dotnet · pavelsavara · Dec 30, 2025 · Dec 23, 2025 · Dec 23, 2025 · Dec 23, 2025
diff --git a/eng/testing/tests.browser.targets b/eng/testing/tests.browser.targets
@@ -12,6 +12,7 @@
     <DisableBuildCompression>true</DisableBuildCompression>
     <PublishTrimmed>false</PublishTrimmed>
     <PublishTrimmed Condition="'$(RunAOTCompilation)' == 'true' or '$(TestTrimming)' == 'true'">true</PublishTrimmed>
+    <WasmTestSupport Condition="'$(RuntimeFlavor)' == 'CoreCLR'">true</WasmTestSupport>
     <_WasmInTreeDefaults>false</_WasmInTreeDefaults>
 
     <ResolveWasmOutputsDependsOn>

diff --git a/src/coreclr/hosts/corerun/CMakeLists.txt b/src/coreclr/hosts/corerun/CMakeLists.txt
@@ -69,13 +69,13 @@ else()
                 LINK_FLAGS "--js-library ${JS_SYSTEM_NATIVE_BROWSER} --js-library ${JS_SYSTEM_BROWSER_UTILS} --extern-post-js ${JS_CORE_RUN}"
                 RUNTIME_OUTPUT_DIRECTORY "${CMAKE_CURRENT_BINARY_DIR}")
             target_link_options(corerun PRIVATE
-                -sEXIT_RUNTIME=0
                 -sINITIAL_MEMORY=134217728
                 -sMAXIMUM_MEMORY=2147483648
                 -sALLOW_MEMORY_GROWTH=1
                 -sSTACK_SIZE=5MB
                 -sMODULARIZE=1
                 -sEXPORT_ES6=1
+                -sEXIT_RUNTIME=1
                 -sEXPORTED_RUNTIME_METHODS=ENV,${CMAKE_EMCC_EXPORTED_RUNTIME_METHODS}
                 -sEXPORTED_FUNCTIONS=_main,${CMAKE_EMCC_EXPORTED_FUNCTIONS}
                 -sEXPORT_NAME=createDotnetRuntime

@@ -125,6 +125,10 @@ interface DotnetHostBuilder {
      * Starts the runtime and returns promise of the API object.
      */
     create(): Promise<RuntimeAPI>;
+    /**
+     * @deprecated use runMain() or runMainAndExit() instead.
+     */
+    run(): Promise<number>;
     /**
      * Runs the Main() method of the application and exits the runtime.
      * You can provide "command line" arguments for the Main() method using
@@ -133,7 +137,14 @@ interface DotnetHostBuilder {
      * Note: after the runtime exits, it would reject all further calls to the API.
      * You can use runMain() if you want to keep the runtime alive.
      */
-    run(): Promise<number>;
+    runMainAndExit (): Promise<number>;
+    /**
+     * Runs the Main() method of the application and keeps the runtime alive.
+     * You can provide "command line" arguments for the Main() method using
+     * - dotnet.withApplicationArguments("A", "B", "C")
+     * - dotnet.withApplicationArgumentsFromQuery()
+     */
+    runMain (): Promise<number>;
 }
 type MonoConfig = {
     /**

@@ -15,7 +15,7 @@ export function is_runtime_running () {
 }
 
 export function assert_runtime_running () {
-    mono_assert(!is_exited(), () => `.NET runtime already exited with ${loaderHelpers.exitCode} ${loaderHelpers.exitReason}. You can use runtime.runMain() which doesn't exit the runtime.`);
+    mono_assert(!is_exited(), () => `.NET runtime already exited with ${loaderHelpers.exitCode} ${loaderHelpers.exitReason}. You can use dotnet.runMain() which doesn't exit the runtime.`);
     if (WasmEnableThreads && ENVIRONMENT_IS_WORKER) {
         mono_assert(runtimeHelpers.runtimeReady, "The WebWorker is not attached to the runtime. See https://github.com/dotnet/runtime/blob/main/src/mono/wasm/threads.md#JS-interop-on-dedicated-threads");
     } else {
@@ -243,6 +243,7 @@ function abort_promises (reason: any) {
     }
 }
 
+// https://github.com/dotnet/xharness/blob/799df8d4c86ff50c83b7a57df9e3691eeab813ec/src/Microsoft.DotNet.XHarness.CLI/Commands/WASM/Browser/WasmBrowserTestRunner.cs#L122-L141
 function appendElementOnExit (exit_code: number) {
     if (ENVIRONMENT_IS_WEB && !ENVIRONMENT_IS_WORKER && loaderHelpers.config && loaderHelpers.config.appendElementOnExit && document) {
         //Tell xharness WasmBrowserTestRunner what was the exit code

@@ -249,7 +249,11 @@ export class HostBuilder implements DotnetHostBuilder {
         }
     }
 
-    async run (): Promise<number> {
+    run (): Promise<number> {
+        return this.runMainAndExit();
+    }
+
+    async runMainAndExit (): Promise<number> {
         try {
             mono_assert(emscriptenModule.config, "Null moduleConfig.config");
             if (!this.instance) {
@@ -261,6 +265,19 @@ export class HostBuilder implements DotnetHostBuilder {
             throw err;
         }
     }
+
+    async runMain (): Promise<number> {
+        try {
+            mono_assert(emscriptenModule.config, "Null moduleConfig.config");
+            if (!this.instance) {
+                await this.create();
+            }
+            return this.instance!.runMain();
+        } catch (err) {
+            mono_exit(1, err);
+            throw err;
+        }
+    }
 }
 
 export async function createApi (): Promise<RuntimeAPI> {

@@ -74,6 +74,11 @@ export interface DotnetHostBuilder {
      */
     create(): Promise<RuntimeAPI>;
 
+    /**
+     * @deprecated use runMain() or runMainAndExit() instead.
+     */
+    run(): Promise<number>;
+
     /**
      * Runs the Main() method of the application and exits the runtime.
      * You can provide "command line" arguments for the Main() method using
@@ -82,7 +87,15 @@ export interface DotnetHostBuilder {
      * Note: after the runtime exits, it would reject all further calls to the API.
      * You can use runMain() if you want to keep the runtime alive.
      */
-    run(): Promise<number>;
+
+    runMainAndExit (): Promise<number>;
+    /**
+     * Runs the Main() method of the application and keeps the runtime alive.
+     * You can provide "command line" arguments for the Main() method using
+     * - dotnet.withApplicationArguments("A", "B", "C")
+     * - dotnet.withApplicationArgumentsFromQuery()
+     */
+    runMain (): Promise<number>;
 }
 
 // when adding new fields, please consider if it should be impacting the config hash. If not, please drop it in the getCacheKey()

@@ -119,7 +119,7 @@ function initRunArgs(runArgs) {
     runArgs.debugging = runArgs.debugging === undefined ? false : runArgs.debugging;
     runArgs.configSrc = runArgs.configSrc === undefined ? './_framework/dotnet.boot.js' : runArgs.configSrc;
     // default'ing to true for tests, unless debugging
-    runArgs.forwardConsole = runArgs.forwardConsole === undefined ? !runArgs.debugging : runArgs.forwardConsole;
+    runArgs.forwardConsole = runArgs.forwardConsole === undefined ? (isFirefox && !runArgs.debugging) : runArgs.forwardConsole;
     runArgs.interpreterPgo = runArgs.interpreterPgo === undefined ? false : runArgs.interpreterPgo;
 
     return runArgs;

@@ -304,6 +304,8 @@ Copyright (c) .NET Foundation. All rights reserved.
     <PropertyGroup>
       <_WasmEmitSourceMapBuild>$(WasmEmitSourceMap)</_WasmEmitSourceMapBuild>
       <_WasmEmitSourceMapBuild Condition="'$(_WasmEmitSourceMapBuild)' == ''">true</_WasmEmitSourceMapBuild>
+      <_WasmEmitDiagnosticModuleBuild Condition="'$(EnableDiagnostics)' == 'true' or '$(WasmEmitSymbolMap)' == 'true' or '$(WasmTestSupport)' == 'true'">true</_WasmEmitDiagnosticModuleBuild>
+      <_WasmEmitDiagnosticModuleBuild Condition="'$(_WasmEmitDiagnosticModuleBuild)' == ''">false</_WasmEmitDiagnosticModuleBuild>
     </PropertyGroup>
 
     <ComputeWasmBuildAssets
@@ -319,7 +321,7 @@ Copyright (c) .NET Foundation. All rights reserved.
       CopySymbols="$(_WasmCopyOutputSymbolsToOutputDirectory)"
       OutputPath="$(OutputPath)"
       EnableThreads="$(_WasmEnableThreads)"
-      EnableDiagnostics="$(EnableDiagnostics)"
+      EnableDiagnostics="$(_WasmEmitDiagnosticModuleBuild)"
       EmitSourceMap="$(_WasmEmitSourceMapBuild)"
       FingerprintAssets="$(_WasmFingerprintAssets)"
       FingerprintDotnetJs="$(_WasmFingerprintDotnetJs)"
@@ -472,7 +474,13 @@ Copyright (c) .NET Foundation. All rights reserved.
       IsAot="$(RunAOTCompilation)"
       IsMultiThreaded="$(WasmEnableThreads)"
       FingerprintAssets="$(_WasmFingerprintAssets)"
-      BundlerFriendly="$(_WasmBundlerFriendlyBootConfig)" />
+      BundlerFriendly="$(_WasmBundlerFriendlyBootConfig)"
+      ExitOnUnhandledError="$(WasmTestExitOnUnhandledError)"
+      AppendElementOnExit="$(WasmTestAppendElementOnExit)"
+      LogExitCode="$(WasmTestLogExitCode)"
+      AsyncFlushOnExit="$(WasmTestAsyncFlushOnExit)"
+      ForwardConsole="$(WasmTestForwardConsole)"
+      />
 
     <ItemGroup>
       <FileWrites Include="$(_WasmBuildBootJsonPath)" />
@@ -651,6 +659,8 @@ Copyright (c) .NET Foundation. All rights reserved.
     <PropertyGroup>
       <_WasmEmitSourceMapPublish>$(WasmEmitSourceMap)</_WasmEmitSourceMapPublish>
       <_WasmEmitSourceMapPublish Condition="'$(_WasmEmitSourceMapPublish)' == ''">false</_WasmEmitSourceMapPublish>
+      <_WasmEmitDiagnosticModulePublish Condition="'$(EnableDiagnostics)' == 'true' or '$(WasmEmitSymbolMap)' == 'true' or '$(WasmTestSupport)' == 'true'">true</_WasmEmitDiagnosticModulePublish>
+      <_WasmEmitDiagnosticModulePublish Condition="'$(_WasmEmitDiagnosticModulePublish)' == ''">false</_WasmEmitDiagnosticModulePublish>
     </PropertyGroup>
 
     <ItemGroup Condition="@(WasmAssembliesFinal->Count()) == 0 or '$(TargetFrameworkVersion)' == 'v6.0'">
@@ -677,7 +687,7 @@ Copyright (c) .NET Foundation. All rights reserved.
       CopySymbols="$(CopyOutputSymbolsToPublishDirectory)"
       ExistingAssets="@(_WasmPublishPrefilteredAssets)"
       EnableThreads="$(_WasmEnableThreads)"
-      EnableDiagnostics="$(EnableDiagnostics)"
+      EnableDiagnostics="$(_WasmEmitDiagnosticModulePublish)"
       EmitSourceMap="$(_WasmEmitSourceMapPublish)"
       IsWebCilEnabled="$(_WasmEnableWebcil)"
       FingerprintAssets="$(_WasmFingerprintAssets)"
@@ -885,7 +895,13 @@ Copyright (c) .NET Foundation. All rights reserved.
       IsAot="$(RunAOTCompilation)"
       IsMultiThreaded="$(WasmEnableThreads)"
       FingerprintAssets="$(_WasmFingerprintAssets)"
-      BundlerFriendly="$(_WasmBundlerFriendlyBootConfig)" />
+      BundlerFriendly="$(_WasmBundlerFriendlyBootConfig)"
+      ExitOnUnhandledError="$(WasmTestExitOnUnhandledError)"
+      AppendElementOnExit="$(WasmTestAppendElementOnExit)"
+      LogExitCode="$(WasmTestLogExitCode)"
+      AsyncFlushOnExit="$(WasmTestAsyncFlushOnExit)"
+      ForwardConsole="$(WasmTestForwardConsole)"
+      />
 
     <ItemGroup>
       <FileWrites Include="$(IntermediateOutputPath)$(_WasmPublishBootConfigFileName)" />

@@ -46,6 +46,12 @@
     <NestedBuildProperty Include="WasmEnableWebcil" />
     <NestedBuildProperty Include="EnableAggressiveTrimming" />
     <NestedBuildProperty Include="TrimMode" />
+    <NestedBuildProperty Include="WasmTestSupport" />
+    <NestedBuildProperty Include="WasmTestExitOnUnhandledError" />
+    <NestedBuildProperty Include="WasmTestAppendElementOnExit" />
+    <NestedBuildProperty Include="WasmTestLogExitCode" />
+    <NestedBuildProperty Include="WasmTestAsyncFlushOnExit" />
+    <NestedBuildProperty Include="WasmTestForwardConsole" />
   </ItemGroup>
 
   <Target Name="BuildSampleInTree"

@@ -139,6 +139,16 @@ public BuildEnvironment()
                 EnvVars["WasmFingerprintAssets"] = "false";
             }
 
+            if (EnvironmentVariables.RuntimeFlavor == "CoreCLR")
+            {
+                EnvVars["WasmTestSupport"] = "true";
+                EnvVars["WasmTestExitOnUnhandledError"] = "true";
+                EnvVars["WasmTestLogExitCode"] = "true";
+                // EnvVars["WasmTestForwardConsole"] = "true"; // only necessary for firefox, because chromedriver supports it natively
+                // EnvVars["WasmTestAsyncFlushOnExit"] = "true"; // only necessary for old nodejs versions
+                // EnvVars["WasmTestAppendElementOnExit"] = "true"; // only used by xharness // https://github.com/dotnet/xharness/blob/799df8d4c86ff50c83b7a57df9e3691eeab813ec/src/Microsoft.DotNet.XHarness.CLI/Commands/WASM/Browser/WasmBrowserTestRunner.cs#L122-L141
+            }
+
             DotNet = Path.Combine(sdkForWorkloadPath!, "dotnet");
             if (RuntimeInformation.IsOSPlatform(OSPlatform.Windows))
                 DotNet += ".exe";

@@ -79,7 +79,7 @@ private async Task BrowserRunTwiceWithAndThenWithoutBuildAsync(Configuration con
         {
             ProjectInfo info = CreateWasmTemplateProject(Template.WasmBrowser, config, aot: false, "browser", extraProperties: extraProperties);
             UpdateBrowserProgramFile();
-            UpdateBrowserMainJs();
+            UpdateBrowserMainJs(forwardConsole: true);
 
             string workingDir = runOutsideProjectDirectory ? BuildEnvironment.TmpPath : _projectDir;
             string projectFilePath = info.ProjectFilePath;
@@ -169,7 +169,7 @@ public async Task BuildAndRunForDifferentOutputPaths(Configuration config, bool
         {
             ProjectInfo info = CreateWasmTemplateProject(Template.WasmBrowser, config, aot: false);
             UpdateBrowserProgramFile();
-            UpdateBrowserMainJs();
+            UpdateBrowserMainJs(forwardConsole: true);
 
             bool isPublish = false;
             string projectDirectory = Path.GetDirectoryName(info.ProjectFilePath) ?? "";

@@ -141,9 +141,16 @@ protected ProjectInfo CopyTestAsset(
                   <LatestRuntimeFrameworkVersion>11.0.0-{{versionSuffix}}</LatestRuntimeFrameworkVersion>
                   <RuntimePackRuntimeIdentifiers>browser-wasm;%(RuntimePackRuntimeIdentifiers)</RuntimePackRuntimeIdentifiers>
                 </KnownFrameworkReference>
-                <KnownWebAssemblySdkPack Update="Microsoft.NET.Sdk.WebAssembly.Pack">
-                  <WebAssemblySdkPackVersion>11.0.0-{{versionSuffix}}</WebAssemblySdkPackVersion>
-                </KnownWebAssemblySdkPack>
+            """;
+            insertAtEnd +=
+            $$"""
+                <Target Name="_UpdateKnownWebAssemblySdkPack" BeforeTargets="ProcessFrameworkReferences">
+                    <ItemGroup>
+                    <KnownWebAssemblySdkPack Update="@(KnownWebAssemblySdkPack)">
+                        <WebAssemblySdkPackVersion Condition="'%(KnownWebAssemblySdkPack.TargetFramework)' == 'net11.0'">11.0.0-{{versionSuffix}}</WebAssemblySdkPackVersion>
+                    </KnownWebAssemblySdkPack>
+                    </ItemGroup>
+                </Target>
             """;
         }
 
@@ -303,7 +310,7 @@ protected void DeleteFile(string pathRelativeToProjectDir)
         }
     }
 
-    protected void UpdateBrowserMainJs(string? targetFramework = null, string runtimeAssetsRelativePath = DefaultRuntimeAssetsRelativePath)
+    protected void UpdateBrowserMainJs(string? targetFramework = null, string runtimeAssetsRelativePath = DefaultRuntimeAssetsRelativePath, bool forwardConsole = false)
     {
         targetFramework ??= DefaultTargetFramework;
         string mainJsPath = Path.Combine(_projectDir, "wwwroot", "main.js");
@@ -314,13 +321,20 @@ protected void UpdateBrowserMainJs(string? targetFramework = null, string runtim
             mainJsContent,
             ".create()",
             (targetFrameworkVersion.Major >= 8)
-                    ? ".withConfig({ forwardConsole: true, appendElementOnExit: true, logExitCode: true, exitOnUnhandledError: true }).create()"
-                    : ".withConfig({ forwardConsole: true, appendElementOnExit: true, logExitCode: true }).create()"
+                    ? $".withConfig({{ forwardConsole: {forwardConsole.ToString().ToLowerInvariant()}, appendElementOnExit: true, logExitCode: true, exitOnUnhandledError: true }}).create()"
+                    : ".withConfig({ appendElementOnExit: true, logExitCode: true }).create()"
             );
 
-        // dotnet.run() is used instead of runMain() in net9.0+
-        if (targetFrameworkVersion.Major >= 9)
+        if (targetFrameworkVersion.Major >= 11)
+        {
+            // runMainAndExit() is used instead of runMain() in net11.0+
+            updatedMainJsContent = StringReplaceWithAssert(updatedMainJsContent, "runMain()", "runMainAndExit()");
+        }
+        else if (targetFrameworkVersion.Major >= 9)
+        {
+            // dotnet.run() is used instead of runMain() in net9.0+
             updatedMainJsContent = StringReplaceWithAssert(updatedMainJsContent, "runMain()", "dotnet.run()");
+        }
 
         updatedMainJsContent = StringReplaceWithAssert(updatedMainJsContent, "from './_framework/dotnet.js'", $"from '{runtimeAssetsRelativePath}dotnet.js'");
 

@@ -13,7 +13,7 @@ public async Task RunMainOnly()
         Configuration config = Configuration.Debug;
 
         ProjectInfo info = CopyTestAsset(config, false, TestAsset.WasmBrowserRunMainOnly, $"WasmBrowserRunMainOnly");
-        var (_, buildOutput) = PublishProject(info, config);
+        var (_, buildOutput) = PublishProject(info, config, new PublishOptions(AssertAppBundle: false, EnableDiagnostics: true));
 
         // ** MicrosoftNetCoreAppRuntimePackDir : '....microsoft.netcore.app.runtime.browser-wasm\11.0.0-dev'
         Assert.Contains("microsoft.netcore.app.runtime.browser-wasm", buildOutput);

@@ -65,7 +65,7 @@ private async Task RunAsync(ILoggerFactory loggerFactory, CancellationToken toke
         var runArgsJson = new RunArgumentsJson(applicationArguments: _args.AppArgs,
                                                runtimeArguments: _args.CommonConfig.RuntimeArguments,
                                                environmentVariables: envVars,
-                                               forwardConsoleToWS: _args.ForwardConsoleOutput ?? false,
+                                               forwardConsole: _args.ForwardConsoleOutput ?? false,
                                                debugging: _args.CommonConfig.Debugging);
         runArgsJson.Save(Path.Combine(_args.CommonConfig.AppPath, "runArgs.json"));
 

@@ -14,7 +14,7 @@ internal sealed record RunArgumentsJson(
     string[] applicationArguments,
     string[]? runtimeArguments = null,
     IDictionary<string, string>? environmentVariables = null,
-    bool forwardConsoleToWS = false,
+    bool forwardConsole = false,
     bool debugging = false
 )
 {

@@ -3,7 +3,7 @@
 
 import { dotnet } from './_framework/dotnet.js'
 
-const { setModuleImports, getAssemblyExports, getConfig, runMain } = await dotnet
+const { setModuleImports, getAssemblyExports, getConfig } = await dotnet
     .withApplicationArguments("start")
     .create();
 
@@ -29,4 +29,4 @@ pauseButton.addEventListener('click', e => {
 });
 
 // run the C# Main() method and keep the runtime process running and executing further API calls
-await runMain();
+await dotnet.runMain();
@@ -17,5 +17,7 @@ public static void Run()
         // In the test case it is done in the JS before call to this method
         var text = JsonSerializer.Serialize(new Person("John", "Doe"), PersonJsonSerializerContext.Default.Person);
         TestOutput.WriteLine(text);
+        Console.WriteLine("LazyLoadingTest done");
+        Console.Out.Flush();
     }
 }
@@ -371,5 +371,7 @@ try {
             break;
     }
 } catch (e) {
-    exit(1, e);
+    if (e.name != "ExitStatus") {
+        exit(1, e);
+    }
 }
@@ -14,6 +14,7 @@ public partial class Foo
     public static int Bar()
     {
         Console.WriteLine("Hello from Foo.Bar!");
+        Console.Out.Flush();
         return 42;
     }
 }
@@ -3,12 +3,4 @@
 
 import { dotnet } from './_framework/dotnet.js'
 
-await dotnet.create();
-
-try {
-    await dotnet.run();
-    console.log("WASM EXIT 0");
-} catch (err) {
-    console.error(err);
-    console.log("WASM EXIT 1");
-}
+await dotnet.runMainAndExit();