diff --git a/tests/Beam/Fable.Tests.Beam.fsproj b/tests/Beam/Fable.Tests.Beam.fsproj
index 19bed181ad..10dbefd827 100644
--- a/tests/Beam/Fable.Tests.Beam.fsproj
+++ b/tests/Beam/Fable.Tests.Beam.fsproj
@@ -1,6 +1,13 @@
 <Project Sdk="Microsoft.NET.Sdk">
   <PropertyGroup>
     <OutputType>Exe</OutputType>
+    <!-- When Fable cracks the project it defines FABLE_COMPILER and runs CoreCompile,
+         which makes xunit.v3 attach its generated entry point and runner-reporter
+         source files. Those reference .NET runtime types and are irrelevant to the
+         transpiled output, so disable them for the Fable build only; on .NET xunit
+         still generates the test runner entry point. -->
+    <XunitAutoGeneratedEntryPoint Condition="'$(FABLE_COMPILER)' == 'True'">false</XunitAutoGeneratedEntryPoint>
+    <XunitRegisterBuiltInRunnerReporters Condition="'$(FABLE_COMPILER)' == 'True'">false</XunitRegisterBuiltInRunnerReporters>
     <TargetFramework>net10.0</TargetFramework>
     <RollForward>Major</RollForward>
     <IsPackable>false</IsPackable>
@@ -10,7 +17,7 @@
   </PropertyGroup>
   <ItemGroup>
     <PackageReference Include="Microsoft.NET.Test.Sdk" Version="18.3.0" />
-    <PackageReference Include="XUnit" Version="2.9.3" />
+    <PackageReference Include="xunit.v3" Version="3.2.2" />
     <PackageReference Include="xunit.runner.visualstudio" Version="3.1.5">
       <IncludeAssets>runtime; build; native; contentfiles; analyzers; buildtransitive</IncludeAssets>
       <PrivateAssets>all</PrivateAssets>
diff --git a/tests/Beam/Main.fs b/tests/Beam/Main.fs
index b00af3eaac..7cfe91c15e 100644
--- a/tests/Beam/Main.fs
+++ b/tests/Beam/Main.fs
@@ -2,5 +2,7 @@
 module Program
 ()
 #else
-module Program = let [<EntryPoint>] main _ = 0
+module Program
+// On .NET, xunit.v3 generates the test runner entry point automatically.
+()
 #endif
diff --git a/tests/Php/Fable.Tests.Php.fsproj b/tests/Php/Fable.Tests.Php.fsproj
index cf4454a014..da00f469da 100644
--- a/tests/Php/Fable.Tests.Php.fsproj
+++ b/tests/Php/Fable.Tests.Php.fsproj
@@ -1,5 +1,13 @@
 <Project Sdk="Microsoft.NET.Sdk">
   <PropertyGroup>
+    <OutputType>Exe</OutputType>
+    <!-- When Fable cracks the project it defines FABLE_COMPILER and runs CoreCompile,
+         which makes xunit.v3 attach its generated entry point and runner-reporter
+         source files. Those reference .NET runtime types and are irrelevant to the
+         transpiled output, so disable them for the Fable build only; on .NET xunit
+         still generates the test runner entry point. -->
+    <XunitAutoGeneratedEntryPoint Condition="'$(FABLE_COMPILER)' == 'True'">false</XunitAutoGeneratedEntryPoint>
+    <XunitRegisterBuiltInRunnerReporters Condition="'$(FABLE_COMPILER)' == 'True'">false</XunitRegisterBuiltInRunnerReporters>
     <TargetFramework>net10.0</TargetFramework>
     <RollForward>Major</RollForward>
     <IsPackable>false</IsPackable>
@@ -8,7 +16,7 @@
   </PropertyGroup>
   <ItemGroup>
     <PackageReference Include="Microsoft.NET.Test.Sdk" Version="18.3.0" />
-    <PackageReference Include="XUnit" Version="2.9.3" />
+    <PackageReference Include="xunit.v3" Version="3.2.2" />
     <PackageReference Include="xunit.runner.visualstudio" Version="3.1.5">
       <IncludeAssets>runtime; build; native; contentfiles; analyzers; buildtransitive</IncludeAssets>
       <PrivateAssets>all</PrivateAssets>
diff --git a/tests/Php/Main.fs b/tests/Php/Main.fs
index ae5f6f6959..d54c0fa690 100644
--- a/tests/Php/Main.fs
+++ b/tests/Php/Main.fs
@@ -2,5 +2,7 @@
 module Program
 ()
 #else
-module Program = let [<EntryPoint>] main _ = 0
+module Program
+// On .NET, xunit.v3 generates the test runner entry point automatically.
+()
 #endif
\ No newline at end of file
diff --git a/tests/Python/Fable.Tests.Python.fsproj b/tests/Python/Fable.Tests.Python.fsproj
index 0bf797f75f..d6b037022f 100644
--- a/tests/Python/Fable.Tests.Python.fsproj
+++ b/tests/Python/Fable.Tests.Python.fsproj
@@ -1,6 +1,13 @@
 <Project Sdk="Microsoft.NET.Sdk">
   <PropertyGroup>
     <OutputType>Exe</OutputType>
+    <!-- When Fable cracks the project it defines FABLE_COMPILER and runs CoreCompile,
+         which makes xunit.v3 attach its generated entry point and runner-reporter
+         source files. Those reference .NET runtime types and are irrelevant to the
+         transpiled output, so disable them for the Fable build only; on .NET xunit
+         still generates the test runner entry point. -->
+    <XunitAutoGeneratedEntryPoint Condition="'$(FABLE_COMPILER)' == 'True'">false</XunitAutoGeneratedEntryPoint>
+    <XunitRegisterBuiltInRunnerReporters Condition="'$(FABLE_COMPILER)' == 'True'">false</XunitRegisterBuiltInRunnerReporters>
     <TargetFramework>net10.0</TargetFramework>
     <RollForward>Major</RollForward>
     <IsPackable>false</IsPackable>
@@ -10,7 +17,7 @@
   </PropertyGroup>
   <ItemGroup>
     <PackageReference Include="Microsoft.NET.Test.Sdk" Version="18.6.0" />
-    <PackageReference Include="XUnit" Version="2.9.3" />
+    <PackageReference Include="xunit.v3" Version="3.2.2" />
     <PackageReference Include="xunit.runner.visualstudio" Version="3.1.5">
       <IncludeAssets>runtime; build; native; contentfiles; analyzers; buildtransitive</IncludeAssets>
       <PrivateAssets>all</PrivateAssets>
@@ -22,6 +29,13 @@
   <ItemGroup>
     <ProjectReference Include="../../src/Fable.Core/Fable.Core.fsproj" />
   </ItemGroup>
+  <ItemGroup>
+    <!-- Run xunit serially: several MailboxProcessor/async tests assert from a
+         fire-and-forget `Async.StartImmediate`, whose continuation can run after
+         its test collection is torn down. xunit.v3 reports such background-thread
+         exceptions as catastrophic (v2 ignored them), which fails on Windows. -->
+    <Content Include="xunit.runner.json" CopyToOutputDirectory="PreserveNewest" />
+  </ItemGroup>
   <ItemGroup>
     <Compile Include="../Js/Main/Globs/*.fs" />
     <Compile Include="Util.fs" />
diff --git a/tests/Python/Main.fs b/tests/Python/Main.fs
index ae5f6f6959..d54c0fa690 100644
--- a/tests/Python/Main.fs
+++ b/tests/Python/Main.fs
@@ -2,5 +2,7 @@
 module Program
 ()
 #else
-module Program = let [<EntryPoint>] main _ = 0
+module Program
+// On .NET, xunit.v3 generates the test runner entry point automatically.
+()
 #endif
\ No newline at end of file
diff --git a/tests/Python/xunit.runner.json b/tests/Python/xunit.runner.json
new file mode 100644
index 0000000000..8641732346
--- /dev/null
+++ b/tests/Python/xunit.runner.json
@@ -0,0 +1,5 @@
+{
+  "$schema": "https://xunit.net/schema/current/xunit.runner.schema.json",
+  "parallelizeTestCollections": false,
+  "maxParallelThreads": 1
+}
diff --git a/tests/Rust/Fable.Tests.Rust.fsproj b/tests/Rust/Fable.Tests.Rust.fsproj
index 5bc246aac9..69b26e98e3 100644
--- a/tests/Rust/Fable.Tests.Rust.fsproj
+++ b/tests/Rust/Fable.Tests.Rust.fsproj
@@ -1,5 +1,14 @@
 <Project Sdk="Microsoft.NET.Sdk">
   <PropertyGroup>
+    <OutputType>Exe</OutputType>
+    <!-- When Fable cracks the project it defines FABLE_COMPILER and runs CoreCompile,
+         which makes xunit.v3 attach its generated entry point and runner-reporter
+         source files after our own files. That breaks transpilation (F# requires the
+         entry point in tests/src/main.fs to be the last declaration, and those xunit
+         sources reference runtime types Fable can't transpile). Disable them for the
+         Fable build only; on .NET xunit still generates the test runner entry point. -->
+    <XunitAutoGeneratedEntryPoint Condition="'$(FABLE_COMPILER)' == 'True'">false</XunitAutoGeneratedEntryPoint>
+    <XunitRegisterBuiltInRunnerReporters Condition="'$(FABLE_COMPILER)' == 'True'">false</XunitRegisterBuiltInRunnerReporters>
     <TargetFramework>net10.0</TargetFramework>
     <RollForward>Major</RollForward>
     <IsPackable>false</IsPackable>
@@ -8,7 +17,7 @@
   </PropertyGroup>
   <ItemGroup>
     <PackageReference Include="Microsoft.NET.Test.Sdk" Version="18.6.0" />
-    <PackageReference Include="XUnit" Version="2.9.3" />
+    <PackageReference Include="xunit.v3" Version="3.2.2" />
     <PackageReference Include="xunit.runner.visualstudio" Version="3.1.5">
       <IncludeAssets>runtime; build; native; contentfiles; analyzers; buildtransitive</IncludeAssets>
       <PrivateAssets>all</PrivateAssets>
diff --git a/tests/Rust/tests/src/main.fs b/tests/Rust/tests/src/main.fs
index 6a938fa462..ddaf02e64b 100644
--- a/tests/Rust/tests/src/main.fs
+++ b/tests/Rust/tests/src/main.fs
@@ -7,5 +7,9 @@ let _imports() =
     ()
 
 // [<OuterAttr("cfg", [|"not(feature = \"no_std\")"|])>]
+#if FABLE_COMPILER
+// Rust needs a `fn main`, so emit the entry point when transpiling. On .NET,
+// xunit.v3 generates the test runner entry point instead (see the .fsproj).
 [<EntryPoint>]
 let main _args = 0
+#endif