dotnet/BenchmarkDotNet · critical · NotSupportedException

Unknown .NET Runtime

Error message

Unknown .NET Runtime

What it means

Thrown by RuntimeInformation.GetCurrentRuntime() when none of the known runtime detectors match: IsWasm, IsNewMono, IsOldMono, IsFullFramework, IsNetCore, and IsNativeAOT all return false. This means BenchmarkDotNet cannot identify the executing .NET runtime and therefore cannot select appropriate host execution strategies, CoreRT/Mono/AOT runtimes, or framework characteristics.

Source

Thrown at src/BenchmarkDotNet/Portability/RuntimeInformation.cs:208

        internal static Runtime GetCurrentRuntime()
        {
            //do not change the order of conditions because it may cause incorrect determination of runtime
            if (IsAot && IsMono)
                return MonoAotLLVMRuntime.Default;
            if (IsWasm)
                return WasmRuntime.Default;
            if (IsNewMono)
                return MonoRuntime.GetCurrentVersion();
            if (IsOldMono)
                return MonoRuntime.Default;
            if (IsFullFramework)
                return ClrRuntime.GetCurrentVersion();
            if (IsNetCore)
                return CoreRuntime.GetCurrentVersion();
            if (IsNativeAOT)
                return NativeAotRuntime.GetCurrentVersion();

            throw new NotSupportedException("Unknown .NET Runtime");
        }

        public static Platform GetCurrentPlatform()
        {
            // these are not part of .NET Standard 2.0, so we use hardcoded values taken from
            // https://github.com/dotnet/runtime/blob/080fcae7eaa8367abf7900e08ff2e52e3efea5bf/src/libraries/System.Private.CoreLib/src/System/Runtime/InteropServices/Architecture.cs#L9
            const Architecture Wasm = (Architecture)4;
            const Architecture S390x = (Architecture)5;
            const Architecture LoongArch64 = (Architecture)6;
            const Architecture Armv6 = (Architecture)7;
            const Architecture Ppc64le = (Architecture)8;
            const Architecture RiscV64 = (Architecture)9;

            switch (ProcessArchitecture)
            {
                case Architecture.Arm:
                    return Platform.Arm;
                case Architecture.Arm64:

View on GitHub (pinned to b515068b61)

Solutions

  1. Upgrade BenchmarkDotNet to a version that supports the target runtime.
  2. If running on a known runtime that is misdetected, check environment variables and runtime information the detectors rely on.
  3. For unsupported runtimes, consider explicitly specifying the runtime in the Job configuration rather than relying on auto-detection.
  4. Report the issue to BenchmarkDotNet with details of the runtime and OS for a detector update.

Example fix

// before (auto-detection fails)
var config = ManualConfig.Create(DefaultConfig.Instance);

// after (explicitly specify runtime)
var config = ManualConfig.Create(DefaultConfig.Instance)
    .AddJob(Job.Default.WithRuntime(CoreRuntime.Core80));
Defensive patterns

Strategy: fallback

Try / catch

try
{
    var runtime = RuntimeInformation.GetCurrentRuntime();
}
catch (NotSupportedException)
{
    // Fallback: explicitly specify the runtime in the Job config
    var job = Job.Default.WithRuntime(CoreRuntime.Core80);
}

Prevention

When it happens

Trigger: Running BenchmarkDotNet on an unsupported or unrecognized runtime environment, such as a preview/new runtime flavor whose detection heuristics (registry keys, environment variables, type presence checks) are not yet implemented, or on a stripped/self-contained runtime where the detection markers are absent.

Common situations: Using a very new .NET preview or a non-standard runtime (e.g., a custom NativeAOT variant, WASM without the expected detector, or an exotic platform). Also on runtimes where BenchmarkDotNet's version predates the runtime's release.

Related errors

AI-assisted analysis of dotnet/BenchmarkDotNet@b515068b61 (2026-08-13). Data as JSON: /api/errors/70f90fc36a14eaaa. Report an issue: GitHub.