dotnet/runtime · critical · Error

Expected internals to be an array

Error message

Expected internals to be an array

What it means

Thrown by dotnetInitializeModule when the `internals` argument passed to the runtime initializer is not an Array. The runtime expects internals to be a positional array indexed by InternalExchangeIndex (RuntimeAPI, export tables, etc.); a non-array indicates the loader and the native module are talking different protocols.

Source

Thrown at src/native/libs/System.Runtime.InteropServices.JavaScript.Native/native/index.ts:37

export function SystemInteropJS_ReleaseCSOwnedObject(jsHandle: JSHandle): void {
    _ems_.dotnetRuntimeExports.releaseCSOwnedObject(jsHandle);
}

export function SystemInteropJS_ResolveOrRejectPromise(args: JSMarshalerArguments): void {
    _ems_.dotnetRuntimeExports.resolveOrRejectPromise(args);
}

export function SystemInteropJS_CancelPromise(taskHolderGCHandle: GCHandle): void {
    _ems_.dotnetRuntimeExports.cancelPromise(taskHolderGCHandle);
}

export function SystemInteropJS_InvokeJSFunction(functionJSSHandle: JSHandle, args: JSMarshalerArguments): void {
    _ems_.dotnetRuntimeExports.invokeJSFunction(functionJSSHandle, args);
}

export const gitHash = GitHash;
export function dotnetInitializeModule(internals: InternalExchange): void {
    if (!Array.isArray(internals)) throw new Error("Expected internals to be an array");
    const runtimeApi = internals[InternalExchangeIndex.RuntimeAPI];
    if (typeof runtimeApi !== "object") throw new Error("Expected internals to have RuntimeAPI");

    if (runtimeApi.runtimeBuildInfo.gitHash && runtimeApi.runtimeBuildInfo.gitHash !== _ems_.DOTNET_INTEROP.gitHash) {
        throw new Error(`Mismatched git hashes between loader and runtime. Loader: ${runtimeApi.runtimeBuildInfo.gitHash}, DOTNET_INTEROP: ${_ems_.DOTNET_INTEROP.gitHash}`);
    }

    internals[InternalExchangeIndex.InteropJavaScriptExportsTable] = interopJavaScriptExportsToTable({
        SystemInteropJS_GetManagedStackTrace: (args: JSMarshalerArguments) => _ems_._SystemInteropJS_GetManagedStackTrace(args),
        SystemInteropJS_CallDelegate: (args: JSMarshalerArguments) => _ems_._SystemInteropJS_CallDelegate(args),
        SystemInteropJS_CompleteTask: (args: JSMarshalerArguments) => _ems_._SystemInteropJS_CompleteTask(args),
        SystemInteropJS_ReleaseJSOwnedObjectByGCHandle: (args: JSMarshalerArguments) => _ems_._SystemInteropJS_ReleaseJSOwnedObjectByGCHandle(args),
        SystemInteropJS_BindAssemblyExports: (args: JSMarshalerArguments) => _ems_._SystemInteropJS_BindAssemblyExports(args),
        SystemInteropJS_CallJSExport: (methodHandle: CSFnHandle, args: JSMarshalerArguments) => _ems_._SystemInteropJS_CallJSExport(methodHandle, args),
    });
    function interopJavaScriptExportsToTable(map: InteropJavaScriptExports): InteropJavaScriptExportsTable {
        // keep in sync with interopJavaScriptExportsFromTable()
        return [

View on GitHub (pinned to 290d5ab72c)

Solutions

1. Use the matching set of runtime files from a single .NET SDK build (clean the output directory and republish).
2. If hosting manually, pass internals as an array with slots populated per InternalExchangeIndex.
3. Verify there is exactly one version of each runtime file on the page/server.

function assertInternalsShape(internals: unknown) {
    if (!Array.isArray(internals)) {
        throw new TypeError("Loader/runtime mismatch: internals must be an array");
    }
}

const isInternalsArray = (v: unknown): v is unknown[] => Array.isArray(v);

When it happens

Trigger: The loader hands the native module an object/record instead of the indexed array, typically because of a version mismatch between the loader JS and the compiled runtime module, or a custom hosting setup that constructs internals incorrectly.

Common situations: Mixing dotnet.js / dotnet.runtime.js / dotnet.native.js from different SDK builds; a custom host that builds the internals object manually and gets the shape wrong.

Related errors

• Expected internals to have RuntimeAPI
• Mismatched git hashes between loader and runtime. Loader: ${
• Mismatched git hashes between loader and runtime. Loader: ${
• Expected internals to be an array
• Expected internals to be an array

AI-assisted analysis of dotnet/runtime@290d5ab72c (2026-08-06). Data as JSON: /api/errors/d24ab1bca1fe8147. Report an issue: GitHub.