# ADR-029: Version as a coarse-grained breaking-change signal

## Status

Accepted

## Context

The `version` integer on `graph_types` could track every schema change or only breaking changes. Tracking every change is noisy; ignoring versioning creates risk.

## Decision

The `version` integer tracks **breaking** schema changes. Non-breaking changes (additive) do not require a version bump. The repository layer checks the version before processing and knows to run migration logic when it doesn't match. An even/odd scheme signals migration state: even = stable, odd = migration in progress.

## Consequences

- Most schema changes (additive) don't bump the version
- Breaking changes bump the version and trigger migration
- Odd versions signal incomplete migration for crash recovery
- The consumer defines when a version bump occurs via a constant

## References

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