Yup - that was it - turns out that my declaration of Pulumi.yaml would be overwritten entirely and disregarded by automation, so if I wanted to use it, I had to import it myself:

const currentProject = yaml.load(fs.readFileSync("./Pulumi.yaml"))

and the LocalWorkspace:

..projectSettings: currentProject..

Still getting the error code 4294967295 though - and I have a feeling it might be due to my absolutely massive stack output.. it contains all the stack resources and all the configuration elements used to create it, including temporary configuration operations to create the final result..

I.e. my design decision at the moment is - it doesn't hurt to just throw it in the output 😄.. Guess I might be wrong