Faster Copilot Studio with .NET 10 and WebAssembly: Key Questions Answered

Copilot Studio, Microsoft's platform for building intelligent chat experiences, has upgraded its browser-based .NET engine from .NET 8 to .NET 10. This move taps into the latest WebAssembly (WASM) improvements, bringing automatic asset fingerprinting, smaller Ahead-of-Time (AOT) output, and a smoother deployment pipeline. The team reports that the migration was straightforward and is now live in production. Below, we answer the most pressing questions about what this upgrade means for developers and end users.

What is the recent update in Copilot Studio regarding .NET and WebAssembly?

Copilot Studio now runs on .NET 10 WebAssembly. A few months ago, the team detailed how they use .NET and WASM to execute C# code directly in the browser. After moving from .NET 6 to .NET 8, they measured significant performance gains. The latest leap to .NET 10 introduces two major improvements: automatic fingerprinting of WASM assets and smaller AOT builds via the WasmStripILAfterAOT feature (now enabled by default). These changes reduce manual scripting, enhance security, and optimize download sizes without sacrificing runtime speed.

How easy was the upgrade from .NET 8 to .NET 10?

The migration was remarkably smooth. For most .NET WASM applications, upgrading involves updating the target framework in .csproj files and verifying that all dependencies are compatible with .NET 10. Copilot Studio followed exactly that path, and the .NET 10 build is now running in production with no major hiccups. The team noted that the upgrade process itself took minimal effort, thanks to backward compatibility and the maturity of the .NET runtime.

What is automatic fingerprinting and how does it simplify deployment?

Automatic fingerprinting is a .NET 10 feature for WebAssembly that appends a unique identifier to each published asset's filename. This serves dual purposes: it busts caches (so users always get the latest version) and provides integrity guarantees (verifying that files haven't been tampered with). In earlier versions, developers had to:

• Read the blazor.boot.json manifest to list assets.
• Run a custom PowerShell script to rename each file with a SHA256 hash.
• Explicitly pass an integrity argument from JavaScript when loading resources.

With .NET 10, all of that manual work is eliminated. The dotnet.js loader imports resources directly, fingerprints are built into filenames, and integrity validation happens automatically. Copilot Studio deleted its custom renaming script and removed the integrity argument from the client-side resource loader, simplifying their codebase.

What was the previous manual process for asset integrity?

Before .NET 10, ensuring asset integrity in Copilot Studio required a multi-step, custom approach. First, the team had to read the published blazor.boot.json manifest to enumerate all WASM assets. Then they ran a PowerShell script that appended a SHA256 hash to each file name. Finally, from JavaScript, they had to pass an explicit integrity argument when requesting each resource. This process was error-prone and added maintenance overhead. With automatic fingerprinting in .NET 10, the entire manual pipeline is obsolete—the framework handles fingerprinting and validation out of the box.

What is WasmStripILAfterAOT and how does it affect output size?

WasmStripILAfterAOT is a setting that removes the Intermediate Language (IL) for methods that have been compiled ahead-of-time to WebAssembly. Since the IL is no longer needed at runtime, stripping it reduces the published output size. In .NET 8 this option existed but defaulted to false. In .NET 10, it is enabled by default for AOT builds, leading to noticeably smaller download packages. For Copilot Studio, which uses a hybrid JIT/AOT strategy, the stripping means that AOT assemblies no longer match their JIT counterparts byte for byte, reducing the number of files that can be deduplicated—but the overall size savings still benefit end users.

How does Copilot Studio balance JIT and AOT engines?

Copilot Studio ships a single NPM package containing both a Just-in-Time (JIT) engine and an Ahead-of-Time (AOT) engine. The JIT engine loads quickly, allowing the user to start interacting immediately. Meanwhile, the AOT engine compiles in the background for maximum execution speed. At runtime, both engines load in parallel: JIT handles initial interactions, then control seamlessly hands off to AOT once it's ready. Bit-for-bit identical files between the two modes are deduplicated to keep the package small. This hybrid approach gives users fast startup times combined with the steady‑state performance of AOT.

Any tips for loading .NET WASM in a WebWorker?

If you load the .NET WASM runtime inside a WebWorker, remember to set dotnetSidecar = true when initializing. This ensures proper initialization in a worker context, preventing common pitfalls. Copilot Studio's team advises this configuration to guarantee that the runtime behaves correctly, especially when running alongside other browser threads. The tip is simple but critical for anyone planning to move WASM execution off the main thread.