A structural contract is the set of requirements that every instance of a form type must satisfy. It defines what sections a form must have, what question it answers, how it should be named, and what predicates it typically carries. The contract is not a template — it specifies structure, not content.
Every form type definition page ([[Model Form]], [[Pattern Form]], [[Gloss Form]], etc.) declares its structural contract. For example, the Pattern Form contract requires: context, forces in tension, solution, consequences, and connections. Any node with is_a::[[Pattern Form]] commits to providing those sections. A model requires different sections. A conviction requires different sections. But all patterns look alike, all models look alike — that is what the contract guarantees.
For humans: A reader who has seen one pattern knows how to read any pattern. The structural contract is a promise that the form’s internal organization will be familiar. You do not need to learn a new layout for each node — just the content.
For agents: An AI agent traversing the graph can rely on the structural contract to know where to find the relevant information in a node. The “Sources” section is always where provenance lives. The “Relations” section is always where connections are declared. This predictability is what makes gardens machine-traversable without per-node instruction.
For interoperability: When two gardens share nodes, the structural contract is what makes them compatible. A [[Model Form]] in one garden follows the same contract as a Model Form in any other garden. This is how garden patches work — grafted nodes are readable because the contracts match.