diff --git a/mobile/app/(tabs)/index.tsx b/mobile/app/(tabs)/index.tsx
index da20d17..144cb1b 100644
--- a/mobile/app/(tabs)/index.tsx
+++ b/mobile/app/(tabs)/index.tsx
@@ -20,10 +20,13 @@ export default function FeedScreen() {
       setSyncMsg(result.error);
     } else if (result.total === 0) {
       setSyncMsg('No activities on instance');
-    } else if (result.synced === 0) {
+    } else if (result.synced === 0 && !result.fetched) {
       setSyncMsg(`Up to date (${result.total} activities)`);
     } else {
-      setSyncMsg(`${result.synced} of ${result.total} activities synced`);
+      const parts = [];
+      if (result.synced > 0) parts.push(`${result.synced} new`);
+      if (result.fetched) parts.push(`${result.fetched} full dataset${result.fetched === 1 ? '' : 's'}`);
+      setSyncMsg(`Synced: ${parts.join(', ')} (${result.total} total)`);
     }
     setTimeout(() => setSyncMsg(null), 3500);
   }, [db]);
diff --git a/mobile/app/(tabs)/settings.tsx b/mobile/app/(tabs)/settings.tsx
index b672dfc..b564075 100644
--- a/mobile/app/(tabs)/settings.tsx
+++ b/mobile/app/(tabs)/settings.tsx
@@ -9,10 +9,11 @@ import { deleteRemoteActivities, getSetting, setSetting, useSetting } from '@/db
 export default function SettingsScreen() {
   const db = useSQLiteContext();
 
-  const storedUrl    = useSetting('instance_url') ?? '';
-  const storedHandle = useSetting('handle') ?? '';
-  const storedPath   = useSetting('auto_import_path') ?? '';
-  const storedToken  = useSetting('api_token');
+  const storedUrl      = useSetting('instance_url') ?? '';
+  const storedHandle   = useSetting('handle') ?? '';
+  const storedPath     = useSetting('auto_import_path') ?? '';
+  const storedToken    = useSetting('api_token');
+  const storedSyncMode = (useSetting('sync_mode') ?? 'summaries') as 'summaries' | 'full';
 
   const [instanceUrl, setInstanceUrl] = useState(storedUrl);
   const [handle,      setHandle]      = useState(storedHandle);
@@ -174,6 +175,26 @@ export default function SettingsScreen() {
         </Section>
       )}
 
+      <Section title="Sync">
+        <View style={styles.modeRow}>
+          <ModeButton
+            label="Summaries only"
+            active={storedSyncMode === 'summaries'}
+            onPress={() => setSetting(db, 'sync_mode', 'summaries')}
+          />
+          <ModeButton
+            label="Full data"
+            active={storedSyncMode === 'full'}
+            onPress={() => setSetting(db, 'sync_mode', 'full')}
+          />
+        </View>
+        <Text style={styles.hint}>
+          {storedSyncMode === 'full'
+            ? 'Downloads map route and elevation chart for every activity during sync. Uses more storage and takes longer.'
+            : 'Syncs activity summaries only. Map and chart are fetched on demand when you open an activity.'}
+        </Text>
+      </Section>
+
       <Section title="Data">
         <Pressable
           style={[styles.resetButton, resetArmed && styles.resetButtonArmed]}
@@ -231,6 +252,17 @@ function Field({
   );
 }
 
+function ModeButton({ label, active, onPress }: { label: string; active: boolean; onPress: () => void }) {
+  return (
+    <Pressable
+      style={[styles.modeButton, active && styles.modeButtonActive]}
+      onPress={onPress}
+    >
+      <Text style={[styles.modeButtonText, active && styles.modeButtonTextActive]}>{label}</Text>
+    </Pressable>
+  );
+}
+
 function Row({ label, value }: { label: string; value: string }) {
   return (
     <View style={styles.row}>
@@ -282,6 +314,11 @@ const styles = StyleSheet.create({
   disconnectText: { color: '#71717a', fontSize: 14 },
   msgOk:  { color: '#86efac', fontSize: 13, paddingHorizontal: 12, paddingBottom: 10 },
   msgErr: { color: '#fca5a5', fontSize: 13, paddingHorizontal: 12, paddingBottom: 10 },
+  modeRow:            { flexDirection: 'row', gap: 8, padding: 12 },
+  modeButton:         { flex: 1, paddingVertical: 9, borderRadius: 8, borderWidth: 1, borderColor: '#3f3f46', alignItems: 'center' },
+  modeButtonActive:   { backgroundColor: '#1e3a5f', borderColor: '#2563eb' },
+  modeButtonText:     { color: '#71717a', fontSize: 13, fontWeight: '500' },
+  modeButtonTextActive: { color: '#60a5fa' },
   resetButton: {
     margin: 12, paddingVertical: 10, alignItems: 'center',
     borderRadius: 8, borderWidth: 1, borderColor: '#3f3f46',
diff --git a/mobile/db/sync.ts b/mobile/db/sync.ts
index b5551d2..2e46e3a 100644
--- a/mobile/db/sync.ts
+++ b/mobile/db/sync.ts
@@ -1,7 +1,7 @@
 import type { SQLiteDatabase } from 'expo-sqlite';
 import { getSetting, upsertRemoteActivity } from './queries';
 
-export type SyncResult = { synced: number; total: number; error?: string };
+export type SyncResult = { synced: number; total: number; fetched?: number; error?: string };
 
 export async function syncFeed(db: SQLiteDatabase): Promise<SyncResult> {
   const instanceUrl = (await getSetting(db, 'instance_url'))?.replace(/\/$/, '');
@@ -30,6 +30,8 @@ export async function syncFeed(db: SQLiteDatabase): Promise<SyncResult> {
   const data: { activities?: RemoteSummary[] } = await resp.json();
   const activities = data.activities ?? [];
 
+  const syncMode = (await getSetting(db, 'sync_mode')) ?? 'summaries';
+
   let synced = 0;
   for (const a of activities) {
     const detailJson = JSON.stringify({
@@ -48,7 +50,46 @@ export async function syncFeed(db: SQLiteDatabase): Promise<SyncResult> {
     if (changed) synced++;
   }
 
-  return { synced, total: activities.length };
+  if (syncMode !== 'full') {
+    return { synced, total: activities.length };
+  }
+
+  // Full mode: fetch geojson + timeseries for any activity missing them
+  const headers = { Authorization: `Bearer ${token}` };
+  let fetched = 0;
+  for (const a of activities) {
+    const row = db.getFirstSync<{ g: number; t: number }>(
+      'SELECT (geojson IS NOT NULL) as g, (timeseries_json IS NOT NULL) as t FROM activities WHERE id = ?',
+      [a.id],
+    );
+    if (row?.g && row?.t) continue;
+
+    let gj: string | null = null;
+    let ts: string | null = null;
+    try {
+      if (!row?.g) {
+        const r = await fetch(`${instanceUrl}/api/activity/${a.id}/geojson`, { headers });
+        if (r.ok) gj = await r.text();
+      }
+      if (!row?.t) {
+        const r = await fetch(`${instanceUrl}/api/activity/${a.id}/timeseries`, { headers });
+        if (r.ok) ts = await r.text();
+      }
+    } catch {}
+
+    if (gj !== null || ts !== null) {
+      await db.runAsync(
+        `UPDATE activities SET
+           geojson        = COALESCE(geojson,        ?),
+           timeseries_json = COALESCE(timeseries_json, ?)
+         WHERE id = ? AND origin = 'remote'`,
+        [gj, ts, a.id],
+      );
+      fetched++;
+    }
+  }
+
+  return { synced, total: activities.length, fetched };
 }
 
 type RemoteSummary = {