[Inference API] Fix output stream ordering in InferenceActionProxy (elastic#124225)

Author: timgrein

docs/changelog/124225.yaml

@@ -0,0 +1,5 @@
+pr: 124225
+summary: "[Inference API] Fix output stream ordering in `InferenceActionProxy`"
+area: Machine Learning
+type: bug
+issues: []

x-pack/plugin/core/src/main/java/org/elasticsearch/xpack/core/inference/action/InferenceActionProxy.java

@@ -105,8 +105,8 @@ public ActionRequestValidationException validate() {
         @Override
         public void writeTo(StreamOutput out) throws IOException {
             super.writeTo(out);
-            out.writeString(inferenceEntityId);
             taskType.writeTo(out);
+            out.writeString(inferenceEntityId);
             out.writeBytesReference(content);
             XContentHelper.writeTo(out, contentType);
             out.writeTimeValue(timeout);