S3 Vector Store Java SDK: Metadata Not Persisted or Returned on Vector Storage/Retrieval

I am using the AWS S3 Vector Store (Preview) with the Java SDK (software.amazon.awssdk:s3vectors:2.32.4). When I store vectors with metadata (using PutInputVector.metadata()), the metadata is not persisted—retrieval via GetOutputVector.metadata() or similarity search always returns null.

I have followed the SDK requirements: metadata is wrapped as a Document using Document.fromMap(Map<String, Document>). I have tested with a minimal flat metadata map (e.g., {source: "Milan.md", chunk_id: "milan_chunk_0"}). Debug logs confirm correct wrapping and storage, but metadata is always missing immediately after storage and on retrieval. No errors are thrown; vector storage and retrieval otherwise work as expected. I have reviewed GitHub issues and release notes, and found related S3 metadata bugs, but no solution for S3 Vectors. Minimal code example: // Dependencies: software.amazon.awssdk:s3vectors:2.32.4, software.amazon.awssdk:core:2.32.4

import software.amazon.awssdk.services.s3vectors.S3VectorsClient;
import software.amazon.awssdk.services.s3vectors.model.*;
import software.amazon.awssdk.core.document.Document;
import java.util.*;

public class S3VectorMetadataTest {
    public static void main(String[] args) {
        S3VectorsClient sv = S3VectorsClient.create();
        String vectorBucket = "your-vector-bucket";
        String indexName = "your-index-name";
        String vectorId = "test_vector_1";
        List<Float> embedding = Arrays.asList(0.1f, 0.2f, 0.3f); // Example embedding

        // Minimal metadata map
        Map<String, Document> docMetadata = new HashMap<>();
        docMetadata.put("source", Document.fromString("test.md"));
        docMetadata.put("chunk_id", Document.fromString("test_chunk_1"));
        Document metadataDoc = Document.fromMap(docMetadata);

        PutInputVector vec = PutInputVector.builder()
            .key(vectorId)
            .data(VectorData.builder().float32(embedding).build())
            .metadata(metadataDoc)
            .build();

        sv.putVectors(PutVectorsRequest.builder()
            .vectorBucketName(vectorBucket)
            .indexName(indexName)
            .vectors(vec)
            .build());

        // Fetch immediately after storing
        GetOutputVector storedVec = sv.getVector(GetVectorRequest.builder()
            .vectorBucketName(vectorBucket)
            .indexName(indexName)
            .key(vectorId)
            .build());

        System.out.println("Stored vector metadata: " + storedVec.metadata()); // Always null
    }
}`

Expected: The metadata should be persisted and retrievable after storage.

Actual: storedVec.metadata() is always null.

Questions:

Is this a known limitation or bug in the S3 Vector Store Java SDK or service? Is there a workaround or ETA for a fix? Is there a different way to persist metadata with vectors in S3 Vectors?

Best regards