# AGENTS.md — core-shared

Generic, reusable primitives with **zero business knowledge**. This package is the foundation for all other packages and exports utilities, Payload field/hook definitions, and tRPC initialization.

## Responsibilities

- **Generic primitives** — environment helpers, date utilities, type guards
- **Payload utilities** — field definitions (slug, SEO), blocks (CTA), access controls (is-admin), hooks (slugify, publish timestamp)
- **tRPC platform** — `initTRPC.create()`, shared context factory, procedure builders
- **No business domain knowledge** — no awareness of articles, users, media, or any feature

## Must NOT import

- Any feature package (`@repo/auth`, `@repo/blog`, etc.)
- Any app package
- Framework-specific code (Next.js, TanStack React Query)

## Public exports

From `package.json`:
- `.` — all utilities, Payload exports, tRPC init
- `./payload` — Payload field/hook/block utilities only
- `./trpc/init` — tRPC `initTRPC` instance + builders. **Plan 9:** also exports `t` (the raw `initTRPC.create({...})` instance) so feature packages can build their own procedures via `t.procedure.use(...)`
- `./trpc/context` — tRPC context factory only
- `./trpc/define-error-middleware` — **Plan 9:** factory that builds a tRPC middleware translating domain errors to `TRPCError`. Takes `ReadonlyArray<readonly [ErrorCtor, TRPC_ERROR_CODE_KEY]>` tuples; uses `instanceof` discrimination; preserves the original error as `.cause`. **Owned by features:** each feature passes its own constructors in via `integrations/api/procedures.ts`. core-shared never enumerates feature-specific error classes — this stays boundary-clean

## Test conventions

- Tests colocated: `src/lib/slug-field.ts` → `src/lib/slug-field.test.ts`
- Vitest environment: `node`
- Alias: `@/` resolves to `src/`
- Run: `pnpm test --filter @repo/core-shared`

Covered areas:
- Slug field generation + validation
- Payload hooks (publish-at timestamp, slugify-if-missing)
- Access control helpers