diff --git a/server/src/main/java/org/elasticsearch/index/mapper/SemanticTextFieldMapper.java b/server/src/main/java/org/elasticsearch/index/mapper/SemanticTextFieldMapper.java
index ec4dc87273dd3..09284b4223073 100644
--- a/server/src/main/java/org/elasticsearch/index/mapper/SemanticTextFieldMapper.java
+++ b/server/src/main/java/org/elasticsearch/index/mapper/SemanticTextFieldMapper.java
@@ -26,8 +26,8 @@ public class SemanticTextFieldMapper extends FieldMapper {
     public static final String CONTENT_TYPE = "semantic_text";
     private static final String SPARSE_VECTOR_SUFFIX = "_inference";
 
-    private static ParseField TEXT_FIELD = new ParseField("text");
-    private static ParseField INFERENCE_FIELD = new ParseField("inference");
+    private static final String TEXT_SUBFIELD_NAME = "text";
+    private static final String SPARSE_VECTOR_SUBFIELD_NAME = "inference";
 
     private static SemanticTextFieldMapper toType(FieldMapper in) {
         return (SemanticTextFieldMapper) in;
@@ -161,24 +161,49 @@ public FieldMapper.Builder getMergeBuilder() {
     }
 
     @Override
-    protected void parseCreateField(DocumentParserContext context) throws IOException {
+    public void parse(DocumentParserContext context) throws IOException {
 
-        XContentParser parser = context.parser();
-        final String value = parser.textOrNull();
+        context.parser();
+        if (context.parser().currentToken() != XContentParser.Token.START_OBJECT) {
+            throw new IllegalArgumentException(
+                "[semantic_text] fields must be a json object, expected a START_OBJECT but got: " + context.parser().currentToken()
+            );
+        }
 
-        if (value == null) {
-            return;
+        boolean textFound = false;
+        boolean inferenceFound = false;
+        for (XContentParser.Token token = context.parser().nextToken(); token != XContentParser.Token.END_OBJECT; token = context.parser().nextToken()) {
+            if (token != XContentParser.Token.FIELD_NAME) {
+                throw new IllegalArgumentException("[semantic_text] fields expect an object with field names, found " + token);
+            }
+
+            String fieldName = context.parser().currentName();
+            XContentParser.Token valueToken = context.parser().nextToken();
+            switch (fieldName) {
+                case TEXT_SUBFIELD_NAME:
+                    context.doc().add(new StringField(name() + TEXT_SUBFIELD_NAME, context.parser().textOrNull(), Field.Store.NO));
+                    textFound = true;
+                    break;
+                case SPARSE_VECTOR_SUBFIELD_NAME:
+                    sparseVectorFieldInfo.sparseVectorFieldMapper.parse(context);
+                    inferenceFound = true;
+                    break;
+                default:
+                    throw new IllegalArgumentException("Unexpected subfield value: " + fieldName);
+            }
         }
 
-        // Create field for original text
-        context.doc().add(new StringField(name(), value, Field.Store.NO));
+        if (textFound == false) {
+            throw new IllegalArgumentException("[semantic_text] value does not contain [" + TEXT_SUBFIELD_NAME + "] subfield");
+        }
+        if (inferenceFound == false) {
+            throw new IllegalArgumentException("[semantic_text] value does not contain [" + SPARSE_VECTOR_SUBFIELD_NAME + "] subfield");
+        }
+    }
 
-        // Parses inference field, for now a separate field in the doc
-        // TODO make inference field a multifield / child field?
-        context.path().add(simpleName() + SPARSE_VECTOR_SUFFIX);
-        parser.nextToken();
-        sparseVectorFieldInfo.sparseVectorFieldMapper.parse(context);
-        context.path().remove();
+    @Override
+    protected void parseCreateField(DocumentParserContext context) {
+        throw new AssertionError("parse is implemented directly");
     }
 
     @Override
diff --git a/server/src/main/java/org/elasticsearch/ingest/FieldInferenceBulkRequestPreprocessor.java b/server/src/main/java/org/elasticsearch/ingest/FieldInferenceBulkRequestPreprocessor.java
index beea8c77d868c..2cd0a2f3d4d1b 100644
--- a/server/src/main/java/org/elasticsearch/ingest/FieldInferenceBulkRequestPreprocessor.java
+++ b/server/src/main/java/org/elasticsearch/ingest/FieldInferenceBulkRequestPreprocessor.java
@@ -46,7 +46,7 @@ protected void processIndexRequest(
 
         String index = indexRequest.index();
         Map<String, Object> sourceMap = indexRequest.sourceAsMap();
-        sourceMap.entrySet().stream().filter(entry -> fieldNeedsInference(index, entry.getKey())).forEach(entry -> {
+        sourceMap.entrySet().stream().filter(entry -> fieldNeedsInference(index, entry.getKey(), entry.getValue())).forEach(entry -> {
             runInferenceForField(indexRequest, entry.getKey(), refs, slot, onFailure);
         });
     }
@@ -54,7 +54,10 @@ protected void processIndexRequest(
     @Override
     public boolean needsProcessing(DocWriteRequest<?> docWriteRequest, IndexRequest indexRequest, Metadata metadata) {
         return (indexRequest.isFieldInferenceDone() == false)
-            && indexRequest.sourceAsMap().keySet().stream().anyMatch(fieldName -> fieldNeedsInference(indexRequest.index(), fieldName));
+            && indexRequest.sourceAsMap()
+                .entrySet()
+                .stream()
+                .anyMatch(entry -> fieldNeedsInference(indexRequest.index(), entry.getKey(), entry.getValue()));
     }
 
     @Override
@@ -67,9 +70,11 @@ public boolean shouldExecuteOnIngestNode() {
         return false;
     }
 
-    // TODO actual mapping check here
-    private boolean fieldNeedsInference(String index, String fieldName) {
-        return fieldName.startsWith("infer_");
+    private boolean fieldNeedsInference(String index, String fieldName, Object fieldValue) {
+        // TODO actual mapping check here
+        return fieldName.startsWith("infer_")
+            // We want to perform inference when we don't have already calculated it
+            && (fieldValue instanceof String);
     }
 
     private void runInferenceForField(
@@ -87,10 +92,11 @@ private void runInferenceForField(
         refs.acquire();
 
         // TODO Hardcoding model ID and task type
+        final String fieldValue = ingestDocument.getFieldValue(fieldName, String.class);
         InferenceAction.Request inferenceRequest = new InferenceAction.Request(
             TaskType.SPARSE_EMBEDDING,
             "my-elser-model",
-            ingestDocument.getFieldValue(fieldName, String.class),
+            fieldValue,
             Map.of()
         );
 
@@ -99,7 +105,10 @@ private void runInferenceForField(
         client.execute(InferenceAction.INSTANCE, inferenceRequest, ActionListener.runAfter(new ActionListener<InferenceAction.Response>() {
             @Override
             public void onResponse(InferenceAction.Response response) {
-                ingestDocument.setFieldValue(fieldName + "_inference", response.getResult().asMap(fieldName).get(fieldName));
+                ingestDocument.removeField(fieldName);
+                // Transform into two subfields, one with the actual text and other with the inference
+                ingestDocument.setFieldValue(fieldName + "._text", fieldValue);
+                ingestDocument.setFieldValue(fieldName + "._inference", response.getResult().asMap(fieldName).get(fieldName));
                 updateIndexRequestSource(indexRequest, ingestDocument);
             }