Copilot Studio Achieves Faster Performance with .NET 10 WebAssembly Upgrade

Overview

Microsoft Copilot Studio, the platform that enables C# execution directly in the browser via .NET WebAssembly (WASM), continues to push performance boundaries. After previously migrating from .NET 6 to .NET 8 and seeing significant gains, the team has now upgraded to .NET 10. This upgrade brings a smooth migration path, automatic asset fingerprinting that simplifies deployment, and reduced output sizes through default AOT optimizations. Here’s a closer look at how the upgrade unfolded and the improvements it delivers.

A Seamless Migration Experience

Upgrading an existing .NET WASM application from version 8 to version 10 is straightforward. For Copilot Studio, the process primarily involved updating the target framework in the .csproj files and verifying that all dependencies were compatible with .NET 10. This minimal-effort approach meant the team could quickly move the production environment to the new runtime, with the .NET 10 build now running live with no disruption to users.

Automatic Fingerprinting Simplifies Deployment

One of the most welcome improvements in .NET 10 for WebAssembly applications is the automatic fingerprinting of WASM assets. When you publish a WebAssembly app, each asset’s filename now includes a unique identifier. This built-in mechanism provides both cache-busting and integrity guarantees without requiring any manual intervention.

Previously, Copilot Studio—like many WASM apps—had to implement a custom workflow:

• Read the published blazor.boot.json manifest to enumerate all assets.
• Run a custom PowerShell script to rename each file with an appended SHA256 hash.
• Pass an explicit integrity argument from JavaScript when requesting each resource.

In .NET 10, all of that manual effort disappears. Resources are now imported directly from dotnet.js, fingerprints are part of the published filenames, and integrity validation happens automatically. The Copilot Studio team was able to delete the custom renaming script and remove the integrity argument from the client-side resource loader. Existing caching and validation logic on top of these resources continues to work unchanged.

Tip: If you load the .NET WASM runtime inside a WebWorker, set dotnetSidecar = true when initializing to ensure proper initialization in a worker context.

Smaller AOT Output with WasmStripILAfterAOT

The other major headline for .NET WASM in .NET 10 is that WasmStripILAfterAOT is now enabled by default for AOT builds. After ahead-of-time compiling .NET methods to WebAssembly, the original Intermediate Language (IL) for those methods is no longer needed at runtime. By stripping it out of the published output, .NET 10 reduces the final download size. In .NET 8, this setting existed but defaulted to false.

Copilot Studio uses a slightly more advanced packaging strategy to get the best of both startup time and steady-state performance. The platform ships a single NPM package that contains both a JIT engine (for fast startup) and an AOT engine (for maximum execution speed). At runtime, Copilot Studio loads JIT and AOT in parallel: the JIT engine handles initial interactions, then control hands off to AOT once it’s ready. Files that are bit-for-bit identical between the two modes are deduplicated to keep the package small.

Because WasmStripILAfterAOT produces AOT assemblies that no longer match their JIT counterparts, fewer files can be shared between the two engines. However, the team reports that the overall size savings from stripping IL outweigh the loss of some deduplication. The result is a leaner final package that loads faster and executes more efficiently.

Conclusion

The upgrade to .NET 10 has delivered tangible benefits for Copilot Studio: a painless migration, streamlined deployment with automatic fingerprinting, and smaller AOT output thanks to default IL stripping. These improvements enhance both developer experience and end-user performance, demonstrating how .NET continues to evolve as a powerful platform for browser-based applications. For teams considering a similar upgrade, the steps are minimal, and the rewards are clear.