diff --git a/static/js/history.js b/static/js/history.js
index e319ce2..fc1697b 100644
--- a/static/js/history.js
+++ b/static/js/history.js
@@ -36,10 +36,17 @@
     let _geoCache = {};  // key → label, pre-populated on trip load
 
     function _geoKey(lat, lon) {
-        return `${lat.toFixed(3)},${lon.toFixed(3)}`;
+        const la = typeof lat === 'number' ? lat : parseFloat(lat);
+        const lo = typeof lon === 'number' ? lon : parseFloat(lon);
+        if (isNaN(la) || isNaN(lo)) return null;
+        return `${la.toFixed(3)},${lo.toFixed(3)}`;
     }
 
     function preloadGeocodes(points) {
+        // Pre-fetch geocode labels for all unique coordinates with a small
+        // concurrency cap so the server (which uses slow Nominatim) doesn't
+        // get overwhelmed. The Pi's reverse_geocoder is instant, so this
+        // still works fast there.
         _geoCache = {};
         const seen = new Set();
         const queue = [];
@@ -51,30 +58,27 @@
         }
         if (!queue.length) return;
 
-        // Try batch endpoint first (server has it, Pi falls back to 404)
-        const coords = queue.map(q => ({lat: q.lat, lon: q.lon}));
-        const ctrl = new AbortController();
-        const t = setTimeout(() => ctrl.abort(), 15000);
-        fetch('/api/geocode/batch', {
-            method: 'POST',
-            headers: {'Content-Type': 'application/json'},
-            body: JSON.stringify({coords: coords}),
-            signal: ctrl.signal,
-        })
-        .then(r => { clearTimeout(t); return r.ok ? r.json() : null; })
-        .then(data => {
-            if (data) {
-                for (const q of queue) {
-                    if (data[q.key]) _geoCache[q.key] = data[q.key];
-                }
-            }
-        })
-        .catch(() => { clearTimeout(t); });
+        const CONCURRENCY = 2;
+        let idx = 0;
+        function next() {
+            if (idx >= queue.length) return;
+            const item = queue[idx++];
+            const ctrl = new AbortController();
+            const t = setTimeout(() => ctrl.abort(), 3000);
+            fetch(`/api/geocode?lat=${item.lat}&lon=${item.lon}`, { signal: ctrl.signal })
+                .then(r => { clearTimeout(t); return r.ok ? r.json() : null; })
+                .then(data => {
+                    _geoCache[item.key] = (data && data.label) || null;
+                })
+                .catch(() => { clearTimeout(t); })
+                .finally(() => next());
+        }
+        for (let i = 0; i < CONCURRENCY && i < queue.length; i++) next();
     }
 
     function geocodePoint(lat, lon) {
         const key = _geoKey(lat, lon);
-        if (key === _lastGeoKey) return;
+        if (!key || key === _lastGeoKey) return;
         _lastGeoKey = key;
         const fallback = `${lat.toFixed(5)}, ${lon.toFixed(5)}`;