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.NET 11 Preview 6 removes the separate Mono path for MAUI on Android, iOS, and Mac Catalyst. CoreCLR is now the only mobile runtime, the UseMonoRuntime escape hatch is closed, and GA is set for November 2026.

Extension indexers landed in .NET 11 Preview 6, letting you add this[...] access to types you do not own. They complete the extension members story that started with methods and properties in C# 14.

This error means the BuildContext you passed is above the Scaffold or ScaffoldMessenger, not below it. Wrap the caller in a Builder, extract it into its own widget, or use a GlobalKey.

This runtime error means a null reached a cast expecting a non-nullable type, almost always from JSON. Make the field nullable, or supply a default before the cast runs.

There is no single Skill type in the Microsoft Agent Framework, but you can package domain expertise as a reusable agent, reuse it in-process with AsAIFunction, and advertise it across frameworks as an A2A AgentSkill. Full walkthrough on Agent Framework 1.0 and .NET 11.

Preview 6 rejects unsafe cross-origin browser requests by default, reading the Sec-Fetch-Site header instead of an antiforgery token. Here is what it blocks and how to opt out.

Kestrel caps request bodies at 30,000,000 bytes by default and returns 413 when you exceed it. Raise MaxRequestBodySize globally, per endpoint, or in web.config behind IIS.

One trailing comma or unescaped Windows path in your MCP config makes every server vanish, not just the broken one. Validate the JSON, fix the five usual suspects, restart.

You set a header, status code, or content type after the body was already flushed. Set all headers before the first write, or guard with HttpResponse.HasStarted and OnStarting.

EF Core hit a property it does not know how to store. Map it as a complex type, convert it with HasConversion, give it a key, or ignore it with [NotMapped].