@@ -0,0 +1,17 @@
+---
+'@object-ui/plugin-report': patch
+'@objectstack/spec': patch
+'@objectstack/lint': patch
+---
+
+feat(plugin-report): a report chart draws its `seriesBy` split
+
+Clause-②: no
+Metadata-protocol: none
+
+A report chart that sets `chart.seriesBy` now draws the split it declares: one bar per `xAxis` value, split into one series per value of the `seriesBy` dimension (a bar per owner, split by stage). The chart's own dataset query asks for `[xAxis, seriesBy]` × `[yAxis]` and the rows are pivoted the way a dashboard widget with two dimensions pivots them, null group included. The series follow the split dimension's declared option order, and a `chart.series[]` entry whose `name` is a split value lands its colour and label on that series. Before this, the key was accepted and checked at publish, but the chart still drew a single series.
+
+- **Liveness.** The `chart.seriesBy` row of the report ledger is graded `live` with the renderer as its evidence, so `os validate` no longer prints the "nothing draws it yet" author warning for it.
+- **Lint.** `os explain chart-axis-not-selected` now says the report chart queries its `xAxis` dimension and, when set, its `seriesBy` split. No rule, severity or finding changes.
+
+Nothing to do for existing reports. A chart without `seriesBy` queries and draws exactly as before.
@@ -3302,8 +3302,9 @@ const CHART_AXIS_NOT_SELECTED_EXPLANATION: RuleExplanation = {
       'chart drawn is unaffected. Advisory: the selection may legitimately be widened at runtime. A ' +
       'query position is never reported: it IS the selection, or the query itself.',
     'The selection is per surface. On a page chart it is `values`, the measure set the query asks ' +
-      'for. On a report it is the chart\'s own `chart.yAxis`: the embedded chart queries ' +
-      'exactly one dimension × one measure and derives ONE series, while `report.values` is the ' +
+      'for. On a report it is the chart\'s own `chart.yAxis`: the embedded chart queries its ' +
+      '`chart.xAxis` dimension (and its `chart.seriesBy` split, when set) × that one measure and, ' +
+      'without a split, derives ONE series, while `report.values` is the ' +
       'selection of the table beneath it. So a report\'s `chart.yAxis` is never reported — a chart ' +
       'cannot fail to select what it queries — and a `chart.series[].name` override lands only when ' +
       'it names `chart.yAxis`. With `chart.seriesBy` set the chart derives one series per value of ' +
 
@@ -58,10 +58,12 @@
  * the three surfaces do not agree, so the tier and the consequence are per
  * POSITION rather than per rule:
  *
- *  - **Report charts.** The chart runs its OWN query out of the two axis
- *    strings — `useDatasetRows(dataset, [xAxis], [yAxis], …)` in
+ *  - **Report charts.** The chart runs its OWN query out of the axis
+ *    strings — `useDatasetRows(dataset, [xAxis], [yAxis], …)`, or
+ *    `[xAxis, seriesBy]` × `[yAxis]` with a split, in
  *    `plugin-report/src/DatasetReportRenderer.tsx`, and in that file's own
- *    words *"the embedded chart queries only `chart.xAxis` × `chart.yAxis`"*.
+ *    words *"the embedded chart queries only `chart.xAxis` (with
+ *    `chart.seriesBy`) × `chart.yAxis`"*.
  *    So `chart.yAxis` IS the binding and keeps `error`. `chart.series[]` is
  *    not: it is *"The author's per-chart override for ONE measure's display
  *    name — the entry of `chart.series[]` whose `name` IS that measure"*,
@@ -117,13 +119,15 @@
  *
  * The consequence is per POSITION; the selection it is measured against is per
  * SURFACE — and on the report surface that selection is not `report.values`.
- * At the same pinned revision `DatasetReportRenderer.tsx` runs
- * `useDatasetRows(dataset, plan.kind === 'series' && xAxis ? [xAxis] : [],
- * wantsQuery && yAxis ? [yAxis] : [], …)` and derives the plotted series with
- * `buildChartSeries(…, [xAxis], [yAxis], …)` — *"the selection is exactly one
- * dimension × one measure, so this takes the helper's single-dimension branch
- * and returns ONE series"*. `report.values` is the selection of the TABLE
- * beneath the chart; the chart's own is the axis pair. Two things follow:
+ * `DatasetReportRenderer.tsx` queries `[xAxis]` (`[xAxis, seriesBy]` with a
+ * split) × `[yAxis]` through `useDatasetRows` and derives the plotted series
+ * with `buildChartSeries(…, queryDimensions, [yAxis], …)` — *"Without
+ * `seriesBy` the selection is one dimension × one
+ * measure, so this takes the helper's single-dimension branch and returns ONE
+ * series"*; with it, one series per `seriesBy` value, whose override names a
+ * value and is not judged here (below). `report.values` is the selection of
+ * the TABLE beneath the chart; the chart's own is the axis pair. Two things
+ * follow:
  *
  *  - **Nothing to report at the report `chart.yAxis`.** That position IS the
  *    chart's query, so it cannot fail to select itself. The warning that fired
@@ -293,8 +297,9 @@ interface ChartBinding {
   /**
    * The measures THIS chart's own query selects, when that is narrower than
    * the `values` limb above (#15734). Set on the report surface and nowhere
-   * else: the embedded report chart queries `chart.xAxis` × `chart.yAxis`
-   * alone and derives exactly ONE series from it, while `report.values` is the
+   * else: the embedded report chart queries `chart.xAxis` (with its
+   * `chart.seriesBy` split, when set) × `chart.yAxis` alone and, without a
+   * split, derives exactly ONE series from it, while `report.values` is the
    * selection of the table beneath it. `chart-axis-not-selected` resolves
    * against this set where it is present — which is both why a `series[].name`
    * override is measured against the singleton `{ chart.yAxis }`, and why the
 
@@ -51,7 +51,7 @@
     "chart": {
       "status": "live",
       "verifiedAt": "2026-09-27",
-      "note": "objectui: DatasetReportChart plots `chart.xAxis` (dataset dimension) × `chart.yAxis` (measure) via useDatasetRows, honoring `type`/`title` (framework#1890/#3441). Supersedes the 2026-06 audit's DEAD finding. Sub-key `groupBy` stays experimental (its own describe marker) — the dataset renderer plots a single series and never reads it. Live on NON-joined reports only (#20161, re-read at the `.objectui-sha` pin f8a9d0fb): the one `report.chart` read (DatasetReportRenderer.tsx:1557) sits after the joined branch's return (:1462-1524), so on a `type: 'joined'` report the schema's refinement REFUSES `chart` rather than accepting a key nothing reads. A `joined` report draws no chart (packages/spec/src/ui/report.zod.ts, the joined-chart prescription, #20161; read point moved out of spec source, #23434): at objectui @f8a9d0fb0596 packages/plugin-report/src/DatasetReportRenderer.tsx#DatasetReportRenderer the joined branch draws each block as a `DatasetMatrixTable` / `DatasetReportTable` and returns before the one `report.chart` read, and no renderer reads a block's `chart`.",
+      "note": "objectui: DatasetReportChart plots `chart.xAxis` (dataset dimension) × `chart.yAxis` (measure) via useDatasetRows, honoring `type`/`title` (framework#1890/#3441). Supersedes the 2026-06 audit's DEAD finding. With `chart.seriesBy` set it also groups by that second dimension and draws a series per value of it (the `seriesBy` row below). Live on NON-joined reports only (#20161, re-read at the `.objectui-sha` pin f8a9d0fb): the one `report.chart` read (DatasetReportRenderer.tsx:1557) sits after the joined branch's return (:1462-1524), so on a `type: 'joined'` report the schema's refinement REFUSES `chart` rather than accepting a key nothing reads. A `joined` report draws no chart (packages/spec/src/ui/report.zod.ts, the joined-chart prescription, #20161; read point moved out of spec source, #23434): at objectui @f8a9d0fb0596 packages/plugin-report/src/DatasetReportRenderer.tsx#DatasetReportRenderer the joined branch draws each block as a `DatasetMatrixTable` / `DatasetReportTable` and returns before the one `report.chart` read, and no renderer reads a block's `chart`.",
       "childrenDefault": "live",
       "children": {
         "aria": {
@@ -60,13 +60,11 @@
           "note": "REMOVED in @objectstack/spec 17 (ADR-0049 D2; the `chart-config-aria-removed` conversion): `ChartConfigSchema` tombstones it with retiredKey, so authoring `report.chart.aria` is a tsc error and a parse error carrying the prescription (use `description` on this same chart config). The row exists because the tombstone keeps the key in the walked shape now that `chart` drills; the retirement record is `dashboard.json`'s `widgets.chartConfig.aria` row."
         },
         "seriesBy": {
-          "status": "planned",
-          "verifiedAt": "2026-10-30",
+          "status": "live",
+          "verifiedAt": "2026-10-31",
           "evidenceScope": "in-repo",
-          "evidence": "packages/spec/src/ui/report.zod.ts#ReportChartSchema (declares `seriesBy`, an optional dataset dimension name); packages/lint/src/validate-chart-bindings.ts#validateChartBindings (resolves it against the report's bound dataset dimensions exactly as `xAxis`, `chart-dimension-unknown` at error, at os validate / os build and the report publish door)",
-          "authorWarn": true,
-          "authorHint": "Keep it, but nothing draws it yet: the report chart still draws a single series, and the split by this dimension appears once the report renderer reads `seriesBy`.",
-          "note": "Spec half of the report chart series split (#27974): a second dataset dimension that splits the one `yAxis` measure into a series per value, the report's spelling of a dashboard widget's two-entry `dimensions` selection. Planned because the renderer half is a follow-up: at this tree ui/packages/plugin-report/src/DatasetReportRenderer.tsx#DatasetReportChart still queries `[xAxis]` × `[yAxis]` and hands `buildChartSeries` one dimension, so the split is not drawn. The other children of `chart` inherit the row's `live` verdict through `childrenDefault`; this row exists to keep that blanket from vouching for the one key nothing reads yet. Flip to `live` with the renderer card."
+          "evidence": "ui/packages/plugin-report/src/DatasetReportRenderer.tsx#DatasetReportChart (reads `chart.seriesBy`, queries `[xAxis, seriesBy]` × `[yAxis]` and pivots the rows through `buildChartSeries` into one series per value); ui/packages/plugin-report/src/__tests__/DatasetReportRenderer.chartSeriesBy-28206.test.tsx; packages/lint/src/validate-chart-bindings.ts#validateChartBindings (resolves it against the report's bound dataset dimensions exactly as `xAxis`, `chart-dimension-unknown` at error, at os validate / os build and the report publish door)",
+          "note": "The report chart series split (#27974 spec half, #28206 renderer half): a second dataset dimension that splits the one `yAxis` measure into a series per value, the report's spelling of a dashboard widget's two-entry `dimensions` selection. LIVE: DatasetReportChart widens its own query to `[xAxis, seriesBy]` × `[yAxis]` and hands both dimensions to `buildChartSeries` (ui/packages/core/src/utils/chart-series.ts), whose pivot branch draws one row per x bucket and one series per `seriesBy` value, the null group included; the series follow the split dimension's declared option order, and a `series[]` entry whose `name` is a split value lands its presentation on that series. Without `seriesBy` the chart queries and draws exactly what it did before. The other children of `chart` inherit the row's `live` verdict through `childrenDefault`; this row stays to carry the reader as evidence."
         }
       }
     },
 
@@ -12,4 +12,4 @@ committed anywhere: `check:liveness` sums the shards when it reads them.
 
 | Type | live | exp | elsewhere | dead | planned | classified |
 |---|---|---|---|---|---|---|
-| `report` | 39 | 0 | 0 | 1 | 1 | 41 |
+| `report` | 40 | 0 | 0 | 1 | 0 | 41 |