From 47c447409b624dfdb0743708c3bf191738267a31 Mon Sep 17 00:00:00 2001
From: iris <iris@hyperhive.local>
Date: Thu, 5 Nov 2026 23:09:07 +0100
Subject: [PATCH] swarm-ui: the refresh picker shows a spinner in place of its
 clock while its page is fetching

usePolled reports when a request is in flight (through a new onBusy of the
poller) and holds it on for at least 0.4 seconds, so a quick answer still
reads as a refresh. The picker swaps its clock for the spinner, in the same
box so its width stays, and the spinner stands still where motion is off.
Every page with a picker passes it; a page with several polled requests shows
it while any of them runs. The Jobs page fetches through shared components
and has none yet.
---
 docs/swarm/ui.md                              |  4 +-
 .../swarm-ui/src/pages/AlertsPage.tsx         |  7 +-
 .../swarm-ui/src/pages/ComponentsPage.tsx     |  8 ++
 .../swarm-ui/src/pages/agents/AgentsPage.tsx  |  2 +
 .../src/pages/broadcast/BroadcastComposer.tsx |  7 +-
 .../swarm-ui/src/pages/builds/BuildsPage.tsx  |  9 ++-
 .../pages/notifications/NotificationsPage.tsx | 19 +++--
 .../src/pages/review-runs/ReviewRuns.tsx      |  7 +-
 .../src/pages/schedules/SchedulesPage.tsx     |  8 +-
 .../swarm-ui/src/pages/swarm/HivesCard.tsx    |  7 +-
 .../swarm-ui/src/ui/polled/busy-hold.ts       | 60 +++++++++++++++
 .../packages/swarm-ui/src/ui/polled/poller.ts | 12 ++-
 .../swarm-ui/src/ui/polled/usePolled.ts       | 23 +++++-
 .../ui/refresh-interval/RefreshInterval.css   | 34 ++++++++
 .../ui/refresh-interval/RefreshInterval.tsx   | 13 +++-
 .../packages/swarm-ui/test/busy-hold.test.mjs | 77 +++++++++++++++++++
 .../packages/swarm-ui/test/poller.test.mjs    | 22 ++++++
 17 files changed, 296 insertions(+), 23 deletions(-)
 create mode 100644 frontend/packages/swarm-ui/src/ui/polled/busy-hold.ts
 create mode 100644 frontend/packages/swarm-ui/test/busy-hold.test.mjs

diff --git a/docs/swarm/ui.md b/docs/swarm/ui.md
index 4603eec3..d70c74ad 100644
--- a/docs/swarm/ui.md
+++ b/docs/swarm/ui.md
@@ -38,7 +38,9 @@ Everything it shows comes from [`swarm-controller`](../../swarm-controller/READM
 Pages that refresh on a timer share one polling rule: the page sends no new
 request while the last one is still running, so an older answer never overtakes
 a slow one, and a failed refresh keeps the rows already on screen under an
-error.
+error. While a page is fetching, its refresh picker shows a spinner in place of
+the clock, for at least 0.4 seconds so a quick answer still reads as a refresh.
+The Jobs page has none yet.
 
 The **wanted** badge changes the state of an agent the swarm has declared. For an
 agent the swarm never declared on its hive, such as one only its hive knows
diff --git a/frontend/packages/swarm-ui/src/pages/AlertsPage.tsx b/frontend/packages/swarm-ui/src/pages/AlertsPage.tsx
index fa6bf982..6f08dab0 100644
--- a/frontend/packages/swarm-ui/src/pages/AlertsPage.tsx
+++ b/frontend/packages/swarm-ui/src/pages/AlertsPage.tsx
@@ -75,7 +75,11 @@ function AlertsBody() {
   const [showAll, setShowAll] = useState(false);
   const [intervalMs, setIntervalMs] =
     useState<RefreshIntervalMs>(DEFAULT_INTERVAL_MS);
-  const { data: alerts, error } = usePolled(intervalMs, (signal) =>
+  const {
+    data: alerts,
+    error,
+    refreshing,
+  } = usePolled(intervalMs, (signal) =>
     fetchJson<Alert[]>("/api/alerts", signal),
   );
   const listed = alerts ? listedAlerts(alerts, showAll) : null;
@@ -96,6 +100,7 @@ function AlertsBody() {
           id="alerts-refresh"
           value={intervalMs}
           onChange={setIntervalMs}
+          refreshing={refreshing}
         />
       </div>
       {error ? (
diff --git a/frontend/packages/swarm-ui/src/pages/ComponentsPage.tsx b/frontend/packages/swarm-ui/src/pages/ComponentsPage.tsx
index f1328eba..39c318e1 100644
--- a/frontend/packages/swarm-ui/src/pages/ComponentsPage.tsx
+++ b/frontend/packages/swarm-ui/src/pages/ComponentsPage.tsx
@@ -510,6 +510,14 @@ export function ComponentsPage() {
         <Sample label="editable">
           <RefreshIntervalPickerSample />
         </Sample>
+        <Sample label="refreshing">
+          <RefreshIntervalPicker
+            id="sample-refresh-interval-busy"
+            value={30_000}
+            onChange={() => undefined}
+            refreshing
+          />
+        </Sample>
       </Section>
 
       <Section title="TextField">
diff --git a/frontend/packages/swarm-ui/src/pages/agents/AgentsPage.tsx b/frontend/packages/swarm-ui/src/pages/agents/AgentsPage.tsx
index 7b547161..27e83724 100644
--- a/frontend/packages/swarm-ui/src/pages/agents/AgentsPage.tsx
+++ b/frontend/packages/swarm-ui/src/pages/agents/AgentsPage.tsx
@@ -98,6 +98,7 @@ export function AgentsPage() {
   const {
     data: rows,
     error,
+    refreshing,
     setData: setRows,
   } = usePolled(intervalMs, (signal) =>
     fetchJson<AgentRow[]>("/api/agents/status", signal),
@@ -131,6 +132,7 @@ export function AgentsPage() {
         id="agents-refresh"
         value={intervalMs}
         onChange={setIntervalMs}
+        refreshing={refreshing}
       />
     </>
   );
diff --git a/frontend/packages/swarm-ui/src/pages/broadcast/BroadcastComposer.tsx b/frontend/packages/swarm-ui/src/pages/broadcast/BroadcastComposer.tsx
index 082a035d..13892a13 100644
--- a/frontend/packages/swarm-ui/src/pages/broadcast/BroadcastComposer.tsx
+++ b/frontend/packages/swarm-ui/src/pages/broadcast/BroadcastComposer.tsx
@@ -60,7 +60,11 @@ function storedFilter(): AgentFilter {
 export function BroadcastComposer() {
   const [intervalMs, setIntervalMs] =
     useState<RefreshIntervalMs>(DEFAULT_INTERVAL_MS);
-  const { data: agents, error: loadError } = usePolled(intervalMs, (signal) =>
+  const {
+    data: agents,
+    error: loadError,
+    refreshing,
+  } = usePolled(intervalMs, (signal) =>
     fetchJson<BroadcastAgent[]>("/api/agents/status", signal),
   );
   const [filter, setFilterState] = useState<AgentFilter>(storedFilter);
@@ -173,6 +177,7 @@ export function BroadcastComposer() {
             id="broadcast-refresh"
             value={intervalMs}
             onChange={setIntervalMs}
+            refreshing={refreshing}
           />
         </div>
 
diff --git a/frontend/packages/swarm-ui/src/pages/builds/BuildsPage.tsx b/frontend/packages/swarm-ui/src/pages/builds/BuildsPage.tsx
index 909325f8..0c6ff268 100644
--- a/frontend/packages/swarm-ui/src/pages/builds/BuildsPage.tsx
+++ b/frontend/packages/swarm-ui/src/pages/builds/BuildsPage.tsx
@@ -96,9 +96,11 @@ function BuildsBody() {
   const wanted = wantedRun(useSearch());
   const [intervalMs, setIntervalMs] =
     useState<RefreshIntervalMs>(DEFAULT_INTERVAL_MS);
-  const { data: runs, error } = usePolled(intervalMs, (signal) =>
-    fetchJson<BuildRun[]>(RUNS, signal),
-  );
+  const {
+    data: runs,
+    error,
+    refreshing,
+  } = usePolled(intervalMs, (signal) => fetchJson<BuildRun[]>(RUNS, signal));
   // Which cards are open. Survives a refresh, so a list that updates under
   // you does not fold the card you are reading. A linked build starts open.
   const [open, setOpen] = useState<ReadonlySet<string>>(
@@ -134,6 +136,7 @@ function BuildsBody() {
           id="builds-refresh"
           value={intervalMs}
           onChange={setIntervalMs}
+          refreshing={refreshing}
         />
       </div>
       <p>
diff --git a/frontend/packages/swarm-ui/src/pages/notifications/NotificationsPage.tsx b/frontend/packages/swarm-ui/src/pages/notifications/NotificationsPage.tsx
index d779977e..c2bf805a 100644
--- a/frontend/packages/swarm-ui/src/pages/notifications/NotificationsPage.tsx
+++ b/frontend/packages/swarm-ui/src/pages/notifications/NotificationsPage.tsx
@@ -41,18 +41,24 @@ export function NotificationRouter() {
   const {
     data: view,
     error,
+    refreshing: flowsRefreshing,
     refresh,
   } = usePolled(intervalMs, (signal) =>
     fetchJson<FlowsView>("/api/notify/flows", signal),
   );
   // The router's own answers. Either is 503 while the running router predates
   // it, which the page says in place of the section.
-  const { data: dry, error: dryError } = usePolled(intervalMs, (signal) =>
-    fetchJson<DryRun>(DRY_RUN_URL, signal),
-  );
-  const { data: deliveries, error: deliveriesError } = usePolled(
-    intervalMs,
-    (signal) => fetchJson<DeliveriesView>(DELIVERIES_URL, signal),
+  const {
+    data: dry,
+    error: dryError,
+    refreshing: dryRefreshing,
+  } = usePolled(intervalMs, (signal) => fetchJson<DryRun>(DRY_RUN_URL, signal));
+  const {
+    data: deliveries,
+    error: deliveriesError,
+    refreshing: deliveriesRefreshing,
+  } = usePolled(intervalMs, (signal) =>
+    fetchJson<DeliveriesView>(DELIVERIES_URL, signal),
   );
   // A failed poll keeps the last answer; the counts are shown only while the
   // latest poll worked.
@@ -102,6 +108,7 @@ export function NotificationRouter() {
           id="notifications-refresh"
           value={intervalMs}
           onChange={setIntervalMs}
+          refreshing={flowsRefreshing || dryRefreshing || deliveriesRefreshing}
         />
         <Button variant="primary" onClick={() => draftFrom()}>
           create flow
diff --git a/frontend/packages/swarm-ui/src/pages/review-runs/ReviewRuns.tsx b/frontend/packages/swarm-ui/src/pages/review-runs/ReviewRuns.tsx
index 28205914..544f82cf 100644
--- a/frontend/packages/swarm-ui/src/pages/review-runs/ReviewRuns.tsx
+++ b/frontend/packages/swarm-ui/src/pages/review-runs/ReviewRuns.tsx
@@ -93,7 +93,11 @@ function RunCard({
 export function ReviewRuns() {
   const [intervalMs, setIntervalMs] =
     useState<RefreshIntervalMs>(DEFAULT_INTERVAL_MS);
-  const { data: runs, error } = usePolled(intervalMs, (signal) =>
+  const {
+    data: runs,
+    error,
+    refreshing,
+  } = usePolled(intervalMs, (signal) =>
     fetchJson<ClassifierRun[]>(RUNS, signal),
   );
   // Which cards are expanded. Survives a refresh, so a list that updates
@@ -117,6 +121,7 @@ export function ReviewRuns() {
           id="review-runs-refresh"
           value={intervalMs}
           onChange={setIntervalMs}
+          refreshing={refreshing}
         />
       }
     >
diff --git a/frontend/packages/swarm-ui/src/pages/schedules/SchedulesPage.tsx b/frontend/packages/swarm-ui/src/pages/schedules/SchedulesPage.tsx
index 72129199..aecaf8c6 100644
--- a/frontend/packages/swarm-ui/src/pages/schedules/SchedulesPage.tsx
+++ b/frontend/packages/swarm-ui/src/pages/schedules/SchedulesPage.tsx
@@ -64,6 +64,7 @@ function SchedulesBody() {
   const {
     data: schedules,
     error,
+    refreshing: schedulesRefreshing,
     refresh,
   } = usePolled(intervalMs, (signal) =>
     fetchJson<Schedule[]>("/api/schedules", signal),
@@ -72,7 +73,11 @@ function SchedulesBody() {
   // lists, polled on the same cadence so an agent created after this page
   // opened shows up. A failed load does not block the page, the cards do not
   // need it; the form says the list could not load.
-  const { data: roster, error: rosterError } = usePolled(intervalMs, (signal) =>
+  const {
+    data: roster,
+    error: rosterError,
+    refreshing: rosterRefreshing,
+  } = usePolled(intervalMs, (signal) =>
     fetchJson<AgentRow[]>("/api/agents/status", signal),
   );
   const agentNames = useMemo(() => agentNamesFrom(roster), [roster]);
@@ -159,6 +164,7 @@ function SchedulesBody() {
           id="schedules-refresh"
           value={intervalMs}
           onChange={setIntervalMs}
+          refreshing={schedulesRefreshing || rosterRefreshing}
         />
       </div>
       {error ? (
diff --git a/frontend/packages/swarm-ui/src/pages/swarm/HivesCard.tsx b/frontend/packages/swarm-ui/src/pages/swarm/HivesCard.tsx
index 2b5a2263..e910af66 100644
--- a/frontend/packages/swarm-ui/src/pages/swarm/HivesCard.tsx
+++ b/frontend/packages/swarm-ui/src/pages/swarm/HivesCard.tsx
@@ -116,7 +116,11 @@ const DEFAULT_INTERVAL_MS: RefreshIntervalMs = 30_000;
 function HiveRoster() {
   const [intervalMs, setIntervalMs] =
     useState<RefreshIntervalMs>(DEFAULT_INTERVAL_MS);
-  const { data: hives, error } = usePolled(intervalMs, (signal) =>
+  const {
+    data: hives,
+    error,
+    refreshing,
+  } = usePolled(intervalMs, (signal) =>
     fetchJson<HiveStatus[]>("/api/hives/status", signal),
   );
 
@@ -127,6 +131,7 @@ function HiveRoster() {
           id="hives-refresh"
           value={intervalMs}
           onChange={setIntervalMs}
+          refreshing={refreshing}
         />
       </div>
       {error ? (
diff --git a/frontend/packages/swarm-ui/src/ui/polled/busy-hold.ts b/frontend/packages/swarm-ui/src/ui/polled/busy-hold.ts
new file mode 100644
index 00000000..93dc1220
--- /dev/null
+++ b/frontend/packages/swarm-ui/src/ui/polled/busy-hold.ts
@@ -0,0 +1,60 @@
+// What a refresh indicator shows, from whether a request is in flight: it turns
+// on at once and, once the request is over, stays on for the rest of `minMs`
+// since it came on, so an answer that takes a blink still shows as a refresh
+// instead of a flash. Free of Preact (and of the real clock, for the tests).
+export const MIN_BUSY_MS = 400;
+
+export function createBusyHold(opts: {
+  /** Called with what to show, only when it changes. */
+  show: (shown: boolean) => void;
+  minMs?: number;
+  now?: () => number;
+  after?: (fn: () => void, ms: number) => unknown;
+  cancel?: (timer: unknown) => void;
+}): { busy(busy: boolean): void; stop(): void } {
+  const minMs = opts.minMs ?? MIN_BUSY_MS;
+  const now = opts.now ?? Date.now;
+  const after = opts.after ?? ((fn, ms) => setTimeout(fn, ms));
+  const cancel =
+    opts.cancel ?? ((t) => clearTimeout(t as ReturnType<typeof setTimeout>));
+  let shown = false;
+  let since = 0;
+  let timer: unknown = null;
+
+  function set(next: boolean) {
+    if (next === shown) return;
+    shown = next;
+    opts.show(next);
+  }
+
+  function clear() {
+    if (timer === null) return;
+    cancel(timer);
+    timer = null;
+  }
+
+  return {
+    busy(busy) {
+      if (busy) {
+        clear();
+        if (!shown) since = now();
+        set(true);
+        return;
+      }
+      if (!shown) return;
+      const left = minMs - (now() - since);
+      if (left <= 0) {
+        set(false);
+        return;
+      }
+      clear();
+      timer = after(() => {
+        timer = null;
+        set(false);
+      }, left);
+    },
+    stop() {
+      clear();
+    },
+  };
+}
diff --git a/frontend/packages/swarm-ui/src/ui/polled/poller.ts b/frontend/packages/swarm-ui/src/ui/polled/poller.ts
index 8d32fe26..4b639d61 100644
--- a/frontend/packages/swarm-ui/src/ui/polled/poller.ts
+++ b/frontend/packages/swarm-ui/src/ui/polled/poller.ts
@@ -4,7 +4,9 @@
 // request in flight and asks again, for a refresh that follows a change.
 // `stop` drops the request in flight. An answer from a dropped request never
 // reaches `onData` or `onError`, so an older response cannot overwrite a
-// newer one or land on a page that is gone.
+// newer one or land on a page that is gone. `onBusy` tells when a request goes
+// in flight and when none is any more, however it ended, so a page can show
+// that it is refreshing.
 export interface Poller {
   tick(): void;
   refetch(): void;
@@ -15,29 +17,35 @@ export function createPoller<T>(opts: {
   fetch: (signal: AbortSignal) => Promise<T>;
   onData: (data: T) => void;
   onError: (error: unknown) => void;
+  onBusy?: (busy: boolean) => void;
 }): Poller {
   let current: { controller: AbortController } | null = null;
 
   function start() {
     const run = { controller: new AbortController() };
     current = run;
+    opts.onBusy?.(true);
     opts.fetch(run.controller.signal).then(
       (data) => {
         if (current !== run) return;
         current = null;
+        opts.onBusy?.(false);
         opts.onData(data);
       },
       (error: unknown) => {
         if (current !== run) return;
         current = null;
+        opts.onBusy?.(false);
         opts.onError(error);
       },
     );
   }
 
   function stop() {
-    current?.controller.abort();
+    if (current === null) return;
+    current.controller.abort();
     current = null;
+    opts.onBusy?.(false);
   }
 
   return {
diff --git a/frontend/packages/swarm-ui/src/ui/polled/usePolled.ts b/frontend/packages/swarm-ui/src/ui/polled/usePolled.ts
index c12fb462..38a33c52 100644
--- a/frontend/packages/swarm-ui/src/ui/polled/usePolled.ts
+++ b/frontend/packages/swarm-ui/src/ui/polled/usePolled.ts
@@ -1,4 +1,4 @@
-// A resource refetched on a timer: `{ data, error, refresh, setData }`.
+// A resource refetched on a timer: `{ data, error, refreshing, refresh, setData }`.
 // `data` is `null` until the first answer; a failed fetch sets `error` and
 // keeps the last good `data`; the next good answer clears `error`. The
 // request discipline (skip a tick while one is in flight, drop answers that
@@ -8,12 +8,15 @@
 // does that for a GET. It may change between renders: the latest one runs.
 // `refresh` refetches now, dropping a request in flight, for after a change
 // the page made. `setData` patches what is shown without a request.
+// `refreshing` is true while a request is in flight, and for a short minimum
+// after it starts (`createBusyHold`), for the refresh picker's spinner.
 import { useEffect, useRef, useState } from "preact/hooks";
 import { readApiError, type ProblemDetails } from "@hive/shared/api-error.js";
 import {
   useRefreshInterval,
   type RefreshIntervalMs,
 } from "../refresh-interval/RefreshInterval.js";
+import { createBusyHold } from "./busy-hold.js";
 import { createPoller, type Poller } from "./poller.js";
 
 /** A failed request, carrying the problem the API answered with. */
@@ -43,15 +46,22 @@ export function usePolled<T>(
 ): {
   data: T | null;
   error: ProblemDetails | null;
+  refreshing: boolean;
   refresh: () => void;
   setData: (update: (prev: T | null) => T | null) => void;
 } {
   const [data, setData] = useState<T | null>(null);
   const [error, setError] = useState<ProblemDetails | null>(null);
+  const [refreshing, setRefreshing] = useState(false);
 
   const fetcherRef = useRef(fetcher);
   fetcherRef.current = fetcher;
   const pollerRef = useRef<Poller | null>(null);
+  const holdRef = useRef<ReturnType<typeof createBusyHold> | null>(null);
+  if (holdRef.current === null) {
+    holdRef.current = createBusyHold({ show: setRefreshing });
+  }
+  const hold = holdRef.current;
   if (pollerRef.current === null) {
     pollerRef.current = createPoller<T>({
       fetch: (signal) => fetcherRef.current(signal),
@@ -60,12 +70,19 @@ export function usePolled<T>(
         setError(null);
       },
       onError: (e) => setError(toProblem(e)),
+      onBusy: (busy) => hold.busy(busy),
     });
   }
   const poller = pollerRef.current;
 
-  useEffect(() => () => poller.stop(), [poller]);
+  useEffect(
+    () => () => {
+      poller.stop();
+      hold.stop();
+    },
+    [poller, hold],
+  );
   useRefreshInterval(intervalMs, () => poller.tick());
 
-  return { data, error, refresh: () => poller.refetch(), setData };
+  return { data, error, refreshing, refresh: () => poller.refetch(), setData };
 }
diff --git a/frontend/packages/swarm-ui/src/ui/refresh-interval/RefreshInterval.css b/frontend/packages/swarm-ui/src/ui/refresh-interval/RefreshInterval.css
index bc7cde1e..3df6d21a 100644
--- a/frontend/packages/swarm-ui/src/ui/refresh-interval/RefreshInterval.css
+++ b/frontend/packages/swarm-ui/src/ui/refresh-interval/RefreshInterval.css
@@ -35,6 +35,40 @@
   color: inherit;
 }
 .ui-refresh-picker-icon {
+  display: inline-flex;
+  align-items: center;
+  justify-content: center;
+  width: 1.2em;
+  height: 1.2em;
   font-size: 0.85em;
   line-height: 1;
 }
+
+/* The spinner takes the clock's place: the same box, so the picker keeps its
+   width. Motion follows the page's setting, the same three rules the page
+   switch uses; where motion is off it is a static arc. */
+.ui-refresh-picker-spinner {
+  box-sizing: border-box;
+  width: 1em;
+  height: 1em;
+  border: 2px solid currentColor;
+  border-right-color: transparent;
+  border-radius: 50%;
+  animation: ui-refresh-spin 0.8s linear infinite;
+}
+@keyframes ui-refresh-spin {
+  to {
+    transform: rotate(360deg);
+  }
+}
+@media (prefers-reduced-motion: reduce) {
+  .ui-refresh-picker-spinner {
+    animation: none;
+  }
+}
+:root[data-motion="reduce"] .ui-refresh-picker-spinner {
+  animation: none;
+}
+:root[data-motion="allow"] .ui-refresh-picker-spinner {
+  animation: ui-refresh-spin 0.8s linear infinite;
+}
diff --git a/frontend/packages/swarm-ui/src/ui/refresh-interval/RefreshInterval.tsx b/frontend/packages/swarm-ui/src/ui/refresh-interval/RefreshInterval.tsx
index 9dc97977..94af34a4 100644
--- a/frontend/packages/swarm-ui/src/ui/refresh-interval/RefreshInterval.tsx
+++ b/frontend/packages/swarm-ui/src/ui/refresh-interval/RefreshInterval.tsx
@@ -43,16 +43,23 @@ export function RefreshIntervalPicker({
   id,
   value,
   onChange,
+  refreshing = false,
 }: {
   id: string;
   value: RefreshIntervalMs;
   onChange: (value: RefreshIntervalMs) => void;
+  /** A request is in flight: a spinner takes the clock's place, so the width stays. */
+  refreshing?: boolean;
 }) {
   const current = PRESETS.find((p) => p.value === value) ?? PRESETS[0];
   return (
-    <div class="ui-refresh-picker">
-      <span class="ui-refresh-picker-icon" aria-hidden="true">
-        🕐
+    <div class="ui-refresh-picker" aria-busy={refreshing}>
+      <span
+        class="ui-refresh-picker-icon"
+        aria-hidden="true"
+        title={refreshing ? "refreshing" : undefined}
+      >
+        {refreshing ? <span class="ui-refresh-picker-spinner" /> : "🕐"}
       </span>
       <Listbox
         id={id}
diff --git a/frontend/packages/swarm-ui/test/busy-hold.test.mjs b/frontend/packages/swarm-ui/test/busy-hold.test.mjs
new file mode 100644
index 00000000..d603ab61
--- /dev/null
+++ b/frontend/packages/swarm-ui/test/busy-hold.test.mjs
@@ -0,0 +1,77 @@
+// What the refresh spinner shows: on at once, off only after a minimum time.
+import assert from "node:assert/strict";
+import { test } from "node:test";
+import { createBusyHold } from "../src/ui/polled/busy-hold.ts";
+
+// A clock and a timer the test moves by hand.
+function rig() {
+  let t = 0;
+  const timers = [];
+  const shown = [];
+  const hold = createBusyHold({
+    show: (s) => shown.push(s),
+    minMs: 400,
+    now: () => t,
+    after: (fn, ms) => {
+      const timer = { fn, at: t + ms, live: true };
+      timers.push(timer);
+      return timer;
+    },
+    cancel: (timer) => {
+      timer.live = false;
+    },
+  });
+  const advance = (ms) => {
+    t += ms;
+    for (const timer of timers) {
+      if (timer.live && timer.at <= t) {
+        timer.live = false;
+        timer.fn();
+      }
+    }
+  };
+  return { hold, shown, advance };
+}
+
+test("it turns on at once and, for a quick answer, off only after the minimum", () => {
+  const { hold, shown, advance } = rig();
+  hold.busy(true);
+  assert.deepEqual(shown, [true]);
+  advance(50);
+  hold.busy(false);
+  assert.deepEqual(shown, [true]);
+  advance(349);
+  assert.deepEqual(shown, [true]);
+  advance(1);
+  assert.deepEqual(shown, [true, false]);
+});
+
+test("a slow answer turns it off as soon as it arrives", () => {
+  const { hold, shown, advance } = rig();
+  hold.busy(true);
+  advance(900);
+  hold.busy(false);
+  assert.deepEqual(shown, [true, false]);
+});
+
+test("a new request while it is held keeps it on and cancels the pending off", () => {
+  const { hold, shown, advance } = rig();
+  hold.busy(true);
+  advance(100);
+  hold.busy(false);
+  hold.busy(true);
+  advance(1000);
+  assert.deepEqual(shown, [true]);
+  hold.busy(false);
+  assert.deepEqual(shown, [true, false]);
+});
+
+test("stop drops a pending off, and busy(false) with nothing shown does nothing", () => {
+  const { hold, shown, advance } = rig();
+  hold.busy(false);
+  hold.busy(true);
+  hold.busy(false);
+  hold.stop();
+  advance(1000);
+  assert.deepEqual(shown, [true]);
+});
diff --git a/frontend/packages/swarm-ui/test/poller.test.mjs b/frontend/packages/swarm-ui/test/poller.test.mjs
index 78e08214..2d40e9f2 100644
--- a/frontend/packages/swarm-ui/test/poller.test.mjs
+++ b/frontend/packages/swarm-ui/test/poller.test.mjs
@@ -92,3 +92,25 @@ test("the answer of a dropped request that fails is not reported", async () => {
   await flush();
   assert.deepEqual(sink.seen.error, []);
 });
+
+test("onBusy follows a request in flight, however it ends", async () => {
+  const { calls, fetch } = manualFetch();
+  const sink = collect();
+  const busy = [];
+  const poller = createPoller({ fetch, ...sink, onBusy: (b) => busy.push(b) });
+  poller.tick();
+  poller.tick();
+  assert.deepEqual(busy, [true]);
+  calls[0].resolve("one");
+  await flush();
+  assert.deepEqual(busy, [true, false]);
+  poller.tick();
+  calls[1].reject(new Error("boom"));
+  await flush();
+  assert.deepEqual(busy, [true, false, true, false]);
+  poller.tick();
+  poller.stop();
+  assert.deepEqual(busy, [true, false, true, false, true, false]);
+  poller.stop();
+  assert.equal(busy.length, 6);
+});