ADR-0002 — Stable validation rule codes

• Status: Accepted
• Date: 2026-07 (as embodied in the 0.2.0b1 codebase)

Context

Downstream CI and documentation need durable identifiers for findings, not unstable free-text messages alone.

Decision

Every issue carries a stable code (for example IDENT001, AGG001). Shipped codes keep their meaning; codes are not reused for different findings; removed checks retire their codes.

Consequences

• The Rule catalogue must be updated with every new code.
• Message wording may improve without changing the code’s meaning.

Alternatives considered

• Message-only findings — rejected for automation and changelogability.
• Auto-generated opaque IDs — rejected as unreadable in reviews.

References

• src/cp_anndata_validator/models/issue.py
• docs/schemas/rule-catalogue.md
• Check modules under src/cp_anndata_validator/checks/