feat(dashboards-v2): reactive threshold editing with live preview

Threshold edits now stream to the spec as the user types, so the panel preview
reflects them before Save. The per-row draft is mirrored into the spec via an
onLiveChange effect in useThresholdDraft; because edits reach the spec live,
ThresholdsSection snapshots the saved value on edit entry and restores it on
Discard. Save keeps the value, Discard rolls back, and add-then-discard still
removes the row.

frontend/src/components/YAxisUnitSelector/YAxisUnitSelector.tsx

@@ -2,7 +2,7 @@ import { useMemo } from 'react';
 import { SolidAlertTriangle } from '@signozhq/icons';
 import { Select, Tooltip } from 'antd';
 import type { DefaultOptionType } from 'antd/es/select';
-import classNames from 'classnames';
+import cx from 'classnames';
 
 import { UniversalYAxisUnitMappings } from './constants';
 import { UniversalYAxisUnit, YAxisUnitSelectorProps } from './types';
@@ -72,9 +72,7 @@ function YAxisUnitSelector({
 	}, [categoriesOverride, source]);
 
 	return (
-		<div
-			className={classNames('y-axis-unit-selector-component', containerClassName)}
-		>
+		<div className={cx('y-axis-unit-selector-component', containerClassName)}>
 			<Select
 				showSearch
 				value={universalUnit}
@@ -84,12 +82,17 @@ function YAxisUnitSelector({
 				loading={loading}
 				suffixIcon={
 					incompatibleUnitMessage ? (
-						<Tooltip title={incompatibleUnitMessage}>
-							<SolidAlertTriangle role="img" aria-label="warning" size="md" />
+						<Tooltip
+							title={incompatibleUnitMessage}
+							overlayClassName="y-axis-unit-warning-tooltip"
+						>
+							<span className="y-axis-unit-warning" role="img" aria-label="warning">
+								<SolidAlertTriangle size="md" />
+							</span>
 						</Tooltip>
 					) : undefined
 				}
-				className={classNames({
+				className={cx({
 					'warning-state': incompatibleUnitMessage,
 				})}
 				data-testid={dataTestId}

frontend/src/components/YAxisUnitSelector/__tests__/YAxisUnitSelector.test.tsx

@@ -1,4 +1,5 @@
-import { fireEvent, render, screen } from '@testing-library/react';
+import { render, screen } from '@testing-library/react';
+import userEvent from '@testing-library/user-event';
 
 import { YAxisCategoryNames } from '../constants';
 import { UniversalYAxisUnit, YAxisSource } from '../types';
@@ -6,9 +7,13 @@ import YAxisUnitSelector from '../YAxisUnitSelector';
 
 describe('YAxisUnitSelector', () => {
 	const mockOnChange = jest.fn();
+	// antd injects its `pointer-events` styles via cssinjs in jsdom, but the SCSS
+	// overrides aren't loaded — skip the pointer-events check so hovers/clicks register.
+	let user: ReturnType<typeof userEvent.setup>;
 
 	beforeEach(() => {
 		mockOnChange.mockClear();
+		user = userEvent.setup({ pointerEventsCheck: 0 });
 	});
 
 	it('renders with default placeholder', () => {
@@ -34,7 +39,7 @@ describe('YAxisUnitSelector', () => {
 		expect(screen.queryByText('Custom placeholder')).toBeInTheDocument();
 	});
 
-	it('calls onChange when a value is selected', () => {
+	it('calls onChange when a value is selected', async () => {
 		render(
 			<YAxisUnitSelector
 				value=""
@@ -44,9 +49,8 @@ describe('YAxisUnitSelector', () => {
 		);
 		const select = screen.getByRole('combobox');
 
-		fireEvent.mouseDown(select);
-		const option = screen.getByText('Bytes (B)');
-		fireEvent.click(option);
+		await user.click(select);
+		await user.click(screen.getByText('Bytes (B)'));
 
 		expect(mockOnChange).toHaveBeenCalledWith('By', {
 			children: 'Bytes (B)',
@@ -55,7 +59,7 @@ describe('YAxisUnitSelector', () => {
 		});
 	});
 
-	it('filters options based on search input', () => {
+	it('filters options based on search input', async () => {
 		render(
 			<YAxisUnitSelector
 				value=""
@@ -65,14 +69,13 @@ describe('YAxisUnitSelector', () => {
 		);
 		const select = screen.getByRole('combobox');
 
-		fireEvent.mouseDown(select);
-		const input = screen.getByRole('combobox');
-		fireEvent.change(input, { target: { value: 'bytes/sec' } });
+		await user.click(select);
+		await user.type(select, 'bytes/sec');
 
 		expect(screen.getByText('Bytes/sec')).toBeInTheDocument();
 	});
 
-	it('shows all categories and their units', () => {
+	it('shows all categories and their units', async () => {
 		render(
 			<YAxisUnitSelector
 				value=""
@@ -80,9 +83,8 @@ describe('YAxisUnitSelector', () => {
 				source={YAxisSource.ALERTS}
 			/>,
 		);
-		const select = screen.getByRole('combobox');
 
-		fireEvent.mouseDown(select);
+		await user.click(screen.getByRole('combobox'));
 
 		// Check for category headers
 		expect(screen.getByText('Data')).toBeInTheDocument();
@@ -93,7 +95,7 @@ describe('YAxisUnitSelector', () => {
 		expect(screen.getByText('Seconds (s)')).toBeInTheDocument();
 	});
 
-	it('shows warning message when incompatible unit is selected', () => {
+	it('shows warning message when incompatible unit is selected', async () => {
 		render(
 			<YAxisUnitSelector
 				source={YAxisSource.ALERTS}
@@ -104,12 +106,12 @@ describe('YAxisUnitSelector', () => {
 		);
 		const warningIcon = screen.getByLabelText('warning');
 		expect(warningIcon).toBeInTheDocument();
-		fireEvent.mouseOver(warningIcon);
-		return screen
-			.findByText(
+		await user.hover(warningIcon);
+		await expect(
+			screen.findByText(
 				'Unit mismatch. The metric was sent with unit Seconds (s), but Bytes (B) is selected.',
-			)
-			.then((el) => expect(el).toBeInTheDocument());
+			),
+		).resolves.toBeInTheDocument();
 	});
 
 	it('does not show warning message when compatible unit is selected', () => {
@@ -125,7 +127,7 @@ describe('YAxisUnitSelector', () => {
 		expect(warningIcon).not.toBeInTheDocument();
 	});
 
-	it('uses categories override to render custom units', () => {
+	it('uses categories override to render custom units', async () => {
 		const customCategories = [
 			{
 				name: YAxisCategoryNames.Data,
@@ -147,9 +149,7 @@ describe('YAxisUnitSelector', () => {
 			/>,
 		);
 
-		const select = screen.getByRole('combobox');
-
-		fireEvent.mouseDown(select);
+		await user.click(screen.getByRole('combobox'));
 
 		expect(screen.getByText('Custom Bytes (B)')).toBeInTheDocument();
 		expect(screen.queryByText('Bytes (B)')).not.toBeInTheDocument();

frontend/src/components/YAxisUnitSelector/styles.scss

@@ -4,6 +4,13 @@
 	}
 }
 
+// Re-enable hover on the warning icon: its `.ant-select-arrow` parent sets
+// `pointer-events: none`, which would otherwise suppress the tooltip.
+.y-axis-unit-warning {
+	display: inline-flex;
+	pointer-events: auto;
+}
+
 .warning-state {
 	.ant-select-selector {
 		border-color: var(--bg-amber-400) !important;
@@ -17,3 +24,7 @@
 		right: 28px;
 	}
 }
+
+.y-axis-unit-warning-tooltip {
+	max-width: 240px;
+}

frontend/src/pages/DashboardPageV2/DashboardContainer/PanelEditor/ConfigPane/ConfigPane.tsx

@@ -32,6 +32,8 @@ interface ConfigPaneProps {
 	tableColumns: TableColumnOption[];
 	/** Query step interval (seconds), for the chart-appearance span-gaps floor. */
 	stepInterval?: number;
+	/** Unit the selected metric was sent with; drives the unit selector's mismatch warning. */
+	metricUnit?: string;
 }
 
 /**
@@ -49,6 +51,7 @@ function ConfigPane({
 	legendSeries,
 	tableColumns,
 	stepInterval,
+	metricUnit,
 }: ConfigPaneProps): JSX.Element {
 	const definition = getPanelDefinition(panelKind);
 	const sections = definition.sections;
@@ -108,6 +111,7 @@ function ConfigPane({
 									onChangePanelKind={onChangePanelKind}
 									queryType={queryType}
 									stepInterval={stepInterval}
+									metricUnit={metricUnit}
 								/>
 							))}
 						</div>

frontend/src/pages/DashboardPageV2/DashboardContainer/PanelEditor/ConfigPane/SectionSlot/SectionSlot.tsx

@@ -34,6 +34,7 @@ function SectionSlot({
 	onChangePanelKind,
 	queryType,
 	stepInterval,
+	metricUnit,
 }: SectionSlotProps): JSX.Element | null {
 	// A kind can hide a section based on current spec state (e.g. Histogram legend once
 	// queries are merged) — skip it before resolving the editor.
@@ -74,6 +75,7 @@ function SectionSlot({
 				onChangePanelKind={onChangePanelKind}
 				queryType={queryType}
 				stepInterval={stepInterval}
+				metricUnit={metricUnit}
 			/>
 		</SettingsSection>
 	);

frontend/src/pages/DashboardPageV2/DashboardContainer/PanelEditor/ConfigPane/sectionContext.ts

@@ -19,4 +19,6 @@ export interface SectionEditorContext {
 	yAxisUnit?: string;
 	queryType?: EQueryType;
 	stepInterval?: number;
+	/** Unit the selected metric was sent with; drives the unit selector's mismatch warning. */
+	metricUnit?: string;
 }

frontend/src/pages/DashboardPageV2/DashboardContainer/PanelEditor/ConfigPane/sections/ChartAppearanceSection/DisconnectValuesField.tsx

@@ -46,11 +46,10 @@ function DisconnectValuesField({
 	onChange,
 }: DisconnectValuesFieldProps): JSX.Element {
 	const duration = value?.fillLessThan || undefined;
-	const isThreshold = !!duration;
-	// Remember the last threshold so toggling Never → Threshold restores it.
-	const [lastDuration, setLastDuration] = useState(
-		duration ?? defaultDuration(stepInterval),
-	);
+	// `fillOnlyBelow` is authoritative; fall back to a stored duration for legacy panels.
+	const isThreshold = value?.fillOnlyBelow ?? !!duration;
+	// Remember the last committed threshold so Never → Threshold restores it.
+	const [lastDuration, setLastDuration] = useState<string | undefined>(duration);
 
 	useEffect(() => {
 		if (duration) {
@@ -59,11 +58,17 @@ function DisconnectValuesField({
 	}, [duration]);
 
 	const handleMode = (mode: DisconnectValuesMode): void => {
-		onChange(
-			mode === DisconnectValuesMode.THRESHOLD
-				? { ...value, fillLessThan: lastDuration }
-				: undefined,
-		);
+		if (mode === DisconnectValuesMode.THRESHOLD) {
+			onChange({
+				...value,
+				fillOnlyBelow: true,
+				// Seed from the live stepInterval (async — undefined until results load), not mount.
+				fillLessThan: lastDuration ?? defaultDuration(stepInterval),
+			});
+			return;
+		}
+		// Never spans every gap; drop the duration so the renderer reads a clean "span all".
+		onChange({ ...value, fillOnlyBelow: false, fillLessThan: undefined });
 	};
 
 	return (
@@ -79,14 +84,16 @@ function DisconnectValuesField({
 					onChange={handleMode}
 				/>
 			</div>
-			{isThreshold && (
+			{isThreshold && duration && (
 				<div className={styles.field}>
 					<Typography.Text>Threshold value</Typography.Text>
 					<DisconnectValuesThresholdInput
 						testId={`${testId}-value`}
-						value={lastDuration}
+						value={duration}
 						minValue={stepInterval}
-						onChange={(next): void => onChange({ ...value, fillLessThan: next })}
+						onChange={(next): void =>
+							onChange({ ...value, fillOnlyBelow: true, fillLessThan: next })
+						}
 					/>
 				</div>
 			)}

frontend/src/pages/DashboardPageV2/DashboardContainer/PanelEditor/ConfigPane/sections/ChartAppearanceSection/DisconnectValuesThresholdInput.tsx

@@ -14,6 +14,28 @@ interface DisconnectValuesThresholdInputProps {
 	onChange: (duration: string) => void;
 }
 
+/**
+ * Inline error for a raw duration, or `null` when valid and in range. The parse is
+ * guarded: `isValidTimeSpan` passes some strings `intervalToSeconds` throws on (e.g. "5x").
+ */
+function validationError(raw: string, minValue?: number): string | null {
+	let seconds: number;
+	try {
+		seconds = rangeUtil.isValidTimeSpan(raw)
+			? rangeUtil.intervalToSeconds(raw)
+			: NaN;
+	} catch {
+		seconds = NaN;
+	}
+	if (!Number.isFinite(seconds) || seconds <= 0) {
+		return 'Enter a valid duration (e.g. 30s, 1m, 1h)';
+	}
+	if (minValue !== undefined && seconds < minValue) {
+		return `Threshold should be > ${rangeUtil.secondsToHms(minValue)}`;
+	}
+	return null;
+}
+
 /**
  * Duration input for the span-gaps threshold: shows/accepts and reports a human
  * duration ("30s", "1m", "1h"), which is the value stored verbatim in
@@ -36,24 +58,21 @@ function DisconnectValuesThresholdInput({
 		setError(null);
 	}, [value]);
 
+	// Validate live so an invalid entry surfaces immediately, not only on blur.
+	const handleText = (raw: string): void => {
+		setText(raw);
+		setError(raw ? validationError(raw, minValue) : null);
+	};
+
 	const commit = (raw: string): void => {
-		if (!raw) {
+		// Skip no-op commits: blur fires when clicking the Never toggle, and re-emitting
+		// the unchanged value there would race the toggle and snap back to Threshold.
+		if (!raw || raw === value) {
 			return;
 		}
-		let seconds: number;
-		try {
-			seconds = rangeUtil.isValidTimeSpan(raw)
-				? rangeUtil.intervalToSeconds(raw)
-				: NaN;
-		} catch {
-			seconds = NaN;
-		}
-		if (!Number.isFinite(seconds) || seconds <= 0) {
-			setError('Enter a valid duration (e.g. 30s, 1m, 1h)');
-			return;
-		}
-		if (minValue !== undefined && seconds < minValue) {
-			setError(`Threshold should be > ${rangeUtil.secondsToHms(minValue)}`);
+		const message = validationError(raw, minValue);
+		if (message) {
+			setError(message);
 			return;
 		}
 		setError(null);
@@ -69,12 +88,9 @@ function DisconnectValuesThresholdInput({
 				status={error ? 'error' : undefined}
 				prefix={<span className={styles.thresholdPrefix}>&gt;</span>}
 				value={text}
-				onChange={(e: ChangeEvent<HTMLInputElement>): void => {
-					setText(e.target.value);
-					if (error) {
-						setError(null);
-					}
-				}}
+				onChange={(e: ChangeEvent<HTMLInputElement>): void =>
+					handleText(e.target.value)
+				}
 				onBlur={(e): void => commit(e.currentTarget.value)}
 				onKeyDown={(e): void => {
 					if (e.key === 'Enter') {

frontend/src/pages/DashboardPageV2/DashboardContainer/PanelEditor/ConfigPane/sections/ChartAppearanceSection/__tests__/ChartAppearanceSection.test.tsx

@@ -1,9 +1,34 @@
+import { useState } from 'react';
 import { render, screen } from '@testing-library/react';
 import userEvent from '@testing-library/user-event';
-import { DashboardtypesLineStyleDTO } from 'api/generated/services/sigNoz.schemas';
+import {
+	DashboardtypesLineStyleDTO,
+	type DashboardtypesTimeSeriesChartAppearanceDTO,
+} from 'api/generated/services/sigNoz.schemas';
 
 import ChartAppearanceSection from '../ChartAppearanceSection';
 
+/** Stateful wrapper that feeds onChange back as the spec, mirroring the real editor. */
+function StatefulSpanGaps({
+	initial,
+	stepInterval,
+}: {
+	initial?: DashboardtypesTimeSeriesChartAppearanceDTO;
+	stepInterval?: number;
+}): JSX.Element {
+	const [value, setValue] = useState<
+		DashboardtypesTimeSeriesChartAppearanceDTO | undefined
+	>(initial);
+	return (
+		<ChartAppearanceSection
+			value={value}
+			controls={{ spanGaps: true }}
+			stepInterval={stepInterval}
+			onChange={setValue}
+		/>
+	);
+}
+
 // Open the antd Select by clicking its selector, then pick the option by label. The
 // line-style and fill-mode controls are ConfigSegmented (buttons), so this helper is
 // only used for the line-interpolation ConfigSelect.
@@ -139,7 +164,7 @@ describe('ChartAppearanceSection', () => {
 		await user.click(screen.getByText('Threshold'));
 
 		expect(onChange).toHaveBeenLastCalledWith({
-			spanGaps: { fillLessThan: '1m' },
+			spanGaps: { fillOnlyBelow: true, fillLessThan: '1m' },
 		});
 	});
 
@@ -162,7 +187,7 @@ describe('ChartAppearanceSection', () => {
 		await user.tab();
 
 		expect(onChange).toHaveBeenLastCalledWith({
-			spanGaps: { fillLessThan: '5m' },
+			spanGaps: { fillOnlyBelow: true, fillLessThan: '5m' },
 		});
 	});
 
@@ -183,7 +208,7 @@ describe('ChartAppearanceSection', () => {
 		await user.tab();
 
 		expect(onChange).toHaveBeenLastCalledWith({
-			spanGaps: { fillLessThan: '300' },
+			spanGaps: { fillOnlyBelow: true, fillLessThan: '300' },
 		});
 	});
 
@@ -200,7 +225,24 @@ describe('ChartAppearanceSection', () => {
 
 		await user.click(screen.getByText('Never'));
 
-		expect(onChange).toHaveBeenLastCalledWith({ spanGaps: undefined });
+		expect(onChange).toHaveBeenLastCalledWith({
+			spanGaps: { fillOnlyBelow: false, fillLessThan: undefined },
+		});
+	});
+
+	it('selects Never when fillOnlyBelow is false even if a duration lingers', () => {
+		render(
+			<ChartAppearanceSection
+				value={{ spanGaps: { fillOnlyBelow: false, fillLessThan: '1m' } }}
+				controls={{ spanGaps: true }}
+				onChange={jest.fn()}
+			/>,
+		);
+
+		// The flag is authoritative: a stale fillLessThan must not show Threshold.
+		expect(
+			screen.queryByTestId('panel-editor-v2-span-gaps-value'),
+		).not.toBeInTheDocument();
 	});
 
 	it('shows an error and does not commit an invalid duration', async () => {
@@ -244,4 +286,117 @@ describe('ChartAppearanceSection', () => {
 		expect(screen.getByText(/Threshold should be >/)).toBeInTheDocument();
 		expect(onChange).not.toHaveBeenCalled();
 	});
+
+	it('seeds the threshold from the step interval when switching to Threshold', async () => {
+		const user = userEvent.setup();
+		const onChange = jest.fn();
+		render(
+			<ChartAppearanceSection
+				value={undefined}
+				controls={{ spanGaps: true }}
+				stepInterval={300}
+				onChange={onChange}
+			/>,
+		);
+
+		await user.click(screen.getByText('Threshold'));
+
+		expect(onChange).toHaveBeenLastCalledWith({
+			spanGaps: { fillOnlyBelow: true, fillLessThan: '5m' },
+		});
+	});
+
+	it('seeds from the step interval even when it arrives after mount', async () => {
+		const user = userEvent.setup();
+		const onChange = jest.fn();
+		// The step interval is undefined until the query response carries step metadata,
+		// so the panel first renders without it and receives it on a later render.
+		const { rerender } = render(
+			<ChartAppearanceSection
+				value={undefined}
+				controls={{ spanGaps: true }}
+				onChange={onChange}
+			/>,
+		);
+		rerender(
+			<ChartAppearanceSection
+				value={undefined}
+				controls={{ spanGaps: true }}
+				stepInterval={300}
+				onChange={onChange}
+			/>,
+		);
+
+		await user.click(screen.getByText('Threshold'));
+
+		// Regression: a value seeded at mount would still be the 1m fallback.
+		expect(onChange).toHaveBeenLastCalledWith({
+			spanGaps: { fillOnlyBelow: true, fillLessThan: '5m' },
+		});
+	});
+
+	it('shows a validation error while typing, before blur', async () => {
+		const user = userEvent.setup();
+		render(
+			<ChartAppearanceSection
+				value={{ spanGaps: { fillLessThan: '1m' } }}
+				controls={{ spanGaps: true }}
+				onChange={jest.fn()}
+			/>,
+		);
+
+		const input = screen.getByTestId('panel-editor-v2-span-gaps-value');
+		await user.clear(input);
+		await user.type(input, 'abc');
+		// No blur / Enter — the error must already be visible.
+
+		expect(screen.getByText(/valid duration/i)).toBeInTheDocument();
+	});
+
+	it('does not re-commit the threshold when blurred without a change', async () => {
+		const user = userEvent.setup();
+		const onChange = jest.fn();
+		render(
+			<ChartAppearanceSection
+				value={{ spanGaps: { fillLessThan: '1m' } }}
+				controls={{ spanGaps: true }}
+				onChange={onChange}
+			/>,
+		);
+
+		const input = screen.getByTestId('panel-editor-v2-span-gaps-value');
+		await user.click(input);
+		await user.tab();
+
+		expect(onChange).not.toHaveBeenCalled();
+	});
+
+	it('fully switches from Threshold to Never (the input disappears)', async () => {
+		const user = userEvent.setup();
+		render(<StatefulSpanGaps initial={{ spanGaps: { fillLessThan: '1m' } }} />);
+
+		expect(
+			screen.getByTestId('panel-editor-v2-span-gaps-value'),
+		).toBeInTheDocument();
+
+		// Focus the input first so clicking Never also fires its blur (the toggle race).
+		await user.click(screen.getByTestId('panel-editor-v2-span-gaps-value'));
+		await user.click(screen.getByText('Never'));
+
+		expect(
+			screen.queryByTestId('panel-editor-v2-span-gaps-value'),
+		).not.toBeInTheDocument();
+	});
+
+	it('remembers the last threshold when toggling Never → Threshold', async () => {
+		const user = userEvent.setup();
+		render(<StatefulSpanGaps initial={{ spanGaps: { fillLessThan: '5m' } }} />);
+
+		await user.click(screen.getByText('Never'));
+		await user.click(screen.getByText('Threshold'));
+
+		expect(screen.getByTestId('panel-editor-v2-span-gaps-value')).toHaveValue(
+			'5m',
+		);
+	});
 });

frontend/src/pages/DashboardPageV2/DashboardContainer/PanelEditor/ConfigPane/sections/FormattingSection/FormattingSection.tsx

@@ -14,7 +14,7 @@ import ColumnUnits from './ColumnUnits';
 import styles from './FormattingSection.module.scss';
 
 type FormattingSectionProps = SectionEditorProps<SectionKind.Formatting> &
-	Pick<SectionEditorContext, 'tableColumns'>;
+	Pick<SectionEditorContext, 'tableColumns' | 'metricUnit'>;
 
 // `full` means "show the raw value, no rounding"; the digits round to that many places.
 const DECIMAL_OPTIONS: {
@@ -39,6 +39,7 @@ function FormattingSection({
 	controls,
 	onChange,
 	tableColumns = [],
+	metricUnit,
 }: FormattingSectionProps): JSX.Element {
 	return (
 		<>
@@ -50,6 +51,7 @@ function FormattingSection({
 						data-testid="panel-editor-v2-unit"
 						source={YAxisSource.DASHBOARDS}
 						value={value?.unit}
+						initialValue={metricUnit}
 						onChange={(unit): void => onChange({ ...value, unit })}
 					/>
 				</div>

frontend/src/pages/DashboardPageV2/DashboardContainer/PanelEditor/ConfigPane/sections/FormattingSection/__tests__/FormattingSection.test.tsx

@@ -3,6 +3,8 @@ import userEvent from '@testing-library/user-event';
 
 import FormattingSection from '../FormattingSection';
 
+// Auto-seeding is covered by useMetricYAxisUnit's tests; here `metricUnit` is just a prop.
+
 // Open the Decimals select (clicking its antd selector) and pick the option with the
 // given visible label.
 async function pickDecimal(label: string): Promise<void> {
@@ -71,4 +73,31 @@ describe('FormattingSection', () => {
 			decimalPrecision: '2',
 		});
 	});
+
+	it('warns when the selected unit mismatches the metric unit', () => {
+		// metric sent in seconds, but bytes is selected.
+		render(
+			<FormattingSection
+				value={{ unit: 'By' }}
+				controls={{ unit: true }}
+				metricUnit="s"
+				onChange={jest.fn()}
+			/>,
+		);
+
+		expect(screen.getByLabelText('warning')).toBeInTheDocument();
+	});
+
+	it('shows no warning when the selected unit matches the metric unit', () => {
+		render(
+			<FormattingSection
+				value={{ unit: 's' }}
+				controls={{ unit: true }}
+				metricUnit="s"
+				onChange={jest.fn()}
+			/>,
+		);
+
+		expect(screen.queryByLabelText('warning')).not.toBeInTheDocument();
+	});
 });

frontend/src/pages/DashboardPageV2/DashboardContainer/PanelEditor/ConfigPane/sections/ThresholdsSection/ThresholdsSection.tsx

@@ -1,4 +1,4 @@
-import { useState } from 'react';
+import { useRef, useState } from 'react';
 import { Plus } from '@signozhq/icons';
 import { Button } from '@signozhq/ui/button';
 import {
@@ -82,6 +82,15 @@ function ThresholdsSection({
 	// Which row is being edited, and whether it was just added (so Discard removes it).
 	const [editingIndex, setEditingIndex] = useState<number | null>(null);
 	const [unsavedIndex, setUnsavedIndex] = useState<number | null>(null);
+	// The saved threshold captured on edit entry, restored if the edit is discarded
+	// (edits stream into the spec live, so Discard can't just drop a local draft).
+	const editSnapshot = useRef<AnyThreshold | null>(null);
+
+	const updateAt =
+		(index: number) =>
+		(next: AnyThreshold): void => {
+			onChange(thresholds.map((t, i) => (i === index ? next : t)));
+		};
 
 	const addThreshold = (): void => {
 		const nextIndex = thresholds.length;
@@ -90,6 +99,11 @@ function ThresholdsSection({
 		setUnsavedIndex(nextIndex);
 	};
 
+	const beginEdit = (index: number): void => {
+		editSnapshot.current = thresholds[index] ?? null;
+		setEditingIndex(index);
+	};
+
 	const saveAt =
 		(index: number) =>
 		(next: AnyThreshold): void => {
@@ -105,11 +119,15 @@ function ThresholdsSection({
 	};
 
 	const discardAt = (index: number) => (): void => {
-		// Discarding a row that was never saved removes it; otherwise just exit edit.
+		// A never-saved row is removed; otherwise revert the live edits to the snapshot.
 		if (index === unsavedIndex) {
 			removeAt(index);
 			return;
 		}
+		const original = editSnapshot.current;
+		if (original) {
+			onChange(thresholds.map((t, i) => (i === index ? original : t)));
+		}
 		setEditingIndex(null);
 	};
 
@@ -120,8 +138,9 @@ function ThresholdsSection({
 			index,
 			yAxisUnit,
 			isEditing: editingIndex === index,
-			onEdit: (): void => setEditingIndex(index),
+			onEdit: (): void => beginEdit(index),
 			onSave: saveAt(index),
+			onLiveChange: updateAt(index),
 			onDiscard: discardAt(index),
 			onRemove: (): void => removeAt(index),
 		};

frontend/src/pages/DashboardPageV2/DashboardContainer/PanelEditor/ConfigPane/sections/ThresholdsSection/__tests__/ThresholdsSection.comparison.test.tsx

@@ -36,9 +36,16 @@ const THRESHOLDS: DashboardtypesComparisonThresholdDTO[] = [
 	},
 ];
 
-// Stateful harness for flows that depend on the value updating (add/discard).
-function Harness({ yAxisUnit }: { yAxisUnit?: string }): JSX.Element {
-	const [value, setValue] = useState<DashboardtypesComparisonThresholdDTO[]>([]);
+// Stateful harness for flows that depend on the value updating (add/discard/live).
+function Harness({
+	yAxisUnit,
+	initial = [],
+}: {
+	yAxisUnit?: string;
+	initial?: DashboardtypesComparisonThresholdDTO[];
+}): JSX.Element {
+	const [value, setValue] =
+		useState<DashboardtypesComparisonThresholdDTO[]>(initial);
 	return (
 		<ComparisonThresholdsSection
 			value={value}
@@ -142,24 +149,44 @@ describe('ComparisonThresholdsSection', () => {
 		expect(valueInput).toHaveValue(5);
 	});
 
-	it('does not commit edits when Discard is clicked', async () => {
+	it('reflects edits live (before Save) so the preview can react', async () => {
 		const user = userEvent.setup();
 		const onChange = jest.fn();
 		render(
 			<ComparisonThresholdsSection value={THRESHOLDS} onChange={onChange} />,
 		);
 
+		await user.click(screen.getByTestId('comparison-threshold-edit-0'));
+		await user.clear(screen.getByTestId('comparison-threshold-value-0'));
+		await user.type(screen.getByTestId('comparison-threshold-value-0'), '90');
+
+		// No Save click — the latest edit is already pushed up for the preview.
+		expect(onChange).toHaveBeenLastCalledWith([
+			{
+				value: 90,
+				color: '#F5B225',
+				operator: DashboardtypesComparisonOperatorDTO.above,
+				unit: 'percent',
+				format: DashboardtypesThresholdFormatDTO.background,
+			},
+		]);
+	});
+
+	it('reverts the live edits to the saved value on Discard', async () => {
+		const user = userEvent.setup();
+		render(<Harness initial={THRESHOLDS} />);
+
 		await user.click(screen.getByTestId('comparison-threshold-edit-0'));
 		await user.clear(screen.getByTestId('comparison-threshold-value-0'));
 		await user.type(screen.getByTestId('comparison-threshold-value-0'), '90');
 		await user.click(screen.getByTestId('comparison-threshold-discard-0'));
 
-		expect(onChange).not.toHaveBeenCalled();
-		// Back to view mode.
+		// Back to view mode, and re-opening shows the rolled-back 80, not 90.
 		expect(
 			screen.queryByTestId('comparison-threshold-value-0'),
 		).not.toBeInTheDocument();
-		expect(screen.getByTestId('comparison-threshold-edit-0')).toBeInTheDocument();
+		await user.click(screen.getByTestId('comparison-threshold-edit-0'));
+		expect(screen.getByTestId('comparison-threshold-value-0')).toHaveValue(80);
 	});
 
 	it('removes a threshold from view mode', async () => {

frontend/src/pages/DashboardPageV2/DashboardContainer/PanelEditor/ConfigPane/sections/ThresholdsSection/__tests__/ThresholdsSection.test.tsx

@@ -10,10 +10,16 @@ const THRESHOLDS: DashboardtypesThresholdWithLabelDTO[] = [
 	{ value: 80, color: '#F5B225', label: 'High', unit: 'percent' },
 ];
 
-// Stateful harness for flows that depend on the value updating (add/discard);
+// Stateful harness for flows that depend on the value updating (add/discard/live);
 // omits `controls` to exercise the default `label` variant.
-function Harness({ yAxisUnit }: { yAxisUnit?: string }): JSX.Element {
-	const [value, setValue] = useState<AnyThreshold[]>([]);
+function Harness({
+	yAxisUnit,
+	initial = [],
+}: {
+	yAxisUnit?: string;
+	initial?: AnyThreshold[];
+}): JSX.Element {
+	const [value, setValue] = useState<AnyThreshold[]>(initial);
 	return (
 		<ThresholdsSection value={value} onChange={setValue} yAxisUnit={yAxisUnit} />
 	);
@@ -70,19 +76,34 @@ describe('ThresholdsSection', () => {
 		]);
 	});
 
-	it('does not commit edits when Discard is clicked', () => {
+	it('reflects edits live (before Save) so the preview can react', () => {
 		const onChange = jest.fn();
 		render(<ThresholdsSection value={THRESHOLDS} onChange={onChange} />);
 
+		fireEvent.click(screen.getByTestId('threshold-edit-0'));
+		fireEvent.change(screen.getByTestId('threshold-value-0'), {
+			target: { value: '90' },
+		});
+
+		// No Save click — the edit is already pushed up for the preview to render.
+		expect(onChange).toHaveBeenLastCalledWith([
+			{ value: 90, color: '#F5B225', label: 'High', unit: 'percent' },
+		]);
+	});
+
+	it('reverts the live edits to the saved value on Discard', () => {
+		render(<Harness initial={THRESHOLDS} />);
+
 		fireEvent.click(screen.getByTestId('threshold-edit-0'));
 		fireEvent.change(screen.getByTestId('threshold-value-0'), {
 			target: { value: '90' },
 		});
 		fireEvent.click(screen.getByTestId('threshold-discard-0'));
 
-		expect(onChange).not.toHaveBeenCalled();
+		// Back to view mode, and re-opening shows the rolled-back 80, not 90.
 		expect(screen.queryByTestId('threshold-value-0')).not.toBeInTheDocument();
-		expect(screen.getByTestId('threshold-edit-0')).toBeInTheDocument();
+		fireEvent.click(screen.getByTestId('threshold-edit-0'));
+		expect(screen.getByTestId('threshold-value-0')).toHaveValue(80);
 	});
 
 	it('removes a threshold from view mode', () => {

frontend/src/pages/DashboardPageV2/DashboardContainer/PanelEditor/ConfigPane/sections/ThresholdsSection/rows/ComparisonThresholdRow.tsx

@@ -27,6 +27,7 @@ interface ComparisonThresholdRowProps {
 	isEditing: boolean;
 	onEdit: () => void;
 	onSave: (next: DashboardtypesComparisonThresholdDTO) => void;
+	onLiveChange: (next: DashboardtypesComparisonThresholdDTO) => void;
 	onDiscard: () => void;
 	onRemove: () => void;
 }
@@ -42,10 +43,15 @@ function ComparisonThresholdRow({
 	isEditing,
 	onEdit,
 	onSave,
+	onLiveChange,
 	onDiscard,
 	onRemove,
 }: ComparisonThresholdRowProps): JSX.Element {
-	const { draft, setDraft, setValue } = useThresholdDraft(threshold, isEditing);
+	const { draft, setDraft, setValue } = useThresholdDraft(
+		threshold,
+		isEditing,
+		onLiveChange,
+	);
 
 	const symbol = threshold.operator ? OPERATOR_SYMBOL[threshold.operator] : '';
 	const summary = (

frontend/src/pages/DashboardPageV2/DashboardContainer/PanelEditor/ConfigPane/sections/ThresholdsSection/rows/LabelThresholdRow.tsx

@@ -20,6 +20,7 @@ interface LabelThresholdRowProps {
 	isEditing: boolean;
 	onEdit: () => void;
 	onSave: (next: DashboardtypesThresholdWithLabelDTO) => void;
+	onLiveChange: (next: DashboardtypesThresholdWithLabelDTO) => void;
 	onDiscard: () => void;
 	onRemove: () => void;
 }
@@ -32,10 +33,15 @@ function LabelThresholdRow({
 	isEditing,
 	onEdit,
 	onSave,
+	onLiveChange,
 	onDiscard,
 	onRemove,
 }: LabelThresholdRowProps): JSX.Element {
-	const { draft, setDraft, setValue } = useThresholdDraft(threshold, isEditing);
+	const { draft, setDraft, setValue } = useThresholdDraft(
+		threshold,
+		isEditing,
+		onLiveChange,
+	);
 
 	// Persist an empty-string label when none was entered — the spec requires a string.
 	const handleSave = useCallback((): void => {

frontend/src/pages/DashboardPageV2/DashboardContainer/PanelEditor/ConfigPane/sections/ThresholdsSection/rows/TableThresholdRow.tsx

@@ -28,6 +28,7 @@ interface TableThresholdRowProps {
 	isEditing: boolean;
 	onEdit: () => void;
 	onSave: (next: DashboardtypesTableThresholdDTO) => void;
+	onLiveChange: (next: DashboardtypesTableThresholdDTO) => void;
 	onDiscard: () => void;
 	onRemove: () => void;
 }
@@ -45,10 +46,15 @@ function TableThresholdRow({
 	isEditing,
 	onEdit,
 	onSave,
+	onLiveChange,
 	onDiscard,
 	onRemove,
 }: TableThresholdRowProps): JSX.Element {
-	const { draft, setDraft, setValue } = useThresholdDraft(threshold, isEditing);
+	const { draft, setDraft, setValue } = useThresholdDraft(
+		threshold,
+		isEditing,
+		onLiveChange,
+	);
 
 	// Stored columnName is the query key; resolve its label + configured unit.
 	const columnUnit = tableColumns.find((c) => c.key === draft.columnName)?.unit;

frontend/src/pages/DashboardPageV2/DashboardContainer/PanelEditor/ConfigPane/sections/ThresholdsSection/rows/shared/useThresholdDraft.ts

@@ -9,12 +9,14 @@ interface ThresholdDraft<T> {
 
 /**
  * Local draft for a threshold row, shared by every variant. Snapshots the saved
- * threshold on each entry into edit mode (so Discard simply drops the draft and the
- * next edit starts clean) and exposes the numeric `value` setter all variants use.
+ * threshold on each entry into edit mode and exposes the numeric `value` setter all
+ * variants use. `onLiveChange` mirrors the draft into the spec as the user edits, so the
+ * panel preview updates live (without Save); the section reverts it on Discard.
  */
 export function useThresholdDraft<T extends { value: number }>(
 	threshold: T,
 	isEditing: boolean,
+	onLiveChange?: (draft: T) => void,
 ): ThresholdDraft<T> {
 	const [draft, setDraft] = useState<T>(threshold);
 
@@ -25,6 +27,13 @@ export function useThresholdDraft<T extends { value: number }>(
 		// eslint-disable-next-line react-hooks/exhaustive-deps -- snapshot only on edit entry
 	}, [isEditing]);
 
+	useEffect(() => {
+		if (isEditing) {
+			onLiveChange?.(draft);
+		}
+		// eslint-disable-next-line react-hooks/exhaustive-deps -- propagate on draft change only
+	}, [draft]);
+
 	const setValue = (raw: string): void => {
 		const next = Number(raw);
 		setDraft((d) => ({ ...d, value: Number.isNaN(next) ? d.value : next }));

frontend/src/pages/DashboardPageV2/DashboardContainer/PanelEditor/__tests__/getSwitchedPluginSpec.test.ts

@@ -1,6 +1,8 @@
 import {
-	TelemetrytypesSignalDTO,
+	DashboardtypesComparisonOperatorDTO,
 	type DashboardtypesPanelSpecDTO,
+	DashboardtypesThresholdFormatDTO,
+	TelemetrytypesSignalDTO,
 } from 'api/generated/services/sigNoz.schemas';
 import { getPanelDefinition } from 'pages/DashboardPageV2/DashboardContainer/Panels/registry';
 
@@ -95,4 +97,141 @@ describe('getSwitchedPluginSpec', () => {
 
 		expect(result.legend?.position).toBe('bottom');
 	});
+
+	describe('thresholds', () => {
+		it('does not carry thresholds when the new kind has no thresholds section', () => {
+			mockGetPanelDefinition.mockReturnValue({ sections: [{ kind: 'columns' }] });
+			const old = specWith({
+				thresholds: [{ value: 80, color: '#F1575F', label: 'warn' }],
+			});
+
+			const result = getSwitchedPluginSpec(
+				old,
+				'signoz/ListPanel',
+				TelemetrytypesSignalDTO.logs,
+			);
+
+			expect(result.thresholds).toBeUndefined();
+		});
+
+		it('carries thresholds verbatim within the label variant (color/value/unit/label)', () => {
+			mockGetPanelDefinition.mockReturnValue({
+				sections: [{ kind: 'thresholds', controls: { variant: 'label' } }],
+			});
+			const old = specWith({
+				thresholds: [{ value: 80, color: '#F1575F', unit: 'ms', label: 'warn' }],
+			});
+
+			const result = getSwitchedPluginSpec(
+				old,
+				'signoz/BarChartPanel',
+				TelemetrytypesSignalDTO.logs,
+			);
+
+			expect(result.thresholds).toStrictEqual([
+				{ value: 80, color: '#F1575F', unit: 'ms', label: 'warn' },
+			]);
+		});
+
+		it('remaps label thresholds into the comparison variant, defaulting operator + format', () => {
+			mockGetPanelDefinition.mockReturnValue({
+				sections: [{ kind: 'thresholds', controls: { variant: 'comparison' } }],
+			});
+			const old = specWith({
+				thresholds: [{ value: 80, color: '#F1575F', label: 'warn' }],
+			});
+
+			const result = getSwitchedPluginSpec(
+				old,
+				'signoz/NumberPanel',
+				TelemetrytypesSignalDTO.logs,
+			);
+
+			// The label is dropped; operator/format are seeded so the threshold can match.
+			expect(result.thresholds).toStrictEqual([
+				{
+					value: 80,
+					color: '#F1575F',
+					operator: DashboardtypesComparisonOperatorDTO.above,
+					format: DashboardtypesThresholdFormatDTO.text,
+				},
+			]);
+		});
+
+		it('remaps comparison thresholds into the table variant, keeping operator/format and seeding a column', () => {
+			mockGetPanelDefinition.mockReturnValue({
+				sections: [{ kind: 'thresholds', controls: { variant: 'table' } }],
+			});
+			const old = specWith({
+				thresholds: [
+					{
+						value: 80,
+						color: '#F1575F',
+						operator: DashboardtypesComparisonOperatorDTO.below,
+						format: DashboardtypesThresholdFormatDTO.text,
+					},
+				],
+			});
+
+			const result = getSwitchedPluginSpec(
+				old,
+				'signoz/TablePanel',
+				TelemetrytypesSignalDTO.logs,
+			);
+
+			expect(result.thresholds).toStrictEqual([
+				{
+					value: 80,
+					color: '#F1575F',
+					operator: DashboardtypesComparisonOperatorDTO.below,
+					format: DashboardtypesThresholdFormatDTO.text,
+					columnName: '',
+				},
+			]);
+		});
+
+		it('drops the table-only columnName when remapping into the label variant', () => {
+			mockGetPanelDefinition.mockReturnValue({
+				sections: [{ kind: 'thresholds', controls: { variant: 'label' } }],
+			});
+			const old = specWith({
+				thresholds: [
+					{
+						value: 80,
+						color: '#F1575F',
+						operator: DashboardtypesComparisonOperatorDTO.above,
+						format: DashboardtypesThresholdFormatDTO.background,
+						columnName: 'p99',
+					},
+				],
+			});
+
+			const result = getSwitchedPluginSpec(
+				old,
+				'signoz/TimeSeriesPanel',
+				TelemetrytypesSignalDTO.logs,
+			);
+
+			expect(result.thresholds).toStrictEqual([{ value: 80, color: '#F1575F' }]);
+		});
+
+		it('defaults the variant to label when the thresholds section omits controls', () => {
+			mockGetPanelDefinition.mockReturnValue({
+				sections: [{ kind: 'thresholds', controls: {} }],
+			});
+			const old = specWith({
+				thresholds: [{ value: 80, color: '#F1575F', label: 'warn' }],
+			});
+
+			const result = getSwitchedPluginSpec(
+				old,
+				'signoz/TimeSeriesPanel',
+				TelemetrytypesSignalDTO.logs,
+			);
+
+			expect(result.thresholds).toStrictEqual([
+				{ value: 80, color: '#F1575F', label: 'warn' },
+			]);
+		});
+	});
 });

frontend/src/pages/DashboardPageV2/DashboardContainer/PanelEditor/getSwitchedPluginSpec.ts

@@ -1,13 +1,18 @@
-import type {
-	DashboardtypesPanelSpecDTO,
-	TelemetrytypesSignalDTO,
-	TelemetrytypesTelemetryFieldKeyDTO,
+import {
+	DashboardtypesComparisonOperatorDTO,
+	type DashboardtypesPanelSpecDTO,
+	DashboardtypesThresholdFormatDTO,
+	type TelemetrytypesSignalDTO,
+	type TelemetrytypesTelemetryFieldKeyDTO,
 } from 'api/generated/services/sigNoz.schemas';
 import { getPanelDefinition } from 'pages/DashboardPageV2/DashboardContainer/Panels/registry';
 import type { PanelKind } from 'pages/DashboardPageV2/DashboardContainer/Panels/types/panelKind';
 import {
-	SectionKind,
+	type AnyThreshold,
 	type PanelFormattingSlice,
+	type SectionConfig,
+	SectionKind,
+	type ThresholdVariant,
 } from 'pages/DashboardPageV2/DashboardContainer/Panels/types/sections';
 import {
 	buildDefaultPluginSpec,
@@ -24,13 +29,73 @@ import { defaultColumnsForSignal } from './ListColumnsEditor/selectFields';
 export interface SwitchedPluginSpec extends DefaultPluginSpec {
 	formatting?: Pick<PanelFormattingSlice, 'unit' | 'decimalPrecision'>;
 	selectFields?: TelemetrytypesTelemetryFieldKeyDTO[];
+	thresholds?: AnyThreshold[];
+}
+
+/** Every field any threshold variant can hold; switching reads across shapes to remap. */
+interface AnyThresholdFields {
+	color: string;
+	value: number;
+	unit?: string;
+	operator?: DashboardtypesComparisonOperatorDTO;
+	format?: DashboardtypesThresholdFormatDTO;
+	columnName?: string;
+	label?: string;
+}
+
+/** The threshold variant a kind edits, or `undefined` when it has no Thresholds section. */
+function getThresholdVariant(
+	sections: SectionConfig[],
+): ThresholdVariant | undefined {
+	const section = sections.find(
+		(s): s is Extract<SectionConfig, { kind: SectionKind.Thresholds }> =>
+			s.kind === SectionKind.Thresholds,
+	);
+	return section ? (section.controls.variant ?? 'label') : undefined;
+}
+
+/**
+ * Remaps a threshold to the target kind's variant: keeps the shared core (color, value,
+ * unit) plus any cross-variant fields, and seeds the rest with the variant's defaults so
+ * the carried threshold stays functional (a comparison/table threshold needs an operator
+ * to match, a table threshold a column).
+ */
+function toThresholdVariant(
+	source: AnyThresholdFields,
+	variant: ThresholdVariant,
+): AnyThreshold {
+	const core = {
+		color: source.color,
+		value: source.value,
+		...(source.unit !== undefined && { unit: source.unit }),
+	};
+	if (variant === 'comparison') {
+		return {
+			...core,
+			operator: source.operator ?? DashboardtypesComparisonOperatorDTO.above,
+			format: source.format ?? DashboardtypesThresholdFormatDTO.text,
+		};
+	}
+	if (variant === 'table') {
+		return {
+			...core,
+			operator: source.operator ?? DashboardtypesComparisonOperatorDTO.above,
+			format: source.format ?? DashboardtypesThresholdFormatDTO.background,
+			columnName: source.columnName ?? '',
+		};
+	}
+	return {
+		...core,
+		...(source.label !== undefined && { label: source.label }),
+	};
 }
 
 /**
  * Builds the plugin spec for a first-visit switch to `newKind`: the kind's declared
  * section defaults (so the config pane opens populated, matching new-panel seeding) plus
- * the only cross-kind config worth keeping — unit + decimal precision. Switching into a
- * List seeds the current signal's default columns so the columns control isn't empty.
+ * the cross-kind config worth keeping — unit + decimal precision, and thresholds when the
+ * new kind supports them (remapped to its variant). Switching into a List seeds the
+ * current signal's default columns so the columns control isn't empty.
  *
  * Revisiting a kind restores its stashed spec instead, so this runs only on first visit.
  */
@@ -66,5 +131,19 @@ export function getSwitchedPluginSpec(
 		}
 	}
 
+	const thresholdVariant = getThresholdVariant(sections);
+	if (thresholdVariant) {
+		const oldThresholds = (
+			oldSpec.plugin.spec as {
+				thresholds?: AnyThreshold[] | null;
+			}
+		).thresholds;
+		if (oldThresholds && oldThresholds.length > 0) {
+			result.thresholds = oldThresholds.map((threshold) =>
+				toThresholdVariant(threshold as AnyThresholdFields, thresholdVariant),
+			);
+		}
+	}
+
 	return result;
 }

frontend/src/pages/DashboardPageV2/DashboardContainer/PanelEditor/hooks/__tests__/useMetricYAxisUnit.test.ts

@@ -0,0 +1,103 @@
+import { renderHook } from '@testing-library/react';
+import useGetYAxisUnit from 'hooks/useGetYAxisUnit';
+
+import { useMetricYAxisUnit } from '../useMetricYAxisUnit';
+
+jest.mock('hooks/useGetYAxisUnit', () => ({
+	__esModule: true,
+	default: jest.fn(),
+}));
+
+const mockUseGetYAxisUnit = useGetYAxisUnit as unknown as jest.Mock;
+
+function mockMetricUnit(
+	yAxisUnit: string | undefined,
+	isLoading = false,
+): void {
+	mockUseGetYAxisUnit.mockReturnValue({ yAxisUnit, isLoading, isError: false });
+}
+
+describe('useMetricYAxisUnit', () => {
+	beforeEach(() => jest.clearAllMocks());
+
+	it('seeds the unit from the metric on a new panel', () => {
+		mockMetricUnit('bytes');
+		const onSelectUnit = jest.fn();
+
+		renderHook(() =>
+			useMetricYAxisUnit({ isNewPanel: true, unit: undefined, onSelectUnit }),
+		);
+
+		expect(onSelectUnit).toHaveBeenCalledWith('bytes');
+	});
+
+	it('does not seed when not a new panel', () => {
+		mockMetricUnit('bytes');
+		const onSelectUnit = jest.fn();
+
+		renderHook(() =>
+			useMetricYAxisUnit({ isNewPanel: false, unit: undefined, onSelectUnit }),
+		);
+
+		expect(onSelectUnit).not.toHaveBeenCalled();
+	});
+
+	it('does not seed when the metric has no unit', () => {
+		mockMetricUnit(undefined);
+		const onSelectUnit = jest.fn();
+
+		renderHook(() =>
+			useMetricYAxisUnit({ isNewPanel: true, unit: undefined, onSelectUnit }),
+		);
+
+		expect(onSelectUnit).not.toHaveBeenCalled();
+	});
+
+	it('does not seed when the unit already matches the metric', () => {
+		mockMetricUnit('bytes');
+		const onSelectUnit = jest.fn();
+
+		renderHook(() =>
+			useMetricYAxisUnit({ isNewPanel: true, unit: 'bytes', onSelectUnit }),
+		);
+
+		expect(onSelectUnit).not.toHaveBeenCalled();
+	});
+
+	it('re-seeds when the resolved metric unit changes', () => {
+		mockMetricUnit('bytes');
+		const onSelectUnit = jest.fn();
+
+		const { rerender } = renderHook(
+			(props: { unit: string | undefined }) =>
+				useMetricYAxisUnit({
+					isNewPanel: true,
+					unit: props.unit,
+					onSelectUnit,
+				}),
+			{ initialProps: { unit: undefined as string | undefined } },
+		);
+		expect(onSelectUnit).toHaveBeenLastCalledWith('bytes');
+
+		// The metric changes; the panel now holds the previously-seeded unit.
+		mockMetricUnit('ms');
+		rerender({ unit: 'bytes' });
+
+		expect(onSelectUnit).toHaveBeenLastCalledWith('ms');
+	});
+
+	it('returns the resolved metric unit and loading state', () => {
+		mockMetricUnit('bytes', true);
+
+		const { result } = renderHook(() =>
+			useMetricYAxisUnit({
+				isNewPanel: false,
+				unit: undefined,
+				onSelectUnit: jest.fn(),
+			}),
+		);
+
+		expect(result.current.metricUnit).toBe('bytes');
+		expect(result.current.isLoading).toBe(true);
+	});
+});

frontend/src/pages/DashboardPageV2/DashboardContainer/PanelEditor/hooks/useMetricYAxisUnit.ts

@@ -0,0 +1,36 @@
+import { useEffect } from 'react';
+import useGetYAxisUnit from 'hooks/useGetYAxisUnit';
+
+interface UseMetricYAxisUnitArgs {
+	/** Only a new panel auto-seeds; editing never overwrites the saved unit. */
+	isNewPanel: boolean;
+	unit: string | undefined;
+	onSelectUnit: (unit: string) => void;
+}
+
+interface UseMetricYAxisUnitResult {
+	metricUnit: string | undefined;
+	isLoading: boolean;
+}
+
+/**
+ * Resolves the selected metric's unit and, on a new panel only, seeds the formatting unit
+ * from it (V1 parity); returns the unit for the selector's mismatch warning.
+ */
+export function useMetricYAxisUnit({
+	isNewPanel,
+	unit,
+	onSelectUnit,
+}: UseMetricYAxisUnitArgs): UseMetricYAxisUnitResult {
+	const { yAxisUnit: metricUnit, isLoading } = useGetYAxisUnit();
+
+	useEffect(() => {
+		if (isNewPanel && metricUnit && metricUnit !== unit) {
+			onSelectUnit(metricUnit);
+		}
+		// Re-seed only when the resolved metric unit changes, not on every unit edit.
+		// eslint-disable-next-line react-hooks/exhaustive-deps
+	}, [isNewPanel, metricUnit]);
+
+	return { metricUnit, isLoading };
+}

frontend/src/pages/DashboardPageV2/DashboardContainer/PanelEditor/index.tsx

@@ -8,6 +8,8 @@ import {
 import { toast } from '@signozhq/ui/sonner';
 import {
 	type DashboardtypesPanelDTO,
+	type DashboardtypesPanelFormattingDTO,
+	type DashboardtypesPanelSpecDTO,
 	TelemetrytypesSignalDTO,
 } from 'api/generated/services/sigNoz.schemas';
 import { PANEL_TYPES } from 'constants/queryBuilder';
@@ -30,6 +32,7 @@ import { useLegendSeries } from './hooks/useLegendSeries';
 import { usePanelQuery } from '../hooks/usePanelQuery';
 import { usePanelEditorDraft } from './hooks/usePanelEditorDraft';
 import { usePanelEditorQuerySync } from './hooks/usePanelEditorQuerySync';
+import { useMetricYAxisUnit } from './hooks/useMetricYAxisUnit';
 import { usePanelEditorSave } from './hooks/usePanelEditorSave';
 import { usePanelTypeSwitch } from './hooks/usePanelTypeSwitch';
 import { useSeedNewListColumns } from './hooks/useSeedNewListColumns';
@@ -123,6 +126,33 @@ function PanelEditorContainer({
 	// Switch the panel's visualization kind in place (reversible per session).
 	const { onChangePanelKind } = usePanelTypeSwitch({ spec, panelType, setSpec });
 
+	// At editor level, not the collapsible FormattingSection, so seeding runs while closed.
+	const formattingUnit = (
+		spec.plugin.spec as {
+			formatting?: DashboardtypesPanelFormattingDTO;
+		}
+	).formatting?.unit;
+	const seedFormattingUnit = useCallback(
+		(unit: string): void => {
+			const pluginSpec = spec.plugin.spec as {
+				formatting?: DashboardtypesPanelFormattingDTO;
+			};
+			setSpec({
+				...spec,
+				plugin: {
+					...spec.plugin,
+					spec: { ...pluginSpec, formatting: { ...pluginSpec.formatting, unit } },
+				},
+			} as DashboardtypesPanelSpecDTO);
+		},
+		[spec, setSpec],
+	);
+	const { metricUnit } = useMetricYAxisUnit({
+		isNewPanel: isNew,
+		unit: formattingUnit,
+		onSelectUnit: seedFormattingUnit,
+	});
+
 	// Spec and query dirtiness are tracked independently so query re-serialization
 	// never false-dirties. A new panel is always savable (you're creating it).
 	const isDirty = isNew || isSpecDirty || isQueryDirty;
@@ -250,6 +280,7 @@ function PanelEditorContainer({
 						legendSeries={legendSeries}
 						tableColumns={tableColumns}
 						stepInterval={stepInterval}
+						metricUnit={metricUnit}
 					/>
 				</ResizablePanel>
 			</ResizablePanelGroup>

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

@@ -108,7 +108,9 @@ function addSeries({
 	// `customColors` is nullable on the spec; coerce so `addSeries` always gets
 	// a defined record (it dereferences keys without a guard).
 	const colorMapping = spec.legend?.customColors ?? {};
-	const spanGaps = resolveSpanGaps(chartAppearance?.spanGaps?.fillLessThan);
+	const spanGaps = chartAppearance?.spanGaps
+		? resolveSpanGaps(chartAppearance?.spanGaps)
+		: true;
 
 	const lineStyle = chartAppearance?.lineStyle
 		? LINE_STYLE_MAP[chartAppearance.lineStyle]

frontend/src/pages/DashboardPageV2/DashboardContainer/Panels/utils/chartAppearance/__tests__/resolvers.test.ts

@@ -1,22 +1,35 @@
 import { resolveSpanGaps } from '../resolvers';
 
 describe('resolveSpanGaps', () => {
-	it('spans all gaps (true) when unset', () => {
-		expect(resolveSpanGaps(undefined)).toBe(true);
-		expect(resolveSpanGaps('')).toBe(true);
-	});
-
-	it('parses a duration string into seconds', () => {
-		expect(resolveSpanGaps('5s')).toBe(5);
-		expect(resolveSpanGaps('10m')).toBe(600);
-		expect(resolveSpanGaps('1h')).toBe(3600);
+	it('parses a duration string into seconds when thresholding', () => {
+		expect(resolveSpanGaps({ fillOnlyBelow: true, fillLessThan: '5s' })).toBe(5);
+		expect(resolveSpanGaps({ fillOnlyBelow: true, fillLessThan: '10m' })).toBe(
+			600,
+		);
+		expect(resolveSpanGaps({ fillOnlyBelow: true, fillLessThan: '1h' })).toBe(
+			3600,
+		);
 	});
 
 	it('tolerates a bare seconds number (back-compat)', () => {
-		expect(resolveSpanGaps('600')).toBe(600);
+		expect(resolveSpanGaps({ fillOnlyBelow: true, fillLessThan: '600' })).toBe(
+			600,
+		);
 	});
 
 	it('falls back to true for unparseable input', () => {
-		expect(resolveSpanGaps('abc')).toBe(true);
+		expect(resolveSpanGaps({ fillOnlyBelow: true, fillLessThan: 'abc' })).toBe(
+			true,
+		);
+	});
+
+	it('spans all gaps when fillOnlyBelow is explicitly false, ignoring any duration', () => {
+		expect(resolveSpanGaps({ fillOnlyBelow: false, fillLessThan: '5m' })).toBe(
+			true,
+		);
+	});
+
+	it('treats a duration with no fillOnlyBelow flag as a threshold (legacy panels)', () => {
+		expect(resolveSpanGaps({ fillLessThan: '5m' })).toBe(300);
 	});
 });

frontend/src/pages/DashboardPageV2/DashboardContainer/Panels/utils/chartAppearance/resolvers.ts

@@ -2,6 +2,7 @@ import { rangeUtil } from '@grafana/data';
 import {
 	DashboardtypesLegendPositionDTO,
 	DashboardtypesPrecisionOptionDTO,
+	type DashboardtypesSpanGapsDTO,
 } from 'api/generated/services/sigNoz.schemas';
 import { PrecisionOption, PrecisionOptionsEnum } from 'components/Graph/types';
 import { LegendPosition } from 'lib/uPlotV2/components/types';
@@ -39,15 +40,14 @@ export function resolveDecimalPrecision(
 }
 
 /**
- * `spec.chartAppearance.spanGaps.fillLessThan` is a duration string on the wire
- * ("10m", "5s"). Empty/missing → span all gaps (default); otherwise forward the
- * threshold in seconds so uPlot only bridges short runs of nulls. Tolerates a
- * bare seconds number for back-compat.
+ * Resolves `spanGaps` to uPlot's value. `fillOnlyBelow: false` spans every gap regardless
+ * of `fillLessThan`; a duration with no flag still thresholds (panels predating the flag).
  */
 export function resolveSpanGaps(
-	fillLessThan: string | undefined,
+	spanGaps: DashboardtypesSpanGapsDTO,
 ): boolean | number {
-	if (!fillLessThan) {
+	const fillLessThan = spanGaps.fillLessThan;
+	if (spanGaps.fillOnlyBelow === false || !fillLessThan) {
 		return true;
 	}
 	const seconds = rangeUtil.isValidTimeSpan(fillLessThan)