Trying to use some assets as unconnected inputs. This works:

@op(
    ins={"unpartitioned": In(asset_key=AssetKey(["unpartitioned_asset"]), input_manager_key="io_manager")},
    required_resource_keys={"io_manager", "gcs"}
)
def unconnected_asset(context, unpartitioned):
    print(unpartitioned)

But this does not:

@op(
    ins={"partitioned": In(asset_key=AssetKey(["partitioned_asset"]),
                          asset_partitions={"partition_name_string"},
                          input_manager_key="io_manager")},
    required_resource_keys={"io_manager", "gcs"}
)
def unconnected_asset2(context, partitioned):
    print(partitioned)

hmm. Is this only happening to you in gcs? As in, if you switched to using a local fs io manager, does the problem still occur?

Good question - will test it shortly and verify