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)

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

...otnet-upgrade/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	4.7/5	4.3/5	-0.4	✅ tools: skill, stop_bash	🟡 0.40	✅
migrate-dotnet10-to-dotnet11	C# 15 compiler breaking changes — Span safe-context, nameof, with()	2.7/5	3.0/5	+0.3	✅ tools: skill	🟡 0.40	✅
migrate-dotnet10-to-dotnet11	EF Core app with Cosmos DB provider using sync APIs	4.3/5	2.7/5	-1.6	✅ tools: skill	🟡 0.40	✅
migrate-dotnet10-to-dotnet11	Deployment to older hardware with minimum requirement changes	4.0/5	2.0/5	-2.0	✅ tools: skill	🟡 0.40	❌
migrate-dotnet10-to-dotnet11	Cryptography app using DSA on macOS	4.3/5	3.7/5	-0.6	✅ tools: skill	🟡 0.40	❌
migrate-dotnet10-to-dotnet11	Basic TFM update with Docker and global.json	4.0/5	4.7/5	+0.7	✅ tools: skill	🟡 0.40	✅
migrate-dotnet10-to-dotnet11	C# 15 dynamic operator and ref readonly delegate issues	5.0/5	2.0/5	-3.0	✅ tools: skill	🟡 0.40	❌

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

Full results

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 · 2026-03-05T07:33:45Z

/evaluate

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>

- 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>

@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>

danmoseley · 2026-03-07T05:30:38Z

/evaluate

danmoseley · 2026-03-07T05:30:52Z

Moved to dotnet-upgrade plugin.

@ViktorHofer does this look OK to merge too?

github-actions · 2026-03-07T05:37:59Z

✅ Evaluation completed. View results | View workflow run

danmoseley · 2026-03-07T06:11:25Z

@ViktorHofer in the table above that the validate flag produced, why eg

migrate-dotnet10-to-dotnet11 | EF Core app with Cosmos DB provider using sync APIs | 4.3/5 | 2.7/5 | -1.6 | ✅ tools: skill | 🟡 0.40 | ✅

seems the skill made things worse (4.3 to 2.7) so why the check mark? It would be nice if the evaluator put some text after the table like "skill is better overall" or something.

Also if the evaluator is going to update an existing comment, it should show the commit that it tested with.

And I think I still don't understand why I got better results, also pasted above.

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

Copilot started reviewing on behalf of danmoseley March 4, 2026 02:05 View session

Copilot AI reviewed Mar 4, 2026

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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

Copilot AI reviewed Mar 4, 2026

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AndriySvyryd reviewed Mar 5, 2026

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AndriySvyryd approved these changes Mar 5, 2026

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github-actions bot mentioned this pull request Mar 7, 2026

🏥 Repository Health Dashboard #168

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danmoseley and others added 8 commits March 6, 2026 22:28

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

f20cabe

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

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

8e60562

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 force-pushed the migrate-dotnet10-to-dotnet11 branch from 8fbf5e5 to 35c2533 Compare March 7, 2026 05:29

danmoseley requested a review from a team March 7, 2026 05:29

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danmoseley commented Mar 4, 2026 • edited Loading Uh oh! There was an error while loading. Please reload this page.

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Files added (9 files, ~800 lines)

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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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danmoseley commented Mar 4, 2026 •

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