Blazor Hot Reload in .NET 10: Why Co-Hosted Matters

There’s a lot of talk right now about .NET 10, Visual Studio 2026, and something called Razor co-hosting. It’s often just a bullet point on a slide, but what does it actually mean? And why should Blazor developers care?

A few days ago, I sat down with David Wengier, one of the engineers working on Razor co-hosting. We spent about an hour going through how Razor tooling used to work, why it was so complicated, and what has actually changed under the hood.

To understand why this matters, we first need to look at the old world: multiple language servers, lots of LSP messages flying back and forth, duplicated work, and two different “realities” when it comes to source code and line numbers. That complexity is the reason hot reload was flaky and why the editor sometimes felt… confused.

Razor co-hosting changes all of that. The Razor language server is no longer a separate process. Instead, Razor is now hosted inside the C# language server, sharing the same syntax tree and semantic model. Fewer round-trips, less translation, better performance, and much more reliable hot reload.

This video walks through:
* How Razor tooling worked before
* Why it was so hard to get right
* What co-hosting actually means
* Why this is a big deal for Blazor and Razor developers

Let me know in the comments what you’re seeing so far. Is the editor better? Is hot reload more reliable? This is just the first step, and there’s more coming.

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