Enhanced Security hinders performance of WASM applications (Including Blazor)

Unfortunately, therein lies the problem. We can't ask them to add this in the bypass as they believe this is crucially an important security feature. We can explain the technology issues behind what is happening, but fundamentally this is a problem where they will now believe that there is an issue with our tool itself, that we cannot build to "the leading browser's security standards" - while both the browser and the library used to make the tool are made by the same company! How can we justify using this when we will get the blame for an issue we have no power over solving, other than completely dropping webassembly in its entirety. 

At the very least, the fact that it seems like both the Edge team and the Blazor team seem to say there is nothing that can be done other than literally switching the feature off, makes it very hard for us to actually do anything about this issue if a customer decides it's necessary.

Your Blazor WebAssembly slowdown under policy-enforced Edge Enhanced Security matches Microsoft’s documented behavior. Enhanced Security runs WebAssembly through an interpreter, which Microsoft warns might not provide expected performance; this is a security tradeoff, not a Blazor configuration fault.

First, review applied policies and record EnhanceSecurityMode, EnhanceSecurityModeAllowUserBypass, and JavaScript JIT policies. If policy controls the setting and user bypass is disabled, the user cannot correct it locally. Ask the Edge administrator to add the application’s domain to EnhanceSecurityModeBypassListDomains, refresh policy, restart Edge, and retest. If DefaultJavaScriptJitSetting also blocks JIT, the administrator should review JavaScriptJitAllowedForSites; its exceptions operate at registrable-domain granularity and apply separately to embedded frames. Avoid disabling Enhanced Security globally unless the organization accepts that reduced protection. If domain exceptions are prohibited, Microsoft documents no client-side Blazor setting that restores JIT performance. Capture the Edge version, applied policies, and a performance trace, then open a Microsoft support case.