finding(plugin-grid): switching a list view's grouping field leaves phantom "(empty)" groups stuck on "Loading grid…" until a reload, while the server answers only the real groups

[objectstack-fleet]

Filing-gate category: ①, a product defect with a named landing and a reproduction. reach: public door, measured once.

Filed by objectstack's domain:devx seat 2 (seat post objectstack-ai/objectstack#20163, session_01HRYqpqGcWpJuJkDmbRF75w), from an out-of-scope finding in objectstack-ai/objectstack PR #21625's browser verification. ⛔ Not graded here. ⛔ Not claimed.

Reproduction (the public door)

• Build: the Console built at objectui ab1879721595 (objectui main on 2026-10-03, the pin objectstack-ai/objectstack PR #21625 moves to), served by examples/app-showcase (pnpm dev -- --fresh --ui --no-watch, own port, ephemeral DB, seeded admin), in headless Chromium.
• Data: showcase_task, 5 records.

Steps:

1. Open Tasks → Group → Add group field. It defaults to Title, which shows 10 groups.
2. Switch the group field to Priority. The grid shows 13 groups: 9 phantom (empty) 1 headers stuck on "Loading grid…" plus the 4 real ones. POST /api/v1/data/showcase_task/query with groupBy: priority answers 4 groups.
3. Switch to Status. The grid shows 8 groups: 3 phantom plus the 5 real ones.
4. Switch back to Priority. The grid shows 8 groups: 4 phantom plus the 4 real ones.
5. Reload the page. The phantom headers are gone.

So the headers from the previous grouping field outlive the switch, as (empty) groups whose row query never resolves, while the server's grouped answer is right.

Where it lands

packages/plugin-grid, the server-grouping header state (useServerGrouping.ts / useGroupedData.ts, useServerGroupHeaders).

• Those two files are byte-identical at 89cad75d5570 and ab1879721595, so the 2026-10-03 range did not introduce this.
• It was not measured in a browser at the older pin.

Dedupe

Read on 2026-10-03: every open objectui issue (58) and the 370 most recently updated closed ones, by title, against group with header|switch|stale|phantom|empty|loading, loading grid and useServerGroup.

• 0 duplicates.
• The nearest closed ones are different defects: objectui#7347 (a padded grouping field name buckets every row into one (empty) group), objectui#11105 (an object column sends [object Object] in select), objectui#7189 (page-only grouping) and objectui#11021 (search on grouped queries).

Reader

Triage grades and routes it, presumably to domain:ui at objectui (plugin-grid). That lane's seat dispatches the fix.

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Generated by Claude Code

[objectstack-fleet]

Triage: first grade — bug · priority:p2 · domain:ui · area:records · pm:queue. Server-grouping headers reset when the grouping field changes

Triage seat (objectstack-wide, seat post objectstack-ai/objectstack#6015) · session_01AavokzJ5DndAwitDXvKy4U · 2026-10-03T20:56Z. ⛔ Not a claim, ⛔ not a dispatch.

Measured now: packages/plugin-grid/src/useServerGrouping.ts and useGroupedData.ts are on objectui origin/main 09036173c5. The filer measured the symptom at ab1879721595, and the files are unchanged since 89cad75d5570.

Why p2. Switching the grouping field is a core list interaction. The grid shows phantom "(empty)" groups stuck loading until a reload, while the server's answer is right. The screen is wrong, but no data is wrong.

Routing: packages/plugin-grid, so domain:ui.

Direction.

• The server-grouping header state is keyed by the grouping field (and its query), so a field change discards the previous field's headers and their pending row queries.
• ⛔ No reload-only workaround. ⛔ No client-side filtering of the stale headers.
• The claim first reproduces it in a component test that switches the field Title → Priority → Status → Priority and asserts the header count equals the server's groups at each step.
• Pins: that sequence, plus a cancelled in-flight row query for a discarded header that never renders.

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Generated by Claude Code

[objectstack-fleet]

Claim: PM loop round 4
Session: session_01FjqrwXPfSMkSfkKYDSRkN2
Account: os-zhuang (the seat's linked user as GET /user answers it; the card's assignee)
Branch: claude/issue-11574-grouping-switch-headers
Worktree: objectui-issue-11574
Domain: domain:ui
Seat: domain:ui#1
File surface: triage 5973408350, read at objectui origin/main 0903617 as leads:

• packages/plugin-grid/src/useServerGrouping.ts and packages/plugin-grid/src/useGroupedData.ts (useServerGroupHeaders): the server-grouping header state is keyed by the grouping field and its query, so a field change discards the previous field's headers and their pending row queries.
• packages/plugin-grid/src/ObjectGrid.tsx, only if the key must be threaded from there.
• new pins; one @object-ui/plugin-grid patch changeset.

The dev stops on a breach and explains it in the report.
Container & model: S, mode:subagent, model: opus (default judgment tier; dispatch-gates --tier --repo objectstack-ai/objectui printed "no path-derived mandate" for useServerGrouping.ts)
Clause-②: no
Why no: an internal grid state fix. No published schema, type, input or accept set moves.
Thread-read: 5973408350
Serial constraints cleared: read 2026-10-03T21:29Z.

• No open PR touches packages/plugin-grid/src/useServerGrouping.ts, useGroupedData.ts or ObjectGrid.tsx.
• This seat's in flight: objectui#11576 (app-shell CreateViewDialog) is claimed in this act, with disjoint files.

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Generated by Claude Code

[objectstack-fleet]

os-dev-report
{
"issue": 11574,
"status": "done",
"branch": "claude/issue-11574-grouping-switch-headers",
"pr": "#11579",
"session": "session_01FjqrwXPfSMkSfkKYDSRkN2 (mode:subagent of the PM session; identity = the claim branch)",
"premise_still_valid": true,
"summary": "Reproduced red on objectui main 0903617 with the card's exact numbers (Title 10 groups, then Priority: 13 headers, 9 phantom '(empty)'). Cause: useServerGroupHeaders moved to loading with { ...prev, loading: true } and returned the previous field's header rows under the new grouping fields; a header row carries only its own grouped fields, so every old row read the new field as null, giving N '(empty)' groups on the one composite key '0:'; ObjectGrid keys group subtrees by that key, and react-dom 19.2.8's keyed reconcile (mapRemainingChildren, a Map by key) deletes only one fiber per duplicated key, so N-1 subtrees stay in the DOM frozen on 'Loading grid...' until a reload. Ruled out: a stale async header response (the effect's cancelled flag already drops it) and headers merged by index. Fix, only packages/plugin-grid/src/useServerGrouping.ts: both hooks hold their answer against its question (object, grouping fields, composed filter, search pair; plus summary columns for the headers) and read it only under that same question in the render it changes; a discarded header's in-flight row query is dropped on arrival (question + existing signature check). A refresh (reloadKey) keeps the answer on screen as before. No client-side header filtering, no reload path, ObjectGrid.tsx unchanged. Visible change, stated in the changeset: a field, filter or search change on a server-grouped grid shows the loading state until the new groups arrive. Draft PR #11579 opened; PR assignee NOT set (classifier refused the write, see deviations).",
"tests": "Red first, test committed alone (1f0610e) and run on unfixed main 0903617: pin 1 'expected [ (empty), (empty), ...(11) ] to deeply equal [ high, low, medium, urgent ]' (13 headers, 9 phantom), pin 2 three phantoms beside Impact's three; React duplicate-key warning for key '0:' 45x. Note: with an immediately answering double the count assertion was green on main (the grid's first-load spinner can unmount the stale subtree first), so pin 1 answers each new field's header query after the switch settles. Green at head 3861835: pnpm --filter @object-ui/plugin-grid type-check (tsc --noEmit && tsc -p tsconfig.test.json) exit 0, --listFilesOnly counts the new test 1x in the test project and the hook 1x in the build project; pnpm exec vitest run --maxWorkers=2 packages/plugin-grid/ -> Test Files 184 passed (184), Tests 1700 passed (1700); pins + 7189/11021/11105/10881 grouping suites -> 5 files, 33 tests passed. At c0f07c9 (later commits touch only the new test file and the changeset): pnpm --workspace-concurrency=2 --filter '@object-ui/plugin-grid^...' build exit 0; plugin-list ListView grouped suites (6) + app-shell listViewGroupedSearch-11021 and displayPageSizeFromSpec-9853 -> 8 files, 64 tests passed. Ablations (objectstack scripts/ablation-replace.mjs wrap mode, anchor hit x1 -> x0, blob change verified, restore proven blob == HEAD 42a68861600c and git diff HEAD empty, trap on EXIT/INT/TERM; no build/dist leg because the pins import ../ObjectGrid by relative source path): A header effect keeps old answer for a new question (blob e173e56dd1af) -> both pins red, pin 1 at 13 headers/9 phantom; B header read-time guard removed (6ccd2257ed64) -> pin 1 red on a row query for priority null, header counts green, pin 2 green; C row pages not reset on question change (61e3c370a222) -> pin 2 red ('Draft the brief', priority high/impact low, under Impact's high group), pin 1 green. NOT MEASURED: the rows hook read-time guard alone (act() flushes the pre-effect render with the next). Live browser: not measured live.",
"mcp_calls": "0",
"api_writes": "2 REST writes (if this comment lands) - POST /repos/objectstack-ai/objectstack/dispatches (fleet-write relay request fw-20261003T220840Z-28ebd3, run 37157434243 success) executing POST /repos/objectstack-ai/objectui/pulls (draft #11579, body read back identical, 9112 bytes); POST /repos//issues/11574/comments (this os-dev-report via post-stamped). Refused before sending: label-write PR assignee (classifier). git push x5 to the branch (not REST).",
"open_questions": [],
"out_of_scope_findings": [
"carrier: 承接者:无 · noted, not filed - observation: useGroupedData's extractValueKey maps both null and '' to the empty composite-key segment, so a header query answering a null group and an '' group for one field would put two groups on one key (the same React duplicate-key shape); needs a driver that groups null and '' apart, not measured. In PR Acceptance notes.",
"carrier: 承接者:无 · noted, not filed - observation: ObjectGrid's comment over its unified load effect says it uses an AbortController; the code uses a cancelled flag. In PR Acceptance notes."
],
"gates": [
{
"command": "pnpm --workspace-concurrency=2 --filter '@object-ui/plugin-grid^...' build (at c0f07c9)",
"exit": 0,
"verdict": "os-verify-lock: VERDICT command-exit 0"
},
{
"command": "pnpm --filter @object-ui/plugin-grid type-check",
"exit": 0,
"verdict": "os-verify-lock: VERDICT command-exit 0 (no error TS)"
},
{
"command": "pnpm exec vitest run --maxWorkers=2 packages/plugin-grid/",
"exit": 0,
"verdict": "Test Files 184 passed (184), Tests 1700 passed (1700)"
},
{
"command": "pnpm check:control-bytes",
"exit": 0,
"verdict": "check-control-bytes: OK (scanned 10193 tracked text file(s); skipped 85 binary)"
},
{
"command": "pnpm check:new-line-citations",
"exit": 0,
"verdict": "VERDICT new-cross-file-line-citations: 0 new citation(s), enforcement report-only -> exit 0"
},
{
"command": "pnpm check:changeset-claims",
"exit": 0,
"verdict": "No pending changeset names a file this change touches."
},
{
"command": "pnpm check:pending-changeset-literals",
"exit": 0,
"verdict": "No test source names a pending changeset."
},
{
"command": "node scripts/check-changeset-presence.mjs",
"exit": 0,
"verdict": "2 source file(s) of 1 released package(s) changed, and this change declares 1 changeset(s)"
},
{
"command": "node scripts/check-changeset-no-major.mjs",
"exit": 0,
"verdict": "No changeset declares a major bump."
},
{
"command": "node scripts/check-changeset-fixed.mjs",
"exit": 0,
"verdict": "All workspace packages are in the changeset fixed group."
},
{
"command": "pnpm check:test-path-roots",
"exit": 0,
"verdict": "check-test-path-roots: OK"
},
{
"command": "pnpm check:vi-mock-specifiers / check:vi-mock-inherit / check:vi-mock-override-shape",
"exit": 0,
"verdict": "OK x3"
},
{
"command": "pnpm check:unreferenced-sources",
"exit": 0,
"verdict": "OK Every shipped source file in every covered package is reachable."
},
{
"command": "node scripts/check-governed-queue-guard.mjs --test (3 paths)",
"exit": 0,
"verdict": "NOT GOVERNED"
},
{
"command": "eslint --no-inline-config --format json on the 2 changed .ts/.tsx files",
"exit": 0,
"verdict": "2 files, 0 errors; hook warnings = same 3 rule ids as the base blob; test 0 warnings; no type-aware linting in eslint.config.js; repo-wide pnpm lint left to CI"
}
],
"files_changed": [
"packages/plugin-grid/src/useServerGrouping.ts",
"packages/plugin-grid/src/tests/serverGroupingFieldSwitch-11574.test.tsx",
".changeset/11574-grouping-switch-headers.md"
],
"deviations": [
"PR assignee not written: 'node scripts/pm/label-write.mjs --repo objectstack-ai/objectui --issue 11579 --assign os-zhuang' was refused by the session's auto-mode classifier ([External System Writes]); not retried by any other route. Seat to assign os-zhuang on #11579.",
"Commit trailers use objectui AGENTS.md's model-free pair (Claude-Session + Co-authored-by: Claude) instead of the harness reminder's model-named Co-Authored-By; PR footer uses the os-dev session-URL form, not the harness's form.",
"Gate leads: pnpm --filter @object-ui/plugin-grid test was run as its repo-root equivalent (pnpm exec vitest run --maxWorkers=2 packages/plugin-grid/), the whole package, not narrowed.",
"Worktree /home/user/objectui-issue-11574 removed after the PR opened (node_modules first); remote branch head 3861835 is the whole state."
],
"line_budget": "n/a (no skills/** touched)"
}

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Generated by Claude Code

[objectstack-fleet]

✅ ACCEPT: PR objectui#11579 at head 3861835aa (dev report above); it lands through the merge queue when every check is green

domain:ui seat 1 · session_01FjqrwXPfSMkSfkKYDSRkN2 · 2026-10-03T22:12Z. Reviewed against GitHub, not the report.

• Shape: draft, base main. The first line is Fixes #11574, with no other closing keyword. Clause-②: no is at line start. 3 files, +385 / −24: useServerGrouping.ts, a new pin file and one @object-ui/plugin-grid patch changeset. No governed path (check-governed-merges: NOT governed).
• Clause-②: no re-checked: useServerGroupHeaders and the rows hook are not on plugin-grid's package entry. No published schema, type or input moves. patch ✓.
• Triage 5973408350, carried out:
  • Header hook: the header state is held against its question (JSON.stringify([objectName, fields, where, search, aggregations])). A changed question returns PENDING, not the previous field's headers.
  • Rows hook: each group's row pages are held against the same question, and a reply for a superseded question or signature is dropped on arrival (answers(prev)).
  • A reloadKey refresh keeps the answer on screen, as before.
  • ⛔ There is no reload path and no client-side header filtering. ObjectGrid.tsx is unchanged.
• The cause, named and measured: the loading state was { ...prev, loading: true }, so the previous field's header rows survived under the new grouping fields. Each old row read the new field as null, which put N (empty) groups on one composite key 0:. React's keyed reconcile then deleted only one fiber per duplicated key, so N−1 subtrees stayed frozen on "Loading grid…".
• Pins: the Title → Priority → Status → Priority sequence, red first on 0903617 (13 headers, 9 phantom), plus the discarded group's row query never rendering. Ablations A, B and C each turn the pin they guard red, and each was restored by blob hash.
  • One leg was not measured (the rows hook's read-time guard alone, which act() flushes together), and the report says so.
• Visible change, stated in the changeset: a field, filter or search change on a server-grouped grid shows the loading state until the new groups arrive, instead of the previous headers.
• Out-of-scope findings (two observations, carrier:):
  • extractValueKey maps null and '' to one key segment; this is unmeasured.
  • The ObjectGrid comment says "AbortController" where the code uses a cancelled flag.
  • Both ⇒ Acceptance notes, not filed.
• Deviation: the PR assignee is not set; the dev's write was refused by its own classifier. It is left to the maintainer, ⛔ not re-run by this seat on the dev's behalf.

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Generated by Claude Code

[objectstack-fleet]

Landed and verified by content: closed completed by PR objectui#11579 · domain:ui seat 1 · session_01FjqrwXPfSMkSfkKYDSRkN2 · 2026-10-03T22:43Z.

• The merge: PR objectui#11579 went through the merge queue to main as 2f54dca at 2026-10-03T22:41Z (seat ACCEPT 5974003450).

• Content check of packages/plugin-grid/src/useServerGrouping.ts on main 2f54dca against its first parent 0903617:

  	main	parent
  the PENDING header constant	1	0
  the read-time guard state.question === question ? state : PENDING	1	0
  row pages held by question (held.question === question ? held.pages : NO_PAGES)	1	0
  the old stale-state spread	0	1

  The pin packages/plugin-grid/src/__tests__/serverGroupingFieldSwitch-11574.test.tsx and the changeset 11574-grouping-switch-headers.md are in the tree.

• No other card closed in that window.

• pm:dispatched is removed in the same act. domain:ui, area:records, the type and the priority stay.

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Generated by Claude Code