RFC-003 §0 Phase 0 — the (eventId, handlerName) offset contract.
- prisma: ProjectionOffset model + 20260424100000_add_projection_offset
migration (composite PK, handlerName/appliedAt index for reconciliation)
- infra: PrismaProjectionOffsetStore (createMany skipDuplicates +
applyWithOffset transactional helper that rolls offset+mutation back
together on failure)
- module: bind PROJECTION_OFFSET_STORE → PrismaProjectionOffsetStore
- testing: assertProjectorIdempotent harness ("replay N times → single
state mutation") for Phase 2/3 projector specs to reuse
- tests: 12 specs lock the contract — replay 5x → 1 mutation, broken
projectors fail loudly, two projectors keep independent offsets
Note: prisma format normalised existing column alignment when the new
model was added; the meaningful diff is the appended ProjectionOffset
block at the bottom of schema.prisma.
Acceptance criteria from issue:
- migration applies cleanly (validated via prisma format/parse)
- harness exported from read-models/testing and used by example
projector spec at __tests__/idempotency-harness.spec.ts
Co-Authored-By: Paperclip <noreply@paperclip.ing>
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