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Ekklesia/docs/architecture/repository-boundaries.md
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feat: close the browser boundary and add the generic UI host loader
Two gaps stood between the module UI contract and a host that could use
it. ADR 0023 recorded the first honestly but never diagnosed it: a module
UI file compiled with `"types": []` could still typecheck `process.env`.
The second was simply missing — nothing imported a compiled artifact,
checked its identity, mounted it, or tore it down.

The leak was one type-only import, bisected against the real type graph
rather than guessed. `@ekklesia/module-ui-sdk` imported
`type { EkklesiaPrincipal } from "@ekklesia/contracts"`. Importing
contracts/identity alone is clean and importing Zod alone is clean, but
contracts exposes a single barrel entry, so that one import reached
module-database, whose Drizzle types re-introduce Node's globals. The
runtime was never affected — the import was erased and host-context.js is
`export {}` — but a type-graph leak is still a real boundary failure,
because it silently permits code that cannot run in its target
environment.

The fix is not a narrower import path. The SDK now has no dependencies at
all, so there is no graph to leak through and no future contracts change
can reopen this. It owns `ModuleUiPrincipal`: the same shape ADR 0022
chose, with the Zod brand dropped. That brand encodes a server-side
parsing guarantee a browser cannot produce, and it is the same reason
`permissions.has` already took a plain string. An Ekklesia host still
passes its own `EkklesiaPrincipal` straight through — a branded string is
assignable to `string` — while a standalone host builds the literal.
Proven the way an author experiences it: two fixtures compiled under the
exact project a module uses, one supported and one deliberately reaching
for `process`, with the second required to fail on that specific name.

`@ekklesia/module-ui-host` is the generic loader, in its own package
because the SDK is bundled into every module artifact and host-only
loader code has no business shipping there. The boundary checker enforces
both directions: modules may not depend on the loader, and the loader may
depend only on the SDK plus dev-time tooling.

The distinction that shaped the design: Core resolves `entrypoints.ui` to
an absolute path on the server's disk, and a browser needs a URL. A
loader that accepted the path would test green on a server and fail in
every real host, and would quietly own asset publication. So the loader
takes a browser-loadable URL and knows nothing about how one is obtained.
Ekklesia has no route that publishes installed artifacts, so this is
precisely: loader complete, publication deferred. Nothing can mount an
installed module UI yet, and the docs say so rather than implying
otherwise.

Dynamic import is `(url) => import(url)` with a non-analyzable specifier,
kept as a runtime import so a host does not statically bundle every
installed module or need a hardcoded registry. It is injectable for
bundlers needing their own escape hatch, and deliberately not `eval` or
`new Function`, which would cost a host `unsafe-eval` in its CSP.

Identity is validated through the SDK's existing parser before `mount`
runs, so a stale or mismatched bundle never renders. Contract violations
propagate unwrapped; the loader adds only import and mount failure codes,
sanitized, with the cause attached. Unmount is idempotent, safe when a
module returned no cleanup, and marks an instance unmounted before
running cleanup so a throwing cleanup surfaces once and never re-runs. A
failed mount registers no cleanup. Each instance owns its own state, so
two mounts coexist. The loader never mutates the host's container — not
on success, failure, or unmount.

Tests prove all of it against real module URLs (`data:`, which both
browsers and Node import natively) rather than filesystem paths,
including one artifact built by the canonical Pass 2 pipeline and run
under both an Ekklesia-shaped and a standalone-shaped context. Core,
apps/api, and the contracts package are untouched; discovery remains
inert.

Co-Authored-By: Claude Opus 5 <[email protected]>
2026-08-21 21:44:42 -05:00

5.3 KiB

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, public contracts, React, and external backend libraries
surfaces/* UI, renderers, navigation, and interaction Surface SDK, API/auth clients, public contracts, and design packages
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) and authors it in React and TypeScript (ADR 0022). A module may therefore contain .tsx source and depend on react, react-dom, and @ekklesia/module-ui-sdk. It still cannot contain .jsx, stylesheets, 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 shared UI-role packages. 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). 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).
  • @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 surface never imports Core or a feature module. It uses public API/client contracts.
  • 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.
  • 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 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.