[rolfbjarne]

Summary

• add a page-level boundary for Mono-specific build properties in .NET
  10 and earlier versus CoreCLR in .NET 11
• document NETSDK1242 for UseMonoRuntime=true on .NET 11 iOS, tvOS,
  and Mac Catalyst while keeping the existing macOS CoreCLR-only workload
  error distinct
• scope the MAUI UseInterpreter=true Debug behavior to .NET 10 and
  earlier and clarify that MtouchInterpreter and UseInterpreter
  configure the Mono interpreter, not the CoreCLR interpreter
• preserve the existing warnings from [msbuild] Detect Mono-only build properties when not using the Mono runtime #26042 and leave MtouchLink and
  TrimMode unchanged

Validation

• git diff --check
• local Markdown link and anchor checks
• exact text/count assertions for the runtime boundary and both MAUI
  notes
• unchanged-section assertions for EnableSGenConc,
  MonoUseCompressedInterfaceBitmap, MtouchEnableSGenConc,
  MtouchUseLlvm, MtouchLink, and TrimMode
• single-file scope, prohibited-heading, collective-wording, and
  trimming-setting assertions
• cited the focused existing ProjectTest.MonoOnlyPropertyWarning and
  ProjectTest.MonoOnlyPropertyError coverage; these macOS workload tests
  were not run from the Windows worktree

Release evidence

Current main at 03e37082495026ce93f511a01fc07ef7e2170279 contains
the #26042 warning behavior and #26468
(c7c6bba288295c08a6d125338f5bf5849d3f5bbc). The available
release/11.0.1xx-rc.1 branch at
4d35fc6aedc02ef4bb9ecdae170cb8132be0a5d6 contains #26042 but does not
contain #26468, and no final .NET 11 release branch is currently
available. This PR follows the approved DOC-018 assumption that #26468
ships in final .NET 11; that ancestry must be rechecked before merge.

The .NET SDK gate currently raises NETSDK1242 for .NET 11 and later
iOS, tvOS, and Mac Catalyst projects with UseMonoRuntime=true; macOS
is excluded from that gate and retains the workload's Only CoreCLR is supported on macOS error. The .NET MAUI net11.0,
release/11.0.1xx-rc1, and release/11.0.1xx-rc2 targets set
UseInterpreter only when UseMonoRuntime=true.

Coordination

Synchronization to dotnet/docs-mobile is intentionally deferred to the
coordinated DOC-018 public documentation PR.

---

Co-authored-by: Copilot App 223556219+Copilot@users.noreply.github.com
Co-authored-by: Copilot Autofix powered by AI 175728472+Copilot@users.noreply.github.com

Backport of #26634.

[Copilot]

Copilot review overview

🟢 Approval recommended

Documentation-only changes have no blocking issues identified.

Review effort: Lite
Findings: None

What changed in this PR

Documentation-only update clarifying Mono/CoreCLR build properties and .NET 11 behavior.

Changes:

• Documents runtime boundaries and NETSDK1242.
• Clarifies MAUI interpreter behavior.
• Updates Mono-specific trimming guidance.

File	Summary
docs/​building-apps/​build-properties.md	Documents runtime-specific properties and MAUI defaults.