=========================
Authoring Custom Pipelines
=========================

The orchestrator treats pipelines as declarative DAGs of
:class:`~batter.pipeline.step.Step` objects. Adding a new protocol therefore boils
down to composing steps and teaching :mod:`batter.orchestrate` how to select them.

1. **Write a factory** (see :mod:`batter.pipeline.factory`). Build a list of
   :class:`Step <batter.pipeline.step.Step>` instances using the helper ``_step`` so
   each node receives a :class:`~batter.pipeline.payloads.StepPayload`.
2. **Expose selection logic** via
   :func:`batter.orchestrate.pipeline_utils.select_pipeline`. Add a branch that
   calls your factory when ``protocol == "<name>"``.
3. **(Optional) Register an :class:`~batter.orchestrate.protocols.FEProtocol`** if
   you need protocol-specific validation or metadata. Look at
   :mod:`batter.orchestrate.protocol_impl` for reference.
4. **Update :class:`batter.config.run.RunConfig`** so the new protocol string is
   accepted and ``fe_sim`` is coerced into the appropriate Pydantic model.
5. **Test and document** – add a lightweight unit test that asserts the ordered step
   names and capture any new YAML options in :doc:`../configuration`.

Once these pieces are in place, :func:`batter.orchestrate.run.run_from_yaml` will
automatically schedule the new pipeline when the user selects your protocol.