Getting it into your agent
One page per mod, every tool's command on it. A separate URL per tool would split the same page into five that compete with each other.
npx skills add managedcode/dotnet-skills --skill migrate-dotnet8-to-dotnet9git clone --depth 1 https://github.com/managedcode/dotnet-skillsWrote this? Show the measurements
A badge with what this costs and how it scanned, read live from this page, so it follows the numbers instead of freezing them. Markdown for a README, HTML for a documentation site or a project page.
[](https://agentmods.dev/skills/managedcode/dotnet-skills/migrate-dotnet8-to-dotnet9)<a href="https://agentmods.dev/skills/managedcode/dotnet-skills/migrate-dotnet8-to-dotnet9"><img src="https://agentmods.dev/badge/skills/managedcode/dotnet-skills/migrate-dotnet8-to-dotnet9.svg" alt="Measured on agentmods" height="20"></a>What it costs to keep this loaded
Counted locally with the o200k_base tokenizer, which is exact for GPT models; Claude uses its own tokenizer and its counts differ. Treat this as one consistent yardstick across the catalogue rather than a bill. Prices are per million input tokens.
| Model | Per session | Once invoked |
|---|---|---|
| Fable 5.1 | $0.00176 | $0.03892 |
| Opus 5 | $0.00088 | $0.01946 |
| Sonnet 5 | $0.00035 | $0.00778 |
| Haiku 4.5 | $0.00018 | $0.00389 |
Grade A, and why
migrate-dotnet8-to-dotnet9 scanned grade A with 0 findings against 26 rules in 11 categories — prompt injection, anti-refusal, data exfiltration, privilege escalation, supply chain, agent snooping, system-prompt leakage, SSRF and excessive agency — measured 3d ago.
A static scan of the body, not an audit. Every finding is printed with the line that produced it so you can judge whether it matters here. A mod is markdown that instructs an agent; that is exactly why what it instructs is worth reading.
Nothing flagged
None of the 26 patterns this scan looks for appear in this file: no shell pipes, no recursive deletes, no credential paths, no hidden text, no instruction-override or anti-refusal phrasing, no agent-config snooping. That is not a guarantee, it is the absence of the things that are checkable.
This is a copy
100% identical to migrate-dotnet8-to-dotnet9 — 0 lines differ, which has more behind it and is treated as the original. This page carries a canonical link to it rather than competing with it.
How it starts
The opening of the file, as written. The whole thing — 233 lines — stays where its author put it; the contents beside it link to each section on GitHub.
.NET 8 → .NET 9 Migration
Migrate a .NET 8 project or solution to .NET 9, systematically resolving all breaking changes. The outcome is a project targeting net9.0 that builds cleanly, passes tests, and accounts for every behavioral, source-incompatible, and binary-incompatible change introduced in the .NET 9 release.
When to Use
- Upgrading
TargetFrameworkfromnet8.0tonet9.0 - Resolving build errors or new warnings after updating the .NET 9 SDK
- Adapting to behavioral changes in .NET 9 runtime, ASP.NET Core 9, or EF Core 9
- Replacing
BinaryFormatterusage (now always throws at runtime) - Updating CI/CD pipelines, Dockerfiles, or deployment scripts for .NET 9
When Not to Use
- The project already targets
net9.0and builds cleanly — migration is done. If the goal is to reachnet10.0, use themigrate-dotnet9-to-dotnet10skill as the next step. - Upgrading from .NET 7 or earlier — address the prior version breaking changes first
- Migrating from .NET Framework — that is a separate, larger effort
- Greenfield projects that start on .NET 9 (no migration needed)
Inputs
| Input | Required | Description |
|---|---|---|
| Project or solution path | Yes | The .csproj, .sln, or .slnx entry point to migrate |
| Build command | No | How to build (e.g., dotnet build, a repo build script). Auto-detect if not provided |
| Test command | No | How to run tests (e.g., dotnet test). Auto-detect if not provided |
| Project type hints | No | Whether the project uses ASP.NET Core, EF Core, WinForms, WPF, containers, etc. Auto-detect from PackageReferences and SDK attributes if not provided |
Workflow
Answer directly from the loaded reference documents. Do not search the filesystem or fetch web pages for breaking change information — the references contain the authoritative details. Focus on identifying which breaking changes apply and providing concrete fixes.
Commit strategy: Commit at each logical boundary — after updating the TFM (Step 2), after resolving build errors (Step 3), after addressing behavioral changes (Step 4), and after updating infrastructure (Step 5). This keeps each commit focused and reviewable.
What ships with it
11 files beside SKILL.md in the same directory: the scripts, references and assets a skill reads on demand. Not counted in the per-session cost; read them before you install if any of them is executable.
- manifest.json 162 B
- references/aspnet-core-dotnet8to9.md 2.3 KB
- references/containers-interop-dotnet8to9.md 1.9 KB
- references/core-libraries-dotnet8to9.md 7.0 KB
- references/cryptography-dotnet8to9.md 2.1 KB
- references/csharp-compiler-dotnet8to9.md 3.3 KB
- references/deployment-runtime-dotnet8to9.md 2.4 KB
- references/efcore-dotnet8to9.md 6.9 KB
- references/sdk-msbuild-dotnet8to9.md 2.3 KB
- references/serialization-networking-dotnet8to9.md 5.4 KB
- references/winforms-wpf-dotnet8to9.md 3.7 KB
What this file has done since we first saw it
Hashed on every crawl. A supply-chain change to an agent config is a question of when, not whether, so the history is kept rather than the latest state alone.
- 3d ago First seen · 233 lines · 176 tokens per session scan A 95d6de4776cc
migrate-dotnet8-to-dotnet9 is a skill published in the GitHub repository managedcode/dotnet-skills (477 stars, last pushed yesterday), licensed MIT. It adds 176 tokens to every session and 3,892 once invoked, about $0.0009 per session on Opus 5. A static security scan graded it A with 0 findings. It is 100% identical to migrate-dotnet8-to-dotnet9, differing in 0 lines, and is treated as a copy.
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