ci: pin the Stage 0 platform harness and run every display scenario

Pin the integration harness to Zayin/Ekklesia PR 92, whose display host keeps
a live display across reconnects and returns a revoked one to pairing, and
fetch it from the repository's canonical Zayin location. With those fixes the
connectivity-blip, caching-probe, and revoke scenarios pass, so CI now runs
them too; previously they were left out because they failed.

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

CLAUDE.md

@@ -0,0 +1,82 @@
+# CLAUDE.md
+
+Guidance for Claude Code (and other coding agents) working in this repository. It points at
+authoritative sources rather than restating them, because restated details drift. Inspect the actual
+source, tests, `package.json`, and CI workflow before relying on anything here or on memory of a
+prior session.
+
+## What this repository is
+
+Signage is a first-party Ekklesia **module** in its own repository (`Zayin/Signage`). It is not part of
+the platform monorepo and vendors none of it: it builds against the published `@ekklesia/*`
+module-development packages (platform ADRs 0053 and 0054), ships as one Ekklesia Module Package
+(ADR 0049), and reaches PostgreSQL only through the Module Database ABI v1 executor the host hands it
+(ADR 0050). Read `README.md` for what exists and the scope boundaries.
+
+Signage owns its domain: channel groups, audience channels, timelines, slots, signage assignments,
+playback rules, native images, and **its own management and display UI**. The platform shell hosts
+that UI through the generic module loader and never rebuilds it; do not move Signage screens into the
+platform.
+
+## Product direction lives beside this repository
+
+The current roadmap and product/interface design contract are `ROADMAP.md` and `DESIGN.md` in the
+parent development directory (`../ROADMAP.md` and `../DESIGN.md` in the standard
+`~/development/ekklesia/` layout). They are deliberately **not** committed here; do not copy them in.
+They are authoritative for product direction. If this repository's documentation disagrees with them,
+flag the conflict and correct the repository-local documentation; never silently follow stale text.
+
+Rules from those documents that apply to every change here:
+
+- **Shared resources belong to the platform.** Displays/devices, identity, branding, mail, storage,
+  and module lifecycle are the platform's. Signage *consumes* displays; it assigns content to them.
+- **The current display management is transitional.** Signage's viewer roster, display naming, and
+  pairing instructions, together with the platform's sidebar *Display devices* panel, are what exists
+  today. Stage 1 moves pairing and the one global display name to the platform's
+  **Settings → Displays**, and Signage then selects an existing display. Fix defects in the current
+  flow, keep existing paired displays, viewer identities, cached content, and assignments working, and
+  do **not** implement the Stage 1 Settings/Displays architecture early.
+- **Branding.** Normal user-facing UI never hard-codes "Ekklesia" (platform ADR 0046).
+- **Visual direction.** Simple and minimal; responsive; light, dark, and system modes. Normal UI
+  colours come only from the shared design tokens (`@ekklesia/design-tokens`) and shared elements
+  (`@ekklesia/ui`) — never a hard-coded colour. The display artifact's pure-black stage, blackout,
+  and slate are content presentation, not themed UI.
+- **No browser-native dialogs.** `window.alert`, `window.confirm`, and `window.prompt` are prohibited.
+  Destructive actions use in-product confirmation proportional to impact: a two-step in-place
+  confirmation for moderate actions, the shared `Dialog` for significant ones.
+- **Plain language.** Normal church staff must understand the UI without implementation terms; do not
+  expose an internal identifier merely because it exists.
+
+## ADRs
+
+`docs/architecture/decisions/` holds Signage's own ADRs; the platform's ADRs live in the Ekklesia
+repository. Accepted ADRs are immutable except for status and cross-reference corrections. A changed
+decision gets a new ADR that supersedes the old one; never rewrite a historical ADR to fit a change.
+
+## Working conventions
+
+- Canonical remote: `ssh://[email protected]:2222/Zayin/Signage.git` (the platform is
+  `Zayin/Ekklesia.git`). Local clones can be behind: `git fetch --prune --tags` and branch from
+  `origin/main`.
+- One branch per PR off an up-to-date `origin/main`. Never push to `main`, never merge your own PR,
+  and never create or push a release tag — release tags belong to the human maintainer.
+- A fix that needs a platform contract change is two PRs: the Ekklesia change first, then Signage,
+  with the compatibility boundary explicit. Do not copy platform logic into Signage to avoid it.
+- Every defect fix gets a regression test. Signage never reads the environment, opens its own socket,
+  builds an Ekklesia URL, or applies a migration; all of that reaches it through the host.
+
+## Verification
+
+`package.json` and `.gitea/workflows/ci.yml` are the source of truth. From a clean checkout:
+
+```bash
+pnpm install --frozen-lockfile
+pnpm lint && pnpm typecheck && pnpm test && pnpm build && pnpm validate
+bash ci/check-cleanup.sh
+```
+
+The CI `integration` job installs the real Module Package into the pinned platform
+(`ci/platform.env`) and drives the Dashboard and a kiosk display in real browsers, running the display
+scenarios listed in `ci/display-scenarios` (`bash ci/package.sh`, `bash ci/fetch-platform.sh`,
+`bash ci/integration.sh`; it needs Docker). Unit tests passing is not evidence that a display or
+browser behaviour works: verify display behaviour through the integration harness.

README.md

@@ -139,8 +139,25 @@ description of the platform ABI.
 | Transitions, offline continuation, playback controls | Dynamic change within one slide |
 | The management and display UI | Its own internal multi-stage behaviour |
 
+## Displays today, and what Stage 1 changes
+
+Displays are platform-owned. What exists now is transitional: a screen is paired in the Dashboard
+sidebar's *Display devices* panel, and Signage keeps its own roster of the screens that have checked
+in — their names, the group and audience each is assigned to, and their health. A running display
+follows its assignment as soon as an administrator changes it, and a revoked display returns to its
+pairing code. Entries for screens that are offline (a retired television, a test tab) can be removed
+from the roster.
+
+The product roadmap moves pairing and the one global display name to the platform's
+**Settings → Displays** in Stage 1; Signage will then select an existing display instead of naming its
+own. Until then, existing paired displays, their viewer identities, cached content, and assignments are
+preserved across every Signage upgrade.
+
+The management screen is currently desktop-only (the narrow-screen notice below 1024 px). The product
+design requires phone and tablet administration and dark mode; that arrives with the Stage 1 shared
+responsive Dashboard and design system rather than as a Signage-only layout.
+
 ## Licence and scope
 
-Deployment, the module store, a theme editor, a mobile management UI, video and audio, MQTT, Home
-Assistant, Companion, and any migration of legacy Announcements data are explicitly out of scope for
-this repository.
+Deployment, the module store, a theme editor, video and audio, MQTT, Home Assistant, Companion, and any
+migration of legacy Announcements data are explicitly out of scope for this repository.

ci/display-scenarios

@@ -5,3 +5,6 @@ two-pages
 session-blip
 stream-failure
 stream-recycle
+connectivity-blip
+caching-probe
+revoke

ci/platform.env

@@ -1,5 +1,5 @@
 # The companion Core harness Signage uses to install and run its real external package. The pull ref
 # remains reachable after its branch is deleted; the full commit pin makes the checkout immutable.
-EKKLESIA_PLATFORM_REPOSITORY=https://git.riverofglorymn.org/River_of_Glory_Church/Ekklesia.git
-EKKLESIA_PLATFORM_REF=refs/pull/90/head
-EKKLESIA_PLATFORM_COMMIT=40ef0ff802c124ae5a3a0b9aa51a1502a7b72644
+EKKLESIA_PLATFORM_REPOSITORY=https://git.zayin.net/Zayin/Ekklesia.git
+EKKLESIA_PLATFORM_REF=refs/pull/92/head
+EKKLESIA_PLATFORM_COMMIT=9331a8f7dfbf8cbb6528a8bff5ba842297b1ee5a

src/browser/desktop-gate.tsx

@@ -20,7 +20,7 @@ export function DesktopOnly({ children }: { readonly children: ReactNode }): Rea
       <div className="signage-narrow-notice" data-testid="signage-narrow-notice" role="note">
         <h2 className="signage-narrow-notice__title">Signage needs a desktop screen</h2>
         <p className="signage-narrow-notice__body">
-          {`Open the Ekklesia Dashboard on a display at least ${SIGNAGE_MIN_DESKTOP_WIDTH_PX} pixels wide to manage timelines, images, channels, and playback.`}
+          {`Open this page on a screen at least ${SIGNAGE_MIN_DESKTOP_WIDTH_PX} pixels wide to manage timelines, images, displays, and playback.`}
         </p>
       </div>
       <div className="signage-desktop" data-testid="signage-desktop">

src/display/controller.ts

@@ -20,6 +20,7 @@ import {
   signageMediaKey,
 } from "../browser/storage.js";
 import {
+  assignedChannelOf,
   type DisplayChannelState,
   type DisplayHeartbeat,
   type DisplayRealtimeGroup,
@@ -110,6 +111,8 @@ export function createDisplayController(options: DisplayControllerOptions): Disp
   let stage: SceneStage | undefined;
   let session: DisplaySessionView | undefined;
   let subscription: { close(): void } | undefined;
+  /** Identifies the one subscription whose callbacks may still act. */
+  let activeSubscription: symbol | undefined;
   let heartbeatHandle: unknown;
   let refreshHandle: unknown;
   let stopped = false;
@@ -127,6 +130,13 @@ export function createDisplayController(options: DisplayControllerOptions): Disp
    * each resets once its request works again. */
   let sessionHandle: unknown;
   let sessionAttempt = 0;
+  /** One registration in flight at a time. A refresh and a heartbeat can both discover that this
+   * viewer was removed from the roster; registering twice would open two realtime subscriptions and
+   * two heartbeat timers for one screen. */
+  let registering = false;
+  /** Consecutive times this screen found itself removed from the roster without a working fetch in
+   * between. Resets once a state fetch succeeds. */
+  let rosterAttempt = 0;
   let refreshAttempt = 0;
   let realtimeHandle: unknown;
   let realtimeAttempt = 0;
@@ -347,6 +357,9 @@ export function createDisplayController(options: DisplayControllerOptions): Disp
     // The crossfade is part of the persisted state too, so a screen that resumes offline fades the
     // way its operator configured rather than the way this file happened to default.
     stage.setCrossfade(snapshot.crossfadeMs);
+    // A deliberate blackout is persisted state like any other. Restoring it first means a kiosk that
+    // reloads mid-blackout stays black while it reconnects, instead of flashing the hidden frame.
+    stage.setBlackout(snapshot.playback.blackout);
     const atMs = serverNowFrom(snapshot, now());
     const evaluation = resolveOffline({ atMs, snapshot, unusableSelectionIds: unusable });
     const resolution = evaluation.resolution;
@@ -500,22 +513,96 @@ export function createDisplayController(options: DisplayControllerOptions): Disp
     if (stopped || !session) {
       return;
     }
+    const viewerId = session.viewerId;
     try {
-      const response = await options.context.api.request(
-        `channels/${session.channelId}/display-state`,
-      );
+      // Asked by viewer, not by channel: the server resolves where this screen is assigned *now*,
+      // so a reassignment or a deleted channel reaches a display that is already running.
+      const response = await options.context.api.request(`viewers/${viewerId}/display-state`);
+      if (await removedFromRoster(response)) {
+        // This screen was removed from the roster. It registers again with the identity it keeps,
+        // and keeps its frame meanwhile.
+        reregister(viewerId);
+        return;
+      }
       if (!response.ok) {
         await refreshFailed();
         return;
       }
       const state = (await response.json()) as DisplayChannelStateView;
       refreshAttempt = 0;
+      rosterAttempt = 0;
+      adoptAssignment(state.channel);
       await apply(state);
     } catch {
       await refreshFailed();
     }
   }
 
+  /** The server's answer about where this screen belongs wins, exactly as its playback state does. */
+  function adoptAssignment(channel: DisplayChannelStateView["channel"]): void {
+    if (!session || (session.channelId === channel.id && session.groupId === channel.groupId)) {
+      return;
+    }
+    session = {
+      ...session,
+      channelId: channel.id,
+      channelKey: channel.key,
+      groupId: channel.groupId,
+    };
+  }
+
+  /**
+   * Only Signage's own "no such viewer" means the roster entry is gone. Any other 404 — a proxy, a
+   * route this server does not have — is an ordinary failure, retried with backoff like the rest;
+   * treating it as removal would re-register in a loop.
+   */
+  async function removedFromRoster(response: Response): Promise<boolean> {
+    if (response.status !== 404) {
+      return false;
+    }
+    const body = (await response
+      .clone()
+      .json()
+      .catch(() => null)) as { code?: unknown } | null;
+    return body?.code === "SIGNAGE_NOT_FOUND";
+  }
+
+  /** Drops a session the server no longer recognizes and registers again, once, on backoff. */
+  function reregister(viewerId: string): void {
+    if (stopped || session?.viewerId !== viewerId) {
+      return;
+    }
+    endSession();
+    // Backed off as well: a server that keeps forgetting this screen the moment it registers must
+    // cost a request a minute, not a tight loop.
+    const delay = rosterAttempt === 0 ? 0 : displayRetryDelayMs(rosterAttempt);
+    rosterAttempt += 1;
+    if (delay === 0) {
+      void register();
+      return;
+    }
+    sessionHandle = setTimer(() => {
+      sessionHandle = undefined;
+      void register();
+    }, delay);
+  }
+
+  /** Releases everything a registration started: realtime, heartbeats, and pending retries. */
+  function endSession(): void {
+    session = undefined;
+    activeSubscription = undefined;
+    subscription?.close();
+    subscription = undefined;
+    if (heartbeatHandle !== undefined) {
+      clearInterval(heartbeatHandle as never);
+      heartbeatHandle = undefined;
+    }
+    if (realtimeHandle !== undefined) {
+      clearTimer(realtimeHandle);
+      realtimeHandle = undefined;
+    }
+  }
+
   /**
    * The server is unreachable, or answered with an error. The frame stays and local continuation
    * takes over — nothing about a network failure belongs on a lobby wall — and the refresh is tried
@@ -545,26 +632,17 @@ export function createDisplayController(options: DisplayControllerOptions): Disp
    * state — exactly as if it had worked the first time.
    */
   async function register(): Promise<void> {
-    if (stopped || session) {
+    if (stopped || session || registering) {
       return;
     }
+    registering = true;
     let registered: DisplaySessionView | undefined;
     try {
-      const response = await options.context.api.request("viewers/session", {
-        body: JSON.stringify({ viewerKey: await viewerKey() }),
-        headers: { "content-type": "application/json" },
-        method: "POST",
-      });
-      if (response.ok) {
-        // Read, not cast: a registration the display cannot understand is no registration, and is
-        // tried again like any other failure.
-        const parsed = parseViewerSessionResponse(await response.json());
-        registered = parsed.ok ? parsed.value : undefined;
+      registered = await requestSession();
+    } finally {
+      registering = false;
     }
-    } catch {
-      registered = undefined;
-    }
-    if (stopped) {
+    if (stopped || session) {
       return;
     }
     if (!registered) {
@@ -590,6 +668,26 @@ export function createDisplayController(options: DisplayControllerOptions): Disp
     report();
   }
 
+  async function requestSession(): Promise<DisplaySessionView | undefined> {
+    let registered: DisplaySessionView | undefined;
+    try {
+      const response = await options.context.api.request("viewers/session", {
+        body: JSON.stringify({ viewerKey: await viewerKey() }),
+        headers: { "content-type": "application/json" },
+        method: "POST",
+      });
+      if (response.ok) {
+        // Read, not cast: a registration the display cannot understand is no registration, and is
+        // tried again like any other failure.
+        const parsed = parseViewerSessionResponse(await response.json());
+        registered = parsed.ok ? parsed.value : undefined;
+      }
+    } catch {
+      registered = undefined;
+    }
+    return registered;
+  }
+
   /**
    * Subscribes to the display's realtime channel, and again whenever the host reports that a
    * subscription has ended for good. The host retries ordinary disconnects itself; a stream that
@@ -600,10 +698,21 @@ export function createDisplayController(options: DisplayControllerOptions): Disp
     if (stopped || !session) {
       return;
     }
+    // Only the newest subscription may act. Closing the old one can report "closed" synchronously,
+    // and that report must not schedule a second resubscription on top of this one.
+    const token = Symbol("subscription");
+    activeSubscription = token;
     subscription?.close();
     subscription = options.context.realtime.subscribe("display-state", {
-      onSnapshot: (state) => onRealtime(state),
+      onSnapshot: (state) => {
+        if (activeSubscription === token) {
+          onRealtime(state);
+        }
+      },
       onStatus: (status) => {
+        if (activeSubscription !== token) {
+          return;
+        }
         online = status === "connected";
         if (status === "connected") {
           realtimeAttempt = 0;
@@ -616,7 +725,11 @@ export function createDisplayController(options: DisplayControllerOptions): Disp
         }
         report();
       },
-      onUpdate: (state) => onRealtime(state),
+      onUpdate: (state) => {
+        if (activeSubscription === token) {
+          onRealtime(state);
+        }
+      },
     });
   }
 
@@ -639,11 +752,29 @@ export function createDisplayController(options: DisplayControllerOptions): Disp
         reportedSelectionId: renderedSelectionId ?? null,
         reportedTimelineId: lastState?.playback.activeTimelineId ?? null,
       };
-      await options.context.api.request(`viewers/${session.viewerId}/heartbeat`, {
+      const viewerId = session.viewerId;
+      const response = await options.context.api.request(`viewers/${viewerId}/heartbeat`, {
         body: JSON.stringify(report),
         headers: { "content-type": "application/json" },
         method: "POST",
       });
+      if (await removedFromRoster(response)) {
+        reregister(viewerId);
+        return;
+      }
+      if (!response.ok) {
+        return;
+      }
+      // The heartbeat is also how a screen learns it was reassigned while its slot is long, paused,
+      // or held — times when no state fetch is otherwise due.
+      const assigned = assignedChannelOf(await response.json().catch(() => undefined));
+      if (
+        assigned !== undefined &&
+        session?.viewerId === viewerId &&
+        assigned !== session.channelId
+      ) {
+        void refresh();
+      }
     } catch {
       // Telemetry is best effort and never affects what is on screen.
     }
@@ -695,6 +826,7 @@ export function createDisplayController(options: DisplayControllerOptions): Disp
 
     async stop(): Promise<void> {
       stopped = true;
+      activeSubscription = undefined;
       subscription?.close();
       subscription = undefined;
       if (heartbeatHandle !== undefined) {

src/server/routes/viewers.ts

@@ -18,6 +18,7 @@ import {
   describeViewerHealth,
   openViewerSession,
   recordViewerHeartbeat,
+  resolveViewerSession,
   SIGNAGE_VIEWER_NAME_MAX,
   updateViewerAssignment,
 } from "../viewers/service.js";
@@ -123,12 +124,50 @@ export function registerViewerRoutes(
         });
         // The response says what a display needs to keep itself honest, and nothing about other
         // displays or the installation.
-        const response: DisplayHeartbeatResponse = { acknowledged: true, recorded: result.written };
+        const assigned = await resolveViewerSession(store(context), result.viewer);
+        const response: DisplayHeartbeatResponse = {
+          acknowledged: true,
+          channelId: assigned.channel.id,
+          recorded: result.written,
+        };
         return Response.json(response);
       });
     },
   });
 
+  http.route({
+    method: "GET",
+    path: "/viewers/:viewerId/display-state",
+    permission: "signage.display.view",
+    maxBodyBytes: 0,
+    handler(_request, context) {
+      return signageBoundary(async () => {
+        const viewerId = requireUuidParam(context, "viewerId");
+        const signageStore = store(context);
+        const viewer = await signageStore.findViewer(viewerId);
+        if (!viewer) {
+          // Removed from the roster. The display registers again with the identity it keeps.
+          throw new SignageError("SIGNAGE_NOT_FOUND");
+        }
+        // Resolved on every fetch, never remembered from registration: an administrator who moves
+        // a screen, or deletes the channel it was on, changes what it shows without a reboot.
+        const { channel } = await resolveViewerSession(signageStore, viewer);
+        const snapshot = await playback().snapshot(channel.groupId);
+        return Response.json(
+          await buildDisplayChannelState({
+            atMs: Date.now(),
+            channel,
+            playback: snapshot,
+            registry: registry(),
+            settings: readSignageSettings(context.config),
+            storage: context.storage,
+            store: signageStore,
+          }),
+        );
+      });
+    },
+  });
+
   http.route({
     method: "GET",
     path: "/channels/:channelId/display-state",

src/server/viewers/service.ts

@@ -87,7 +87,7 @@ export async function openViewerSession(input: ViewerSessionInput): Promise<View
     if (!refreshed) {
       throw new SignageError("SIGNAGE_OPERATION_FAILED");
     }
-    return resolveSession(input.store, refreshed);
+    return resolveViewerSession(input.store, refreshed);
   }
 
   const channel = defaultChannelOf(group.channels);
@@ -121,7 +121,16 @@ function defaultChannelOf(channels: readonly StoredChannel[]): StoredChannel {
   return fallback;
 }
 
-async function resolveSession(store: SignageStore, viewer: StoredViewer): Promise<ViewerSession> {
+/**
+ * Where a known viewer is assigned **now**: its own channel, or the default channel of the default
+ * group when that channel no longer exists. A display asks this on every state fetch, which is what
+ * makes an administrator's reassignment — or deleting the channel a screen was on — reach a display
+ * that is already running, rather than only the next time it boots.
+ */
+export async function resolveViewerSession(
+  store: SignageStore,
+  viewer: StoredViewer,
+): Promise<ViewerSession> {
   const groups = await store.listChannelGroups();
   for (const group of groups) {
     const channel = group.channels.find((candidate) => candidate.id === viewer.channelId);

src/shared/display-protocol.ts

@@ -206,9 +206,28 @@ export function parseDisplayHeartbeat(raw: unknown): ProtocolResult<DisplayHeart
 export interface DisplayHeartbeatResponse {
   readonly acknowledged: true;
   readonly recorded: boolean;
+  /** The channel an administrator has this viewer assigned to now. A display whose own idea of its
+   * channel differs refetches its state, so a reassignment reaches a running screen within one
+   * heartbeat. Optional: a display ignores a response without it. */
+  readonly channelId?: string;
 }
 
-// --- Channel state: GET channels/:channelId/display-state -----------------------------------------
+/** The assigned channel from a heartbeat response, if it carried a usable one. */
+export function assignedChannelOf(raw: unknown): string | undefined {
+  if (typeof raw !== "object" || raw === null) {
+    return undefined;
+  }
+  const channelId = (raw as { readonly channelId?: unknown }).channelId;
+  return typeof channelId === "string" && channelId.length > 0 && channelId.length <= 64
+    ? channelId
+    : undefined;
+}
+
+// --- Channel state: GET viewers/:viewerId/display-state (and channels/:channelId/display-state) -----
+//
+// A registered display asks by its own viewer id, so the server resolves which channel it is assigned
+// to at that moment. The channel route remains for the management preview and for display code a
+// kiosk cached before the viewer route existed.
 
 /** A fresh, signed delivery URL. A bearer capability with an expiry: never persisted by a display. */
 export interface DisplayMedia {

src/ui/SignageDashboard.tsx

@@ -1,9 +1,9 @@
 import type { ModuleUiHostContext } from "@ekklesia/module-ui-sdk";
 import { EkklesiaUiStyles, EmptyState, PageHeader, Tabs } from "@ekklesia/ui";
-import { type ReactElement, useMemo, useState } from "react";
+import { type ReactElement, useContext, useMemo, useState } from "react";
 import { DesktopOnly } from "../browser/desktop-gate.js";
 import { createSignageApi } from "./api.js";
-import { useResource } from "./hooks.js";
+import { createResourceCache, ResourceCacheContext, useResource } from "./hooks.js";
 import { DisplaysPanel } from "./panels/DisplaysPanel.js";
 import { ImagesPanel } from "./panels/ImagesPanel.js";
 import { PlaybackPanel } from "./panels/PlaybackPanel.js";
@@ -22,7 +22,20 @@ import type { ChannelGroupView, SettingsResponse } from "./types.js";
  * Permission checks here decide what an operator is *offered*. The server decides what happens: a
  * hidden button is a courtesy, and every route is enforced regardless of what this believes.
  */
-export function SignageDashboard({
+export function SignageDashboard(props: {
+  readonly context: ModuleUiHostContext;
+  readonly copyText: (value: string) => Promise<void>;
+}): ReactElement {
+  // One cache for the life of this screen: everything the panels have loaded, shared between them.
+  const [cache] = useState(createResourceCache);
+  return (
+    <ResourceCacheContext.Provider value={cache}>
+      <SignageWorkspace {...props} />
+    </ResourceCacheContext.Provider>
+  );
+}
+
+function SignageWorkspace({
   context,
   copyText,
 }: {
@@ -30,16 +43,15 @@ export function SignageDashboard({
   readonly copyText: (value: string) => Promise<void>;
 }): ReactElement {
   const api = useMemo(() => createSignageApi(context.api), [context.api]);
+  const cache = useContext(ResourceCacheContext);
   // Read before the resources below, so a viewer who may not see Signage at all asks for nothing.
   // A hidden screen is a usability choice; the server is what actually refuses, and making a
   // request it will certainly refuse is noise in a log rather than security.
   const mayView = context.permissions.has("signage.view");
   const settings = useResource(
-		() =>
-			mayView
-				? api.get<SettingsResponse>("settings")
-				: Promise.resolve(undefined),
+    () => (mayView ? api.get<SettingsResponse>("settings") : Promise.resolve(undefined)),
     [mayView],
+    mayView ? "settings" : undefined,
   );
   const groups = useResource(
     () =>
@@ -47,14 +59,13 @@ export function SignageDashboard({
         ? api.get<{ groups: readonly ChannelGroupView[] }>("channel-groups")
         : Promise.resolve(undefined),
     [mayView],
+    mayView ? "channel-groups" : undefined,
   );
   const [tab, setTab] = useState("playback");
   const [groupId, setGroupId] = useState<string | undefined>(undefined);
 
   const mayManageAssets = context.permissions.has("signage.assets.manage");
-	const mayManageTimelines = context.permissions.has(
-		"signage.timelines.manage",
-	);
+  const mayManageTimelines = context.permissions.has("signage.timelines.manage");
   const mayControl = context.permissions.has("signage.playback.control");
   const mayManageDisplays = context.permissions.has("signage.displays.manage");
 
@@ -68,15 +79,10 @@ export function SignageDashboard({
   }
 
   const selectedGroupId =
-		groupId ??
-		(groups.state.status === "ready"
-			? groups.state.value?.groups[0]?.id
-			: undefined);
+    groupId ?? (groups.state.status === "ready" ? groups.state.value?.groups[0]?.id : undefined);
   const selectedGroup =
     groups.state.status === "ready"
-			? groups.state.value?.groups.find(
-					(candidate) => candidate.id === selectedGroupId,
-				)
+      ? groups.state.value?.groups.find((candidate) => candidate.id === selectedGroupId)
       : undefined;
 
   return (
@@ -118,8 +124,7 @@ export function SignageDashboard({
                           {...(selectedGroup
                             ? {
                                 activeGroupName: selectedGroup.name,
-																activeTimelineId:
-																	selectedGroup.playback.activeTimelineId,
+                                activeTimelineId: selectedGroup.playback.activeTimelineId,
                               }
                             : {})}
                           api={api}
@@ -127,13 +132,15 @@ export function SignageDashboard({
                           onActivate={
                             mayControl && selectedGroupId !== undefined
                               ? async (timelineId) => {
-																	await api.send(
-																		"POST",
-																		`playback/${selectedGroupId}/activate`,
-																		{
+                                  await api.send("POST", `playback/${selectedGroupId}/activate`, {
                                     timelineId,
                                     when: "now",
-																		},
+                                  });
+                                  // Playback opens on what is now true, not on the
+                                  // timeline it was showing before.
+                                  cache?.write(
+                                    `playback/${selectedGroupId}`,
+                                    await api.get(`playback/${selectedGroupId}`),
                                   );
                                   groups.reload();
                                   setTab("playback");
@@ -148,11 +155,7 @@ export function SignageDashboard({
                     },
                     {
                       content: (
-												<ImagesPanel
-													api={api}
-													canManage={mayManageAssets}
-													settings={loaded}
-												/>
+                        <ImagesPanel api={api} canManage={mayManageAssets} settings={loaded} />
                       ),
                       id: "images",
                       label: "Images",
@@ -174,13 +177,7 @@ export function SignageDashboard({
                       label: "Displays",
                     },
                     {
-											content: (
-												<ProvidersPanel
-													api={api}
-													context={context}
-													settings={loaded}
-												/>
-											),
+                      content: <ProvidersPanel api={api} context={context} settings={loaded} />,
                       id: "providers",
                       label: "Providers",
                     },

src/ui/hooks.ts

@@ -1,4 +1,4 @@
-import { useCallback, useEffect, useRef, useState } from "react";
+import { createContext, useCallback, useContext, useEffect, useRef, useState } from "react";
 import { type SignageApiFailure, SignageRequestError } from "./api.js";
 
 /**
@@ -21,15 +21,76 @@ export interface Resource<Value> {
   reload(): void;
 }
 
+/**
+ * The last value each Signage resource loaded, shared by every panel on the screen.
+ *
+ * The tabs mount only the selected panel, so without this every tab switch threw its data away,
+ * flashed a spinner, and collapsed the page to its height before growing again — the "jumping" an
+ * operator saw. It also let two panels disagree: activating a timeline from Playback left Timelines
+ * showing the old one as inactive until a reload. Now a remounted panel starts from what was last
+ * known and refreshes quietly, and a reload anywhere updates every panel reading the same resource.
+ */
+export interface ResourceCache {
+  read(key: string): { readonly value: unknown } | undefined;
+  write(key: string, value: unknown): void;
+  subscribe(key: string, listener: (value: unknown) => void): () => void;
+}
+
+export function createResourceCache(): ResourceCache {
+  const values = new Map<string, { readonly value: unknown }>();
+  const listeners = new Map<string, Set<(value: unknown) => void>>();
+  return {
+    read: (key) => values.get(key),
+    subscribe(key, listener) {
+      const set = listeners.get(key) ?? new Set();
+      set.add(listener);
+      listeners.set(key, set);
+      return () => {
+        set.delete(listener);
+        if (set.size === 0) {
+          listeners.delete(key);
+        }
+      };
+    },
+    write(key, value) {
+      values.set(key, { value });
+      for (const listener of [...(listeners.get(key) ?? [])]) {
+        listener(value);
+      }
+    },
+  };
+}
+
+export const ResourceCacheContext = createContext<ResourceCache | undefined>(undefined);
+
 export function useResource<Value>(
   load: () => Promise<Value>,
   dependencies: readonly unknown[],
+  /** Shares this resource with every other panel that names the same key. */
+  key?: string,
 ): Resource<Value> {
-  const [state, setState] = useState<Loadable<Value>>({ status: "loading" });
+  const cache = useContext(ResourceCacheContext);
+  const cached = key === undefined ? undefined : cache?.read(key);
+  const [state, setState] = useState<Loadable<Value>>(
+    cached === undefined
+      ? { status: "loading" }
+      : { status: "ready", value: cached.value as Value },
+  );
   const generation = useRef(0);
   const loadRef = useRef(load);
   loadRef.current = load;
 
+  useEffect(() => {
+    if (key === undefined || !cache) {
+      return;
+    }
+    const current = cache.read(key);
+    if (current !== undefined) {
+      setState({ status: "ready", value: current.value as Value });
+    }
+    return cache.subscribe(key, (value) => setState({ status: "ready", value: value as Value }));
+  }, [cache, key]);
+
   const run = useCallback(() => {
     generation.current += 1;
     const token = generation.current;
@@ -38,7 +99,13 @@ export function useResource<Value>(
       .then((value) => {
         // A response from a request the panel has already moved on from must never overwrite a
         // newer one.
-        if (token === generation.current) {
+        if (token !== generation.current) {
+          return;
+        }
+        if (key !== undefined && cache) {
+          // Every panel subscribed to this key, including this one, is updated by the write.
+          cache.write(key, value);
+        } else {
           setState({ status: "ready", value });
         }
       })
@@ -58,7 +125,7 @@ export function useResource<Value>(
           status: "failed",
         });
       });
-  }, []);
+  }, [cache, key]);
 
   // The caller's dependency list is spread deliberately: a resource reloads when *its* inputs
   // change, which is the whole reason this takes one.

src/ui/index.tsx

@@ -24,9 +24,7 @@ export default defineModuleUi({
         context={context}
         copyText={async (value) => {
           if (globalThis.navigator.clipboard === undefined) {
-						throw new Error(
-							"Clipboard access is not available in this browser.",
-						);
+            throw new Error("Clipboard access is not available in this browser.");
           }
           await globalThis.navigator.clipboard.writeText(value);
         }}

src/ui/panels/DisplaysPanel.tsx

@@ -1,31 +1,42 @@
-import {
-	Badge,
-	Button,
-	Field,
-	InlineNotice,
-	Panel,
-	Select,
-	TextInput,
-} from "@ekklesia/ui";
+import { Badge, Button, Field, InlineNotice, Panel, Select, TextInput } from "@ekklesia/ui";
 import { type ReactElement, useState } from "react";
 import type { SignageApi } from "../api.js";
 import { useAction, useResource, useTick } from "../hooks.js";
 import type { ChannelGroupView, ViewerHealthView } from "../types.js";
-import {
-	FailureNote,
-	formatSince,
-	OnlineBadge,
-	renderLoadable,
-} from "./shared.js";
+import { ConfirmButton, FailureNote, formatSince, OnlineBadge, renderLoadable } from "./shared.js";
 
 const AUDIENCE_KEY = /^[a-z][a-z0-9]*(?:-[a-z0-9]+)*$/u;
 
+/**
+ * The key content providers use to pick an audience's version of a slide, derived from the name an
+ * operator typed. It is an implementation detail: staff name an audience ("Online"), and only an
+ * operator who knows a provider expects a particular key needs the Advanced override.
+ */
+export function audienceKeyFor(name: string, taken: readonly string[]): string {
+  const base =
+    name
+      .normalize("NFKD")
+      .toLowerCase()
+      .replace(/[^a-z0-9]+/gu, "-")
+      .replace(/^-+|-+$/gu, "")
+      .slice(0, 48)
+      .replace(/-+$/u, "") || "audience";
+  const start = /^[a-z]/u.test(base) ? base : `audience-${base}`;
+  const reserved = new Set([...taken, "default"]);
+  let candidate = start;
+  for (let suffix = 2; reserved.has(candidate); suffix += 1) {
+    candidate = `${start}-${suffix}`;
+  }
+  return candidate;
+}
+
 function DisplayRow({
   canManage,
   groups,
   nowMs,
   onChannelChange,
   onNameChange,
+  onRemove,
   viewer,
 }: {
   readonly canManage: boolean;
@@ -33,31 +44,32 @@ function DisplayRow({
   readonly nowMs: number;
   readonly onChannelChange: (channelId: string) => void;
   readonly onNameChange: (name: string) => void;
+  readonly onRemove: () => void;
   readonly viewer: ViewerHealthView;
 }): ReactElement {
   return (
-		<div
-			className="signage-display-row"
-			data-testid={`signage-display-${viewer.id}`}
-		>
+    <div className="signage-display-row" data-testid={`signage-display-${viewer.id}`}>
       <div className="signage-display-row__identity">
         {canManage ? (
           <TextInput
             aria-label={`Name for ${viewer.name}`}
             defaultValue={viewer.name}
             onBlur={(event) =>
-							event.target.value !== viewer.name &&
-							onNameChange(event.target.value)
+              event.target.value !== viewer.name && onNameChange(event.target.value)
             }
           />
         ) : (
           <strong>{viewer.name}</strong>
         )}
         <OnlineBadge online={viewer.online} />
+        {viewer.deviceId === null ? (
+          // Opened by someone signed in — a test tab on a laptop, not a paired screen.
+          <Badge tone="neutral">Signed-in browser</Badge>
+        ) : undefined}
       </div>
       <div className="signage-display-row__assignment">
         {canManage ? (
-					<Field label="Audience channel">
+          <Field label="Audience">
             {(control) => (
               <Select
                 {...control}
@@ -82,18 +94,22 @@ function DisplayRow({
       <div className="signage-display-row__health">
         <span>{`Seen ${formatSince(viewer.lastSeenAtMs, nowMs)}`}</span>
         <Badge tone={viewer.offlineReady ? "success" : "neutral"}>
-					{viewer.offlineReady
-						? `${viewer.cachedAssetCount} cached`
-						: "Not offline ready"}
+          {viewer.offlineReady ? `${viewer.cachedAssetCount} cached` : "Not offline ready"}
         </Badge>
         {viewer.lastError === null ? undefined : (
-					<span
-						className="signage-display-row__error"
-						title={viewer.lastError.detail ?? undefined}
-					>
+          <span className="signage-display-row__error" title={viewer.lastError.detail ?? undefined}>
             {viewer.lastError.code}
           </span>
         )}
+        {canManage && !viewer.online ? (
+          // Only an offline entry: a screen that is still connected would simply reappear.
+          <ConfirmButton
+            confirmLabel="Remove from the list"
+            label="Remove"
+            onConfirm={onRemove}
+            testId={`signage-display-remove-${viewer.id}`}
+          />
+        ) : undefined}
       </div>
     </div>
   );
@@ -119,10 +135,12 @@ export function DisplaysPanel({
   const groups = useResource(
     () => api.get<{ groups: readonly ChannelGroupView[] }>("channel-groups"),
     [],
+    "channel-groups",
   );
   const viewers = useResource(
     () => api.get<{ viewers: readonly ViewerHealthView[] }>("viewers"),
     [],
+    "viewers",
   );
   const edit = useAction(() => {
     groups.reload();
@@ -131,12 +149,8 @@ export function DisplaysPanel({
   });
   const viewerEdit = useAction(viewers.reload);
   const [groupName, setGroupName] = useState("");
-	const [copyStatus, setCopyStatus] = useState<"copied" | "failed" | "idle">(
-		"idle",
-	);
-	const [confirmGroupId, setConfirmGroupId] = useState<string | undefined>(
-		undefined,
-	);
+  const [copyStatus, setCopyStatus] = useState<"copied" | "failed" | "idle">("idle");
+  const [confirmGroupId, setConfirmGroupId] = useState<string | undefined>(undefined);
   const [channelDraft, setChannelDraft] = useState<{
     groupId: string;
     key: string;
@@ -148,15 +162,14 @@ export function DisplaysPanel({
   });
   useTick(5000);
   const nowMs = Date.now();
-	const readyViewers =
-		viewers.state.status === "ready" ? viewers.state.value.viewers : [];
+  const readyViewers = viewers.state.status === "ready" ? viewers.state.value.viewers : [];
 
-	const updateViewer = (
-		viewerId: string,
-		changes: Record<string, string>,
-	): void => {
+  const updateViewer = (viewerId: string, changes: Record<string, string>): void => {
     viewerEdit.run(() => api.send("PATCH", `viewers/${viewerId}`, changes));
   };
+  const removeViewer = (viewerId: string): void => {
+    viewerEdit.run(() => api.send("DELETE", `viewers/${viewerId}`));
+  };
 
   return (
     <div className="signage-columns">
@@ -164,14 +177,6 @@ export function DisplaysPanel({
         actions={
           displaySetupUrl === undefined ? undefined : (
             <div className="signage-pairing-actions">
-							<a
-								className="ek-button ek-focusable ek-button--primary"
-								href={displaySetupUrl}
-								rel="noopener noreferrer"
-								target="_blank"
-							>
-								Open display setup
-							</a>
               <Button
                 onClick={() => {
                   setCopyStatus("idle");
@@ -180,35 +185,39 @@ export function DisplaysPanel({
                     () => setCopyStatus("failed"),
                   );
                 }}
+                variant="primary"
               >
-								Copy URL
+                Copy setup address
               </Button>
+              <a
+                className="ek-button ek-focusable ek-button--secondary"
+                href={displaySetupUrl}
+                rel="noopener noreferrer"
+                target="_blank"
+              >
+                Preview here
+              </a>
             </div>
           )
         }
         description="Connect a screen in three short steps."
         title="Pair a display"
       >
-				<ol
-					className="signage-pairing-steps"
-					aria-label="Display pairing steps"
-				>
+        <ol className="signage-pairing-steps" aria-label="Display pairing steps">
           <li>
             <span className="signage-pairing-steps__number">1</span>
             <span>
-							Open display setup on the screen that will show signage.
+              On the screen that will show signage, open the display setup address. Copy it from
+              here; opening it on this computer only previews the display.
             </span>
           </li>
           <li>
             <span className="signage-pairing-steps__number">2</span>
-						<span>
-							Enter its six-digit code under Display devices in the Dashboard
-							sidebar.
-						</span>
+            <span>Enter its six-digit code under Display devices in the Dashboard sidebar.</span>
           </li>
           <li>
             <span className="signage-pairing-steps__number">3</span>
-						<span>Name the display and choose its audience channel below.</span>
+            <span>Name the display and choose its group below.</span>
           </li>
         </ol>
         {displaySetupUrl === undefined ? (
@@ -218,18 +227,15 @@ export function DisplaysPanel({
         ) : undefined}
         <span className="signage-copy-status" aria-live="polite">
           {copyStatus === "copied"
-						? "Display setup URL copied."
+            ? "Display setup address copied."
             : copyStatus === "failed"
-							? "Could not copy the URL. Copy it from the newly opened setup page."
+              ? "Could not copy the address. Use Preview here and copy it from the address bar."
               : ""}
         </span>
-				{viewers.state.status === "ready" &&
-				viewers.state.value.viewers.length === 0 ? (
+        {viewers.state.status === "ready" && viewers.state.value.viewers.length === 0 ? (
           <div className="signage-display-empty">
             <strong>No displays paired yet</strong>
-						<span>
-							A newly approved screen appears below in its assigned channel.
-						</span>
+            <span>A newly approved screen appears below in its assigned channel.</span>
           </div>
         ) : undefined}
       </Panel>
@@ -265,21 +271,17 @@ export function DisplaysPanel({
             </div>
           ) : undefined
         }
-				description="A channel group shares one playback clock. Each audience channel can receive a different content variant."
+        description="Displays in one group play together, on the same slide at the same moment. Use another group for screens that should run their own loop."
         title="Channel groups and displays"
       >
         {renderLoadable(
           groups.state,
           (value) => {
             const knownChannelIds = new Set(
-							value.groups.flatMap((group) =>
-								group.channels.map((channel) => channel.id),
-							),
+              value.groups.flatMap((group) => group.channels.map((channel) => channel.id)),
             );
             const unassigned = readyViewers.filter(
-							(viewer) =>
-								viewer.channelId === null ||
-								!knownChannelIds.has(viewer.channelId),
+              (viewer) => viewer.channelId === null || !knownChannelIds.has(viewer.channelId),
             );
             return (
               <div className="signage-groups" data-testid="signage-groups">
@@ -287,9 +289,7 @@ export function DisplaysPanel({
                   <article className="signage-group" key={group.id}>
                     <header className="signage-group__header">
                       <div className="signage-group__identity">
-												<span className="signage-hierarchy-label">
-													Channel group
-												</span>
+                        <span className="signage-hierarchy-label">Channel group</span>
                         <h3>{group.name}</h3>
                       </div>
                       <Badge tone="info">{group.playback.transport}</Badge>
@@ -308,9 +308,8 @@ export function DisplaysPanel({
                     {confirmGroupId === group.id ? (
                       <div className="signage-confirm" role="alert">
                         <p>
-													Delete {group.name}? Its playback history will be
-													removed. Displays assigned here will move to the
-													default channel of another group.
+                          Delete {group.name}? Its playback history will be removed. Displays
+                          assigned here will move to the default channel of another group.
                         </p>
                         <Button
                           disabled={edit.pending}
@@ -322,10 +321,7 @@ export function DisplaysPanel({
                           disabled={edit.pending}
                           onClick={() =>
                             edit.run(async () => {
-															await api.send(
-																"DELETE",
-																`channel-groups/${group.id}`,
-															);
+                              await api.send("DELETE", `channel-groups/${group.id}`);
                               setConfirmGroupId(undefined);
                             })
                           }
@@ -339,13 +335,14 @@ export function DisplaysPanel({
                     <section className="signage-audiences">
                       <div className="signage-audiences__heading">
                         <div>
-													<span className="signage-hierarchy-label">
-														Audience channels
-													</span>
-													<h4>Who this group renders for</h4>
+                          <span className="signage-hierarchy-label">Audiences</span>
+                          <h4>Who is watching these displays</h4>
                         </div>
                         <span>
-													Displays inherit the channel they are assigned to.
+                          Every display in this group shows the same slide at the same moment. Add
+                          an audience only when some screens should get a different version of it,
+                          such as wording for people watching online. Images look the same for every
+                          audience.
                         </span>
                       </div>
                       <div className="signage-channel-list">
@@ -354,51 +351,39 @@ export function DisplaysPanel({
                             (viewer) => viewer.channelId === channel.id,
                           );
                           return (
-														<article
-															className="signage-channel"
-															key={channel.id}
-														>
+                            <article className="signage-channel" key={channel.id}>
                               <header className="signage-channel__header">
                                 <div>
                                   <h5>{channel.name}</h5>
                                   <div className="signage-channel__meta">
                                     {channel.isDefault ? (
-																			<Badge tone="success">
-																				Default channel
-																			</Badge>
+                                      <Badge tone="success">Default audience</Badge>
                                     ) : undefined}
-																		<span>Audience key</span>
-																		<code>{channel.key}</code>
                                     <Badge tone="neutral">
                                       {`${assigned.length} display${assigned.length === 1 ? "" : "s"}`}
                                     </Badge>
                                   </div>
                                 </div>
                                 {canManage && !channel.isDefault ? (
-																	<Button
-																		disabled={edit.pending}
-																		onClick={() =>
-																			edit.run(() =>
-																				api.send(
-																					"DELETE",
-																					`channels/${channel.id}`,
-																				),
-																			)
+                                  <ConfirmButton
+                                    confirmLabel={
+                                      assigned.length === 0
+                                        ? `Remove ${channel.name}`
+                                        : `Remove ${channel.name} and move its displays to the default audience`
                                     }
-																		variant="danger"
-																	>
-																		Remove channel
-																	</Button>
+                                    disabled={edit.pending}
+                                    label="Remove audience"
+                                    onConfirm={() =>
+                                      edit.run(() => api.send("DELETE", `channels/${channel.id}`))
+                                    }
+                                    testId={`signage-channel-remove-${channel.id}`}
+                                  />
                                 ) : undefined}
                               </header>
                               <div className="signage-channel__displays">
-																<span className="signage-hierarchy-label">
-																	Displays
-																</span>
+                                <span className="signage-hierarchy-label">Displays</span>
                                 {assigned.length === 0 ? (
-																	<p className="signage-channel__empty">
-																		No displays assigned.
-																	</p>
+                                  <p className="signage-channel__empty">No displays assigned.</p>
                                 ) : (
                                   assigned.map((viewer) => (
                                     <DisplayRow
@@ -409,9 +394,8 @@ export function DisplaysPanel({
                                       onChannelChange={(channelId) =>
                                         updateViewer(viewer.id, { channelId })
                                       }
-																			onNameChange={(name) =>
-																				updateViewer(viewer.id, { name })
-																			}
+                                      onNameChange={(name) => updateViewer(viewer.id, { name })}
+                                      onRemove={() => removeViewer(viewer.id)}
                                       viewer={viewer}
                                     />
                                   ))
@@ -423,19 +407,14 @@ export function DisplaysPanel({
                       </div>
 
                       {canManage ? (
-												<div
-													className="signage-channel-form"
-													data-testid="signage-add-channel"
-												>
+                        <div className="signage-channel-form" data-testid="signage-add-channel">
                           <div className="signage-channel-form__heading">
-														<h5>Add an audience channel</h5>
-														<span>
-															The default channel always remains available.
-														</span>
+                            <h5>Add an audience</h5>
+                            <span>The default audience always remains.</span>
                           </div>
                           <Field
-														hint="Shown to administrators and when assigning displays."
-														label="Channel name"
+                            hint="Shown when you assign displays, for example Online."
+                            label="Audience name"
                           >
                             {(control) => (
                               <TextInput
@@ -444,25 +423,23 @@ export function DisplaysPanel({
                                 onChange={(event) =>
                                   setChannelDraft((current) => ({
                                     groupId: group.id,
-																		key:
-																			current.groupId === group.id
-																				? current.key
-																				: "",
+                                    key: current.groupId === group.id ? current.key : "",
                                     name: event.target.value,
                                   }))
                                 }
-																placeholder="Online audience"
-																value={
-																	channelDraft.groupId === group.id
-																		? channelDraft.name
-																		: ""
-																}
+                                placeholder="Online"
+                                value={channelDraft.groupId === group.id ? channelDraft.name : ""}
                               />
                             )}
                           </Field>
+                          <details className="signage-advanced">
+                            <summary>Advanced</summary>
                             <Field
-														hint="Advanced: lowercase ID sent to content providers, e.g. online."
-														label="Audience key"
+                              hint={`Only needed when a content module expects a particular key. Leave empty to use ${audienceKeyFor(
+                                channelDraft.groupId === group.id ? channelDraft.name : "",
+                                group.channels.map((channel) => channel.key),
+                              )}.`}
+                              label="Content key"
                             >
                               {(control) => (
                                 <TextInput
@@ -472,40 +449,35 @@ export function DisplaysPanel({
                                     setChannelDraft((current) => ({
                                       groupId: group.id,
                                       key: event.target.value,
-																		name:
-																			current.groupId === group.id
-																				? current.name
-																				: "",
+                                      name: current.groupId === group.id ? current.name : "",
                                     }))
                                   }
                                   pattern="[a-z][a-z0-9]*(?:-[a-z0-9]+)*"
-																placeholder="online"
-																value={
-																	channelDraft.groupId === group.id
-																		? channelDraft.key
-																		: ""
-																}
+                                  value={channelDraft.groupId === group.id ? channelDraft.key : ""}
                                 />
                               )}
                             </Field>
+                          </details>
                           <Button
                             disabled={
                               edit.pending ||
                               channelDraft.groupId !== group.id ||
-															!AUDIENCE_KEY.test(channelDraft.key.trim()) ||
-															channelDraft.key.trim() === "default" ||
-															channelDraft.name.trim() === ""
+                              channelDraft.name.trim() === "" ||
+                              (channelDraft.key.trim() !== "" &&
+                                (!AUDIENCE_KEY.test(channelDraft.key.trim()) ||
+                                  channelDraft.key.trim() === "default"))
                             }
                             onClick={() =>
                               edit.run(async () => {
-																await api.send(
-																	"POST",
-																	`channel-groups/${group.id}/channels`,
-																	{
-																		key: channelDraft.key.trim(),
+                                await api.send("POST", `channel-groups/${group.id}/channels`, {
+                                  key:
+                                    channelDraft.key.trim() ||
+                                    audienceKeyFor(
+                                      channelDraft.name,
+                                      group.channels.map((channel) => channel.key),
+                                    ),
                                   name: channelDraft.name.trim(),
-																	},
-																);
+                                });
                                 setChannelDraft({
                                   groupId: "",
                                   key: "",
@@ -515,7 +487,7 @@ export function DisplaysPanel({
                             }
                             variant="primary"
                           >
-														Add channel
+                            Add audience
                           </Button>
                         </div>
                       ) : undefined}
@@ -525,21 +497,16 @@ export function DisplaysPanel({
 
                 {unassigned.length === 0 ? undefined : (
                   <section className="signage-unassigned">
-										<span className="signage-hierarchy-label">
-											Needs assignment
-										</span>
+                    <span className="signage-hierarchy-label">Needs assignment</span>
                     {unassigned.map((viewer) => (
                       <DisplayRow
                         canManage={canManage}
                         groups={value.groups}
                         key={viewer.id}
                         nowMs={nowMs}
-												onChannelChange={(channelId) =>
-													updateViewer(viewer.id, { channelId })
-												}
-												onNameChange={(name) =>
-													updateViewer(viewer.id, { name })
-												}
+                        onChannelChange={(channelId) => updateViewer(viewer.id, { channelId })}
+                        onNameChange={(name) => updateViewer(viewer.id, { name })}
+                        onRemove={() => removeViewer(viewer.id)}
                         viewer={viewer}
                       />
                     ))}

src/ui/panels/ImagesPanel.tsx

@@ -9,7 +9,7 @@ import {
 import type { SignageApi } from "../api.js";
 import { useAction, useResource } from "../hooks.js";
 import type { ImageRecord, SettingsResponse } from "../types.js";
-import { FailureNote, formatInstant, renderLoadable } from "./shared.js";
+import { ConfirmButton, FailureNote, formatInstant, renderLoadable } from "./shared.js";
 
 /**
  * The native image library and its upload queue.
@@ -28,7 +28,11 @@ export function ImagesPanel({
   readonly settings: SettingsResponse;
   readonly canManage: boolean;
 }): ReactElement {
-  const images = useResource(() => api.get<{ images: readonly ImageRecord[] }>("images"), []);
+  const images = useResource(
+    () => api.get<{ images: readonly ImageRecord[] }>("images"),
+    [],
+    "images",
+  );
   const [uploads, setUploads] = useState<readonly UploadItem[]>([]);
   const queueRef = useRef<UploadQueue | undefined>(undefined);
   const [renaming, setRenaming] = useState<{ id: string; value: string } | undefined>(undefined);
@@ -204,13 +208,15 @@ export function ImagesPanel({
                             Rename
                           </Button>
                         )}
-                        <Button
+                        <ConfirmButton
+                          confirmLabel="Delete this image"
                           disabled={remove.pending}
-                          onClick={() => remove.run(() => api.send("DELETE", `images/${image.id}`))}
-                          variant="danger"
-                        >
-                          Delete
-                        </Button>
+                          label="Delete"
+                          onConfirm={() =>
+                            remove.run(() => api.send("DELETE", `images/${image.id}`))
+                          }
+                          testId={`signage-image-delete-${image.id}`}
+                        />
                       </div>
                     ) : undefined}
                   </li>

src/ui/panels/PlaybackPanel.tsx

@@ -1,14 +1,6 @@
 import type { ModuleUiHostContext } from "@ekklesia/module-ui-sdk";
-import {
-	ActionBar,
-	Badge,
-	Button,
-	EmptyState,
-	Field,
-	Panel,
-	Select,
-} from "@ekklesia/ui";
-import { type ReactElement, useState } from "react";
+import { ActionBar, Badge, Button, EmptyState, Field, Panel, Select } from "@ekklesia/ui";
+import { type ReactElement, useEffect, useRef, useState } from "react";
 import type { SignageApi } from "../api.js";
 import { useAction, useResource, useTick } from "../hooks.js";
 import type {
@@ -18,12 +10,7 @@ import type {
   TimelineSummary,
 } from "../types.js";
 import { PreviewPanel } from "./PreviewPanel.js";
-import {
-	FailureNote,
-	formatDuration,
-	formatInstant,
-	renderLoadable,
-} from "./shared.js";
+import { FailureNote, formatDuration, formatInstant, renderLoadable } from "./shared.js";
 
 /**
  * Live transport for one channel group.
@@ -50,10 +37,12 @@ export function PlaybackPanel({
   const groups = useResource(
     () => api.get<{ groups: readonly ChannelGroupView[] }>("channel-groups"),
     [],
+    "channel-groups",
   );
   const timelines = useResource(
     () => api.get<{ timelines: readonly TimelineSummary[] }>("timelines"),
     [],
+    "timelines",
   );
   const detail = useResource(
     () =>
@@ -61,6 +50,7 @@ export function PlaybackPanel({
         ? Promise.resolve(undefined)
         : api.get<PlaybackDetailView>(`playback/${groupId}`),
     [groupId],
+    groupId === undefined ? undefined : `playback/${groupId}`,
   );
   const command = useAction(() => {
     detail.reload();
@@ -75,6 +65,10 @@ export function PlaybackPanel({
       : undefined;
   // A one-second tick so the remaining time counts down rather than sitting still between refreshes.
   useTick(1000);
+  useManagementUpdates(context, groupId, () => {
+    detail.reload();
+    groups.reload();
+  });
 
   function run(path: string, body?: unknown): void {
     if (groupId === undefined) {
@@ -88,9 +82,8 @@ export function PlaybackPanel({
       return timelineId;
     }
     return (
-			timelines.state.value.timelines.find(
-				(timeline) => timeline.id === timelineId,
-			)?.name ?? timelineId
+      timelines.state.value.timelines.find((timeline) => timeline.id === timelineId)?.name ??
+      timelineId
     );
   }
 
@@ -130,10 +123,7 @@ export function PlaybackPanel({
               value === undefined ? (
                 <EmptyState title="No channel group selected" />
               ) : (
-								<div
-									className="signage-playback"
-									data-testid="signage-playback"
-								>
+                <div className="signage-playback" data-testid="signage-playback">
                   <div className="signage-playback__status">
                     {value.snapshot.activeTimelineId === null ? undefined : (
                       <Badge tone="success">
@@ -151,9 +141,7 @@ export function PlaybackPanel({
                     >
                       {value.snapshot.transport}
                     </Badge>
-										{value.snapshot.blackout ? (
-											<Badge tone="danger">Blackout</Badge>
-										) : undefined}
+                    {value.snapshot.blackout ? <Badge tone="danger">Blackout</Badge> : undefined}
                     {value.current?.stale === true ? (
                       <Badge tone="warning">Stale</Badge>
                     ) : undefined}
@@ -173,10 +161,7 @@ export function PlaybackPanel({
                   ) : (
                     <section className="signage-playback__now">
                       <h3>Now showing</h3>
-											<dl
-												className="signage-playback__current"
-												data-testid="signage-current"
-											>
+                      <dl className="signage-playback__current" data-testid="signage-current">
                         <dt>Provider</dt>
                         <dd>{value.current.providerId}</dd>
                         <dt>Item</dt>
@@ -192,12 +177,7 @@ export function PlaybackPanel({
                             : formatDuration(value.snapshot.remainingMs)}
                         </dd>
                         <dt>Started</dt>
-												<dd>
-													{formatInstant(
-														value.current.startedAtMs,
-														settings.timezone,
-													)}
-												</dd>
+                        <dd>{formatInstant(value.current.startedAtMs, settings.timezone)}</dd>
                       </dl>
                     </section>
                   )}
@@ -208,10 +188,7 @@ export function PlaybackPanel({
                       data-testid="signage-controls"
                       label="Playback controls"
                     >
-											<Button
-												disabled={command.pending}
-												onClick={() => run("previous")}
-											>
+                      <Button disabled={command.pending} onClick={() => run("previous")}>
                         Previous
                       </Button>
                       {value.snapshot.transport === "paused" ? (
@@ -223,27 +200,17 @@ export function PlaybackPanel({
                           Resume
                         </Button>
                       ) : (
-												<Button
-													disabled={command.pending}
-													onClick={() => run("pause")}
-												>
+                        <Button disabled={command.pending} onClick={() => run("pause")}>
                           Pause
                         </Button>
                       )}
-											<Button
-												disabled={command.pending}
-												onClick={() => run("next")}
-											>
+                      <Button disabled={command.pending} onClick={() => run("next")}>
                         Next
                       </Button>
                       <Button
                         disabled={command.pending}
-												onClick={() =>
-													run("blackout", { on: !value.snapshot.blackout })
-												}
-												variant={
-													value.snapshot.blackout ? "primary" : "secondary"
-												}
+                        onClick={() => run("blackout", { on: !value.snapshot.blackout })}
+                        variant={value.snapshot.blackout ? "primary" : "secondary"}
                       >
                         {value.snapshot.blackout ? "End blackout" : "Blackout"}
                       </Button>
@@ -255,10 +222,7 @@ export function PlaybackPanel({
                           Release hold
                         </Button>
                       )}
-											<Button
-												disabled={command.pending}
-												onClick={() => run("reload")}
-											>
+                      <Button disabled={command.pending} onClick={() => run("reload")}>
                         Reload content
                       </Button>
                     </ActionBar>
@@ -274,17 +238,12 @@ export function PlaybackPanel({
                               {(control) => (
                                 <Select
                                   {...control}
-																	onChange={(event) =>
-																		setActivateId(event.target.value)
-																	}
+                                  onChange={(event) => setActivateId(event.target.value)}
                                   value={activateId}
                                 >
                                   <option value="">Choose a timeline…</option>
                                   {loaded.timelines.map((timeline) => (
-																		<option
-																			key={timeline.id}
-																			value={timeline.id}
-																		>
+                                    <option key={timeline.id} value={timeline.id}>
                                       {timeline.name}
                                     </option>
                                   ))}
@@ -323,18 +282,11 @@ export function PlaybackPanel({
 
                   {value.history.length === 0 ? undefined : (
                     <div className="signage-playback__history">
-											<h4 className="signage-editor__subtitle">
-												Recently played
-											</h4>
+                      <h4 className="signage-editor__subtitle">Recently played</h4>
                       <ul className="ek-list">
                         {value.history.slice(0, 8).map((entry) => (
-													<li
-														className="ek-list__item signage-row"
-														key={entry.id}
-													>
-														<span className="signage-row__name">
-															{entry.itemId}
-														</span>
+                          <li className="ek-list__item signage-row" key={entry.id}>
+                            <span className="signage-row__name">{entry.itemId}</span>
                             <span className="signage-playback__history-meta">
                               {`${entry.providerId} · ${formatInstant(entry.startedAtMs, settings.timezone)}`}
                             </span>
@@ -355,3 +307,46 @@ export function PlaybackPanel({
     </div>
   );
 }
+
+/**
+ * Follows Signage's management realtime channel, which carries revisions only (ADR 0005), and asks
+ * for fresh detail when this group's playback actually changed — so "Now showing" follows the wall
+ * instead of freezing until an operator presses something. One subscription per mounted panel,
+ * closed when the panel goes away.
+ */
+function useManagementUpdates(
+  context: ModuleUiHostContext,
+  groupId: string | undefined,
+  onChange: () => void,
+): void {
+  const onChangeRef = useRef(onChange);
+  onChangeRef.current = onChange;
+  useEffect(() => {
+    if (groupId === undefined) {
+      return;
+    }
+    let seen: string | undefined;
+    const subscription = context.realtime.subscribe("management-state", {
+      onSnapshot: (payload) => observe(payload),
+      onUpdate: (payload) => observe(payload),
+    });
+    function observe(payload: unknown): void {
+      const groups = (payload as { groups?: unknown } | null)?.groups;
+      if (!Array.isArray(groups)) {
+        return;
+      }
+      const mine = groups.find((group: { groupId?: unknown }) => group?.groupId === groupId) as
+        | { revision?: unknown; selectionRevision?: unknown }
+        | undefined;
+      if (!mine) {
+        return;
+      }
+      const marker = `${String(mine.revision)}:${String(mine.selectionRevision)}`;
+      if (seen !== undefined && marker !== seen) {
+        onChangeRef.current();
+      }
+      seen = marker;
+    }
+    return () => subscription.close();
+  }, [context, groupId]);
+}

src/ui/panels/PreviewPanel.tsx

@@ -2,6 +2,7 @@ import type { ModuleUiHostContext } from "@ekklesia/module-ui-sdk";
 import { EmptyState, Panel } from "@ekklesia/ui";
 import { type ReactElement, useEffect, useRef } from "react";
 import { SignageSlate } from "../../browser/slate.js";
+import { createMemoryMediaCache, createMemoryStore } from "../../browser/storage.js";
 import { createDisplayController, type DisplayChannelStateView } from "../../display/controller.js";
 import type { SignageApi } from "../api.js";
 
@@ -36,7 +37,16 @@ export function PreviewPanel({
       return;
     }
     let stopped = false;
-    const controller = createDisplayController({ context, root, telemetry: false });
+    // The display's own rendering code, but nothing it keeps: a management browser is not a wall,
+    // so it persists no snapshot and caches no image bytes, and never restores one channel's last
+    // frame into another channel's preview.
+    const controller = createDisplayController({
+      context,
+      media: createMemoryMediaCache(),
+      root,
+      store: createMemoryStore(),
+      telemetry: false,
+    });
     let handle: ReturnType<typeof setTimeout> | undefined;
 
     async function pump(): Promise<void> {

src/ui/panels/ProvidersPanel.tsx

@@ -42,18 +42,15 @@ export function ProvidersPanel({
   const providers = useResource(
     () => api.get<{ providers: readonly ProviderHealth[] }>("providers"),
     [],
+    "providers",
   );
   const published = new Set(
-		context.contributions
-			.list(SLIDE_RENDERER_CAPABILITY)
-			.map((contribution) => contribution.id),
+    context.contributions.list(SLIDE_RENDERER_CAPABILITY).map((contribution) => contribution.id),
   );
 
   return (
     <Panel
-			actions={
-				<Badge tone="neutral">{`Contract ${settings.rendererInputVersion}`}</Badge>
-			}
+      actions={<Badge tone="neutral">{`Contract ${settings.rendererInputVersion}`}</Badge>}
       description="Running content sources available to timelines."
       title="Content providers"
     >
@@ -78,17 +75,12 @@ export function ProvidersPanel({
               </TableHead>
               <TableBody>
                 {value.providers.map((provider) => {
-									const rendererPublished = published.has(
-										provider.renderer.contributionId,
-									);
-									const isNative =
-										provider.renderer.contributionId === "signage.native-image";
+                  const rendererPublished = published.has(provider.renderer.contributionId);
+                  const isNative = provider.renderer.contributionId === "signage.native-image";
                   return (
                     <TableRow key={provider.providerId}>
                       <TableCell>
-												<span className="signage-provider__id">
-													{provider.providerId}
-												</span>
+                        <span className="signage-provider__id">{provider.providerId}</span>
                         <span className="signage-provider__version">{`v${provider.providerVersion}`}</span>
                       </TableCell>
                       <TableCell>{provider.contractVersion}</TableCell>
@@ -96,9 +88,7 @@ export function ProvidersPanel({
                         {isNative ? (
                           <Badge tone="info">Built in</Badge>
                         ) : rendererPublished ? (
-													<Badge tone="success">
-														{provider.renderer.contributionId}
-													</Badge>
+                          <Badge tone="success">{provider.renderer.contributionId}</Badge>
                         ) : (
                           <Badge tone="warning">Renderer not published</Badge>
                         )}
@@ -113,10 +103,7 @@ export function ProvidersPanel({
                         )}
                       </TableCell>
                       <TableCell>
-												{formatInstant(
-													provider.lastSuccessAt,
-													settings.timezone,
-												)}
+                        {formatInstant(provider.lastSuccessAt, settings.timezone)}
                       </TableCell>
                     </TableRow>
                   );

src/ui/panels/TimelinesPanel.tsx

@@ -26,6 +26,7 @@ import type {
   TimelineSummary,
 } from "../types.js";
 import {
+  ConfirmButton,
   FailureNote,
   formatDuration,
   formatInstant,
@@ -60,10 +61,12 @@ export function TimelinesPanel({
   const timelines = useResource(
     () => api.get<{ timelines: readonly TimelineSummary[] }>("timelines"),
     [],
+    "timelines",
   );
   const providers = useResource(
     () => api.get<{ providers: readonly ProviderHealth[] }>("providers"),
     [],
+    "providers",
   );
   const [selectedId, setSelectedId] = useState<string | undefined>(undefined);
   const [newName, setNewName] = useState("");
@@ -92,9 +95,7 @@ export function TimelinesPanel({
               <Button
                 disabled={create.pending || newName.trim().length === 0}
                 onClick={() =>
-									create.run(() =>
-										api.send("POST", "timelines", { name: newName.trim() }),
-									)
+                  create.run(() => api.send("POST", "timelines", { name: newName.trim() }))
                 }
                 variant="primary"
               >
@@ -126,10 +127,7 @@ export function TimelinesPanel({
                 </TableHead>
                 <TableBody>
                   {value.timelines.map((timeline) => (
-										<TableRow
-											key={timeline.id}
-											selected={timeline.id === selectedId}
-										>
+                    <TableRow key={timeline.id} selected={timeline.id === selectedId}>
                       <TableCell>
                         <div className="signage-timeline-name">
                           <Button
@@ -141,16 +139,13 @@ export function TimelinesPanel({
                           </Button>
                           {timeline.id === activeTimelineId ? (
                             <Badge tone="success">
-															{activeGroupName
-																? `Active in ${activeGroupName}`
-																: "Active"}
+                              {activeGroupName ? `Active in ${activeGroupName}` : "Active"}
                             </Badge>
                           ) : undefined}
                         </div>
                       </TableCell>
                       <TableCell>
-												{timeline.eligibleFrom === null &&
-												timeline.eligibleUntil === null
+                        {timeline.eligibleFrom === null && timeline.eligibleUntil === null
                           ? "Always"
                           : `${formatInstant(timeline.eligibleFrom, settings.timezone)} → ${formatInstant(timeline.eligibleUntil, settings.timezone)}`}
                       </TableCell>
@@ -158,18 +153,11 @@ export function TimelinesPanel({
                       <TableCell>
                         {onActivate === undefined ? undefined : (
                           <Button
-														disabled={
-															activation.pending ||
-															timeline.id === activeTimelineId
-														}
-														onClick={() =>
-															activation.run(() => onActivate(timeline.id))
-														}
+                            disabled={activation.pending || timeline.id === activeTimelineId}
+                            onClick={() => activation.run(() => onActivate(timeline.id))}
                             variant="primary"
                           >
-														{timeline.id === activeTimelineId
-															? "Active"
-															: "Activate"}
+                            {timeline.id === activeTimelineId ? "Active" : "Activate"}
                           </Button>
                         )}
                       </TableCell>
@@ -191,11 +179,7 @@ export function TimelinesPanel({
           key={selectedId}
           onChanged={timelines.reload}
           onClose={() => setSelectedId(undefined)}
-					providers={
-						providers.state.status === "ready"
-							? providers.state.value.providers
-							: []
-					}
+          providers={providers.state.status === "ready" ? providers.state.value.providers : []}
           settings={settings}
           timelineId={selectedId}
         />
@@ -224,19 +208,19 @@ function TimelineEditor({
   const detail = useResource(
     () => api.get<TimelineDetail>(`timelines/${timelineId}`),
     [timelineId],
+    `timelines/${timelineId}`,
   );
   const images = useResource(
     () => api.get<{ images: readonly ImageRecord[] }>("images"),
     [],
+    "images",
   );
   const edit = useAction(() => {
     detail.reload();
     onChanged();
   });
   const [providerId, setProviderId] = useState("");
-	const [sources, setSources] = useState<readonly ProviderSourceDescriptor[]>(
-		[],
-	);
+  const [sources, setSources] = useState<readonly ProviderSourceDescriptor[]>([]);
   const [items, setItems] = useState<readonly ProviderItemDescriptor[]>([]);
 
   function loadProvider(nextProviderId: string): void {
@@ -273,10 +257,7 @@ function TimelineEditor({
             <h3 className="signage-editor__title">{value.timeline.name}</h3>
 
             {canManage ? (
-							<div
-								className="signage-editor__add"
-								data-testid="signage-add-source"
-							>
+              <div className="signage-editor__add" data-testid="signage-add-source">
                 <Field
                   hint="A provider's own source. Repeat its slot to give it more turns in one rotation."
                   label="Content provider"
@@ -289,10 +270,7 @@ function TimelineEditor({
                     >
                       <option value="">Choose a provider…</option>
                       {providers.map((provider) => (
-												<option
-													key={provider.providerId}
-													value={provider.providerId}
-												>
+                        <option key={provider.providerId} value={provider.providerId}>
                           {provider.providerId}
                         </option>
                       ))}
@@ -348,32 +326,24 @@ function TimelineEditor({
                           disabled={edit.pending}
                           onClick={() =>
                             edit.run(() =>
-															api.send(
-																"POST",
-																`timelines/${timelineId}/slots`,
-																{
+                              api.send("POST", `timelines/${timelineId}/slots`, {
                                 sourceId: source.id,
-																},
-															),
+                              }),
                             )
                           }
                         >
                           Add slot
                         </Button>
-												<Button
+                        <ConfirmButton
+                          confirmLabel="Remove this source"
                           disabled={edit.pending}
-													onClick={() =>
+                          label="Remove"
+                          onConfirm={() =>
                             edit.run(() =>
-															api.send(
-																"DELETE",
-																`timelines/${timelineId}/sources/${source.id}`,
-															),
+                              api.send("DELETE", `timelines/${timelineId}/sources/${source.id}`),
                             )
                           }
-													variant="danger"
-												>
-													Remove
-												</Button>
+                        />
                       </>
                     ) : undefined}
                   </div>
@@ -403,8 +373,7 @@ function TimelineEditor({
                       (candidate) => candidate.id === slot.sourceId,
                     );
                     const image =
-											slot.providerId === NATIVE_PROVIDER_ID &&
-											images.state.status === "ready"
+                      slot.providerId === NATIVE_PROVIDER_ID && images.state.status === "ready"
                         ? images.state.value.images.find(
                             (candidate) => candidate.id === slot.itemId,
                           )
@@ -415,8 +384,7 @@ function TimelineEditor({
                         <TableCell>
                           {slot.kind === "provider-source"
                             ? (source?.label ?? "Removed source")
-														: (image?.displayName ??
-															`${slot.providerId} · ${slot.itemId}`)}
+                            : (image?.displayName ?? `${slot.providerId} · ${slot.itemId}`)}
                         </TableCell>
                         <TableCell>
                           {slot.durationOverrideMs === null
@@ -430,13 +398,9 @@ function TimelineEditor({
                             label={slot.enabled ? "On" : "Off"}
                             onChange={(event) =>
                               edit.run(() =>
-																api.send(
-																	"PATCH",
-																	`timelines/${timelineId}/slots/${slot.id}`,
-																	{
+                                api.send("PATCH", `timelines/${timelineId}/slots/${slot.id}`, {
                                   enabled: event.target.checked,
-																	},
-																),
+                                }),
                               )
                             }
                           />
@@ -448,63 +412,44 @@ function TimelineEditor({
                                 disabled={index === 0 || edit.pending}
                                 onClick={() =>
                                   edit.run(() =>
-																		api.send(
-																			"PUT",
-																			`timelines/${timelineId}/slot-order`,
-																			{
+                                    api.send("PUT", `timelines/${timelineId}/slot-order`, {
                                       slotIds: swap(
-																					value.slots.map(
-																						(candidate) => candidate.id,
-																					),
+                                        value.slots.map((candidate) => candidate.id),
                                         index,
                                         index - 1,
                                       ),
-																			},
-																		),
+                                    }),
                                   )
                                 }
                               >
                                 Up
                               </Button>
                               <Button
-																disabled={
-																	index === value.slots.length - 1 ||
-																	edit.pending
-																}
+                                disabled={index === value.slots.length - 1 || edit.pending}
                                 onClick={() =>
                                   edit.run(() =>
-																		api.send(
-																			"PUT",
-																			`timelines/${timelineId}/slot-order`,
-																			{
+                                    api.send("PUT", `timelines/${timelineId}/slot-order`, {
                                       slotIds: swap(
-																					value.slots.map(
-																						(candidate) => candidate.id,
-																					),
+                                        value.slots.map((candidate) => candidate.id),
                                         index,
                                         index + 1,
                                       ),
-																			},
-																		),
+                                    }),
                                   )
                                 }
                               >
                                 Down
                               </Button>
-															<Button
+                              <ConfirmButton
+                                confirmLabel="Remove this slot"
                                 disabled={edit.pending}
-																onClick={() =>
+                                label="Remove"
+                                onConfirm={() =>
                                   edit.run(() =>
-																		api.send(
-																			"DELETE",
-																			`timelines/${timelineId}/slots/${slot.id}`,
-																		),
+                                    api.send("DELETE", `timelines/${timelineId}/slots/${slot.id}`),
                                   )
                                 }
-																variant="danger"
-															>
-																Remove
-															</Button>
+                              />
                             </div>
                           ) : undefined}
                         </TableCell>
@@ -529,18 +474,18 @@ function TimelineEditor({
                 >
                   Duplicate
                 </Button>
-								<Button
+                <ConfirmButton
+                  confirmLabel={`Delete ${value.timeline.name}`}
                   disabled={edit.pending}
-									onClick={() =>
+                  label="Delete timeline"
+                  onConfirm={() =>
                     edit.run(async () => {
                       await api.send("DELETE", `timelines/${timelineId}`);
                       onClose();
                     })
                   }
-									variant="danger"
-								>
-									Delete timeline
-								</Button>
+                  testId="signage-timeline-delete"
+                />
               </div>
             ) : undefined}
           </div>

src/ui/panels/shared.tsx

@@ -1,5 +1,5 @@
-import { Badge, ErrorState, LoadingState } from "@ekklesia/ui";
-import type { ReactElement, ReactNode } from "react";
+import { Badge, Button, ErrorState, LoadingState } from "@ekklesia/ui";
+import { type ReactElement, type ReactNode, useEffect, useState } from "react";
 import type { SignageApiFailure } from "../api.js";
 import type { Loadable } from "../hooks.js";
 
@@ -89,3 +89,80 @@ export function formatSince(atMs: number | null, nowMs: number): string {
 export function OnlineBadge({ online }: { readonly online: boolean }): ReactElement {
   return <Badge tone={online ? "success" : "danger"}>{online ? "Online" : "Offline"}</Badge>;
 }
+
+/** How long an armed destructive button waits for its second press before standing down. */
+export const CONFIRM_RESET_MS = 6000;
+
+/**
+ * A moderate destructive action, confirmed in place (DESIGN §21.3) — never with a browser dialog.
+ *
+ * The first press arms it: the button says plainly what will happen and a Cancel appears beside it.
+ * A second, deliberate press performs the action. Walking away, pressing Cancel, or Escape disarms
+ * it, so an armed button can never be left waiting for an accidental click.
+ */
+export function ConfirmButton({
+  label,
+  confirmLabel,
+  disabled,
+  onConfirm,
+  testId,
+}: {
+  readonly label: string;
+  /** What the second press does, in words: "Delete this image", not "Are you sure?". */
+  readonly confirmLabel: string;
+  readonly disabled?: boolean;
+  readonly onConfirm: () => void;
+  readonly testId?: string;
+}): ReactElement {
+  const [armed, setArmed] = useState(false);
+  useEffect(() => {
+    if (!armed) {
+      return;
+    }
+    const timer = setTimeout(() => setArmed(false), CONFIRM_RESET_MS);
+    return () => clearTimeout(timer);
+  }, [armed]);
+
+  if (!armed) {
+    return (
+      <Button
+        data-testid={testId}
+        disabled={disabled}
+        onClick={() => setArmed(true)}
+        variant="danger"
+      >
+        {label}
+      </Button>
+    );
+  }
+  return (
+    <fieldset
+      className="signage-confirm-inline"
+      onKeyDown={(event) => {
+        if (event.key === "Escape") {
+          setArmed(false);
+        }
+      }}
+    >
+      <Button
+        autoFocus
+        data-testid={testId === undefined ? undefined : `${testId}-confirm`}
+        disabled={disabled}
+        onClick={() => {
+          setArmed(false);
+          onConfirm();
+        }}
+        variant="danger"
+      >
+        {confirmLabel}
+      </Button>
+      <Button
+        data-testid={testId === undefined ? undefined : `${testId}-cancel`}
+        onClick={() => setArmed(false)}
+        variant="quiet"
+      >
+        Cancel
+      </Button>
+    </fieldset>
+  );
+}

src/ui/styles.css

@@ -176,10 +176,7 @@
 .signage-image-grid {
   display: grid;
   gap: var(--signage-gap);
-	grid-template-columns: repeat(
-			auto-fill,
-			minmax(var(--signage-thumbnail-width), 1fr)
-		);
+  grid-template-columns: repeat(auto-fill, minmax(var(--signage-thumbnail-width), 1fr));
   list-style: none;
   margin: 0;
   padding: 0;
@@ -507,14 +504,30 @@
   padding: var(--ekklesia-spacing-sm);
 }
 
+.signage-advanced > summary {
+  color: var(--ekklesia-text-secondary);
+  cursor: pointer;
+  font-size: var(--ekklesia-typography-size-sm);
+}
+
+.signage-advanced[open] > summary {
+  margin-block-end: var(--signage-gap-tight);
+}
+
+.signage-confirm-inline {
+  align-items: center;
+  display: inline-flex;
+  flex-wrap: wrap;
+  gap: var(--signage-gap-tight);
+}
+
 .signage-confirm p {
   flex: 1 1 30rem;
   margin: 0;
 }
 
 .signage-audiences {
-	border-block-start: var(--ekklesia-border-width) solid
-		var(--ekklesia-border-divider);
+  border-block-start: var(--ekklesia-border-width) solid var(--ekklesia-border-divider);
   display: grid;
   gap: var(--signage-gap);
   padding-block-start: var(--signage-gap);
@@ -545,8 +558,7 @@
 .signage-channel {
   background: var(--ekklesia-background-surface);
   border: var(--ekklesia-border-width) solid var(--ekklesia-border-divider);
-	border-inline-start: var(--ekklesia-spacing-2xs) solid
-		var(--ekklesia-accent-base);
+  border-inline-start: var(--ekklesia-spacing-2xs) solid var(--ekklesia-accent-base);
   border-radius: var(--ekklesia-radius-md);
   display: grid;
   gap: var(--signage-gap-tight);
@@ -584,8 +596,7 @@
 }
 
 .signage-channel__displays {
-	border-block-start: var(--ekklesia-border-width) solid
-		var(--ekklesia-border-divider);
+  border-block-start: var(--ekklesia-border-width) solid var(--ekklesia-border-divider);
   display: grid;
   gap: var(--signage-gap-tight);
   padding-block-start: var(--signage-gap-tight);
@@ -603,10 +614,7 @@
   border-radius: var(--ekklesia-radius-md);
   display: grid;
   gap: var(--signage-gap-tight);
-	grid-template-columns: minmax(14rem, 1.2fr) minmax(14rem, 1fr) minmax(
-			14rem,
-			1.2fr
-		);
+  grid-template-columns: minmax(14rem, 1.2fr) minmax(14rem, 1fr) minmax(14rem, 1.2fr);
   padding: var(--ekklesia-spacing-sm);
 }
 

tests/browser/display-contract.test.ts

@@ -200,7 +200,8 @@ describe("display ↔ server contract", () => {
 
     const sent = calls.map((call) => `${call.method} ${call.path}`);
     expect(sent).toContain("POST /viewers/session");
-    expect(sent).toContain("GET /channels/:channelId/display-state");
+    // By viewer, so the server — not the display's memory of its registration — decides the channel.
+    expect(sent).toContain("GET /viewers/:viewerId/display-state");
     expect(sent).toContain("POST /viewers/:viewerId/heartbeat");
     // Not one refusal, of any kind, for anything the display built itself.
     expect(calls.filter((call) => call.status >= 400)).toEqual([]);
@@ -220,4 +221,48 @@ describe("display ↔ server contract", () => {
     expect(viewer?.reportedProviderId).toBe(SIGNAGE_NATIVE_PROVIDER_ID);
     expect(viewer?.reportedContributionId).toBeNull();
   });
+
+  it("a display moved to another channel group is served that group's state on its next fetch", async () => {
+    const display = controller();
+    await display.start();
+    await settle();
+    const viewerId = display.diagnostics().viewerId;
+    const firstChannel = display.diagnostics().channelId;
+    expect(viewerId).toBeDefined();
+
+    // An administrator creates a second group and moves this screen to it while it is running.
+    const groupId = newId();
+    const channelId = newId();
+    await store.createChannelGroup({ channelId, channelName: "Default", groupId, name: "Nursery" });
+    await store.updateViewer(viewerId as string, { channelId });
+
+    const response = await host.context.api.request(`viewers/${viewerId}/display-state`);
+    const state = (await response.json()) as { channel: { id: string; groupId: string } };
+    expect(state.channel).toMatchObject({ groupId, id: channelId });
+    expect(channelId).not.toBe(firstChannel);
+
+    // And the heartbeat names the new assignment, which is how a display with a long slot hears.
+    const beat = await host.context.api.request(`viewers/${viewerId}/heartbeat`, {
+      body: JSON.stringify({}),
+      headers: { "content-type": "application/json" },
+      method: "POST",
+    });
+    expect(((await beat.json()) as { channelId?: string }).channelId).toBe(channelId);
+    await display.stop();
+  });
+
+  it("a display whose channel was deleted falls back to the default channel, not to nothing", async () => {
+    const display = controller();
+    await display.start();
+    await settle();
+    const viewerId = display.diagnostics().viewerId as string;
+    await store.updateViewer(viewerId, { channelId: null });
+
+    const response = await host.context.api.request(`viewers/${viewerId}/display-state`);
+    expect(response.status).toBe(200);
+    const [group] = await store.listChannelGroups();
+    const fallback = group?.channels.find((channel) => channel.isDefault);
+    expect(((await response.json()) as { channel: { id: string } }).channel.id).toBe(fallback?.id);
+    await display.stop();
+  });
 });

tests/browser/display-recovery.test.ts

@@ -145,7 +145,7 @@ describe("a display recovers from every failed request without a reload", () =>
         },
         {
           method: "GET",
-          path: "channels/chan-1/display-state",
+          path: /^(viewers\/[^/]+|channels\/chan-1)\/display-state$/u,
           respond: () => {
             server.stateRequests += 1;
             if (server.stateFailing) {

tests/browser/display.test.ts

@@ -174,7 +174,7 @@ describe("display controller", () => {
         },
         {
           method: "GET",
-          path: "channels/chan-1/display-state",
+          path: /^(viewers\/[^/]+|channels\/chan-1)\/display-state$/u,
           respond: () => jsonResponse(state()),
         },
         { method: "POST", path: /^viewers\/.*\/heartbeat$/u, respond: () => jsonResponse({}) },
@@ -205,7 +205,7 @@ describe("display controller", () => {
         { method: "POST", path: "viewers/session", respond: () => jsonResponse(SESSION) },
         {
           method: "GET",
-          path: "channels/chan-1/display-state",
+          path: /^(viewers\/[^/]+|channels\/chan-1)\/display-state$/u,
           respond: () => jsonResponse(state()),
         },
         { method: "POST", path: /^viewers\/.*\/heartbeat$/u, respond: () => jsonResponse({}) },
@@ -376,6 +376,28 @@ describe("display controller", () => {
     await controller.stop();
   });
 
+  it("restores a blackout before the server answers, so a reload never flashes content", async () => {
+    const store = createMemoryStore();
+    const media = createMemoryMediaCache();
+    const online = createFakeHost({ permissions: [], routes: [] });
+    const before = build({ host: online, media, store, telemetry: false });
+    await before.start();
+    await before.apply(state({ playback: { blackout: true } as never }));
+    await settle();
+    await before.stop();
+
+    // A kiosk reloads mid-blackout and its first request has not been answered yet.
+    root.dataset.blackout = "false";
+    const pending = createFakeHost({ permissions: ["signage.display.view"], routes: [] });
+    Object.assign(pending.context.api, { request: () => new Promise<Response>(() => undefined) });
+    const after = build({ host: pending, media, store });
+    void after.start();
+    await settle();
+
+    expect(root.dataset.blackout).toBe("true");
+    await after.stop();
+  });
+
   it("reports a bounded, sanitized heartbeat and nothing else", async () => {
     const beats: unknown[] = [];
     const host = createFakeHost({
@@ -384,7 +406,7 @@ describe("display controller", () => {
         { method: "POST", path: "viewers/session", respond: () => jsonResponse(SESSION) },
         {
           method: "GET",
-          path: "channels/chan-1/display-state",
+          path: /^(viewers\/[^/]+|channels\/chan-1)\/display-state$/u,
           respond: () => jsonResponse(state()),
         },
         {
@@ -428,7 +450,7 @@ describe("display controller", () => {
         { method: "POST", path: "viewers/session", respond: () => jsonResponse(SESSION) },
         {
           method: "GET",
-          path: "channels/chan-1/display-state",
+          path: /^(viewers\/[^/]+|channels\/chan-1)\/display-state$/u,
           respond: () => jsonResponse(state()),
         },
         { method: "POST", path: /^viewers\/.*\/heartbeat$/u, respond: () => jsonResponse({}) },
@@ -471,4 +493,146 @@ describe("display controller", () => {
     expect(controller.diagnostics().renderedSelectionId).toBe("sel-1");
     await controller.stop();
   });
+
+  it("follows the server when an administrator moves it to another channel", async () => {
+    const moved = { groupId: "group-2", id: "chan-2", key: "online" };
+    let stateFetches = 0;
+    let realtimeHandlers: { onUpdate?: (state: unknown) => void } | undefined;
+    const host = createFakeHost({
+      permissions: ["signage.display.view"],
+      routes: [
+        { method: "POST", path: "viewers/session", respond: () => jsonResponse(SESSION) },
+        {
+          method: "GET",
+          path: /^viewers\/[^/]+\/display-state$/u,
+          respond: () => {
+            stateFetches += 1;
+            // Registered on chan-1; moved by an administrator right after its first fetch.
+            return jsonResponse(state(stateFetches === 1 ? {} : { channel: moved }));
+          },
+        },
+        {
+          method: "POST",
+          path: /^viewers\/.*\/heartbeat$/u,
+          respond: () => jsonResponse({ acknowledged: true, channelId: moved.id, recorded: true }),
+        },
+      ],
+    });
+    Object.assign(host.context.realtime, {
+      subscribe: (_channel: string, handlers: { onUpdate?: (state: unknown) => void }) => {
+        realtimeHandlers = handlers;
+        return { close: () => undefined };
+      },
+    });
+    const controller = build({ host });
+    await controller.start();
+    await settle();
+
+    // The heartbeat named a different channel, so the display refetched and adopted it.
+    expect(stateFetches).toBe(2);
+    expect(controller.diagnostics().channelId).toBe("chan-2");
+
+    // A change in the old group no longer concerns it; a change in the new one does.
+    realtimeHandlers?.onUpdate?.({
+      groups: [{ groupId: "group-1", revision: 99, selectionRevision: 1 }],
+    });
+    await settle();
+    expect(stateFetches).toBe(2);
+    realtimeHandlers?.onUpdate?.({
+      groups: [{ groupId: "group-2", revision: 99, selectionRevision: 1 }],
+    });
+    await settle();
+    expect(stateFetches).toBe(3);
+    await controller.stop();
+  });
+
+  it("registers again, exactly once, when it was removed from the roster", async () => {
+    let sessions = 0;
+    let subscriptions = 0;
+    let closes = 0;
+    let removed = false;
+    const host = createFakeHost({
+      permissions: ["signage.display.view"],
+      routes: [
+        {
+          method: "POST",
+          path: "viewers/session",
+          respond: () => {
+            sessions += 1;
+            removed = false;
+            return jsonResponse(SESSION);
+          },
+        },
+        {
+          method: "GET",
+          path: /^viewers\/[^/]+\/display-state$/u,
+          respond: () =>
+            removed ? jsonResponse({ code: "SIGNAGE_NOT_FOUND" }, 404) : jsonResponse(state()),
+        },
+        {
+          method: "POST",
+          path: /^viewers\/.*\/heartbeat$/u,
+          respond: () =>
+            removed
+              ? jsonResponse({ code: "SIGNAGE_NOT_FOUND" }, 404)
+              : jsonResponse({ acknowledged: true }),
+        },
+      ],
+    });
+    let onUpdate: ((state: unknown) => void) | undefined;
+    Object.assign(host.context.realtime, {
+      subscribe: (_channel: string, handlers: { onUpdate?: (state: unknown) => void }) => {
+        subscriptions += 1;
+        onUpdate = handlers.onUpdate;
+        return { close: () => (closes += 1) };
+      },
+    });
+    const controller = build({ host });
+    await controller.start();
+    await settle();
+    expect(sessions).toBe(1);
+
+    // Removed from the roster; a realtime nudge and a heartbeat both discover it at once.
+    removed = true;
+    onUpdate?.({ groups: [{ groupId: "group-1", revision: 50, selectionRevision: 1 }] });
+    onUpdate?.({ groups: [{ groupId: "group-1", revision: 51, selectionRevision: 1 }] });
+    await settle();
+
+    expect(sessions).toBe(2);
+    // One live subscription: the old one closed, exactly one new one opened.
+    expect(subscriptions - closes).toBe(1);
+    expect(controller.diagnostics().renderedSelectionId).toBe("sel-1");
+    await controller.stop();
+  });
+
+  it("treats a 404 that is not Signage's own as an ordinary failure, never a re-registration loop", async () => {
+    let sessions = 0;
+    const host = createFakeHost({
+      permissions: ["signage.display.view"],
+      routes: [
+        {
+          method: "POST",
+          path: "viewers/session",
+          respond: () => {
+            sessions += 1;
+            return jsonResponse(SESSION);
+          },
+        },
+        {
+          method: "GET",
+          path: /^viewers\/[^/]+\/display-state$/u,
+          // A proxy, or a server without this route — not "this viewer is gone".
+          respond: () => jsonResponse({ code: "NOT_FOUND" }, 404),
+        },
+        { method: "POST", path: /^viewers\/.*\/heartbeat$/u, respond: () => jsonResponse({}) },
+      ],
+    });
+    const controller = build({ host });
+    await controller.start();
+    await settle();
+    await settle();
+
+    expect(sessions).toBe(1);
+    await controller.stop();
+  });
 });

tests/browser/management-ui.test.tsx

@@ -3,12 +3,7 @@ import { act } from "react";
 import { createRoot, type Root } from "react-dom/client";
 import { afterEach, beforeEach, describe, expect, it } from "vitest";
 import { SignageDashboard } from "../../src/ui/SignageDashboard.js";
-import {
-	createFakeHost,
-	errorResponse,
-	FAKE_SETTINGS,
-	jsonResponse,
-} from "./support/fake-host.js";
+import { createFakeHost, errorResponse, FAKE_SETTINGS, jsonResponse } from "./support/fake-host.js";
 
 /**
  * The management UI's behaviour, mounted as React rather than inspected as source.
@@ -19,18 +14,14 @@ import {
  */
 
 // React needs this to run effects the way a browser does.
-(
-	globalThis as { IS_REACT_ACT_ENVIRONMENT?: boolean }
-).IS_REACT_ACT_ENVIRONMENT = true;
+(globalThis as { IS_REACT_ACT_ENVIRONMENT?: boolean }).IS_REACT_ACT_ENVIRONMENT = true;
 
 let container: HTMLElement;
 let root: Root;
 const DISPLAY_SETUP_URL = "https://api.example.test/display/signage";
 const copiedText: string[] = [];
 
-function dashboard(
-	context: Parameters<typeof SignageDashboard>[0]["context"],
-): React.ReactElement {
+function dashboard(context: Parameters<typeof SignageDashboard>[0]["context"]): React.ReactElement {
   return (
     <SignageDashboard
       context={context}
@@ -93,9 +84,7 @@ function buttonNamed(label: string): HTMLButtonElement | undefined {
 }
 
 const GROUP = {
-	channels: [
-		{ id: "chan-1", isDefault: true, key: "default", name: "Default" },
-	],
+  channels: [{ id: "chan-1", isDefault: true, key: "default", name: "Default" }],
   id: "group-1",
   name: "Main",
   playback: {
@@ -208,12 +197,10 @@ describe("Signage dashboard", () => {
 
     await render(dashboard(host.context));
 
-		expect(
-			container.querySelector("[data-testid='signage-current']")?.textContent,
-		).toContain("welcome");
-		expect(
-			container.querySelector("[data-testid='signage-remaining']")?.textContent,
-		).toBe("4s");
+    expect(container.querySelector("[data-testid='signage-current']")?.textContent).toContain(
+      "welcome",
+    );
+    expect(container.querySelector("[data-testid='signage-remaining']")?.textContent).toBe("4s");
 
     await click(buttonNamed("Pause"));
     await click(buttonNamed("Next"));
@@ -256,12 +243,8 @@ describe("Signage dashboard", () => {
     await render(dashboard(host.context));
 
     // The current slide is still legible; the buttons that would be refused are simply not offered.
-		expect(
-			container.querySelector("[data-testid='signage-current']"),
-		).not.toBeNull();
-		expect(
-			container.querySelector("[data-testid='signage-controls']"),
-		).toBeNull();
+    expect(container.querySelector("[data-testid='signage-current']")).not.toBeNull();
+    expect(container.querySelector("[data-testid='signage-controls']")).toBeNull();
   });
 
   it("shows which timeline remains active after the dashboard data is reloaded", async () => {
@@ -349,11 +332,7 @@ describe("Signage dashboard", () => {
           method: "POST",
           path: "playback/group-1/activate",
           respond: () =>
-						errorResponse(
-							"SIGNAGE_CONFLICT",
-							"The request conflicts with the current state.",
-							409,
-						),
+            errorResponse("SIGNAGE_CONFLICT", "The request conflicts with the current state.", 409),
         },
       ],
     });
@@ -404,12 +383,7 @@ describe("Signage dashboard", () => {
         {
           method: "POST",
           path: "timelines",
-					respond: () =>
-						errorResponse(
-							"SIGNAGE_INVALID_REQUEST",
-							"The request is not valid.",
-							400,
-						),
+          respond: () => errorResponse("SIGNAGE_INVALID_REQUEST", "The request is not valid.", 400),
         },
       ],
     });
@@ -421,9 +395,7 @@ describe("Signage dashboard", () => {
       ),
     );
 
-		const input = container.querySelector(
-			"input[type='text']",
-		) as HTMLInputElement;
+    const input = container.querySelector("input[type='text']") as HTMLInputElement;
     await type(input, "Sunday morning");
     await click(buttonNamed("Create"));
 
@@ -504,9 +476,7 @@ describe("Signage dashboard", () => {
     );
     await click(buttonNamed("Sunday morning"));
 
-		expect(
-			container.querySelector("[data-testid='signage-timeline-editor']"),
-		).not.toBeNull();
+    expect(container.querySelector("[data-testid='signage-timeline-editor']")).not.toBeNull();
     expect(container.textContent).toContain("This timeline has no slots");
   });
 
@@ -615,9 +585,7 @@ describe("Signage dashboard", () => {
     );
 
     expect(container.textContent).toContain("No content providers registered");
-		expect(container.textContent).toContain(
-			"Signage works on its own with native images",
-		);
+    expect(container.textContent).toContain("Signage works on its own with native images");
   });
 
   it("shows the display roster with online state and offline readiness", async () => {
@@ -677,19 +645,13 @@ describe("Signage dashboard", () => {
 
     await render(dashboard(host.context));
     await click(
-			[...container.querySelectorAll("[role='tab']")].find(
-				(tab) => tab.textContent === "Displays",
-			),
+      [...container.querySelectorAll("[role='tab']")].find((tab) => tab.textContent === "Displays"),
     );
 
     expect(container.textContent).toContain("Online");
     expect(container.textContent).toContain("12 cached");
-		const display = container.querySelector(
-			"[data-testid='signage-display-viewer-1']",
-		);
-		expect(display?.closest(".signage-channel")?.textContent).toContain(
-			"Default",
-		);
+    const display = container.querySelector("[data-testid='signage-display-viewer-1']");
+    expect(display?.closest(".signage-channel")?.textContent).toContain("Default");
     // A sanitized code, never a stack or a message a browser happened to have.
     expect(container.textContent).toContain("SLIDE_DECODE_FAILED");
   });
@@ -697,9 +659,7 @@ describe("Signage dashboard", () => {
   it("explains display registration and deletes a channel group only after confirmation", async () => {
     const secondGroup = {
       ...GROUP,
-			channels: [
-				{ id: "chan-2", isDefault: true, key: "default", name: "Default" },
-			],
+      channels: [{ id: "chan-2", isDefault: true, key: "default", name: "Default" }],
       id: "group-2",
       name: "Foyer",
       playback: { ...GROUP.playback, groupId: "group-2" },
@@ -754,21 +714,21 @@ describe("Signage dashboard", () => {
     );
 
     const setupLink = [...container.querySelectorAll("a")].find(
-			(candidate) => candidate.textContent?.trim() === "Open display setup",
+      (candidate) => candidate.textContent?.trim() === "Preview here",
     );
     expect(setupLink?.href).toBe(DISPLAY_SETUP_URL);
     expect(setupLink?.target).toBe("_blank");
     expect(setupLink?.rel).toContain("noopener");
-		await click(buttonNamed("Copy URL"));
+    await click(buttonNamed("Copy setup address"));
     expect(copiedText).toEqual([DISPLAY_SETUP_URL]);
-		expect(container.textContent).toContain("Display setup URL copied.");
+    expect(container.textContent).toContain("Display setup address copied.");
     expect(container.textContent).toContain("Channel groups and displays");
-		expect(container.textContent).toContain("Audience channels");
-		expect(container.textContent).toContain("Channel name");
-		expect(container.textContent).toContain("Audience key");
-		expect(container.textContent).toContain(
-			"Advanced: lowercase ID sent to content providers",
-		);
+    // Plain language for the audience concept, and no internal key on the page by default.
+    expect(container.textContent).toContain("Audiences");
+    expect(container.textContent).toContain("Images look the same for every audience.");
+    expect(container.textContent).toContain("Audience name");
+    expect(container.textContent).not.toContain("Audience key");
+    expect(container.querySelector("details.signage-advanced")?.hasAttribute("open")).toBe(false);
     await click(buttonNamed("Delete group"));
     expect(deleted).toEqual([]);
     expect(container.textContent).toContain("Displays assigned here will move");
@@ -825,9 +785,7 @@ describe("Signage dashboard", () => {
 
     await render(dashboard(host.context));
     await click(
-			[...container.querySelectorAll("[role='tab']")].find(
-				(tab) => tab.textContent === "Images",
-			),
+      [...container.querySelectorAll("[role='tab']")].find((tab) => tab.textContent === "Images"),
     );
 
     const input = container.querySelector(
@@ -857,9 +815,7 @@ describe("Signage dashboard", () => {
     const uploads = container.querySelector("[data-testid='signage-uploads']");
     expect(uploads?.textContent).toContain("done");
     expect(uploads?.textContent).toContain("failed");
-		expect(uploads?.textContent).toContain(
-			"The uploaded file is not a decodable image.",
-		);
+    expect(uploads?.textContent).toContain("The uploaded file is not a decodable image.");
   });
 
   it("stays on screen when one panel's data cannot be loaded", async () => {
@@ -885,11 +841,7 @@ describe("Signage dashboard", () => {
           method: "GET",
           path: "playback/group-1",
           respond: () =>
-						errorResponse(
-							"SIGNAGE_OPERATION_FAILED",
-							"The operation could not be completed.",
-							500,
-						),
+            errorResponse("SIGNAGE_OPERATION_FAILED", "The operation could not be completed.", 500),
         },
       ],
     });
@@ -897,9 +849,7 @@ describe("Signage dashboard", () => {
     await render(dashboard(host.context));
 
     expect(container.textContent).toContain("Signage could not load this");
-		expect(container.textContent).toContain(
-			"The operation could not be completed.",
-		);
+    expect(container.textContent).toContain("The operation could not be completed.");
     // The rest of the dashboard is still usable: one failing panel is not a failed screen.
     expect(container.querySelectorAll("[role='tab']").length).toBe(5);
   });

tests/browser/offline.test.ts

@@ -391,7 +391,7 @@ describe("a display that loses its network", () => {
         },
         {
           method: "GET",
-          path: "channels/chan-1/display-state",
+          path: /^(viewers\/[^/]+|channels\/chan-1)\/display-state$/u,
           respond: () => {
             if (!reachable) {
               throw new Error("network is gone");

tests/browser/stage0-management.test.tsx

@@ -0,0 +1,414 @@
+// @vitest-environment happy-dom
+import { readdirSync, readFileSync, statSync } from "node:fs";
+import { join } from "node:path";
+import { act } from "react";
+import { createRoot, type Root } from "react-dom/client";
+import { afterEach, beforeEach, describe, expect, it } from "vitest";
+import { audienceKeyFor } from "../../src/ui/panels/DisplaysPanel.js";
+import { SignageDashboard } from "../../src/ui/SignageDashboard.js";
+import {
+  createFakeHost,
+  FAKE_SETTINGS,
+  type FakeHostRoute,
+  jsonResponse,
+} from "./support/fake-host.js";
+
+/**
+ * Stage 0 production-readiness regressions for the management screen.
+ *
+ * Each case is a defect an operator met: an activation that looked lost after changing tabs, a
+ * screen that collapsed to a spinner on every tab switch, deletions with no confirmation, an
+ * internal key presented as something to fill in, and test displays nobody could remove.
+ */
+
+(globalThis as { IS_REACT_ACT_ENVIRONMENT?: boolean }).IS_REACT_ACT_ENVIRONMENT = true;
+
+let container: HTMLElement;
+let root: Root;
+
+beforeEach(() => {
+  container = document.createElement("div");
+  document.body.append(container);
+  root = createRoot(container);
+});
+
+afterEach(async () => {
+  await act(async () => root.unmount());
+  container.remove();
+});
+
+async function settle(): Promise<void> {
+  for (let index = 0; index < 8; index += 1) {
+    await act(async () => {
+      await new Promise((resolve) => setTimeout(resolve, 0));
+    });
+  }
+}
+
+async function click(element: Element | null | undefined): Promise<void> {
+  if (!element) {
+    throw new Error("Expected an element to click.");
+  }
+  await act(async () => (element as HTMLElement).click());
+  await settle();
+}
+
+function button(label: string): HTMLButtonElement | undefined {
+  return [...container.querySelectorAll("button")].find(
+    (candidate) => candidate.textContent?.trim() === label,
+  ) as HTMLButtonElement | undefined;
+}
+
+function tab(label: string): Element | undefined {
+  return [...container.querySelectorAll("[role='tab']")].find(
+    (candidate) => candidate.textContent === label,
+  );
+}
+
+async function choose(select: HTMLSelectElement, value: string): Promise<void> {
+  const setter = Object.getOwnPropertyDescriptor(HTMLSelectElement.prototype, "value")?.set;
+  await act(async () => {
+    setter?.call(select, value);
+    select.dispatchEvent(new Event("change", { bubbles: true }));
+  });
+}
+
+async function type(input: HTMLInputElement, value: string): Promise<void> {
+  const setter = Object.getOwnPropertyDescriptor(HTMLInputElement.prototype, "value")?.set;
+  await act(async () => {
+    setter?.call(input, value);
+    input.dispatchEvent(new Event("input", { bubbles: true }));
+  });
+}
+
+function timeline(id: string, name: string) {
+  return {
+    description: null,
+    eligibleFrom: null,
+    eligibleUntil: null,
+    id,
+    name,
+    revision: 1,
+    updatedAt: "2026-10-01T15:00:00.000Z",
+  };
+}
+
+function group(activeTimelineId: string | null) {
+  return {
+    channels: [{ id: "chan-1", isDefault: true, key: "default", name: "Default" }],
+    id: "group-1",
+    name: "Main",
+    playback: {
+      activeTimelineId,
+      blackout: false,
+      currentSelectionId: null,
+      currentSlotId: null,
+      deadlineAtMs: null,
+      groupId: "group-1",
+      pendingTimelineId: null,
+      remainingMs: null,
+      revision: activeTimelineId === null ? 1 : 2,
+      scheduledActivationAtMs: null,
+      scheduledTimelineId: null,
+      selectionRevision: null,
+      serverNowMs: 1_700_000_000_000,
+      startedAtMs: null,
+      staticAssetId: null,
+      transport: activeTimelineId === null ? ("idle" as const) : ("playing" as const),
+    },
+    revision: 1,
+  };
+}
+
+/** A small, stateful Signage backend: activation really changes what later reads return. */
+function backend(extra: readonly FakeHostRoute[] = []) {
+  let active: string | null = null;
+  const sent: string[] = [];
+  const routes: FakeHostRoute[] = [
+    ...extra,
+    { method: "GET", path: "settings", respond: () => jsonResponse(FAKE_SETTINGS) },
+    {
+      method: "GET",
+      path: "channel-groups",
+      respond: () => jsonResponse({ groups: [group(active)] }),
+    },
+    {
+      method: "GET",
+      path: "timelines",
+      respond: () =>
+        jsonResponse({
+          timelines: [timeline("timeline-1", "Sunday"), timeline("timeline-2", "Easter")],
+        }),
+    },
+    { method: "GET", path: "providers", respond: () => jsonResponse({ providers: [] }) },
+    { method: "GET", path: "images", respond: () => jsonResponse({ images: [] }) },
+    { method: "GET", path: "viewers", respond: () => jsonResponse({ viewers: [] }) },
+    {
+      method: "GET",
+      path: "playback/group-1",
+      respond: () => jsonResponse({ current: null, history: [], snapshot: group(active).playback }),
+    },
+    { method: "GET", path: /^channels\/.*\/display-state$/u, respond: () => jsonResponse({}) },
+    {
+      method: "POST",
+      path: "playback/group-1/activate",
+      respond: ({ init }) => {
+        active = (JSON.parse(String(init?.body)) as { timelineId: string }).timelineId;
+        sent.push(`activate ${active}`);
+        return jsonResponse(group(active).playback);
+      },
+    },
+  ];
+  return { routes, sent };
+}
+
+function mount(host: ReturnType<typeof createFakeHost>) {
+  return act(async () => {
+    root.render(<SignageDashboard context={host.context} copyText={() => Promise.resolve()} />);
+  });
+}
+
+describe("Signage dashboard — Stage 0 regressions", () => {
+  it("shows a timeline activated on Playback as active on Timelines too", async () => {
+    const server = backend();
+    const host = createFakeHost({
+      permissions: ["signage.view", "signage.playback.control", "signage.timelines.manage"],
+      routes: server.routes,
+    });
+    await mount(host);
+    await settle();
+
+    const activate = [...container.querySelectorAll("select")].find((select) =>
+      [...select.options].some((option) => option.textContent === "Choose a timeline…"),
+    ) as HTMLSelectElement;
+    await choose(activate, "timeline-2");
+    await click(button("Now"));
+    expect(server.sent).toEqual(["activate timeline-2"]);
+
+    await click(tab("Timelines"));
+    const row = [...container.querySelectorAll("tr")].find((candidate) =>
+      candidate.textContent?.includes("Easter"),
+    );
+    expect(row?.textContent).toContain("Active in Main");
+    expect(container.querySelector("tr")?.parentElement).not.toBeNull();
+  });
+
+  it("keeps what it loaded when switching tabs, instead of flashing back to a loading state", async () => {
+    let slow = false;
+    const server = backend([
+      {
+        method: "GET",
+        path: "timelines",
+        respond: () =>
+          slow
+            ? new Promise<Response>(() => undefined)
+            : jsonResponse({ timelines: [timeline("timeline-1", "Sunday")] }),
+      },
+    ]);
+    const host = createFakeHost({ permissions: ["signage.view"], routes: server.routes });
+    await mount(host);
+    await settle();
+    await click(tab("Timelines"));
+    expect(container.textContent).toContain("Sunday");
+
+    // The next load never finishes. Coming back must still show the last known list.
+    slow = true;
+    await click(tab("Images"));
+    await click(tab("Timelines"));
+    expect(container.textContent).toContain("Sunday");
+    expect(container.textContent).not.toContain("Loading timelines…");
+  });
+
+  it("deletes an image only after a second, deliberate press, and Cancel stands it down", async () => {
+    const deleted: string[] = [];
+    const image = {
+      byteSize: 1000,
+      contentType: "image/png",
+      createdAt: "2026-10-01T15:00:00.000Z",
+      displayName: "Welcome",
+      expiresAt: null,
+      height: 1080,
+      id: "image-1",
+      originalFilename: "welcome.png",
+      renditions: [],
+      status: "ready",
+      width: 1920,
+    };
+    const server = backend([
+      { method: "GET", path: "images", respond: () => jsonResponse({ images: [image] }) },
+      {
+        method: "DELETE",
+        path: "images/image-1",
+        respond: ({ path }) => {
+          deleted.push(path);
+          return new Response(null, { status: 204 });
+        },
+      },
+    ]);
+    const host = createFakeHost({
+      permissions: ["signage.view", "signage.assets.manage"],
+      routes: server.routes,
+    });
+    await mount(host);
+    await settle();
+    await click(tab("Images"));
+
+    await click(container.querySelector("[data-testid='signage-image-delete-image-1']"));
+    expect(deleted).toEqual([]);
+    expect(button("Delete this image")).toBeDefined();
+    await click(container.querySelector("[data-testid='signage-image-delete-image-1-cancel']"));
+    expect(button("Delete this image")).toBeUndefined();
+    expect(deleted).toEqual([]);
+
+    await click(container.querySelector("[data-testid='signage-image-delete-image-1']"));
+    await click(container.querySelector("[data-testid='signage-image-delete-image-1-confirm']"));
+    expect(deleted).toEqual(["images/image-1"]);
+  });
+
+  it("adds an audience from its name alone, deriving the content key", async () => {
+    const posted: unknown[] = [];
+    const server = backend([
+      {
+        method: "POST",
+        path: "channel-groups/group-1/channels",
+        respond: ({ init }) => {
+          posted.push(JSON.parse(String(init?.body)));
+          return jsonResponse({}, 201);
+        },
+      },
+    ]);
+    const host = createFakeHost({
+      permissions: ["signage.view", "signage.displays.manage"],
+      routes: server.routes,
+    });
+    await mount(host);
+    await settle();
+    await click(tab("Displays"));
+
+    const name = container.querySelector("input[placeholder='Online']") as HTMLInputElement;
+    await type(name, "Watching Online");
+    await click(button("Add audience"));
+    expect(posted).toEqual([{ key: "watching-online", name: "Watching Online" }]);
+  });
+
+  it("labels a signed-in browser and removes an offline entry only after confirmation", async () => {
+    const removed: string[] = [];
+    const viewer = {
+      cachedAssetCount: 0,
+      channelId: "chan-1",
+      deviceId: null,
+      id: "viewer-1",
+      lastError: null,
+      lastSeenAtMs: Date.now() - 600_000,
+      name: "New display",
+      offlineReady: false,
+      online: false,
+      reportedContributionId: null,
+      reportedProviderId: null,
+      reportedSelectionId: null,
+      reportedTimelineId: null,
+    };
+    const server = backend([
+      { method: "GET", path: "viewers", respond: () => jsonResponse({ viewers: [viewer] }) },
+      {
+        method: "DELETE",
+        path: "viewers/viewer-1",
+        respond: ({ path }) => {
+          removed.push(path);
+          return new Response(null, { status: 204 });
+        },
+      },
+    ]);
+    const host = createFakeHost({
+      permissions: ["signage.view", "signage.displays.manage"],
+      routes: server.routes,
+    });
+    await mount(host);
+    await settle();
+    await click(tab("Displays"));
+
+    expect(container.textContent).toContain("Signed-in browser");
+    await click(container.querySelector("[data-testid='signage-display-remove-viewer-1']"));
+    expect(removed).toEqual([]);
+    await click(container.querySelector("[data-testid='signage-display-remove-viewer-1-confirm']"));
+    expect(removed).toEqual(["viewers/viewer-1"]);
+  });
+
+  it("follows playback changes on the management channel, and stops when Playback is left", async () => {
+    const subscriptions: { closed: boolean; onUpdate: ((payload: unknown) => void) | undefined }[] =
+      [];
+    const server = backend();
+    const host = createFakeHost({ permissions: ["signage.view"], routes: server.routes });
+    Object.assign(host.context.realtime, {
+      subscribe(channel: string, handlers: { onUpdate?: (payload: unknown) => void }) {
+        const entry = { closed: false, onUpdate: handlers.onUpdate };
+        if (channel === "management-state") {
+          subscriptions.push(entry);
+        }
+        return { close: () => (entry.closed = true) };
+      },
+    });
+    await mount(host);
+    await settle();
+    const detailReads = () =>
+      host.requests.filter((request) => request.path === "playback/group-1").length;
+    const before = detailReads();
+
+    const live = subscriptions.find((entry) => !entry.closed);
+    await act(async () => {
+      live?.onUpdate?.({ groups: [{ groupId: "group-1", revision: 1, selectionRevision: null }] });
+      live?.onUpdate?.({ groups: [{ groupId: "group-1", revision: 2, selectionRevision: 4 }] });
+    });
+    await settle();
+    expect(detailReads()).toBeGreaterThan(before);
+
+    await click(tab("Images"));
+    expect(subscriptions.every((entry) => entry.closed)).toBe(true);
+  });
+});
+
+describe("audience content keys", () => {
+  it("derives a valid, unique key that is never the reserved default", () => {
+    expect(audienceKeyFor("Online", [])).toBe("online");
+    expect(audienceKeyFor("Online", ["online"])).toBe("online-2");
+    expect(audienceKeyFor("Default", [])).toBe("default-2");
+    expect(audienceKeyFor("2nd service", [])).toBe("audience-2nd-service");
+    expect(audienceKeyFor("   ", [])).toBe("audience");
+    expect(audienceKeyFor("Café — Room!", [])).toBe("cafe-room");
+  });
+});
+
+/** Source-level guards for two product-wide rules (DESIGN §2.1 and §21.1). */
+describe("product rules in the browser source", () => {
+  function sources(directory: string): string[] {
+    return readdirSync(directory).flatMap((entry) => {
+      const path = join(directory, entry);
+      if (statSync(path).isDirectory()) {
+        return sources(path);
+      }
+      return /\.(ts|tsx)$/u.test(entry) ? [path] : [];
+    });
+  }
+  const files = ["src/ui", "src/browser", "src/display"].flatMap(sources);
+
+  it("never uses a browser-native alert, confirm, or prompt", () => {
+    for (const file of files) {
+      expect(readFileSync(file, "utf8"), file).not.toMatch(
+        /\b(?:window\.|globalThis\.)?(?:alert|confirm|prompt)\s*\(/u,
+      );
+    }
+  });
+
+  it("never puts the platform's name in user-facing text", () => {
+    for (const file of files) {
+      const code = readFileSync(file, "utf8")
+        .replace(/\/\*[\s\S]*?\*\//gu, "")
+        .replace(/^\s*\/\/.*$/gmu, "")
+        .replace(/\{\/\*[\s\S]*?\*\/\}/gu, "");
+      // Quoted strings and JSX text; identifiers such as `EkklesiaUiStyles` are not text.
+      expect(code, file).not.toMatch(
+        /["'`][^"'`\n]*\bEkklesia\b[^"'`\n]*["'`]|>[^<{]*\bEkklesia\b/u,
+      );
+    }
+  });
+});

tests/browser/support/fake-host.ts

@@ -37,11 +37,7 @@ export function jsonResponse(body: unknown, status = 200): Response {
   });
 }
 
-export function errorResponse(
-	code: string,
-	message: string,
-	status = 400,
-): Response {
+export function errorResponse(code: string, message: string, status = 400): Response {
   return jsonResponse({ code, message }, status);
 }
 
@@ -74,19 +70,13 @@ export function createFakeHost(options: FakeHostOptions): FakeHost {
           return route.respond({ init, path: normalized });
         }
       }
-			return errorResponse(
-				"SIGNAGE_NOT_FOUND",
-				"The requested resource was not found.",
-				404,
-			);
+      return errorResponse("SIGNAGE_NOT_FOUND", "The requested resource was not found.", 404);
     },
   };
 
   const contributions: ModuleUiContributions = {
     list: (capabilityId) =>
-			capabilityId === "signage.slide-renderer"
-				? (options.contributions ?? [])
-				: [],
+      capabilityId === "signage.slide-renderer" ? (options.contributions ?? []) : [],
     async mount(mountOptions) {
       mounted.push({
         contributionId: mountOptions.contributionId,

tests/drizzle-timelines.test.ts

@@ -65,7 +65,8 @@ function constraintDatabase(existing: readonly { id: string; position: number }[
   };
   return {
     database: {
-      transaction: async (operation: (value: typeof transaction) => Promise<unknown>) => operation(transaction),
+      transaction: async (operation: (value: typeof transaction) => Promise<unknown>) =>
+        operation(transaction),
     } as unknown as ModuleDrizzleDatabase,
     positions,
   };

tests/manifest.test.ts

@@ -177,6 +177,7 @@ describe("Signage server runtime", () => {
       "GET /timelines",
       "GET /timelines/:timelineId",
       "GET /viewers",
+      "GET /viewers/:viewerId/display-state",
       "PATCH /images/:imageId",
       "PATCH /timelines/:timelineId",
       "PATCH /timelines/:timelineId/slots/:slotId",