feat: give display devices their own paired identity

ADR 0033 gave Ekklesia a display host and ADR 0034 gave it a login page.
Together, the only way to light a television in a foyer was to sign a
human being into it and leave that session running on a screen anyone can
walk up to: a person's credentials on a wall, a person's session as the
thing signage depends on, and the display going dark when they are
revoked or their session simply expires.

A screen is not a person. Ekklesia now recognizes three principal classes
— anonymous, authenticated human, and managed device — and a device is a
first-class principal with its own credential and its own explicit
permissions. It has no email, no password, and no row in the identity
tables, and it satisfies the `authenticated` baseline never, so every
route that settles for "somebody is signed in" stays closed to it.

Device permissions live in their own table because
ekklesia_core_grant.user_id is a non-null foreign key into the user table
and making it polymorphic would rewrite the platform's central
authorization record to serve one narrow case. That is a schema decision,
not a second decision point: the evaluator gained one branch, so a device
is allowed or denied by the same function, with the same deny-by-default,
as anyone else — with no owner path it could reach and no baseline that
stands in for a grant.

The six-digit code is not the credential. It is printed across a screen in
a public hallway, so it is treated as public: it identifies a request to
an administrator and is worth nothing alone. Collecting the credential
also requires a 256-bit claim secret held only in the requesting browser's
HttpOnly cookie, and approving requires the restricted core.devices.manage
permission. Without that split, reading a code off a wall would hand over
the screen's identity.

The permission a pairing asks for is read from the module's validated
display declaration, never from the request, so a browser cannot ask to be
granted core.devices.manage or another module's permission. Approval
grants exactly that one permission.

Credentials are stored only as SHA-256; the raw value exists in the
Set-Cookie that issues it and the device's own cookie jar, and is never
logged, returned in JSON, or placed in a URL. The cookie is HttpOnly, so
the module display code running in that same page cannot read it.
Revocation is a server-side column checked on every principal resolution,
and re-pairing mints a new identity so an old credential can never come
back. State transitions are conditional updates, so one code cannot be
approved twice or claimed into two credentials under a race.

/api/v1/principal still reports a device as anonymous: it is what the
Dashboard uses to decide whether a person is signed in. Displays read
their viewer from the descriptor instead, which already performed the
authorization — so displays are descriptor-first while the Dashboard stays
principal-first, and neither infers an identity by elimination.

Proven end to end against real PostgreSQL and real HTTP: an unpaired
screen shows a code, an owner approves it, the device opens the display
descriptor and a realtime stream, and revocation closes both while the
device still holds its cookie. An already-open SSE stream is bounded by
realtime's existing five-minute reconnect rather than closed instantly,
and that bound is documented rather than called immediate.

Co-Authored-By: Claude Opus 5 <[email protected]>

surfaces/shell/src/browser/DevicePanel.tsx

@@ -0,0 +1,207 @@
+import { type FormEvent, type ReactElement, useCallback, useEffect, useState } from "react";
+import {
+  approveDevicePairing,
+  type EkklesiaHostConfig,
+  type HostDeviceSummary,
+  listHostDevices,
+  lookupDevicePairing,
+  revokeHostDevice,
+} from "../host-protocol.js";
+
+/**
+ * The administrator's whole device surface: type the code from a screen, name it, approve it, and
+ * later take it away again.
+ *
+ * Deliberately small. Device identity belongs to the platform rather than to any module, so it has
+ * to live in the host — but this is infrastructure plumbing, not a fleet-management product, and
+ * there is no grouping, filtering, bulk action, targeting, health, or remote control here on
+ * purpose (ADR 0036). It renders only for an administrator who actually holds `core.devices.manage`:
+ * a viewer without it is told nothing about which devices exist.
+ */
+const panelStyles = {
+  action: {
+    background: "transparent",
+    border: "1px solid #d6d3d1",
+    borderRadius: "0.25rem",
+    cursor: "pointer",
+    font: "inherit",
+    padding: "0.25rem 0.5rem",
+  },
+  input: {
+    border: "1px solid #d6d3d1",
+    borderRadius: "0.25rem",
+    font: "inherit",
+    minWidth: 0,
+    padding: "0.25rem 0.5rem",
+    width: "100%",
+  },
+  meta: { color: "#78716c", fontSize: "0.8125rem", margin: 0 },
+  row: {
+    alignItems: "center",
+    borderTop: "1px solid #e7e5e4",
+    display: "flex",
+    gap: "0.5rem",
+    justifyContent: "space-between",
+    padding: "0.375rem 0",
+  },
+  section: { display: "grid", gap: "0.5rem" },
+  title: { fontSize: "0.8125rem", fontWeight: 600, letterSpacing: "0.04em", margin: 0 },
+} as const;
+
+type PairingStep =
+  | { readonly step: "idle" }
+  | { readonly step: "busy" }
+  | { readonly step: "found"; readonly moduleId: string; readonly permissionId: string }
+  | { readonly step: "error"; readonly message: string };
+
+export interface DevicePanelProps {
+  readonly config: EkklesiaHostConfig;
+}
+
+export function DevicePanel(props: DevicePanelProps): ReactElement | undefined {
+  const { config } = props;
+  const [devices, setDevices] = useState<readonly HostDeviceSummary[] | undefined>(undefined);
+  const [permitted, setPermitted] = useState(true);
+  const [code, setCode] = useState("");
+  const [name, setName] = useState("");
+  const [pairing, setPairing] = useState<PairingStep>({ step: "idle" });
+
+  const refresh = useCallback(async (): Promise<void> => {
+    try {
+      setDevices(await listHostDevices(config));
+    } catch {
+      // The panel simply does not render for someone who may not manage devices; it never explains
+      // what it would have shown.
+      setPermitted(false);
+    }
+  }, [config]);
+
+  useEffect(() => {
+    void refresh();
+  }, [refresh]);
+
+  if (!permitted) {
+    return undefined;
+  }
+
+  const lookUp = async (event: FormEvent): Promise<void> => {
+    event.preventDefault();
+    setPairing({ step: "busy" });
+    try {
+      const found = await lookupDevicePairing(config, code.trim());
+      setPairing({ moduleId: found.moduleId, permissionId: found.permissionId, step: "found" });
+    } catch {
+      // One message for expired, consumed, mistyped, and never-existed alike.
+      setPairing({ message: "That code is not waiting for approval.", step: "error" });
+    }
+  };
+
+  const approve = async (): Promise<void> => {
+    setPairing({ step: "busy" });
+    try {
+      await approveDevicePairing(config, code.trim(), name.trim());
+      setCode("");
+      setName("");
+      setPairing({ step: "idle" });
+      await refresh();
+    } catch {
+      setPairing({ message: "That code could not be approved.", step: "error" });
+    }
+  };
+
+  const revoke = async (deviceId: string): Promise<void> => {
+    try {
+      await revokeHostDevice(config, deviceId);
+      await refresh();
+    } catch {
+      // Left to the next refresh rather than asserting a failure the operator cannot act on.
+    }
+    await refresh();
+  };
+
+  return (
+    <section data-testid="host-devices" style={panelStyles.section}>
+      <h2 style={panelStyles.title}>DISPLAY DEVICES</h2>
+
+      <form onSubmit={(event) => void lookUp(event)} style={{ display: "grid", gap: "0.375rem" }}>
+        <label htmlFor="device-pairing-code" style={panelStyles.meta}>
+          Pairing code shown on the screen
+        </label>
+        <input
+          autoComplete="off"
+          data-testid="device-pairing-code-input"
+          id="device-pairing-code"
+          inputMode="numeric"
+          maxLength={6}
+          onChange={(event) => setCode(event.target.value)}
+          style={panelStyles.input}
+          value={code}
+        />
+        <button data-testid="device-pairing-lookup" style={panelStyles.action} type="submit">
+          Find display
+        </button>
+      </form>
+
+      {pairing.step === "found" ? (
+        <div data-testid="device-pairing-found" style={{ display: "grid", gap: "0.375rem" }}>
+          <p style={panelStyles.meta}>
+            A display is asking to show <strong>{pairing.moduleId}</strong>.
+          </p>
+          <label htmlFor="device-pairing-name" style={panelStyles.meta}>
+            Name this display
+          </label>
+          <input
+            autoComplete="off"
+            data-testid="device-pairing-name"
+            id="device-pairing-name"
+            maxLength={128}
+            onChange={(event) => setName(event.target.value)}
+            placeholder="Foyer TV"
+            style={panelStyles.input}
+            value={name}
+          />
+          <button
+            data-testid="device-pairing-approve"
+            disabled={name.trim().length === 0}
+            onClick={() => void approve()}
+            style={panelStyles.action}
+            type="button"
+          >
+            Approve
+          </button>
+        </div>
+      ) : undefined}
+
+      {pairing.step === "error" ? (
+        <p data-testid="device-pairing-error" style={panelStyles.meta}>
+          {pairing.message}
+        </p>
+      ) : undefined}
+
+      {devices !== undefined && devices.length === 0 ? (
+        <p data-testid="device-list-empty" style={panelStyles.meta}>
+          No displays are paired.
+        </p>
+      ) : undefined}
+
+      {devices?.map((device) => (
+        <div data-testid={`device-${device.id}`} key={device.id} style={panelStyles.row}>
+          <span>
+            {device.name}
+            {device.revoked ? " (revoked)" : ""}
+          </span>
+          {device.revoked ? undefined : (
+            <button
+              data-testid={`device-revoke-${device.id}`}
+              onClick={() => void revoke(device.id)}
+              style={panelStyles.action}
+              type="button"
+            >
+              Revoke
+            </button>
+          )}
+        </div>
+      ))}
+    </section>
+  );
+}

surfaces/shell/src/browser/HostApp.tsx

@@ -14,6 +14,7 @@ import {
   HostProtocolError,
   loadHostPrincipal,
 } from "../host-protocol.js";
+import { DevicePanel } from "./DevicePanel.js";
 import { LoginForm } from "./LoginForm.js";
 import { ModuleUiFrame } from "./ModuleUiFrame.js";
 
@@ -157,9 +158,13 @@ async function resolveBootstrapState(
 ): Promise<ResolvedBootstrapState> {
   try {
     const bootstrap = await bootstrapHost(config, signal);
-    return bootstrap.principal.kind === "anonymous"
-      ? { status: "anonymous" }
-      : { bootstrap, status: "ready" };
+    // Only a person signs into the Dashboard. The test is `=== "authenticated"` and never "not
+    // anonymous", so a principal class added later cannot quietly become a Dashboard login — which
+    // is precisely how a paired display device would otherwise have walked in (ADR 0036). In
+    // practice `/api/v1/principal` never reports a device at all; this is the second lock.
+    return bootstrap.principal.kind === "authenticated"
+      ? { bootstrap: { ...bootstrap, principal: bootstrap.principal }, status: "ready" }
+      : { status: "anonymous" };
   } catch (error) {
     if (error instanceof HostProtocolError && error.code === "HOST_UNAUTHENTICATED") {
       return { status: "anonymous" };
@@ -167,9 +172,9 @@ async function resolveBootstrapState(
     if (error instanceof HostProtocolError && error.code === "HOST_ACCESS_DENIED") {
       try {
         const principal = await loadHostPrincipal(config, signal);
-        return principal.kind === "anonymous"
-          ? { status: "anonymous" }
-          : { principal, status: "access-denied" };
+        return principal.kind === "authenticated"
+          ? { principal, status: "access-denied" }
+          : { status: "anonymous" };
       } catch {
         return { status: "failed" };
       }
@@ -454,6 +459,7 @@ export function HostApp(props: HostAppProps): ReactElement {
         </button>
       </header>
       <aside style={shellStyles.aside}>
+        <DevicePanel config={config} />
         {entries.length === 0 && groups.length === 0 ? (
           <p data-testid="host-empty" style={{ color: "#57534e", margin: 0 }}>
             No installed module provides a user interface.

surfaces/shell/src/display/DisplayApp.tsx

@@ -7,11 +7,13 @@ import {
   HostProtocolError,
 } from "../host-protocol.js";
 import { DisplayUiFrame } from "./DisplayUiFrame.js";
+import { PairingScreen } from "./PairingScreen.js";
 
 type DisplayState =
   | { readonly status: "loading"; readonly generation: number }
   | { readonly status: "ready"; readonly bootstrap: DisplayHostBootstrap & { status: "ready" } }
-  | { readonly status: "signed-out" }
+  /** No identity this display can use yet: show a pairing code rather than a human login form. */
+  | { readonly status: "pairing" }
   | { readonly status: "unavailable" }
   | { readonly status: "failed" };
 
@@ -93,24 +95,26 @@ export function DisplayApp(props: DisplayAppProps): ReactElement {
         if (abort.signal.aborted) {
           return;
         }
-        setState(
-          bootstrap.status === "signed-out"
-            ? { status: "signed-out" }
-            : { bootstrap, status: "ready" },
-        );
+        setState({ bootstrap, status: "ready" });
       })
       .catch((error: unknown) => {
         if (abort.signal.aborted) {
           return;
         }
+        // A denied or unauthenticated descriptor is the ordinary state of a screen nobody has
+        // paired yet, not an error worth logging on every wall in the building.
+        if (
+          error instanceof HostProtocolError &&
+          (error.code === "DISPLAY_ACCESS_DENIED" || error.code === "HOST_UNAUTHENTICATED")
+        ) {
+          setState({ status: "pairing" });
+          return;
+        }
         console.error("[ekklesia] display host bootstrap failed", error);
         setState(
-          error instanceof HostProtocolError &&
-            (error.code === "DISPLAY_ACCESS_DENIED" || error.code === "DISPLAY_NOT_AVAILABLE")
+          error instanceof HostProtocolError && error.code === "DISPLAY_NOT_AVAILABLE"
             ? { status: "unavailable" }
-            : error instanceof HostProtocolError && error.code === "HOST_UNAUTHENTICATED"
-              ? { status: "signed-out" }
-              : { status: "failed" },
+            : { status: "failed" },
         );
       });
     return () => abort.abort();
@@ -123,10 +127,8 @@ export function DisplayApp(props: DisplayAppProps): ReactElement {
       {state.status === "loading" ? (
         <DisplayMessage testId="display-host-loading">Loading display…</DisplayMessage>
       ) : undefined}
-      {state.status === "signed-out" ? (
-        <DisplayMessage onRetry={retry} testId="display-host-signed-out">
-          Sign in to use this display.
-        </DisplayMessage>
+      {state.status === "pairing" ? (
+        <PairingScreen config={config} moduleId={moduleId} onRetry={retry} />
       ) : undefined}
       {state.status === "unavailable" ? (
         <DisplayMessage onRetry={retry} testId="display-host-unavailable">

surfaces/shell/src/display/PairingScreen.tsx

@@ -0,0 +1,154 @@
+import { type ReactElement, useEffect, useRef, useState } from "react";
+import {
+  type EkklesiaHostConfig,
+  HostProtocolError,
+  pollDevicePairing,
+  requestDevicePairing,
+} from "../host-protocol.js";
+
+/**
+ * What an unpaired screen shows: a short code, and nothing else of consequence.
+ *
+ * This page is looked at by whoever walks past a television, so it deliberately carries no request
+ * id, no claim secret, no permission id, no module internals, and no server URL beyond the one the
+ * browser is already on. The code is the only thing on it that means anything, and the code is
+ * useless on its own — approving it requires an administrator, and collecting the credential
+ * requires the HttpOnly cookie this browser holds and nobody watching can see (ADR 0036).
+ */
+const pairingStyles = {
+  code: {
+    fontFamily: "ui-monospace, SFMono-Regular, Menlo, monospace",
+    fontSize: "clamp(3rem, 14vw, 9rem)",
+    fontWeight: 600,
+    letterSpacing: "0.15em",
+    lineHeight: 1.1,
+    margin: 0,
+  },
+  hint: { color: "#78716c", margin: 0, maxWidth: "40ch" },
+  root: {
+    alignItems: "center",
+    background: "#0c0a09",
+    color: "#fafaf9",
+    display: "flex",
+    flexDirection: "column",
+    gap: "1.5rem",
+    height: "100%",
+    justifyContent: "center",
+    minHeight: "100dvh",
+    padding: "2rem",
+    textAlign: "center",
+  },
+  title: { fontFamily: "system-ui, sans-serif", fontSize: "1.25rem", fontWeight: 500, margin: 0 },
+} as const;
+
+type PairingState =
+  | { readonly status: "requesting" }
+  | { readonly status: "waiting"; readonly code: string }
+  | { readonly status: "unavailable" };
+
+export interface PairingScreenProps {
+  readonly config: EkklesiaHostConfig;
+  readonly moduleId: string;
+  /** Called once the host has issued this device its session, so the display mounts itself without
+   * anyone touching the television. */
+  readonly onRetry: () => void;
+}
+
+export function PairingScreen(props: PairingScreenProps): ReactElement {
+  const { config, moduleId, onRetry } = props;
+  const [state, setState] = useState<PairingState>({ status: "requesting" });
+  const pairedRef = useRef(onRetry);
+  pairedRef.current = onRetry;
+
+  useEffect(() => {
+    const abort = new AbortController();
+    let timer: ReturnType<typeof setTimeout> | undefined;
+    let stopped = false;
+
+    const stop = (): void => {
+      stopped = true;
+      if (timer !== undefined) {
+        clearTimeout(timer);
+      }
+    };
+
+    const begin = async (): Promise<void> => {
+      let requested: { code: string; pollIntervalMs: number };
+      try {
+        requested = await requestDevicePairing(config, moduleId, abort.signal);
+      } catch (error) {
+        if (!abort.signal.aborted) {
+          // Never surfaces the underlying reason on a public screen.
+          if (!(error instanceof HostProtocolError)) {
+            console.error("[ekklesia] pairing request failed");
+          }
+          setState({ status: "unavailable" });
+        }
+        return;
+      }
+      if (stopped || abort.signal.aborted) {
+        return;
+      }
+      setState({ code: requested.code, status: "waiting" });
+
+      const poll = async (): Promise<void> => {
+        if (stopped || abort.signal.aborted) {
+          return;
+        }
+        let status: string;
+        try {
+          status = await pollDevicePairing(config, abort.signal);
+        } catch {
+          // A transient failure is not a reason to abandon a screen that may be on a wall; it asks
+          // again on the next tick.
+          timer = setTimeout(() => void poll(), requested.pollIntervalMs);
+          return;
+        }
+        if (status === "paired") {
+          stop();
+          pairedRef.current();
+          return;
+        }
+        if (status === "expired" || status === "unknown") {
+          // The code aged out before anyone approved it. Draw a fresh one rather than leaving a
+          // dead number on the screen.
+          stop();
+          void begin();
+          return;
+        }
+        timer = setTimeout(() => void poll(), requested.pollIntervalMs);
+      };
+      timer = setTimeout(() => void poll(), requested.pollIntervalMs);
+    };
+
+    void begin();
+    return () => {
+      stop();
+      abort.abort();
+    };
+  }, [config, moduleId]);
+
+  return (
+    <div data-testid="display-pairing" style={pairingStyles.root}>
+      {state.status === "waiting" ? (
+        <>
+          <p style={pairingStyles.title}>Pair this display</p>
+          <p data-testid="display-pairing-code" style={pairingStyles.code}>
+            {state.code}
+          </p>
+          <p style={pairingStyles.hint}>
+            Enter this code in the Ekklesia dashboard to connect this screen. Waiting for approval…
+          </p>
+        </>
+      ) : undefined}
+      {state.status === "requesting" ? (
+        <p style={pairingStyles.title}>Preparing this display…</p>
+      ) : undefined}
+      {state.status === "unavailable" ? (
+        <p data-testid="display-pairing-unavailable" style={pairingStyles.title}>
+          This display is not available.
+        </p>
+      ) : undefined}
+    </div>
+  );
+}

surfaces/shell/src/host-protocol.ts

@@ -231,13 +231,37 @@ function parseDescriptor(entry: unknown): HostModuleUiDescriptor {
  */
 export interface HostModuleDisplayResponse {
   readonly module: HostModuleUiDescriptor;
+  /** Who the host resolved as the viewer. Read from the response that already authorized this
+   * display rather than from `/api/v1/principal`, which answers only about people. */
+  readonly viewer: ModuleUiPrincipal;
+}
+
+/** Strictly validates the host's statement of who is viewing. Only the two principal kinds a
+ * `restricted` display permission can admit are accepted — an anonymous viewer here would mean the
+ * server authorized a display for nobody, which is a protocol violation rather than a state to
+ * render. */
+function parseDisplayViewer(payload: unknown): ModuleUiPrincipal {
+  if (hasExactKeys(payload, ["kind", "userId"]) && payload.kind === "authenticated") {
+    const userId = nonEmptyString(payload.userId);
+    if (userId !== undefined) {
+      return Object.freeze({ kind: "authenticated" as const, userId });
+    }
+  }
+  if (hasExactKeys(payload, ["deviceId", "kind"]) && payload.kind === "device") {
+    const deviceId = nonEmptyString(payload.deviceId);
+    if (deviceId !== undefined) {
+      return Object.freeze({ deviceId, kind: "device" as const });
+    }
+  }
+  throw new HostProtocolError("HOST_RESPONSE_INVALID");
 }
 
 /** Strictly validates the display descriptor response, including every nested URL container. */
 export function parseHostModuleDisplay(payload: unknown): HostModuleDisplayResponse {
-  if (!hasExactKeys(payload, ["module"])) {
+  if (!hasExactKeys(payload, ["module", "viewer"])) {
     throw new HostProtocolError("HOST_RESPONSE_INVALID");
   }
+  const viewer = parseDisplayViewer(payload.viewer);
   const entry = payload.module;
   if (
     !hasExactKeys(entry, ["api", "display", "id", "permissions", "realtime", "version"]) ||
@@ -278,9 +302,207 @@ export function parseHostModuleDisplay(payload: unknown): HostModuleDisplayRespo
       uiUrl,
       version,
     }),
+    viewer,
   });
 }
 
+/** A same-origin, credential-carrying platform mutation. Mirrors `auth-protocol.ts`'s `postJson`:
+ * `redirect: "error"` so a misconfigured deployment cannot silently follow a redirect with the
+ * device's cookies attached, and no thrown value ever carries the request body. */
+async function requestPlatformMutation(
+  config: EkklesiaHostConfig,
+  rootRelativePath: string,
+  body: unknown,
+  signal?: AbortSignal,
+): Promise<unknown> {
+  const performRequest = config.fetch ?? fetch;
+  let response: Response;
+  try {
+    response = await performRequest(resolveApiUrl(config, rootRelativePath), {
+      body: JSON.stringify(body),
+      cache: "no-store",
+      credentials: "include",
+      headers: { accept: "application/json", "content-type": "application/json" },
+      method: "POST",
+      redirect: "error",
+      ...(signal ? { signal } : {}),
+    });
+  } catch (error) {
+    throw new HostProtocolError("HOST_REQUEST_FAILED", { cause: error });
+  }
+  if (response.status === 401 || response.status === 403) {
+    throw new HostProtocolError("HOST_UNAUTHENTICATED");
+  }
+  if (!response.ok) {
+    throw new HostProtocolError("HOST_REQUEST_FAILED");
+  }
+  try {
+    return (await response.json()) as unknown;
+  } catch {
+    throw new HostProtocolError("HOST_RESPONSE_INVALID");
+  }
+}
+
+/**
+ * Asks the host to start pairing this screen, and returns the code to put on it.
+ *
+ * The response deliberately carries no secret. The value that proves this browser is the one that
+ * asked travels in an HttpOnly cookie the host sets, so nothing here — and nothing anyone reads off
+ * the screen — can be used to collect the device's credential (ADR 0036).
+ */
+export async function requestDevicePairing(
+  config: EkklesiaHostConfig,
+  moduleId: string,
+  signal?: AbortSignal,
+): Promise<{ readonly code: string; readonly pollIntervalMs: number }> {
+  const payload = await requestPlatformMutation(
+    config,
+    "/api/v1/device-pairing/requests",
+    { moduleId },
+    signal,
+  );
+  if (!hasExactKeys(payload, ["code", "expiresAt", "pollIntervalMs"])) {
+    throw new HostProtocolError("HOST_RESPONSE_INVALID");
+  }
+  const code = nonEmptyString(payload.code);
+  const pollIntervalMs = payload.pollIntervalMs;
+  if (
+    code === undefined ||
+    typeof pollIntervalMs !== "number" ||
+    !Number.isFinite(pollIntervalMs)
+  ) {
+    throw new HostProtocolError("HOST_RESPONSE_INVALID");
+  }
+  return Object.freeze({ code, pollIntervalMs: Math.max(1000, Math.trunc(pollIntervalMs)) });
+}
+
+/** Asks whether this screen has been approved yet. When it has, the host issues the device session
+ * in a `Set-Cookie` the browser stores and this code never sees. */
+export async function pollDevicePairing(
+  config: EkklesiaHostConfig,
+  signal?: AbortSignal,
+): Promise<string> {
+  const payload = await requestPlatformMutation(
+    config,
+    "/api/v1/device-pairing/claims",
+    {},
+    signal,
+  );
+  if (!hasExactKeys(payload, ["status"])) {
+    throw new HostProtocolError("HOST_RESPONSE_INVALID");
+  }
+  const status = nonEmptyString(payload.status);
+  if (status === undefined) {
+    throw new HostProtocolError("HOST_RESPONSE_INVALID");
+  }
+  return status;
+}
+
+/** One paired display, as the administrator's panel shows it. Deliberately no credential, no hash,
+ * and no pairing history — none of that is anything an operator can act on. */
+export interface HostDeviceSummary {
+  readonly id: string;
+  readonly name: string;
+  readonly permissions: readonly string[];
+  readonly revoked: boolean;
+}
+
+export async function lookupDevicePairing(
+  config: EkklesiaHostConfig,
+  code: string,
+  signal?: AbortSignal,
+): Promise<{ readonly moduleId: string; readonly permissionId: string }> {
+  const payload = await requestPlatformMutation(
+    config,
+    "/api/v1/device-pairing/lookups",
+    { code },
+    signal,
+  );
+  if (!hasExactKeys(payload, ["expiresAt", "moduleId", "permissionId", "requestedAt"])) {
+    throw new HostProtocolError("HOST_RESPONSE_INVALID");
+  }
+  const moduleId = nonEmptyString(payload.moduleId);
+  const permissionId = nonEmptyString(payload.permissionId);
+  if (moduleId === undefined || permissionId === undefined) {
+    throw new HostProtocolError("HOST_RESPONSE_INVALID");
+  }
+  return Object.freeze({ moduleId, permissionId });
+}
+
+export async function approveDevicePairing(
+  config: EkklesiaHostConfig,
+  code: string,
+  deviceName: string,
+  signal?: AbortSignal,
+): Promise<void> {
+  await requestPlatformMutation(
+    config,
+    "/api/v1/device-pairing/approvals",
+    { code, deviceName },
+    signal,
+  );
+}
+
+export async function listHostDevices(
+  config: EkklesiaHostConfig,
+  signal?: AbortSignal,
+): Promise<readonly HostDeviceSummary[]> {
+  const payload = await requestPlatformJson(config, "/api/v1/devices", signal, {
+    forbidden: "HOST_ACCESS_DENIED",
+  });
+  if (typeof payload !== "object" || payload === null || !("devices" in payload)) {
+    throw new HostProtocolError("HOST_RESPONSE_INVALID");
+  }
+  const entries = (payload as { devices: unknown }).devices;
+  if (!Array.isArray(entries)) {
+    throw new HostProtocolError("HOST_RESPONSE_INVALID");
+  }
+  return Object.freeze(
+    entries.map((entry) => {
+      const id = nonEmptyString((entry as { id?: unknown }).id);
+      const name = nonEmptyString((entry as { name?: unknown }).name);
+      const permissions = (entry as { permissions?: unknown }).permissions;
+      if (id === undefined || name === undefined || !Array.isArray(permissions)) {
+        throw new HostProtocolError("HOST_RESPONSE_INVALID");
+      }
+      return Object.freeze({
+        id,
+        name,
+        permissions: Object.freeze(permissions.map((permission) => String(permission))),
+        revoked: (entry as { revoked?: unknown }).revoked === true,
+      });
+    }),
+  );
+}
+
+export async function revokeHostDevice(
+  config: EkklesiaHostConfig,
+  deviceId: string,
+  signal?: AbortSignal,
+): Promise<void> {
+  const performRequest = config.fetch ?? fetch;
+  let response: Response;
+  try {
+    response = await performRequest(
+      resolveApiUrl(config, `/api/v1/devices/${encodeURIComponent(deviceId)}/revoke`),
+      {
+        body: "{}",
+        cache: "no-store",
+        credentials: "include",
+        headers: { accept: "application/json", "content-type": "application/json" },
+        method: "POST",
+        redirect: "error",
+        ...(signal ? { signal } : {}),
+      },
+    );
+  } catch (error) {
+    throw new HostProtocolError("HOST_REQUEST_FAILED", { cause: error });
+  }
+  if (!response.ok) {
+    throw new HostProtocolError("HOST_REQUEST_FAILED");
+  }
+}
+
 /** Reads one exact `/display/<module-id>` pathname without accepting a trailing path or traversal. */
 export function parseDisplayRoute(pathname: string): string {
   const match = /^\/display\/([^/]+)$/u.exec(pathname);
@@ -480,43 +702,46 @@ export async function loadModuleDisplay(
   config: EkklesiaHostConfig,
   moduleId: string,
   signal?: AbortSignal,
-): Promise<HostModuleUiDescriptor> {
+): Promise<HostModuleDisplayResponse> {
   const payload = await requestPlatformJson(config, moduleDisplayDescriptorPath(moduleId), signal, {
     forbidden: "DISPLAY_ACCESS_DENIED",
     notFound: "DISPLAY_NOT_AVAILABLE",
   });
-  const descriptor = parseHostModuleDisplay(payload).module;
-  if (descriptor.id !== moduleId) {
+  const response = parseHostModuleDisplay(payload);
+  if (response.module.id !== moduleId) {
     throw new HostProtocolError("HOST_RESPONSE_INVALID");
   }
-  return descriptor;
+  return response;
 }
 
-export type DisplayHostBootstrap =
-  | {
-      readonly status: "signed-out";
-      readonly principal: Extract<ModuleUiPrincipal, { readonly kind: "anonymous" }>;
-    }
-  | {
-      readonly status: "ready";
-      readonly descriptor: HostModuleUiDescriptor;
-      readonly principal: Extract<ModuleUiPrincipal, { readonly kind: "authenticated" }>;
-    };
+export type DisplayHostBootstrap = {
+  readonly status: "ready";
+  readonly descriptor: HostModuleUiDescriptor;
+  readonly principal: ModuleUiPrincipal;
+};
 
-/** Principal first, then protected display metadata; anonymous browsers never probe a module id. */
+/**
+ * Descriptor first, deliberately — the opposite of the Dashboard's principal-first bootstrap.
+ *
+ * The Dashboard asks who you are before asking what you may mount, because it is asking about a
+ * person and `/api/v1/principal` answers that plainly. A display cannot: a paired device is
+ * anonymous to that endpoint by design (ADR 0036), so a principal-first display would conclude that
+ * every device in the building was signed out. The descriptor is the actual authorization boundary
+ * for a display, and it reports the viewer it authorized, so one request settles both questions for
+ * a person and a device alike.
+ *
+ * A denied descriptor throws `DISPLAY_ACCESS_DENIED`, which is what the host turns into pairing.
+ */
 export async function bootstrapDisplayHost(
   config: EkklesiaHostConfig,
   moduleId: string,
   signal?: AbortSignal,
 ): Promise<DisplayHostBootstrap> {
-  const principal = await loadHostPrincipal(config, signal);
-  if (principal.kind === "anonymous") {
-    return Object.freeze({ principal, status: "signed-out" });
-  }
+  const response = await loadModuleDisplay(config, moduleId, signal);
   return Object.freeze({
-    descriptor: await loadModuleDisplay(config, moduleId, signal),
-    principal,
-    status: "ready",
+    descriptor: response.module,
+    principal: response.viewer,
+    status: "ready" as const,
   });
 }