Package architecture

Dependency direction is intentional:

geometry and models   reusable numerical/physics kernels
          │
          ▼
io                    format and transport adapters
          │
          ▼
modules               pipeline-facing adaptation
          │
          ▼
runner                 graph loading and local execution
          │
          ▼
server and client      long-lived remote operation

dataclasses supplies shared containers and step contracts. Reusable numerical or physical calculations belong in geometry or models; file-format access belongs in io; modules adapts those capabilities to ProcessingData and pipeline configuration. Avoid imports that reverse this direction.

The server calls the shared runner rather than maintaining another scientific execution implementation. The client is a supported transport facade and does not import server internals.

For complete step boundaries and metadata requirements, read the module author guide. For I/O contracts, read the source and sink guide.