ADR-0004: Consolidated migration baseline

Status: accepted Date: 2026-08-25 Deciders: platform maintainers Supersedes: historical pre-release migration chains Superseded by: none

Context

Before the first supported release, long exploratory migration chains added noise and produced states no deployed environment needed to preserve.

Decision

Each schema starts with a consolidated, reversible baseline that represents the first supported release. From that release onward, applied migrations are immutable and every change uses a new numbered up/down pair. CI verifies checksums, ordering, reversibility, timeouts, and expand/contract safety.

Consequences

Fresh installation stays fast and deterministic. There is deliberately no upgrade path from unsupported pre-release databases; supported releases use the migration and upgrade guides.