Zendesk Chat to GC Web Messaging Data Action 422 Error

I can’t seem to figure out why the Data Action fails with a 422 Unprocessable Entity when pushing Zendesk chat transcripts to Genesys Cloud interactions. The payload structure matches the schema, yet the API rejects the request.

Error: Field ‘channelType’ is invalid. Expected ‘web’, received ‘zendesk_chat’.

How do we map the legacy Zendesk channel type to the correct Genesys Cloud interaction attribute during this migration step?