From 6c1a99cde9cb72a0c58db9da852c4da29e876c55 Mon Sep 17 00:00:00 2001
From: Milos Kotlar <kotlarmilos@gmail.com>
Date: Tue, 7 Jul 2026 11:39:42 +0200
Subject: [PATCH 1/2] Fix NETSDK1242 build breaks on NativeAOT and Mono mobile
 smoke test

The .NET 11 SDK 11.0.100-preview.6.26352.110 added check NETSDK1242, which
errors when a project targets a mobile platform (ios/tvos/maccatalyst/android)
with the Mono runtime. The CoreCLR mobile legs already pass /p:UseMonoRuntime=false
so the check never fires for them, but the NativeAOT legs do not, so the mobile
inner target frameworks of the multi-targeted libs.tests projects default to Mono
during restore and fail the build.

Force UseMonoRuntime off whenever UseNativeAOTRuntime is set, since NativeAOT is
CoreCLR-based and never uses Mono. Separately, set the SDK opt-out on the single
Mono iOS simulator smoke test, which intentionally builds the product with Mono
and therefore cannot turn UseMonoRuntime off.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
---
 Directory.Build.props                                          | 3 +++
 .../runtime-extra-platforms-ioslikesimulator.yml               | 2 +-
 2 files changed, 4 insertions(+), 1 deletion(-)

diff --git a/Directory.Build.props b/Directory.Build.props
index 97e2d5ecacff0f..6686c890574a34 100644
--- a/Directory.Build.props
+++ b/Directory.Build.props
@@ -236,6 +236,9 @@
     <CoreLibProject Condition="'$(UseNativeAotCoreLib)' == 'true'">$([MSBuild]::NormalizePath('$(CoreClrProjectRoot)', 'nativeaot', 'System.Private.CoreLib', 'src', 'System.Private.CoreLib.csproj'))</CoreLibProject>
     <UriProject>$([MSBuild]::NormalizePath('$(LibrariesProjectRoot)', 'System.Private.Uri', 'src', 'System.Private.Uri.csproj'))</UriProject>
 
+    <!-- NativeAOT is CoreCLR-based and never uses the Mono runtime. Force UseMonoRuntime off so the mobile inner target frameworks of
+         multi-targeted libraries do not default to Mono during restore, which would fail the .NET 11 SDK's mobile check (NETSDK1242). -->
+    <UseMonoRuntime Condition="'$(UseMonoRuntime)' == '' and '$(UseNativeAOTRuntime)' == 'true'">false</UseMonoRuntime>
     <!-- this property is used by the SDK to pull in mono-based runtime packs -->
     <UseMonoRuntime Condition="'$(UseMonoRuntime)' == '' and '$(RuntimeFlavor)' == 'Mono'">true</UseMonoRuntime>
     <UseMonoRuntime Condition="'$(UseMonoRuntime)' == 'true' and '$(TargetsMobile)' != 'true' and (
diff --git a/eng/pipelines/extra-platforms/runtime-extra-platforms-ioslikesimulator.yml b/eng/pipelines/extra-platforms/runtime-extra-platforms-ioslikesimulator.yml
index b46adbe7a77350..acb45464e13666 100644
--- a/eng/pipelines/extra-platforms/runtime-extra-platforms-ioslikesimulator.yml
+++ b/eng/pipelines/extra-platforms/runtime-extra-platforms-ioslikesimulator.yml
@@ -33,7 +33,7 @@ jobs:
     jobParameters:
       testGroup: innerloop
       nameSuffix: AllSubsets_Mono
-      buildArgs: -s mono+libs+host+packs+libs.tests -c $(_BuildConfig) /p:ArchiveTests=true /p:RunSmokeTestsOnly=true /p:RunAOTCompilation=true /p:MonoForceInterpreter=true
+      buildArgs: -s mono+libs+host+packs+libs.tests -c $(_BuildConfig) /p:ArchiveTests=true /p:RunSmokeTestsOnly=true /p:RunAOTCompilation=true /p:MonoForceInterpreter=true /p:_DisableCheckForUnsupportedMonoMobileRuntime=true
       timeoutInMinutes: 240
       # extra steps, run tests
       postBuildSteps:

From 79c1dbe921345058779d8d2b307bd1f668f45ca1 Mon Sep 17 00:00:00 2001
From: Milos Kotlar <kotlarmilos@gmail.com>
Date: Tue, 7 Jul 2026 12:04:32 +0200
Subject: [PATCH 2/2] Drop explanatory comment on NativeAOT UseMonoRuntime rule

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
---
 Directory.Build.props | 4 +---
 1 file changed, 1 insertion(+), 3 deletions(-)

diff --git a/Directory.Build.props b/Directory.Build.props
index 6686c890574a34..c0b055b05dc93d 100644
--- a/Directory.Build.props
+++ b/Directory.Build.props
@@ -236,10 +236,8 @@
     <CoreLibProject Condition="'$(UseNativeAotCoreLib)' == 'true'">$([MSBuild]::NormalizePath('$(CoreClrProjectRoot)', 'nativeaot', 'System.Private.CoreLib', 'src', 'System.Private.CoreLib.csproj'))</CoreLibProject>
     <UriProject>$([MSBuild]::NormalizePath('$(LibrariesProjectRoot)', 'System.Private.Uri', 'src', 'System.Private.Uri.csproj'))</UriProject>
 
-    <!-- NativeAOT is CoreCLR-based and never uses the Mono runtime. Force UseMonoRuntime off so the mobile inner target frameworks of
-         multi-targeted libraries do not default to Mono during restore, which would fail the .NET 11 SDK's mobile check (NETSDK1242). -->
-    <UseMonoRuntime Condition="'$(UseMonoRuntime)' == '' and '$(UseNativeAOTRuntime)' == 'true'">false</UseMonoRuntime>
     <!-- this property is used by the SDK to pull in mono-based runtime packs -->
+    <UseMonoRuntime Condition="'$(UseMonoRuntime)' == '' and '$(UseNativeAOTRuntime)' == 'true'">false</UseMonoRuntime>
     <UseMonoRuntime Condition="'$(UseMonoRuntime)' == '' and '$(RuntimeFlavor)' == 'Mono'">true</UseMonoRuntime>
     <UseMonoRuntime Condition="'$(UseMonoRuntime)' == 'true' and '$(TargetsMobile)' != 'true' and (
         $(TargetFramework.EndsWith('-android')) or $(TargetFramework.EndsWith('-ios')) or