Add migrate-dotnet10-to-dotnet11 skill by danmoseley · Pull Request #153 · dotnet/skills

danmoseley · 2026-02-28T03:53:27Z

Adds a new migration skill that guides upgrading .NET 10 projects to .NET 11, covering TFM updates, NuGet package upgrades, and source-breaking changes documented so far in .NET 11 Preview 1.

Sources

Overview of all breaking changes in .NET 11 — https://learn.microsoft.com/en-us/dotnet/core/compatibility/11
Entity Framework Core breaking changes in .NET 11 — https://learn.microsoft.com/en-us/ef/core/what-is-new/ef-core-11.0/breaking-changes
C# 15 compiler breaking changes — https://learn.microsoft.com/en-us/dotnet/csharp/whats-new/breaking-changes/compiler%20breaking%20changes%20-%20dotnet%2011

ASP.NET Core and WinForms breaking changes pages do not yet exist for .NET 11.

Skill coverage

The skill follows a structured 6-step workflow: assess → update TFMs/packages → fix source-incompatible changes → check behavioral changes → update infrastructure → verify. It references 6 conditional reference files loaded based on project type:

Core libraries — NamedPipeClientStream constructor removal (SYSLIB0063), ZLibStream/GZipStream/DeflateStream behavioral changes, Utf8JsonWriter.WriteRawValue validation, TAR entry name changes
C# 15 compiler (Roslyn) — Span<T> safe-context rules, ref readonly InAttribute changes, nameof(this.Member) semantics, with expression parsing, dynamic &&/|| operator resolution
EF Core 11 — Cosmos DB synchronous I/O fully removed
Cryptography — DSA removed from macOS
Runtime/JIT — Hardware baseline requirements (x86-64-v2, Arm64 LSE/AES)
SDK/MSBuild — Mono launch target removed

Eval suite

7 scenarios in eval.yaml testing compression/TAR changes, C# 15 compiler breaks, EF Core Cosmos migration, hardware requirements, DSA macOS, TFM updates, and dynamic operator resolution.

Status

This is an early skill covering .NET 11 Preview 1 only. Reference files will be expanded as Previews 2–7 ship and more breaking changes are documented.

Files added (9 files, ~800 lines)

plugins/dotnet/skills/migrate-dotnet10-to-dotnet11/SKILL.md
plugins/dotnet/skills/migrate-dotnet10-to-dotnet11/references/ (6 reference files)
tests/dotnet/migrate-dotnet10-to-dotnet11/eval.yaml
.github/CODEOWNERS (updated)

Adds a new migration skill that guides upgrading .NET 10 projects to .NET 11, covering TFM updates, NuGet package upgrades, and breaking changes across the .NET 11 Preview 1 surface area. Sources: - https://learn.microsoft.com/en-us/dotnet/core/compatibility/11 - https://learn.microsoft.com/en-us/ef/core/what-is-new/ef-core-11.0/breaking-changes - https://learn.microsoft.com/en-us/dotnet/csharp/whats-new/breaking-changes/compiler%20breaking%20changes%20-%20dotnet%2011 - https://learn.microsoft.com/en-us/dotnet/core/whats-new/dotnet-11/overview Skill coverage: - C# 15 compiler: Span safe-context, ref readonly InAttribute, nameof(this.), with() parsing, dynamic &&/|| with interfaces - Core libraries: DeflateStream/GZipStream empty payloads, MemoryStream capacity, TAR checksum validation, ZipArchive.CreateAsync eager loading, Environment.TickCount consistency - EF Core 11: Cosmos DB sync I/O fully removed - Cryptography: DSA removed from macOS - Runtime/JIT: x86-64-v2 minimum, Arm64 LSE requirement on Windows - SDK: Mono launch target removed for .NET Framework apps 6 reference files loaded based on project type + 7 eval scenarios. Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Add documentation for the NamedPipeClientStream constructor obsoletion (SYSLIB0063) which was merged in dotnet/runtime#120328 for .NET 11 but not yet documented on learn.microsoft.com. The isConnected parameter overload is obsoleted, and projects with TreatWarningsAsErrors will fail to build. Changes: - core-libraries.md: Add Obsoleted APIs section with SYSLIB0063 - SKILL.md: Add to description, Step 1 assessment, Step 3 patterns Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

- Add explicit migration framing to skill description to differentiate from csharp-scripts skill (SDK was routing to wrong skill) - Add 'Use the migrate-dotnet10-to-dotnet11 skill' to eval prompts, matching real-world usage where users explicitly invoke migration skills Eval results (3 runs each, explicit skill invocation): Haiku: 6/7 activated, best +1.3 (compression/TAR scenario) Sonnet: 7/7 activated, best +0.3 (EF Core, TFM update scenarios) Skill activates reliably now. Quality gains are modest because the skill covers only Preview 1 breaking changes (training data already includes MS Learn docs). Expect larger gains as content grows with later previews. Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

danmoseley · 2026-02-28T03:54:43Z

Did some eval testing and this seems limited value over no-skill in part because there are relatively few breaking changes; the agent can search the web by itself without this skill. In later previews we may be able to add more nuances here and make it useful. Opening the PR as a placeholder for now.

danmoseley · 2026-02-28T03:55:00Z

fyi @mcastro-x

Copilot

Pull request overview

Adds a new dotnet migration skill (migrate-dotnet10-to-dotnet11) to guide upgrading projects from .NET 10 to .NET 11, backed by scoped reference docs and an eval suite to validate coverage.

Changes:

Added migrate-dotnet10-to-dotnet11 skill with a structured migration workflow.
Added 6 technology-area reference documents (core libraries, C# compiler, EF Core, crypto, runtime/JIT, SDK/MSBuild).
Added a 7-scenario eval.yaml test suite plus CODEOWNERS entries for the new skill/tests.

Reviewed changes

Copilot reviewed 9 out of 9 changed files in this pull request and generated 3 comments.

Show a summary per file

File	Description
`plugins/dotnet/skills/migrate-dotnet10-to-dotnet11/SKILL.md`	New migration skill definition and step-by-step workflow.
`plugins/dotnet/skills/migrate-dotnet10-to-dotnet11/references/core-libraries.md`	Reference notes for core library breaking/behavioral changes.
`plugins/dotnet/skills/migrate-dotnet10-to-dotnet11/references/csharp-compiler.md`	Reference notes for C# 15/Roslyn breaking changes.
`plugins/dotnet/skills/migrate-dotnet10-to-dotnet11/references/efcore.md`	Reference notes for EF Core 11 (Cosmos sync I/O removal).
`plugins/dotnet/skills/migrate-dotnet10-to-dotnet11/references/cryptography.md`	Reference notes for crypto breaking changes (DSA on macOS).
`plugins/dotnet/skills/migrate-dotnet10-to-dotnet11/references/runtime-jit.md`	Reference notes for runtime/JIT changes (hardware baseline, etc.).
`plugins/dotnet/skills/migrate-dotnet10-to-dotnet11/references/sdk-msbuild.md`	Reference notes for SDK/MSBuild behavioral change.
`tests/dotnet/migrate-dotnet10-to-dotnet11/eval.yaml`	Eval scenarios validating the skill’s guidance across the covered areas.
`.github/CODEOWNERS`	Assigns ownership for the new skill and its tests.

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plugins/dotnet/skills/migrate-dotnet10-to-dotnet11/SKILL.md

plugins/dotnet/skills/migrate-dotnet10-to-dotnet11/references/csharp-compiler.md

…csharp-compiler.md Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>

danmoseley · 2026-02-28T04:02:22Z

Validated against PowerShell/PowerShell

Tested the skill by checking out PowerShell/PowerShell at commit 1965e059 (pre-.NET 11 upgrade) and following the skill workflow to migrate from .NET 10 to .NET 11 Preview 1. Compared results against the human-authored gold commit 212c5f97 (32 files, 71 insertions, 67 deletions).

Gold commit breakdown

Category	Files	Skill coverage
TFM updates (`net10.0` -> `net11.0`)	~11	✅ Step 2
Package version bumps (17 packages)	~8	✅ Step 2
`global.json` SDK pin	1	✅ Step 5
SYSLIB0063: `NamedPipeClientStream` `isConnected` obsoletion	1	✅ Step 3 pattern #7
Span collection expression safe-context (`#if UNIX` only)	1	✅ Step 3 pattern #1
Build scripts / CI (`net10.0` string replacements)	~8	⚠️ Partial
BOM/manifest (runtime-specific packaging)	1	❌ Not applicable
Docs	1	⚠️ Partial

Live test results

Updated global.json, TFMs, and net10.0 references across 20 files
Built using PowerShell's own build system (Start-PSBuild)
One build error: SYSLIB0063 on RemoteSessionNamedPipe.cs:1302 -- skill pattern Skill idea: Source Generator / Analyzer Authoring #7 guided the fix (remove isConnected parameter)
Rebuild: success ✅
The Span collection expression issue (src/powershell/Program.cs) is inside #if UNIX so didn't trigger on Windows. On cross-platform CI it would surface, and skill pattern Initial documentation and validation workflow #1 covers the exact fix used by the human (new int[] { ... })

Scorecard

Metric	Result
Build-breaking changes fixed by skill	2/2 (100%)
Files correctly handled	30/32 (94%)
Build after skill-guided migration	✅ Passed
Skill fix matches gold commit	✅ Exact match for both code fixes

The 2 uncovered files are a PowerShell-specific BOM manifest (windows.json) and a doc file -- neither is a .NET breaking change.

Note: SYSLIB0063 was discovered through this test and was not in Microsoft's breaking change docs (the runtime PR dotnet/runtime#120328 still has the needs-breaking-change-doc-created label). It was added to the skill's core-libraries.md as a result of this validation.

Separate the breaking and fixed code into distinct blocks to avoid ambiguity about which line to use vs remove. Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

danmoseley · 2026-03-03T20:14:33Z

This skill isn't super compelling right now as there aren't many changes, but there are also few users so I think it's reaosnable to merge it now and we'll iterate in future previews and learn.

danmoseley · 2026-03-03T21:15:28Z

getting some more reviews

danmoseley · 2026-03-04T02:04:37Z

Closing in favor of a new PR — this one was orphaned when the fork relationship with dotnet/skills was re-established.

danmoseley and others added 3 commits February 27, 2026 18:05

Copilot AI review requested due to automatic review settings February 28, 2026 03:53

danmoseley requested review from dbreshears and timheuer as code owners February 28, 2026 03:53

Copilot started reviewing on behalf of danmoseley February 28, 2026 03:53 View session

Copilot AI reviewed Feb 28, 2026

View reviewed changes

Update plugins/dotnet/skills/migrate-dotnet10-to-dotnet11/references/…

8a01fd1

…csharp-compiler.md Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>

danmoseley and others added 2 commits February 27, 2026 21:03

Split nameof(this.) example into before/after code blocks

443cd72

Separate the breaking and fixed code into distinct blocks to avoid ambiguity about which line to use vs remove. Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Merge branch 'main' into migrate-dotnet10-to-dotnet11

a600908

danmoseley closed this Mar 4, 2026

danmoseley mentioned this pull request Mar 4, 2026

Add migrate-dotnet10-to-dotnet11 skill #181

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danmoseley commented Feb 28, 2026

Sources

Skill coverage

Eval suite

Status

Files added (9 files, ~800 lines)

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Pull request overview

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danmoseley commented Feb 28, 2026

Validated against PowerShell/PowerShell

Gold commit breakdown

Live test results

Scorecard

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