This works fine though so it is definitely not the template:

response.writeFile({
 file: render.transaction({entityId: parseInt(params.record_id), printMode: render.PrintMode.PDF}),
 isInline: true
 });

But I cannot use this as I have to pass in data via custom data source.

you have serverResponse and response is that just a typos in Slack?

Yeah, it's a typo because I copied that part from NS docs as I removed it from my original script.

what you have shared so far has not actually excluded the template

@battk my question is in 2 parts. Let me share the previous part as well.

function printPDF(params) {
    var renderer = render.create();
    renderer.setTemplateByScriptId({
       scriptId: 'CUSTTMPL_SALE'
    });
    var lookupResult = search.lookupFields({type: search.Type.VENDOR, id: params.vendor_id, columns: ['altname']});
    renderer.addCustomDataSource({
       format: render.DataSource.OBJECT,
       alias: 'data',
       data: {
          vendor_id: params.vendor_name,
          vendor_name: lookupResult.altname
       }
    });

    renderer.addRecord({
       templateName: 'record',
       record: record.load({
          type: params.record_type,
          id: parseInt(params.record_id)
       })
    });

    return renderer.renderAsString();
}

var fileObj = printPDF(params);
response.setHeader({
    name: 'Content-disposition',
    value: 'filename="' + params.tran_id + '"'
});
var pdfFile = render.xmlToPdf({
    xmlString: fileObj
});

response.writeFile({file: pdfFile});

But this works fine:

response.write({

output: renderer.renderAsString()

});

(edited) I have tested printing the template using the code below and that works fine as well.

response.writeFile({
 file: render.transaction({entityId: parseInt(params.record_id), printMode: render.PrintMode.PDF}),
 isInline: true
 });

same answer,

The template is getting printed from the native Print function, if that helps.

rendered.renderasString doesnt actually pass to bfo

so why does the native print function works?

the native print button is equivalent to renderer.transaction

I see...

the renderer does not

should I try by removing the code which is using custom data source?

you also havent really shared anything to suggest that the sales order's form uses CUSTTMPL_SALE

I have verified the form again just now, it is using the template that I have created.

whats the template

CUSTTMPL_SALE

the actual templte

Due to confidentiality reasons, I cannot share the template.