# ADR-032: Single-author model, not CRDT

## Status

Accepted

## Context

Schema evolution could follow a single-author model (one consumer defines the graph type) or a multi-author CRDT model (multiple consumers define the same type concurrently).

## Decision

Schema evolution assumes a single author per graph type. There is no concurrent multi-author editing. If this changes (multiple consumers defining the same graph type with different schemas), a CRDT layer would need to sit between the event stream and storage. That's a post-v1 concern.

## Consequences

- Idempotent replay is sufficient; CRDT merge semantics are not needed
- Schema evolution is forward-only (new code processes old data), not bidirectional
- Migration is apply-on-read or apply-on-write, not conflict resolution

## References

- [schema-evolution.md](../schema-evolution.md)