List-view grouping is server-side: group set and per-group counts come from an aggregate query, rows within a group are paged (objectui#7189 ruling A)

[os-project-manager]

Filed by the director seat (objectstack #12708, summon #8, session session_01ShyhexkB2d1AeRZ85tgAAe) to carry a maintainer ruling into the spec lane. Filed unassigned; domain:spec and pm:queue set because the ruling names the lane. objectui#7189 is pm:blocked on this card.

The ruling this card implements

Provenance (who / verbatim / where): maintainer, live PM chat with the director seat, 2026-09-02, replying to decision batch #7 in which objectui#7189 was item 1 with the recommendation B (fetch the whole filtered set within the platform ceiling) and A (server-side grouping) offered as the fallback. Verbatim reply: 「7189 A 其他同意」 — the maintainer takes A over the recommendation.

Ruled: A. Grouping on a list view (the grid) is server-side. The set of groups and every number in a group header (the count and any per-group aggregation) are properties of the query, not of the fetched page. Rows inside a group are paged. The client-side grouping of the fetched page that packages/plugin-grid/src/useGroupedData.ts performs today is the interim state, not the contract.

Measured facts the ruling rests on (all from objectui#7189 and its landing note, comment 5496459435)

• A grid grouped by a lookup over 186 rows in five units with $top: 100 renders two group headers (86, 14) with three units absent when rows are contiguous, and five headers reading 31/31/30/1/7 when interleaved. Which shape appears depends on row order. Neither is the data.
• ObjectGrid.tsx computes useServerPagination = !hasInlineData && !isGrouped, so a grouped grid that owns its fetch has no server pager at all: its pager pages groups in memory over the rows already loaded. Records past the first window are not on page 2. They are unreachable from that screen.
• The platform already groups the same field over the same data with true totals through the dataset engine (the same application's dashboard does it). The capability exists; the grid surface lacks it.
• The disclosure half landed in objectui PR examples/app-todo: is_completed and is_overdue are readonly flags that nothing ever maintains — permanently false, and one of them is read by a hook #7226 (a "Partial" marker beside every group count). It is honest and it tells the reader about rows they cannot reach. Disclosure is a ceiling here, not a floor.

Scope, three halves in order

1. Spec (this card's first half). Define what grouping on a list view means and what the platform returns for it: the group keys, the per-group total count, the per-group aggregations (the same aggregation vocabulary datasets already use, one vocabulary and not two, per objectui#4576), and the paging model for rows within a group. Whether this is a new query shape on the data endpoint or a reuse of the dataset aggregate query is the spec seat's design call. An ADR if the contract is new. Clause ② yes.
2. Platform. The group query on the REST and ObjectQL path, reusing the dataset aggregate engine: group-by over plain and lookup fields, total per group, a row page per group. Blocked-by the spec half.
3. objectui (plugin-grid). Grouped mode consumes group headers from the server; useGroupedData stops grouping the page; the grouped exclusion in useServerPagination goes; the "Partial" marker from PR examples/app-todo: is_completed and is_overdue are readonly flags that nothing ever maintains — permanently false, and one of them is read by a hook #7226 is retired once counts are server-true (enforce-or-remove); the "Grouping is page-scoped" docs section written under chore(deps)(deps-dev): bump the development-dependencies group across 1 directory with 5 updates #7189 is rewritten. Blocked-by the platform half. Tracked on objectui#7189.

Not in scope

• The unbounded fetch on gantt, calendar, map and tree: ruled a′ on objectui#7210 (platform ceiling constant plus a loud footnote) and dispatched separately.
• Any change to dashboard datasets.

Acceptance

• The 186-row, five-unit, $top: 100 fixture renders five group headers with counts 86/61/31/7/1 regardless of row order, and opening the 86-row group pages its rows.
• No "Partial" marker renders when counts are server-true.
• A grouped grid with more rows than one window can reach every row through the UI.

Related: objectui#7189 (origin; the ruling is recorded there) · objectui#7210 · objectui PR #7226 · objectui#7179 · objectstack #12708 (director seat ledger).