monorepo-template / core

---
description: "Package dependency boundaries - tag map and enforced invariants."
alwaysApply: false
globs: **/turbo.json
---

# Package Boundaries

Root `turbo.json` `boundaries.tags` is the enforcement: `pnpm boundaries` (inside `pnpm run ci`) **fails CI** on a violation, it is not a convention. This rule is the rationale.

## Tag map

| Tag | Packages |
|-----|----------|
| `app` | every `front-*` / `worker-*` / `queue-*` / `webhook-*` / `mcp-*` |
| `contracts` | `@repo/dtos-common` |
| `contracts-base` | `@repo/enums-common` |
| `lib` | `@repo/correlation-id` |
| `config` | `@repo/typescript-config`, `@repo/vitest-config` |

## Invariants

- **Nothing may depend on an `app`.** `app.dependents.deny` lists all four tags, so apps are entry points and never installable dependencies. Worker-to-Worker calls go through service-binding RPC declared in `wrangler.jsonc` - never a package import.
- **The contract chain cannot invert.** `contracts` → `contracts-base` → `config` are declared as allow-lists, so the documented `enums → dtos` direction is genuinely enforced and cannot become a cycle.
- **`lib` must not depend on apps or contracts.** `lib.dependencies.allow` is `["config"]`: apps may depend on `lib`, never the reverse.
- **A new package must declare its tag.** Add `turbo.json` with `"extends": ["//"]` and a `tags` entry, or `pnpm boundaries` reports it as untagged.
- **`config` depends on nothing internal.** `config.dependencies.allow` is `[]`, so `@repo/typescript-config` and `@repo/vitest-config` cannot depend on any tagged workspace package.

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