fix(diagnostics): say which read failed, and let Live restart

- "Load older" is not offered off a loading filter's placeholder rows,
  whose cursor belongs to the previous filter.
- A failed older page, stale rows and missing counts each get their own
  message (HU/EN).
- Live shows as off once a failed read stopped the polling; pressing it
  again reads now.

frontend/src/components/AdminLogs.dom.test.tsx

@@ -197,6 +197,44 @@ describe("AdminLogs", () => {
     const reads = logsMock.mock.calls.length;
     await act(async () => vi.advanceTimersByTimeAsync(12000));
     expect(logsMock.mock.calls.length).toBe(reads);
+    // The button says polling stopped, and pressing it reads again.
+    const liveButton = screen.getByRole("button", { name: "adminLogs.live" });
+    expect(liveButton.getAttribute("aria-pressed")).toBe("false");
+    fireEvent.click(liveButton);
+    await settle();
+    expect(logsMock.mock.calls.length).toBe(reads + 1);
+  });
+
+  it("a failed older page says so, not that the list is out of date", async () => {
+    logsMock.mockImplementation(async (_q, before) => {
+      if (before !== null) throw new Error("500");
+      return { items: [row(2)], accounts: {}, next_cursor: "c1" };
+    });
+    renderConsole();
+    await waitFor(() => expect(lines()).toHaveLength(1));
+
+    fireEvent.click(screen.getByRole("button", { name: "adminLogs.older" }));
+
+    expect((await screen.findByRole("alert")).textContent).toContain("adminLogs.olderFailed");
+  });
+
+  it("offers no older page while a filter change loads", async () => {
+    let landErrors!: (page: LogPage) => void;
+    logsMock.mockImplementation((q) =>
+      q.levels
+        ? new Promise<LogPage>((resolve) => (landErrors = resolve))
+        : Promise.resolve({ items: [row(2)], accounts: {}, next_cursor: "c1" }),
+    );
+    renderConsole();
+    await waitFor(() => expect(lines()).toHaveLength(1));
+    expect(screen.queryByRole("button", { name: "adminLogs.older" })).toBeTruthy();
+
+    fireEvent.click(screen.getByRole("button", { name: /settings\.myLog\.filters\.error/ }));
+    await waitFor(() => expect(landErrors).toBeTypeOf("function"));
+
+    // The rows on screen are the previous filter's: their cursor is not this list's.
+    expect(screen.queryByRole("button", { name: "adminLogs.older" })).toBeNull();
+    await act(async () => landErrors({ items: [row(1)], accounts: {}, next_cursor: null }));
   });
 
   it("copies every loaded line, oldest first", async () => {

frontend/src/components/AdminLogs.tsx

@@ -105,11 +105,26 @@ export default function AdminLogs() {
     placeholderData: keepPreviousData,
     refetchInterval: (q) => (live && q.state.status !== "error" ? LIVE_MS * 4 : false),
   });
-  // What "Load older" continues from — read off the data, since `hasNextPage` is off while live.
-  const olderCursor = logs.data?.pages[logs.data.pages.length - 1]?.next_cursor ?? null;
-  // A read failed while rows (or counts) were already on screen: they are kept, and said to be old.
-  const stale = (logs.isError && !!logs.data) || facets.isError;
-  const retryStale = () => {
+  // A failed read stops the polling (the intervals above); the button shows that, and pressing it
+  // again reads now.
+  const polling = live && !logs.isError;
+  // What "Load older" continues from — read off the data, since `hasNextPage` is off while live; not
+  // off placeholder rows, which are the previous filter's.
+  const olderCursor = logs.isPlaceholderData
+    ? null
+    : (logs.data?.pages[logs.data.pages.length - 1]?.next_cursor ?? null);
+  // A read that failed while lines were on screen: they are kept, and the message says what the
+  // failure means for them. (With no lines, the list's own error state says it.)
+  const failure = !logs.data
+    ? null
+    : logs.isFetchNextPageError
+      ? "olderFailed"
+      : logs.isError || (facets.isError && facets.data)
+        ? "stale"
+        : facets.isError
+          ? "countsFailed"
+          : null;
+  const retryFailed = () => {
     if (logs.isFetchNextPageError) void logs.fetchNextPage();
     else if (logs.isError) void logs.refetch();
     if (facets.isError) void facets.refetch();
@@ -129,13 +144,17 @@ export default function AdminLogs() {
     id === "none" ? t("adminLogs.noAccount") : (accounts[id] ?? `#${id}`);
 
   const toggleLive = () => {
-    if (!live) {
-      // Watching the top: drop the older pages now; `liveRef` keeps each tick to the first page.
-      qc.setQueryData<typeof logs.data>(key, (d) =>
-        d ? { pages: d.pages.slice(0, 1), pageParams: d.pageParams.slice(0, 1) } : d,
-      );
+    if (polling) {
+      setLive(false);
+      return;
     }
-    setLive(!live);
+    // Watching the top: drop the older pages now; `liveRef` keeps each tick to the first page.
+    qc.setQueryData<typeof logs.data>(key, (d) =>
+      d ? { pages: d.pages.slice(0, 1), pageParams: d.pageParams.slice(0, 1) } : d,
+    );
+    setLive(true);
+    if (logs.isError) void logs.refetch();
+    if (facets.isError) void facets.refetch();
   };
 
   const loadOlder = () => {
@@ -256,10 +275,10 @@ export default function AdminLogs() {
             />
             <span className="ml-auto flex gap-1.5">
               <Button
-                variant={live ? "outline-accent" : "outline"}
+                variant={polling ? "outline-accent" : "outline"}
                 size="xs"
                 icon={<Radio className="h-3.5 w-3.5" />}
-                aria-pressed={live}
+                aria-pressed={polling}
                 onClick={toggleLive}
               >
                 {t("adminLogs.live")}
@@ -296,14 +315,14 @@ export default function AdminLogs() {
             </div>
           )}
 
-          {stale && (
+          {failure && (
             <StateMessage
               tone="error"
               compact
-              onRetry={retryStale}
+              onRetry={retryFailed}
               className="border-b border-border"
             >
-              {t("adminLogs.stale")}
+              {t(`adminLogs.${failure}`)}
             </StateMessage>
           )}
 

frontend/src/i18n/locales/en/adminLogs.json

@@ -27,6 +27,8 @@
   "showJob": "Only this job's lines",
   "empty": "No lines match the filters.",
   "stale": "The last refresh failed; what you see may be out of date.",
+  "olderFailed": "Couldn't load the older lines.",
+  "countsFailed": "The filter counts didn't load.",
   "count_one": "{{count}} line loaded · newest first",
   "count_other": "{{count}} lines loaded · newest first",
   "older": "Load older",

frontend/src/i18n/locales/hu/adminLogs.json

@@ -27,6 +27,8 @@
   "showJob": "Csak ennek a jobnak a sorai",
   "empty": "Nincs a szűrésnek megfelelő sor.",
   "stale": "Az utolsó frissítés nem sikerült, amit látsz, elavult lehet.",
+  "olderFailed": "Nem sikerült betölteni a régebbi sorokat.",
+  "countsFailed": "A szűrők számai nem töltődtek be.",
   "count_one": "{{count}} sor betöltve · a legújabb felül",
   "count_other": "{{count}} sor betöltve · a legújabb felül",
   "older": "Régebbiek betöltése",