Browser called in no-GUI Debian - caused by stanmodel-class.R update?

I often run rstan on a cloud Linux VM with no GUI (DigitalOcean). Today I’ve seen a new problem. I fixed it but thought I’d document it here for others.

sampling() produces a warning that xgd-open (a Linux library to find apps that open various files and feed them through) cannot find a suitable browser. Although it is labelled a “warning”, it freezes the process. It doesn’t return to the R prompt, it just seems to hang.

Of course, there is no browser because there is no GUI.

This seems related to StanProgress.html error: "The address wasn’t understood" - the error is resolved by the sampling() option


but why has it started happening? I’m using Debian 18, and R and rstan were downloaded and installed today. I see that xgd-open is trying to open a temporary file StanProgress.html and that this is mentioned only inside stanmodel-class.R (rstan/stanmodel-class.R at develop · stan-dev/rstan · GitHub), which was updated in September 2020 (commit 72ba2c4). I guess that this changed somehow and now calls xgd-open, and although I’ve installed rstan since September, maybe it has only just come through to the current version of rstan.