fix(status): fetch last poll once per app session

src/App.tsx

@@ -25,6 +25,7 @@ import { clearTrips, readTripQuery, readTrips, removeTrip, toggleTrip, tripQuery
 import type { Journey, Lang, Suggestion } from "./lib/transit/types"
 import coordinatesFile from "../data/en/coordinates.json"
 import { accessByCode } from "./lib/status/pack"
+import { loadLastPoll } from "./lib/status/lastPoll"
 import { loadStatus, loadStatusHistory, statusClock } from "./lib/status/load"
 import { locationCopy, readLocation, rememberedLocation, resetLocationMemory, type LocationResult } from "./lib/status/location"
 import { nearestBoardable, nearestStation, type Coordinate } from "./lib/status/nearest"
@@ -166,6 +167,10 @@ export function App() {
   const [helpNotice, setHelpNotice] = useState<string | null>(null)
   const [trips, setTrips] = useState<SavedTrip[]>(readStoredTrips)
   const [savedMark, setSavedMark] = useState<{ n: number; fromCode: string; toCode: string } | null>(null)
+  const [statusPolledAt, setStatusPolledAt] = useState<string | null>(null)
+  useEffect(() => {
+    void loadLastPoll().then(setStatusPolledAt)
+  }, [])
   useEffect(() => {
     if (tab !== "saved" || savedMark === null) return
     const id = window.setTimeout(() => setSavedMark(null), 1100)
@@ -838,6 +843,7 @@ export function App() {
         here={here}
         locating={locating}
         locateNote={locateNote}
+        polledAt={statusPolledAt}
         onLocate={() =>
           readHere(
             () => undefined,

src/lib/status/lastPoll.test.ts

@@ -1,4 +1,4 @@
-import { describe, expect, it } from "vitest"
+import { afterEach, describe, expect, it, vi } from "vitest"
 import { readLastPollPayload } from "./lastPoll"
 
 describe("last poll payload", () => {
@@ -12,3 +12,24 @@ describe("last poll payload", () => {
     expect(readLastPollPayload(null)).toBeNull()
   })
 })
+
+describe("loadLastPoll session cache", () => {
+  afterEach(() => {
+    vi.unstubAllGlobals()
+    vi.resetModules()
+  })
+
+  it("hits the network only once per module session", async () => {
+    const fetchMock = vi.fn(async () =>
+      new Response(JSON.stringify({ polledAt: "2026-10-13T14:00:00.000" }), {
+        status: 200,
+        headers: { "Content-Type": "application/json" },
+      }),
+    )
+    vi.stubGlobal("fetch", fetchMock)
+    const mod = await import("./lastPoll")
+    await expect(mod.loadLastPoll()).resolves.toBe("2026-10-13T14:00:00.000")
+    await expect(mod.loadLastPoll()).resolves.toBe("2026-10-13T14:00:00.000")
+    expect(fetchMock).toHaveBeenCalledTimes(1)
+  })
+})

src/lib/status/lastPoll.ts

@@ -1,6 +1,8 @@
 /** Trial: last successful Status bake dispatch from the Cloudflare ping Worker. */
 export const STATUS_PING_URL = "https://detro-status-ping.rushforlinux.workers.dev"
 
+let sessionPoll: Promise<string | null> | null = null
+
 export function readLastPollPayload(raw: unknown): string | null {
   if (!raw || typeof raw !== "object") return null
   const polledAt = (raw as { polledAt?: unknown }).polledAt
@@ -20,3 +22,9 @@ export async function fetchLastPoll(signal?: AbortSignal): Promise<string | null
     return null
   }
 }
+
+/** One network read per app session (tab navigation must not refetch). */
+export function loadLastPoll(): Promise<string | null> {
+  if (!sessionPoll) sessionPoll = fetchLastPoll()
+  return sessionPoll
+}

src/ui/StatusView.tsx

@@ -1,8 +1,7 @@
-import { useEffect, useMemo, useRef, useState, type CSSProperties, type KeyboardEvent } from "react"
+import { useMemo, useRef, useState, type CSSProperties, type KeyboardEvent } from "react"
 import { ArrowRight, LocateFixed, X } from "lucide-react"
 import type { Copy } from "../i18n/copy"
 import { lineIndexFor, searchCatalog, type CatalogStation } from "../lib/dmrc/snapshot"
-import { fetchLastPoll } from "../lib/status/lastPoll"
 import { statusStamp12, statusTime12 } from "../lib/status/load"
 import { nearestOpen } from "../lib/status/gates"
 import { nearestStation, type Coordinate } from "../lib/status/nearest"
@@ -29,6 +28,7 @@ export function StatusView({
   onLocate,
   onPlan,
   onClear,
+  polledAt = null,
   initialFrom = null,
   initialDest = null,
 }: {
@@ -45,6 +45,7 @@ export function StatusView({
   onLocate: () => void
   onPlan: (from: Stop, to: Stop) => void
   onClear: () => void
+  polledAt?: string | null
   initialFrom?: string | null
   initialDest?: string | null
 }) {
@@ -56,7 +57,6 @@ export function StatusView({
   const [looked, setLooked] = useState<Stop | null>(() => named(initialFrom, names) ?? named(initialDest, names))
   const [openLine, setOpenLine] = useState<string | null>(null)
   const [focus, setFocus] = useState<string | null>(null)
-  const [polledAt, setPolledAt] = useState<string | null>(null)
   const closedCount = Object.keys(pack.stations).length
   const openCount = Math.max(0, names.size - closedCount)
   const clock = pack.fetchedAt ? statusTime12(pack.fetchedAt) : ""
@@ -92,17 +92,6 @@ export function StatusView({
   const suggestions = useMemo(() => (query.trim() ? searchCatalog(stations, "en", query).slice(0, 8) : []), [query, stations])
   const listOpen = searchOpen && query.trim().length > 0
 
-  useEffect(() => {
-    let alive = true
-    // Do not abort on Strict Mode remount — a cancelled first request looks like a failure in DevTools.
-    fetchLastPoll().then((value) => {
-      if (alive) setPolledAt(value)
-    })
-    return () => {
-      alive = false
-    }
-  }, [])
-
   function lookAt(stop: Stop, lineCode?: string | null) {
     setLooked(stop)
     setQuery("")