# ADR-002: Strict Frontend / Backend Separation

| Field | Value |
| --- | --- |
| Status | Accepted |
| Date | 2025-01-01 |
| Deciders | Platform Architecture |
| Supersedes | — |
| Superseded by | — |

## Context

Mixing UI and server logic in one deployable unit blocks independent scaling, white-label hosting, and multi-client UIs.

## Decision

Backend lives only under `backend/`. Frontend lives only under `frontend/`. Communication is exclusively through versioned REST APIs (and future WebSocket if needed). No shared source except contracts, schemas, generated SDKs, and type definitions.

## Consequences

### Positive

- Independent deploy and scale
- Clear ownership of business logic (backend only)
- Multiple UIs can share the same APIs

### Negative

- Requires disciplined API versioning
- Local DX needs Docker or two runtimes

## Alternatives Considered

1. Monorepo full-stack Next.js with API routes as primary backend
2. Server-rendered Django templates

## Related Documents

- [Architecture Overview](../architecture.md)
- [Module Boundaries](../module-boundaries.md)
- [Developer Guide](../../development/developer-guide.md)