When using Salesforce Bulk API using the sf CLI or through REST, you might get this error when uploading a csv file.

This is usually caused by line-ending format on the raw csv file. On my Mac machine this should be LF and CRLF on Windows. To fix this you can use a text editor tool like VS Code or Sublime Text.

VS Code, open the .csv file and open the Command Pallete menu (Command+Shift+P keys for Mac), search for “Change End of Line Sequence” and set it to LF or CRLF for windows and save. That’s it, when uploaded Salesforce should detect the right line-ending.

If your using sf data tree, upload your file from the cli.

sf data upsert bulk --sobject Supply_Service__c --file con-update.csv --external-id GT_Consumer_Number__c