feat(charts): make stacking a property of TimeSeries and Bar charts

Charts now take a `stack` prop and hand it to their config, which derives
everything else. Callers no longer compute fill bands or transform data:
V1 and V2 bar panels, Meter Explorer and Billing each drop their
`setBands` call and declare `stack` instead.

The stacking hook moves next to the shell that runs it and is no longer
bar-specific, so TimeSeries stacks too — which is what the upcoming area
chart will build on. `stack` sits on the two chart prop types rather than
the shared config, so kinds that cannot stack never expose it.

Assisted-by: Claude Opus 5

frontend/src/container/BillingContainer/BillingUsageGraph/BillingUsageGraph.tsx

@@ -5,6 +5,7 @@ import BarChart from 'container/DashboardContainer/visualization/charts/BarChart
 import { useIsDarkMode } from 'hooks/useDarkMode';
 import { useResizeObserver } from 'hooks/useDimensions';
 import { prepareChartData } from 'lib/uPlotV2/utils/dataUtils';
+import { StackMode } from 'lib/uPlotV2/config/types';
 import {
 	LegendPosition,
 	TooltipRenderArgs,
@@ -131,9 +132,9 @@ export function BillingUsageGraph(props: BillingUsageGraphProps): JSX.Element {
 			<div ref={graphRef} className={styles.graphContainer}>
 				{containerDimensions.width > 0 && containerDimensions.height > 0 && (
 					<BarChart
+						stack={StackMode.Normal}
 						config={config}
 						data={chartData}
-						isStackedBarChart
 						legendConfig={{ position: LegendPosition.BOTTOM }}
 						customTooltip={renderBillingTooltip}
 						width={containerDimensions.width}

frontend/src/container/BillingContainer/BillingUsageGraph/__tests__/prepareBillingBarConfig.test.ts

@@ -58,26 +58,17 @@ describe('prepareBillingBarConfig', () => {
 		expect(config.series?.[4]?.stroke).toBe(Color.BG_AMBER_500);
 	});
 
-	it('sets stacking bands, padding, and focus alpha for behavioral parity', () => {
+	it('sets padding and focus alpha for behavioral parity', () => {
 		const builder = prepareBillingBarConfig({
 			...baseProps,
 			apiResponse: makeApiResponse(['Logs', 'Traces', 'Metrics']),
 		});
 		const config = builder.getConfig();
-		expect(config.bands).toStrictEqual([{ series: [1, 2] }, { series: [2, 3] }]);
+		// Stacking bands come from the chart now — see useChartStacking.
 		expect(config.padding).toStrictEqual([32, 32, 16, 16]);
 		expect(config.focus).toStrictEqual({ alpha: 0.3 });
 	});
 
-	it('sets no bands when result is empty', () => {
-		const builder = prepareBillingBarConfig({
-			...baseProps,
-			apiResponse: makeApiResponse([]),
-		});
-		const config = builder.getConfig();
-		expect(config.bands).toBeUndefined();
-	});
-
 	it('uses queryName as label when legend is undefined', () => {
 		const apiResponse: MetricRangePayloadProps = {
 			data: {

frontend/src/container/BillingContainer/BillingUsageGraph/prepareBillingBarConfig.ts

@@ -1,7 +1,6 @@
 import { Color } from '@signozhq/design-tokens';
 import type { Timezone } from 'components/CustomTimePicker/timezoneUtils';
 import { PANEL_TYPES } from 'constants/queryBuilder';
-import { getInitialStackedBands } from 'container/DashboardContainer/visualization/charts/utils/stackSeriesUtils';
 import { buildBaseConfig } from 'container/DashboardContainer/visualization/panels/utils/baseConfigBuilder';
 import { DrawStyle } from 'lib/uPlotV2/config/types';
 import type { UPlotConfigBuilder } from 'lib/uPlotV2/config/UPlotConfigBuilder';
@@ -63,7 +62,6 @@ export function prepareBillingBarConfig({
 		});
 	});
 
-	builder.setBands(getInitialStackedBands(results.length));
 	builder.setPadding([32, 32, 16, 16]);
 	builder.setFocus({ alpha: 0.3 });
 

frontend/src/container/DashboardContainer/visualization/charts/BarChart/BarChart.tsx

@@ -6,25 +6,24 @@ import {
 	TooltipRenderArgs,
 } from 'lib/uPlotV2/components/types';
 
-import { useBarChartStacking } from '../../hooks/useBarChartStacking';
+import { StackMode } from 'lib/uPlotV2/config/types';
+
 import { BarChartProps } from '../types';
 
 export default function BarChart(props: BarChartProps): JSX.Element {
 	const {
 		children,
-		isStackedBarChart,
 		customTooltip,
 		config,
 		data,
+		stack = StackMode.None,
 		pinnedTooltipElement,
 		...rest
 	} = props;
 
-	const chartData = useBarChartStacking({
-		data,
-		isStackedBarChart,
-		config,
-	});
+	// Written during render so it lands before UPlotChart's effect reads the config,
+	// which derives the fill bands, percent axis unit and percent range from it.
+	config.setStack(stack);
 
 	const renderTooltip = useCallback(
 		(props: TooltipRenderArgs): React.ReactNode => {
@@ -37,7 +36,6 @@ export default function BarChart(props: BarChartProps): JSX.Element {
 				timezone: rest.timezone,
 				yAxisUnit: rest.yAxisUnit,
 				decimalPrecision: rest.decimalPrecision,
-				isStackedBarChart: isStackedBarChart,
 				canPinTooltip: rest.canPinTooltip,
 				renderTooltipFooter: rest.renderTooltipFooter,
 			};
@@ -48,7 +46,6 @@ export default function BarChart(props: BarChartProps): JSX.Element {
 			rest.timezone,
 			rest.yAxisUnit,
 			rest.decimalPrecision,
-			isStackedBarChart,
 			rest.canPinTooltip,
 			rest.renderTooltipFooter,
 		],
@@ -58,7 +55,7 @@ export default function BarChart(props: BarChartProps): JSX.Element {
 		<ChartWrapper
 			{...rest}
 			config={config}
-			data={chartData}
+			data={data}
 			customTooltip={renderTooltip}
 			pinnedTooltipElement={pinnedTooltipElement}
 		>

frontend/src/container/DashboardContainer/visualization/charts/ChartWrapper/ChartWrapper.tsx

@@ -6,12 +6,15 @@ import {
 	TooltipRenderArgs,
 } from 'lib/uPlotV2/components/types';
 import UPlotChart from 'lib/uPlotV2/components/UPlotChart/UPlotChart';
+import { StackMode } from 'lib/uPlotV2/config/types';
+import { prepareAlignedData } from 'lib/uPlotV2/components/UPlotChart/utils';
 import { PlotContextProvider } from 'lib/uPlotV2/context/PlotContext';
 import TooltipPlugin from 'lib/uPlotV2/plugins/TooltipPlugin/TooltipPlugin';
 import noop from 'lodash-es/noop';
 import uPlot from 'uplot';
 
-import { ChartProps } from '../types';
+import { ChartWrapperProps } from '../types';
+import { useChartStacking } from './useChartStacking';
 
 const TOOLTIP_WIDTH_PADDING = 120;
 const TOOLTIP_MIN_WIDTH = 300;
@@ -39,9 +42,20 @@ export default function ChartWrapper({
 	pinnedTooltipElement,
 	tooltipPortalRoot,
 	'data-testid': testId,
-}: ChartProps): JSX.Element {
+}: ChartWrapperProps): JSX.Element {
 	const plotInstanceRef = useRef<uPlot | null>(null);
 
+	const stack = config.getStackMode();
+	const chartData = useChartStacking({ data, config });
+
+	// Tooltips need pre-stack values, gap-processed exactly as UPlotChart processes the
+	// plot data — otherwise the cursor's index addresses a shorter array.
+	const unstackedData = useMemo(
+		() =>
+			stack === StackMode.None ? undefined : prepareAlignedData({ data, config }),
+		[data, config, stack],
+	);
+
 	const legendComponent = useCallback(
 		(averageLegendWidth: number): React.ReactNode => {
 			if (!showLegend) {
@@ -61,11 +75,11 @@ export default function ChartWrapper({
 	const renderTooltipCallback = useCallback(
 		(args: TooltipRenderArgs): React.ReactNode => {
 			if (customTooltip) {
-				return customTooltip(args);
+				return customTooltip({ ...args, unstackedData });
 			}
 			return null;
 		},
-		[customTooltip],
+		[customTooltip, unstackedData],
 	);
 
 	const syncMetadata = useMemo(
@@ -91,7 +105,7 @@ export default function ChartWrapper({
 				{({ chartWidth, chartHeight, averageLegendWidth }): JSX.Element => (
 					<UPlotChart
 						config={config}
-						data={data}
+						data={chartData}
 						width={chartWidth}
 						height={chartHeight}
 						plotRef={(plot): void => {

frontend/src/container/DashboardContainer/visualization/charts/ChartWrapper/__tests__/useChartStacking.test.ts

@@ -0,0 +1,98 @@
+import { renderHook } from '@testing-library/react';
+import { UPlotConfigBuilder } from 'lib/uPlotV2/config/UPlotConfigBuilder';
+import { StackMode } from 'lib/uPlotV2/config/types';
+import uPlot from 'uplot';
+
+import { useChartStacking } from '../useChartStacking';
+
+type Hooks = Record<string, (...args: unknown[]) => void>;
+
+function createConfig(stack: StackMode): {
+	config: UPlotConfigBuilder;
+	hooks: Hooks;
+} {
+	const hooks: Hooks = {};
+	const config = {
+		getStackMode: (): StackMode => stack,
+		addHook: jest.fn((type: string, hook: (...args: unknown[]) => void) => {
+			hooks[type] = hook;
+			return jest.fn();
+		}),
+	} as unknown as UPlotConfigBuilder;
+	return { config, hooks };
+}
+
+const data = [[1], [30], [10]] as unknown as uPlot.AlignedData;
+
+describe('useChartStacking', () => {
+	it('returns the data untouched and registers nothing when the config says `none`', () => {
+		const { config } = createConfig(StackMode.None);
+		const { result } = renderHook(() => useChartStacking({ data, config }));
+
+		expect(result.current).toBe(data);
+		expect(config.addHook).not.toHaveBeenCalled();
+	});
+
+	it('treats a missing config as unstacked', () => {
+		const { result } = renderHook(() => useChartStacking({ data, config: null }));
+
+		expect(result.current).toBe(data);
+	});
+
+	it('accumulates raw values when the config declares `normal`', () => {
+		const { config } = createConfig(StackMode.Normal);
+		const { result } = renderHook(() => useChartStacking({ data, config }));
+
+		expect(result.current).toStrictEqual([[1], [40], [10]]);
+	});
+
+	it('rescales each column to its total when the config declares `percent`', () => {
+		const { config } = createConfig(StackMode.Percent);
+		const { result } = renderHook(() => useChartStacking({ data, config }));
+
+		expect(result.current).toStrictEqual([[1], [100], [25]]);
+	});
+
+	it('registers the uPlot hooks that re-stack on data and visibility changes', () => {
+		const { config } = createConfig(StackMode.Normal);
+		renderHook(() => useChartStacking({ data, config }));
+
+		expect(
+			(config.addHook as jest.Mock).mock.calls.map(([type]) => type),
+		).toStrictEqual(['setData', 'setSeries']);
+	});
+
+	it('re-stacks from the raw values when the legend hides a series', () => {
+		const { config, hooks } = createConfig(StackMode.Normal);
+		renderHook(() => useChartStacking({ data, config }));
+
+		const plot = {
+			data: [[1]],
+			series: [{}, { show: true }, { show: false }],
+			delBand: jest.fn(),
+			addBand: jest.fn(),
+			setData: jest.fn(),
+		};
+		hooks.setSeries(plot, 2, { show: false });
+
+		// The hidden series keeps its raw value and stops contributing to the total.
+		expect(plot.setData).toHaveBeenCalledWith([[1], [30], [10]]);
+		expect(plot.delBand).toHaveBeenCalledWith(null);
+	});
+
+	it('ignores a focus-only setSeries so hovering does not re-stack', () => {
+		const { config, hooks } = createConfig(StackMode.Normal);
+		renderHook(() => useChartStacking({ data, config }));
+
+		const plot = {
+			data: [[1]],
+			series: [{}, { show: true }, { show: true }],
+			delBand: jest.fn(),
+			addBand: jest.fn(),
+			setData: jest.fn(),
+		};
+		hooks.setSeries(plot, 1, { focus: true });
+
+		expect(plot.setData).not.toHaveBeenCalled();
+	});
+});

frontend/src/container/DashboardContainer/visualization/charts/ChartWrapper/useChartStacking.ts

@@ -6,10 +6,11 @@ import {
 	useRef,
 } from 'react';
 import { UPlotConfigBuilder } from 'lib/uPlotV2/config/UPlotConfigBuilder';
+import { StackMode } from 'lib/uPlotV2/config/types';
 import { has } from 'lodash-es';
 import uPlot from 'uplot';
 
-import { stackSeries } from '../charts/utils/stackSeriesUtils';
+import { stackSeries } from '../utils/stackSeriesUtils';
 
 /** Returns true if the series at the given index is hidden (e.g. via legend toggle). */
 function isSeriesHidden(plot: uPlot, seriesIndex: number): boolean {
@@ -31,12 +32,12 @@ function canApplyStacking(
 
 function setupStackingHooks(
 	config: UPlotConfigBuilder,
-	applyStackingToChart: (plot: uPlot) => void,
+	restack: (plot: uPlot) => void,
 	isUpdatingRef: MutableRefObject<boolean>,
 ): () => void {
 	const onDataChange = (plot: uPlot): void => {
 		if (!isUpdatingRef.current) {
-			applyStackingToChart(plot);
+			restack(plot);
 		}
 	};
 
@@ -45,8 +46,9 @@ function setupStackingHooks(
 		_seriesIdx: number | null,
 		opts: uPlot.Series,
 	): void => {
+		// uPlot fires setSeries for hover focus too; only visibility changes restack.
 		if (!has(opts, 'focus')) {
-			applyStackingToChart(plot);
+			restack(plot);
 		}
 	};
 
@@ -62,64 +64,69 @@ function setupStackingHooks(
 	};
 }
 
-export interface UseBarChartStackingParams {
+export interface UseChartStackingParams {
 	data: uPlot.AlignedData;
-	isStackedBarChart?: boolean;
 	config: UPlotConfigBuilder | null;
 }
 
 /**
- * Handles stacking for bar charts: computes initial stacked data and re-stacks
- * when data or series visibility changes (e.g. legend toggles).
+ * Stacks a chart's data for the mode declared on its config, and re-stacks on data or
+ * visibility changes. The pre-stack values live in a ref because the uPlot hooks that
+ * read them run outside React's render cycle.
  */
-export function useBarChartStacking({
+export function useChartStacking({
 	data,
-	isStackedBarChart = false,
 	config,
-}: UseBarChartStackingParams): uPlot.AlignedData {
-	// Store unstacked source data so uPlot hooks can access it (hooks run outside React's render cycle)
+}: UseChartStackingParams): uPlot.AlignedData {
+	const stack = config?.getStackMode() ?? StackMode.None;
 	const unstackedDataRef = useRef<uPlot.AlignedData | null>(null);
-	unstackedDataRef.current = isStackedBarChart ? data : null;
+	unstackedDataRef.current = stack === 'none' ? null : data;
 
-	// Prevents re-entrant calls when we update chart data (avoids infinite loop in setData hook)
+	// Guards the re-entrant setData below, which would otherwise re-trigger our own hook.
 	const isUpdatingChartRef = useRef(false);
 
 	const chartData = useMemo((): uPlot.AlignedData => {
-		if (!isStackedBarChart || !data || data.length < 2) {
+		if (stack === StackMode.None || !data || data.length < 2) {
 			return data;
 		}
 		const noSeriesHidden = (): boolean => false; // include all series in initial stack
-		const { data: stacked } = stackSeries(data, noSeriesHidden);
-		return stacked;
-	}, [data, isStackedBarChart]);
+		return stackSeries(data, noSeriesHidden, stack).data;
+	}, [data, stack]);
 
-	const applyStackingToChart = useCallback((plot: uPlot): void => {
-		const unstacked = unstackedDataRef.current;
-		if (
-			!unstacked ||
-			!canApplyStacking(unstacked, plot, isUpdatingChartRef.current)
-		) {
-			return;
-		}
+	const restack = useCallback(
+		(plot: uPlot): void => {
+			const unstacked = unstackedDataRef.current;
+			if (
+				!unstacked ||
+				!canApplyStacking(unstacked, plot, isUpdatingChartRef.current)
+			) {
+				return;
+			}
 
-		const shouldExcludeSeries = (idx: number): boolean =>
-			isSeriesHidden(plot, idx);
-		const { data: stacked, bands } = stackSeries(unstacked, shouldExcludeSeries);
+			const shouldExcludeSeries = (idx: number): boolean =>
+				isSeriesHidden(plot, idx);
+			const { data: stacked, bands } = stackSeries(
+				unstacked,
+				shouldExcludeSeries,
+				stack,
+			);
 
-		plot.delBand(null);
-		bands.forEach((band: uPlot.Band) => plot.addBand(band));
+			plot.delBand(null);
+			bands.forEach((band: uPlot.Band) => plot.addBand(band));
 
-		isUpdatingChartRef.current = true;
-		plot.setData(stacked);
-		isUpdatingChartRef.current = false;
-	}, []);
+			isUpdatingChartRef.current = true;
+			plot.setData(stacked);
+			isUpdatingChartRef.current = false;
+		},
+		[stack],
+	);
 
 	useLayoutEffect(() => {
-		if (!isStackedBarChart || !config) {
+		if (stack === StackMode.None || !config) {
 			return undefined;
 		}
-		return setupStackingHooks(config, applyStackingToChart, isUpdatingChartRef);
-	}, [isStackedBarChart, config, applyStackingToChart]);
+		return setupStackingHooks(config, restack, isUpdatingChartRef);
+	}, [stack, config, restack]);
 
 	return chartData;
 }

frontend/src/container/DashboardContainer/visualization/charts/TimeSeries/TimeSeries.tsx

@@ -6,10 +6,16 @@ import {
 	TooltipRenderArgs,
 } from 'lib/uPlotV2/components/types';
 
+import { StackMode } from 'lib/uPlotV2/config/types';
+
 import { TimeSeriesChartProps } from '../types';
 
 export default function TimeSeries(props: TimeSeriesChartProps): JSX.Element {
-	const { children, customTooltip, ...rest } = props;
+	const { children, customTooltip, stack = StackMode.None, ...rest } = props;
+
+	// Written during render so it lands before UPlotChart's effect reads the config,
+	// which derives the fill bands, percent axis unit and percent range from it.
+	rest.config.setStack(stack);
 
 	const renderTooltip = useCallback(
 		(props: TooltipRenderArgs): React.ReactNode => {

frontend/src/container/DashboardContainer/visualization/charts/types.ts

@@ -14,6 +14,7 @@ import {
 	ChartClickData,
 } from 'lib/uPlotV2/plugins/TooltipPlugin/types';
 import { BaseAutocompleteData } from 'types/api/queryBuilder/queryAutocompleteResponse';
+import type { StackMode } from 'lib/uPlotV2/config/types';
 
 interface BaseChartProps {
 	width: number;
@@ -52,27 +53,26 @@ interface UPlotChartDataProps {
 	groupByPerQuery?: Record<string, BaseAutocompleteData[]>;
 }
 
-export interface TimeSeriesChartProps
-	extends BaseChartProps, UPlotBasedChartProps, UPlotChartDataProps {
+/** Everything the shared uPlot shell consumes; each chart's props narrow it. */
+export interface ChartWrapperProps
+	extends BaseChartProps, UPlotBasedChartProps, UPlotChartDataProps {}
+
+export interface TimeSeriesChartProps extends ChartWrapperProps {
 	timezone?: Timezone;
+	/** How series compose. Defaults to `none`, which draws them independently. */
+	stack?: StackMode;
 }
 
-export interface HistogramChartProps
-	extends BaseChartProps, UPlotBasedChartProps, UPlotChartDataProps {
+export interface BarChartProps extends ChartWrapperProps {
+	timezone?: Timezone;
+	/** How series compose. Defaults to `none`, which draws them independently. */
+	stack?: StackMode;
+}
+
+export interface HistogramChartProps extends ChartWrapperProps {
 	isQueriesMerged?: boolean;
 }
 
-export interface BarChartProps
-	extends BaseChartProps, UPlotBasedChartProps, UPlotChartDataProps {
-	isStackedBarChart?: boolean;
-	timezone?: Timezone;
-}
-
-export type ChartProps =
-	| TimeSeriesChartProps
-	| BarChartProps
-	| HistogramChartProps;
-
 /**
  * One resolved pie/donut slice: a display label, its (already parsed) positive
  * numeric value, and the colour used for the arc + legend swatch.

frontend/src/container/DashboardContainer/visualization/charts/utils/__tests__/stackSeriesUtils.test.ts

@@ -0,0 +1,158 @@
+import { AlignedData } from 'uplot';
+
+import { StackMode } from 'lib/uPlotV2/config/types';
+
+import { stackSeries } from '../stackSeriesUtils';
+
+const includeAll = (): boolean => false;
+
+// Stacking is top-down: the first series carries the column total, the last its own
+// raw value. Every expectation below reads in that order.
+describe('stackSeries', () => {
+	it('is a no-op under `none`, returning the data and no bands', () => {
+		const data: AlignedData = [[1], [30], [10]];
+
+		const { data: result, bands } = stackSeries(data, includeAll, StackMode.None);
+
+		expect(result).toBe(data);
+		expect(bands).toStrictEqual([]);
+	});
+
+	describe('normal', () => {
+		it('accumulates raw values from the bottom series upward', () => {
+			const data: AlignedData = [
+				[1, 2],
+				[10, 20],
+				[1, 2],
+			];
+
+			expect(stackSeries(data, includeAll, StackMode.Normal).data).toStrictEqual([
+				[1, 2],
+				[11, 22],
+				[1, 2],
+			]);
+		});
+
+		it('treats nulls as 0 without breaking the running total', () => {
+			const data: AlignedData = [
+				[1, 2],
+				[10, null],
+				[1, 2],
+			];
+
+			expect(stackSeries(data, includeAll, StackMode.Normal).data).toStrictEqual([
+				[1, 2],
+				[11, 2],
+				[1, 2],
+			]);
+		});
+
+		it('emits one band per adjacent pair of participating series', () => {
+			const data: AlignedData = [[1], [10], [5], [1]];
+
+			expect(stackSeries(data, includeAll, StackMode.Normal).bands).toStrictEqual([
+				{ series: [1, 2] },
+				{ series: [2, 3] },
+			]);
+		});
+
+		it('copies omitted series through unstacked and skips their bands', () => {
+			const data: AlignedData = [[1], [10], [5], [1]];
+			const omitMiddle = (seriesIndex: number): boolean => seriesIndex === 2;
+
+			const { data: stacked, bands } = stackSeries(
+				data,
+				omitMiddle,
+				StackMode.Normal,
+			);
+
+			expect(stacked).toStrictEqual([[1], [11], [5], [1]]);
+			expect(bands).toStrictEqual([{ series: [1, 3] }]);
+		});
+	});
+
+	describe('percent', () => {
+		it('rescales each column to its total so the top series reads 100', () => {
+			const data: AlignedData = [
+				[1, 2],
+				[30, 10],
+				[10, 10],
+			];
+
+			expect(stackSeries(data, includeAll, StackMode.Percent).data).toStrictEqual([
+				[1, 2],
+				[100, 100],
+				[25, 50],
+			]);
+		});
+
+		it('normalises per column, so an identical series differs across x', () => {
+			const data: AlignedData = [
+				[1, 2],
+				[1, 3],
+				[1, 1],
+			];
+
+			expect(stackSeries(data, includeAll, StackMode.Percent).data).toStrictEqual([
+				[1, 2],
+				[100, 100],
+				[50, 25],
+			]);
+		});
+
+		it('excludes omitted series from the total, so the visible ones still reach 100', () => {
+			const data: AlignedData = [[1], [30], [10], [60]];
+			const omitLast = (seriesIndex: number): boolean => seriesIndex === 3;
+
+			expect(stackSeries(data, omitLast, StackMode.Percent).data).toStrictEqual([
+				[1],
+				[100],
+				[25],
+				[60],
+			]);
+		});
+
+		it('yields 0 for a column whose participating series sum to zero', () => {
+			const data: AlignedData = [
+				[1, 2],
+				[0, 5],
+				[0, 5],
+			];
+
+			expect(stackSeries(data, includeAll, StackMode.Percent).data).toStrictEqual([
+				[1, 2],
+				[0, 100],
+				[0, 50],
+			]);
+		});
+
+		it('divides by the signed total when a column mixes signs', () => {
+			// 30 + (-10) = 20, so the shares are 150% and -50% and still sum to 100.
+			const data: AlignedData = [[1], [30], [-10]];
+
+			expect(stackSeries(data, includeAll, StackMode.Percent).data).toStrictEqual([
+				[1],
+				[100],
+				[-50],
+			]);
+		});
+
+		it('yields 0 across a column whose signed total cancels to zero', () => {
+			const data: AlignedData = [[1], [10], [-10]];
+
+			expect(stackSeries(data, includeAll, StackMode.Percent).data).toStrictEqual([
+				[1],
+				[0],
+				[0],
+			]);
+		});
+	});
+
+	it('defaults to normal when no mode is given', () => {
+		const data: AlignedData = [[1], [30], [10]];
+
+		expect(stackSeries(data, includeAll).data).toStrictEqual(
+			stackSeries(data, includeAll, StackMode.Normal).data,
+		);
+	});
+});

frontend/src/container/DashboardContainer/visualization/charts/utils/stackSeriesUtils.ts

@@ -1,13 +1,20 @@
+import { StackMode } from 'lib/uPlotV2/config/types';
 import uPlot, { AlignedData } from 'uplot';
 
 /**
  * Stack data cumulatively (top-down: first series = top, last = bottom).
- * When `omit(seriesIndex)` returns true, that series is excluded from stacking.
+ * When `omit(seriesIndex)` returns true, that series keeps its raw values and
+ * contributes nothing to the total. `None` is a no-op.
  */
 export function stackSeries(
 	data: AlignedData,
 	omit: (seriesIndex: number) => boolean,
+	mode: StackMode = StackMode.Normal,
 ): { data: AlignedData; bands: uPlot.Band[] } {
+	if (mode === StackMode.None) {
+		return { data, bands: [] };
+	}
+
 	const timeAxis = data[0];
 	const pointCount = timeAxis.length;
 	const valueSeriesCount = data.length - 1; // exclude time axis
@@ -17,6 +24,7 @@ export function stackSeries(
 		valueSeriesCount,
 		pointCount,
 		omit,
+		mode,
 	});
 	const bands = buildFillBands(valueSeriesCount + 1, omit); // +1 for 1-based series indices
 
@@ -31,6 +39,34 @@ interface BuildStackedSeriesParams {
 	valueSeriesCount: number;
 	pointCount: number;
 	omit: (seriesIndex: number) => boolean;
+	mode: StackMode;
+}
+
+/** Per-point total. Mixed-sign columns sum signed, as "share of total" implies. */
+function columnTotals({
+	data,
+	valueSeriesCount,
+	pointCount,
+	omit,
+}: Omit<BuildStackedSeriesParams, 'mode'>): number[] {
+	const totals = Array(pointCount).fill(0) as number[];
+
+	for (let seriesIndex = 1; seriesIndex <= valueSeriesCount; seriesIndex++) {
+		if (omit(seriesIndex)) {
+			continue;
+		}
+		const rawValues = data[seriesIndex] as (number | null)[];
+		rawValues.forEach((rawValue, pointIndex) => {
+			totals[pointIndex] += rawValue == null ? 0 : Number(rawValue);
+		});
+	}
+
+	return totals;
+}
+
+/** A column whose participating series sum to 0 has no share to divide, so every slice is 0. */
+function toPercent(value: number, total: number): number {
+	return total === 0 ? 0 : (value / total) * 100;
 }
 
 /**
@@ -42,9 +78,15 @@ function buildStackedSeries({
 	valueSeriesCount,
 	pointCount,
 	omit,
+	mode,
 }: BuildStackedSeriesParams): (number | null)[][] {
 	const stackedSeries: (number | null)[][] = Array(valueSeriesCount);
 	const cumulativeSums = Array(pointCount).fill(0) as number[];
+	// Known up front: totals span series the accumulation below has not reached yet.
+	const totals =
+		mode === StackMode.Percent
+			? columnTotals({ data, valueSeriesCount, pointCount, omit })
+			: undefined;
 
 	for (let seriesIndex = valueSeriesCount; seriesIndex >= 1; seriesIndex--) {
 		const rawValues = data[seriesIndex] as (number | null)[];
@@ -54,7 +96,10 @@ function buildStackedSeries({
 		} else {
 			stackedSeries[seriesIndex - 1] = rawValues.map((rawValue, pointIndex) => {
 				const numericValue = rawValue == null ? 0 : Number(rawValue);
-				return (cumulativeSums[pointIndex] += numericValue);
+				const contribution = totals
+					? toPercent(numericValue, totals[pointIndex])
+					: numericValue;
+				return (cumulativeSums[pointIndex] += contribution);
 			});
 		}
 	}
@@ -101,16 +146,3 @@ function findNextVisibleSeriesIndex(
 	}
 	return -1;
 }
-
-/**
- * Returns band indices for initial stacked state (no series omitted).
- * Top-down: first series at top, band fills between consecutive series.
- * uPlot band format: [upperSeriesIdx, lowerSeriesIdx].
- */
-export function getInitialStackedBands(seriesCount: number): uPlot.Band[] {
-	const bands: uPlot.Band[] = [];
-	for (let seriesIndex = 1; seriesIndex < seriesCount; seriesIndex++) {
-		bands.push({ series: [seriesIndex, seriesIndex + 1] });
-	}
-	return bands;
-}

frontend/src/container/DashboardContainer/visualization/hooks/__tests__/useBarChartStacking.test.ts

@@ -1,313 +0,0 @@
-import { renderHook } from '@testing-library/react';
-import uPlot from 'uplot';
-
-import type { UseBarChartStackingParams } from '../useBarChartStacking';
-import { useBarChartStacking } from '../useBarChartStacking';
-
-type MockConfig = { addHook: jest.Mock };
-
-function asConfig(c: MockConfig): UseBarChartStackingParams['config'] {
-	return c as unknown as UseBarChartStackingParams['config'];
-}
-
-function createMockConfig(): {
-	config: MockConfig;
-	invokeSetData: (plot: uPlot) => void;
-	invokeSetSeries: (
-		plot: uPlot,
-		seriesIndex: number | null,
-		opts: Partial<uPlot.Series> & { focus?: boolean },
-	) => void;
-	removeSetData: jest.Mock;
-	removeSetSeries: jest.Mock;
-} {
-	let setDataHandler: ((plot: uPlot) => void) | null = null;
-	let setSeriesHandler:
-		| ((plot: uPlot, seriesIndex: number | null, opts: uPlot.Series) => void)
-		| null = null;
-
-	const removeSetData = jest.fn();
-	const removeSetSeries = jest.fn();
-
-	const addHook = jest.fn(
-		(
-			hookName: string,
-			handler: (plot: uPlot, ...args: unknown[]) => void,
-		): (() => void) => {
-			if (hookName === 'setData') {
-				setDataHandler = handler as (plot: uPlot) => void;
-				return removeSetData;
-			}
-			if (hookName === 'setSeries') {
-				setSeriesHandler = handler as (
-					plot: uPlot,
-					seriesIndex: number | null,
-					opts: uPlot.Series,
-				) => void;
-				return removeSetSeries;
-			}
-			return jest.fn();
-		},
-	);
-
-	const config: MockConfig = { addHook };
-
-	const invokeSetData = (plot: uPlot): void => {
-		setDataHandler?.(plot);
-	};
-
-	const invokeSetSeries = (
-		plot: uPlot,
-		seriesIndex: number | null,
-		opts: Partial<uPlot.Series> & { focus?: boolean },
-	): void => {
-		setSeriesHandler?.(plot, seriesIndex, opts as uPlot.Series);
-	};
-
-	return {
-		config,
-		invokeSetData,
-		invokeSetSeries,
-		removeSetData,
-		removeSetSeries,
-	};
-}
-
-function createMockPlot(overrides: Partial<uPlot> = {}): uPlot {
-	return {
-		data: [
-			[0, 1, 2],
-			[1, 2, 3],
-			[4, 5, 6],
-		],
-		series: [{ show: true }, { show: true }, { show: true }],
-		delBand: jest.fn(),
-		addBand: jest.fn(),
-		setData: jest.fn(),
-		...overrides,
-	} as unknown as uPlot;
-}
-
-describe('useBarChartStacking', () => {
-	it('returns data as-is when isStackedBarChart is false', () => {
-		const data: uPlot.AlignedData = [
-			[100, 200],
-			[1, 2],
-			[3, 4],
-		];
-		const { result } = renderHook(() =>
-			useBarChartStacking({
-				data,
-				isStackedBarChart: false,
-				config: null,
-			}),
-		);
-		expect(result.current).toBe(data);
-	});
-
-	it('returns data as-is when config is null and isStackedBarChart is true', () => {
-		const data: uPlot.AlignedData = [
-			[0, 1],
-			[1, 2],
-			[4, 5],
-		];
-		const { result } = renderHook(() =>
-			useBarChartStacking({
-				data,
-				isStackedBarChart: true,
-				config: null,
-			}),
-		);
-		// Still returns stacked data (computed in useMemo); no hooks registered
-		expect(result.current[0]).toStrictEqual([0, 1]);
-		expect(result.current[1]).toStrictEqual([5, 7]); // stacked
-		expect(result.current[2]).toStrictEqual([4, 5]);
-	});
-
-	it('returns stacked data when isStackedBarChart is true and multiple value series', () => {
-		const data: uPlot.AlignedData = [
-			[0, 1, 2],
-			[1, 2, 3],
-			[4, 5, 6],
-			[7, 8, 9],
-		];
-		const { result } = renderHook(() =>
-			useBarChartStacking({
-				data,
-				isStackedBarChart: true,
-				config: null,
-			}),
-		);
-		expect(result.current[0]).toStrictEqual([0, 1, 2]);
-		expect(result.current[1]).toStrictEqual([12, 15, 18]); // s1+s2+s3
-		expect(result.current[2]).toStrictEqual([11, 13, 15]); // s2+s3
-		expect(result.current[3]).toStrictEqual([7, 8, 9]);
-	});
-
-	it('returns data as-is when only one value series (no stacking needed)', () => {
-		const data: uPlot.AlignedData = [
-			[0, 1],
-			[1, 2],
-		];
-		const { result } = renderHook(() =>
-			useBarChartStacking({
-				data,
-				isStackedBarChart: true,
-				config: null,
-			}),
-		);
-		expect(result.current).toStrictEqual(data);
-	});
-
-	it('registers setData and setSeries hooks when isStackedBarChart and config provided', () => {
-		const { config } = createMockConfig();
-		const data: uPlot.AlignedData = [
-			[0, 1],
-			[1, 2],
-			[3, 4],
-		];
-
-		renderHook(() =>
-			useBarChartStacking({
-				data,
-				isStackedBarChart: true,
-				config: asConfig(config),
-			}),
-		);
-
-		expect(config.addHook).toHaveBeenCalledWith('setData', expect.any(Function));
-		expect(config.addHook).toHaveBeenCalledWith(
-			'setSeries',
-			expect.any(Function),
-		);
-	});
-
-	it('does not register hooks when isStackedBarChart is false', () => {
-		const { config } = createMockConfig();
-		const data: uPlot.AlignedData = [
-			[0, 1],
-			[1, 2],
-			[3, 4],
-		];
-
-		renderHook(() =>
-			useBarChartStacking({
-				data,
-				isStackedBarChart: false,
-				config: asConfig(config),
-			}),
-		);
-
-		expect(config.addHook).not.toHaveBeenCalled();
-	});
-
-	it('calls cleanup when unmounted', () => {
-		const { config, removeSetData, removeSetSeries } = createMockConfig();
-		const data: uPlot.AlignedData = [
-			[0, 1],
-			[1, 2],
-			[3, 4],
-		];
-
-		const { unmount } = renderHook(() =>
-			useBarChartStacking({
-				data,
-				isStackedBarChart: true,
-				config: asConfig(config),
-			}),
-		);
-
-		unmount();
-
-		expect(removeSetData).toHaveBeenCalled();
-		expect(removeSetSeries).toHaveBeenCalled();
-	});
-
-	it('re-stacks and updates plot when setData hook is invoked', () => {
-		const { config, invokeSetData } = createMockConfig();
-		const data: uPlot.AlignedData = [
-			[0, 1, 2],
-			[1, 2, 3],
-			[4, 5, 6],
-		];
-		const plot = createMockPlot({
-			data: [
-				[0, 1, 2],
-				[5, 7, 9],
-				[4, 5, 6],
-			],
-		});
-
-		renderHook(() =>
-			useBarChartStacking({
-				data,
-				isStackedBarChart: true,
-				config: asConfig(config),
-			}),
-		);
-
-		invokeSetData(plot);
-
-		expect(plot.delBand).toHaveBeenCalledWith(null);
-		expect(plot.addBand).toHaveBeenCalled();
-		expect(plot.setData).toHaveBeenCalledWith(
-			expect.arrayContaining([
-				[0, 1, 2],
-				expect.any(Array), // stacked row 1
-				expect.any(Array), // stacked row 2
-			]),
-		);
-	});
-
-	it('re-stacks when setSeries hook is invoked (e.g. legend toggle)', () => {
-		const { config, invokeSetSeries } = createMockConfig();
-		const data: uPlot.AlignedData = [
-			[0, 1],
-			[10, 20],
-			[5, 10],
-		];
-		// Plot data must match unstacked length so canApplyStacking passes
-		const plot = createMockPlot({
-			data: [
-				[0, 1],
-				[15, 30],
-				[5, 10],
-			],
-		});
-
-		renderHook(() =>
-			useBarChartStacking({
-				data,
-				isStackedBarChart: true,
-				config: asConfig(config),
-			}),
-		);
-
-		invokeSetSeries(plot, 1, { show: false });
-
-		expect(plot.setData).toHaveBeenCalled();
-	});
-
-	it('does not re-stack when setSeries is called with focus option', () => {
-		const { config, invokeSetSeries } = createMockConfig();
-		const data: uPlot.AlignedData = [
-			[0, 1],
-			[1, 2],
-			[3, 4],
-		];
-		const plot = createMockPlot();
-
-		renderHook(() =>
-			useBarChartStacking({
-				data,
-				isStackedBarChart: true,
-				config: asConfig(config),
-			}),
-		);
-
-		(plot.setData as jest.Mock).mockClear();
-		invokeSetSeries(plot, 1, { focus: true } as uPlot.Series);
-
-		expect(plot.setData).not.toHaveBeenCalled();
-	});
-});

frontend/src/container/DashboardContainer/visualization/panels/BarPanel/BarPanel.tsx

@@ -22,6 +22,7 @@ import { prepareBarPanelConfig } from './utils';
 import '../Panel.styles.scss';
 import TooltipFooter from '../components/TooltipFooter';
 import { prepareChartData } from 'lib/uPlotV2/utils/dataUtils';
+import { StackMode } from 'lib/uPlotV2/config/types';
 
 function BarPanel(props: PanelWrapperProps): JSX.Element {
 	const {
@@ -147,6 +148,7 @@ function BarPanel(props: PanelWrapperProps): JSX.Element {
 			{containerDimensions.width > 0 && containerDimensions.height > 0 && (
 				<BarChart
 					key={`${syncMode}-${syncFilterMode}`}
+					stack={widget.stackedBarChart ? StackMode.Normal : StackMode.None}
 					config={config}
 					legendConfig={{
 						position: widget?.legendPosition ?? LegendPosition.BOTTOM,
@@ -159,7 +161,6 @@ function BarPanel(props: PanelWrapperProps): JSX.Element {
 					height={containerDimensions.height}
 					layoutChildren={layoutChildren}
 					groupByPerQuery={groupByPerQuery}
-					isStackedBarChart={widget.stackedBarChart ?? false}
 					yAxisUnit={widget.yAxisUnit}
 					decimalPrecision={widget.decimalPrecision}
 					timezone={timezone}

frontend/src/container/DashboardContainer/visualization/panels/BarPanel/__tests__/utils.test.ts

@@ -35,20 +35,10 @@ jest.mock('lib/getLabelName', () => ({
 	),
 }));
 
-jest.mock(
-	'container/DashboardContainer/visualization/charts/utils/stackSeriesUtils',
-	() => ({
-		getInitialStackedBands: jest.fn().mockReturnValue([]),
-	}),
-);
-
 const getLegendMock = jest.requireMock('lib/dashboard/getQueryResults')
 	.getLegend as jest.Mock;
 const getLabelNameMock = jest.requireMock('lib/getLabelName')
 	.default as jest.Mock;
-const getInitialStackedBandsMock = jest.requireMock(
-	'container/DashboardContainer/visualization/charts/utils/stackSeriesUtils',
-).getInitialStackedBands as jest.Mock;
 
 const createApiResponse = (
 	result: MetricRangePayloadProps['data']['result'] = [],
@@ -247,36 +237,5 @@ describe('BarPanel utils', () => {
 			}).getConfig();
 			expect(config.series?.[1]).toMatchObject({ stroke: '#ff0000' });
 		});
-
-		it('calls getInitialStackedBands when widget is stackedBarChart', () => {
-			const widget = createWidget({ stackedBarChart: true });
-			const apiResponse = createApiResponse([
-				{
-					metric: {},
-					queryName: 'Q1',
-					values: [[1000, '1']],
-				} as MetricRangePayloadProps['data']['result'][0],
-				{
-					metric: {},
-					queryName: 'Q2',
-					values: [[1000, '2']],
-				} as MetricRangePayloadProps['data']['result'][0],
-			]);
-			prepareBarPanelConfig({ ...baseParams, widget, apiResponse });
-			// seriesCount = result.length + 1 = 3
-			expect(getInitialStackedBandsMock).toHaveBeenCalledWith(3);
-		});
-
-		it('does not call getInitialStackedBands for non-stacked chart', () => {
-			const apiResponse = createApiResponse([
-				{
-					metric: {},
-					queryName: 'Q1',
-					values: [[1000, '1']],
-				} as MetricRangePayloadProps['data']['result'][0],
-			]);
-			prepareBarPanelConfig({ ...baseParams, apiResponse });
-			expect(getInitialStackedBandsMock).not.toHaveBeenCalled();
-		});
 	});
 });

frontend/src/container/DashboardContainer/visualization/panels/BarPanel/utils.ts

@@ -1,7 +1,6 @@
 import { ExecStats } from 'api/v5/v5';
 import { Timezone } from 'components/CustomTimePicker/timezoneUtils';
 import { PANEL_TYPES } from 'constants/queryBuilder';
-import { getInitialStackedBands } from 'container/DashboardContainer/visualization/charts/utils/stackSeriesUtils';
 import { getLegend } from 'lib/dashboard/getQueryResults';
 import getLabelName from 'lib/getLabelName';
 import { OnClickPluginOpts } from 'lib/uPlotLib/plugins/onClickPlugin';
@@ -69,11 +68,6 @@ export function prepareBarPanelConfig({
 		return builder;
 	}
 
-	if (widget.stackedBarChart) {
-		const seriesCount = (apiResponse.data.result.length ?? 0) + 1; // +1 for 1-based uPlot series indices
-		builder.setBands(getInitialStackedBands(seriesCount));
-	}
-
 	apiResponse.data.result.forEach((series) => {
 		const baseLabelName = getLabelName(
 			series.metric,

frontend/src/container/MeterExplorer/Explorer/TimeSeries.tsx

@@ -9,6 +9,7 @@ import { useIsDarkMode } from 'hooks/useDarkMode';
 import { useResizeObserver } from 'hooks/useDimensions';
 import useUrlYAxisUnit from 'hooks/useUrlYAxisUnit';
 import { LegendPosition } from 'lib/uPlotV2/components/types';
+import { StackMode } from 'lib/uPlotV2/config/types';
 import { prepareChartData } from 'lib/uPlotV2/utils/dataUtils';
 import { useTimezone } from 'providers/Timezone';
 import { AppState } from 'store/reducers';
@@ -137,6 +138,7 @@ function TimeSeries({
 									key={`${WIDGET_ID}-${index}`}
 								>
 									<BarChart
+										stack={StackMode.Normal}
 										config={chart.config}
 										legendConfig={{
 											position: LegendPosition.BOTTOM,
@@ -144,7 +146,6 @@ function TimeSeries({
 										data={chart.chartData as uPlot.AlignedData}
 										width={containerDimensions.width}
 										height={containerDimensions.height}
-										isStackedBarChart
 										yAxisUnit={yAxisUnit || 'short'}
 										timezone={timezone}
 									/>

frontend/src/container/MeterExplorer/Explorer/configBuilder.ts

@@ -1,6 +1,5 @@
 import { Timezone } from 'components/CustomTimePicker/timezoneUtils';
 import { PANEL_TYPES } from 'constants/queryBuilder';
-import { getInitialStackedBands } from 'container/DashboardContainer/visualization/charts/utils/stackSeriesUtils';
 import { getLegend } from 'lib/dashboard/getQueryResults';
 import getLabelName from 'lib/getLabelName';
 import {
@@ -89,9 +88,6 @@ export function buildMeterChartConfig({
 		return builder;
 	}
 
-	const seriesCount = (apiResponse.data.result.length ?? 0) + 1;
-	builder.setBands(getInitialStackedBands(seriesCount));
-
 	apiResponse.data.result.forEach((series) => {
 		const baseLabelName = getLabelName(
 			series.metric,

frontend/src/lib/uPlotV2/components/Tooltip/BarChartTooltip.tsx

@@ -9,6 +9,7 @@ export default function BarChartTooltip(props: BarTooltipProps): JSX.Element {
 		(): TooltipContentItem[] =>
 			buildTooltipContent({
 				data: props.uPlotInstance.data,
+				unstackedData: props.unstackedData,
 				series: props.uPlotInstance.series,
 				dataIndexes: props.dataIndexes,
 				activeSeriesIndex: props.seriesIndex,
@@ -21,6 +22,7 @@ export default function BarChartTooltip(props: BarTooltipProps): JSX.Element {
 			}),
 		[
 			props.uPlotInstance,
+			props.unstackedData,
 			props.seriesIndex,
 			props.dataIndexes,
 			props.yAxisUnit,

frontend/src/lib/uPlotV2/components/Tooltip/TimeSeriesTooltip.tsx

@@ -11,6 +11,7 @@ export default function TimeSeriesTooltip(
 		(): TooltipContentItem[] =>
 			buildTooltipContent({
 				data: props.uPlotInstance.data,
+				unstackedData: props.unstackedData,
 				series: props.uPlotInstance.series,
 				dataIndexes: props.dataIndexes,
 				activeSeriesIndex: props.seriesIndex,
@@ -22,6 +23,7 @@ export default function TimeSeriesTooltip(
 			}),
 		[
 			props.uPlotInstance,
+			props.unstackedData,
 			props.seriesIndex,
 			props.dataIndexes,
 			props.yAxisUnit,

frontend/src/lib/uPlotV2/components/Tooltip/__tests__/utils.test.ts

@@ -72,6 +72,35 @@ describe('Tooltip utils', () => {
 			expect(result).toBe(20);
 		});
 
+		it('reports the pre-stack value, identically for normal and percent', () => {
+			const unstackedData: AlignedData = [[0], [30], [10]];
+			const series = [{}, { show: true }, { show: true }] as Series[];
+			const read = (data: AlignedData): number | null =>
+				getTooltipBaseValue({
+					data,
+					unstackedData,
+					index: 1,
+					dataIndex: 0,
+					isStackedBarChart: true,
+					series,
+				});
+
+			expect(read([[0], [40], [10]])).toBe(30);
+			expect(read([[0], [100], [25]])).toBe(30);
+		});
+
+		it('falls back to subtraction when no pre-stack data is given', () => {
+			const result = getTooltipBaseValue({
+				data: [[0], [40], [10]],
+				index: 1,
+				dataIndex: 0,
+				isStackedBarChart: true,
+				series: [{}, { show: true }, { show: true }] as Series[],
+			});
+
+			expect(result).toBe(30);
+		});
+
 		it('returns null when value is missing', () => {
 			const data: AlignedData = [
 				[0, 1],

frontend/src/lib/uPlotV2/components/Tooltip/utils.ts

@@ -23,17 +23,25 @@ export function resolveSeriesColor(
 
 export function getTooltipBaseValue({
 	data,
+	unstackedData,
 	index,
 	dataIndex,
 	isStackedBarChart,
 	series,
 }: {
 	data: AlignedData;
+	unstackedData?: AlignedData;
 	index: number;
 	dataIndex: number;
 	isStackedBarChart?: boolean;
 	series?: Series[];
 }): number | null {
+	// The subtraction below only recovers the raw value under `normal` stacking.
+	const unstackedSeries = unstackedData?.[index];
+	if (unstackedSeries) {
+		return unstackedSeries[dataIndex] ?? null;
+	}
+
 	let baseValue = data[index][dataIndex] ?? null;
 	// Top-down stacking (first series at top): raw = stacked[i] - stacked[nextVisible].
 	// When series are hidden, we must use the next *visible* series, not index+1,
@@ -56,6 +64,7 @@ export function getTooltipBaseValue({
 
 export function buildTooltipContent({
 	data,
+	unstackedData,
 	series,
 	dataIndexes,
 	activeSeriesIndex,
@@ -67,6 +76,7 @@ export function buildTooltipContent({
 	syncFilterMode,
 }: {
 	data: AlignedData;
+	unstackedData?: AlignedData;
 	series: Series[];
 	dataIndexes: Array<number | null>;
 	activeSeriesIndex: number | null;
@@ -115,6 +125,7 @@ export function buildTooltipContent({
 
 		const baseValue = getTooltipBaseValue({
 			data,
+			unstackedData,
 			index: seriesIndex,
 			dataIndex,
 			isStackedBarChart,

frontend/src/lib/uPlotV2/components/types.ts

@@ -69,6 +69,11 @@ export interface TooltipRenderArgs {
 	syncedSeriesIndexes?: number[] | null;
 	/** Receiver-side filter mode for the synced tooltip. Defaults to Filtered. */
 	syncFilterMode?: SyncTooltipFilterMode;
+	/**
+	 * Pre-stack values, injected by `ChartWrapper`. `Percent` discards the column total,
+	 * so the raw value cannot be recovered from the plot's own cumulative data.
+	 */
+	unstackedData?: uPlot.AlignedData;
 }
 
 export interface IRenderTooltipFooterArgs {

frontend/src/lib/uPlotV2/config/UPlotConfigBuilder.ts

@@ -20,6 +20,7 @@ import {
 	ConfigBuilderProps,
 	LegendItem,
 	SelectionPreferencesSource,
+	StackMode,
 } from './types';
 import { AxisProps, UPlotAxisBuilder } from './UPlotAxisBuilder';
 import { ScaleProps, UPlotScaleBuilder } from './UPlotScaleBuilder';
@@ -28,6 +29,11 @@ import { SeriesProps, UPlotSeriesBuilder } from './UPlotSeriesBuilder';
 /**
  * Type definitions for uPlot option objects
  */
+/** Renders a 0–100 number as `50%`, unlike the 0–1 `percentunit`. */
+const PERCENT_AXIS_UNIT = 'percent';
+
+const PERCENT_AXIS_MAX = 100;
+
 type LegendConfig = {
 	show?: boolean;
 	live?: boolean;
@@ -57,6 +63,8 @@ export class UPlotConfigBuilder extends ConfigBuilder<
 
 	private bands: uPlot.Band[] = [];
 
+	private stack: StackMode = StackMode.None;
+
 	private cursor: Cursor | undefined;
 
 	private hooks: Hooks.Arrays = {};
@@ -143,6 +151,15 @@ export class UPlotConfigBuilder extends ConfigBuilder<
 		this.axes[scaleKey] = new UPlotAxisBuilder(props);
 	}
 
+	/** Drives the fill bands, the percent axis unit and the percent range below. */
+	setStack(stack: StackMode): void {
+		this.stack = stack;
+	}
+
+	getStackMode(): StackMode {
+		return this.stack;
+	}
+
 	/**
 	 * Add or merge a scale configuration
 	 */
@@ -211,6 +228,41 @@ export class UPlotConfigBuilder extends ConfigBuilder<
 		this.bands = bands;
 	}
 
+	/**
+	 * The panel's own limits are in the source unit, which means nothing once values are
+	 * normalised. Soft rather than hard, so mixed-sign shares outside 0–100 stay visible.
+	 */
+	private resolveScale(scale: UPlotScaleBuilder): UPlotScaleBuilder {
+		if (this.stack !== StackMode.Percent || scale.props.scaleKey !== 'y') {
+			return scale;
+		}
+		return new UPlotScaleBuilder({
+			...scale.props,
+			min: undefined,
+			max: undefined,
+			softMin: 0,
+			softMax: PERCENT_AXIS_MAX,
+			// Thresholds still draw, but a 500ms one must not stretch the axis to 0–500.
+			thresholds: undefined,
+		});
+	}
+
+	/** Explicit bands win; otherwise a stack fills between consecutive series. */
+	private resolveBands(): uPlot.Band[] | undefined {
+		if (this.bands.length > 0) {
+			return this.bands;
+		}
+		if (this.stack === StackMode.None || this.series.length < 2) {
+			return undefined;
+		}
+		return (
+			this.series
+				.slice(0, -1)
+				// uPlot series are 1-based (index 0 is the timestamp axis).
+				.map((_, index) => ({ series: [index + 1, index + 2] as [number, number] }))
+		);
+	}
+
 	/**
 	 * Set cursor configuration
 	 */
@@ -444,9 +496,19 @@ export class UPlotConfigBuilder extends ConfigBuilder<
 				};
 			}),
 		];
-		config.axes = Object.values(this.axes).map((a) => a.getConfig());
+		config.axes = Object.entries(this.axes).map(([scaleKey, axis]) => {
+			if (scaleKey !== 'y' || this.stack !== StackMode.Percent) {
+				return axis.getConfig();
+			}
+			// Ticks read as percentages; the panel unit still applies to tooltips and
+			// thresholds, so build from a copy rather than touching the axis props.
+			return new UPlotAxisBuilder({
+				...axis.props,
+				yAxisUnit: PERCENT_AXIS_UNIT,
+			}).getConfig();
+		});
 		config.scales = this.scales.reduce(
-			(acc, s) => ({ ...acc, ...s.getConfig() }),
+			(acc, s) => ({ ...acc, ...this.resolveScale(s).getConfig() }),
 			{} as Record<string, uPlot.Scale>,
 		);
 
@@ -456,7 +518,7 @@ export class UPlotConfigBuilder extends ConfigBuilder<
 		config.cursor = this.getCursorConfig();
 		config.tzDate = this.tzDate;
 		config.plugins = this.plugins.length > 0 ? this.plugins : undefined;
-		config.bands = this.bands.length > 0 ? this.bands : undefined;
+		config.bands = this.resolveBands();
 
 		if (Array.isArray(this.padding)) {
 			config.padding = this.padding;

frontend/src/lib/uPlotV2/config/__tests__/UPlotConfigBuilder.test.ts

@@ -5,7 +5,7 @@ import {
 	STEP_INTERVAL_MULTIPLIER,
 } from '../../constants';
 import type { SeriesProps } from '../types';
-import { DrawStyle, SelectionPreferencesSource } from '../types';
+import { DrawStyle, SelectionPreferencesSource, StackMode } from '../types';
 import { UPlotConfigBuilder } from '../UPlotConfigBuilder';
 
 // Mock only the real boundary that hits localStorage
@@ -496,3 +496,161 @@ describe('UPlotConfigBuilder', () => {
 		expect(config.bands).toBeUndefined();
 	});
 });
+
+describe('UPlotConfigBuilder stacking', () => {
+	beforeEach(() => {
+		jest.clearAllMocks();
+		getStoredSeriesVisibilityMock.getStoredSeriesVisibility.mockReturnValue([]);
+	});
+
+	/**
+	 * Soft limits end up captured in the scale's range closure, so the only way to read
+	 * them back is to run it and inspect the range config it hands uPlot.
+	 */
+	function scaleSoftLimits(
+		builder: UPlotConfigBuilder,
+		scaleKey: string,
+	): { min: number; max: number } {
+		const rangeNum = jest.fn().mockReturnValue([0, 0]);
+		(uPlot as unknown as { rangeNum: unknown }).rangeNum = rangeNum;
+
+		const range = builder.getConfig().scales?.[scaleKey]?.range as (
+			u: unknown,
+			min: number,
+			max: number,
+			key: string,
+		) => void;
+		range({ scales: { [scaleKey]: { distr: 1 } } }, 40, 60, scaleKey);
+
+		const [, , rangeConfig] = rangeNum.mock.calls[0] as [
+			number,
+			number,
+			{ min: { soft: number }; max: { soft: number } },
+		];
+		return { min: rangeConfig.min.soft, max: rangeConfig.max.soft };
+	}
+
+	/** Renders y-axis ticks the way uPlot would, so unit formatting is observable. */
+	function yAxisTicks(builder: UPlotConfigBuilder, ticks: number[]): string[] {
+		const yAxis = builder.getConfig().axes?.find((a) => a.scale === 'y');
+		const values = yAxis?.values as (
+			u: unknown,
+			splits: number[],
+		) => (string | null)[];
+		return values(null, ticks).map((v) => String(v));
+	}
+
+	function builderFor(stack?: StackMode, seriesCount = 3): UPlotConfigBuilder {
+		const builder = new UPlotConfigBuilder({ id: 'stack-test' });
+		if (stack) {
+			builder.setStack(stack);
+		}
+		builder.addAxis({ scaleKey: 'y', show: true, side: 3, yAxisUnit: 'ms' });
+		for (let i = 0; i < seriesCount; i++) {
+			builder.addSeries({
+				scaleKey: 'y',
+				label: `S${i}`,
+				drawStyle: DrawStyle.Bar,
+				colorMapping: {},
+				isDarkMode: false,
+			} as SeriesProps);
+		}
+		return builder;
+	}
+
+	it('defaults to no stacking, so no bands and the panel unit on the axis', () => {
+		const builder = builderFor();
+
+		expect(builder.getStackMode()).toBe('none');
+		expect(builder.getConfig().bands).toBeUndefined();
+		expect(yAxisTicks(builder, [1000])).toStrictEqual(['1 s']);
+	});
+
+	it('derives one band per adjacent series pair once a stack is declared', () => {
+		expect(builderFor(StackMode.Normal).getConfig().bands).toStrictEqual([
+			{ series: [1, 2] },
+			{ series: [2, 3] },
+		]);
+	});
+
+	it('emits no bands for a single series', () => {
+		expect(builderFor(StackMode.Normal, 1).getConfig().bands).toBeUndefined();
+	});
+
+	it('keeps the panel unit on the axis for a normal stack', () => {
+		expect(yAxisTicks(builderFor(StackMode.Normal), [1000])).toStrictEqual([
+			'1 s',
+		]);
+	});
+
+	it('formats the axis as percentages for a percent stack', () => {
+		expect(yAxisTicks(builderFor(StackMode.Percent), [0, 50, 100])).toStrictEqual(
+			['0%', '50%', '100%'],
+		);
+	});
+
+	it('leaves other axes on their own unit under a percent stack', () => {
+		const builder = builderFor(StackMode.Percent);
+		builder.addAxis({ scaleKey: 'x', show: true, side: 2 });
+
+		expect(builder.getConfig().axes?.map((a) => a.scale)).toStrictEqual([
+			'y',
+			'x',
+		]);
+	});
+
+	it('pins the y scale to the 0–100 band under a percent stack, dropping panel limits', () => {
+		const builder = new UPlotConfigBuilder({ id: 'stack-scale' });
+		builder.setStack(StackMode.Percent);
+		builder.addScale({ scaleKey: 'y', softMin: 5, softMax: 500 });
+
+		// Soft, not hard: mixed-sign shares fall outside 0–100 and must stay visible.
+		expect(builder.getConfig().scales?.y).toMatchObject({ auto: true });
+		expect(scaleSoftLimits(builder, 'y')).toStrictEqual({ min: 0, max: 100 });
+	});
+
+	it('leaves the panel limits alone when the stack is not percent', () => {
+		const builder = new UPlotConfigBuilder({ id: 'stack-scale' });
+		builder.setStack(StackMode.Normal);
+		builder.addScale({ scaleKey: 'y', softMin: 5, softMax: 500 });
+
+		expect(scaleSoftLimits(builder, 'y')).toStrictEqual({ min: 5, max: 500 });
+	});
+
+	it.each([StackMode.Normal, StackMode.Percent])(
+		'draws thresholds under a %s stack',
+		(stack) => {
+			const builder = new UPlotConfigBuilder({ id: 'stack-thr' });
+			builder.setStack(stack);
+			builder.addThresholds({
+				scaleKey: 'y',
+				thresholds: [{ thresholdValue: 500, thresholdColor: 'red' }],
+				yAxisUnit: 'ms',
+			});
+
+			expect(builder.getConfig().hooks?.draw).toHaveLength(1);
+		},
+	);
+
+	it('keeps a source-unit threshold from stretching the percent band', () => {
+		const builder = new UPlotConfigBuilder({ id: 'stack-thr' });
+		builder.setStack(StackMode.Percent);
+		const thresholds = {
+			scaleKey: 'y',
+			thresholds: [{ thresholdValue: 500, thresholdColor: 'red' }],
+			yAxisUnit: 'ms',
+		};
+		builder.addThresholds(thresholds);
+		builder.addScale({ scaleKey: 'y', thresholds });
+
+		// Without this the 500ms threshold would widen a percentage axis to 0–500.
+		expect(scaleSoftLimits(builder, 'y')).toStrictEqual({ min: 0, max: 100 });
+	});
+
+	it('lets explicit bands win over the derived ones', () => {
+		const builder = builderFor(StackMode.Normal);
+		builder.setBands([{ series: [1, 3] }]);
+
+		expect(builder.getConfig().bands).toStrictEqual([{ series: [1, 3] }]);
+	});
+});

frontend/src/lib/uPlotV2/config/types.ts

@@ -33,6 +33,13 @@ export enum SelectionPreferencesSource {
 /**
  * Props for configuring the uPlot config builder
  */
+/** `Percent` rescales each x-slice to its column total, so every column fills to 100. */
+export enum StackMode {
+	None = 'none',
+	Normal = 'normal',
+	Percent = 'percent',
+}
+
 export interface ConfigBuilderProps {
 	id: string;
 	onDragSelect?: (startTime: number, endTime: number) => void;

frontend/src/lib/uPlotV2/utils/__tests__/dataUtils.test.ts

@@ -281,3 +281,20 @@ describe('dataUtils', () => {
 		});
 	});
 });
+
+describe('insertLargeGapNullsIntoAlignedData index alignment', () => {
+	// ChartWrapper gap-processes the pre-stack series to keep tooltip indices aligned;
+	// that only holds because insertions are decided from the x axis, never from y.
+	it('inserts at the same positions regardless of the y values', () => {
+		const x = [0, 100, 200];
+		const options = [{ spanGaps: 50 }];
+		const raw = [x, [1, 2, 3]] as uPlot.AlignedData;
+		const stacked = [x, [10, 20, 30]] as uPlot.AlignedData;
+
+		const fromRaw = insertLargeGapNullsIntoAlignedData(raw, options);
+		const fromStacked = insertLargeGapNullsIntoAlignedData(stacked, options);
+
+		expect(fromRaw[0]).toStrictEqual(fromStacked[0]);
+		expect(fromRaw[1]).toHaveLength((fromStacked[1] as unknown[]).length);
+	});
+});

frontend/src/pages/DashboardPageV2/DashboardContainer/Panels/kinds/BarChartPanel/Renderer.tsx

@@ -7,6 +7,7 @@ import { PanelMode } from 'container/DashboardContainer/visualization/panels/typ
 import { useIsDarkMode } from 'hooks/useDarkMode';
 import { useResizeObserver } from 'hooks/useDimensions';
 import { IRenderTooltipFooterArgs } from 'lib/uPlotV2/components/types';
+import { StackMode } from 'lib/uPlotV2/config/types';
 import {
 	flattenTimeSeries,
 	getExecStats,
@@ -219,7 +220,9 @@ function BarPanelRenderer({
 						height={containerDimensions.height}
 						syncMode={dashboardPreference?.syncMode}
 						syncFilterMode={dashboardPreference?.syncFilterMode}
-						isStackedBarChart={spec.visualization?.stackedBarChart ?? false}
+						stack={
+							spec.visualization?.stackedBarChart ? StackMode.Normal : StackMode.None
+						}
 						renderTooltipFooter={renderTooltipFooter}
 						onClick={enableDrillDown ? handleChartClick : undefined}
 					/>

frontend/src/pages/DashboardPageV2/DashboardContainer/Panels/kinds/BarChartPanel/utils/buildConfig.ts

@@ -1,7 +1,6 @@
 import type { DashboardtypesBarChartPanelSpecDTO } from 'api/generated/services/sigNoz.schemas';
 import { Timezone } from 'components/CustomTimePicker/timezoneUtils';
 import { PANEL_TYPES } from 'constants/queryBuilder';
-import { getInitialStackedBands } from 'container/DashboardContainer/visualization/charts/utils/stackSeriesUtils';
 import { PanelMode } from 'container/DashboardContainer/visualization/panels/types';
 import { buildBaseConfig } from 'pages/DashboardPageV2/DashboardContainer/Panels/utils/baseConfigBuilder';
 import { resolveSeriesLabelV5 } from 'pages/DashboardPageV2/DashboardContainer/Panels/utils/resolveSeriesLabel';
@@ -101,12 +100,6 @@ function addSeries({
 }: AddSeriesArgs): void {
 	const colorMapping = spec.legend?.customColors ?? {};
 
-	if (spec.visualization?.stackedBarChart) {
-		// uPlot uses 1-based series indices (index 0 is the timestamp axis);
-		// `+1` keeps the band targets aligned with the series we're about to add.
-		builder.setBands(getInitialStackedBands(series.length + 1));
-	}
-
 	series.forEach((s) => {
 		const baseLabel = getLabelName(s.labels, s.queryName, s.legend);
 		const label = resolveSeriesLabelV5(s, builderQueries, baseLabel);