Issue
Does Heroku Connect support Salesforce Custom Metadata Types (__mdt)?
Resolution
Heroku Connect supports Custom Metadata Types from Salesforce API v56.0 and later. These objects are considered same as Salesforce Custom Objects by Heroku connect.
Background:
Salesforce Custom Metadata Types were introduced in v38.0 when the fields like SystemModStamp weren't supported by them. Therefore, Heroku Connect didn't support the Custom Metadata Types previously. Customers would see the below error when they try to map these objects:
The object__mdt object cannot be mapped because it has Salesforce API restrictions that prevent it from being syncable.
In API v56.0 (Winter '23), Salesforce introduced the SystemModStamp field for these objects. This enabled them to be supported by Heroku Connect.