diff --git a/packages/react-native-fantom/runner/runner.js b/packages/react-native-fantom/runner/runner.js
index 99628faabe0..6ba49135c25 100644
--- a/packages/react-native-fantom/runner/runner.js
+++ b/packages/react-native-fantom/runner/runner.js
@@ -19,7 +19,7 @@ import {
   updateSnapshotsAndGetJestSnapshotResult,
 } from './snapshotUtils';
 import {
-  getBuckModeForPlatform,
+  getBuckModesForPlatform,
   getDebugInfoFromCommandResult,
   getShortHash,
   runBuck2,
@@ -76,7 +76,7 @@ function generateBytecodeBundle({
   const hermesCompilerCommandResult = runBuck2(
     [
       'run',
-      getBuckModeForPlatform(isOptimizedMode),
+      ...getBuckModesForPlatform(isOptimizedMode),
       '//xplat/hermes/tools/hermesc:hermesc',
       '--',
       '-emit-binary',
@@ -178,7 +178,9 @@ module.exports = async function runTest(
 
   const rnTesterCommandResult = runBuck2([
     'run',
-    getBuckModeForPlatform(testConfig.mode === FantomTestConfigMode.Optimized),
+    ...getBuckModesForPlatform(
+      testConfig.mode === FantomTestConfigMode.Optimized,
+    ),
     '//xplat/ReactNative/react-native-cxx/samples/tester:tester',
     '--',
     '--bundlePath',
diff --git a/packages/react-native-fantom/runner/utils.js b/packages/react-native-fantom/runner/utils.js
index 5d698977064..d5aa6deeac7 100644
--- a/packages/react-native-fantom/runner/utils.js
+++ b/packages/react-native-fantom/runner/utils.js
@@ -18,21 +18,30 @@ import {SourceMapConsumer} from 'source-map';
 
 const BUCK_ISOLATION_DIR = 'react-native-fantom-buck-out';
 
-export function getBuckModeForPlatform(enableRelease: boolean = false): string {
+export function getBuckModesForPlatform(
+  enableRelease: boolean = false,
+): $ReadOnlyArray<string> {
   const mode = enableRelease ? 'opt' : 'dev';
 
+  let osPlatform;
   switch (os.platform()) {
     case 'linux':
-      return `@//arvr/mode/linux/${mode}`;
+      osPlatform = `@//arvr/mode/linux/${mode}`;
+      break;
     case 'darwin':
-      return os.arch() === 'arm64'
-        ? `@//arvr/mode/mac-arm/${mode}`
-        : `@//arvr/mode/mac/${mode}`;
+      osPlatform =
+        os.arch() === 'arm64'
+          ? `@//arvr/mode/mac-arm/${mode}`
+          : `@//arvr/mode/mac/${mode}`;
+      break;
     case 'win32':
-      return `@//arvr/mode/win/${mode}`;
+      osPlatform = `@//arvr/mode/win/${mode}`;
+      break;
     default:
       throw new Error(`Unsupported platform: ${os.platform()}`);
   }
+
+  return ['@//xplat/mode/react-force-cxx-platform', osPlatform];
 }
 
 type SpawnResultWithOriginalCommand = {
diff --git a/packages/react-native-fantom/runner/warmup/warmup.js b/packages/react-native-fantom/runner/warmup/warmup.js
index ece60df0dc2..a5503c154ad 100644
--- a/packages/react-native-fantom/runner/warmup/warmup.js
+++ b/packages/react-native-fantom/runner/warmup/warmup.js
@@ -10,7 +10,7 @@
  */
 
 import {
-  getBuckModeForPlatform,
+  getBuckModesForPlatform,
   getDebugInfoFromCommandResult,
   runBuck2,
 } from '../utils';
@@ -96,7 +96,7 @@ async function warmUpMetro(isOptimizedMode: boolean): Promise<void> {
 function warmUpHermesCompiler(isOptimizedMode: boolean): void {
   const buildHermesCompilerCommandResult = runBuck2([
     'build',
-    getBuckModeForPlatform(isOptimizedMode),
+    ...getBuckModesForPlatform(isOptimizedMode),
     '//xplat/hermes/tools/hermesc:hermesc',
   ]);
 
@@ -110,7 +110,7 @@ function warmUpHermesCompiler(isOptimizedMode: boolean): void {
 function warmUpRNTesterCLI(isOptimizedMode: boolean): void {
   const buildRNTesterCommandResult = runBuck2([
     'build',
-    getBuckModeForPlatform(isOptimizedMode),
+    ...getBuckModesForPlatform(isOptimizedMode),
     '//xplat/ReactNative/react-native-cxx/samples/tester:tester',
   ]);