Add migrate-dotnet10-to-dotnet11 skill by danmoseley · Pull Request #181 · dotnet/skills

danmoseley · 2026-03-04T02:04:40Z

Recreated from #153 (original PR was orphaned when the fork relationship with dotnet/skills was re-established).

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>

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

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>

Copilot

Pull request overview

Adds a new .NET migration skill package to the dotnet plugin, including reference material and an eval suite to validate the skill’s guidance for .NET 10 → .NET 11 upgrades.

Changes:

Added migrate-dotnet10-to-dotnet11 skill with a structured workflow and conditional reference loading.
Added 6 reference documents covering core libraries, C# compiler, EF Core, crypto, runtime/JIT, and SDK/MSBuild breaking changes.
Added a 7-scenario eval suite and updated CODEOWNERS for the new skill/test directories.

Reviewed changes

Copilot reviewed 9 out of 9 changed files in this pull request and generated 4 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 guidance.
`plugins/dotnet/skills/migrate-dotnet10-to-dotnet11/references/core-libraries.md`	Core library breaking changes reference used by the skill.
`plugins/dotnet/skills/migrate-dotnet10-to-dotnet11/references/csharp-compiler.md`	C# 15 / Roslyn breaking changes reference used by the skill.
`plugins/dotnet/skills/migrate-dotnet10-to-dotnet11/references/efcore.md`	EF Core 11 breaking changes reference (Cosmos sync I/O removal).
`plugins/dotnet/skills/migrate-dotnet10-to-dotnet11/references/cryptography.md`	Crypto breaking changes reference (DSA removal on macOS).
`plugins/dotnet/skills/migrate-dotnet10-to-dotnet11/references/runtime-jit.md`	Runtime/JIT breaking changes reference (hardware baseline, globalization).
`plugins/dotnet/skills/migrate-dotnet10-to-dotnet11/references/sdk-msbuild.md`	SDK/MSBuild breaking changes reference (Mono launch target behavior).
`tests/dotnet/migrate-dotnet10-to-dotnet11/eval.yaml`	New eval scenarios asserting the skill covers key migration breaks and fixes.
`.github/CODEOWNERS`	Assigns ownership for the new skill and test directories.

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tests/dotnet/migrate-dotnet10-to-dotnet11/eval.yaml

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

plugins/dotnet/skills/migrate-dotnet10-to-dotnet11/references/csharp-compiler-dotnet10to11.md

ViktorHofer · 2026-03-04T20:08:19Z

/evaluate

github-actions · 2026-03-04T20:15:38Z

Skill Validation Results

Skill	Scenario	Baseline	With Skill	Δ	Skills Loaded	Overfit	Verdict
migrate-dotnet10-to-dotnet11	Console app with compression and TAR operations	2.7/5	1.0/5	-1.7	✅ tools: skill	✅ 0.04	❌
migrate-dotnet10-to-dotnet11	C# 15 compiler breaking changes — Span safe-context, nameof, with()	3.3/5	2.3/5	-1.0	✅ tools: skill	✅ 0.04	✅
migrate-dotnet10-to-dotnet11	EF Core app with Cosmos DB provider using sync APIs	4.0/5	4.0/5	0.0	✅ tools: skill	✅ 0.04	✅
migrate-dotnet10-to-dotnet11	Deployment to older hardware with minimum requirement changes	3.0/5	3.0/5	0.0	✅ tools: skill	✅ 0.04	❌
migrate-dotnet10-to-dotnet11	Cryptography app using DSA on macOS	4.0/5	3.7/5	-0.3	✅ tools: skill	✅ 0.04	❌
migrate-dotnet10-to-dotnet11	Basic TFM update with Docker and global.json	4.3/5	4.0/5	-0.3	✅ tools: skill	✅ 0.04	✅
migrate-dotnet10-to-dotnet11	C# 15 dynamic operator and ref readonly delegate issues	4.0/5	2.0/5	-2.0	✅ tools: skill	✅ 0.04	❌

Model: claude-opus-4.6 | Judge: claude-opus-4.6

Full results

- SKILL.md: Show global.json as a diff edit preserving existing keys (rollForward, other settings) instead of replacing the entire file - csharp-compiler.md: Fix ref readonly lambda example to use a static field instead of a captured local (which won't compile in a lambda) - csharp-compiler.md: Declare missing local variable x in ref readonly local function example - eval.yaml: Fix ref readonly lambda snippet to use a class with a static field, matching the reference file fix Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Copilot

Pull request overview

Copilot reviewed 9 out of 9 changed files in this pull request and generated 1 comment.

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.github/CODEOWNERS

danmoseley · 2026-03-04T22:14:25Z

Local Eval Results (post review-feedback fixes)

3 iterations (the CI run posted above used 1 iteration), claude-opus-4.6 model & judge, run locally.

Scenario	Baseline	With Skill	Δ	Overfit	Verdict
Console app with compression and TAR operations ⏰	2.0/5	1.0/5	-1.0	✅ 0.06	✅
C# 15 compiler breaking changes — Span safe-context, nameof, with()	2.7/5	2.7/5	0.0	✅ 0.06	✅
EF Core app with Cosmos DB provider using sync APIs	3.0/5	3.3/5	+0.3	✅ 0.06	❌
Deployment to older hardware with minimum requirement changes	2.7/5	3.0/5	+0.3	✅ 0.06	✅
Cryptography app using DSA on macOS ⏰	2.0/5	3.0/5	+1.0	✅ 0.06	✅
Basic TFM update with Docker and global.json	3.3/5	4.0/5	+0.7	✅ 0.06	✅
C# 15 dynamic operator and ref readonly delegate issues ⏰	2.0/5	1.7/5	-0.3	✅ 0.06	✅

Overall: ✅ passed (22.4% improvement, threshold 10%). Skill activated in all 7 scenarios. No overfitting detected.

⏰ = baseline run(s) hit timeout (agent spent time searching for non-existent skill file in empty workspace).

ViktorHofer · 2026-03-04T22:24:40Z

the CI run posted above used 1 iteration

3

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

AndriySvyryd

Reviewed EF Core content

@ViktorHofer

…Core - Add @ViktorHofer as second owner for migrate-dotnet10-to-dotnet11 and migrate-nullable-references paths per CONTRIBUTING.md requirements - Add Preview 1 annotation to EF Core reference file per reviewer feedback Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Rename e.g. efcore.md to efcore-dotnet10to11.md so names won't collide with reference files from other version migration skills. Update all paths in SKILL.md to match. Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

ViktorHofer · 2026-03-05T07:33:45Z

/evaluate

danmoseley and others added 6 commits February 27, 2026 18:05

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

8a01fd1

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

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 requested a review from timheuer as a code owner March 4, 2026 02:04

Copilot AI review requested due to automatic review settings March 4, 2026 02:04

danmoseley requested a review from dbreshears as a code owner March 4, 2026 02:04

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danmoseley requested a review from Copilot March 4, 2026 21:35

Copilot started reviewing on behalf of danmoseley March 4, 2026 21:36 View session

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danmoseley and others added 2 commits March 4, 2026 18:30

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Add migrate-dotnet10-to-dotnet11 skill#181

Add migrate-dotnet10-to-dotnet11 skill#181
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ViktorHofer commented Mar 4, 2026

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danmoseley commented Mar 4, 2026

Local Eval Results (post review-feedback fixes)

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