jumble/docs/performance-fixes.md

Performance fixes (audit follow-up)

This document records seven fixes identified during a sluggishness audit. They are ordered by impact and should be applied in sequence.

Executive summary

Sluggishness came mainly from main-thread work that scales with feed size and React context churn that re-renders large subtrees. Orphaned files added maintenance noise but did not affect runtime.

The largest win is in NoteList: expensive per-event work ran inside a filter that scans up to 2,500 events on every dependency change.

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Fix 1 — Hoist pinnedEventHexIdSet out of shouldHideEvent

File: src/components/NoteList/index.tsx

Problem: shouldHideEvent rebuilt pinnedEventHexIdSet (with decode() per pin) inside the per-event callback. That callback is used in a useMemo that scans up to MAX_TIMELINE_EVENTS_SCAN_FOR_VISIBLE (2500) rows, so pin decoding ran up to 2,500× per filter pass.

Fix: Compute pinnedEventHexIdSet once in a useMemo keyed on pinnedEventIds. shouldHideEvent reads the memoized set.

Expected impact: Largest feed-filter win; small diff.

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Fix 2 — Cap profile-prefetch walks to visible + lookahead

File: src/components/NoteList/index.tsx

Problem: A debounced useEffect walked all of timelineEventsForFilter and newEvents on every buffer change, then enqueued profile/emoji prefetch for every author found.

Fix: Walk only filteredEvents.slice(0, showCount + prefetchMargin) (capped, e.g. 120 rows) plus a small slice of newEvents (e.g. 32). Keep the existing note-stats slice for visible rows.

Expected impact: Fewer redundant kind-0 fetches and less main-thread work when the timeline buffer grows.

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Fix 3 — Memoize MuteListProvider and ContentPolicyProvider context values

Files:

• src/providers/MuteListProvider.tsx
• src/providers/ContentPolicyProvider.tsx

Problem: Both providers passed a new value object every render. Handler functions were recreated each render. Consumers include NoteList, Note, Image, VideoPlayer, etc., so parent re-renders cascaded through the feed.

Fix:

• Wrap mute handlers in useCallback.
• Wrap policy updaters in useCallback.
• Wrap provider value in useMemo with stable dependencies.

Expected impact: Fewer wide subtree re-renders when unrelated parent state changes.

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Fix 4 — Cap iterateProfileEvents IndexedDB scan

File: src/services/indexed-db.service.ts

Problem: iterateProfileEvents loaded all kind-0 rows from IndexedDB into a single events[] array before chunked callback processing. Large offline caches caused a big allocation on first @-mention search or session prewarm.

Fix: Cap rows collected during the cursor pass (MAX_PROFILE_EVENTS_ITERATE, e.g. 8,000). Log when truncated. Keep chunked requestAnimationFrame yields during callback processing.

Expected impact: Bounded memory and faster startup on accounts with very large profile caches.

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Fix 5 — Tune ReplaceableEventService batching during scroll

Files:

• src/lib/scroll-activity.service.ts (new)
• src/components/NoteList/index.tsx
• src/services/client-replaceable-events.service.ts

Problem: maxBatchSize: 200 with 100ms batching queued many kind-0 fetches during fast scrolling, competing with timeline REQs (console: Large batch detected, limiting processing).

Fix:

• Add a lightweight scroll-activity signal (markScrolling() from feed scroll handlers).
• Lower maxBatchSize (64) and lengthen batchScheduleFn delay while scrolling (200ms vs 100ms idle).

Expected impact: Profile fetches defer during scroll; timeline paint stays responsive.

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Fix 6 — Delete unused files and junk

Problem: Knip reported 16 unused files plus src/services/Untitled (accidental single-character junk). No runtime cost, but bundle/clarity noise.

Files removed:

Cluster	Files
Connected relays UI	ActiveRelaysDropdownSection.tsx, ActiveRelaysIconGrid.tsx, active-relays-display.ts
Old Explore tabs	Explore/index.tsx, ExploreFavoriteRelays.tsx, ExplorePopularRelays.tsx, ExploreRelayReviews.tsx
Other UI	FollowingFavoriteRelayList, SeenOnButton, NotificationThreadWatchButtons, ProfileTimeline, Tabs/index.tsx, ProfileSearchBar, QuickZapSwitch
Hooks	useBtcUsdRate.ts, useRelayConnectionRows.ts
Junk	src/services/Untitled

Note: useProfileTimeline hook and ExploreRelayDirectory remain in use; only dead wrappers were removed.

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Fix 7 — YouTube iframe API poll timeout

File: src/lib/youtube-iframe-api.ts

Problem: When the YouTube script tag was already present but YT.Player never became available, requestAnimationFrame polled forever.

Fix: Cap polling (e.g. 5s / ~300 frames). Resolve the promise anyway so embeds fail gracefully instead of leaking rAF work.

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Verification

After applying all fixes:

npm run test -- --run src/lib/profile-author-warmup-spec.test.ts src/components/PostEditor/PostTextarea/Mention/mention-range.test.ts
npx tsc --noEmit

Manual checks:

1. Home feed scroll — no jank spike when many authors are visible.
2. @-mention search — still finds cached profiles after IDB cap.
3. YouTube embeds — still load when API is healthy; no infinite rAF when blocked.

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Phase 2 — Archives API was additive, not a replacement (2026-06-07)

Why it still felt sluggish: Nostr Archives REST was wired in parallel with relays for profiles/search, but feed note stats still fired full relay REQ waves for every visible card even when Archives already had interaction counts. Archives also consumed the shared 100 req/min budget via sequential interaction prefetch, while relay work continued unchanged.

Fix A — Feed cards: Archives-only stats

File: src/components/NoteStats/index.tsx

Background feed cards (!foregroundStats) now call prefetchArchivesInteractions only. Relay fetchNoteStats runs on foreground surfaces (open note, thread, interactions panel).

Fix B — Parallel Archives interaction prefetch

File: src/lib/note-stats-archives-prefetch.ts

Prefetch runs with concurrency 5 instead of one note at a time.

Fix C — Archives-first profile batch

File: src/lib/profile-metadata-batch.ts

Await Archives metadata (400ms cap), then relay-fetch only pubkeys Archives did not return — avoids duplicate kind-0 storms.

Fix D — Remove 120× subscribeNoteStats in NoteList

File: src/components/NoteList/index.tsx

Dropped per-visible-note stats subscriptions that re-triggered profile batches on every Archives count update.

Fix E — Stabilize superchat filter

File: src/components/NoteList/index.tsx

feedAttestedSuperchatIds read from a ref inside shouldHideEvent so attestation updates do not rescan 2500 rows.

Fix F — Cap Archives blocking on thread resolve

File: src/lib/thread-context-local.ts

Archives event lookup races with a 700ms cap before falling through to local stores / relays.

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Related audit items (not in this pass)

Area	Notes
DeepBrowsingProvider + Tabs	Scroll updates context → tab chrome re-renders
NostrProvider	Account hydration causes broad tree updates
useFeedAttestedSuperchatIds	New attestations invalidate shouldHideEvent → full feed re-scan
NoteList stats subscriptions	Up to ~120 subscribeNoteStats listeners
RssFeedList	20s IndexedDB poll while mounted
client.service	45s HTTP timeline polling on index relays
Knip unused exports	Mostly shadcn re-exports; low priority

The while (true) worker pool in client.service.ts (~line 390) is intentional and bounded.