Dynamic fields are not returned by output_fields=['*'] or [''] in Milvus Lite 3.1.0

[zc277584121]

Summary

Milvus Lite 3.1.0 does not return dynamic fields when searching with output_fields=["*"] or output_fields=["$meta"].

The same repro returns dynamic fields on Milvus Standalone and Zilliz Cloud. This makes client code behave differently across Lite, server, and cloud when it reconnects to an existing dynamic-field collection and does not know all dynamic field names ahead of time.

Environment

• pymilvus==3.0.0
• milvus-lite==3.1.0
• Milvus Lite server version reported by get_server_version(): milvus_lite-3.1.0

Comparison backends tested:

Backend	Version reported	output_fields=["*"]	output_fields=["$meta"]
Milvus Lite	milvus_lite-3.1.0	only pk	only pk
Milvus Standalone	2.5.13	includes dynamic fields	includes dynamic fields
Milvus Standalone	3.0-beta	includes dynamic fields	includes dynamic fields
Zilliz Cloud	Compatible with Milvus 2.6	includes dynamic fields	includes dynamic fields

Reproduction

import os
import tempfile
from pymilvus import DataType, MilvusClient

uri = os.path.join(tempfile.mkdtemp(), "milvus.db")
client = MilvusClient(uri=uri)
print(client.get_server_version())

collection_name = "dynamic_output_repro"

schema = client.create_schema(auto_id=True, enable_dynamic_field=True)
schema.add_field(field_name="pk", datatype=DataType.INT64, is_primary=True, auto_id=True)
schema.add_field(field_name="text", datatype=DataType.VARCHAR, max_length=1024)
schema.add_field(field_name="vector", datatype=DataType.FLOAT_VECTOR, dim=2)

index_params = client.prepare_index_params()
index_params.add_index(field_name="vector", index_type="AUTOINDEX", metric_type="L2")

client.create_collection(
    collection_name=collection_name,
    schema=schema,
    index_params=index_params,
    consistency_level="Strong",
)
client.insert(
    collection_name=collection_name,
    data=[{"text": "foo", "vector": [0.0, 0.0], "page": 1, "source": "test"}],
)
client.flush(collection_name)
client.load_collection(collection_name)

for fields in [["*"], ["$meta"], ["pk", "text", "$meta"], ["pk", "text", "page", "source"]]:
    result = client.search(
        collection_name=collection_name,
        data=[[0.0, 0.0]],
        anns_field="vector",
        search_params={"metric_type": "L2", "params": {}},
        limit=1,
        output_fields=fields,
    )
    print(fields, result[0][0].get("entity"))

Actual output on Milvus Lite 3.1.0

milvus_lite-3.1.0
['*'] {'pk': 1}
['$meta'] {'pk': 1}
['pk', 'text', '$meta'] {'pk': 1, 'text': 'foo'}
['pk', 'text', 'page', 'source'] {'pk': 1, 'text': 'foo', 'page': 1, 'source': 'test'}

Expected behavior

Milvus Lite should align with Milvus Standalone and Zilliz Cloud:

• output_fields=["*"] should return dynamic fields such as page and source.
• output_fields=["$meta"] should return dynamic fields without requiring the client to know each dynamic key ahead of time.

Explicitly listing dynamic field names works in Milvus Lite, so the data is stored and queryable. The issue appears specific to wildcard/meta output field expansion.