dotnet

Generate wrapper interfaces and DI registration for hard-to-test static dependencies in C#, when the abstraction does NOT exist yet. Produces IFileSystem, IEnvironmentProvider, IConsole, IProcessRunner wrappers, or guides first-time adoption of TimeProvider and IHttpClientFactory and registering them in DI. USE FOR: generate wrapper for static, create IFileSystem wrapper, wrap DateTime.Now, make static testable, make class testable, create abstraction for File.*, generate DI registration, set up/adopt TimeProvider when it is not registered yet, IHttpClientFactory setup, testability wrapper, create the right abstraction to mock, what abstraction for Environment, how to make statics injectable, adopt System.IO.Abstractions. DO NOT USE FOR: detecting statics (use detect-static-dependencies), migrating call sites or replacing existing DateTime.*/File.* usages once the wrapper is created or already registered in DI (use migrate-static-to-wrapper), general interface design.

Replace existing static dependency call sites with wrapper or built-in abstraction calls when the abstraction already exists or is already registered in DI. Codemod-style bulk replacement of DateTime.Now/UtcNow to TimeProvider, File.ReadAllText to IFileSystem, and similar, across a bounded scope (file, project, or namespace). Adds the constructor injection parameter to affected classes. USE FOR: replace all DateTime.UtcNow/DateTime.Now calls with TimeProvider and add the constructor parameter, TimeProvider already registered in DI so migrate the call sites, migrate static calls to wrapper, bulk replace File.* with IFileSystem, codemod static to injectable, add constructor injection for an existing dependency, scoped migration of statics, migrate statics in only certain scoped files. DO NOT USE FOR: detecting statics (use detect-static-dependencies), creating the wrapper or registering it when it does not exist yet (use generate-testability-wrappers), migrating between test frameworks.

Write, create, modernize, or fix comprehensive MSTest unit tests with MSTest 3.x/4.x APIs. USE FOR: write, create, review, or modernize MSTest tests and assertions, better MSTest assertion than Assert.IsTrue, replace hard cast with IsInstanceOfType, MSTest assertion APIs (Contains, ContainsSingle, HasCount, IsEmpty, IsNotEmpty, DoesNotContain, AreSame, IsNull, StartsWith, EndsWith, MatchesRegex, IsGreaterThan, IsLessThan, IsInRange), swapped/reversed Assert.AreEqual args (Expected/Actual backwards), replace ExpectedException with Assert.Throws, data-driven (DataRow, DynamicData, ValueTuples), lifecycle (TestInitialize, TestCleanup, TestContext), async and cancellation tests, conditional execution/retry/cleanup (OSCondition, Retry), parallelization (Parallelize/DoNotParallelize), MSTest.Sdk setup, MSTESTxxxx analyzer fixes. DO NOT USE FOR: test quality audits (use test-anti-patterns), running tests (use run-tests), MSTest version migration (use migrate-mstest skills), xUnit/NUnit/TUnit, or non-.NET languages.

Analyzes the variety and depth of assertions across test suites in any language. Use when the user asks to evaluate assertion quality, find shallow tests, identify assertion-free tests (no assertions or only trivial ones like Assert.IsNotNull / toBeTruthy()), flag self-referential or tautological assertions, measure assertion diversity, or audit whether tests verify different facets of behavior. Polyglot: .NET, Python, TS/JS, Java, Go, Ruby, Rust, Swift, Kotlin, PowerShell, C++. DO NOT USE FOR: writing new tests (use code-testing-agent / writing-mstest-tests), mutation reasoning about whether tests would catch a bug (use test-gap-analysis), or a general severity-ranked anti-pattern audit (use test-anti-patterns), fixing or rewriting assertions, or writing, fixing, or modernizing MSTest tests, assertions, or attributes (use writing-mstest-tests).

Run, filter, or troubleshoot .NET tests with `dotnet test`. USE FOR: running all tests in a project or solution; running only a subset (a specific test class, category, or trait) via filters; running a single target framework in a multi-TFM project (`--framework`); producing TRX reports; collecting crash or hang dumps; diagnosing why `dotnet test` fails or uses the wrong argument syntax. Detects the test platform (VSTest vs Microsoft.Testing.Platform) and framework (MSTest/xUnit/NUnit/TUnit), then picks the matching command: the `--` separator on .NET SDK 8/9 vs 10+, the right filter flag (--filter, --filter-class, --filter-trait, --filter-query, --treenode-filter), and TRX/blame flags. DO NOT USE FOR: writing test code (use code-testing-agent), iterating on failing tests without rebuilding (use mtp-hot-reload), CI/CD config, or debugging test logic.

Parse-only static analysis that pairs source files with the tests referencing them and emits JSON listing untested files ordered by API surface, each with a suggested_test_path. Roslyn engine for C#/.NET (namespace-aware), tree-sitter engine for polyglot repos (Python, TS/JS, Go, Java, Rust, Ruby). USE FOR: where to write tests next, which files have no tests, find untested code, build a source-to-test pairing map, prioritized test-gap worklist. DO NOT USE FOR: line/branch coverage or CRAP risk (use coverage-analysis); whether existing tests are strong (use test-gap-analysis or assertion-quality).

Detects duplicate boilerplate, copy-paste tests, and structural maintainability issues across .NET test suites. Use when the user asks to reduce repetition, consolidate similar test methods, convert copy-paste tests to data-driven parameterized tests, suggest a better test structure, or identify refactoring opportunities. Identifies repeated construction, assertion patterns, copy-paste methods convertible to DataRow/Theory/TestCase, redundant setup/teardown, and shared infrastructure. Produces an analysis report with concrete before/after suggestions. Works with MSTest, xUnit, NUnit, and TUnit. DO NOT USE FOR: writing new tests (use writing-mstest-tests), reviewing test quality or anti-patterns (use test-anti-patterns), or deep mock auditing (use exp-mock-usage-analysis).

Provides file paths to language-specific reference files for the test ANALYSIS skills (assertion-quality, test-anti-patterns, test-gap-analysis, test-smell-detection, test-tagging). Call this skill to discover available extension files (e.g., dotnet.md for .NET/MSTest/xUnit/NUnit/TUnit, python.md for pytest/unittest, typescript.md for Jest/Vitest/Mocha, java.md for JUnit/TestNG, etc.). Do not use directly — invoked by the test-quality-auditor agent and polyglot analysis skills that need framework-specific lookup tables (test markers, assertion APIs, skip annotations, sleep patterns, mystery guest indicators, integration markers, setup/teardown, tag-support capability).

Make .NET MAUI apps accessible with semantic properties, screen reader labels/hints, heading levels, focus, announcements, AutomationProperties, touch targets, and platform checks. USE FOR: accessibility audits, WCAG UI fixes, TalkBack/VoiceOver/Narrator behavior, SemanticProperties.Description/Hint/HeadingLevel, SemanticScreenReader.Announce, SetSemanticFocus, avoiding redundant Label metadata, hiding decorative content with IsInAccessibleTree=false, and CollectionView row semantics. DO NOT USE FOR: general layout, UI automation only, or performance tuning.

Use `Microsoft.Maui.AI.Attributes` to source-generate `Microsoft.Extensions.AI` tools for MAUI apps. USE FOR: `ExportAIFunction`, `AIToolSource`, `AIToolContext`, `Default.Tools`, DI-bound parameters, chat-session scopes, AOT-safe tools, and `IChatClient.UseFunctionInvocation`. DO NOT USE FOR: Essentials.AI chat or embeddings, native bindings, or theory.

Design .NET MAUI architecture around DI, MVVM, compiled bindings, Shell navigation, route registration, query parameters, and testable services. USE FOR: MauiProgram service registration, page/ViewModel wiring, Shell GoToAsync, Routing.RegisterRoute, trim-safe IQueryAttributable vs [QueryProperty] for full trimming/NativeAOT, Uri.EscapeDataString/UnescapeDataString query handling, x:DataType on pages/DataTemplates, AddTransient page lifetimes, and avoiding BuildServiceProvider/service locator patterns. DO NOT USE FOR: project layout, API currency, or runtime debug tools.

Configure .NET MAUI app icons, splash screens, images, fonts, bundled files, app/window lifecycle, background/resume state, and platform asset/lifecycle settings. USE FOR: MauiIcon, MauiSplashScreen, MauiImage, MauiFont, MauiAsset, Resources/Images, Resources/Fonts, Resources/Raw seed JSON, FileSystem.OpenAppPackageFileAsync, Window Created/Stopped/Resumed/Destroying, ConfigureLifecycleEvents, state restore, Xamarin drawable/UIAppFonts migration, and platform asset overrides. DO NOT USE FOR: localization/theme resources, device permissions, or broad project structure.

Connect MAUI apps to Aspire-hosted APIs. USE FOR: `AddServiceDiscovery`, typed `HttpClient`, `https+http://apiservice`, missing AppHost config on devices, Android emulator `10.0.2.2`, iOS simulator `localhost`, physical-device LAN/dev-tunnel fallbacks, dev certs, Bearer handlers, debug-only cleartext. DO NOT USE FOR: offline caching, OAuth callbacks, or server-side Aspire.

Implement .NET MAUI authentication and secure storage flows with WebAuthenticator, MSAL.NET, platform callback URIs, token caches, brokers, SecureStorage, logout cleanup, and Blazor Hybrid auth handoff. USE FOR: login/logout, OAuth/OIDC redirects, Entra ID, CallbackUrl, WebAuthenticatorCallbackActivity, Android intent filters, CFBundleURLTypes, MSAL redirect URI/BrokerRedirectUri, AcquireTokenSilent, RemoveAsync/GetAccountsAsync token cache cleanup, secure token storage, and native-to-Blazor auth state. DO NOT USE FOR: architecture, API retries/offline behavior, or UI debugging.

Build and debug .NET MAUI Blazor Hybrid features with BlazorWebView, HybridWebView, Razor components, static assets, JS/.NET interop, trimming/NativeAOT concerns, and DevFlow CDP route inspection. USE FOR: MAUI apps hosting Razor UI, embedded HTML/JS, choosing BlazorWebView vs HybridWebView, AddMauiBlazorWebView, RootComponent, SendRawMessage/RawMessageReceived, JSON DTO contracts, JsonSerializerContext, wwwroot assets, hybrid auth/data handoff, stale DOM/Razor route debugging, and maui_cdp_webviews/source/evaluate/screenshot/logs. DO NOT USE FOR: pure XAML UI or browser-only apps.

Apply advanced MAUI control guidance. USE FOR: `CollectionView` incremental loading, `RemainingItemsThreshold`, `EmptyView`, `AutomationId`, avoiding `ScrollView` wrappers, `SafeAreaEdges` on .NET 10, `GraphicsView`/`IDrawable`/`Invalidate` hot-path performance, gestures, animations. DO NOT USE FOR: general layout, full accessibility audits, profiling, or handlers.

MAUI-specific dependency flow rules, channel conventions, and feed lookup workflows. Use when asked about darc, BAR, Maestro, feeds for .NET MAUI, build promotion, asset lookup, channel mappings, or dependency flow for dotnet/maui. Wraps the maestro-cli skill and maestro MCP tools with MAUI-specific guardrails.

Assesses ship-readiness for .NET MAUI release branches — Servicing Releases (SR) and Previews. Surveys CI pipelines, computes what's actually NEW in the branch (commits + source PRs with revert detection), and cross-references open `regressed-in-*` issues against branch contents to identify port candidates, rejected backports, and unresolved regressions. Supports both in-flight and pre-cut (candidate) modes for SR and Preview branches.

Investigate CI failures for dotnet/maui PRs and the nightly/official signed build — build errors, Helix test logs, and binlog analysis. Use when asked about failing checks, CI status, test failures, 'why is CI red', 'build failed', 'what's failing on PR', 'is this PR ready to merge', Helix failures, device test failures, or 'nightly is broken', 'nightly build failing', 'inflight feed stale', 'dogfood feed stopped updating', 'official build failed'.

Build and run .NET MAUI device tests locally with category filtering. Supports iOS, MacCatalyst, Android on macOS; Android, Windows on Windows. Use TestFilter to run specific test categories.

Verifies tests catch the bug. Auto-detects test type (UI tests, device tests, unit tests) and dispatches to the appropriate runner. Supports two modes - verify failure only (test creation) or full verification (test + fix validation).

Classifies PR CI/test failures as likely PR-caused or unrelated, compares against base-branch baseline, and emits an overall merge-readiness verdict. Uses gathered GitHub/AzDO/Helix context and the shared MAUI CI facts.

Labels issues and pull requests in the dotnet/maui repository with `area-*` and `platform/*` labels ONLY, based on technical content and platform-file conventions. Used by the gh-aw agentic-labeler workflow and available for batch evaluation and interactive Copilot CLI usage.

Deep code review of PR changes for correctness, safety, and MAUI conventions. Uses independence-first assessment (code before narrative) and delegates to the maui-expert-reviewer agent for per-dimension sub-agent evaluation. Triggers on: "review code for PR", "code review PR", "analyze code changes", "check PR code quality". Do NOT use for: summarizing PRs, describing what changed, general PR questions, running tests, or fixing code.

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.

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.

Implementation details for EF Core test infrastructure. Use when changing test fixtures, SQL baseline assertions, test helpers, the test class hierarchy, or when adding new tests.

Implementation details for the EF Core Azure Cosmos DB provider. Use when changing Cosmos-specific code.

Run ApiChief in the EF Core repo to emit baselines, summaries, deltas, review files, or breaking-change checks. Use when refreshing `*.baseline.json`, preparing API review artifacts, or validating API changes.

Create custom GitHub Copilot agents. Use when asked to create, scaffold, or configure a custom agent, declarative agent, or @-invokable chat participant for GitHub Copilot.

Create new Agent Skills for GitHub Copilot. Use when asked to create, scaffold, or add a skill. Generates SKILL.md with frontmatter, directory structure, and optional resources.

Implementation details for EF Core migrations. Use when changing MigrationsSqlGenerator, model diffing, migration operations, HistoryRepository, the Migrator or related classes.

Implementation details for EF Core LINQ query translation, SQL generation, and bulk operations (ExecuteUpdate/ExecuteDelete). Use when changing expression visitors, SqlExpressions, QuerySqlGenerator, ShaperProcessingExpressionVisitor, UpdateExpression, DeleteExpression, or related classes.

Create EF Core PRs targeting servicing release branches (release/*). Use when working on a PR that targets a release branch, backporting a fix from main, or when the user mentions servicing, patch, or release branch.

Monitors .NET runtime CI test pipelines on Azure DevOps. Use this skill when asked to monitor CI pipeline test results, triage CI test failures across ADO pipelines, or generate CI test monitoring reports.

Review code changes in dotnet/runtime for correctness, performance, and consistency with project conventions. Use when reviewing PRs or code changes.

Add a new API to the JIT-VM (aka JIT-EE) interface in the codebase.

Create prototype-backed API proposals for dotnet/runtime. Use when asked to draft an API proposal, write an api-suggestion issue, refine a vague API idea into a complete proposal, or improve a proposal marked api-needs-work. Covers the full pipeline from research through prototyping, ref source generation, and publishing. DO NOT USE FOR bug fixes, code review, performance benchmarking, or internal API changes that don't affect public surface area.

Generate and run ad hoc performance benchmarks to validate code changes. Use this when asked to benchmark, profile, or validate the performance impact of a code change in dotnet/runtime.

Analyze a dotnet/runtime PR's CI failures, skip failures already known to Build Analysis, find matching Known Build Errors, and create or draft new KBEs for the remaining failures. Supports dry-run output to local markdown files instead of creating GitHub issues.

Triage Fuzzlyn CI runs.

Triage a dotnet/runtime GitHub issue with duplicate search, label check, reproduction, and ecosystem research, then recommend KEEP/CLOSE/NEEDS INFO. Use when asked to triage, evaluate, assess, or check a specific GitHub issue. Also use when asked "is this a duplicate", "should we close this", "check this issue", "what do you think about this issue", or when given a dotnet/runtime issue URL or number and asked for an opinion. Handles bug reports, API proposals, enhancements, performance regressions, and questions.

Use when a code/test/comment diff is called bloated, slop, LLM slop, bullshit, WTF, crap, rubbish, embarrassing, overengineered, adhoc, or "not paid by LOC"; or when symptoms include bloated comments, superfluous planning .md / .tools / one-time setup / phase-or-sprint tags, huge-file growth instead of new-file extraction, 5 copy-pasted tests that should be 1 parametrized test, duplicated test setup, reinvented helpers, near-duplicate logic across files, low reuse, 4+ new module-level helpers for one bugfix, fresh whole-AST/IR/syntax-tree walkers, or 150+ added LOC for one bugfix. Also use proactively before opening a PR whose diff smells like any of the above.

Write release notes for completed changes. Use when PR modifies tracked paths and needs release notes entry.

Debug and fix --realsig+ (RealInternalSignature) codegen bugs in IlxGen — MethodAccessException / FieldAccessException / TypeAccessException at runtime, IL `private` vs `assembly` visibility, closure and TLR-lift placement (cloc / NestedTypeRefForCompLoc / effectiveCloc / moduleCloc). Use when a program compiles cleanly but crashes only under --realsig+, when IL accessibility differs between realsig modes, or when reasoning about where compiler-synthesized closures/state-machines/quotation helpers are nested.

Fix ILVerify baseline failures when IL shape changes (codegen, new types, method signatures). Use when CI fails on ILVerify job.

Triage a build / compile / restore / WarnAsError failure from its MSBuild binary log. Fetches the binlog (a local build's, or a failed dotnet/fsharp Azure DevOps PR build's published artifact) and analyzes it live via the `binlog-mcp` MCP server — structured errors, root-cause diagnosis, and an MSBuild perf X-ray. NOT for test failures or CheckCodeFormatting: a build binlog has no errors there.

Investigate compiler failures, test errors, or unexpected behavior through systematic minimal reproduction, 3-hypothesis testing, and verification. Always re-run builds and tests after changes.

Retrieve and analyze Azure DevOps build failures for GitHub PRs. Use when CI fails. CRITICAL: Collect ALL errors from ALL platforms FIRST, write hypotheses to file, then fix systematically.

Use when drafting, proposing, creating, or editing prose for a dotnet/fsharp GitHub PR or issue — body, title, comment, review summary, edits — including bare asks like "open a PR", "ship this", "write up what I did", "summarise the change", "reply on the PR", "edit the issue body", "gh pr create", "gh pr comment", "gh pr edit --body", "gh issue comment", "gh pr review --body". Primary use case is PR descriptions; same rules apply to PR/issue comments and review summaries. Not for labels, reviewers, merging, or code-review findings (just the prose write-up of them).

Generate and maintain .NET release notes from `features.json`. Uses `generate-changes` for authoritative shipped-change data, `generate-features` for scoring/triage, `update-existing-branch` for incremental reruns on populated branches, `editorial-scoring` for the shared rubric, `api-diff`/`dotnet-inspect` for API verification, and a multi-model `review-release-notes` pass for final editorial QA.

Refresh an existing .NET release-notes milestone branch set incrementally. Checks whether the VMR ref moved, regenerates `changes.json` only when needed, merges the delta into `features.json`, integrates new material into existing markdown clusters across the per-component branches, and responds to review feedback. USE FOR: reruns on a populated release-notes branch set. DO NOT USE FOR: first-pass generation of a new milestone (use generate-changes, generate-features, and release-notes).

Create and update per-distro package files in release-notes/{version}/distros/ that document .NET runtime dependencies and package availability for each Linux distribution. USE FOR: setting up distros/ for a new .NET version, updating dependency package names when distro versions change, auditing package data. DO NOT USE FOR: supported-os.json changes (use update-supported-os skill), os-packages.json (legacy format).

Create the GitHub release discussion in dotnet/core and the locked mirror announcement issue in dotnet/announcements for a .NET preview, RC, or GA release. USE FOR: publishing release discussions after release notes exist, mirroring a newly created discussion into dotnet/announcements, verifying an existing post, and re-running a partially completed publication safely. DO NOT USE FOR: writing release notes, generating changes/features.json, or retrying create commands blindly after cancellation.

Update the HAL+JSON release information graph when new .NET releases ship. Regenerates index files across the version hierarchy (root → major → patch), timeline hierarchy (timeline → year → month), llms.json, and downloads using graph generator tools. USE FOR: adding a new patch release to the graph, adding a new major version, updating timeline entries after a release, refreshing the graph after source data changes. DO NOT USE FOR: supported-os.json changes (use update-supported-os skill), querying the graph (use dotnet-releases skill on release-index branch), editing generated graph files by hand (update source data and regenerate).

Apply the shared reader-centric rubric used to rank candidate features for release notes, blog posts, and docs. Use this when you need scoring and cut guidance independent of any one output format or task.

Generate `changes.json` for a .NET release milestone by selecting the correct VMR base/head refs and running `release-notes generate changes`. Handles preview-only multi-branch targeting (`main` vs release branches vs tags) and emits the authoritative manifest of what shipped. DO NOT USE FOR: API verification/diffs (use api-diff), feature scoring (use generate-features), or writing markdown release notes (use release-notes).

Generate `features.json` from `changes.json` by ranking and annotating shipped changes. `features.json` keeps the same schema as `changes.json` and adds optional scoring fields so release notes, docs, and blog posts can apply different cutoffs. Uses the shared `editorial-scoring` rubric. DO NOT USE FOR: regenerating VMR diffs (use generate-changes) or writing final markdown (use release-notes).

Analyze CI build and test status from Azure DevOps and Helix for dotnet repository PRs. Use when checking CI status, investigating failures, determining if a PR is ready to merge, or given URLs containing dev.azure.com or helix.dot.net. Also use when asked "why is CI red", "test failures", "retry CI", "rerun tests", "is CI green", "build failed", "checks failing", or "flaky tests". DO NOT USE FOR: investigating stale codeflow PRs or dependency update health, tracing whether a commit has flowed from one repo to another, reviewing code changes for correctness or style.

Tell the history of a Maestro subscription using the darc CLI's get-subscription-history command. USE FOR: "what happened the last times this subscription ran", "show the trigger history for a subscription", "why did this subscription fail/not update", "did this subscription open a PR recently", inspecting subscription trigger outcomes (Updated, NoUpdate, NotUpdatable, Failure, UserError, HasConflict, Rescheduled), filtering outcomes by build id, date range, outcome type or free-text repo/branch search. DO NOT USE FOR: checking current subscription staleness/health (use flow-analysis or maestro-cli), tracing whether a commit reached a repo (use flow-tracing), CI build failures (use ci-analysis). INVOKES: shell (darc get-subscription-history).

Analyze a failed Azure DevOps PR build by reusing the binlog that build already produced — instead of rebuilding locally. Use when an `azure-pipelines` check on a GitHub PR transitions to `failure` and you need a structured root-cause analysis posted back as a PR review. Downloads `PostBuildLogs_*` / `Logs_Build_*` from the AzDO build artifacts, invokes the `binlog` MCP server (Microsoft.AITools.BinlogMcp) for build overview / errors / warnings (with deeper diagnostic capabilities — root-cause reports, property-value tracing — when the basics aren't enough), groups symptoms by root cause, and emits a single summary comment. Optionally attaches inline `suggestion` blocks when an error maps to a one-line fix on a diffed line. Cuts per-PR analysis cost from ~5–8 min (rebuild + analyze) to ~2–3 min (download + analyze). DO NOT USE FOR: pipelines that don't publish a binlog artifact, GitHub-Actions-only repos (no AzDO build to reuse), or general CI health dashboards (use `ci-analysis`).

Investigate AzDO pipeline failures beyond Helix — build errors, infra tooling crashes, validation test flakiness, artifact cascade failures. USE FOR: "why did the unified-build fail", "what's breaking the pipeline", "how often does this failure occur", "drill into build task logs", "1ES scan failures", "SourcelinkTests flaky", "NetAnalyzers build error", analyzing AzDO build timelines and task logs, failure frequency/trend analysis. DO NOT USE FOR: Helix test failures (use helix-investigation), CI status overview (use ci-analysis), codeflow PRs (use flow-analysis). INVOKES: AzDO, Helix, and binlog MCP tools, az CLI for internal auth, gh CLI.

Build the Arcade SDK from source, configure a local NuGet feed with the artifacts, and validate the build by running a test repository against the locally-built packages. Use when testing local Arcade changes against a consuming repo, validating Arcade SDK changes before merging, or verifying that a repo can build with a new Arcade version. Use when asked "test arcade", "build and test arcade", "validate arcade changes", "try arcade locally", "test arcade SDK", "build arcade packages", or "run a repo against local arcade". DO NOT USE FOR: CI analysis, Helix test investigation, codeflow/dependency-flow issues, or production Arcade SDK publishing.

Analyze VMR codeflow health using maestro MCP tools and GitHub MCP tools. USE FOR: investigating stale codeflow PRs, checking if fixes have flowed through the VMR pipeline, debugging dependency update issues, checking overall flow status for a repo, diagnosing why backflow PRs are missing or blocked, subscription health, build freshness, URLs containing dotnet-maestro or "Source code updates from dotnet/dotnet". DO NOT USE FOR: CI build failures (use ci-analysis skill), code review (use code-review skill), general PR investigation without codeflow context, tracing whether a specific commit/PR has reached another repo (use flow-tracing skill). INVOKES: maestro and GitHub MCP tools, flow-health.cs script.

Trace dependency flow across .NET repos through the VMR pipeline. USE FOR: checking if a PR/commit from repo A has reached repo B, finding what runtime SHA is in an SDK build, tracing dependency versions through the VMR, checking if a commit is included in an SDK build, decoding SDK version strings, "has my fix reached runtime", "did roslyn#80873 flow to runtime", "what SHA is in SDK version X", cross-repo dependency tracing, mapping SDK versions to VMR commits. DO NOT USE FOR: codeflow PR health or staleness (use flow-analysis skill), CI build failures (use ci-analysis skill). INVOKES: maestro and GitHub MCP tools, Get-SdkVersionTrace.ps1 script.

Analyze historical failure rates for Known Build Error issues by mining the edit history of issue bodies. Use when asked "when did this last fail", "failure history", "failure rate", "is this issue still active", "flaky test history", "known issue activity", or "most active known issues".

Install and validate a .NET SDK from an Azure DevOps internal build. Use this when asked to install, validate, or set up a .NET SDK from a dnceng/internal Azure DevOps build link or build ID.

Review code changes in dotnet/roslyn for correctness, performance, and consistency with project conventions. Use when reviewing PRs or code changes.

Update the agent knowledge base after making code changes in the Roslyn repo. Run at the end of every task that modifies code, adds files, changes public APIs or diagnostics, or establishes new patterns. Keeps .github/memory/ fresh and reliable.

Create or modify Roslyn IDE analyzers, code fixes, and code refactorings. Use when: adding a new IDE diagnostic (IDE0xxx), implementing a CodeFixProvider, implementing a CodeRefactoringProvider, writing analyzer/fixer tests, or working with AbstractBuiltInCodeStyleDiagnosticAnalyzer. Also use for: diagnostic analyzer, code action, FixAllProvider, TestInRegularAndScriptAsync, TestMissingInRegularAndScriptAsync.

Perform a branch snap (release branch cut) for dotnet repos like dotnet/roslyn. Use when: snapping a branch, cutting a release branch, creating a release branch, merging main into release, updating VS insertion config, updating darc subscriptions for a snap, moving milestones, or asked about snap workflow.

Import Razor formatting log zips that the user has already downloaded from Azure DevOps feedback tickets or GitHub issues into FormattingLogTest, validate whether the captured problem still reproduces, and if needed drive a minimal repro plus fix workflow.

Set up tracking for a new C# compiler feature: create test plan issue, feature label, update Language Feature Status page, and link related PRs. Use when: setting up a new language feature, creating a test plan, tracking a new csharplang proposal in roslyn, or asked to 'set up feature tracking'.

Run the razor-toolset-ci pipeline to validate the current branch against large third-party repositories (MudBlazor, OrchardCore, ASP.NET Core, etc.). Use when asked to run toolset tests, ecosystem tests, or third-party validation.

Add or change a dotnet CLI command, subcommand, or option across the relevant CLI projects. USE FOR: adding or changing a dotnet CLI command/subcommand, adding a new Option<T> or Argument<T>, registering a subcommand in the command tree, changing an option's help description or a command's runtime message, wiring a command parser, or updating --help output.

Include a dotnet CLI command or feature in the Native AOT CLI (src/Cli/dotnet-aot) and prove it works. USE FOR: enabling a command/option in dotnet-aot, adding source files to AotSourceFiles.props, gating AOT-incompatible code with #if CLI_AOT, building and NativeAOT-publishing dotnet-aot, writing/updating the AOT parser + integration tests, running the local dn harness in AOT mode and comparing it to the managed CLI. DO NOT USE FOR: resolving IL trim/AOT analyzer warnings (use dotnet-aot-compat), running dotnet.Tests incrementally (use incremental-test), or pure managed CLI work.

Regenerate Static Web Assets test baselines. USE FOR: fixing "generated manifest should match the expected baseline" errors, updating baseline JSON files after legitimate build output changes, understanding the baseline comparison system.

Review code changes in dotnet/sdk for problems — either a GitHub pull request or local changes in your branch before a PR exists. Use when asked to review a PR, review local or uncommitted changes, do a code review, check a PR or branch for issues, or review pull request changes. Focuses only on identifying problems — not style nits or praise.

Run dotnet.Tests incrementally without a full build.cmd rebuild. Use after modifying source code in SDK projects to quickly build only changed projects, deploy their outputs into the redist SDK layout, and run tests against them.

Author end-to-end Static Web Assets integration tests that exercise MSBuild targets through build, publish, or pack. USE FOR: writing new SWA integration tests, choosing a test asset and base class, dynamically modifying projects at runtime, selecting the right manifest to assert on, verifying the full asset pipeline (primary, compressed, endpoints). DO NOT USE FOR: unit tests of individual tasks (write those directly), baseline regeneration (use swa-baseline-regeneration), troubleshooting failures (use swa-troubleshooting).

Understand and fix Static Web Assets Pack tests. USE FOR: fixing Pack test assertion failures after nupkg content changes, tracing MSBuild conditions to expected nupkg content, updating test assertions for new or changed package layouts, understanding conditional pack logic in .targets files.

Diagnose and fix common Static Web Assets test and build failures. USE FOR: analyzing CI failures, identifying root cause categories from error messages, fixing metadata propagation bugs, timing/ordering issues in MSBuild targets, test assertion mismatches.

Instructions for restoring and building the WinForms repository. Use when asked how to restore NuGet packages, build the full solution, build a single project, create packages, or troubleshoot build errors.

Instructions for downloading and installing .NET preview runtime versions required by the WinForms repository. Use when test executables fail with "framework not found" errors or when a specific .NET preview runtime version needs to be installed.

Instructions for running unit tests, integration tests, and individual tests in the WinForms repository. Use this when asked how to run tests, filter them, use Visual Studio workflows, or troubleshoot test failures.

Instructions for modernizing and refactoring existing C# / VB.NET code files. Use when asked to refactor, modernize, clean up, review, or improve existing source files in this repository. Covers upgrading to C# 14 / .NET 10 idioms, comment quality, spelling and grammar fixes, XML documentation, and readability improvements.

C# and .NET coding standards for generating new code files. Use when creating new classes, methods, controls, tests, or any new C# / VB source files in this repository. Covers C# 14 / .NET 10 patterns, naming, formatting, XML docs, WinForms conventions, and performance idioms.

Instructions for writing unit tests for Graphics, Bitmap, GraphicsPath, and Font rendering APIs in System.Drawing. Covers bitmap-based verification, integer/float overload testing, version-guarded test blocks, and FluentAssertions patterns for path-point validation.

Instructions for adding new public APIs (properties, methods, events, delegates) to existing WinForms controls or components. Covers API issue tracking, PublicAPI file maintenance, property/event conventions, CodeDOM serialization, design-time attributes, and XML documentation.

Instructions for using GDI, GDI+ for drawing primitives, shapes and processing/rendering bitmaps and rendering Fonts. Also, tenets for adding new APIs to System.Drawing for modernization and improving drawing, imaging, and font features.