feat(api): serve the built Dashboard from the API origin

Serve surfaces/shell's built Dashboard from apps/api on the same origin
as /api (ADR 0044), exactly as the display host is served: a closed set
of files read once at startup, never a static directory, never a path
built from request input.

- The shell exports @ekklesia/shell/dashboard-assets (the exact built
  index.html and script URLs), emits the script at
  assets/ekklesia-dashboard/app.js, and index.html names that absolute
  path so dev and production serve the same URLs.
- GET / and GET /assets/ekklesia-dashboard/app.js answer from a frozen
  snapshot: no-cache with a strong ETag and 304 on match. Source maps
  are never served; every other path is the ordinary sanitized 404.
- The page sets nosniff, X-Frame-Options: DENY, Content-Security-Policy:
  frame-ancestors 'none' (that directive only), and Referrer-Policy:
  no-referrer, on 200 and 304 alike.
- A missing or empty shell build fails startup with a fixed
  DashboardHostAssetError before any module code is imported.
- The If-None-Match comparison moves to conditional-request.ts, shared
  with the display host routes.
- The emailed-link token stripping moves from browser/main.tsx into
  consumeAuthLanding (location and history injected) so it is tested;
  behavior is unchanged.

Co-Authored-By: Claude Opus 5.5 <[email protected]>

apps/api/src/app.ts

@@ -27,6 +27,8 @@ import type { Context, MiddlewareHandler } from "hono";
 import { Hono } from "hono";
 import { cors } from "hono/cors";
 import { AUTH_REQUEST_MAX_BODY_BYTES, platformBodyLimit } from "./body-limits.js";
+import type { DashboardHostAssets } from "./dashboard-host-assets.js";
+import { createDashboardHostRoutes } from "./dashboard-host-routes.js";
 import { createDashboardRoutes } from "./dashboard-routes.js";
 import { createDeviceRoutes } from "./device-routes.js";
 import type { DisplayHostAssets } from "./display-host-assets.js";
@@ -138,6 +140,13 @@ export interface CreateApiAppOptions {
    * presentation only — nothing reachable through this store influences discovery, dependency
    * ordering, module startup, or any authorization decision. */
   readonly dashboard: DashboardStore;
+  /**
+   * The built Dashboard's two files, read once by production startup (ADR 0044). Required rather
+   * than optional, unlike `displayHostAssets`: every installation has a Dashboard, and a missing
+   * shell build fails startup instead of leaving this origin answering `/` with a 404. See
+   * `./dashboard-host-routes.js`.
+   */
+  readonly dashboardHostAssets: DashboardHostAssets;
   /**
    * The readiness inputs behind the unauthenticated health routes (ADR 0044). Required rather than
    * defaulted, like every other dependency here: a composition that cannot reach a database says so
@@ -354,6 +363,11 @@ export function createApiApp(options: CreateApiAppOptions): Hono {
   // own entirely. See `./health-routes.js`.
   app.route("/", createHealthRoutes(options.health));
 
+  // The Dashboard page and its one script, at exact literal paths outside `/api/` (ADR 0044). They
+  // grant no authority and resolve no principal; the page asks `/api/v1/principal` itself. See
+  // `./dashboard-host-routes.js`.
+  app.route("/", createDashboardHostRoutes(options.dashboardHostAssets));
+
   app.route(
     "/",
     createGrantsRoutes({

apps/api/src/conditional-request.ts

@@ -0,0 +1,16 @@
+/**
+ * RFC 9110 weak comparison for a GET/HEAD `If-None-Match` precondition, shared by the host-owned
+ * asset routes that answer `304` against a strong validator they computed from their own bytes.
+ */
+export function etagMatches(headerValue: string | undefined, etag: string): boolean {
+  if (headerValue === undefined) {
+    return false;
+  }
+  if (headerValue.trim() === "*") {
+    return true;
+  }
+  return headerValue.split(",").some((candidate) => {
+    const value = candidate.trim();
+    return (value.startsWith("W/") ? value.slice(2) : value) === etag;
+  });
+}

apps/api/src/dashboard-host-assets.ts

@@ -0,0 +1,69 @@
+import { createHash } from "node:crypto";
+import { readFile } from "node:fs/promises";
+import { dashboardHostAssetUrls } from "@ekklesia/shell/dashboard-assets";
+
+/**
+ * The two immutable, platform-owned files that make up the built Ekklesia Dashboard (ADR 0044).
+ *
+ * Exactly the model `./display-host-assets.js` uses: read once, before the HTTP listener is bound,
+ * from the exact URLs the surface package exports. Request input is never involved in this read, the
+ * package is never exposed as a static directory, and the source map beside the script is never
+ * read. Text rather than a mutable `Buffer` keeps the frozen snapshot a genuinely immutable value
+ * every response can reuse.
+ */
+export interface DashboardHostAssets {
+  readonly html: string;
+  readonly htmlEtag: string;
+  readonly script: string;
+  readonly scriptEtag: string;
+}
+
+/** A startup failure with a fixed, non-secret shape. The originating filesystem exception, package
+ * location, and machine path are intentionally not retained or surfaced. */
+export class DashboardHostAssetError extends Error {
+  readonly code = "DASHBOARD_HOST_ASSET_UNAVAILABLE" as const;
+
+  constructor() {
+    super("The Dashboard host browser assets are unavailable.");
+    this.name = "DashboardHostAssetError";
+    this.stack = `${this.name}: ${this.message}`;
+    Object.freeze(this);
+  }
+}
+
+function strongEtag(text: string): string {
+  return `"${createHash("sha256").update(text).digest("base64url")}"`;
+}
+
+/**
+ * Captures one immutable, internally consistent Dashboard asset snapshot.
+ *
+ * Each strong validator is derived from the exact text in the same snapshot, so bytes from one build
+ * can never be paired with an ETag from another. Empty output is a failed shell build rather than a
+ * valid page that can never render anything.
+ */
+export function createDashboardHostAssets(html: string, script: string): DashboardHostAssets {
+  if (html.trim().length === 0 || script.trim().length === 0) {
+    throw new DashboardHostAssetError();
+  }
+  return Object.freeze({
+    html,
+    htmlEtag: strongEtag(html),
+    script,
+    scriptEtag: strongEtag(script),
+  });
+}
+
+/** Loads only the two surface-declared files. A missing or unreadable build fails startup rather
+ * than leaving an API whose own origin answers `/` with a 404. */
+export async function loadDashboardHostAssets(): Promise<DashboardHostAssets> {
+  try {
+    // Sequential deliberately, as for the display host: diagnostics stay deterministic and no
+    // rejected sibling read is left running after this function has already failed.
+    const html = await readFile(new URL(dashboardHostAssetUrls.html), "utf8");
+    const script = await readFile(new URL(dashboardHostAssetUrls.script), "utf8");
+    return createDashboardHostAssets(html, script);
+  } catch {
+    throw new DashboardHostAssetError();
+  }
+}

apps/api/src/dashboard-host-routes.ts

@@ -0,0 +1,123 @@
+import { Hono } from "hono";
+import { etagMatches } from "./conditional-request.js";
+import { createDashboardHostAssets, type DashboardHostAssets } from "./dashboard-host-assets.js";
+
+/**
+ * The Dashboard's two host-owned routes (ADR 0044). Neither can collide with anything else the API
+ * serves: `/` is the only page the Dashboard has — it has no client router, and every emailed
+ * verification or reset link lands on `/` with a query (ADR 0038) — and the script lives beside, never
+ * inside, the display host's `/assets/ekklesia-display/` namespace. Module routes all live under
+ * `/api/v1/modules/<module-id>`.
+ */
+export const DASHBOARD_HOST_PAGE_PATH = "/";
+export const DASHBOARD_HOST_SCRIPT_PATH = "/assets/ekklesia-dashboard/app.js";
+
+/**
+ * Revalidate-always with a strong `ETag`, exactly the module UI and display-host script policy. The
+ * shell emits fixed, unhashed file names, so no response here may be cached as `immutable`: a
+ * rebuilt Dashboard must reach a browser on its next load, and an unchanged one costs a `304`.
+ */
+const DASHBOARD_HOST_CACHE_CONTROL = "no-cache";
+
+/**
+ * Headers the Dashboard page carries on every answer, including a `304`, so a revalidated cache
+ * entry never keeps an older set.
+ *
+ * The page holds the platform sign-in form, so it refuses to be framed by anyone — `X-Frame-Options`
+ * for older browsers, and CSP `frame-ancestors`, the one directive a policy here carries until the
+ * full Content-Security-Policy is decided separately. `no-referrer` keeps the page's URL, which can
+ * briefly hold an emailed reset token before the shell strips it, out of every request it makes.
+ */
+const DASHBOARD_PAGE_SECURITY_HEADERS = Object.freeze({
+  "Content-Security-Policy": "frame-ancestors 'none'",
+  "Referrer-Policy": "no-referrer",
+  "X-Content-Type-Options": "nosniff",
+  "X-Frame-Options": "DENY",
+});
+
+/** A composition error, detected before any Dashboard route is registered. Carries no file path,
+ * package location, or asset content. */
+export class DashboardHostConfigurationError extends Error {
+  constructor() {
+    super("The Dashboard host configuration is inconsistent.");
+    this.name = "DashboardHostConfigurationError";
+    this.stack = `${this.name}: ${this.message}`;
+    Object.freeze(this);
+  }
+}
+
+/** Copies and validates injected assets before registering any route, as the display host does, so
+ * a composition can never pair bytes with a validator computed from different bytes. */
+function snapshotAssets(input: DashboardHostAssets): DashboardHostAssets {
+  try {
+    const snapshot = createDashboardHostAssets(input.html, input.script);
+    if (snapshot.htmlEtag !== input.htmlEtag || snapshot.scriptEtag !== input.scriptEtag) {
+      throw new DashboardHostConfigurationError();
+    }
+    return snapshot;
+  } catch {
+    throw new DashboardHostConfigurationError();
+  }
+}
+
+function fixedAsset(
+  ifNoneMatch: string | undefined,
+  body: string,
+  etag: string,
+  contentType: string,
+  extraHeaders: Readonly<Record<string, string>>,
+): Response {
+  if (etagMatches(ifNoneMatch, etag)) {
+    return new Response(null, {
+      headers: { ...extraHeaders, "Cache-Control": DASHBOARD_HOST_CACHE_CONTROL, ETag: etag },
+      status: 304,
+    });
+  }
+  return new Response(body, {
+    headers: {
+      "X-Content-Type-Options": "nosniff",
+      ...extraHeaders,
+      "Cache-Control": DASHBOARD_HOST_CACHE_CONTROL,
+      "Content-Type": contentType,
+      ETag: etag,
+    },
+    status: 200,
+  });
+}
+
+/**
+ * Serves the built Dashboard from the same origin as `/api`, so the identity system keeps its
+ * default same-origin shape.
+ *
+ * Two exact literal routes over one frozen snapshot: never a static directory, never a path or file
+ * name taken from the request, and never the source map. Any other path — `/index.html`, `/app.js`,
+ * the `.map`, a traversal spelling — has no route and falls through to the application's ordinary
+ * sanitized `404`. Like the display host's code, these bytes grant no authority: the page renders
+ * the sign-in form until `/api/v1/principal` says otherwise.
+ */
+export function createDashboardHostRoutes(assets: DashboardHostAssets): Hono {
+  const snapshot = snapshotAssets(assets);
+  const routes = new Hono();
+
+  routes.get(DASHBOARD_HOST_PAGE_PATH, (c) =>
+    fixedAsset(
+      c.req.header("if-none-match"),
+      snapshot.html,
+      snapshot.htmlEtag,
+      "text/html; charset=utf-8",
+      DASHBOARD_PAGE_SECURITY_HEADERS,
+    ),
+  );
+
+  routes.get(DASHBOARD_HOST_SCRIPT_PATH, (c) =>
+    fixedAsset(
+      c.req.header("if-none-match"),
+      snapshot.script,
+      snapshot.scriptEtag,
+      "text/javascript; charset=utf-8",
+      {},
+    ),
+  );
+
+  return routes;
+}

apps/api/src/module-display-routes.ts

@@ -6,6 +6,7 @@ import {
   getAuthorizedPrincipal,
   requirePermission,
 } from "./authorization-middleware.js";
+import { etagMatches } from "./conditional-request.js";
 import { createDisplayHostAssets, type DisplayHostAssets } from "./display-host-assets.js";
 export {
   MODULE_DISPLAY_DESCRIPTOR_PREFIX,
@@ -100,20 +101,6 @@ function displayFailure(c: Context): Response {
   return c.json({ code: "AUTHORIZATION_EVALUATION_FAILED" }, 503);
 }
 
-/** RFC 9110 weak comparison for a GET/HEAD `If-None-Match` precondition. */
-function etagMatches(headerValue: string | undefined, etag: string): boolean {
-  if (headerValue === undefined) {
-    return false;
-  }
-  if (headerValue.trim() === "*") {
-    return true;
-  }
-  return headerValue.split(",").some((candidate) => {
-    const value = candidate.trim();
-    return (value.startsWith("W/") ? value.slice(2) : value) === etag;
-  });
-}
-
 /** Copies and validates injected assets before registering any route. Production's loader already
  * creates this exact shape, while this check keeps a test/composition caller from pairing mutable
  * bytes with a stale validator. */

apps/api/src/server.ts

@@ -45,6 +45,7 @@ import {
   wrapFetchWithClientAddress,
 } from "./client-address.js";
 import { type ApiRuntimeConfig, createApiRuntimeConfig } from "./config.js";
+import { loadDashboardHostAssets } from "./dashboard-host-assets.js";
 import { type ApiDatabaseHandle, createApiDatabase } from "./database.js";
 import { withDevicePrincipals } from "./device-principal.js";
 import { loadDisplayHostAssets } from "./display-host-assets.js";
@@ -543,9 +544,13 @@ export async function startApi(
   // starts and application composition succeeds.
   const moduleUi = createModuleUiPublicationRegistry(eligibility.eligibleModules);
   let displayHostAssets: Awaited<ReturnType<typeof loadDisplayHostAssets>> | undefined;
+  let dashboardHostAssets: Awaited<ReturnType<typeof loadDashboardHostAssets>>;
   try {
     displayHostAssets =
       moduleUi.listDisplays().length === 0 ? undefined : await loadDisplayHostAssets();
+    // Unconditional, unlike the display host: every installation serves its Dashboard (ADR 0044),
+    // so a missing shell build fails here, before any module code is imported.
+    dashboardHostAssets = await loadDashboardHostAssets();
   } catch (error) {
     await safeCloseStorage(storageProvider);
     await safeCloseMail(mailProvider);
@@ -625,6 +630,7 @@ export async function startApi(
       },
       // A typed view over the same single pool as identity, authorization, and the module facade.
       dashboard: createDashboardStore(databaseHandle.dashboard),
+      dashboardHostAssets,
       // The app is only composed after `startDiscoveredModuleRuntime` resolved, so module startup
       // has completed whenever it can answer; it stops counting as complete once shutdown begins.
       health: {