diff --git a/community-modules/styles/src/internal/base/parts/_calculated-columns.scss b/community-modules/styles/src/internal/base/parts/_calculated-columns.scss
index cfaa1883d98..5d2f79dac1e 100644
--- a/community-modules/styles/src/internal/base/parts/_calculated-columns.scss
+++ b/community-modules/styles/src/internal/base/parts/_calculated-columns.scss
@@ -1,3 +1,5 @@
+@use 'ag';
+
 @mixin output {
     .ag-calculated-column-panel .ag-panel-content-wrapper {
         padding: var(--ag-grid-size) var(--ag-cell-horizontal-padding);
@@ -41,9 +43,15 @@
     .ag-calculated-column-expression-tools {
         display: flex;
 
-        .ag-group-container {
-            flex: 1 1 auto;
-            justify-content: end;
+        .ag-label {
+            @include ag.unthemed-rtl(
+                (
+                    text-align: right,
+                )
+            );
+        }
+
+        .ag-field-set-wrapper {
             gap: var(--ag-grid-size);
             flex-wrap: nowrap;
             align-items: center;
diff --git a/community-modules/styles/src/internal/base/parts/_common-structural.scss b/community-modules/styles/src/internal/base/parts/_common-structural.scss
index 11a2cb41339..cc2bedd972e 100644
--- a/community-modules/styles/src/internal/base/parts/_common-structural.scss
+++ b/community-modules/styles/src/internal/base/parts/_common-structural.scss
@@ -1963,6 +1963,23 @@
         align-items: flex-end;
     }
 
+    .ag-field-set {
+        display: flex;
+        align-items: center;
+    }
+
+    .ag-field-set-wrapper {
+        display: flex;
+    }
+
+    .ag-field-set-wrapper-horizontal {
+        flex-direction: row;
+    }
+
+    .ag-field-set-wrapper-vertical {
+        flex-direction: column;
+    }
+
     .ag-toggle-button-icon {
         transition: right 0.3s;
         position: absolute;
diff --git a/packages/ag-grid-community/src/agWidgets/agFieldSet.css b/packages/ag-grid-community/src/agWidgets/agFieldSet.css
new file mode 100644
index 00000000000..bcc88bf6828
--- /dev/null
+++ b/packages/ag-grid-community/src/agWidgets/agFieldSet.css
@@ -0,0 +1,16 @@
+.ag-field-set {
+    display: flex;
+    align-items: center;
+}
+
+.ag-field-set-wrapper {
+    display: flex;
+}
+
+.ag-field-set-wrapper-horizontal {
+    flex-direction: row;
+}
+
+.ag-field-set-wrapper-vertical {
+    flex-direction: column;
+}
diff --git a/packages/ag-grid-community/src/agWidgets/agFieldSet.ts b/packages/ag-grid-community/src/agWidgets/agFieldSet.ts
new file mode 100644
index 00000000000..ac9ccaebdf1
--- /dev/null
+++ b/packages/ag-grid-community/src/agWidgets/agFieldSet.ts
@@ -0,0 +1,89 @@
+import type {
+    AgBaseComponent,
+    AgComponentSelector,
+    AgCoreBeanCollection,
+    AgElementParams,
+    BaseEvents,
+    BaseProperties,
+    IPropertiesService,
+} from 'ag-stack';
+import { RefPlaceholder, _isComponent } from 'ag-stack';
+
+import { AgAbstractLabel } from './agAbstractLabel';
+import type { AgLabelParams } from './agFieldParams';
+import agFieldSetCSS from './agFieldSet.css';
+import type { AgWidgetSelectorType } from './agWidgetSelectorType';
+
+type AgFieldSetItem<TBeanCollection> = AgBaseComponent<TBeanCollection> | HTMLElement;
+type AgFieldSetDirection = 'horizontal' | 'vertical';
+
+const AgFieldSetElement: AgElementParams<any> = {
+    tag: 'div',
+    cls: 'ag-field-set',
+    role: 'group',
+    children: [
+        { tag: 'div', ref: 'eLabel' },
+        { tag: 'div', ref: 'eWrapper', cls: 'ag-wrapper ag-field-set-wrapper ag-field-set-wrapper-horizontal' },
+    ],
+};
+
+/** @internal AG_GRID_INTERNAL - Not for public use. Can change / be removed at any time. */
+export class AgFieldSet<
+    TBeanCollection extends AgCoreBeanCollection<TProperties, TGlobalEvents, TCommon, TPropertiesService>,
+    TProperties extends BaseProperties,
+    TGlobalEvents extends BaseEvents,
+    TCommon,
+    TPropertiesService extends IPropertiesService<TProperties, TCommon>,
+    TComponentSelectorType extends string,
+    TConfig extends AgLabelParams = AgLabelParams,
+> extends AgAbstractLabel<
+    TBeanCollection,
+    TProperties,
+    TGlobalEvents,
+    TCommon,
+    TPropertiesService,
+    TComponentSelectorType,
+    TConfig
+> {
+    protected readonly eLabel: HTMLElement = RefPlaceholder;
+    private readonly eWrapper: HTMLElement = RefPlaceholder;
+
+    constructor(config?: TConfig) {
+        super(config, AgFieldSetElement as AgElementParams<TComponentSelectorType>);
+        this.registerCSS(agFieldSetCSS);
+    }
+
+    public override postConstruct(): void {
+        super.postConstruct();
+
+        this.addCss('ag-field-set');
+        this.getGui().setAttribute('aria-labelledby', this.getLabelId());
+    }
+
+    public addItems(items: AgFieldSetItem<TBeanCollection>[]): void {
+        for (const item of items) {
+            this.addItem(item);
+        }
+    }
+
+    public addItem(item: AgFieldSetItem<TBeanCollection>): void {
+        const el = _isComponent(item) ? item.getGui() : item;
+
+        this.eWrapper.appendChild(el);
+    }
+
+    public setDirection(direction: AgFieldSetDirection): this {
+        const eWrapper = this.eWrapper;
+
+        eWrapper.classList.toggle('ag-field-set-wrapper-horizontal', direction === 'horizontal');
+        eWrapper.classList.toggle('ag-field-set-wrapper-vertical', direction === 'vertical');
+
+        return this;
+    }
+}
+
+/** @internal AG_GRID_INTERNAL - Not for public use. Can change / be removed at any time. */
+export const AgFieldSetSelector: AgComponentSelector<AgWidgetSelectorType> = {
+    selector: 'AG-FIELD-SET',
+    component: AgFieldSet,
+};
diff --git a/packages/ag-grid-community/src/agWidgets/agWidgetSelectorType.ts b/packages/ag-grid-community/src/agWidgets/agWidgetSelectorType.ts
index a7b68e90437..06b572e7554 100644
--- a/packages/ag-grid-community/src/agWidgets/agWidgetSelectorType.ts
+++ b/packages/ag-grid-community/src/agWidgets/agWidgetSelectorType.ts
@@ -3,6 +3,7 @@ export type AgWidgetSelectorType =
     | 'AG-CHECKBOX'
     | 'AG-COLOR-INPUT'
     | 'AG-COLOR-PICKER'
+    | 'AG-FIELD-SET'
     | 'AG-GROUP-COMPONENT'
     | 'AG-INPUT-DATE-FIELD'
     | 'AG-INPUT-NUMBER-FIELD'
diff --git a/packages/ag-grid-community/src/main-internal.ts b/packages/ag-grid-community/src/main-internal.ts
index eeb88906898..0bb5cfbbebb 100644
--- a/packages/ag-grid-community/src/main-internal.ts
+++ b/packages/ag-grid-community/src/main-internal.ts
@@ -394,6 +394,7 @@ export { AgAbstractInputField } from './agWidgets/agAbstractInputField';
 export { AgAbstractLabel } from './agWidgets/agAbstractLabel';
 export { AgCheckbox, AgCheckboxSelector } from './agWidgets/agCheckbox';
 export { AgContentEditableField, AgContentEditableFieldSelector } from './agWidgets/agContentEditableField';
+export { AgFieldSet, AgFieldSetSelector } from './agWidgets/agFieldSet';
 export type {
     AgCheckboxParams,
     AgFieldParams,
diff --git a/packages/ag-grid-community/src/widgets/gridWidgetTypes.ts b/packages/ag-grid-community/src/widgets/gridWidgetTypes.ts
index 05bcb250c3c..6c45d9c74bd 100644
--- a/packages/ag-grid-community/src/widgets/gridWidgetTypes.ts
+++ b/packages/ag-grid-community/src/widgets/gridWidgetTypes.ts
@@ -1,5 +1,6 @@
 import type { AgCheckbox } from '../agWidgets/agCheckbox';
 import type { AgCheckboxParams } from '../agWidgets/agFieldParams';
+import type { AgFieldSet } from '../agWidgets/agFieldSet';
 import type { AgInputDateField } from '../agWidgets/agInputDateField';
 import type { AgInputNumberField } from '../agWidgets/agInputNumberField';
 import type { AgInputTextArea } from '../agWidgets/agInputTextArea';
@@ -102,3 +103,13 @@ export type GridSelect<TValue = string | null> = AgSelect<
     AgComponentSelectorType,
     TValue
 >;
+
+/** @internal AG_GRID_INTERNAL - Not for public use. Can change / be removed at any time. */
+export type GridFieldSet = AgFieldSet<
+    BeanCollection,
+    GridOptionsWithDefaults,
+    AgEventTypeParams,
+    AgGridCommon<any, any>,
+    GridOptionsService,
+    AgComponentSelectorType
+>;
diff --git a/packages/ag-grid-enterprise/src/calculatedColumns/calculatedColumnForm.ts b/packages/ag-grid-enterprise/src/calculatedColumns/calculatedColumnForm.ts
index a2e115df75a..6011e2c06c1 100644
--- a/packages/ag-grid-enterprise/src/calculatedColumns/calculatedColumnForm.ts
+++ b/packages/ag-grid-enterprise/src/calculatedColumns/calculatedColumnForm.ts
@@ -3,6 +3,7 @@ import { RefPlaceholder, _getDocument, _setDisplayed } from 'ag-stack';
 import type {
     CalculatedColumnExpressionPicker,
     ElementParams,
+    GridFieldSet,
     GridInputTextArea,
     GridInputTextField,
     GridSelect,
@@ -10,6 +11,7 @@ import type {
     TooltipFeature,
 } from 'ag-grid-community';
 import {
+    AgFieldSetSelector,
     AgInputTextAreaSelector,
     AgInputTextFieldSelector,
     AgSelectSelector,
@@ -19,8 +21,6 @@ import {
 
 import { AgAutocompleteList } from '../advancedFilter/autocomplete/agAutocompleteList';
 import type { AutocompleteEntry } from '../advancedFilter/autocomplete/autocompleteParams';
-import { AgGroupComponentSelector } from '../agStack/agGroupComponent';
-import type { GroupComponent } from '../widgets/gridEnterpriseWidgetTypes';
 import { CalculatedColumnAutocompleteRow } from './calculatedColumnAutocompleteRow';
 import type {
     CalculatedColumnDataTypeOption,
@@ -68,7 +68,7 @@ const CalculatedColumnFormElement: ElementParams = {
             children: [
                 { tag: 'ag-input-text-area', ref: 'eExpression' },
                 {
-                    tag: 'ag-group-component',
+                    tag: 'ag-field-set',
                     cls: 'ag-calculated-column-expression-tools',
                     ref: 'eExpressionTools',
                     children: [
@@ -117,7 +117,7 @@ export class CalculatedColumnForm extends Component {
     private readonly eApply: HTMLButtonElement = RefPlaceholder;
     private readonly eCancel: HTMLButtonElement = RefPlaceholder;
     private readonly eActions: HTMLElement = RefPlaceholder;
-    private readonly eExpressionTools: GroupComponent = RefPlaceholder;
+    private readonly eExpressionTools: GridFieldSet = RefPlaceholder;
 
     private activeReplacement: { start: number; end: number } | null = null;
     private suggestionSource: HTMLElement | null = null;
@@ -150,7 +150,7 @@ export class CalculatedColumnForm extends Component {
             AgInputTextFieldSelector,
             AgSelectSelector,
             AgInputTextAreaSelector,
-            AgGroupComponentSelector,
+            AgFieldSetSelector,
         ]);
         this.expressionPickers = new Set(expressionPickers);
     }
@@ -202,8 +202,9 @@ export class CalculatedColumnForm extends Component {
 
         this.eExpressionTools
             .setDirection('horizontal')
-            .setTitle(translate('calculatedColumnExpressionToolsLabel', 'Insert'))
-            .hideOpenCloseIcons(true);
+            .setLabelWidth('flex')
+            .setLabel(translate('calculatedColumnExpressionToolsLabel', 'Insert'))
+            .setLabelSeparator(':');
     }
 
     private setupActionButtons(): void {
diff --git a/packages/ag-grid-enterprise/src/calculatedColumns/calculatedColumns.css b/packages/ag-grid-enterprise/src/calculatedColumns/calculatedColumns.css
index 8e660f2e064..7840f757fc6 100644
--- a/packages/ag-grid-enterprise/src/calculatedColumns/calculatedColumns.css
+++ b/packages/ag-grid-enterprise/src/calculatedColumns/calculatedColumns.css
@@ -44,8 +44,11 @@
 .ag-calculated-column-expression-tools {
     display: flex;
 
-    :where(.ag-group-container) {
-        flex: 1 1 auto;
+    :where(.ag-label) {
+        text-align: right;
+    }
+
+    :where(.ag-field-set-wrapper) {
         justify-content: end;
         gap: var(--ag-spacing);
         flex-wrap: nowrap;
diff --git a/packages/ag-grid-enterprise/src/rowHierarchy/autoColService.ts b/packages/ag-grid-enterprise/src/rowHierarchy/autoColService.ts
index 867210dc13e..1ad9c6c6360 100644
--- a/packages/ag-grid-enterprise/src/rowHierarchy/autoColService.ts
+++ b/packages/ag-grid-enterprise/src/rowHierarchy/autoColService.ts
@@ -1,7 +1,9 @@
 import type {
+    CellRendererSelectorResult,
     ColDef,
     ColumnEventType,
     IAutoColService,
+    ITooltipParams,
     NamedBean,
     PropertyValueChangedEvent,
     RowNode,
@@ -234,9 +236,108 @@ export class AutoColService extends BeanStub implements NamedBean, IAutoColServi
             res.initialSort = undefined;
         }
 
+        if (!underlyingColumn) {
+            this.applyDynamicSingleColumnTooltips(res, autoGroupColumnDef);
+        }
+
         return res;
     }
 
+    // Each group row's `rowGroupColumn` differs per row, so tooltips must dispatch at render time.
+    private applyDynamicSingleColumnTooltips(res: ColDef, autoGroupColumnDef: ColDef | undefined): void {
+        const leafTooltipValueGetter = autoGroupColumnDef?.tooltipValueGetter;
+        const leafTooltipField = autoGroupColumnDef?.tooltipField;
+        const leafTooltipComponent = autoGroupColumnDef?.tooltipComponent;
+        const leafTooltipComponentParams = autoGroupColumnDef?.tooltipComponentParams;
+        const leafTooltipComponentSelector = autoGroupColumnDef?.tooltipComponentSelector;
+
+        const rowGroupCols = this.beans.rowGroupColsSvc?.columns ?? [];
+        const anyGroupColHasTooltip = rowGroupCols.some(
+            (col) =>
+                col.colDef.tooltipValueGetter ||
+                col.colDef.tooltipField ||
+                col.colDef.tooltipComponent ||
+                col.colDef.tooltipComponentSelector
+        );
+
+        const hasTooltipConfig =
+            anyGroupColHasTooltip ||
+            leafTooltipValueGetter != null ||
+            leafTooltipField != null ||
+            leafTooltipComponent != null ||
+            leafTooltipComponentSelector != null;
+
+        if (!hasTooltipConfig) {
+            return;
+        }
+
+        res.tooltipField = undefined;
+        res.tooltipComponent = undefined;
+        res.tooltipComponentParams = undefined;
+
+        res.tooltipValueGetter = (params) => {
+            if (params.node?.group) {
+                const groupedCol = params.node.rowGroupColumn as AgColumn | undefined;
+                if (!groupedCol) {
+                    return undefined;
+                }
+                const colDef = groupedCol.colDef;
+                if (colDef.tooltipValueGetter) {
+                    return colDef.tooltipValueGetter(params);
+                }
+                if (colDef.tooltipField) {
+                    return params.value;
+                }
+                return undefined;
+            }
+            if (leafTooltipValueGetter) {
+                return leafTooltipValueGetter(params);
+            }
+            if (leafTooltipField && params.data) {
+                return (params.data as Record<string, unknown>)[leafTooltipField];
+            }
+            return undefined;
+        };
+
+        const needsSelector =
+            anyGroupColHasTooltip || leafTooltipComponent != null || leafTooltipComponentSelector != null;
+        if (!needsSelector) {
+            return;
+        }
+
+        // tooltipComponentSelector is typed for cell params but called with ITooltipParams at runtime
+        const callSelector = (
+            sel: ColDef['tooltipComponentSelector'],
+            params: ITooltipParams
+        ): CellRendererSelectorResult | undefined =>
+            (sel as unknown as (p: ITooltipParams) => CellRendererSelectorResult | undefined)(params);
+
+        const selector = (params: ITooltipParams): CellRendererSelectorResult | undefined => {
+            if (params.node?.group) {
+                const groupedCol = params.node.rowGroupColumn as AgColumn | undefined;
+                const colDef = groupedCol?.colDef;
+                if (!colDef) {
+                    return undefined;
+                }
+                if (colDef.tooltipComponentSelector) {
+                    return callSelector(colDef.tooltipComponentSelector, params);
+                }
+                if (!colDef.tooltipComponent) {
+                    return undefined;
+                }
+                return { component: colDef.tooltipComponent, params: colDef.tooltipComponentParams };
+            }
+            if (leafTooltipComponentSelector) {
+                return callSelector(leafTooltipComponentSelector, params);
+            }
+            if (leafTooltipComponent == null) {
+                return undefined;
+            }
+            return { component: leafTooltipComponent, params: leafTooltipComponentParams };
+        };
+        res.tooltipComponentSelector = selector as unknown as ColDef['tooltipComponentSelector'];
+    }
+
     private createBaseColDef(rowGroupCol?: AgColumn): ColDef {
         const userDef = this.gos.get('autoGroupColumnDef');
         const localeTextFunc = this.getLocaleTextFunc();
@@ -252,6 +353,12 @@ export class AutoColService extends BeanStub implements NamedBean, IAutoColServi
         if (rowGroupCol) {
             res.headerName = this.beans.colNames.getDisplayNameForColumn(rowGroupCol, 'header') ?? undefined;
             res.headerValueGetter = rowGroupCol.colDef.headerValueGetter;
+            res.headerTooltip = rowGroupCol.colDef.headerTooltip;
+            res.tooltipField = rowGroupCol.colDef.tooltipField;
+            res.tooltipValueGetter = rowGroupCol.colDef.tooltipValueGetter;
+            res.tooltipComponent = rowGroupCol.colDef.tooltipComponent;
+            res.tooltipComponentParams = rowGroupCol.colDef.tooltipComponentParams;
+            res.tooltipComponentSelector = rowGroupCol.colDef.tooltipComponentSelector;
         }
         return res;
     }
diff --git a/packages/ag-stack/src/rendering/agPositionableFeature.ts b/packages/ag-stack/src/rendering/agPositionableFeature.ts
index 4f6a23d741c..9340178f199 100644
--- a/packages/ag-stack/src/rendering/agPositionableFeature.ts
+++ b/packages/ag-stack/src/rendering/agPositionableFeature.ts
@@ -370,7 +370,9 @@ export class AgPositionableFeature<
             }
         }
 
-        if (this.getHeight() === height) {
+        // only skip when a height style is already in place: on the first sizing pass the measured
+        // height can match the target before any style is set, which would leave the panel unsized.
+        if (eGui.style.height !== '' && this.getHeight() === height) {
             return;
         }
 
diff --git a/testing/behavioural/src/tooltip/tooltip-group-col-inheritance.test.ts b/testing/behavioural/src/tooltip/tooltip-group-col-inheritance.test.ts
new file mode 100644
index 00000000000..32c0ea061b1
--- /dev/null
+++ b/testing/behavioural/src/tooltip/tooltip-group-col-inheritance.test.ts
@@ -0,0 +1,405 @@
+import { getByTestId, waitFor } from '@testing-library/dom';
+import { userEvent } from '@testing-library/user-event';
+
+import { GROUP_AUTO_COLUMN_ID, TooltipModule, agTestIdFor, getGridElement, setupAgTestIds } from 'ag-grid-community';
+import type { GridOptions, ITooltipComp, ITooltipParams, Module } from 'ag-grid-community';
+import { RowGroupingModule } from 'ag-grid-enterprise';
+
+import { GridColumns, GridRows, TestGridsManager, asyncSetTimeout } from '../test-utils';
+
+describe('Tooltip inheritance in group columns', () => {
+    const gridMgr = new TestGridsManager({
+        includeDefaultModules: true,
+        modules: [TooltipModule, RowGroupingModule] as Module[],
+    });
+
+    beforeAll(() => setupAgTestIds());
+    afterEach(() => gridMgr.reset());
+
+    const TOOLTIP_SHOW_DELAY = 200;
+
+    const getTooltips = () => Array.from(document.querySelectorAll<HTMLElement>('.ag-tooltip, .ag-tooltip-custom'));
+    const waitForTooltips = async (count: number) =>
+        await waitFor(() => expect(getTooltips().length).toBe(count), { timeout: 2000 });
+
+    // TC2 – single column grouping: group cell inherits tooltipValueGetter from underlying colDef
+    test('group cell inherits tooltipValueGetter when grouped (singleColumn)', async () => {
+        const gridOptions: GridOptions = {
+            columnDefs: [
+                {
+                    field: 'country',
+                    rowGroup: true,
+                    hide: true,
+                    tooltipValueGetter: (params) => `Tooltip: ${params.value}`,
+                },
+                { field: 'athlete' },
+            ],
+            rowData: [{ country: 'Australia', athlete: 'Alice' }],
+            tooltipShowDelay: TOOLTIP_SHOW_DELAY,
+        };
+
+        const api = await gridMgr.createGridAndWait('tooltip-group-single', gridOptions);
+        await new GridColumns(api, 'group cell inherits tooltipValueGetter (singleColumn) setup').checkColumns(`
+            CENTER
+            ├── ag-Grid-AutoColumn "Group" width:200
+            └── athlete "Athlete" width:200
+        `);
+        await new GridRows(api, 'group cell inherits tooltipValueGetter (singleColumn) setup').check(`
+            ROOT id:ROOT_NODE_ID
+            └─┬ LEAF_GROUP collapsed id:row-group-country-Australia ag-Grid-AutoColumn:"Australia"
+            · └── LEAF hidden id:0 country:"Australia" athlete:"Alice"
+        `);
+
+        const gridDiv = getGridElement(api)! as HTMLElement;
+        const groupCell = await waitFor(() =>
+            getByTestId(gridDiv, agTestIdFor.autoGroupCell('row-group-country-Australia'))
+        );
+
+        await userEvent.hover(groupCell);
+        await asyncSetTimeout(TOOLTIP_SHOW_DELAY + 50);
+        await waitForTooltips(1);
+        expect(getTooltips()[0]).toHaveTextContent('Tooltip: Australia');
+        await new GridRows(api, 'group cell inherits tooltipValueGetter (singleColumn) final state').check(`
+            ROOT id:ROOT_NODE_ID
+            └─┬ LEAF_GROUP collapsed id:row-group-country-Australia ag-Grid-AutoColumn:"Australia"
+            · └── LEAF hidden id:0 country:"Australia" athlete:"Alice"
+        `);
+    });
+
+    // TC2 – multiple column grouping: group cell inherits tooltipValueGetter from underlying colDef
+    test('group cell inherits tooltipValueGetter when grouped (multipleColumns)', async () => {
+        const gridOptions: GridOptions = {
+            columnDefs: [
+                {
+                    field: 'country',
+                    rowGroup: true,
+                    hide: true,
+                    tooltipValueGetter: (params) => `Country: ${params.value}`,
+                },
+                { field: 'athlete' },
+            ],
+            rowData: [{ country: 'Australia', athlete: 'Alice' }],
+            groupDisplayType: 'multipleColumns',
+            tooltipShowDelay: TOOLTIP_SHOW_DELAY,
+        };
+
+        const api = await gridMgr.createGridAndWait('tooltip-group-multiple', gridOptions);
+        await new GridColumns(api, 'group cell inherits tooltipValueGetter (multipleColumns) setup').checkColumns(`
+            CENTER
+            ├── ag-Grid-AutoColumn-country "Country" width:200
+            └── athlete "Athlete" width:200
+        `);
+        await new GridRows(api, 'group cell inherits tooltipValueGetter (multipleColumns) setup').check(`
+            ROOT id:ROOT_NODE_ID ag-Grid-AutoColumn-country:null
+            └─┬ LEAF_GROUP collapsed id:row-group-country-Australia ag-Grid-AutoColumn-country:"Australia"
+            · └── LEAF hidden id:0 country:"Australia" athlete:"Alice"
+        `);
+
+        const gridDiv = getGridElement(api)! as HTMLElement;
+        const autoColId = `${GROUP_AUTO_COLUMN_ID}-country`;
+        const groupCell = await waitFor(() =>
+            getByTestId(gridDiv, agTestIdFor.cell('row-group-country-Australia', autoColId))
+        );
+
+        await userEvent.hover(groupCell);
+        await asyncSetTimeout(TOOLTIP_SHOW_DELAY + 50);
+        await waitForTooltips(1);
+        expect(getTooltips()[0]).toHaveTextContent('Country: Australia');
+        await new GridRows(api, 'group cell inherits tooltipValueGetter (multipleColumns) final state').check(`
+            ROOT id:ROOT_NODE_ID ag-Grid-AutoColumn-country:null
+            └─┬ LEAF_GROUP collapsed id:row-group-country-Australia ag-Grid-AutoColumn-country:"Australia"
+            · └── LEAF hidden id:0 country:"Australia" athlete:"Alice"
+        `);
+    });
+
+    // TC2 – tooltipField is inherited (singleColumn)
+    test('group cell inherits tooltipField from underlying colDef', async () => {
+        const gridOptions: GridOptions = {
+            columnDefs: [
+                { field: 'country', rowGroup: true, hide: true, tooltipField: 'country' },
+                { field: 'athlete' },
+            ],
+            rowData: [{ country: 'Australia', athlete: 'Alice' }],
+            tooltipShowDelay: TOOLTIP_SHOW_DELAY,
+        };
+
+        const api = await gridMgr.createGridAndWait('tooltip-group-field', gridOptions);
+        await new GridColumns(api, 'group cell inherits tooltipField setup').checkColumns(`
+            CENTER
+            ├── ag-Grid-AutoColumn "Group" width:200
+            └── athlete "Athlete" width:200
+        `);
+        await new GridRows(api, 'group cell inherits tooltipField setup').check(`
+            ROOT id:ROOT_NODE_ID
+            └─┬ LEAF_GROUP collapsed id:row-group-country-Australia ag-Grid-AutoColumn:"Australia"
+            · └── LEAF hidden id:0 country:"Australia" athlete:"Alice"
+        `);
+
+        const gridDiv = getGridElement(api)! as HTMLElement;
+        const groupCell = await waitFor(() =>
+            getByTestId(gridDiv, agTestIdFor.autoGroupCell('row-group-country-Australia'))
+        );
+
+        await userEvent.hover(groupCell);
+        await asyncSetTimeout(TOOLTIP_SHOW_DELAY + 50);
+        await waitForTooltips(1);
+        expect(getTooltips()[0]).toHaveTextContent('Australia');
+        await new GridRows(api, 'group cell inherits tooltipField final state').check(`
+            ROOT id:ROOT_NODE_ID
+            └─┬ LEAF_GROUP collapsed id:row-group-country-Australia ag-Grid-AutoColumn:"Australia"
+            · └── LEAF hidden id:0 country:"Australia" athlete:"Alice"
+        `);
+    });
+
+    // TC4 – grouped header inherits headerTooltip from underlying colDef (multipleColumns)
+    test('grouped header inherits headerTooltip from underlying colDef (multipleColumns)', async () => {
+        const gridOptions: GridOptions = {
+            columnDefs: [
+                { field: 'country', rowGroup: true, hide: true, headerTooltip: 'Country header tooltip' },
+                { field: 'athlete' },
+            ],
+            rowData: [{ country: 'Australia', athlete: 'Alice' }],
+            groupDisplayType: 'multipleColumns',
+            tooltipShowDelay: TOOLTIP_SHOW_DELAY,
+        };
+
+        const api = await gridMgr.createGridAndWait('tooltip-group-header', gridOptions);
+        await new GridColumns(api, 'grouped header inherits headerTooltip (multipleColumns) setup').checkColumns(`
+            CENTER
+            ├── ag-Grid-AutoColumn-country "Country" width:200
+            └── athlete "Athlete" width:200
+        `);
+        await new GridRows(api, 'grouped header inherits headerTooltip (multipleColumns) setup').check(`
+            ROOT id:ROOT_NODE_ID ag-Grid-AutoColumn-country:null
+            └─┬ LEAF_GROUP collapsed id:row-group-country-Australia ag-Grid-AutoColumn-country:"Australia"
+            · └── LEAF hidden id:0 country:"Australia" athlete:"Alice"
+        `);
+
+        const gridDiv = getGridElement(api)! as HTMLElement;
+        const autoColId = `${GROUP_AUTO_COLUMN_ID}-country`;
+        const headerCell = await waitFor(() => getByTestId(gridDiv, agTestIdFor.headerCell(autoColId)));
+
+        await userEvent.hover(headerCell);
+        await asyncSetTimeout(TOOLTIP_SHOW_DELAY + 50);
+        await waitForTooltips(1);
+        expect(getTooltips()[0]).toHaveTextContent('Country header tooltip');
+        await new GridRows(api, 'grouped header inherits headerTooltip (multipleColumns) final state').check(`
+            ROOT id:ROOT_NODE_ID ag-Grid-AutoColumn-country:null
+            └─┬ LEAF_GROUP collapsed id:row-group-country-Australia ag-Grid-AutoColumn-country:"Australia"
+            · └── LEAF hidden id:0 country:"Australia" athlete:"Alice"
+        `);
+    });
+
+    // TC5 – leaf rows in the group column use autoGroupColumnDef tooltip settings
+    test('leaf rows use autoGroupColumnDef tooltipValueGetter', async () => {
+        const gridOptions: GridOptions = {
+            columnDefs: [{ field: 'country', rowGroup: true, hide: true }, { field: 'athlete' }],
+            autoGroupColumnDef: {
+                field: 'athlete',
+                tooltipValueGetter: (params) => `Leaf: ${params.value}`,
+            },
+            rowData: [{ country: 'Australia', athlete: 'Alice' }],
+            tooltipShowDelay: TOOLTIP_SHOW_DELAY,
+        };
+
+        const api = await gridMgr.createGridAndWait('tooltip-group-leaf', gridOptions);
+        await new GridColumns(api, 'leaf rows use autoGroupColumnDef tooltipValueGetter setup').checkColumns(`
+            CENTER
+            ├── ag-Grid-AutoColumn "Group" width:200
+            └── athlete "Athlete" width:200
+        `);
+        await new GridRows(api, 'leaf rows use autoGroupColumnDef tooltipValueGetter setup').check(`
+            ROOT id:ROOT_NODE_ID
+            └─┬ LEAF_GROUP collapsed id:row-group-country-Australia ag-Grid-AutoColumn:"Australia"
+            · └── LEAF hidden id:0 ag-Grid-AutoColumn:"Alice" country:"Australia" athlete:"Alice"
+        `);
+
+        api.setRowNodeExpanded(api.getRowNode('row-group-country-Australia')!, true);
+
+        const gridDiv = getGridElement(api)! as HTMLElement;
+        const leafCell = await waitFor(() => getByTestId(gridDiv, agTestIdFor.autoGroupCell('0')));
+
+        await userEvent.hover(leafCell);
+        await asyncSetTimeout(TOOLTIP_SHOW_DELAY + 50);
+        await waitForTooltips(1);
+        expect(getTooltips()[0]).toHaveTextContent('Leaf: Alice');
+        await new GridRows(api, 'leaf rows use autoGroupColumnDef tooltipValueGetter final state').check(`
+            ROOT id:ROOT_NODE_ID
+            └─┬ LEAF_GROUP id:row-group-country-Australia ag-Grid-AutoColumn:"Australia"
+            · └── LEAF id:0 ag-Grid-AutoColumn:"Alice" country:"Australia" athlete:"Alice"
+        `);
+    });
+
+    // group rows always use underlying colDef tooltip even when autoGroupColumnDef also sets one
+    test('group rows use underlying colDef tooltip, ignoring autoGroupColumnDef tooltipValueGetter', async () => {
+        const gridOptions: GridOptions = {
+            columnDefs: [
+                {
+                    field: 'country',
+                    rowGroup: true,
+                    hide: true,
+                    tooltipValueGetter: () => 'Inherited tooltip',
+                },
+                { field: 'athlete' },
+            ],
+            autoGroupColumnDef: {
+                tooltipValueGetter: () => 'autoGroupColumnDef tooltip',
+            },
+            rowData: [{ country: 'Australia', athlete: 'Alice' }],
+            tooltipShowDelay: TOOLTIP_SHOW_DELAY,
+        };
+
+        const api = await gridMgr.createGridAndWait('tooltip-group-override', gridOptions);
+        await new GridColumns(api, 'group rows use underlying colDef tooltip setup').checkColumns(`
+            CENTER
+            ├── ag-Grid-AutoColumn "Group" width:200
+            └── athlete "Athlete" width:200
+        `);
+        await new GridRows(api, 'group rows use underlying colDef tooltip setup').check(`
+            ROOT id:ROOT_NODE_ID
+            └─┬ LEAF_GROUP collapsed id:row-group-country-Australia ag-Grid-AutoColumn:"Australia"
+            · └── LEAF hidden id:0 country:"Australia" athlete:"Alice"
+        `);
+
+        const gridDiv = getGridElement(api)! as HTMLElement;
+        const groupCell = await waitFor(() =>
+            getByTestId(gridDiv, agTestIdFor.autoGroupCell('row-group-country-Australia'))
+        );
+
+        await userEvent.hover(groupCell);
+        await asyncSetTimeout(TOOLTIP_SHOW_DELAY + 50);
+        await waitForTooltips(1);
+        expect(getTooltips()[0]).toHaveTextContent('Inherited tooltip');
+        await new GridRows(api, 'group rows use underlying colDef tooltip final state').check(`
+            ROOT id:ROOT_NODE_ID
+            └─┬ LEAF_GROUP collapsed id:row-group-country-Australia ag-Grid-AutoColumn:"Australia"
+            · └── LEAF hidden id:0 country:"Australia" athlete:"Alice"
+        `);
+    });
+
+    // tooltipComponentSelector is inherited by the auto group column (multipleColumns)
+    test('group column inherits tooltipComponentSelector (multipleColumns)', async () => {
+        class CustomTooltip implements ITooltipComp {
+            private eGui!: HTMLElement;
+            init(params: ITooltipParams) {
+                this.eGui = document.createElement('div');
+                this.eGui.className = 'ag-tooltip-custom custom-selector-tooltip';
+                this.eGui.textContent = `selector:${params.value}`;
+            }
+            getGui() {
+                return this.eGui;
+            }
+        }
+
+        const gridOptions: GridOptions = {
+            columnDefs: [
+                {
+                    field: 'country',
+                    rowGroup: true,
+                    hide: true,
+                    tooltipValueGetter: (params) => params.value,
+                    tooltipComponentSelector: () => ({ component: CustomTooltip }),
+                },
+                { field: 'athlete' },
+            ],
+            rowData: [{ country: 'Australia', athlete: 'Alice' }],
+            groupDisplayType: 'multipleColumns',
+            tooltipShowDelay: TOOLTIP_SHOW_DELAY,
+        };
+
+        const api = await gridMgr.createGridAndWait('tooltip-group-selector-multiple', gridOptions);
+        await new GridColumns(api, 'group column inherits tooltipComponentSelector (multipleColumns) setup')
+            .checkColumns(`
+            CENTER
+            ├── ag-Grid-AutoColumn-country "Country" width:200
+            └── athlete "Athlete" width:200
+        `);
+        await new GridRows(api, 'group column inherits tooltipComponentSelector (multipleColumns) setup').check(`
+            ROOT id:ROOT_NODE_ID ag-Grid-AutoColumn-country:null
+            └─┬ LEAF_GROUP collapsed id:row-group-country-Australia ag-Grid-AutoColumn-country:"Australia"
+            · └── LEAF hidden id:0 country:"Australia" athlete:"Alice"
+        `);
+
+        const gridDiv = getGridElement(api)! as HTMLElement;
+        const autoColId = `${GROUP_AUTO_COLUMN_ID}-country`;
+        const groupCell = await waitFor(() =>
+            getByTestId(gridDiv, agTestIdFor.cell('row-group-country-Australia', autoColId))
+        );
+
+        await userEvent.hover(groupCell);
+        await asyncSetTimeout(TOOLTIP_SHOW_DELAY + 50);
+        await waitForTooltips(1);
+        expect(document.querySelector('.custom-selector-tooltip')).not.toBeNull();
+        expect(getTooltips()[0]).toHaveTextContent('selector:Australia');
+        await new GridRows(api, 'group column inherits tooltipComponentSelector (multipleColumns) final state').check(
+            `
+                ROOT id:ROOT_NODE_ID ag-Grid-AutoColumn-country:null
+                └─┬ LEAF_GROUP collapsed id:row-group-country-Australia ag-Grid-AutoColumn-country:"Australia"
+                · └── LEAF hidden id:0 country:"Australia" athlete:"Alice"
+            `
+        );
+    });
+
+    // tooltipComponentSelector on the source column is dispatched in singleColumn mode
+    test('group cell uses tooltipComponentSelector from source column (singleColumn)', async () => {
+        class CustomTooltip implements ITooltipComp {
+            private eGui!: HTMLElement;
+            init(params: ITooltipParams) {
+                this.eGui = document.createElement('div');
+                this.eGui.className = 'ag-tooltip-custom custom-selector-tooltip';
+                this.eGui.textContent = `selector:${params.value}`;
+            }
+            getGui() {
+                return this.eGui;
+            }
+        }
+
+        const gridOptions: GridOptions = {
+            columnDefs: [
+                {
+                    field: 'country',
+                    rowGroup: true,
+                    hide: true,
+                    tooltipValueGetter: (params) => params.value,
+                    tooltipComponentSelector: () => ({ component: CustomTooltip }),
+                },
+                { field: 'athlete' },
+            ],
+            rowData: [{ country: 'Australia', athlete: 'Alice' }],
+            tooltipShowDelay: TOOLTIP_SHOW_DELAY,
+        };
+
+        const api = await gridMgr.createGridAndWait('tooltip-group-selector-single', gridOptions);
+        await new GridColumns(api, 'group cell uses tooltipComponentSelector from source column (singleColumn) setup')
+            .checkColumns(`
+            CENTER
+            ├── ag-Grid-AutoColumn "Group" width:200
+            └── athlete "Athlete" width:200
+        `);
+        await new GridRows(api, 'group cell uses tooltipComponentSelector from source column (singleColumn) setup')
+            .check(`
+            ROOT id:ROOT_NODE_ID
+            └─┬ LEAF_GROUP collapsed id:row-group-country-Australia ag-Grid-AutoColumn:"Australia"
+            · └── LEAF hidden id:0 country:"Australia" athlete:"Alice"
+        `);
+
+        const gridDiv = getGridElement(api)! as HTMLElement;
+        const groupCell = await waitFor(() =>
+            getByTestId(gridDiv, agTestIdFor.autoGroupCell('row-group-country-Australia'))
+        );
+
+        await userEvent.hover(groupCell);
+        await asyncSetTimeout(TOOLTIP_SHOW_DELAY + 50);
+        await waitForTooltips(1);
+        expect(document.querySelector('.custom-selector-tooltip')).not.toBeNull();
+        expect(getTooltips()[0]).toHaveTextContent('selector:Australia');
+        await new GridRows(
+            api,
+            'group cell uses tooltipComponentSelector from source column (singleColumn) final state'
+        ).check(`
+            ROOT id:ROOT_NODE_ID
+            └─┬ LEAF_GROUP collapsed id:row-group-country-Australia ag-Grid-AutoColumn:"Australia"
+            · └── LEAF hidden id:0 country:"Australia" athlete:"Alice"
+        `);
+    });
+});
diff --git a/yarn.lock b/yarn.lock
index bd7adf7020f..40ea0f2f0a7 100644
--- a/yarn.lock
+++ b/yarn.lock
@@ -19299,7 +19299,7 @@ pretty-ms@^9.2.0:
   dependencies:
     parse-ms "^4.0.0"
 
-prismjs@^1.29.0, prismjs@^1.30.0:
+prismjs@^1.30.0:
   version "1.30.0"
   resolved "https://registry.ag-grid.com/prismjs/-/prismjs-1.30.0.tgz#d9709969d9d4e16403f6f348c63553b19f0975a9"
   integrity sha512-DEvV2ZF2r2/63V+tK8hQvrR2ZGn10srHbXviTlcv7Kpzw8jWiNTqbVgjO3IY8RxrrOUF8VPMQQFysYYYv0YZxw==
@@ -21567,7 +21567,16 @@ string-length@^4.0.2:
     char-regex "^1.0.2"
     strip-ansi "^6.0.0"
 
-"string-width-cjs@npm:string-width@^4.2.0", "string-width@^1.0.2 || 2 || 3 || 4", string-width@^4.1.0, string-width@^4.2.0, string-width@^4.2.3:
+"string-width-cjs@npm:string-width@^4.2.0":
+  version "4.2.3"
+  resolved "https://registry.ag-grid.com/string-width/-/string-width-4.2.3.tgz#269c7117d27b05ad2e536830a8ec895ef9c6d010"
+  integrity sha512-wKyQRQpjJ0sIp62ErSZdGsjMJWsap5oRNihHhu6G7JVO/9jIB6UyevL+tXuOqrng8j/cxKTWyWUwvSTriiZz/g==
+  dependencies:
+    emoji-regex "^8.0.0"
+    is-fullwidth-code-point "^3.0.0"
+    strip-ansi "^6.0.1"
+
+"string-width@^1.0.2 || 2 || 3 || 4", string-width@^4.1.0, string-width@^4.2.0, string-width@^4.2.3:
   version "4.2.3"
   resolved "https://registry.ag-grid.com/string-width/-/string-width-4.2.3.tgz#269c7117d27b05ad2e536830a8ec895ef9c6d010"
   integrity sha512-wKyQRQpjJ0sIp62ErSZdGsjMJWsap5oRNihHhu6G7JVO/9jIB6UyevL+tXuOqrng8j/cxKTWyWUwvSTriiZz/g==
@@ -21680,7 +21689,7 @@ stringify-entities@^4.0.0:
     character-entities-html4 "^2.0.0"
     character-entities-legacy "^3.0.0"
 
-"strip-ansi-cjs@npm:strip-ansi@^6.0.1", strip-ansi@^6.0.0, strip-ansi@^6.0.1:
+"strip-ansi-cjs@npm:strip-ansi@^6.0.1":
   version "6.0.1"
   resolved "https://registry.ag-grid.com/strip-ansi/-/strip-ansi-6.0.1.tgz#9e26c63d30f53443e9489495b2105d37b67a85d9"
   integrity sha512-Y38VPSHcqkFrCpFnQ9vuSXmquuv5oXOKpGeT6aGrr3o3Gc9AlVa6JBfUSOCnbxGGZF+/0ooI7KrPuUSztUdU5A==
@@ -21694,6 +21703,13 @@ strip-ansi@^5.0.0, strip-ansi@^5.1.0, strip-ansi@^5.2.0:
   dependencies:
     ansi-regex "^4.1.0"
 
+strip-ansi@^6.0.0, strip-ansi@^6.0.1:
+  version "6.0.1"
+  resolved "https://registry.ag-grid.com/strip-ansi/-/strip-ansi-6.0.1.tgz#9e26c63d30f53443e9489495b2105d37b67a85d9"
+  integrity sha512-Y38VPSHcqkFrCpFnQ9vuSXmquuv5oXOKpGeT6aGrr3o3Gc9AlVa6JBfUSOCnbxGGZF+/0ooI7KrPuUSztUdU5A==
+  dependencies:
+    ansi-regex "^5.0.1"
+
 strip-ansi@^7.0.1, strip-ansi@^7.1.0:
   version "7.1.2"
   resolved "https://registry.ag-grid.com/strip-ansi/-/strip-ansi-7.1.2.tgz#132875abde678c7ea8d691533f2e7e22bb744dba"
@@ -23963,7 +23979,7 @@ wordwrap@^1.0.0:
   resolved "https://registry.ag-grid.com/wordwrap/-/wordwrap-1.0.0.tgz#27584810891456a4171c8d0226441ade90cbcaeb"
   integrity sha512-gvVzJFlPycKc5dZN4yPkP8w7Dc37BtP1yczEneOb4uq34pXZcvrtRTmWV8W+Ume+XCxKgbjM+nevkyFPMybd4Q==
 
-"wrap-ansi-cjs@npm:wrap-ansi@^7.0.0", wrap-ansi@^7.0.0:
+"wrap-ansi-cjs@npm:wrap-ansi@^7.0.0":
   version "7.0.0"
   resolved "https://registry.ag-grid.com/wrap-ansi/-/wrap-ansi-7.0.0.tgz#67e145cff510a6a6984bdf1152911d69d2eb9e43"
   integrity sha512-YVGIj2kamLSTxw6NsZjoBxfSwsn0ycdesmc4p+Q21c5zPuZ1pl+NfxVdxPtdHvmNVOQ6XSYG4AUtyt/Fi7D16Q==
@@ -23990,6 +24006,15 @@ wrap-ansi@^6.2.0:
     string-width "^4.1.0"
     strip-ansi "^6.0.0"
 
+wrap-ansi@^7.0.0:
+  version "7.0.0"
+  resolved "https://registry.ag-grid.com/wrap-ansi/-/wrap-ansi-7.0.0.tgz#67e145cff510a6a6984bdf1152911d69d2eb9e43"
+  integrity sha512-YVGIj2kamLSTxw6NsZjoBxfSwsn0ycdesmc4p+Q21c5zPuZ1pl+NfxVdxPtdHvmNVOQ6XSYG4AUtyt/Fi7D16Q==
+  dependencies:
+    ansi-styles "^4.0.0"
+    string-width "^4.1.0"
+    strip-ansi "^6.0.0"
+
 wrap-ansi@^8.1.0:
   version "8.1.0"
   resolved "https://registry.ag-grid.com/wrap-ansi/-/wrap-ansi-8.1.0.tgz#56dc22368ee570face1b49819975d9b9a5ead214"