the pinned iOS/Mac
         # Catalyst workload (see WorkloadSetVersion above) requires. Xcode 26.3 is already
         # installed on the image, just not selected by default - so switch to it explicitly
         # rather than installing anything extra.