Ekklesia/docs/architecture/repository-boundaries.md

# Repository boundaries

These rules map platform ownership to filesystem and package boundaries. The executable check is
`pnpm boundaries`; CI must reject violations.

| Area | Owns | May depend on |
| --- | --- | --- |
| `apps/*` | Thin deployable composition roots | Public Core APIs, generated bootstrap, or a surface as required by the app |
| `core` | Feature-agnostic platform implementations | Public contracts and external infrastructure libraries |
| `modules/*` | Domain capability, data, and the module's own UI | Module SDK, module UI SDK, the approved design packages, public contracts, React, and external backend libraries |
| `surfaces/*` | The application shell, UI, renderers, navigation, and interaction | Surface SDK, API/auth clients, the module UI SDK and host loader, design packages, and a browser framework |
| `builders/*` | Declarative surface composition tooling | Builder/surface SDKs and public contracts |
| `packages/*` | Explicitly scoped SDKs, contracts, clients, design, testing, or tooling | Only dependencies appropriate to the package's declared level |
| `templates/module` | A small example backend module | The same dependencies allowed for any module |

## Mandatory rules

- Core never imports a feature module, surface, Builder implementation, or app.
- A module never imports Core implementations, another module, a surface, Builder code, or an app.
- A module may own UI ([ADR 0021](decisions/0021-modules-as-hostable-products.md)) and authors it in
  React and TypeScript ([ADR 0022](decisions/0022-module-ui-authoring-and-host-contract.md)). A
  module may therefore contain `.tsx` source and depend on `react`, `react-dom`, and
  `@ekklesia/module-ui-sdk`. Since
  [ADR 0040](decisions/0040-module-stylesheets-and-artifact-isolation.md) it may also contain plain
  `.css`, but **only** inside a browser-artifact source root the canonical builder compiles
  (`src/ui/`, `src/display/`, `src/contributions/`); a stylesheet anywhere else in a module is a file
  no build reads and no host loads. It still cannot contain `.jsx`, other stylesheet dialects, single-file components,
  Astro/Marko/MDX/HTML views, or SVG presentation assets, and cannot depend on any other UI framework
  (including `react-router-dom`, `react-native`, and `@vitejs/plugin-react`) or on any shared role
  beyond the two approved design packages named below. A module needs no bundler plugin: `@ekklesia/module-ui-build` — a `tooling` package,
  a role modules could already depend on — owns the entire module UI build
  ([ADR 0023](decisions/0023-module-ui-build-pipeline.md)). An unsupported framework aliased behind an allowed name is resolved and rejected by its
  real target.
- Module UI source is subject to the identical layer rules as module backend source: it may not
  import Core, an app, a surface, a builder, or another module. It also may not import
  `@ekklesia/module-ui-host`: that package is host infrastructure, and a module bundling the loader
  would blur the author/host split ([ADR 0024](decisions/0024-browser-safe-ui-sdk-and-host-loader.md)).
- A module may consume exactly two shared **design** roles: `design-tokens` (`@ekklesia/design-tokens`)
  and `ui` (`@ekklesia/ui`), added by
  [ADR 0039](decisions/0039-shared-design-tokens-and-elements.md). This is a named allowlist, not a
  general "browser-safe shared packages are fine" relaxation: `api-client`, `auth-client`,
  `surface-sdk`, and `module-ui-host` remain rejected inside a module. Both approved packages are
  browser-safe by construction — `design-tokens` has no dependencies at all and `ui` depends only on
  it and React — so a module UI file that imports them still cannot typecheck `process.env`, proven by a real
  compile under the exact browser project a module uses. Both are also pinned at the bottom of the
  presentation stack by `design-packages-depend-downward-only`: neither may reach an implementation
  layer, an API/auth client, or the backend contracts barrel, because a design package that could
  would put all of it inside every module artifact that renders a button.
- A module **references** registered global semantic tokens and may derive private,
  differently-prefixed aliases from them inside its own artifact. It may never define an
  `--ekklesia-*` custom property: that would invent a global theme variable outside the registry,
  which a future theme editor could not enumerate and another module could unknowingly depend on.
- `@ekklesia/module-ui-sdk` has no dependencies at all, and `@ekklesia/module-ui-host` depends only
  on it. Both are browser-safe by construction: neither can pull a backend type graph — and with it
  Node's global declarations — into browser code. Core still owns the containing
  application shell and all platform policy, and module UI reaches the host only through
  `@ekklesia/module-ui-sdk`.
- A module stylesheet is compiled **into** the one declared JavaScript artifact as text and installed
  by the host at mount; there is no sidecar file, no second publication route, and no manifest field
  for one. Every browser artifact is mounted inside its own Shadow DOM root the generic loader
  creates, so one module's styles cannot reach the Dashboard, another module, or another renderer,
  and the host's cannot reach in. That root is a correctness boundary for styles, never a sandbox:
  module code remains trusted, same-realm code. The browser mount ABI is versioned
  (`MODULE_UI_ABI_VERSION`) and a mismatched artifact fails closed rather than mounting under guessed
  semantics.
- A module may declare **browser contributions** (`manifest.contributions`, v7): compiled renderers
  it offers to capabilities *other* modules provide
  ([ADR 0041](decisions/0041-module-browser-contributions.md)). Core validates identity,
  compatibility, and the artifact path through the identical resolution every other compiled
  entrypoint uses, and knows nothing about what a contribution renders — there is no payload schema,
  slot, ordering, or rendering hint anywhere in the platform. A contribution is published only when
  another eligible module provides its target capability within the declared range; otherwise it is
  absent rather than broken. A consuming module discovers contributions through
  `ModuleUiHostContext.contributions` and mounts them by id; it never constructs a publication URL,
  and it can only ever see contributions aimed at a capability it itself provides. A contributed
  renderer receives its own id and the consumer's opaque JSON input, and no database, storage,
  credential, session, or API client of its own.
- Manifest v7 permits independently optional primary (`entrypoints.ui`) and full-viewport display
  (`entrypoints.display`) artifacts. Modules own both feature experiences; surfaces own their
  containers, routes, navigation/chrome, credentials, error states, and publication wiring. The
  fixed authoring sources are `src/ui/index.tsx` and `src/display/index.tsx`; both use the same
  role-neutral UI SDK ABI and neither may import a surface or host loader.
- Module UI **asset publication** runs Core → `apps/api`, never the other way
  ([ADR 0025](decisions/0025-trusted-module-ui-asset-publication.md)). Core owns the policy
  (`createModuleUiPublicationRegistry`, built only from already-validated `DiscoveredModule`
  records); `apps/api` owns the HTTP route and the one canonical URL construction. Neither
  `@ekklesia/module-ui-host` nor `@ekklesia/module-ui-sdk` learns anything about how Ekklesia
  publishes artifacts — the loader takes a URL and stays host-neutral — and no module may reach
  publication internals. This introduced no new package and no boundary relaxation: `apps/*` could
  already depend on Core and on shared packages.
- A publication helper accepts module **identity** only. Neither Core's registry nor the API's URL
  builder takes a filename, relative path, or any other artifact selector, so no caller can use one
  to reach a second file inside a module package.
- A surface never imports Core or a feature module. It uses public API/client contracts, and reaches
  the server over HTTP.
- A surface may depend only on browser-safe shared roles (`api-client`, `auth-client`,
  `design-tokens`, `module-ui-host`, `module-ui-sdk`, `surface-sdk`, `ui`) plus dev-time `testing`
  and `tooling`. **`@ekklesia/contracts` is deliberately excluded**, despite being a "public
  contract" package: its barrel pulls Drizzle's types, and with them Node's global declarations, into
  any program that imports it — measured in
  [ADR 0024](decisions/0024-browser-safe-ui-sdk-and-host-loader.md), which removed exactly that
  import from `@ekklesia/module-ui-sdk` to close the browser boundary. `module-sdk` re-exports the
  same barrel and is excluded for the same reason. A surface declares its own types for the wire and
  validates what arrives ([ADR 0026](decisions/0026-minimal-ekklesia-module-ui-host.md)).
- Dashboard navigation configuration is **Core-owned platform state**, never module-owned: Core
  stores groups and placements and resolves the view, `apps/api` exposes it, and `surfaces/shell`
  renders it. A group is presentation configuration and never module structure — it has no manifest,
  version, artifact, or lifecycle, and nothing in discovery, dependency resolution, or module startup
  may ever read it
  ([ADR 0027](decisions/0027-dashboard-navigation-and-flat-modules.md)). A module's manifest declares
  its own display name and nothing about where it is presented.
- The browser host (`surfaces/shell`) statically imports no module. Every installed module UI it can
  mount arrives at run time as a URL from the module UI inventory, is fetched by the generic loader,
  and is never bundled into the shell. Its own build (esbuild, owned by that package) is a separate
  concern from `@ekklesia/module-ui-build`, which compiles a *module's* declared artifact.
- Dashboard login, logout, and session-transition UX are surface-owned
  ([ADR 0034](decisions/0034-host-owned-browser-authentication.md)). They use the API over HTTP and
  must not add credentials, cookies, tokens, or auth methods to `ModuleUiHostContext`; modules keep
  receiving only the host-neutral principal and permission hints already in the UI SDK.
- The display browser application is a separate surface entrypoint under `surfaces/shell`; it also
  statically imports no module and mounts only the exact display descriptor/artifact supplied by the
  API. It ships a third fixed asset, a service worker scoped to `/display/`, that caches **only** the
  display shell and the declared browser artifacts it actually loaded
  ([ADR 0043](decisions/0043-display-offline-code-fallback.md)). It never caches the descriptor,
  `/api/v1/principal`, any module or platform API response, the realtime stream, a pairing exchange,
  or any cross-origin request — so a revoked device stays revoked and cached code can never
  manufacture current authorization. Caching is network-first, so a screen cannot be trapped on
  obsolete code. It contains no Dashboard chrome and does not move display rendering into the surface—the
  module still owns that renderer.
- Separate surfaces do not import each other's internals.
- Builder code composes contracts and surface renderer identifiers; it does not import module or
  surface internals.
- Contract and SDK packages cannot depend upward on implementations.
- Workspace package consumers use declared `exports`, not private subpaths.
- Every internal dependency uses a `workspace:` range and every imported workspace package is
  declared by the consumer.
- Code a workspace package ships (its `src/` and `bin/`, excluding tests and declaration files)
  declares every runtime import in `dependencies` or `optionalDependencies`. A peer declaration may
  stay beside it, but ordinarily never replaces it: a workspace package is linked into its consumers
  as a directory, so its imports resolve from its own `node_modules`, where a consumer never
  satisfies a peer, and a production install (`pnpm install --prod`, as the production image runs)
  omits development dependencies. There are two narrow exceptions, each for one package and one
  peer. `@ekklesia/module-database`'s `drizzle-orm` peer: modules choose that compatible runtime and
  the Module Package v1 bundler incorporates it into their self-contained backend; Core never loads
  the adapter package. And `@ekklesia/ui`'s `react` peer (ADR 0053): the shared elements are only
  ever bundled into browser artifacts, and the consumer's own React must be the one in the bundle;
  no production Node.js process loads them. Type-only imports are exempt; a `.tsx`/`.jsx` file counts as importing `react`,
  because the automatic JSX runtime imports `react/jsx-runtime` implicitly
  (`runtime-imports-are-production-dependencies`).
- Workspace aliases are forbidden because they obscure package ownership in the dependency graph.
- Workspace package names are unique and shared packages declare a recognized architectural role.
- Circular source and workspace-package dependencies are rejected.
- Cross-module data access uses services, events, capabilities, or opaque identifiers rather than
  direct table imports and foreign keys. Modules may not import another module's Drizzle tables,
  columns, relations, schema entrypoint, or migration internals.

The design packages are covered the same way: one fixture proves a module may depend on both, one
proves every other shared role stays rejected, and one proves neither design package may depend
upward.

The boundary test suite includes intentionally invalid fixture graphs. This proves that the guard
rejects every currently machine-checkable repository rule even before production packages fill
every directory. The UI guard rejects component, view, template, stylesheet, shared UI-role, and
common UI-framework dependencies inside modules. This deny list is defense in depth; package
review remains required when adopting a new frontend technology. ADR 0022 narrowed the guard
precisely rather than removing it: React was un-denied, every other framework stayed denied, and the
layer rules were untouched.

The Phase 3 schema validator complements source boundaries by checking table ownership, foreign-key
targets, and physical table namespaces in compiled Drizzle metadata. Offline migration validation
checks each module's packaged Drizzle inventory and policy contract, while deliberately making no
claim that opaque SQL ownership can be proven without PostgreSQL-aware analysis.

## Generated code

Generated artifacts are reproducible outputs with a named generator and validation step. A
generated module bootstrap under the root `generated/` boundary may import discovered module entry
points, and apps may import that generated bootstrap. Handwritten app and Core code still cannot
import feature modules directly. Generated files are never an excuse for a hand-maintained central
module registry.