Source Build Outer Loop failing on main: NETSDK1242 building mobile targets with Mono on .NET 11

[mthalman]

Summary

The Source Build Outer Loop pipeline (1525) is failing on main because the source-built SDK attempts to build mobile (android/ios/tvos/maccatalyst) projects with the Mono runtime, which is no longer supported in .NET 11.

Failing build

• Pipeline: Source Build Outer Loop (id 1525)
• Build: 3006776
• Branch: refs/heads/main
• Failing leg: SB_CentOSStream10_Mono_Offline_CurrentSourceBuiltSdk_x64
• Failing task: Build (centOSStreamContainer)

Error

NETSDK1242: Building android/ios/tvos/maccatalyst projects with the Mono runtime is not supported in .NET 11.0 and later. Use the CoreCLR runtime or target .NET 10.0.

Root cause

The runtime restore in the Mono offline leg pulls in .NET 11 mobile targets while using the Mono runtime. As of .NET 11, mobile workload projects can no longer be built against the Mono runtime.

Suggested fix

Update the source-build / runtime configuration so the Mono leg does not build mobile targets under .NET 11 — either switch those targets to the CoreCLR runtime or target .NET 10.0 for the affected projects.

Category

Configuration

[github-actions]

🏷️ Source-build triage pass — 2026-06-24 16:48 UTC

📋 Classification

Field	Value
Area	area-infra
Additional area(s)	area-build (configuration of build targets)
Kind	bug
Severity	S2 — Blocks the Mono offline CI leg on main branch; workaround is to disable the leg or revert to .NET 10 mobile targets
Affected version(s)	.NET 11 (main branch)
Repro	yes-minimal — Build link and error message provided; clear failure in CI pipeline

🚦 Priority

• Blocking: blocking-clean-ci — Prevents main branch CI from being green; affects the Mono offline leg
• Urgency: 🔴 current release — no milestone

  Blocks main branch CI; needs immediate fix to restore clean builds on the primary development branch

👥 Routing

• Team: @dotnet/source-build
• Possible SME(s): mthalman, ellahathaway
  • mthalman — Assigned to this issue; active on 15+ ops-monitor and area-build issues including Enable AOT-compiled SDK tools when the SDK is built via source-build #5567, SdkContentTests.CompareMsftToSbTemplatePackageVersions fails: 11.0 MSTest templates aren't valid standalone XML #5565, Microsoft.Extensions.ObjectPool version differences between Microsoft build and source build #5513, SolutionPersistence product and product version numbers report wrong version #5512
  • ellahathaway — Active on 20+ build, testing, and infra issues including Internal 9.0 VMR Sync is Failing #5600, release/8.0.1xx branch is failing to build with aspnetcore patch errors #5597, Cloaked SBE file in release/8.0.1xx and release/9.0.1xx #5595, [release/9.0.1xx] New aspnetcore binary #5594, Follow up: remove aspnetcore public feed setup into smoke test online.NuGet.Config #5593

🔗 Cross-references

• Recommended labels: add area-infra, add area-build, add blocking-clean-ci
• Related issues: none found
• Possible duplicate of: none

✅ Assessment

• Confidence: high
• Needs human?: no

---

Restricted mode — no labels or milestone applied. A maintainer should manually apply any accepted labels and milestone.

Note

🔒 Integrity filter blocked 22 items

The following items were blocked because they don't meet the GitHub integrity level.

• #5574 search_issues: has lower integrity than agent requires. The agent cannot read data with integrity below "approved".
• #5562 search_issues: has lower integrity than agent requires. The agent cannot read data with integrity below "approved".
• #5556 search_issues: has lower integrity than agent requires. The agent cannot read data with integrity below "approved".
• #5555 search_issues: has lower integrity than agent requires. The agent cannot read data with integrity below "approved".
• #5552 search_issues: has lower integrity than agent requires. The agent cannot read data with integrity below "approved".
• #5547 search_issues: has lower integrity than agent requires. The agent cannot read data with integrity below "approved".
• #5544 search_issues: has lower integrity than agent requires. The agent cannot read data with integrity below "approved".
• #5543 search_issues: has lower integrity than agent requires. The agent cannot read data with integrity below "approved".
• #5532 search_issues: has lower integrity than agent requires. The agent cannot read data with integrity below "approved".
• #5525 search_issues: has lower integrity than agent requires. The agent cannot read data with integrity below "approved".
• #5514 search_issues: has lower integrity than agent requires. The agent cannot read data with integrity below "approved".
• #4590 search_issues: has lower integrity than agent requires. The agent cannot read data with integrity below "approved".
• #1689 search_issues: has lower integrity than agent requires. The agent cannot read data with integrity below "approved".
• #1638 search_issues: has lower integrity than agent requires. The agent cannot read data with integrity below "approved".
• #1627 search_issues: has lower integrity than agent requires. The agent cannot read data with integrity below "approved".
• #1610 search_issues: has lower integrity than agent requires. The agent cannot read data with integrity below "approved".
• ... and 6 more items

To allow these resources, lower min-integrity in your GitHub frontmatter:

tools:
  github:
    min-integrity: approved  # merged | approved | unapproved | none

Generated by Triage · ● 2.7M · ◷

[mthalman]

Runtime build logs:

build-logs.zip

[mthalman]

[Triage] This was temporarily mitigated by dotnet/dotnet#7359. Need to determine what the long-term resolution will be.