Accelerating Copilot Studio: .NET 10 on WebAssembly Delivers Speed and Simplicity

Microsoft Copilot Studio leverages .NET and WebAssembly (WASM) to run C# directly in the browser, enabling rich AI-powered interactions. Recently, the team upgraded their WASM runtime from .NET 8 to .NET 10, unlocking significant performance gains and streamlining deployment. This Q&A explores the migration process, key new features like automatic fingerprinting and WasmStripILAfterAOT, and how Copilot Studio optimizes both startup time and steady-state performance using a dual-engine strategy.

What is Copilot Studio and why did it upgrade to .NET 10?

Microsoft Copilot Studio is a platform that hosts AI copilots, running C# in the browser via .NET WebAssembly. The team originally migrated from .NET 6 to .NET 8 to improve performance and innovation. Continuing that trajectory, they moved to .NET 10 to take advantage of new WASM-specific optimizations. The upgrade delivered a smoother developer experience and better end-user performance, including faster execution and simpler asset management. By staying on the latest .NET version, Copilot Studio ensures it leverages cutting-edge improvements in compilation, caching, and integrity verification.

How did the migration from .NET 8 to .NET 10 proceed?

The migration was remarkably straightforward. For Copilot Studio, the main change was updating the target framework in .csproj files and verifying that all dependencies were compatible with .NET 10. No major code rewrites were needed, and the team was able to get the .NET 10 build running in production quickly. This smooth transition highlights .NET's commitment to backward compatibility and incremental upgrades. The team reports that the new runtime has been stable and performant since deployment.

What is automatic fingerprinting in .NET 10 for WebAssembly?

Automatic fingerprinting is a feature in .NET 10 that automatically appends a unique hash to each WebAssembly asset's filename during publishing. This serves two purposes: cache-busting (users always get the latest version) and integrity verification (browsers can check that the asset hasn't been tampered with). Previously, developers had to implement this manually—reading the manifest, renaming files, and passing integrity arguments from JavaScript. With .NET 10, all of that is handled by the build tooling. For Copilot Studio, this meant they could delete their custom PowerShell renaming script and simplify their client-side resource loader. Existing caching and validation logic remains compatible, making the transition seamless.

How did Copilot Studio handle fingerprinting before .NET 10?

Before .NET 10, Copilot Studio (like many WASM apps) had to manually implement fingerprinting. The process involved:

• Reading the blazor.boot.json manifest to enumerate all published assets.
• Running a custom PowerShell script to rename each file, appending a SHA256 hash to the filename.
• Passing an explicit integrity argument from JavaScript when requesting each resource via the <script> tag.

This approach was error-prone and required maintaining custom tooling. With .NET 10, fingerprinting is integrated into the build pipeline, eliminating the need for that manual work and reducing the risk of mismatched hashes or missing integrity checks. The team now enjoys a simpler, more reliable deployment process.

What is WasmStripILAfterAOT and why is it significant?

WasmStripILAfterAOT is a .NET 10 feature enabled by default for AOT (Ahead-of-Time) builds. When you compile .NET methods to WebAssembly using AOT, the original Intermediate Language (IL) for those methods is no longer needed at runtime. In .NET 8, this setting existed but defaulted to false, meaning the IL was kept in the published output, increasing download size. In .NET 10, the compiler strips that IL automatically, resulting in smaller AOT output. For Copilot Studio, this directly reduces the size of the AOT engine package, speeding up load times and improving bandwidth efficiency without any code changes.

How does Copilot Studio combine JIT and AOT engines for optimal performance?

Copilot Studio uses an advanced dual-engine strategy to balance startup speed and steady-state performance. It ships a single NPM package containing both a JIT (Just-In-Time) engine for fast startup and an AOT (Ahead-of-Time) engine for maximum execution speed. At runtime, both engines load in parallel: the JIT engine handles initial interactions immediately, then seamlessly hands control to the AOT engine once it's ready. Files that are bit-for-bit identical between the two modes are deduplicated to keep the package size minimal. With .NET 10's WasmStripILAfterAOT, the AOT assemblies no longer match their JIT counterparts, so fewer files can be shared—but the net result is still a net win due to smaller AOT size and faster execution. This architecture ensures a responsive user experience from the first click while delivering peak performance for long-running tasks.

What is the overall impact of .NET 10 on Copilot Studio's deployment?

The upgrade to .NET 10 has streamlined Copilot Studio's deployment pipeline in two major ways. First, automatic fingerprinting has removed the need for a custom PowerShell script and manual integrity arguments, reducing maintenance overhead and the risk of human error. Second, WasmStripILAfterAOT brings smaller AOT builds out of the box, lowering bandwidth costs and improving load times for end users. Together, these changes make deploying new versions of Copilot Studio faster and more reliable. The team was able to delete old tooling, simplify their client-side code, and still maintain all existing caching and validation logic. The result is a more efficient development workflow and a better experience for users of Copilot Studio.