Factory stack

Locked decisions (no per-project relitigation)

Layer	Choice	Why
Runtime	Next.js App Router	Convergent across all customer repos; ecosystem fit for tRPC / server actions / Vercel deploy
Language	TypeScript	Convergent; non-negotiable
Validation	Zod	Pairs with both tRPC and server actions; field registry pattern depends on it
Server state	TanStack Query	Convergent across all repos that need server state
DB	Postgres via Neon (dev branches) or RDS (compliance)	Convergent
Forms	react-hook-form + Zod via resolver	Convergent
Email	Resend	Convergent
Linting	ESLint + Prettier + ESLint Drizzle rules where applicable	Convergent
Env vars	t3-oss/env-nextjs (Zod-validated, server/client split)	Convergent

Decision-criteria choices (pick per project; document in project's CLAUDE.md or DECISIONS.md)

ORM — Drizzle vs Supabase auto-types vs raw pg

• Drizzle — default. Schema partitioning by domain (_shared.ts, <domain>.ts) + shared timestamps helper. pgTableCreator() for prefixing if the DB is shared.
• Supabase auto-generated types — when Supabase Auth + RLS is already doing real work. RLS policies are the contract; auto-types are a free byproduct.
• Raw pg — never for new projects. Migrate if encountered.

Auth — Better Auth + orgs vs Supabase Auth + RLS vs Clerk

• Better Auth + organization plugin — default. Org + RBAC + 2FA out of the box; pairs with Drizzle.
• Supabase Auth + RLS — when RLS pays for itself (multi-role partner/distributor model, deeply branched authz at row level).
• Clerk — consumer/SSO-heavy, or when managed auth UI components matter.

The wrapper interface is the same regardless: requireAuth(), requireRole(), withOrgContext(). See factory-auth.md (Phase B) for the canonical wrapper shape.

API style — server actions vs tRPC

• Server actions — default for feature-folder-colocated apps with one frontend consumer. Pairs with TanStack Query (useMutation wrapping the action).
• tRPC — when typed RPC contracts add leverage: ≥3 entities with cross-feature queries, multiple consumers, or a public API surface.
• Pitfall: don't import both. Pick a side per project.

Component library — Mantine vs shadcn

• Mantine — CRUD-heavy / form-table dense / internal-tool surfaces. Built-in date pickers, multiselects, notifications save weeks. Pair with mantine-form-zod-resolver.
• shadcn — design flexibility / marketing-adjacent / unified Tailwind styling with a landing site. Pair with react-hook-form + zodResolver.
• Same project, one choice. Mixing leads to design drift.

Deploy

• Web (Next.js): Vercel. PR previews via Neon dev branches in GitHub Actions.
• Python services: Cloud Run. CLI / Cloud Run API / Pub/Sub handler — see factory-data-pipelines.md.
• Infra-as-code: Terraform with environments/modules layout when AWS/RDS or HIPAA/FDA compliance is in play; skip when Vercel + Neon is sufficient.

Observability

• PostHog + Sentry from day one. Non-negotiable. Easiest to start early, most expensive to backfill.
• Tag events by tool/feature so per-tool usage is queryable later.
• See factory-observability.md (Phase B) for activity logging and trace ID patterns.

How to use this skill

1. At project kickoff, read this file end-to-end.
2. For decision-criteria choices, make the pick explicitly in the project's CLAUDE.md or a one-page DECISIONS.md (one line per decision).
3. Refer back when the project considers changing course — the criteria are the basis for that conversation.

Pitfalls referenced elsewhere

See factory-pitfalls.md for the anti-patterns digest indexed across all factory-*.md skills.