fix: delete activity removes it from index.json; detail page uses lazy load

delete_activity now updates data_dir/index.json so merge_all no longer
re-adds the summary for a deleted activity, preventing the broken
"Activity not found" state after deletion.

ActivityDetailLoader switches from loadIndex (all year shards) to
loadIndexPaged (first year shard only) + direct file fallback, so
opening an activity detail page no longer downloads the entire history.

bincio/serve/server.py

@@ -1288,6 +1288,17 @@ async def delete_activity(
     if images_dir.exists():
         shutil.rmtree(images_dir)
 
+    # Remove from the extract-level flat index so merge_all doesn't re-add
+    # the summary even though the detail file is gone.
+    index_path = dd / "index.json"
+    if index_path.exists():
+        try:
+            idx = json.loads(index_path.read_text(encoding="utf-8"))
+            idx["activities"] = [a for a in idx.get("activities", []) if a.get("id") != activity_id]
+            index_path.write_text(json.dumps(idx, indent=2, ensure_ascii=False))
+        except Exception:
+            pass  # corrupt index — merge_all will clean up on next run
+
     # Remove from dedup cache so the file can be re-uploaded if needed
     cache_path = dd / ".bincio_cache.json"
     if cache_path.exists():

site/src/components/ActivityDetailLoader.svelte

@@ -1,6 +1,6 @@
 <script lang="ts">
   import { onMount } from 'svelte';
-  import { loadIndex } from '../lib/dataloader';
+  import { loadIndexPaged } from '../lib/dataloader';
   import ActivityDetail from './ActivityDetail.svelte';
   import { isUnlisted } from '../lib/format';
   import type { ActivitySummary, BASIndex } from '../lib/types';
@@ -12,26 +12,13 @@
   let loading = true;
 
   /**
-   * Fallback: if the activity isn't found in the loaded index (e.g. the user's
+   * Build an ActivitySummary stub from a detail JSON object.
-   * shard fetch failed silently), try to fetch the detail file directly from
+   * Used when we fetch the detail file directly without going through the index.
-   * each known user shard's _merged/activities/ directory.
    */
-  async function fetchActivityDirect(id: string): Promise<ActivitySummary | null> {
+  function summaryFromDetail(d: any, detailUrl: string, handle?: string): ActivitySummary {
-    try {
-      const r = await fetch(`${base}data/index.json`);
-      if (!r.ok) return null;
-      const root: BASIndex = await r.json();
-      for (const shard of (root.shards ?? [])) {
-        if (!shard.handle) continue;
-        const url = `${base}data/${shard.handle}/_merged/activities/${id}.json`;
-        try {
-          const dr = await fetch(url);
-          if (!dr.ok) continue;
-          const d = await dr.json();
-          if (d.id !== id) continue;
     return {
       id: d.id,
-            title: d.title ?? id,
+      title: d.title ?? d.id,
       sport: d.sport ?? 'other',
       sub_sport: d.sub_sport ?? null,
       started_at: d.started_at ?? '',
@@ -48,14 +35,50 @@
       mmp: d.mmp ?? null,
       source: d.source ?? null,
       privacy: d.privacy ?? 'public',
-            detail_url: `${shard.handle}/_merged/activities/${id}.json`,
+      detail_url: detailUrl,
       track_url: d.bbox && d.privacy !== 'no_gps'
-              ? `${shard.handle}/_merged/activities/${id}.geojson`
+        ? detailUrl.replace(/\.json$/, '.geojson')
         : null,
       preview_coords: null,
-            handle: shard.handle,
+      ...(handle ? { handle } : {}),
     };
-        } catch { /* try next shard */ }
+  }
+
+  /**
+   * Fallback: fetch the activity detail file directly without loading the index.
+   * Tries single-user path first, then each multi-user handle shard.
+   */
+  async function fetchActivityDirect(id: string): Promise<ActivitySummary | null> {
+    // Single-user: public/data → _merged/, so activities/ resolves directly
+    try {
+      const url = `${base}data/activities/${id}.json`;
+      const r = await fetch(url);
+      if (r.ok) {
+        const d = await r.json();
+        if (d.id === id) return summaryFromDetail(d, `activities/${id}.json`);
+      }
+    } catch { /* fall through */ }
+
+    // Multi-user: try each handle shard
+    try {
+      const r = await fetch(`${base}data/index.json`);
+      if (!r.ok) return null;
+      const root: BASIndex = await r.json();
+      for (const shard of (root.shards ?? [])) {
+        if (!shard.handle) continue;
+        const url = `${base}data/${shard.handle}/_merged/activities/${id}.json`;
+        try {
+          const dr = await fetch(url);
+          if (!dr.ok) continue;
+          const d = await dr.json();
+          if (d.id === id) {
+            return summaryFromDetail(
+              d,
+              `${shard.handle}/_merged/activities/${id}.json`,
+              shard.handle,
+            );
+          }
+        } catch { /* try next */ }
       }
     } catch { /* ignore */ }
     return null;
@@ -68,12 +91,14 @@
     if (!id) { notFound = true; loading = false; return; }
 
     try {
-      const index = await loadIndex(base);
+      // Load only the most-recent year shard — avoids downloading all years just
+      // to look up one activity. Falls back to a direct file fetch if not found.
+      const { index } = await loadIndexPaged(base);
       activity = index.activities.find(a => a.id === id) ?? null;
 
       if (!activity) {
-        // Shard lookup failed — try fetching the detail file directly.
+        // Not in first year shard (old activity) or shard fetch failed —
-        // This handles transient shard fetch errors, stale index state, etc.
+        // fetch the detail file directly to avoid loading all remaining shards.
         activity = await fetchActivityDirect(id);
       }