defaultUrl behaviour

Hi,

According to the docs, JupyterLab is the default UI as of JupyterHub 2.0 and Helm chart 2.0. I am using binderhub-1.0.0-0.dev.git.3002.h5f189ce which I think matches that, but please let me know otherwise.

I get the classic notebook UI when I run binder with this repo. However, if I follow what’s in the docs and use the below:

  singleuser:
    cmd: jupyterhub-singleuser
    defaultUrl: "/lab"
    extraEnv:
      JUPYTERHUB_SINGLEUSER_APP: "jupyter_server.serverapp.ServerApp"
    image:
      name: pangeo/pangeo-notebook
      tag: 2023.01.04

Running binder again with the same repo produces:

image

Reverting back the config to:

  singleuser:
    cmd: jupyterhub-singleuser
    image:
      name: pangeo/pangeo-notebook
      tag: 2023.01.04

and running binder again with the same repo gets me back to the classic notebook UI:

https://<url>/user/<user>/tree

However, if I manually replace tree with lab in the url:

https://<url>/user/<user>/lab

It runs JupyterLab smoothly.

Do you know why?

Many thanks,
Sebastian