# AGENTS.md -- Root Monorepo

This is a Turborepo + pnpm monorepo implementing Clean Architecture (Uncle Bob / Lazar Nikolov). It supports Next.js 15 and TanStack Start as frontend frameworks, Payload CMS v3 for content management, and tRPC v11 for type-safe API communication.

---

## Monorepo Package Map

| Package | Path | Purpose | Depends On |
|---|---|---|---|
| `@repo/core` | `packages/core` | Clean Architecture business logic: entities, use cases, repository/service interfaces, controllers, InversifyJS DI container | `zod`, `inversify`, `reflect-metadata` |
| `@repo/api` | `packages/api` | tRPC v11 routers that call `@repo/core` controllers | `@repo/core`, `@trpc/server`, `zod` |
| `@repo/api-client` | `packages/api-client` | Shared React Query hooks, `ApiProvider`, and `useTRPC` for frontend apps | `@repo/api`, `@trpc/client`, `@trpc/tanstack-react-query`, `@tanstack/react-query` |
| `@repo/cms-core` | `packages/cms-core` | Payload CMS config, collections (Users, Articles, Media), globals (SiteSettings), hooks | `payload`, `@payloadcms/db-postgres`, `@payloadcms/richtext-lexical` |
| `@repo/cms-client` | `packages/cms-client` | Dual-mode Payload client (local via Payload instance, HTTP via REST API). STANDALONE -- no monorepo deps | `payload` (types only) |
| `@repo/ui` | `packages/ui` | Atomic Design component library (atoms/molecules/organisms/templates) built with shadcn/ui patterns + Tailwind v4 | `clsx`, `tailwind-merge`, `react` |
| `@repo/eslint-config` | `packages/eslint-config` | Shared ESLint 9 flat configs for the entire monorepo | (tooling) |
| `@repo/typescript-config` | `packages/typescript-config` | Shared `tsconfig` base configs (`base.json`) with `experimentalDecorators` + `emitDecoratorMetadata` | (tooling) |
| `@repo/web-next` | `apps/web-next` | Next.js 15 App Router frontend (port 3000) | `@repo/api`, `@repo/api-client`, `@repo/ui` |
| `@repo/web-tanstack` | `apps/web-tanstack` | TanStack Start frontend (port 3002) | `@repo/api`, `@repo/api-client`, `@repo/ui` |
| `@repo/cms` | `apps/cms` | Thin Next.js shell hosting the Payload Admin UI (port 3001) | `@repo/cms-core`, `@payloadcms/next`, `@payloadcms/ui` |
| `@repo/storybook` | `apps/storybook` | Storybook 8 for `@repo/ui` components (port 6006) | `@repo/ui` |

---

## Dependency Flow Diagram

```
                     +-----------------+     +-----------------+
                     | apps/web-next   |     | apps/web-tanstack|
                     +--------+--------+     +--------+--------+
                              |                       |
                    +---------+-----------+-----------+
                    |                     |
              +-----v------+      +------v-------+
              | @repo/api- |      |  @repo/ui    |
              | client     |      | (Atomic      |
              +-----+------+      |  Design)     |
                    |             +--------------+
              +-----v------+
              | @repo/api  |         +----------+     +------------+
              | (tRPC v11) |         | apps/cms |     | apps/      |
              +-----+------+         +----+-----+     | storybook  |
                    |                     |           +------+-----+
              +-----v------+      +------v-------+          |
              | @repo/core |      | @repo/       |    +-----v------+
              | (Clean     |      | cms-core     |    | @repo/ui   |
              | Arch)      |      | (Payload     |    +-----------+
              +-----+------+      | collections) |
                    |             +--------------+
                    |
              +-----v----------+
              | @repo/          |
              | cms-client      |
              | (optional,      |
              |  standalone)    |
              +----------------+

  @repo/eslint-config ---------> used by all packages (devDependency)
  @repo/typescript-config -----> used by all packages (devDependency)
```

Key rule: arrows point DOWN. A package may only depend on packages below it in this diagram. Apps sit at the top; `@repo/core` and `@repo/cms-client` sit at the bottom.

---

## Complete Data Flow

Every user interaction follows this path:

```
UI Component (React)
  |
  v
useTRPC().content.listArticles.useQuery()     <-- @repo/api-client hook
  |
  v
tRPC Router Procedure (.query / .mutation)     <-- @repo/api router
  |
  v
Controller (Zod safeParse -> InputParseError)  <-- @repo/core interface-adapters
  |
  v
Use Case (business logic + getInjection())    <-- @repo/core application
  |
  v
Repository / Service Interface                 <-- @repo/core application (abstract)
  |
  v
Implementation (@injectable class)             <-- @repo/core infrastructure (concrete)
  |
  v
Data Store (Payload CMS / in-memory mock)
```

Example -- listing articles end-to-end:

```typescript
// 1. UI: apps/web-next -- a React Server Component or client component
const trpc = useTRPC();
const articles = trpc.content.listArticles.useQuery({ status: "published" });

// 2. tRPC router: packages/api/src/router/content.router.ts
contentRouter = router({
  listArticles: publicProcedure
    .input(z.object({ status: z.string().optional(), /* ... */ }).optional())
    .query(async ({ input }) => {
      return await getArticlesController(input ?? {});
    }),
});

// 3. Controller: packages/core/src/interface-adapters/controllers/content/articles.controller.ts
export async function getArticlesController(input) {
  const { data, error } = getInputSchema.safeParse(input);
  if (error) throw new InputParseError("Invalid data", { cause: error });
  return await getArticlesUseCase(data);
}

// 4. Use Case: packages/core/src/application/use-cases/content/get-articles.use-case.ts
export async function getArticlesUseCase(options) {
  const articlesRepository = getInjection("IArticlesRepository");
  return await articlesRepository.getArticles(options);
}

// 5. Repository: resolved at runtime via InversifyJS DI container
//    Mock: packages/core/src/infrastructure/repositories/mock-articles.repository.ts
//    Production: a PayloadArticlesRepository using @repo/cms-client (future)
```

---

## Hard Rules

| # | Rule | Reason |
|---|---|---|
| 1 | `@repo/core` NEVER imports from apps/* or framework packages (Next.js, TanStack) | Core business logic must be framework-agnostic. It must be portable across any UI framework or transport layer. |
| 2 | `@repo/cms-core` NEVER imports from `@repo/core` or `@repo/infrastructure` | CMS config is Payload-native. The bridge between Payload and Clean Architecture is `@repo/cms-client`, consumed in `@repo/core`'s infrastructure layer. |
| 3 | `@repo/cms-client` NEVER imports from any other `@repo/*` package | `cms-client` is standalone. It defines a `PayloadClient` interface with `local` and `http` modes. It has zero monorepo dependencies so it can be used anywhere. |
| 4 | `@repo/core`'s `entities/` layer NEVER imports from `application/`, `infrastructure/`, `interface-adapters/`, or `di/` | Entities are the innermost layer of Clean Architecture. They define pure domain types and errors with zero dependencies. |
| 5 | `@repo/core`'s `application/` layer NEVER imports from `infrastructure/` | Use cases and interfaces depend on abstractions (interfaces), never on concrete implementations. The DI container resolves implementations at runtime. |
| 6 | `@repo/core`'s `interface-adapters/` layer NEVER imports from `infrastructure/` | Controllers validate input and delegate to use cases. They must not know about concrete data access or external services. |

---

## How to Add a New Feature (End-to-End Recipe)

This recipe walks through adding a "comments" feature. Follow every step in order.

### Step 1: Define the Entity (packages/core/src/entities/models/comment.ts)

```typescript
import { z } from "zod";

export const commentSchema = z.object({
  id: z.string(),
  articleId: z.string(),
  authorId: z.string(),
  body: z.string().min(1).max(2000),
  createdAt: z.date(),
});

export type Comment = z.infer<typeof commentSchema>;
```

Export it from `packages/core/src/entities/models/index.ts`:

```typescript
export { commentSchema, type Comment } from "./comment";
```

The barrel export chain is: `models/index.ts` -> `entities/index.ts` -> `core/src/index.ts`. Only `models/index.ts` needs updating; the other two already re-export with `*`.

### Step 2: Define the Repository Interface (packages/core/src/application/repositories/comments.repository.interface.ts)

```typescript
import type { Comment } from "@/entities/models/comment";

export interface ICommentsRepository {
  getComment(id: string): Promise<Comment | undefined>;
  getComments(options?: {
    articleId?: string;
    limit?: number;
    offset?: number;
  }): Promise<Comment[]>;
  createComment(input: Comment): Promise<Comment>;
}
```

Export from `packages/core/src/application/repositories/index.ts`:

```typescript
export type { ICommentsRepository } from "./comments.repository.interface";
```

### Step 3: Create Mock Implementation (packages/core/src/infrastructure/repositories/mock-comments.repository.ts)

```typescript
import { injectable } from "inversify";

import type { ICommentsRepository } from "@/application/repositories/comments.repository.interface";
import type { Comment } from "@/entities/models/comment";

@injectable()
export class MockCommentsRepository implements ICommentsRepository {
  private _comments: Comment[] = [];

  async getComment(id: string): Promise<Comment | undefined> {
    return this._comments.find((c) => c.id === id);
  }

  async getComments(options?: {
    articleId?: string;
    limit?: number;
    offset?: number;
  }): Promise<Comment[]> {
    let result = [...this._comments];
    if (options?.articleId) {
      result = result.filter((c) => c.articleId === options.articleId);
    }
    const offset = options?.offset ?? 0;
    const limit = options?.limit ?? 50;
    return result.slice(offset, offset + limit);
  }

  async createComment(input: Comment): Promise<Comment> {
    this._comments.push(input);
    return input;
  }
}
```

Critical: the `@injectable()` decorator is required for InversifyJS. Without it, the container cannot resolve this class.

### Step 4: Register in DI (packages/core/src/di/)

**4a. Add symbol to `types.ts`:**

```typescript
import type { ICommentsRepository } from "@/application/repositories/comments.repository.interface";

// Add to DI_SYMBOLS:
export const DI_SYMBOLS = {
  // ...existing...
  ICommentsRepository: Symbol.for("ICommentsRepository"),
};

// Add to DI_RETURN_TYPES:
export interface DI_RETURN_TYPES {
  // ...existing...
  ICommentsRepository: ICommentsRepository;
}
```

**4b. Create module `modules/comments.module.ts`:**

```typescript
import { ContainerModule, interfaces } from "inversify";

import type { ICommentsRepository } from "@/application/repositories/comments.repository.interface";
import { MockCommentsRepository } from "@/infrastructure/repositories/mock-comments.repository";
import { DI_SYMBOLS } from "../types";

const initializeModule = (bind: interfaces.Bind) => {
  bind<ICommentsRepository>(DI_SYMBOLS.ICommentsRepository).to(
    MockCommentsRepository
  );
};

export const CommentsModule = new ContainerModule(initializeModule);
```

**4c. Load module in `container.ts`:**

```typescript
import { CommentsModule } from "./modules/comments.module";

export const initializeContainer = () => {
  ApplicationContainer.load(AuthModule);
  ApplicationContainer.load(ContentModule);
  ApplicationContainer.load(CommentsModule); // <-- add
};

export const destroyContainer = () => {
  ApplicationContainer.unload(AuthModule);
  ApplicationContainer.unload(ContentModule);
  ApplicationContainer.unload(CommentsModule); // <-- add
};
```

### Step 5: Create Use Case (packages/core/src/application/use-cases/content/create-comment.use-case.ts)

```typescript
import type { Comment } from "@/entities/models/comment";
import { getInjection } from "@/di/container";

export async function createCommentUseCase(input: {
  articleId: string;
  authorId: string;
  body: string;
}): Promise<Comment> {
  const commentsRepository = getInjection("ICommentsRepository");

  const now = new Date();
  const comment: Comment = {
    id: crypto.randomUUID(),
    articleId: input.articleId,
    authorId: input.authorId,
    body: input.body,
    createdAt: now,
  };

  return await commentsRepository.createComment(comment);
}
```

### Step 6: Create Controller (packages/core/src/interface-adapters/controllers/content/comments.controller.ts)

```typescript
import { z } from "zod";

import { InputParseError } from "@/entities/errors/common";
import type { Comment } from "@/entities/models/comment";
import { createCommentUseCase } from "@/application/use-cases/content/create-comment.use-case";

const createInputSchema = z.object({
  articleId: z.string(),
  authorId: z.string(),
  body: z.string().min(1).max(2000),
});

export async function createCommentController(
  input: Partial<z.infer<typeof createInputSchema>>
): Promise<Comment> {
  const { data, error: inputParseError } = createInputSchema.safeParse(input);

  if (inputParseError) {
    throw new InputParseError("Invalid data", { cause: inputParseError });
  }

  return await createCommentUseCase(data);
}
```

### Step 7: Export from core (packages/core/src/index.ts)

```typescript
export { createCommentController } from "./interface-adapters/controllers/content/comments.controller";
export { createCommentUseCase } from "./application/use-cases/content/create-comment.use-case";
```

### Step 8: Create tRPC Router Procedure (packages/api/src/router/content.router.ts)

Add to the existing content router:

```typescript
import { createCommentController } from "@repo/core";

// Inside contentRouter:
createComment: publicProcedure
  .input(
    z.object({
      articleId: z.string(),
      authorId: z.string(),
      body: z.string().min(1).max(2000),
    })
  )
  .mutation(async ({ input }) => {
    return await createCommentController(input);
  }),
```

### Step 9: Use from UI (apps/web-next)

```typescript
"use client";
import { useTRPC } from "@repo/api-client";
import { useMutation } from "@tanstack/react-query";

export function AddCommentForm({ articleId }: { articleId: string }) {
  const trpc = useTRPC();
  const mutation = trpc.content.createComment.useMutation();

  const handleSubmit = (body: string) => {
    mutation.mutate({ articleId, authorId: "current-user-id", body });
  };

  // ... render form using @repo/ui components
}
```

### Step 10: Add Payload Collection (optional -- packages/cms-core)

If the data is CMS-managed, create a collection. See "How to Add a Payload Collection" below.

---

## How to Add a UI Component

### Classification Guide

Components live in `packages/ui/src/` organized by Atomic Design:

| Level | Directory | Description | Examples |
|---|---|---|---|
| **Atoms** | `src/atoms/{name}/` | Smallest building blocks. Single HTML element wrappers. No composition of other atoms. | `Button`, `Input`, `Label` |
| **Molecules** | `src/molecules/{name}/` | Combine 2+ atoms into a reusable unit. | `FormField` (Label + Input + error text) |
| **Organisms** | `src/organisms/{name}/` | Complex UI sections combining molecules/atoms. May contain local state. | `LoginForm`, `ArticleCard` |
| **Templates** | `src/templates/{name}/` | Page-level layout structures with slots for organisms/molecules. No data fetching. | `DashboardLayout`, `AuthLayout` |

### File Structure for Each Component

```
src/atoms/my-component/
  my-component.tsx          # Component implementation
  my-component.stories.tsx  # Storybook story
  index.ts                  # Barrel export
```

### Import Rules

| From | Can Import | NEVER Import |
|---|---|---|
| Atoms | `lib/utils` only | Other atoms, molecules, organisms, templates |
| Molecules | Atoms, `lib/utils` | Other molecules, organisms, templates |
| Organisms | Atoms, Molecules, `lib/utils` | Other organisms, templates |
| Templates | Atoms, Molecules, Organisms, `lib/utils` | Other templates |
| Apps | Any `@repo/ui` export | Internal `@repo/ui` paths (always use package export) |

### Export Chain

1. Export from `src/atoms/{name}/index.ts`
2. Re-export from `src/atoms/index.ts`
3. Everything flows through `src/index.ts` which re-exports all levels

### Component Pattern

Use `cn()` from `lib/utils` for className merging. Use `forwardRef` for atoms wrapping native elements:

```typescript
import { forwardRef, type ButtonHTMLAttributes } from "react";
import { cn } from "../../lib/utils";

export const MyButton = forwardRef<HTMLButtonElement, ButtonHTMLAttributes<HTMLButtonElement>>(
  ({ className, ...props }, ref) => (
    <button className={cn("base-classes", className)} ref={ref} {...props} />
  )
);
MyButton.displayName = "MyButton";
```

---

## How to Add a Payload Collection

### Step 1: Create the collection (packages/cms-core/src/collections/{name}/index.ts)

```typescript
import type { CollectionConfig } from "payload";
import { myFields } from "./fields";

export const MyCollection: CollectionConfig = {
  slug: "my-collection",
  admin: {
    useAsTitle: "title",
  },
  fields: myFields,
};
```

### Step 2: Define fields (packages/cms-core/src/collections/{name}/fields.ts)

```typescript
import type { Field } from "payload";

export const myFields: Field[] = [
  { name: "title", type: "text", required: true },
  { name: "content", type: "richText" },
];
```

### Step 3: Register in payload.config.ts

```typescript
import { MyCollection } from "./collections/my-collection";

export default buildConfig({
  collections: [Users, Articles, Media, MyCollection], // add here
  // ...
});
```

### Step 4: Export from index.ts

```typescript
export { MyCollection } from "./collections/my-collection";
```

### Hook Rules

- Hooks live in `collections/{name}/hooks/` with descriptive names like `before-change.ts`
- Hook types: `beforeChange`, `afterChange`, `beforeRead`, `afterRead`, `beforeDelete`, `afterDelete`, `beforeValidate`, `afterValidate`
- Hooks receive `({ data, operation, req })` and must return `data` (for before hooks)
- Hooks MUST NOT import from `@repo/core`. The CMS is independent. If you need to sync with core business logic, use the `@repo/cms-client` bridge in the infrastructure layer, not hooks calling core directly.
- Example hook:

```typescript
import type { CollectionBeforeChangeHook } from "payload";

export const myBeforeChangeHook: CollectionBeforeChangeHook = ({ data, operation }) => {
  if (operation === "create" && data && !data.slug) {
    data.slug = data.title.toLowerCase().replace(/[^a-z0-9]+/g, "-").replace(/^-|-$/g, "");
  }
  return data;
};
```

---

## Key Commands

```bash
pnpm install              # Install all dependencies
pnpm dev                  # Start all dev servers (Next.js :3000, CMS :3001, Storybook :6006)
pnpm build                # Build all packages (via Turborepo)
pnpm test                 # Run all tests (via Turborepo)
pnpm typecheck            # Type-check all packages
pnpm lint                 # Lint all packages
pnpm format               # Format all files with Prettier
pnpm format:check         # Check formatting without writing
docker compose up -d      # Start PostgreSQL (required for CMS)

# Filtered commands
pnpm dev --filter @repo/web-next       # Only start Next.js app
pnpm test --filter @repo/core          # Only test core package
pnpm dev --filter @repo/storybook      # Only start Storybook

# Core package direct commands
cd packages/core && pnpm vitest run    # Run core unit tests
cd packages/core && pnpm vitest --ui   # Run tests with UI
```

---

## Cross-References

Each package and key directory has its own `AGENTS.md` with domain-specific rules and recipes:

- `packages/core/AGENTS.md` -- Clean Architecture layers, import rules, DI resolution
- `packages/core/src/entities/AGENTS.md` -- Entity models and errors
- `packages/core/src/application/AGENTS.md` -- Use cases and interfaces
- `packages/core/src/infrastructure/AGENTS.md` -- Concrete implementations
- `packages/core/src/interface-adapters/controllers/AGENTS.md` -- Controllers
- `packages/core/src/di/AGENTS.md` -- InversifyJS container configuration
- `packages/core/src/application/use-cases/auth/AGENTS.md` -- Auth domain rules
- `packages/core/src/application/use-cases/content/AGENTS.md` -- Content domain rules