diff --git a/src/hooks/useNoteOperations.test.ts b/src/hooks/useNoteOperations.test.ts
new file mode 100644
index 0000000..ae111ea
--- /dev/null
+++ b/src/hooks/useNoteOperations.test.ts
@@ -0,0 +1,182 @@
+import { act, renderHook } from '@testing-library/react';
+import { beforeEach, describe, expect, it, vi } from 'vitest';
+
+type SelectableItem = { getId: () => string };
+
+const coreState = {
+  selectedItems: [] as SelectableItem[],
+  selectionChangedCallbacks: [] as Array<() => void>,
+  executeCommand: vi.fn(),
+};
+
+const projectStoreState = {
+  selectedNoteIds: [] as string[],
+  clearAllSelections: () => {
+    coreState.selectedItems = [];
+    syncSelectionFromCore();
+  },
+  bumpAutomationRedrawVersion: vi.fn(),
+  syncSelectionFromCore: () => {
+    syncSelectionFromCore();
+  },
+};
+
+const syncSelectionFromCore = () => {
+  projectStoreState.selectedNoteIds = coreState.selectedItems.map(item => item.getId());
+  coreState.selectionChangedCallbacks.forEach(callback => callback());
+};
+
+vi.mock('../core/KGCore', () => ({
+  KGCore: {
+    instance: () => ({
+      getSelectedItems: () => coreState.selectedItems,
+      addSelectedItem: (item: SelectableItem) => {
+        coreState.selectedItems = coreState.selectedItems.filter(selectedItem => selectedItem.getId() !== item.getId());
+        coreState.selectedItems.push(item);
+        syncSelectionFromCore();
+      },
+      addSelectedItems: (items: SelectableItem[]) => {
+        const incomingIds = new Set(items.map(item => item.getId()));
+        coreState.selectedItems = coreState.selectedItems.filter(item => !incomingIds.has(item.getId()));
+        coreState.selectedItems.push(...items);
+        syncSelectionFromCore();
+      },
+      clearSelectedItems: () => {
+        coreState.selectedItems = [];
+        syncSelectionFromCore();
+      },
+      executeCommand: (...args: unknown[]) => coreState.executeCommand(...args),
+      onSelectionChanged: (callback: () => void) => {
+        coreState.selectionChangedCallbacks.push(callback);
+      },
+    }),
+  },
+}));
+
+vi.mock('../stores/projectStore', () => ({
+  useProjectStore: Object.assign(vi.fn(), {
+    getState: () => projectStoreState,
+  }),
+}));
+
+import { useNoteOperations } from './useNoteOperations';
+import { KGCore } from '../core/KGCore';
+import { KGPianoRollState } from '../core/state/KGPianoRollState';
+import { ResizeNotesCommand } from '../core/commands';
+import { useProjectStore } from '../stores/projectStore';
+import { createMockMidiNote, createMockMidiRegion, createMockMidiTrack } from '../test/utils/mock-data';
+
+describe('useNoteOperations', () => {
+  beforeEach(() => {
+    vi.restoreAllMocks();
+    coreState.selectedItems = [];
+    coreState.selectionChangedCallbacks = [];
+    coreState.executeCommand = vi.fn();
+    projectStoreState.selectedNoteIds = [];
+    projectStoreState.bumpAutomationRedrawVersion.mockReset();
+
+    vi.spyOn(window, 'getComputedStyle').mockReturnValue({
+      getPropertyValue: (property: string) => {
+        if (property === '--region-grid-beat-width') {
+          return '40';
+        }
+
+        if (property === '--region-piano-key-height') {
+          return '20';
+        }
+
+        return '';
+      },
+    } as CSSStyleDeclaration);
+
+    KGPianoRollState.instance().setActiveTool('pointer');
+  });
+
+  it('selects the grabbed note before resizing when it was not part of the current selection', () => {
+    const noteA = createMockMidiNote({ id: 'note-a', startBeat: 0, endBeat: 1, pitch: 60 });
+    const noteB = createMockMidiNote({ id: 'note-b', startBeat: 1, endBeat: 2, pitch: 62 });
+    const noteC = createMockMidiNote({ id: 'note-c', startBeat: 2, endBeat: 3, pitch: 64 });
+    const activeRegion = createMockMidiRegion({
+      id: 'region-1',
+      trackId: '1',
+      notes: [noteA, noteB, noteC],
+    });
+    const track = createMockMidiTrack({ id: 1, regions: [activeRegion] });
+    const updateTrack = vi.fn();
+
+    noteA.select();
+    noteB.select();
+    KGCore.instance().addSelectedItems([noteA, noteB]);
+
+    const { result } = renderHook(() => useNoteOperations({
+      activeRegion,
+      timeSignature: { numerator: 4, denominator: 4 },
+      updateTrack,
+      tracks: [track],
+      pianoGridRef: { current: null },
+    }));
+
+    act(() => {
+      result.current.handleNoteResizeStart(noteC.getId(), 'end', 120);
+    });
+
+    expect(KGCore.instance().getSelectedItems().map(item => item.getId())).toEqual([noteC.getId()]);
+    expect(useProjectStore.getState().selectedNoteIds).toEqual([noteC.getId()]);
+    expect(noteA.isSelected()).toBe(false);
+    expect(noteB.isSelected()).toBe(false);
+    expect(noteC.isSelected()).toBe(true);
+
+    act(() => {
+      result.current.handleNoteResizeEnd(noteC.getId(), 'end');
+    });
+
+    expect(coreState.executeCommand).toHaveBeenCalledTimes(1);
+    const resizeCommand = coreState.executeCommand.mock.calls[0][0];
+    expect(resizeCommand).toBeInstanceOf(ResizeNotesCommand);
+    expect((resizeCommand as ResizeNotesCommand).getNoteIdsToResize()).toEqual([noteC.getId()]);
+  });
+
+  it('keeps the existing multi-selection when resizing a selected note', () => {
+    const noteA = createMockMidiNote({ id: 'note-a', startBeat: 0, endBeat: 1, pitch: 60 });
+    const noteB = createMockMidiNote({ id: 'note-b', startBeat: 1, endBeat: 2, pitch: 62 });
+    const noteC = createMockMidiNote({ id: 'note-c', startBeat: 2, endBeat: 3, pitch: 64 });
+    const activeRegion = createMockMidiRegion({
+      id: 'region-1',
+      trackId: '1',
+      notes: [noteA, noteB, noteC],
+    });
+    const track = createMockMidiTrack({ id: 1, regions: [activeRegion] });
+    const updateTrack = vi.fn();
+
+    noteA.select();
+    noteB.select();
+    KGCore.instance().addSelectedItems([noteA, noteB]);
+
+    const { result } = renderHook(() => useNoteOperations({
+      activeRegion,
+      timeSignature: { numerator: 4, denominator: 4 },
+      updateTrack,
+      tracks: [track],
+      pianoGridRef: { current: null },
+    }));
+
+    act(() => {
+      result.current.handleNoteResizeStart(noteA.getId(), 'end', 0);
+    });
+
+    expect(KGCore.instance().getSelectedItems().map(item => item.getId())).toEqual([noteA.getId(), noteB.getId()]);
+    expect(useProjectStore.getState().selectedNoteIds).toEqual([noteA.getId(), noteB.getId()]);
+    expect(noteA.isSelected()).toBe(true);
+    expect(noteB.isSelected()).toBe(true);
+    expect(noteC.isSelected()).toBe(false);
+
+    act(() => {
+      result.current.handleNoteResizeEnd(noteA.getId(), 'end');
+    });
+
+    expect(coreState.executeCommand).toHaveBeenCalledTimes(1);
+    const resizeCommand = coreState.executeCommand.mock.calls[0][0];
+    expect(resizeCommand).toBeInstanceOf(ResizeNotesCommand);
+    expect((resizeCommand as ResizeNotesCommand).getNoteIdsToResize()).toEqual([noteA.getId(), noteB.getId()]);
+  });
+});
diff --git a/src/hooks/useNoteOperations.ts b/src/hooks/useNoteOperations.ts
index 3a36b0b..8a7c040 100644
--- a/src/hooks/useNoteOperations.ts
+++ b/src/hooks/useNoteOperations.ts
@@ -279,6 +279,28 @@ export const useNoteOperations = ({
     // Find the note being resized
     const note = activeRegion.getNotes().find(n => n.getId() === noteId);
     if (!note) return;
+
+    const selectedNotesInRegion = core.getSelectedItems().filter(item =>
+      item instanceof KGMidiNote &&
+      activeRegion.getNotes().some(regionNote => regionNote.getId() === item.getId())
+    ) as KGMidiNote[];
+    const isResizedNoteSelected = selectedNotesInRegion.some(selectedNote => selectedNote.getId() === noteId);
+
+    if (!isResizedNoteSelected) {
+      selectedNotesInRegion.forEach(selectedNote => {
+        selectedNote.deselect();
+      });
+      useProjectStore.getState().clearAllSelections();
+
+      note.select();
+      core.addSelectedItem(note);
+      KGPianoRollState.instance().setLastEditedNoteLength(note.getEndBeat() - note.getStartBeat());
+
+      const track = tracks.find(t => t.getId().toString() === activeRegion.getTrackId());
+      if (track) {
+        updateTrack(track);
+      }
+    }
     
     // Store the initial start and end beats
     initialStartBeatRef.current = note.getStartBeat();