Architecture Constitution

What is this document?

The Architecture Constitution defines the system shape: which services exist, which space owns which data, how spaces communicate, and the rules that keep them isolated.

It is the document an AI agent consults before adding any new service, queue or integration.

Why does it matter?

• Multi-space apps without one end up with every space reinventing auth, data fetching and error handling.
• Isolation rules prevent one space from quietly depending on another’s internals.
• Integration is designed, not excavated.

What's inside?

• System overview — Services, data stores and third parties with data flow.
• Isolation rules — What may call what, and through which boundary.
• Cross-cutting concerns — Auth, observability, configuration.

How CREAH generates it

CREAH builds this document from your Stage 0 answers and interview. Questions that shape it include:

• Which cloud will run the product?
• Do any spaces need to work offline?
• Which third-party services are already decided?

Example excerpt

## AC-3: Space Isolation Rule
No space app ever calls another space app's API directly.
All cross-space communication routes through core-api.
Correct: Customer space → core-api → emits order.placed → Restaurant space listens