Creating a Subkernel

Custom subkernels are distributed as Python packages and registered with Beaker through Python entry points, just like contexts. The Beaker CLI scaffolds the package layout for you.

Scaffolding a new subkernel project

Start with a Beaker project:

beaker project new

and then add a subkernel to it:

beaker subkernel new

The wizard prompts for a name, class names, and a slug, and generates a package containing:

my_subkernel/
├── subkernel.py            # BeakerSubkernel (or CheckpointableBeakerSubkernel) subclass
└── procedures/
    ├── fetch_state.<ext>   # language-side helper script
    └── reflectors/
        ├── default.<ext>
        └── ...

Installing for development

After scaffolding, install the package in editable mode so Beaker picks up your changes:

pip install -e .

The subkernel will be discovered automatically the next time Beaker starts. You can confirm it was registered with:

beaker subkernel list

For details on how reflectors fit into the subkernel, see Reflectors.