diff --git a/test/framework/src/main/java/org/elasticsearch/index/mapper/MapperServiceTestCase.java b/test/framework/src/main/java/org/elasticsearch/index/mapper/MapperServiceTestCase.java
index 459480d1d7316..0c0016fe2af7d 100644
--- a/test/framework/src/main/java/org/elasticsearch/index/mapper/MapperServiceTestCase.java
+++ b/test/framework/src/main/java/org/elasticsearch/index/mapper/MapperServiceTestCase.java
@@ -207,6 +207,12 @@ protected final MapperService createMapperService(Settings settings, String mapp
         return mapperService;
     }
 
+    protected final MapperService createMapperService(IndexVersion indexVersion, Settings settings, XContentBuilder mappings)
+        throws IOException {
+        MapperService mapperService = createMapperService(indexVersion, settings, () -> true, mappings);
+        return mapperService;
+    }
+
     protected final MapperService createMapperService(IndexVersion version, XContentBuilder mapping) throws IOException {
         return createMapperService(version, getIndexSettings(), () -> true, mapping);
     }
diff --git a/x-pack/plugin/inference/src/test/java/org/elasticsearch/xpack/inference/mapper/SemanticInferenceMetadataFieldsMapperTests.java b/x-pack/plugin/inference/src/test/java/org/elasticsearch/xpack/inference/mapper/SemanticInferenceMetadataFieldsMapperTests.java
index 96a1f90f4e688..4c44940c6bf1d 100644
--- a/x-pack/plugin/inference/src/test/java/org/elasticsearch/xpack/inference/mapper/SemanticInferenceMetadataFieldsMapperTests.java
+++ b/x-pack/plugin/inference/src/test/java/org/elasticsearch/xpack/inference/mapper/SemanticInferenceMetadataFieldsMapperTests.java
@@ -9,10 +9,15 @@
 
 import org.apache.lucene.index.FieldInfo;
 import org.apache.lucene.index.FieldInfos;
+import org.elasticsearch.cluster.metadata.IndexMetadata;
 import org.elasticsearch.common.settings.Settings;
+import org.elasticsearch.index.IndexVersion;
+import org.elasticsearch.index.IndexVersions;
+import org.elasticsearch.index.mapper.InferenceMetadataFieldsMapper;
 import org.elasticsearch.index.mapper.MappedFieldType;
 import org.elasticsearch.index.mapper.MapperServiceTestCase;
 import org.elasticsearch.plugins.Plugin;
+import org.elasticsearch.test.index.IndexVersionUtils;
 import org.elasticsearch.xpack.inference.InferencePlugin;
 
 import java.util.Collection;
@@ -24,6 +29,59 @@ protected Collection<? extends Plugin> getPlugins() {
         return Collections.singletonList(new InferencePlugin(Settings.EMPTY));
     }
 
+    public void testIsEnabled() {
+        var settings = Settings.builder()
+            .put(IndexMetadata.SETTING_INDEX_VERSION_CREATED.getKey(), getRandomCompatibleIndexVersion(true))
+            .put(InferenceMetadataFieldsMapper.USE_LEGACY_SEMANTIC_TEXT_FORMAT.getKey(), true)
+            .build();
+        assertFalse(InferenceMetadataFieldsMapper.isEnabled(settings));
+
+        settings = Settings.builder()
+            .put(IndexMetadata.SETTING_INDEX_VERSION_CREATED.getKey(), getRandomCompatibleIndexVersion(false))
+            .put(InferenceMetadataFieldsMapper.USE_LEGACY_SEMANTIC_TEXT_FORMAT.getKey(), true)
+            .build();
+        assertFalse(InferenceMetadataFieldsMapper.isEnabled(settings));
+
+        settings = Settings.builder()
+            .put(IndexMetadata.SETTING_INDEX_VERSION_CREATED.getKey(), getRandomCompatibleIndexVersion(false))
+            .put(InferenceMetadataFieldsMapper.USE_LEGACY_SEMANTIC_TEXT_FORMAT.getKey(), false)
+            .build();
+        assertTrue(InferenceMetadataFieldsMapper.isEnabled(settings));
+
+        // Test that index.mapping.semantic_text.use_legacy_format == false is ignored when the index version is too old to support the new
+        // format
+        settings = Settings.builder()
+            .put(
+                IndexMetadata.SETTING_INDEX_VERSION_CREATED.getKey(),
+                IndexVersionUtils.randomVersionBetween(
+                    random(),
+                    IndexVersions.SEMANTIC_TEXT_FIELD_TYPE,
+                    IndexVersionUtils.getPreviousVersion(IndexVersions.INFERENCE_METADATA_FIELDS_BACKPORT)
+                )  // 8.x version range prior to the introduction of the new format
+            )
+            .put(InferenceMetadataFieldsMapper.USE_LEGACY_SEMANTIC_TEXT_FORMAT.getKey(), false)
+            .build();
+        assertFalse(InferenceMetadataFieldsMapper.isEnabled(settings));
+    }
+
+    public void testIsEnabledByDefault() {
+        var settings = Settings.builder()
+            .put(
+                IndexMetadata.SETTING_INDEX_VERSION_CREATED.getKey(),
+                IndexVersionUtils.randomPreviousCompatibleVersion(random(), IndexVersions.INFERENCE_METADATA_FIELDS_BACKPORT)
+            )
+            .build();
+        assertFalse(InferenceMetadataFieldsMapper.isEnabled(settings));
+
+        settings = Settings.builder()
+            .put(
+                IndexMetadata.SETTING_INDEX_VERSION_CREATED.getKey(),
+                IndexVersionUtils.randomVersionBetween(random(), IndexVersions.INFERENCE_METADATA_FIELDS_BACKPORT, IndexVersion.current())
+            )
+            .build();
+        assertTrue(InferenceMetadataFieldsMapper.isEnabled(settings));
+    }
+
     @Override
     public void testFieldHasValue() {
         assertTrue(
@@ -42,4 +100,19 @@ public void testFieldHasValueWithEmptyFieldInfos() {
     public MappedFieldType getMappedFieldType() {
         return new SemanticInferenceMetadataFieldsMapper.FieldType();
     }
+
+    static IndexVersion getRandomCompatibleIndexVersion(boolean useLegacyFormat) {
+        if (useLegacyFormat) {
+            // Randomly choose an index version compatible with the legacy semantic text format
+            return IndexVersionUtils.randomVersionBetween(random(), IndexVersions.SEMANTIC_TEXT_FIELD_TYPE, IndexVersion.current());
+        } else {
+            // Randomly choose an index version compatible with the new semantic text format
+            return IndexVersionUtils.randomVersionBetween(
+                random(),
+                IndexVersions.INFERENCE_METADATA_FIELDS_BACKPORT,
+                IndexVersion.current()
+            );
+        }
+    }
+
 }
diff --git a/x-pack/plugin/inference/src/test/java/org/elasticsearch/xpack/inference/mapper/SemanticTextFieldMapperTests.java b/x-pack/plugin/inference/src/test/java/org/elasticsearch/xpack/inference/mapper/SemanticTextFieldMapperTests.java
index d78b27607b91b..52d6b5b41bb97 100644
--- a/x-pack/plugin/inference/src/test/java/org/elasticsearch/xpack/inference/mapper/SemanticTextFieldMapperTests.java
+++ b/x-pack/plugin/inference/src/test/java/org/elasticsearch/xpack/inference/mapper/SemanticTextFieldMapperTests.java
@@ -24,6 +24,7 @@
 import org.apache.lucene.search.join.QueryBitSetProducer;
 import org.apache.lucene.search.join.ScoreMode;
 import org.elasticsearch.action.admin.indices.mapping.put.PutMappingRequest;
+import org.elasticsearch.cluster.metadata.IndexMetadata;
 import org.elasticsearch.common.CheckedBiConsumer;
 import org.elasticsearch.common.CheckedBiFunction;
 import org.elasticsearch.common.Strings;
@@ -33,6 +34,7 @@
 import org.elasticsearch.common.settings.Settings;
 import org.elasticsearch.core.CheckedConsumer;
 import org.elasticsearch.index.IndexVersion;
+import org.elasticsearch.index.IndexVersions;
 import org.elasticsearch.index.mapper.DocumentMapper;
 import org.elasticsearch.index.mapper.DocumentParsingException;
 import org.elasticsearch.index.mapper.FieldMapper;
@@ -61,6 +63,7 @@
 import org.elasticsearch.search.LeafNestedDocuments;
 import org.elasticsearch.search.NestedDocuments;
 import org.elasticsearch.search.SearchHit;
+import org.elasticsearch.test.index.IndexVersionUtils;
 import org.elasticsearch.xcontent.XContentBuilder;
 import org.elasticsearch.xcontent.XContentType;
 import org.elasticsearch.xcontent.json.JsonXContent;
@@ -112,10 +115,29 @@ protected Collection<? extends Plugin> getPlugins() {
     }
 
     private MapperService createMapperService(XContentBuilder mappings, boolean useLegacyFormat) throws IOException {
+        IndexVersion indexVersion = SemanticInferenceMetadataFieldsMapperTests.getRandomCompatibleIndexVersion(useLegacyFormat);
+        return createMapperService(mappings, useLegacyFormat, indexVersion, indexVersion);
+    }
+
+    private MapperService createMapperService(
+        XContentBuilder mappings,
+        boolean useLegacyFormat,
+        IndexVersion minIndexVersion,
+        IndexVersion maxIndexVersion
+    ) throws IOException {
+        validateIndexVersion(minIndexVersion, useLegacyFormat);
+        IndexVersion indexVersion = IndexVersionUtils.randomVersionBetween(random(), minIndexVersion, maxIndexVersion);
         var settings = Settings.builder()
+            .put(IndexMetadata.SETTING_INDEX_VERSION_CREATED.getKey(), indexVersion)
             .put(InferenceMetadataFieldsMapper.USE_LEGACY_SEMANTIC_TEXT_FORMAT.getKey(), useLegacyFormat)
             .build();
-        return createMapperService(settings, mappings);
+        return createMapperService(indexVersion, settings, mappings);
+    }
+
+    private static void validateIndexVersion(IndexVersion indexVersion, boolean useLegacyFormat) {
+        if (useLegacyFormat == false && indexVersion.before(IndexVersions.INFERENCE_METADATA_FIELDS_BACKPORT)) {
+            throw new IllegalArgumentException("Index version " + indexVersion + " does not support new semantic text format");
+        }
     }
 
     @Override