msbuild

Orchestrate an MSBuild release: create the tracking issue, branch, configure DARC channels and subscriptions, bump version in main, final-brand the release branch, insert into VS, and publish post-GA. Covers the full monthly release lifecycle aligned with VS shipping cadence.

Guide for migrating MSBuild tasks to multithreaded mode support, including compatibility red-team review. Use this when converting tasks to thread-safe versions, implementing IMultiThreadableTask, adding TaskEnvironment support, or auditing migrations for behavioral compatibility.

Guides struct-based COM interop in MSBuild using CsWin32 patterns. Consult when working with ComScope<T>, ComClassFactory, IComIID, IID.Get<T>(), delegate* unmanaged vtables, CoCreateInstance, or manually defining COM interfaces not in Win32 metadata (e.g. WMI IWbemLocator, IWbemServices).

Guides CsWin32 P/Invoke interop in MSBuild. Consult when working with the PInvoke class, Windows.Win32 namespaces, FEATURE_WINDOWSINTEROP, HANDLE/HMODULE/HRESULT types, BufferScope<T>, replacing [DllImport] with CsWin32, or conditioning Windows-only code for source builds.

Make .NET projects compatible with Native AOT and trimming by systematically resolving IL trim/AOT analyzer warnings. USE FOR: making projects AOT-compatible, fixing trimming warnings, resolving IL warnings (IL2026, IL2070, IL2067, IL2072, IL3050), adding DynamicallyAccessedMembers annotations, enabling IsAotCompatible. DO NOT USE FOR: publishing native AOT binaries, optimizing binary size, replacing reflection-heavy libraries with alternatives. INVOKES: no tools — pure knowledge skill.

Guide for running MSBuild unit tests efficiently. Use when running, scoping, filtering, or speeding up unit tests in this repository, or when finalizing a change with a heavier validation pass. Covers xUnit v3 + Microsoft.Testing.Platform (MTP) specifics and which `dotnet test` flags do and don't apply.

GitHub issue and project-board management for the dotnet/msbuild repo. Use when asked to file/triage/update issues, post comments, amend issue bodies, move sprints, bulk-update project board fields, or audit items by sprint/status/assignee.

Guides assessment of backward compatibility for MSBuild changes. Consult when modifying behavior, adding warnings or errors, changing defaults, altering target ordering, removing or deprecating features, deciding whether a change needs a ChangeWave, reviewing blast radius of behavioral changes, or when a PR introduces user-visible output differences.

Guides authoring of MSBuild errors, warnings, and diagnostic messages. Consult when adding new MSBxxxx codes, writing or modifying user-facing diagnostic text, deciding between error/warning/message severity, working with Strings.resx resource files, formatting paths in error output, or evaluating whether a new warning could break WarnAsError builds.

Manage MSBuild Change Waves: create new waves, condition features behind opt-out flags, write tests for wave-gated features, document change waves in ChangeWaves.md, and retire expired waves. Use when adding changes that need an opt-out or rotating out old change waves. Changes that introduce a user-visible behavior change should consider whether to use a changewave.

Guides work on the SDK-MSBuild integration boundary. Consult when authoring or modifying SDK targets, working on dotnet CLI to MSBuild invocation, handling project-reference protocol, coordinating cross-repo changes with dotnet/sdk, debugging property resolution or import ordering, working on restore/build/publish/pack target chains, or dealing with Directory.Build.props/targets interaction.

Guides changes to MSBuild binary log infrastructure. Consult when modifying BinaryLogger or BinaryLogReplayEventSource, adding new BuildEventArgs types, changing event serialization/deserialization, modifying ProjectImportsCollector, adjusting message importance levels, or making changes that affect .binlog content. Also applies when verifying that behavioral changes are properly reflected in binary log output.

Guides performance optimization for MSBuild engine code. Consult when working on hot paths in evaluation or execution, reducing allocations, choosing collection types, handling strings efficiently, modifying Expander.cs or Evaluator.cs, using Span<T>/stackalloc, caching values, or profiling build performance. Also applies when reviewing PRs for performance regression.

Reviews MSBuild code changes using a 24-dimension methodology. Activates for code review, PR review, pull request analysis, design review, architecture review, code quality assessment, or style check of MSBuild code. Covers backwards compatibility, ChangeWave discipline, performance, allocation awareness, test coverage, error message quality, logging, string comparison, API surface, target authoring, cross-platform correctness, code simplification, concurrency, naming, SDK integration, evaluation model integrity, correctness, dependency management, security, and build infrastructure.

Deploy locally-built MSBuild binaries into a Visual Studio installation for testing and debugging. Use when you need VS itself to use your local MSBuild changes, or when debugging MSBuild as invoked by VS.

Review and merge open bot PRs: dependency updates from dotnet-maestro, codeflow from dotnet/dotnet, and OneLoc localization PRs. Produces a clickable dashboard with CI status, review state, and suspicious file flags. Use when you want to triage all open bot PRs in one pass.

Check health of MSBuild CI pipelines, VS repo PR insertion statuses, and VMR codeflow PRs. Use when asked about pipeline health, build failures, infrastructure issues, CI status, insertion PR status, VMR codeflow status, or for periodic health monitoring.

Guide for testing bug reproductions against locally-built MSBuild. Use this when you have a repro project and want to verify a fix works before submitting a PR.