@@ -0,0 +1,16 @@
+---
+'@objectstack/service-analytics': patch
+---
+
+fix(service-analytics): the draft preview groups a bucketed time dimension and reads a qualified filter member as the live faces do, and the ObjectQL strategy serves a backed `RELATION.id` dimension
+
+Clause-②: yes (widening)
+Metadata-protocol: none
+
+Three answers `queryDataset` gave differently depending on the face, measured on real SQLite:
+
+- **A bucketed time dimension in the draft preview.** A `timeDimensions` entry with a `granularity` is now grouped by its bucket whether or not the member is also in `dimensions`, and the bucket is a column of the answer and of `fields` (type `time` for a `date` dimension). This is the set both live strategies project. Before, the preview grouped by `dimensions` alone: one total where the live faces answered one row per month, regions without months, and a windowed `year` bucket with no key.
+- **A filter member spelled other than its column, in the draft preview.** A `runtimeFilter` (or dataset filter) member such as `OBJECT.region`, `CUBE.region` or a dataset dimension `zone` declared over `region` is now read from the column it names, with that column's declared type, through the member resolution the live strategies use. Before, the preview matched no drafted row: `[]`, or under an `$or` only the other arm's rows, where both live faces served the rows.
+- **A backed `RELATION.id` dimension on the ObjectQL strategy.** `account.id` (with `include: ['account']`), and two dimensions through one relationship (`account.id` beside `account.name`, or the FK column `account` beside `account.name`), are now served with the native strategy's groups. Before, the strategy handed the engine a `groupBy` naming one column twice and answered `INVALID_QUERY` / 400. The engine's duplicate-column refusal is unchanged; the strategy now names each column once.
+
+Nothing is refused that was served, and no export, key, error code or status is added. The draft preview still refuses a relationship-path member (#28555).
@@ -0,0 +1,300 @@
+// Copyright (c) 2026 ObjectStack. Licensed under the Apache-2.0 license.
+
+/**
+ * [#28690, #28691, #28692] Three answers the faces of `queryDataset` gave
+ * differently, on the native strategy, the ObjectQL strategy and the draft
+ * preview, on real SQLite (the #28201 / #28258 / #28555 harness).
+ *
+ * ## What these pins hold
+ *
+ * - #28690. A `timeDimensions` entry with a granularity is grouped by its
+ *   bucket whether or not the member is also in `dimensions`, on every face,
+ *   with the bucket in `fields`. Before, the preview grouped by `dimensions`
+ *   alone: one total where the live faces answered one group per month, and
+ *   regions without months.
+ * - #28691. A `runtimeFilter` member spelled other than its column
+ *   (`OBJECT.region`, `CUBE.region`, a dataset dimension `zone` over
+ *   `region`, `OBJECT.closed_at`) is read from that column by the preview, as
+ *   both live strategies read it. Before, the preview matched no drafted row
+ *   (`[]`, or under an `$or` only the other arm's rows).
+ * - #28692. The ObjectQL strategy answers a backed `account.id` dimension, and
+ *   two dimensions through one relationship, with the native strategy's
+ *   groups. Before, it handed the engine a groupBy naming one column twice and
+ *   answered `INVALID_QUERY`.
+ */
+
+import { describe, it, expect, beforeAll, afterAll } from 'vitest';
+import { ObjectQL } from '@objectstack/objectql';
+import { SqlDriver } from '@objectstack/driver-sql';
+import { DatasetSchema } from '@objectstack/spec/ui';
+import type { AnalyticsService } from '../analytics-service.js';
+import { AnalyticsServicePlugin } from '../plugin.js';
+import { installDefaultOrganization } from './default-organization.testkit.js';
+
+const OBJECT = 'os28690_deal';
+const ACCOUNT = 'os28690_account';
+
+const ACCOUNTS = [
+  { id: 'a1', name: 'Acme' },
+  { id: 'a2', name: 'Globex' },
+] as const;
+const ROWS = [
+  { id: 'd1', region: 'amer', amount: 100, account: 'a1', closed_at: '2026-03-01T00:00:00.000Z' },
+  { id: 'd2', region: 'amer', amount: 50, account: 'a2', closed_at: '2026-04-01T00:00:00.000Z' },
+  { id: 'd3', region: 'emea', amount: 30, account: 'a1', closed_at: '2026-04-02T00:00:00.000Z' },
+] as const;
+
+const shape = {
+  label: 'Deals',
+  object: OBJECT,
+  dimensions: [
+    { name: 'region', field: 'region', type: 'string' },
+    { name: 'closed_at', field: 'closed_at', type: 'date' },
+    { name: 'zone', field: 'region', type: 'string' },
+  ],
+  measures: [{ name: 'total', aggregate: 'sum', field: 'amount' }],
+};
+/** Declares no relationship. */
+const UNBACKED = DatasetSchema.parse({ name: 'os28690_deals', ...shape });
+/** Declares `account`. */
+const BACKED = DatasetSchema.parse({ name: 'os28690_deals_by_account', include: ['account'], ...shape });
+
+type Face = 'native' | 'objectql' | 'preview';
+const FACES: readonly Face[] = ['native', 'objectql', 'preview'];
+const LIVE: readonly Face[] = ['native', 'objectql'];
+
+const quiet = { debug() {}, info() {}, warn() {}, error() {}, trace() {}, fatal() {}, child() { return quiet; } };
+
+type Selection = {
+  dimensions?: string[];
+  measures: string[];
+  runtimeFilter?: Record<string, unknown>;
+  timeDimensions?: Array<Record<string, unknown>>;
+};
+type Answer = { rows: Array<Record<string, unknown>>; fields: string[] };
+
+/** A `'protocol'` service answering one pending seed draft, which routes `previewDrafts` onto the preview path. */
+const pendingSeedProtocol = {
+  getMetaItems: async () => [{ name: 'os28690_seed', object: OBJECT }],
+  getMetaItem: async () => ({ item: { records: ROWS } }),
+};
+
+describe('[#28690–#28692] time-dimension buckets, column-spelled filter members and FK-id groups on every face', () => {
+  let engine: ObjectQL;
+  const services: Partial<Record<'native' | 'objectql', AnalyticsService>> = {};
+
+  const ask = (face: Face, dataset: typeof UNBACKED, selection: Selection) =>
+    services[face === 'preview' ? 'objectql' : face]!.queryDataset(
+      dataset,
+      { ...selection } as never,
+      undefined,
+      face === 'preview' ? { previewDrafts: true } : undefined,
+    );
+
+  /** One face's rows (measures as numbers, sorted) and its `fields` as `name:type`. */
+  const answerOf = async (face: Face, dataset: typeof UNBACKED, selection: Selection): Promise<Answer> => {
+    const result = await ask(face, dataset, selection);
+    const rows = (result.rows as Array<Record<string, unknown>>)
+      .map((r) => ({ ...r, total: Number(r.total) }))
+      .sort((a, b) => JSON.stringify(a).localeCompare(JSON.stringify(b)));
+    return { rows, fields: (result.fields ?? []).map((f: { name: string; type: string }) => `${f.name}:${f.type}`) };
+  };
+
+  /** Every face in `faces` answers `expected`, rows and fields alike. */
+  const answeredAlike = async (faces: readonly Face[], dataset: typeof UNBACKED, selection: Selection, expected: Answer) => {
+    for (const face of faces) {
+      expect(await answerOf(face, dataset, selection), face).toEqual(expected);
+    }
+  };
+
+  beforeAll(async () => {
+    const driver = new SqlDriver({ client: 'better-sqlite3', connection: { filename: ':memory:' }, useNullAsDefault: true } as never);
+    engine = new ObjectQL({ logger: quiet } as never);
+    engine.registerDriver(driver as never, true);
+    await engine.init();
+    engine.registry.registerObject({
+      name: ACCOUNT,
+      label: 'Account',
+      fields: { name: { name: 'name', type: 'text' } },
+    } as never);
+    engine.registry.registerObject({
+      name: OBJECT,
+      label: 'Deal',
+      fields: {
+        region: { name: 'region', type: 'text' },
+        amount: { name: 'amount', type: 'number' },
+        closed_at: { name: 'closed_at', type: 'datetime' },
+        account: { name: 'account', type: 'lookup', reference: ACCOUNT },
+      },
+    } as never);
+    await engine.syncSchemas();
+    await installDefaultOrganization(engine as never);
+    for (const row of ACCOUNTS) await engine.insert(ACCOUNT, { ...row } as never);
+    for (const row of ROWS) await engine.insert(OBJECT, { ...row } as never);
+
+    for (const [face, caps] of [
+      ['native', undefined],
+      ['objectql', () => ({ nativeSql: false, objectqlAggregate: true, inMemory: false })],
+    ] as const) {
+      const registered: Record<string, unknown> = {};
+      const provided: Record<string, unknown> = { data: engine, protocol: pendingSeedProtocol };
+      await new AnalyticsServicePlugin({ ...(caps ? { queryCapabilities: caps } : {}) } as never).init({
+        getService: (name: string) => provided[name] ?? registered[name],
+        registerService: (name: string, svc: unknown) => { registered[name] = svc; },
+        replaceService: (name: string, svc: unknown) => { registered[name] = svc; },
+        hook: () => {},
+        logger: quiet,
+      } as never);
+      services[face] = registered.analytics as AnalyticsService;
+    }
+  });
+
+  afterAll(async () => {
+    try { await engine?.destroy(); } catch { /* noop */ }
+  });
+
+  describe('#28690 — a bucketed time dimension is grouped whether or not it is also a dimension', () => {
+    it('groups by month with no dimensions, where the preview answered one total', async () => {
+      await answeredAlike(FACES, UNBACKED, { measures: ['total'], timeDimensions: [{ dimension: 'closed_at', granularity: 'month' }] }, {
+        rows: [{ closed_at: '2026-03', total: 100 }, { closed_at: '2026-04', total: 80 }],
+        fields: ['closed_at:time', 'total:number'],
+      });
+    });
+
+    it('groups by region and month, where the preview grouped by region alone', async () => {
+      await answeredAlike(
+        FACES,
+        UNBACKED,
+        { dimensions: ['region'], measures: ['total'], timeDimensions: [{ dimension: 'closed_at', granularity: 'month' }] },
+        {
+          rows: [
+            { region: 'amer', closed_at: '2026-03', total: 100 },
+            { region: 'amer', closed_at: '2026-04', total: 50 },
+            { region: 'emea', closed_at: '2026-04', total: 30 },
+          ],
+          fields: ['region:string', 'closed_at:time', 'total:number'],
+        },
+      );
+    });
+
+    it('keys an OBJECT-qualified time dimension by its spelling, as the live faces do', async () => {
+      const member = `${OBJECT}.closed_at`;
+      await answeredAlike(FACES, UNBACKED, { measures: ['total'], timeDimensions: [{ dimension: member, granularity: 'month' }] }, {
+        rows: [{ [member]: '2026-03', total: 100 }, { [member]: '2026-04', total: 80 }],
+        fields: [`${member}:time`, 'total:number'],
+      });
+    });
+
+    it('buckets a windowed year, where the preview answered the total with no key', async () => {
+      await answeredAlike(
+        FACES,
+        UNBACKED,
+        { measures: ['total'], timeDimensions: [{ dimension: 'closed_at', granularity: 'year', dateRange: ['2026-04-01', '2026-04-30'] }] },
+        { rows: [{ closed_at: '2026', total: 80 }], fields: ['closed_at:time', 'total:number'] },
+      );
+    });
+
+    it('still projects nothing for a time dimension with no granularity (a window only)', async () => {
+      await answeredAlike(
+        FACES,
+        UNBACKED,
+        { measures: ['total'], timeDimensions: [{ dimension: 'closed_at', dateRange: ['2026-04-01', '2026-04-30'] }] },
+        { rows: [{ total: 80 }], fields: ['total:number'] },
+      );
+    });
+  });
+
+  describe('#28691 — a filter member spelled other than its column is read from that column', () => {
+    const emeaOnly: Answer = { rows: [{ region: 'emea', total: 30 }], fields: ['region:string', 'total:number'] };
+    const amerAprilAndEmea: Answer = {
+      rows: [{ region: 'amer', total: 50 }, { region: 'emea', total: 30 }],
+      fields: ['region:string', 'total:number'],
+    };
+
+    it.each([
+      ['OBJECT.region', `${OBJECT}.region`],
+      ['CUBE.region', `${UNBACKED.name}.region`],
+      ['the dimension zone over region', 'zone'],
+    ])('matches %s, where the preview answered []', async (_label, member) => {
+      await answeredAlike(FACES, UNBACKED, { dimensions: ['region'], measures: ['total'], runtimeFilter: { [member]: 'emea' } }, emeaOnly);
+    });
+
+    it("matches OBJECT.region's arm under an $or, where the preview answered only the other arm's rows", async () => {
+      await answeredAlike(
+        FACES,
+        UNBACKED,
+        { dimensions: ['region'], measures: ['total'], runtimeFilter: { $or: [{ [`${OBJECT}.region`]: { $in: ['emea'] } }, { amount: 50 }] } },
+        amerAprilAndEmea,
+      );
+    });
+
+    it('reads an OBJECT-qualified datetime member as the datetime column, where the preview answered []', async () => {
+      await answeredAlike(
+        FACES,
+        UNBACKED,
+        { dimensions: ['region'], measures: ['total'], runtimeFilter: { [`${OBJECT}.closed_at`]: { $gte: '2026-04-01' } } },
+        amerAprilAndEmea,
+      );
+    });
+
+    it("compares an OBJECT-qualified datetime member's instants, as the column's declaration reads them", async () => {
+      // 2026-04-02T01:00+02:00 is 2026-04-01T23:00Z, so d3 (2026-04-02T00:00Z)
+      // is after it. Compared as text, as an undeclared column would be, it is not.
+      await answeredAlike(
+        FACES,
+        UNBACKED,
+        { dimensions: ['region'], measures: ['total'], runtimeFilter: { [`${OBJECT}.closed_at`]: { $gte: '2026-04-02T01:00:00+02:00' } } },
+        { rows: [{ region: 'emea', total: 30 }], fields: ['region:string', 'total:number'] },
+      );
+    });
+
+    it('filters on zone beside a time-dimension-only bucket', async () => {
+      await answeredAlike(
+        FACES,
+        UNBACKED,
+        { measures: ['total'], timeDimensions: [{ dimension: 'closed_at', granularity: 'month' }], runtimeFilter: { zone: 'amer' } },
+        { rows: [{ closed_at: '2026-03', total: 100 }, { closed_at: '2026-04', total: 50 }], fields: ['closed_at:time', 'total:number'] },
+      );
+    });
+  });
+
+  describe('#28692 — the ObjectQL strategy groups a backed FK path once', () => {
+    it("serves a backed 'account.id' with the native strategy's groups, where it answered INVALID_QUERY", async () => {
+      await answeredAlike(LIVE, BACKED, { dimensions: ['account.id'], measures: ['total'] }, {
+        rows: [{ 'account.id': 'a1', total: 130 }, { 'account.id': 'a2', total: 50 }],
+        fields: ['account.id:string', 'total:number'],
+      });
+    });
+
+    it("serves 'account.id' beside 'account.name', where it answered INVALID_QUERY", async () => {
+      await answeredAlike(LIVE, BACKED, { dimensions: ['account.id', 'account.name'], measures: ['total'] }, {
+        rows: [
+          { 'account.id': 'a1', 'account.name': 'Acme', total: 130 },
+          { 'account.id': 'a2', 'account.name': 'Globex', total: 50 },
+        ],
+        fields: ['account.id:string', 'account.name:string', 'total:number'],
+      });
+    });
+
+    it.each([
+      ['after', ['account.name', 'account']],
+      ['before', ['account', 'account.name']],
+    ])("serves the FK column 'account' %s 'account.name'", async (_label, dimensions) => {
+      await answeredAlike(LIVE, BACKED, { dimensions, measures: ['total'] }, {
+        rows: [
+          { account: 'a1', 'account.name': 'Acme', total: 130 },
+          { account: 'a2', 'account.name': 'Globex', total: 50 },
+        ],
+        fields: [...dimensions.map((d) => `${d}:string`), 'total:number'],
+      });
+    });
+
+    it('leaves the draft preview refusing a backed relationship path (#28555)', async () => {
+      await expect(ask('preview', BACKED, { dimensions: ['account.id'], measures: ['total'] })).rejects.toMatchObject({
+        code: 'INVALID_FIELD',
+        status: 400,
+        member: 'account.id',
+      });
+    });
+  });
+});
@@ -2895,6 +2895,9 @@ export class AnalyticsService implements IAnalyticsService {
               seedRows!,
               (field) => this.sourceFieldMeta?.(dataset.object, field)?.type,
               compiled.durations,
+              // [#28691] …and each `where` member the live faces read from a
+              // column spelled otherwise is read from that column.
+              previewWhereColumns(q, cube),
             );
           },
         } as IAnalyticsService;
@@ -4777,6 +4780,43 @@ function previewEvaluationCube(query: AnalyticsQuery, cube: Cube): Cube {
   return Object.keys(aliases).length > 0 ? { ...cube, dimensions: { ...cube.dimensions, ...aliases } } : cube;
 }
 
+/**
+ * [#28691] The column each `where` member resolves to, for every member
+ * spelled other than its column, which the draft-preview evaluator matches
+ * against the drafted rows (they carry columns). `OBJECT.region`,
+ * `CUBE.region` and a dataset dimension `zone` over `region` all read
+ * `region`, as both live strategies read them. Measured before: each matched
+ * no drafted row (`[]`, or under an `$or` only the other arm's rows) where
+ * both live faces served the rows.
+ *
+ * The leaves are read with the reader the strategies compile with
+ * (`normalizeAnalyticsFilterTree` + `collectFilterLeaves`, as
+ * {@link relationshipMembers} reads them), and each is resolved by
+ * {@link declaredMemberEntry}'s `'any'` arm, the strategies' filter-member
+ * lookup. A member that resolves to no declared entry, or to an expression or
+ * a relationship path, is not listed: it is read as written, or was refused
+ * before the evaluator runs.
+ */
+function previewWhereColumns(query: AnalyticsQuery, cube: Cube): Record<string, string> {
+  const where = (query as { where?: unknown }).where;
+  if (!where || typeof where !== 'object') return {};
+  let leaves: string[];
+  try {
+    leaves = collectFilterLeaves(normalizeAnalyticsFilterTree({ where }, NO_DATETIME_COLUMNS)).map((leaf) => leaf.member);
+  } catch {
+    return {};
+  }
+  const out: Record<string, string> = {};
+  for (const member of leaves) {
+    if (out[member] !== undefined) continue;
+    const entry = declaredMemberEntry(cube, member, 'any');
+    if (!entry) continue;
+    const column = typeof entry.sql === 'string' ? entry.sql.trim() : entry.key;
+    if (column !== member && BARE_IDENTIFIER.test(column)) out[member] = column;
+  }
+  return out;
+}
+
 /**
  * [#28172] The measures `measures` names that `cube` (registered as
  * `cubeName`) does not declare, minted