chore: add CLAUDE.md

CLAUDE.md

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+# CLAUDE.md
+
+This file provides guidance to Claude Code (claude.ai/code) when working with code in this repository.
+
+## Development Commands
+
+### Build System
+- `pnpm build` - Build all packages using Turbo
+- `pnpm watch` - Watch mode for all packages
+- `pnpm lint` - Run ESLint across all packages
+- `pnpm test` - Run tests for all packages
+
+### Package Management
+- Uses `pnpm` with workspaces
+- Package manager is pinned to `pnpm@10.12.1`
+- Packages are located in `packages/`, `samples/`, and `tests/`
+
+### Testing
+- Runtime package tests: `pnpm test` (includes vitest, typing generation, and typecheck)
+- CLI tests: `pnpm test` 
+- E2E tests are in `tests/e2e/` directory
+
+### ZenStack CLI Commands
+- `npx zenstack init` - Initialize ZenStack in a project
+- `npx zenstack generate` - Compile ZModel schema to TypeScript
+- `npx zenstack db push` - Sync schema to database (uses Prisma)
+- `npx zenstack migrate dev` - Create and apply migrations
+- `npx zenstack migrate deploy` - Deploy migrations to production
+
+## Architecture Overview
+
+### Core Components
+- **@zenstackhq/runtime** - Main database client and ORM engine built on Kysely
+- **@zenstackhq/cli** - Command line interface and project management
+- **@zenstackhq/language** - ZModel language specification and parser (uses Langium)
+- **@zenstackhq/sdk** - Code generation utilities and schema processing
+
+### Key Architecture Patterns
+- **Monorepo Structure**: Uses pnpm workspaces with Turbo for build orchestration
+- **Language-First Design**: ZModel DSL compiles to TypeScript, not runtime code generation
+- **Kysely-Based ORM**: V3 uses Kysely as query builder instead of Prisma runtime dependency
+- **Plugin Architecture**: Runtime plugins for query interception and entity mutation hooks
+
+### ZModel to TypeScript Flow
+1. ZModel schema (`schema.zmodel`) defines database structure and policies
+2. `zenstack generate` compiles ZModel to TypeScript schema (`schema.ts`)
+3. Schema is used to instantiate `ZenStackClient` with type-safe CRUD operations
+4. Client provides both high-level ORM API and low-level Kysely query builder
+
+### Package Dependencies
+- **Runtime**: Depends on Kysely, Zod, and various utility libraries
+- **CLI**: Depends on language package, Commander.js, and Prisma (for migrations)
+- **Language**: Uses Langium for grammar parsing and AST generation
+- **Database Support**: SQLite (better-sqlite3) and PostgreSQL (pg) only
+
+### Testing Strategy
+- Runtime package has comprehensive client API tests and policy tests
+- CLI has action-specific tests for commands
+- E2E tests validate real-world schema compatibility (cal.com, formbricks, trigger.dev)
+- Type coverage tests ensure TypeScript inference works correctly
+
+## Key Differences from Prisma
+- No runtime dependency on @prisma/client
+- Pure TypeScript implementation without Rust/WASM
+- Built-in access control and validation (coming soon)
+- Kysely query builder as escape hatch instead of raw SQL
+- Schema-first approach with ZModel DSL extension of Prisma schema language
+
+## Development Notes
+- Always run `zenstack generate` after modifying ZModel schemas
+- Database migrations still use Prisma CLI under the hood
+- Plugin system allows interception at ORM, Kysely, and entity mutation levels
+- Computed fields are evaluated at database level for performance