TanStack Virtual and GitHub Large-Surface Virtualization

Scope

Evidence for the Slate v2 virtualization planning lane.

Sources:

• GitHub Engineering, "The uphill climb of making diff lines performant", pasted by the user on 2026-05-03.
• TanStack Virtual official docs queried through Context7 on 2026-05-03.
• Live .tmp/slate-v2 source read on 2026-05-03.
• TanStack Blog, "TanStack Virtual just got a lot faster, and finally handles iOS", published 2026-05-19 and read on 2026-05-23.
• TanStack Virtual latest Virtualizer API docs, read on 2026-05-23.

2026-05-23 TanStack Virtual Perf And iOS Update

Latest upstream facts:

• @tanstack/[email protected] depends on @tanstack/[email protected].
• The 2026-05-19 release keeps the public VirtualItem[] shape but moves the common single-lane hot path onto flat Float64Array storage with lazy VirtualItem materialization.
• resizeItem / dynamic-measurement storms are fixed by internal cache version tracking instead of cloning the whole size cache.
• iOS WebKit momentum scroll is now handled inside TanStack Virtual by deferring scroll position writes while touch/momentum/elastic overscroll is active.
• Backward-scroll jank for dynamic heights is fixed by default: above-viewport size adjustments are skipped while scrolling backward unless the consumer overrides shouldAdjustScrollPositionOnItemSizeChange.
• takeSnapshot() plus initialMeasurementsCache and initialOffset is the upstream restoration path for remounting a measured virtual list without throwing away known item sizes.

Current live Slate v2 facts on 2026-05-23:

• slate-react depends on @tanstack/react-virtual with range ^3.13.24.
• The lockfile currently resolves @tanstack/[email protected] and @tanstack/[email protected], so the latest iOS/backward-scroll/core fast-path release is not actually installed yet.
• useVirtualizedRootPlan uses the single-lane path, stable runtime-id item keys, rangeExtractor, measureElement, and Slate-owned missing-range / DOM coverage policy.
• useVirtualizedRootPlan.scrollToTopLevelIndex bypasses TanStack for layout-backed targets by calling rootElement.scrollTo(...) directly. That loses the new iOS scroll-write deferral path for that branch.

Slate decision update:

• Upgrade @tanstack/react-virtual in .tmp/slate-v2 so the lockfile reaches 3.13.25 / [email protected].
• Do not expose TanStack options in public Slate API. The existing Slate-shaped domStrategy={{ type: 'virtualized', threshold, overscan, estimatedBlockSize }} boundary remains correct.
• Do not override shouldAdjustScrollPositionOnItemSizeChange by default. The new upstream default is the behavior Slate wants for dynamic-height backward scroll.
• Keep lanes unused. Slate's top-level block virtualization wants the single-lane fast path.
• Route internal programmatic virtualized scroll writes through virtualizer.scrollToOffset / virtualizer.scrollToIndex where practical, rather than direct rootElement.scrollTo, so Slate inherits upstream iOS scroll semantics.
• Consider takeSnapshot() only as an internal remount/restoration optimization for large docs. Do not add a public Slate API until a real remount-jump problem is proven.

GitHub Diff Lessons

GitHub did not jump straight to virtualization. The sequence matters:

1. reduce repeated-unit cost first;
2. simplify component trees;
3. delegate events through a top-level handler;
4. move rare state into conditional children;
5. convert repeated lookup paths to O(1) maps;
6. use virtualization for the p95+ tail where even cheap rows are too many.

The reported shape:

• v1 diff line: many DOM nodes, React components, and event handlers.
• v2 diff line: fewer wrappers, fewer components, delegated events, less state.
• p95+ pull requests: TanStack Virtual reduced DOM/heap pressure and INP.

Slate implication:

• TanStack Virtual is good evidence for viewport range management at extreme scale.
• It is not evidence that editable rich text can make the default DOM incomplete without a selection/copy/paste/IME/a11y policy.

TanStack Virtual API Facts

TanStack Virtual provides a headless viewport range engine:

• required: count, getScrollElement, estimateSize;
• important: overscan, getItemKey, rangeExtractor, measureElement, onChange, scrollToIndex;
• dynamic height rows need data-index and virtualizer.measureElement;
• stable item keys should come from a stable item id instead of raw index when rows can reorder;
• custom range extraction can force extra indexes to stay mounted;
• window scrolling needs scrollMargin and adjusted transforms.

Slate implication:

• use runtime ids as virtual item keys;
• use measureElement for variable block heights;
• use rangeExtractor or a Slate-side corridor rule to retain caret, composition, selection, and materialization targets;
• do not leak TanStack positioning assumptions into Slate's public editor API.

Live Slate v2 Current Shape

Current live .tmp/slate-v2 source has:

• renderingStrategy public prop with full, staged, shell, and virtualized effective types;
• @tanstack/react-virtual as a slate-react runtime dependency;
• a TanStack-backed useVirtualizedRootPlan using useVirtualizer, runtime-id item keys, dynamic measurement, retained selected/promoted indexes, and coalesced missing viewport ranges;
• an experimental type: 'virtualized' option in packages/slate-react/src/rendering-strategy/create-segment-plan.ts;
• DOMCoverageReason = 'viewport-virtualization' in packages/slate-dom/src/plugin/dom-coverage.ts;
• hidden viewport-range DOMCoverageBoundary registration in packages/slate-react/src/rendering-strategy/virtualized-range-boundary.tsx;
• virtualized-mode package tests in packages/slate-react/test/rendering-strategy-and-scroll.tsx;
• a full browser example in site/examples/ts/rendering-strategy-runtime.tsx;
• docs warning that virtualized native browser find and screen-reader traversal do not cover unmounted regions until mounted.

Current gap:

• virtualization works, but its public option types, render branch, materialization handler, metrics, shell fallback, and keyboard classification are still spread through shared shell/staged rendering files;
• previewChars still appears in the virtualized option union even though viewport virtualization does not render shell previews;
• RenderingStrategySegmentShell can still register viewport-virtualization boundaries, which keeps shell and virtualized policy coupled.

Planning Decision

Use TanStack Virtual as a viewport range engine for experimental virtualized mode only. Do not let it own Slate's editor semantics, and keep the virtualized adapter visibly decoupled from shell/staged rendering internals.

The Slate-owned layers remain:

• DOMCoverageBoundary;
• materialization policy;
• model-backed copy/paste policy;
• selection import/export;
• IME and mobile guards;
• metrics and degradation classification.

The TanStack-owned layer is only:

• visible index range;
• measured item sizes;
• overscan and scroll alignment;
• optional custom retained indexes.