randomayzer/agents/antigravity/inbox/TASK-2026-08-20-seed-precommit.md

Task: Phase 2.4 — Seed Pre-Commit Gate (Seed Grinding Elimination)

Assigned to: Antigravity Priority: CRITICAL (fairness) Date: 2026-08-20 Base SHA: 9927e74421223135a170de640255803ab513fd48

Scope

1. Remove client-provided seed from executeDrawSchema (strict schema -> 400 on client seed).
2. Remove client-provided seed from createGiveawaySchema and creation inputs.
3. Fix seed generation inside createAndLockSnapshot / POST /api/giveaways/[id]/snapshot using CSPRNG (generateCryptoSecureSeed) and persist in Giveaway.seed atomically with snapshot creation.
4. Update POST /api/giveaways/[id]/draw to strictly read seed from DB (giveaway.seed). Fail with 409 Conflict if seed is not pre-committed.
5. Hide seed before DRAWN status:
   • Compute seedCommitment = sha256(seed).
   • POST /api/giveaways/[id]/snapshot returns seedCommitment, not raw seed.
   • GET /api/giveaways/[id] masks seed with null/omitted before DRAWN, providing seedCommitment.
   • Ensure GET /api/giveaways and other routes do not leak raw seed.
6. Update UI in src/app/giveaways/new/page.tsx to remove manual seed input and display seedCommitment.
7. Add adversarial / grinding regression tests in tests/seed-precommit-gate.test.ts.
8. Ensure all existing 273 tests pass, lint passes, build passes.