Thanks @dkushari 

I looked at the github issue you posted, but it has to do specifically with DELTA_UNSUPPORTED_SCHEMA_DURING_READ when streaming *from* a delta table.

The specific error I'm seeing is a key error for the Azure storage account hosting the destination external table. In my example, only bronze_table (the writeStream destination) has its storage on that specific storage account. In other words, it looks like writeStream + azure key (which should be vended by the UC temp credential logic) breaks, whilst write + azure key (same table, same everything else) works 100%.

I guess it could be the same issue as the one you posted, but it's raising a horribly confusing error message.

Do you have any other tips, or bug reports I could take a look at?