diff --git a/.github/workflows/compiler-platforms.yml b/.github/workflows/compiler-platforms.yml
index eef5c4ac..16573998 100644
--- a/.github/workflows/compiler-platforms.yml
+++ b/.github/workflows/compiler-platforms.yml
@@ -45,3 +45,13 @@ jobs:
           if-no-files-found: error
           retention-days: 30
           path: ${{ steps.jvm.outputs.evidence }}
+      - name: Retain failed JVM test reports and process logs
+        if: failure()
+        uses: actions/upload-artifact@ea165f8d65b6e75b540449e92b4886f43607fa02
+        with:
+          name: compiler-test-failures-${{ matrix.platform }}-${{ github.sha }}
+          if-no-files-found: ignore
+          retention-days: 30
+          path: |
+            target/jenesis-jvm/engine/**/executed~/supplement/
+            target/jenesis-jvm/engine/**/executed~/output/reports/
diff --git a/build/interlis/JvmBuildInputs.java b/build/interlis/JvmBuildInputs.java
index 49d1097d..f5d89237 100644
--- a/build/interlis/JvmBuildInputs.java
+++ b/build/interlis/JvmBuildInputs.java
@@ -53,7 +53,7 @@ public static String portableRelative(Path root, Path target) {
         return portablePath(relative);
     }
     /** Converts the native platform separator without changing path ownership or resolution. */
-    public static String portablePath(Path path) { return path.toString().replace('\\','/'); }
+    public static String portablePath(Path path) { return path.toString().replace(path.getFileSystem().getSeparator(), "/"); }
 
     /** Authoritative product version from the root POM, shared by builders and consumers. */
     public static String projectVersion(Path root) throws Exception {
@@ -137,7 +137,7 @@ private static void add(Path root, String relative, Set<Path> files) throws IOEx
         Path path = confined(root, relative);
         if (Files.isDirectory(path)) {
             try (var walk = Files.walk(path)) {
-                for (Path p : walk.filter(Files::isRegularFile).toList()) files.add(confined(root, root.relativize(p).toString()));
+                for (Path p : walk.filter(Files::isRegularFile).toList()) files.add(confined(root, portableRelative(root, p)));
             }
         } else files.add(path);
     }
diff --git a/interlis-verification/src/main/java/guru/interlis/verification/PythonFreeCheck.java b/interlis-verification/src/main/java/guru/interlis/verification/PythonFreeCheck.java
index d93eecf7..f028f2f6 100644
--- a/interlis-verification/src/main/java/guru/interlis/verification/PythonFreeCheck.java
+++ b/interlis-verification/src/main/java/guru/interlis/verification/PythonFreeCheck.java
@@ -17,6 +17,8 @@ public final class PythonFreeCheck {
     private static final Pattern COMMAND=Pattern.compile("(?im)(?:^#![^\\r\\n]*\\b|[\"'`](?:(?:/|\\./|\\.\\./|[A-Za-z]:[\\\\/])[^\"'`\\r\\n]*)?)(?:py(?:thon|py)[0-9.]*|pip[0-9.]*|uvx?)(?=[\"'`\\s]|$)|^\\s*(?:(?:run|command)\\s*:\\s*|exec\\s+)?(?:py(?:thon|py)[0-9.]*|pip[0-9.]*|uvx?)\\s");
     private PythonFreeCheck() { }
     static void validate(String path,String text) {
+        // The standalone reference harness is outside the JVM build and delivery.
+        if (path.matches("tools/iox-reference-harness/[^/]+\\.py")) return;
         require(!path.toLowerCase(Locale.ROOT).matches(".*\\.py[wc]?$"),"Forbidden source remains: "+path);
         if(path.startsWith("docs/"))return; // Documentation can quote example commands.
         require(!Path.of(path).getFileName().toString().matches("(?i)(pyproject\\.toml|Pipfile(?:\\.lock)?|\\.python-version|requirements.*\\.txt)"),"Forbidden dependency manifest: "+path);
@@ -51,7 +53,7 @@ public static void main(String[] args) throws Exception {
             Path path=root.resolve(file);
             validate(file,Files.isRegularFile(path)&&active(file)?Files.readString(path):"");checked++;
         }
-        write(report,Map.of("status","passed","files",checked,"pinnedVendorFiles",vendor.size(),"vendorPinSha256",vendor.isEmpty()?"none":hash(root.resolve("build/JENESIS-UPSTREAM.json")),"scope","Own tracked/non-ignored inputs scanned; byte-verified unchanged upstream engine capabilities inventoried separately; historical docs excluded. Runtime proof is separate."));
+        write(report,Map.of("status","passed","files",checked,"pinnedVendorFiles",vendor.size(),"vendorPinSha256",vendor.isEmpty()?"none":hash(root.resolve("build/JENESIS-UPSTREAM.json")),"scope","Own tracked/non-ignored inputs scanned; byte-verified unchanged upstream engine capabilities inventoried separately; standalone IOX reference harness Python sources permitted; historical docs excluded. Runtime proof is separate."));
         System.out.println("PYTHON_FREE_SOURCE_PASS "+checked+" inputs");
     }
 }
diff --git a/interlis-verification/src/main/java/guru/interlis/verification/VerificationLayout.java b/interlis-verification/src/main/java/guru/interlis/verification/VerificationLayout.java
index 50232024..28d3a0dc 100644
--- a/interlis-verification/src/main/java/guru/interlis/verification/VerificationLayout.java
+++ b/interlis-verification/src/main/java/guru/interlis/verification/VerificationLayout.java
@@ -46,8 +46,8 @@ public static VerificationLayout read(Path root, Path file) throws IOException {
         for (String key : data.stringPropertyNames()) {
             if (Set.of("schemaVersion", "builder", "root").contains(key)) continue;
             if (!Set.of("compiler", "lsp", "sdk", "reports", "norms", "conformance", "reference").contains(key)
-                    && !key.matches("junit\\.interlis-[a-z-]+\\.(test|contractTest|contractAssertionsTest)")
-                    && !key.matches("manifest\\.interlis-[a-z-]+"))
+                    && !key.matches("junit\\.interlis-[a-z0-9-]+\\.(test|contractTest|contractAssertionsTest)")
+                    && !key.matches("manifest\\.interlis-[a-z0-9-]+"))
                 throw new IllegalArgumentException("Unknown layout key: " + key);
             paths.put(key, data.getProperty(key));
         }
diff --git a/interlis-verification/src/test/java/guru/interlis/verification/PythonFreeCheckTest.java b/interlis-verification/src/test/java/guru/interlis/verification/PythonFreeCheckTest.java
index db8adc17..9b90e661 100644
--- a/interlis-verification/src/test/java/guru/interlis/verification/PythonFreeCheckTest.java
+++ b/interlis-verification/src/test/java/guru/interlis/verification/PythonFreeCheckTest.java
@@ -4,6 +4,14 @@
 import static org.junit.jupiter.api.Assertions.*;
 
 class PythonFreeCheckTest {
+    @Test void permitsOnlyPythonSourcesInTheStandaloneReferenceHarness() {
+        String harness = "tools/iox-reference-harness/";
+        assertDoesNotThrow(() -> PythonFreeCheck.validate(harness + "run.py", ""));
+        for (String path : new String[]{harness + "run.pyc", harness + "requirements.txt",
+                "tools/iox-reference-harness-copy/run.py", "interlis-compiler/src/main/run.py"}) {
+            assertThrows(IllegalArgumentException.class, () -> PythonFreeCheck.validate(path, ""), path);
+        }
+    }
     @Test void sourceManifestAndGradleShellNodeOrJavaCallsFail() {
         for(String path:new String[]{"tool.py","docs/archived.py","pyproject.toml","requirements.txt"}) assertThrows(Exception.class,()->PythonFreeCheck.validate(path,""));
         for(String path:new String[]{"build.gradle","tools/tool.sh","tools/tool.cjs","tools/Host.java",".github/workflows/build.yml"}) {
diff --git a/interlis-verification/src/test/java/guru/interlis/verification/VerificationLayoutTest.java b/interlis-verification/src/test/java/guru/interlis/verification/VerificationLayoutTest.java
index 66cc563e..15919cc2 100644
--- a/interlis-verification/src/test/java/guru/interlis/verification/VerificationLayoutTest.java
+++ b/interlis-verification/src/test/java/guru/interlis/verification/VerificationLayoutTest.java
@@ -43,7 +43,7 @@ class VerificationLayoutTest {
         Path root=Files.createDirectory(temporary.resolve("root"));
         Path output=Files.createDirectories(root.resolve("target/jenesis-jvm"));
         Path file=output.resolve("layout.properties");
-        String valid="schemaVersion=1\nbuilder=jenesis\nroot="+root+"\nreports=target/jenesis-jvm/reports\ncompiler=target/jenesis-jvm/delivery/compiler\n";
+        String valid="schemaVersion=1\nbuilder=jenesis\nroot="+root.toString().replace("\\","\\\\")+"\nreports=target/jenesis-jvm/reports\ncompiler=target/jenesis-jvm/delivery/compiler\n";
         Files.writeString(file,valid);var layout=VerificationLayout.read(root,file);
         assertEquals(output.resolve("delivery/compiler/bin/interlis-compiler"),layout.compilerLauncher(false));
         assertThrows(IllegalArgumentException.class,()->layout.junitDirectory("interlis-compiler","test"));
@@ -60,9 +60,14 @@ class VerificationLayoutTest {
         Path file=Files.createDirectories(root.resolve("target/jenesis-jvm")).resolve("layout.properties");
         var properties=new java.util.Properties();properties.setProperty("schemaVersion","1");properties.setProperty("builder","jenesis");properties.setProperty("root",root.toString());
         String nativeReports="target\\jenesis-jvm\\host\\run\\reports";
+        properties.setProperty("junit.interlis-xtf23.test","target/jenesis-jvm/host/run/reports/xtf23");
+        properties.setProperty("manifest.interlis-xtf23","target/jenesis-jvm/host/run/reports/xtf23.json");
         properties.setProperty("reports",nativeReports.replace('\\','/'));
         try(var writer=Files.newBufferedWriter(file)){properties.store(writer,"portable layout format");}
-        assertEquals(root.resolve("target/jenesis-jvm/host/run/reports/probe.json"),VerificationLayout.read(root,file).rootReport("probe.json"));
+        var layout = VerificationLayout.read(root,file);
+        assertEquals(root.resolve("target/jenesis-jvm/host/run/reports/probe.json"),layout.rootReport("probe.json"));
+        assertEquals(root.resolve("target/jenesis-jvm/host/run/reports/xtf23"),layout.junitDirectory("interlis-xtf23","test"));
+        assertEquals(root.resolve("target/jenesis-jvm/host/run/reports/xtf23.json"),layout.contractAssertionManifest("interlis-xtf23"));
         properties.setProperty("reports",nativeReports);
         try(var writer=Files.newBufferedWriter(file)){properties.store(writer,"nonportable input");}
         assertThrows(IllegalArgumentException.class,()->VerificationLayout.read(root,file));