Function Blocks (Engine Perspective)

This section covers how the workflow engine manages function blocks -- registration, version resolution, schema validation, and safety semantics. For how to write function blocks in Python, see the Worker SDK documentation.

1. Definition -- What a function block is, its metadata, and how it maps to workflow steps
2. Version Resolving -- How partial versions are resolved to concrete versions
3. Registration Protocol -- How workers register FBs, schema compatibility rules
4. Types & Safety -- Pure/idempotent semantics and how they drive transaction safety