Replace Upgrade Assistant content with GitHub Copilot app modernization guidance

[Copilot]

Fixes #36436

.NET Upgrade Assistant has been deprecated by Microsoft. This PR updates the ASP.NET Framework to ASP.NET Core migration documentation to direct users to GitHub Copilot app modernization instead.

Changes:

• tooling.md: Replaced all Upgrade Assistant step-by-step instructions with:

  • [!IMPORTANT] deprecation notice (matching the standard block from dotnet/docs)
  • Brief intro paragraph pointing to the new tooling
  • "See also" section with links to GitHub Copilot app modernization docs
  • Updated metadata (ai-usage, ms.date)

• start.md: Removed two Upgrade Assistant references for consistency

• index.md: Updated tooling.md reference to no longer mention Upgrade Assistant

Original prompt

---

This section details on the original issue you should resolve

<issue_title>Upgrade Assistant mentions need to be replaced-retired</issue_title>
<issue_description>Follow how this is handled in related issue: dotnet/docs#50261

This product is no longer supported by MS and has been replaced by GHCP AppMod.

Remove the Upgrade Assistant centered content from this topic:
Learn to upgrade from ASP.NET MVC, Web API, and Web

Then replace with replace with a paragraph intro that in turn then sends developers to:
How to upgrade a .NET app with GitHub Copilot app modernization - .NET Core | Microsoft Learn

..and then in the See also, also point to this Overview:
GitHub Copilot app modernization overview | Microsoft Learn

Likely we will not use this, but it is good to be aware the following warning used in the .NET docs:
https://github.com/dotnet/docs/blob/main/docs/core/porting/includes/github-copilot-suggestion.md

@adegeo who is handling the related issue on the dotnet/docs repo.</issue_description>

<agent_instructions>Read through both the issue description and all discussion before determining the proper soluttion.</agent_instructions>

Comments on the Issue (you are @copilot in this section)

@wadepickett ## AI Analysis Report **Run by:** @wadepickett **Date:** 2025-12-04 **Issue:** #36436 **Model:** GitHub Copilot ---

Issue Analysis: Upgrade Assistant mentions need to be replaced-retired

✅ Issue Validation

Status: Valid and actionable

📋 Issue Summary

The issue highlights the need to update a particular documentation topic (Learn to upgrade from ASP.NET MVC, Web API, and Web) in the ASP.NET Core docs. The content currently refers to the "Upgrade Assistant" tool, which has been retired by Microsoft and superseded by the GitHub Copilot App Modernization (GHCP AppMod) approach. The issue requests removal of Upgrade Assistant-centric content, replacement with an introductory paragraph directing readers to the latest modernization guidance, and additional links in the "See also" section.

📁 Affected Files

File/Article	Path	Lines	Section
Main article	aspnetcore/migration/fx-to-core/tooling.md	TBD: spans Upgrade Assistant content	Section: "Upgrade using Upgrade Assistant" and relevant intro/see also

📝 Proposed Changes

Documentation Updates

File: aspnetcore/migration/fx-to-core/tooling.md

• Remove Upgrade Assistant-focused content (section titled "Upgrade using Upgrade Assistant" and any other mentions).
• Insert a paragraph, after introductory material or where Upgrade Assistant was previously referenced, explaining that Upgrade Assistant is retired and replaced by "GitHub Copilot app modernization" tooling.
• Add link:
  • How to upgrade a .NET app with GitHub Copilot app modernization - .NET Core | Microsoft Learn
• Update "See also" section to include:
  • GitHub Copilot app modernization overview | Microsoft Learn

Current content to be replaced:
(Excerpt from Upgrade Assistant section, lines TBD)

Upgrade using Upgrade Assistant
You can use the .NET Upgrade Assistant to port ASP.NET apps to ASP.NET Core...
// ... further details about the Upgrade Assistant

Proposed replacement text:

> [!NOTE]
> The .NET Upgrade Assistant tool has been retired and is no longer supported by Microsoft. App modernization efforts should now use the GitHub Copilot app modernization toolset.
>
> To learn how to upgrade your ASP.NET apps, see:
> [How to upgrade a .NET app with GitHub Copilot app modernization](https://learn.microsoft.com/en-us/dotnet/core/porting/github-copilot-app-modernization/how-to-upgrade-with-github-copilot).

See also section—add:

- [GitHub Copilot app modernization overview](https://learn.microsoft.com/en-us/dotnet/core/porting/github-copilot-app-modernization/overview)

Note: No code samples are involved in this change.

🎯 Action Plan

1. Edit file: [aspnetcore/migration/fx-to-core/tooling.md](ht...

• Fixes Upgrade Assistant mentions need to be replaced-retired #36436

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Internal previews

📄 File	🔗 Preview link
aspnetcore/migration/fx-to-core/index.md	Migrate from ASP.NET Framework to ASP.NET Core
aspnetcore/migration/fx-to-core/start.md	Get started with incremental ASP.NET to ASP.NET Core migration
aspnetcore/migration/fx-to-core/tooling.md	Use tooling to help migrate ASP.NET Framework to ASP.NET Core