diff --git a/test/fixtures/litert_lm/c_api_version.c b/test/fixtures/litert_lm/c_api_version.c
index df782fa95..622eeb68d 100644
--- a/test/fixtures/litert_lm/c_api_version.c
+++ b/test/fixtures/litert_lm/c_api_version.c
@@ -33,3 +33,11 @@ int litert_lm_native_in_process_litert_abi_version(void) {
 // A missing gate must fail the test process before an incompatible call can
 // accidentally look like a supported engine initialization.
 void *litert_lm_engine_settings_create(void) { abort(); }
+
+#ifdef SMOKE_SYMBOLS
+void litert_lm_engine_create(void) { abort(); }
+void litert_lm_engine_delete(void) { abort(); }
+void stream_proxy_create(void) { abort(); }
+void stream_proxy_free_string(void) { abort(); }
+void stream_proxy_delete(void) { abort(); }
+#endif
diff --git a/test/unit/tooling/litert_lm_library_smoke_test.dart b/test/unit/tooling/litert_lm_library_smoke_test.dart
index e1d1911ba..abd06f420 100644
--- a/test/unit/tooling/litert_lm_library_smoke_test.dart
+++ b/test/unit/tooling/litert_lm_library_smoke_test.dart
@@ -201,4 +201,83 @@ void main() {
       throwsA(same(failure)),
     );
   });
+
+  group('in-process LiteRT marker', () {
+    final skip = Platform.isWindows ? 'compiles fixtures with cc' : null;
+    final libraries = <String, DynamicLibrary>{};
+    late Directory fixtures;
+
+    setUpAll(() {
+      if (skip != null) return;
+      fixtures = Directory.systemTemp.createTempSync('litert_marker_');
+      for (final (name, defines) in [
+        ('absent', ['-DSMOKE_SYMBOLS']),
+        ('zero', ['-DSMOKE_SYMBOLS', '-DIN_PROCESS_LITERT_ABI=0']),
+        ('one', ['-DSMOKE_SYMBOLS', '-DIN_PROCESS_LITERT_ABI=1']),
+      ]) {
+        final output = path.join(
+          fixtures.path,
+          '$name.${Platform.isMacOS ? 'dylib' : 'so'}',
+        );
+        final result = Process.runSync('cc', [
+          '-shared',
+          '-fPIC',
+          ...defines,
+          'test/fixtures/litert_lm/c_api_version.c',
+          '-o',
+          output,
+        ]);
+        expect(result.exitCode, 0, reason: '${result.stderr}');
+        libraries[name] = DynamicLibrary.open(output);
+      }
+    });
+
+    tearDownAll(() {
+      if (skip == null) fixtures.deleteSync(recursive: true);
+    });
+
+    test('desktop runtimes must export the marker with value 1', () {
+      for (final abi in [Abi.linuxX64, Abi.linuxArm64, Abi.windowsX64]) {
+        requireInProcessLiteRtMarker(libraries['one']!, abi);
+        for (final name in ['absent', 'zero']) {
+          expect(
+            () => requireInProcessLiteRtMarker(libraries[name]!, abi),
+            throwsA(
+              isA<StateError>().having(
+                (error) => error.message,
+                'message',
+                contains('litert_lm_native_in_process_litert_abi_version'),
+              ),
+            ),
+          );
+        }
+      }
+    }, skip: skip);
+
+    Map<String, Object?> runSmoke(String fixture, Abi abi) =>
+        runLiteRtLmLibrarySmoke(
+          abi: abi,
+          directory: null,
+          releaseTag: 'v0.19.1-2',
+          openLibrary: (_) => libraries[fixture]!,
+        );
+
+    test('the smoke run enforces the marker and reports its value', () {
+      for (final abi in [Abi.linuxX64, Abi.windowsX64]) {
+        expect(runSmoke('one', abi)['inProcessLiteRtAbi'], 1);
+        for (final name in ['absent', 'zero']) {
+          expect(() => runSmoke(name, abi), throwsStateError);
+        }
+      }
+    }, skip: skip);
+
+    test('the smoke run reports no marker where it is not required', () {
+      expect(runSmoke('absent', Abi.macosArm64)['inProcessLiteRtAbi'], isNull);
+    }, skip: skip);
+
+    test('Apple and Android runtimes are not required to export it', () {
+      requireInProcessLiteRtMarker(libraries['absent']!, Abi.macosArm64);
+      requireInProcessLiteRtMarker(libraries['absent']!, Abi.androidArm64);
+    }, skip: skip);
+  });
 }
diff --git a/tool/litert_lm_library_smoke.dart b/tool/litert_lm_library_smoke.dart
index 2c770ae7b..34796edb3 100644
--- a/tool/litert_lm_library_smoke.dart
+++ b/tool/litert_lm_library_smoke.dart
@@ -2,6 +2,8 @@ import 'dart:convert';
 import 'dart:ffi';
 import 'dart:io';
 
+import 'package:llamadart/src/backends/litert_lm/litert_lm_c_api_version.dart';
+import 'package:llamadart/src/backends/litert_lm/litert_lm_platform.dart';
 import 'package:llamadart/src/backends/litert_lm/litert_lm_runtime.dart'
     as runtime;
 import 'package:llamadart/src/hook/native_release_pins.dart';
@@ -26,19 +28,57 @@ void main() {
     return;
   }
 
+  print(
+    'RESULT litert_lm_library ${jsonEncode(runLiteRtLmLibrarySmoke(abi: Abi.current(), directory: Platform.environment[_litertLmLibDirEnv], releaseTag: liteRtLmReleaseTag))}',
+  );
+}
+
+/// Opens the runtime, checks its symbols and in-process LiteRT marker, and
+/// returns the RESULT payload.
+Map<String, Object?> runLiteRtLmLibrarySmoke({
+  required Abi abi,
+  required String? directory,
+  required String releaseTag,
+  DynamicLibrary Function(String)? openLibrary,
+}) {
   final opened = openLiteRtLmSmokeLibrary(
-    directory: Platform.environment[_litertLmLibDirEnv],
-    abi: Abi.current(),
-    cApiV1: liteRtLmSmokeUsesCApiV1(liteRtLmReleaseTag),
+    directory: directory,
+    abi: abi,
+    cApiV1: liteRtLmSmokeUsesCApiV1(releaseTag),
+    openLibrary: openLibrary,
   );
   final library = opened.library;
   for (final symbol in _requiredSymbols) {
     library.lookup<NativeFunction<Void Function()>>(symbol);
   }
 
-  print(
-    'RESULT litert_lm_library ${jsonEncode({'abi': Abi.current().toString(), 'library': opened.path, 'symbols': _requiredSymbols})}',
-  );
+  return {
+    'abi': abi.toString(),
+    'library': opened.path,
+    'symbols': _requiredSymbols,
+    'inProcessLiteRtAbi': requireInProcessLiteRtMarker(library, abi),
+  };
+}
+
+/// Fails when a bundled Linux or Windows runtime does not report in-process
+/// LiteRT, which gates native embeddings there; a repin that drops the
+/// `litert_lm_native_in_process_litert_abi_version` export would otherwise
+/// surface only on hardware. Returns the reported value, or null where the
+/// marker is not required.
+int? requireInProcessLiteRtMarker(DynamicLibrary library, Abi abi) {
+  if (abi != Abi.linuxX64 && abi != Abi.linuxArm64 && abi != Abi.windowsX64) {
+    return null;
+  }
+  final reported = readLiteRtLmInProcessLiteRtAbiVersion(library);
+  if (reported != liteRtLmInProcessLiteRtAbiVersion) {
+    throw StateError(
+      'The $abi LiteRT-LM runtime reports '
+      'litert_lm_native_in_process_litert_abi_version '
+      '${reported ?? '(not exported)'}, expected '
+      '$liteRtLmInProcessLiteRtAbiVersion.',
+    );
+  }
+  return reported;
 }
 
 bool _isSupportedHost() {
diff --git a/website/docs/maintainers/native-and-web-sync.md b/website/docs/maintainers/native-and-web-sync.md
index 75c6abf3d..6013400ce 100644
--- a/website/docs/maintainers/native-and-web-sync.md
+++ b/website/docs/maintainers/native-and-web-sync.md
@@ -396,7 +396,12 @@ hook and Apple companion source now pin published
 [v0.19.1-2](https://github.com/leehack/litert-lm-native/releases/tag/v0.19.1-2),
 owner `0b15fb34` / upstream `7a03724c`, which keeps C API 1.0.0 and the
 `v0.19.0` exports and adds the in-process LiteRT marker
-`litert_lm_native_in_process_litert_abi_version` (1 on every platform). The
+`litert_lm_native_in_process_litert_abi_version` (1 on every platform); the
+`LiteRT-LM Smoke` library step fails when the bundled Linux x64 or Windows
+x64 runtime lacks the export or does not report 1, and prints the value as
+`inProcessLiteRtAbi`; Linux arm64 has no CI runner for it. Rolling the pin back
+to a pre-marker tag (`v0.18.1-4`, `v0.19.0`, `v0.19.1`, `v0.19.1-1`) therefore
+fails the smoke on Linux and Windows by design. The
 earlier `-1` rebuild links LiteRT into the Linux and Windows
 `libLiteRtLm` ([litert-lm-native#112](https://github.com/leehack/litert-lm-native/pull/112));
 its Apple and Android binaries are identical to `v0.19.1`. Upstream