Introduction
Microsoft Copilot Studio, the platform for building AI-powered assistants, has taken another leap forward by upgrading its WebAssembly runtime to .NET 10. Following a previous transition from .NET 6 to .NET 8, this latest move delivers faster startup times, smaller downloads, and a smoother deployment pipeline. Here’s a look at what changed and the real-world benefits now hitting production.
A Seamless Migration Process
Updating Dependencies
Shifting an existing .NET 8 WebAssembly application to .NET 10 is remarkably straightforward. For Copilot Studio, the team simply updated the target framework moniker in their .csproj files and verified that all dependencies were compatible with the new runtime version. No complex rewrites or workarounds were necessary, and the .NET 10 build is now running live in production.
Streamlined Deployment with Automatic Fingerprinting
Eliminating Manual Steps
One of the most welcome enhancements in .NET 10 for WebAssembly apps is automatic fingerprinting of WASM assets. When publishing an application, each resource file now receives a unique identifier baked into its filename, providing both cache-busting and integrity verification without any manual configuration.
Previously, Copilot Studio – like many WASM projects – had to follow a labor-intensive process:
- Parse the
blazor.boot.jsonmanifest to enumerate all deployed assets. - Run a custom PowerShell script to append a SHA256 hash to every filename.
- Explicitly supply an integrity argument from JavaScript when requesting each resource.
With .NET 10, that entire workflow disappears. Resources are imported directly from dotnet.js, fingerprints are part of the published filenames, and integrity checks happen automatically behind the scenes. The Copilot Studio team deleted their custom renaming script and removed 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 during initialization to ensure proper behavior in a worker context.
Reduced AOT Build Size
WasmStripILAfterAOT Enabled by Default
Another major improvement in .NET 10 is that WasmStripILAfterAOT is now turned on by default for ahead-of-time compiled builds. After every .NET method is compiled to WebAssembly, the original intermediate language (IL) is no longer needed at runtime. By stripping that IL from the published output, .NET 10 reduces the overall download size.
In .NET 8, this setting existed but defaulted to false, so most teams had to manually enable it to gain the benefit. Copilot Studio, however, uses a more sophisticated packaging strategy. To balance startup speed and long‑run performance, they ship a single npm package containing both a JIT engine (for rapid initial startup) and an AOT engine (for maximum steady‑state speed). At runtime, both engines load in parallel: the JIT engine handles early interactions while the AOT engine prepares in the background, then seamlessly takes over.
Because WasmStripILAfterAOT produces AOT assemblies that no longer match their JIT equivalents, fewer files can be deduplicated between the two modes. Nonetheless, the net effect is a leaner package and faster download for end users.
Conclusion
The upgrade to .NET 10 brings tangible wins for Copilot Studio: automatic fingerprinting eliminates manual script management, while smaller AOT builds reduce payload sizes. Combined, these changes accelerate both developer productivity and runtime performance, demonstrating how incremental platform improvements can deliver big results in production environments.