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Phase 3 — Architecture & Engineering

Inter-App Communication Map

The explicit contract that keeps your spaces talking to the right neighbours

2 min read · Document 13 of 30

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What is this document?

The Communication Map is a matrix of every space against every other space, marking each connection as allowed, forbidden, or routed through the core API.

It is short, scannable and unambiguous — and every forbidden cell is enforced, not just documented.

Why does it matter?

  • Every direct connection that should not exist is a coupling that breaks during refactoring.
  • Hidden connections are security holes that are hard to find.
  • New features slot into a known communication pattern.

What's inside?

  • Communication matrix — Allowed, forbidden and routed connections.
  • Enforcement — Network rules, auth scopes and reviews.
  • Change process — How a new connection is approved.
Every connection routes through the core API

How CREAH generates it

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

  • Does any space need real-time data from another?
  • Which spaces may see customer contact details?
  • Which integrations are external?

Example excerpt

## Communication Matrix
              Core API  Customer  Partner  Admin
Core API        —         ✅        ✅       ✅
Customer App    ✅         —        ❌       ❌
Partner App     ✅         ❌        —       ❌

Rule: every ❌ is enforced by network and auth rules, not convention.

Related documents

Phase 3

Event Catalog

Every event your spaces exchange, typed and contracted before anyone builds a listener

Phase 3

Architecture Constitution

The blueprint that keeps every space from becoming a separate disaster

Phase 3

Ecosystem Build Specification

The monorepo blueprint that makes every app feel like one coherent product

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