diff --git a/backend/src/lib/weather-fetch.js b/backend/src/lib/weather-fetch.js
index 156682e..f6ecd56 100644
--- a/backend/src/lib/weather-fetch.js
+++ b/backend/src/lib/weather-fetch.js
@@ -10,13 +10,15 @@
 // other endpoints could actually serve. This matters because Met Office DataHub
 // sells "Global Spot" and "Forecast" as SEPARATE subscriptions with separate keys
 // (settings' met_office integration: api_key = Spot, forecast_api_key = Forecast,
-// optional) — only Spot (used here for daily) has ever been confirmed live (hvac,
-// 2026-08-25); hourly/three-hourly try forecast_api_key first (falling back to
-// api_key if no separate Forecast key is configured), since Spot alone may not
-// actually be subscribed to those endpoints. Field names for hourly/three-hourly
-// are taken from the published Met Office DataHub docs, still not verified live —
-// a mismatch there just throws and that tier falls back to Open-Meteo, same as an
-// outright subscription failure.
+// optional) — only Spot's daily endpoint has ever been confirmed live (hvac,
+// 2026-08-25). Which key actually covers hourly/three-hourly is NOT documented
+// anywhere we could find, and a first guess (Forecast key -> hourly) was tried and
+// confirmed wrong via settings' met_office test route — so every tier just tries
+// whichever keys are configured (Spot then Forecast, see fetchWithKeys) and keeps
+// whichever works, discovered at runtime rather than assumed. Field names for
+// hourly/three-hourly are taken from the published Met Office DataHub docs, still
+// not verified live — a mismatch there just throws and that tier falls back to
+// Open-Meteo, same as an outright subscription failure.
 import { pool, setStatus } from '../db.js'
 import { iconFromMetOffice, iconFromOpenMeteo } from './icons.js'
 
@@ -217,6 +219,25 @@ function openMeteoAstroPoints(dailyRows, astroKeys) {
     .map(r => ({ date: r.dateKey, sunrise: r.sunrise, sunset: r.sunset }))
 }
 
+// Tries each configured key in turn against the same tier, returning the first
+// success. Which of Spot/Forecast actually covers which endpoint isn't documented
+// anywhere we could find, and a first guess (Forecast -> hourly specifically) was
+// tried and confirmed wrong live via settings' met_office test route — so rather
+// than assuming again, every tier just tries whatever keys are configured and
+// keeps whichever one actually works, discovered at runtime instead of guessed at.
+async function fetchWithKeys(fetchFn, keys) {
+  const errors = []
+  for (const [name, key] of keys) {
+    if (!key) continue
+    try {
+      return await fetchFn(key)
+    } catch (err) {
+      errors.push(`${name}: ${err.message}`)
+    }
+  }
+  throw new Error(errors.join('; ') || 'no Met Office key configured')
+}
+
 // ── Storage ──────────────────────────────────────────────────────────────
 async function replaceResolution(resolution, points) {
   const client = await pool.connect()
@@ -293,13 +314,15 @@ export async function refreshForecast(log = console) {
     let hourlyPoints = [], threeHourlyPoints = [], dailyPoints = [], astroPoints = []
 
     if (metOffice?.api_key) {
-      const spotKey = metOffice.api_key
-      const forecastKey = metOffice.forecast_api_key || metOffice.api_key
+      // Spot first (the one confirmed working, for daily) then Forecast, for
+      // every tier — see fetchWithKeys' comment for why this doesn't assume
+      // which key covers which endpoint.
+      const keys = [['Spot', metOffice.api_key], ['Forecast', metOffice.forecast_api_key]]
 
       const [hourlyR, threeHourlyR, dailyR] = await Promise.allSettled([
-        fetchMetOfficeHourly(lat, lon, forecastKey),
-        fetchMetOfficeThreeHourly(lat, lon, forecastKey, dayKeys),
-        fetchMetOfficeDaily(lat, lon, spotKey, skipKeys, astroKeys),
+        fetchWithKeys(key => fetchMetOfficeHourly(lat, lon, key), keys),
+        fetchWithKeys(key => fetchMetOfficeThreeHourly(lat, lon, key, dayKeys), keys),
+        fetchWithKeys(key => fetchMetOfficeDaily(lat, lon, key, skipKeys, astroKeys), keys),
       ])
 
       if (hourlyR.status === 'fulfilled') {