diff --git a/.github/workflows/build-samples-todoapp-avalonia.yml b/.github/workflows/build-samples-todoapp-avalonia.yml
index a5e5a08..2312b59 100644
--- a/.github/workflows/build-samples-todoapp-avalonia.yml
+++ b/.github/workflows/build-samples-todoapp-avalonia.yml
@@ -76,18 +76,51 @@ jobs:
 
   ios:
     # iOS builds require Xcode, which is only available on macOS runners.
-    runs-on: macos-latest
+    # 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
+    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).
+      # 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
+      # (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
+      # intentionally not a repo-wide global.json pin, which would force every `dotnet`
+      # invocation in the whole repo (including samples with no workload dependency at all)
+      # to require this exact workload version to already be installed, breaking them on a
+      # fresh runner.
+      WorkloadSetVersion: '10.0.107'
+      RequiredXcodeVersion: '26.3'
     steps:
       - name: Checkout Repository
         uses: actions/checkout@v7
 
+      - name: Select Xcode ${{ env.RequiredXcodeVersion }}
+        # macos-15 defaults to Xcode 16.4, which doesn't satisfy what the pinned iOS
+        # workload (see WorkloadSetVersion above) requires. Xcode 26.3 is already installed
+        # on the image, just not selected by default - so switch to it explicitly rather
+        # than installing anything extra.
+        run: sudo xcode-select -s /Applications/Xcode_${{ env.RequiredXcodeVersion }}.app
+
       - name: Setup .NET
         uses: actions/setup-dotnet@v5
         with:
           dotnet-version: ${{ env.DOTNET_VERSION }}
 
       - name: Install iOS workload
-        run: dotnet workload install ios
+        run: dotnet workload install ios --version ${{ env.WorkloadSetVersion }}
 
       - name: Restore iOS project
         run: dotnet restore ${{ env.iOSProjectFile }}
diff --git a/.github/workflows/build-samples-todoapp-maui.yml b/.github/workflows/build-samples-todoapp-maui.yml
index 5f03eda..0f977cb 100644
--- a/.github/workflows/build-samples-todoapp-maui.yml
+++ b/.github/workflows/build-samples-todoapp-maui.yml
@@ -48,18 +48,51 @@ jobs:
 
   ios:
     # iOS builds require Xcode, which is only available on macOS runners.
-    runs-on: macos-latest
+    # 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
+    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).
+      # 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
+      # (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
+      # the same runner - it's intentionally not a repo-wide global.json pin, which would
+      # force every `dotnet` invocation in the whole repo (including samples with no workload
+      # dependency at all) to require this exact workload version to already be installed,
+      # breaking them on a fresh runner.
+      WorkloadSetVersion: '10.0.107'
+      RequiredXcodeVersion: '26.3'
     steps:
       - name: Checkout Repository
         uses: actions/checkout@v7
 
+      - name: Select Xcode ${{ env.RequiredXcodeVersion }}
+        # macos-15 defaults to Xcode 16.4, which doesn't satisfy what the pinned iOS
+        # workload (see WorkloadSetVersion above) requires. Xcode 26.3 is already installed
+        # on the image, just not selected by default - so switch to it explicitly rather
+        # than installing anything extra.
+        run: sudo xcode-select -s /Applications/Xcode_${{ env.RequiredXcodeVersion }}.app
+
       - name: Setup .NET
         uses: actions/setup-dotnet@v5
         with:
           dotnet-version: ${{ env.DOTNET_VERSION }}
 
       - name: Install MAUI iOS workload
-        run: dotnet workload install maui-ios
+        run: dotnet workload install maui-ios --version ${{ env.WorkloadSetVersion }}
 
       - name: Restore MAUI project (iOS TFM only)
         run: dotnet restore ${{ env.MauiProjectFile }} -p:TargetFramework=${{ env.iOSTargetFramework }}