---
term: contract
category: service
status: canonical
authority: world.elonn.local
---

Contract

The named, versioned agreement that defines a World model, runtime payload, or
service payload and its behavior. Runtime contracts tell runtimes what
primitives, capabilities, services, actions, controls, and objects they can
expect.

Fields:
- name — canonical contract name (e.g. elonn.home.runtime)
- version — integer version; breaking changes increment this

Allowed:
- runtime contract
- service contract
- translator contract
- World model contract
- contract name
- contract version

Forbidden:
- schema (describes data shape; a contract is broader — it includes capabilities and behavioral expectations)
- API spec (contracts are runtime payloads, not API documentation)
- manifest (too generic)

Notes:
- The current runtime compatibility contract is elonn.home.runtime at version 2.
- Runtime adapters read the contract name and version to determine how to
execute a translated World payload. Version changes are breaking.
- Runtime contracts are produced by World translators and consumed by runtime
adapters. No runtime and no other service produces the runtime contract.
- When a runtime contract version changes, World, the relevant translator, and
affected runtime adapters must be updated together.

Related:
- runtime
- world
- translator
- web
- session (runtime session)