Performance

Performance

Performance is UX. In Nevermind, every millisecond affects trust because the product is a keyboard-first command palette. Treat perceived latency, input responsiveness, and visual stability as product requirements, not polish.

How to use this skill

1. Explore before assuming. Identify the exact interaction path: renderer input → IPC → main/provider work → cache/revalidation → render/update.
2. Turn on local traces. Debug performance marks are dev-gated by default. In the renderer, use localStorage.setItem('nvm.debugPerformance', 'true') if needed and tune noisy logs with localStorage.setItem('nvm.debugPerformance.slowMs', '16'). In main/CLI runs, use NVM_DEBUG_PERFORMANCE=1 and optionally NVM_DEBUG_PERFORMANCE_SLOW_MS=16.
3. Read the logs before fixing. Use mise exec -- pnpm logs:tail or inspect the app log for performance.measure entries. Compare paired layers such as search.renderer-to-results, ipc.actions:search, search.actions, extension.search.provider, root-actions.to-command-items, app.commit, view-action.ipc, ipc.palette:hide, and palette-window.show to locate where time is spent.
4. Separate perceived and actual latency. Prefer showing cached/snapshot data immediately, hydrating expensive details later, and refreshing in place.
5. Find the blocking edge. Look for synchronous CPU, awaited fanout, repeated IPC, re-render storms, layout reads/writes, heavy serialization, filesystem/native calls, and broad cache invalidation.
6. Fix the disease, then re-measure. Prefer no-op guards, in-flight dedupe, request coalescing, stale-result drops, memoization, and lazy hydration before architectural rewrites. Confirm the same performance.measure names improve instead of adding unrelated patches.
7. Verify with the closest real flow. Use mise exec -- pnpm typecheck and mise exec -- pnpm test for safety; manually dogfood UI changes when render/input feel matters.

Hot paths to inspect first

• Root search: src/app/palette/use-search-results.ts, src/app/electron/main.ts search/provider fanout, ranking, cache invalidation.
• Input/rendering: src/app/palette/App.tsx, src/app/palette/filtering.ts, src/app/palette/ui.tsx, src/app/palette/extension-view.tsx.
• Chat streaming: src/app/palette/use-ai-chat.ts, markdown rendering in src/app/palette/App.tsx, AI event forwarding in src/app/electron/ai.ts and src/app/electron/main.ts.
• Native/Electron work: src/app/electron/palette-window.ts, app icons, thumbnails, clipboard polling, filesystem scans, logging.
• Extension API surfaces: src/app/resources/nevermind-extension-api.d.ts when fixing missing primitives rather than bypassing extension APIs.

Rules

• Input must stay responsive. Never add work to keystroke paths without debounce, cancellation, coalescing, or a hard cap.
• Do not await decoration. Icons, thumbnails, previews, and metadata should hydrate after primary results appear.
• Drop stale work. Search, selection previews, and chat/UI patches must ignore old results when the active query/view/selection changed.
• Batch streams. Token-by-token AI updates should be coalesced to animation frames or similarly bounded render cadence.
• No broad invalidation by default. Invalidate the smallest provider/cache/view possible; broad root invalidation is a smell unless the data truly affects all roots.
• Treat polling and refresh as lifecycle ownership problems. For laggy extension views, audit renderer-held action tokens, IPC clone-safety, staleness, in-flight dedupe, and host-owned refresh primitives before suppressing repeated errors.
• Avoid render-time derivation loops. Memoize filtered sections/items, flattened view items, markdown nodes, and action rows when they depend on stable inputs.
• Prevent avoidable re-renders. Keep state as local as possible, split components around independent update frequencies, stabilize callbacks/props passed to large lists, and avoid rebuilding arrays/objects/React nodes in parent render paths unless their inputs changed.
• Do not let selection/input churn redraw everything. Typing, arrow-key movement, chat token deltas, and hover/preview changes should update only the affected surface or row; use refs for mutable bookkeeping that does not affect paint.
• Memoize expensive presentation. Markdown, icons, accessories, action panels, filtered sections, and large list rows should be memoized or moved into memoized child components before adding more state to App.tsx.
• Guard Electron window operations. Resizing, centering, opacity changes, and IPC mode updates should no-op when state is unchanged.
• Preserve immediate dismissal. For dismissAfterRun: 'auto' native/app actions, verify ipc.palette:hide and palette-window.hide happen before slow execute/open work; enqueue hide before execute IPC and defer native launch work out of the current IPC turn when needed.
• Treat native calls as expensive. nativeImage, file-icon, clipboard image conversion, filesystem scans, and log reads need caching, limits, and in-flight dedupe.
• Measure or bound. If exact measurement is hard, add conservative caps/timeouts and document the remaining risk.

Review checklist

• Does typing trigger only the minimum required IPC/provider work?
• Can older async results overwrite newer UI state?
• Does opening the palette show useful cached results immediately?
• Are expensive visual assets lazy and deduped?
• Does chat streaming re-render or re-parse more than necessary?
• Are cache invalidations scoped to the changed extension/surface?
• Are large lists filtered/rendered with memoization or caps?
• Does this state change force unrelated rows, sibling panes, markdown, or action panels to re-render?
• Are callback/array/object props stable enough for memoized children to help?
• Are window/layout operations guarded against no-op repeats?
• Do immediate-dismiss actions hide the palette before slow native/app work starts?
• Did verification cover both tests and the real UX path?