MongoDB SMT for BSON unwrapping

[Sumit Jha]

Hello Team,

I am using the Debezium MongoDB connector 3.2.1.Final and facing an issue when attempting to flatten BSON data types (like $oid, $date) into native types using SMT.

Current Behavior (Without SMTs):
Without any SMTs applied, the data is successfully ingested into Kafka and subsequently consumed by a Snowflake sink connector. However, fields retain their verbose BSON wrappers in the output payload (e.g., "_id": {"$oid": "..."}, "createdAt": {"$date": "..."})

Desired Behavior (With SMTs):
I want these fields flattened so that _id appears as a plain string, and dates/longs appear as their respective native types. For this, I am using the standard ExtractNewDocumentState SMT:

transforms: unwrap
transforms.unwrap.type: io.debezium.connector.mongodb.transforms.ExtractNewDocumentState
transforms.unwrap.add.fields: op,ts_ms,source.ts_ms

The Problem:
With the ExtractNewDocumentState SMT enabled, the connector fails repeatedly with following DataException errors:

<error screenshot attached>

My Question:
How can I automatically unwrap the BSON types ($oid, $date, $numberLong, etc.) into simple scalar types (String, Long, Timestamp) across all fields (including deeply nested ones) without causing DataException with ExtractNewDocumentState due to schema drift in my source MongoDB collections?