Microsoft Copilot Studio has upgraded its WebAssembly (WASM) engine to .NET 10, delivering significant performance improvements and streamlining deployment processes. The move, which follows a previous upgrade from .NET 6 to .NET 8, marks a leap forward in the platform's ability to run C# code directly in the browser.
"The migration to .NET 10 was remarkably smooth," said a Copilot Studio engineer. "We simply updated the target framework in our project files and ensured compatibility. The new build is now running in production."
Background
Copilot Studio is a low-code platform for building intelligent chatbot agents. It leverages .NET and WebAssembly (WASM) to execute C# logic in the browser, enabling rich server-side behaviors without round trips. Earlier this year, the team shared how moving from .NET 6 to .NET 8 improved startup times and execution speed.
The upgrade to .NET 10 builds on that foundation. Key improvements include automatic fingerprinting of WASM assets and smaller AOT (ahead-of-time) compiled outputs.
Automatic Fingerprinting Simplifies Deployment
One of the most impactful changes in .NET 10 is automatic fingerprinting. When publishing a WASM app, each asset's filename now includes a unique identifier, providing cache-busting and integrity validation without manual scripting.
Previously, Copilot Studio required a custom PowerShell script that read a manifest, renamed files with SHA256 hashes, and passed integrity arguments from JavaScript. "With .NET 10, all that manual work is gone," the engineer explained. "Resources are imported directly from dotnet.js, fingerprints are included in filenames, and integrity is validated automatically. We deleted our custom renaming script and removed the integrity argument from the client-side loader."
Existing caching and validation logic continues to work unchanged. For those loading the WASM runtime in a WebWorker, setting dotnetSidecar = true during initialization ensures proper behavior.
Smaller AOT Output with WasmStripILAfterAOT
.NET 10 also enables WasmStripILAfterAOT by default for AOT builds. After compiling .NET methods to WebAssembly, the original Intermediate Language (IL) is no longer needed at runtime. Stripping it out reduces download size and speeds up load times.
Copilot Studio uses a hybrid packaging strategy: shipping both a JIT engine for fast startup and an AOT engine for maximum performance. Both are loaded in parallel; the JIT handles initial interactions while the AOT compiles in the background. Files identical between modes are deduplicated. However, because WasmStripILAfterAOT makes AOT assemblies differ from their JIT counterparts, fewer files can be shared. The team reports that the overall package size remains manageable, and the performance gains offset any small increase.
What This Means
For developers building chatbots with Copilot Studio, the upgrade translates to faster cold-start times, smoother real-time interactions, and simpler deployment pipelines. Automatic fingerprinting eliminates error-prone manual steps, while smaller AOT outputs reduce bandwidth usage.
For end users, this means more responsive bots that can handle complex logic in the browser nearly instantaneously. The combination of JIT and AOT ensures both quick initial responses and sustained high performance.
The Copilot Studio team plans to continue optimizing on .NET 10, with further improvements expected in upcoming releases. As the engineer noted, "This upgrade sets the stage for even more ambitious AI-driven scenarios."