using sage engine during compilation of tex file

edit

I would like to automate calling sage after compiling a tex file in TeXShop. I have copied the sage.engine file from ~/Library/TeXShop/Engines/Inactive/Sage to ~/Library/TeXShop/Engines/ and followed the instructions in About Sage.pdf.

I've included the line % !TEX TS-program = sage in my tex file, but when I compile the file the sage expressions don't compute. I only get ?? for sage expressions. If I run sage on the sagetex.sage file and re-compile the tex file, then everything looks good.

I'm running TeXShop 3.75 on MacOS 10.10.5