This skill builds on core, table-features, and client-vs-server. Expansion controls row-tree inclusion; the renderer owns disclosure controls and detail panels.

Setup

import {
  createExpandedRowModel,
  rowExpandingFeature,
  tableFeatures,
} from '@tanstack/table-core'

type Node = { id: string; children?: Node[] }
export const features = tableFeatures({
  rowExpandingFeature,
  expandedRowModel: createExpandedRowModel(),
})
export const options = { getSubRows: (row: Node) => row.children }

Core Patterns

const detailOptions = { getRowCanExpand: () => true }
const isDetailOpen = row.getIsExpanded()

For custom detail UI, render an additional row/panel when isDetailOpen is true.

Common Mistakes

[HIGH] Omitting the subrow accessor

Wrong: const options = { data: nestedRows }

Correct: const options = { data: nestedRows, getSubRows: (row: Node) => row.children }

Nested object structure is not inferred automatically.

Source: docs/framework/react/guide/expanding.md#table-rows-as-expanded-data

[HIGH] Expecting detail markup from state

Wrong: row.toggleExpanded(true)

Correct: if (row.getIsExpanded()) renderDetail(row.original)

Table is headless and cannot render a custom detail panel.

Source: docs/framework/react/guide/expanding.md#custom-expanding-ui

[HIGH] Misreading pagination placement

Wrong: const options = { paginateExpandedRows: false }; const leafOnlyPages = true

Correct: const options = { paginateExpandedRows: false }; const descendantsStayWithParent = true

This option controls whether expansion happens before or after pagination; it does not make page size count only leaf rows.

Source: packages/table-core/src/features/row-expanding/rowExpandingFeature.types.ts

API Discovery

Inspect node_modules/@tanstack/table-core/dist/features/row-expanding/ for expansion state, row APIs, and model placement.