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+# Architecture
+
+## Executive decision (§1)
+
+EPPP is implemented as a **TypeScript modular monolith**: Node.js 24 LTS, Fastify 5, PostgreSQL 18 (sole canonical DB), React 19 (server-rendered public components + Vite admin), and Docker Compose as the primary runtime model.
+
+The first visible release is intentionally small: editable site identity, editable Home page, ordered list of published posts, individual post pages, administration interface, and the **Amber** theme.
+
+**Central product rule:** EPPP v0.1 is small because optional features are absent, not because extensibility is absent.
+
+From the first release the codebase has explicit versioned boundaries for: content types, content blocks, page sections, themes, extensions, extension settings, navigation, visitor preferences, database migrations, media storage, background jobs, events, and rendering.
+
+EPPP is **not** a microservice system, a Next.js app, a WordPress clone, or a browser-installable arbitrary-code marketplace.
+
+## Architecture style (§4)
+
+**Modular monolith.** One application image contains the public server, admin API, rendering pipeline, extension runtime, core services, built admin assets and first-party extensions. An optional worker uses the same image with a different command (`eppp serve` / `eppp worker`).
+
+```
+                 Internet
+                    |
+              Optional edge proxy (Caddy 2.11.4)
+                    |
+        +---------------------------+
+        |  EPPP APP — Node 24 /     |
+        |  Fastify 5                 |
+        |  Public React SSR | Admin  |
+        |  React + Vite               |
+        +------------+---------------+
+                     |
+             Application Core
+        Sites | Content | Revisions | Pages | Navigation | Media
+        Blocks | Themes | Extensions | Settings | Preferences
+        Auth | Jobs | Events | Rendering
+                     |
+            Registry layer
+        ContentType | Block | Section | Theme | Extension | Job
+                     |
+              PostgreSQL 18.6
+```
+
+**Why not microservices:** no v1 requirement justifies distributed transactions, service discovery, brokers, multi-service deployment, or cross-service schema changes. Module boundaries allow future extraction on evidence.
+
+## Repository & dependency architecture (§9)
+
+```
+eppp/
+  apps/server · apps/admin
+  packages/contracts · core · extension-sdk · database-postgres · rendering-react · ui-core · config · testing
+  extensions/core-blog · theme-amber
+  migrations/ · tooling/ · docs/{adr, extension-development, operations}
+  Dockerfile · compose.yml · compose.edge.yml · .env.example · pnpm-workspace.yaml · pnpm-lock.yaml · package.json · tsconfig.base.json
+```
+
+### Dependency direction (§9.1)
+
+Allowed:
+- `apps/server -> core/application -> contracts`
+- `extensions/* -> extension-sdk -> contracts`
+- `database-postgres -> core ports -> Kysely/pg`
+
+Forbidden:
+- `core -> theme-amber`, `core -> core-blog`, `core -> reading`
+- `theme-amber -> database internals`
+- extension A → extension B internals
+- public browser code → server-only package
+
+CI enforces these via import/dependency architecture tests (FIT-001, FIT-010, FIT-011).
+
+## Core ownership (§11)
+
+**Core owns:** application lifecycle; site identity/configuration; authentication; content persistence primitives; revisions; page composition; navigation; extension discovery/activation/settings; theme resolution; content-type/block/section/theme registries; visitor preferences; media storage port; job registry; event bus; migration coordinator; public rendering pipeline; admin API infrastructure; health/readiness; error/observability conventions; hardened outbound fetch (v1.1, §29-A.4); page metadata rendering (v1.1, §34-A).
+
+**Core does not own** (extensions own these): Reading/bookmarks, bookmark seams/half-life, RSS, Amber-specific CSS, projects/running-list, comments, analytics, newsletter integrations, link-health.
+
+## Public rendering (§19)
+
+Public pages are server-rendered first. Pipeline: Fastify route → SiteResolver → VisitorPreferenceResolver → ContentService → PageComposition + BlockRegistry → ThemeResolver → React DOM server renderer → HTML.
+
+**Zero-JavaScript baseline (§19.1):** Home, article, navigation, metadata and footer work with JS disabled. React is a server-rendering detail; the site is not hydrated. Core public Home/article target: **0 bytes** EPPP JavaScript.
+
+**Client islands (§19.2):** only truly interactive features register islands (theme selector, Reading filters, graph, comments, gallery), each with an activation mode (`load`/`idle`/`visible`/`interaction`).
+
+## Administration (§20)
+
+React client app built with Vite, served by the same image. `/admin/*` → `/api/admin/v1/*`. Initial IA: Dashboard, Content→Posts, Home, Navigation, Appearance (Active theme, Theme settings), Extensions, Settings→Site.
+
+## v0.1 public surface (§42)
+
+```
+GET /  ·  GET /posts/:slug  ·  GET /assets/*  ·  GET /media/*
+GET /health/live  ·  GET /health/ready  ·  GET /admin/*
+```
+
+Admin API lives under `/api/admin/v1/*`. Initial Home composition: `core.site-intro` + `core.post-list`; post list defaults to published only, newest first, deterministic ordering, configurable limit.