Copilot Studio, Microsoft’s AI-powered copilot builder, has taken another leap forward by upgrading its .NET WebAssembly (WASM) engine from .NET 8 to .NET 10. This move builds on previous performance gains and introduces several automations and optimizations that streamline development, improve runtime efficiency, and reduce deployment complexity. In this article, we break down the ten most impactful changes that come with this upgrade—from smoother migrations to smarter asset handling. Whether you’re a Copilot Studio developer or just curious about how .NET evolves in the browser, these insights will help you understand what’s new and why it matters.

1. Seamless Framework Migration

Upgrading an existing .NET 8 WASM application to .NET 10 is remarkably straightforward—typically just a matter of updating the target framework in the .csproj files and verifying dependency compatibility. For Copilot Studio, this process went without a hitch, and the .NET 10 build is now running in production. This smooth migration means teams can focus on leveraging new features instead of troubleshooting upgrade issues. The Copilot Studio team reported no breaking changes in their codebase, highlighting .NET’s commitment to backward compatibility. If you’re planning a similar upgrade, expect minimal disruption and a clear path to the latest performance and security improvements.

2. Automatic Fingerprinting of WASM Assets

One of the most welcome changes in .NET 10 for WebAssembly applications is automatic fingerprinting of WASM assets. When you publish a WebAssembly app, each asset’s filename now includes a unique identifier derived from its content. This provides built-in cache-busting and integrity guarantees without any manual intervention. Previously, developers had to read the published blazor.boot.json manifest, run custom PowerShell scripts to rename files with SHA256 hashes, and pass explicit integrity arguments from JavaScript. Now, all that complexity is eliminated—fingerprints are part of the published filenames, and integrity validation happens automatically. This reduces deployment friction and ensures that users always get the correct, uncorrupted assets.

3. Elimination of Custom Deployment Scripts

With automatic fingerprinting, Copilot Studio was able to delete its custom renaming script and remove the integrity argument from the client-side resource loader. This not only simplifies the codebase but also reduces the risk of human error during build and deployment. The team no longer needs to maintain a separate PowerShell or Node.js script to hash files or update manifest references. Existing caching and validation logic built on top of these resources continues to work unchanged, so there’s no need to overhaul existing infrastructure. This is a clear win for maintainability and developer productivity.

4. Improved Integrity Validation

Automatic fingerprinting also enhances integrity validation. In .NET 10, resources are imported directly from dotnet.js with fingerprints embedded. The runtime verifies that the fetched asset matches the expected hash, preventing tampered or corrupted files from executing. This is especially important for production environments where security and reliability are paramount. Previously, developers had to manually pass integrity arguments from JavaScript for each resource—a tedious and error-prone process. Now, the validation is baked into the framework, providing a higher level of trust without extra code.

5. Tip: WebWorker Initialization with dotnetSidecar

For teams that load the .NET WASM runtime inside a WebWorker, .NET 10 introduces a helpful configuration option: set dotnetSidecar = true when initializing the runtime. This ensures proper initialization in a worker context, avoiding common pitfalls like missing event handlers or cross-thread synchronization issues. Copilot Studio uses this technique to run WASM in the background without blocking the main thread, improving responsiveness. If you’re building a browser-based app that needs to offload heavy computation, consider using a WebWorker with the dotnetSidecar flag to take full advantage of .NET’s multi-threading capabilities.

6. WasmStripILAfterAOT Now Default

A significant optimization in .NET 10 is that WasmStripILAfterAOT is now enabled by default for AOT (Ahead-of-Time) builds. After compiling .NET methods to native WebAssembly, the original Intermediate Language (IL) is no longer needed at runtime. In .NET 8, this setting existed but defaulted to false, meaning the IL was retained, bloating the output. Now, .NET 10 automatically strips the IL from published AOT assemblies, reducing file sizes and download times. This is a low-effort, high-impact improvement—just upgrade your target framework and your AOT builds get smaller automatically.

7. Smaller AOT Output in Production

The practical effect of WasmStripILAfterAOT is a measurable reduction in AOT output size. For Copilot Studio, which ships both JIT (Just-In-Time) and AOT engines in a single NPM package, this means less data to download and faster startup times. The stripped assemblies are also more efficient to cache, as they contain only the executable code needed at runtime. In benchmarks, the team observed a reduction of several megabytes in total package size, translating to quicker load times for end users. This is especially valuable for mobile or low-bandwidth scenarios where every kilobyte counts.

8. Dual-Engine Strategy: JIT and AOT in Parallel

Copilot Studio employs a sophisticated packaging strategy that combines both a JIT engine (for fast startup) and an AOT engine (for maximum execution speed). In .NET 10, this dual-engine approach continues to be supported and optimized. At runtime, the app loads JIT and AOT in parallel; the JIT engine handles initial interactions almost instantly, then seamlessly hands off to the AOT engine once it’s ready. This gives users the best of both worlds—immediate responsiveness and sustained performance. The upgrade to .NET 10 did not break this architecture, and the team can now benefit from smaller AOT outputs while keeping the JIT path lean.

9. Enhanced Deduplication for Dual Engines

Because WasmStripILAfterAOT produces AOT assemblies that no longer match their JIT counterparts, Copilot Studio had to adapt its deduplication logic. Files that are bit-for-bit identical between the two modes are deduplicated to keep the package small. In .NET 10, this deduplication becomes even more effective because the stripped AOT assemblies are uniquely sized, reducing the overlap with JIT assemblies. The team reports that fewer duplicate files remain, further shrinking the overall delivery footprint. This careful balancing act ensures that the NPM package remains compact without sacrificing performance.

10. Proven Performance Gains from Continuous Upgrades

The move from .NET 6 to .NET 8 already delivered significant performance improvements for Copilot Studio, and the upgrade to .NET 10 continues that trend. Beyond the specific features listed above, the team benefits from general runtime improvements, better garbage collection, and optimized WebAssembly interop. These incremental gains compound over time, making Copilot Studio snappier and more reliable for users. The smooth upgrade path also means that future .NET versions will be just as easy to adopt, ensuring the platform stays at the forefront of browser-based .NET performance. If you’re running a WASM application, consider following Copilot Studio’s lead and upgrading to .NET 10 today.

Conclusion: Copilot Studio’s migration to .NET 10 WebAssembly demonstrates how a well-managed upgrade can unlock substantial developer and end-user benefits. From automatic fingerprinting that eliminates manual scripts to default AOT optimizations that shrink payloads, each improvement contributes to a faster, more maintainable, and more secure application. The dual-engine strategy remains intact, and the overall codebase is cleaner. For teams working with .NET in the browser, these ten takeaways provide a clear roadmap for what to expect—and how to prepare for an equally seamless upgrade.