diff --git a/packages/core/src/editor/index.ts b/packages/core/src/editor/index.ts
index 6f266d20c..d7d955d74 100644
--- a/packages/core/src/editor/index.ts
+++ b/packages/core/src/editor/index.ts
@@ -1,6 +1,7 @@
 export { createDefaultEditorState, createEditor } from './create'
 export type { Editor } from './create'
 export { createTextActions } from './text'
+export { opacityFromBuffer } from './nodes'
 export { EDITOR_TOOLS, TOOL_SHORTCUTS } from './tool-registry'
 export type { EditorToolDef } from './tool-registry'
 export type {
diff --git a/packages/core/src/editor/nodes.ts b/packages/core/src/editor/nodes.ts
index f00fa443c..ce19f306d 100644
--- a/packages/core/src/editor/nodes.ts
+++ b/packages/core/src/editor/nodes.ts
@@ -8,6 +8,15 @@ import { textAutoResizeChanges } from './text/auto-resize'
 import type { EditorContext } from './types'
 import { createVariableBindingActions } from './variable-bindings'
 
+export function opacityFromBuffer(buffer: string): number {
+  if (buffer === '0') return 1
+  if (!/^\d+$/.test(buffer)) return 1
+  const n = Number.parseInt(buffer, 10)
+  if (!Number.isFinite(n)) return 1
+  const percent = buffer.length === 1 ? n * 10 : n
+  return Math.min(100, Math.max(0, percent)) / 100
+}
+
 export function createNodeActions(ctx: EditorContext) {
   const layoutModeActions = createLayoutModeActions(ctx)
   const nudgeActions = createNudgeActions(ctx)
@@ -51,9 +60,29 @@ export function createNodeActions(ctx: EditorContext) {
     ctx.requestRender()
   }
 
+  function setOpacity(opacity: number, coalesceKey?: string) {
+    if (!Number.isFinite(opacity)) return
+    const clamped = Math.max(0, Math.min(1, opacity))
+    const ids = [...ctx.state.selectedIds]
+    if (ids.length === 0) return
+    const targets = ids.map((id) => ctx.graph.getNode(id)).filter((n): n is SceneNode => n != null)
+    const changed = targets.filter((t) => t.opacity !== clamped)
+    if (changed.length === 0) return
+    ctx.undo.runBatch(
+      'Set opacity',
+      () => {
+        for (const target of changed) {
+          updateNodeWithUndo(target.id, { opacity: clamped }, 'Set opacity')
+        }
+      },
+      coalesceKey
+    )
+  }
+
   return {
     updateNode,
     updateNodeWithUndo,
+    setOpacity,
     ...layoutModeActions,
     ...variableBindingActions,
     ...nudgeActions
diff --git a/packages/scene-graph/src/undo.ts b/packages/scene-graph/src/undo.ts
index af9780c23..268aa556f 100644
--- a/packages/scene-graph/src/undo.ts
+++ b/packages/scene-graph/src/undo.ts
@@ -2,6 +2,7 @@ export interface UndoEntry {
   label: string
   forward: () => void
   inverse: () => void
+  coalesceKey?: string
 }
 
 export interface UndoManagerOptions {
@@ -11,6 +12,7 @@ export interface UndoManagerOptions {
 interface UndoBatch {
   label: string
   entries: UndoEntry[]
+  coalesceKey?: string
 }
 
 const DEFAULT_HISTORY_LIMIT = 200
@@ -63,8 +65,8 @@ export class UndoManager {
     return entry.label
   }
 
-  beginBatch(label: string): void {
-    this.batches.push({ label, entries: [] })
+  beginBatch(label: string, coalesceKey?: string): void {
+    this.batches.push({ label, entries: [], coalesceKey })
   }
 
   commitBatch(): void {
@@ -77,8 +79,8 @@ export class UndoManager {
     else this.pushUndoEntry(entry)
   }
 
-  runBatch<T>(label: string, fn: () => T): T {
-    this.beginBatch(label)
+  runBatch<T>(label: string, fn: () => T, coalesceKey?: string): T {
+    this.beginBatch(label, coalesceKey)
     try {
       const result = fn()
       this.commitBatch()
@@ -129,12 +131,21 @@ export class UndoManager {
     return {
       label: batch.label,
       forward: () => batch.entries.forEach((entry) => entry.forward()),
-      inverse: () => batch.entries.toReversed().forEach((entry) => entry.inverse())
+      inverse: () => batch.entries.toReversed().forEach((entry) => entry.inverse()),
+      coalesceKey: batch.coalesceKey
     }
   }
 
   private pushUndoEntry(entry: UndoEntry): void {
-    this.undoStack.push(entry)
+    const previous = this.undoStack.at(-1)
+    if (entry.coalesceKey && previous?.coalesceKey === entry.coalesceKey) {
+      this.undoStack[this.undoStack.length - 1] = {
+        ...entry,
+        inverse: previous.inverse
+      }
+    } else {
+      this.undoStack.push(entry)
+    }
     this.redoStack = []
     this.trimUndoStack()
   }
diff --git a/packages/vue/src/editor/commands/context.ts b/packages/vue/src/editor/commands/context.ts
index 634d70899..aa6f989e3 100644
--- a/packages/vue/src/editor/commands/context.ts
+++ b/packages/vue/src/editor/commands/context.ts
@@ -16,4 +16,5 @@ export type EditorCommandMapOptions = {
   messages: CommandMessagesStore
   otherPages: ComputedRef<Array<{ id: string }>>
   moveSelectionToPage: (pageId: string) => void
+  getOpacityTarget: () => { value: number; coalesceKey?: string }
 }
diff --git a/packages/vue/src/editor/commands/registry.ts b/packages/vue/src/editor/commands/registry.ts
index 77e4de0ee..319f7c2ec 100644
--- a/packages/vue/src/editor/commands/registry.ts
+++ b/packages/vue/src/editor/commands/registry.ts
@@ -96,6 +96,7 @@ export const EDITOR_COMMAND_METADATA = {
   'selection.outlineText': { contextTestId: 'context-outline-text' },
   'selection.outlineStroke': { contextTestId: 'context-outline-stroke' },
   'selection.moveToPage': {},
+  'selection.setOpacity': { shortcut: '1-9, 0' },
   'view.zoom100': { keybinding: '$mod+Digit0' },
   'view.zoomFit': { keybinding: ['$mod+Digit1', 'Shift+Digit1'] },
   'view.zoomSelection': { keybinding: ['$mod+Digit2', 'Shift+Digit2'] }
diff --git a/packages/vue/src/editor/commands/selection.ts b/packages/vue/src/editor/commands/selection.ts
index 151984b02..6047e4d96 100644
--- a/packages/vue/src/editor/commands/selection.ts
+++ b/packages/vue/src/editor/commands/selection.ts
@@ -29,7 +29,8 @@ export function createSelectionCommands({
   capabilities,
   messages: t,
   otherPages,
-  moveSelectionToPage
+  moveSelectionToPage,
+  getOpacityTarget
 }: EditorCommandMapOptions): Record<SelectionCommandId, EditorCommand> {
   return {
     'selection.selectAll': {
@@ -261,6 +262,17 @@ export function createSelectionCommands({
       run: () => {
         moveSelectionToPage(otherPages.value[0].id)
       }
+    },
+    'selection.setOpacity': {
+      id: 'selection.setOpacity',
+      get label() {
+        return t.value.setOpacity
+      },
+      enabled: capabilities.canSetOpacity,
+      run: () => {
+        const target = getOpacityTarget()
+        editor.setOpacity(target.value, target.coalesceKey)
+      }
     }
   }
 }
diff --git a/packages/vue/src/editor/commands/types.ts b/packages/vue/src/editor/commands/types.ts
index 2e341182c..a3a2b272d 100644
--- a/packages/vue/src/editor/commands/types.ts
+++ b/packages/vue/src/editor/commands/types.ts
@@ -30,6 +30,7 @@ export type EditorCommandId =
   | 'selection.outlineText'
   | 'selection.outlineStroke'
   | 'selection.moveToPage'
+  | 'selection.setOpacity'
   | 'view.zoom100'
   | 'view.zoomFit'
   | 'view.zoomSelection'
diff --git a/packages/vue/src/editor/commands/use.ts b/packages/vue/src/editor/commands/use.ts
index 0f9ff9b41..b98e4851f 100644
--- a/packages/vue/src/editor/commands/use.ts
+++ b/packages/vue/src/editor/commands/use.ts
@@ -41,19 +41,26 @@ export function useEditorCommands() {
     editor.moveToPage(pageId)
   }
 
+  let opacityTarget: { value: number; coalesceKey?: string } = { value: 1 }
+  function setOpacityTarget(value: number, coalesceKey?: string) {
+    opacityTarget = coalesceKey ? { value, coalesceKey } : { value }
+  }
+
   const commands = createEditorCommandMap({
     editor,
     selection,
     capabilities,
     messages: t,
     otherPages,
-    moveSelectionToPage
+    moveSelectionToPage,
+    getOpacityTarget: () => opacityTarget
   })
 
   return {
     commands,
     otherPages,
     moveSelectionToPage,
+    setOpacityTarget,
     ...createEditorCommandActions(commands)
   }
 }
diff --git a/packages/vue/src/editor/selection-capabilities/use.ts b/packages/vue/src/editor/selection-capabilities/use.ts
index a11653f12..a77edd80f 100644
--- a/packages/vue/src/editor/selection-capabilities/use.ts
+++ b/packages/vue/src/editor/selection-capabilities/use.ts
@@ -66,6 +66,7 @@ export function useSelectionCapabilities() {
     canGoToMainComponent: computed(() => selection.isInstance.value),
     canCreateInstance: computed(() => selectedNode.value?.type === 'COMPONENT'),
     canMoveToPage: useSceneComputed(() => hasSelection.value && editor.graph.getPages().length > 1),
+    canSetOpacity: computed(() => hasSelection.value),
     canSelectAll: useSceneComputed(
       () => editor.graph.getChildren(editor.state.currentPageId).length > 0
     ),
diff --git a/packages/vue/src/i18n/locales/de/commands.json b/packages/vue/src/i18n/locales/de/commands.json
index 642538812..d411cdc11 100644
--- a/packages/vue/src/i18n/locales/de/commands.json
+++ b/packages/vue/src/i18n/locales/de/commands.json
@@ -15,6 +15,7 @@
   "bringToFront": "In den Vordergrund",
   "sendToBack": "In den Hintergrund",
   "moveToPage": "Auf Seite verschieben",
+  "setOpacity": "Deckkraft festlegen",
   "zoomTo100": "Zoom 100 %",
   "zoomToFit": "Einpassen",
   "zoomToSelection": "Auswahl einpassen",
diff --git a/packages/vue/src/i18n/locales/es/commands.json b/packages/vue/src/i18n/locales/es/commands.json
index 427c5095f..7587ca63e 100644
--- a/packages/vue/src/i18n/locales/es/commands.json
+++ b/packages/vue/src/i18n/locales/es/commands.json
@@ -15,6 +15,7 @@
   "bringToFront": "Traer al frente",
   "sendToBack": "Enviar al fondo",
   "moveToPage": "Mover a página",
+  "setOpacity": "Establecer opacidad",
   "zoomTo100": "Zoom 100 %",
   "zoomToFit": "Ajustar a pantalla",
   "zoomToSelection": "Zoom a selección",
diff --git a/packages/vue/src/i18n/locales/fr/commands.json b/packages/vue/src/i18n/locales/fr/commands.json
index fd470a22b..a76efb041 100644
--- a/packages/vue/src/i18n/locales/fr/commands.json
+++ b/packages/vue/src/i18n/locales/fr/commands.json
@@ -15,6 +15,7 @@
   "bringToFront": "Mettre au premier plan",
   "sendToBack": "Mettre en arrière-plan",
   "moveToPage": "Déplacer vers la page",
+  "setOpacity": "Définir l'opacité",
   "zoomTo100": "Zoom 100 %",
   "zoomToFit": "Ajuster à l'écran",
   "zoomToSelection": "Zoom sur la sélection",
diff --git a/packages/vue/src/i18n/locales/it/commands.json b/packages/vue/src/i18n/locales/it/commands.json
index a9542c114..be2f1dd71 100644
--- a/packages/vue/src/i18n/locales/it/commands.json
+++ b/packages/vue/src/i18n/locales/it/commands.json
@@ -15,6 +15,7 @@
   "bringToFront": "Porta in primo piano",
   "sendToBack": "Porta in secondo piano",
   "moveToPage": "Sposta nella pagina",
+  "setOpacity": "Imposta opacità",
   "zoomTo100": "Zoom 100%",
   "zoomToFit": "Adatta allo schermo",
   "zoomToSelection": "Zoom sulla selezione",
diff --git a/packages/vue/src/i18n/locales/ja/commands.json b/packages/vue/src/i18n/locales/ja/commands.json
index 426d1a306..f83c011d7 100644
--- a/packages/vue/src/i18n/locales/ja/commands.json
+++ b/packages/vue/src/i18n/locales/ja/commands.json
@@ -15,6 +15,7 @@
   "bringToFront": "最前面へ移動",
   "sendToBack": "最背面へ移動",
   "moveToPage": "ページへ移動",
+  "setOpacity": "不透明度を設定",
   "zoomTo100": "100%にズーム",
   "zoomToFit": "画面に合わせる",
   "zoomToSelection": "選択範囲にズーム",
diff --git a/packages/vue/src/i18n/locales/pl/commands.json b/packages/vue/src/i18n/locales/pl/commands.json
index 32482b1b6..09db34849 100644
--- a/packages/vue/src/i18n/locales/pl/commands.json
+++ b/packages/vue/src/i18n/locales/pl/commands.json
@@ -15,6 +15,7 @@
   "bringToFront": "Przenieś na wierzch",
   "sendToBack": "Przenieś na spód",
   "moveToPage": "Przenieś na stronę",
+  "setOpacity": "Ustaw krycie",
   "zoomTo100": "Zoom 100%",
   "zoomToFit": "Dopasuj do ekranu",
   "zoomToSelection": "Zoom do zaznaczenia",
diff --git a/packages/vue/src/i18n/locales/ru/commands.json b/packages/vue/src/i18n/locales/ru/commands.json
index 57e59500f..25a100df3 100644
--- a/packages/vue/src/i18n/locales/ru/commands.json
+++ b/packages/vue/src/i18n/locales/ru/commands.json
@@ -15,6 +15,7 @@
   "bringToFront": "На передний план",
   "sendToBack": "На задний план",
   "moveToPage": "Переместить на страницу",
+  "setOpacity": "Задать непрозрачность",
   "zoomTo100": "Масштаб 100%",
   "zoomToFit": "Вписать в экран",
   "zoomToSelection": "Масштаб по выделению",
diff --git a/packages/vue/src/i18n/locales/zh-cn/commands.json b/packages/vue/src/i18n/locales/zh-cn/commands.json
index 99138a415..ab222b8e3 100644
--- a/packages/vue/src/i18n/locales/zh-cn/commands.json
+++ b/packages/vue/src/i18n/locales/zh-cn/commands.json
@@ -15,6 +15,7 @@
   "bringToFront": "置于顶层",
   "sendToBack": "置于底层",
   "moveToPage": "移动到页面",
+  "setOpacity": "设置不透明度",
   "zoomTo100": "缩放到 100%",
   "zoomToFit": "适应屏幕",
   "zoomToSelection": "适应所选内容",
diff --git a/packages/vue/src/i18n/messages/commands.ts b/packages/vue/src/i18n/messages/commands.ts
index da696cfa6..1dd11b669 100644
--- a/packages/vue/src/i18n/messages/commands.ts
+++ b/packages/vue/src/i18n/messages/commands.ts
@@ -33,6 +33,7 @@ export const commandMessageDefaults = {
   flipHorizontal: 'Flip horizontal',
   flipVertical: 'Flip vertical',
   moveToPage: 'Move to page',
+  setOpacity: 'Set opacity',
   zoomTo100: 'Zoom to 100%',
   zoomToFit: 'Zoom to fit',
   zoomToSelection: 'Zoom to selection'
diff --git a/src/app/shell/keyboard/actions.ts b/src/app/shell/keyboard/actions.ts
index 5d7f7c4e9..83805e537 100644
--- a/src/app/shell/keyboard/actions.ts
+++ b/src/app/shell/keyboard/actions.ts
@@ -1,5 +1,6 @@
 import type { Ref } from 'vue'
 
+import { opacityFromBuffer } from '@open-pencil/core/editor'
 import type { useEditorCommands, useViewportKind } from '@open-pencil/vue'
 
 import type { EditorStore } from '@/app/editor/active-store'
@@ -9,13 +10,15 @@ type KeyboardActionsOptions = {
   activeTab: Ref<'design' | 'code' | 'ai'>
   isMobile: ReturnType<typeof useViewportKind>['isMobile']
   runCommand: ReturnType<typeof useEditorCommands>['runCommand']
+  setOpacityTarget: ReturnType<typeof useEditorCommands>['setOpacityTarget']
 }
 
 export function createKeyboardActions({
   store,
   activeTab,
   isMobile,
-  runCommand
+  runCommand,
+  setOpacityTarget
 }: KeyboardActionsOptions) {
   function hasNodeEditSelection() {
     return (
@@ -98,6 +101,34 @@ export function createKeyboardActions({
     if (store.state.selectedIds.size > 0) void store.exportSelection(1, 'png')
   }
 
+  let opacityBuffer = ''
+  let opacitySelectionKey = ''
+  let opacityCoalesceKey = ''
+  let opacityResetTimer: ReturnType<typeof setTimeout> | undefined
+
+  function resetOpacityBuffer() {
+    opacityBuffer = ''
+    opacitySelectionKey = ''
+    opacityCoalesceKey = ''
+    clearTimeout(opacityResetTimer)
+  }
+
+  function opacityDigit(digit: string) {
+    if (store.state.selectedIds.size === 0) return
+    const selectionKey = [...store.state.selectedIds].sort().join('\0')
+    if (selectionKey !== opacitySelectionKey) resetOpacityBuffer()
+    if (!opacityBuffer) {
+      opacitySelectionKey = selectionKey
+      opacityCoalesceKey = crypto.randomUUID()
+    }
+    opacityBuffer += digit
+    if (opacityBuffer.length > 3) opacityBuffer = opacityBuffer.slice(-3)
+    setOpacityTarget(opacityFromBuffer(opacityBuffer), opacityCoalesceKey)
+    runCommand('selection.setOpacity')
+    clearTimeout(opacityResetTimer)
+    opacityResetTimer = setTimeout(resetOpacityBuffer, 800)
+  }
+
   return {
     smartDelete,
     confirmOrEnterText,
@@ -105,6 +136,7 @@ export function createKeyboardActions({
     toggleAutoLayout,
     toggleUI,
     toggleAI,
-    exportSelectionPng
+    exportSelectionPng,
+    opacityDigit
   }
 }
diff --git a/src/app/shell/keyboard/registry.ts b/src/app/shell/keyboard/registry.ts
index c6ba53d29..a9706c83e 100644
--- a/src/app/shell/keyboard/registry.ts
+++ b/src/app/shell/keyboard/registry.ts
@@ -20,6 +20,7 @@ type ShortcutDefinition = {
   id: string
   keys: string | string[]
   run: ShortcutAction
+  shouldPreventDefault?: (event: KeyboardEvent) => boolean
 }
 
 function commandShortcut(
@@ -36,6 +37,19 @@ function commandShortcuts(...commands: EditorCommandId[]): ShortcutDefinition[]
   })
 }
 
+function opacityBindings(): ShortcutDefinition[] {
+  return ['0', '1', '2', '3', '4', '5', '6', '7', '8', '9'].map((digit) => ({
+    id: `selection-opacity-${digit}`,
+    keys: digit,
+    run: ({ keyEvent, actions }) => {
+      if (keyEvent.metaKey || keyEvent.ctrlKey || keyEvent.altKey || keyEvent.shiftKey) return
+      actions.opacityDigit(digit)
+    },
+    shouldPreventDefault: (event) =>
+      !event.metaKey && !event.ctrlKey && !event.altKey && !event.shiftKey
+  }))
+}
+
 function shouldIgnoreShortcut(event: KeyboardEvent, options: KeyboardShortcutOptions) {
   return (
     (event.target instanceof Element && event.target.closest('[data-picker-content]') !== null) ||
@@ -136,7 +150,8 @@ export function registerKeyboardShortcuts(options: KeyboardShortcutOptions) {
     { id: 'delete', keys: 'Delete', run: ({ actions }) => actions.smartDelete(false) },
     { id: 'delete-alt', keys: 'Alt+Delete', run: ({ actions }) => actions.smartDelete(true) },
     { id: 'enter', keys: 'Enter', run: ({ actions }) => actions.confirmOrEnterText() },
-    { id: 'escape', keys: 'Escape', run: ({ actions }) => actions.escapeOrDeselect() }
+    { id: 'escape', keys: 'Escape', run: ({ actions }) => actions.escapeOrDeselect() },
+    ...opacityBindings()
   ]
 
   const bindings: KeyBindingMap = {}
@@ -144,8 +159,8 @@ export function registerKeyboardShortcuts(options: KeyboardShortcutOptions) {
 
   for (const shortcut of shortcuts) {
     bindShortcut(bindings, shortcut.keys, (event) => {
-      event.preventDefault()
       shortcut.run(runOptions(event))
+      if (shortcut.shouldPreventDefault?.(event) ?? true) event.preventDefault()
     })
   }
 
diff --git a/src/app/shell/keyboard/types.ts b/src/app/shell/keyboard/types.ts
index b0e311060..d4c3d2a15 100644
--- a/src/app/shell/keyboard/types.ts
+++ b/src/app/shell/keyboard/types.ts
@@ -12,6 +12,7 @@ export type KeyboardShortcutActions = {
   toggleUI: () => void
   toggleAI: () => void
   exportSelectionPng: () => void
+  opacityDigit: (digit: string) => void
 }
 
 export type KeyboardShortcutOptions = {
diff --git a/src/app/shell/keyboard/use.ts b/src/app/shell/keyboard/use.ts
index 6eaa56b2f..38abea9c5 100644
--- a/src/app/shell/keyboard/use.ts
+++ b/src/app/shell/keyboard/use.ts
@@ -17,11 +17,17 @@ export function useKeyboard() {
   const { activeTab } = useAIChat()
   const store = useEditorStore()
   const { isMobile } = useViewportKind()
-  const { runCommand } = useEditorCommands()
+  const { runCommand, setOpacityTarget } = useEditorCommands()
   const activeElement = useActiveElement()
   const inputFocused = computed(() => isInputElement(activeElement.value))
 
-  const actions = createKeyboardActions({ store, activeTab, isMobile, runCommand })
+  const actions = createKeyboardActions({
+    store,
+    activeTab,
+    isMobile,
+    runCommand,
+    setOpacityTarget
+  })
 
   bindEditorClipboard(store)
   bindNudgeKeys(store)
diff --git a/tests/e2e/keyboard/shortcuts.spec.ts b/tests/e2e/keyboard/shortcuts.spec.ts
index 328c4185a..c3746c256 100644
--- a/tests/e2e/keyboard/shortcuts.spec.ts
+++ b/tests/e2e/keyboard/shortcuts.spec.ts
@@ -48,6 +48,15 @@ function getZoom() {
   })
 }
 
+function getSelectedOpacity() {
+  return editor.page.evaluate(() => {
+    const store = window.openPencil?.getStore?.()
+    if (!store) throw new Error('OpenPencil store not initialized')
+    const id = [...store.state.selectedIds][0]
+    return id ? store.graph.getNode(id)?.opacity : undefined
+  })
+}
+
 test.describe('tool switching', () => {
   test('V → SELECT', async () => {
     await editor.page.keyboard.press('v')
@@ -222,6 +231,56 @@ test.describe('duplicate', () => {
   })
 })
 
+test.describe('opacity shortcuts', () => {
+  test.beforeEach(async () => {
+    await editor.canvas.clearCanvas()
+    await editor.canvas.drawRect(100, 100, 60, 60)
+  })
+
+  test('combines digits and undoes them as one interaction', async () => {
+    await editor.page.keyboard.press('2')
+    await editor.page.keyboard.press('8')
+    expect(await getSelectedOpacity()).toBe(0.28)
+
+    await editor.page.keyboard.press('Meta+z')
+    expect(await getSelectedOpacity()).toBe(1)
+
+    await editor.page.keyboard.press('Meta+Shift+z')
+    expect(await getSelectedOpacity()).toBe(0.28)
+  })
+
+  test('maps 0 to 100% and 00 to 0%', async () => {
+    await editor.page.keyboard.press('5')
+    expect(await getSelectedOpacity()).toBe(0.5)
+
+    await editor.canvas.clearCanvas()
+    await editor.canvas.drawRect(100, 100, 60, 60)
+    await editor.page.keyboard.press('0')
+    expect(await getSelectedOpacity()).toBe(1)
+    await editor.page.keyboard.press('0')
+    expect(await getSelectedOpacity()).toBe(0)
+  })
+
+  test('does not consume shifted digits or NumLock-off navigation keys', async () => {
+    await editor.page.keyboard.press('5')
+    await editor.page.keyboard.press('Shift+1')
+    expect(await getSelectedOpacity()).toBe(0.5)
+
+    const prevented = await editor.page.evaluate(() => {
+      const event = new KeyboardEvent('keydown', {
+        key: 'End',
+        code: 'Numpad1',
+        bubbles: true,
+        cancelable: true
+      })
+      window.dispatchEvent(event)
+      return event.defaultPrevented
+    })
+    expect(prevented).toBe(false)
+    expect(await getSelectedOpacity()).toBe(0.5)
+  })
+})
+
 test.describe('zoom shortcuts', () => {
   test('⌘0 zooms to 100%', async () => {
     await editor.canvas.clearCanvas()
diff --git a/tests/engine/editor/opacity.test.ts b/tests/engine/editor/opacity.test.ts
new file mode 100644
index 000000000..c2cbb378d
--- /dev/null
+++ b/tests/engine/editor/opacity.test.ts
@@ -0,0 +1,187 @@
+import { describe, test, expect } from 'bun:test'
+
+import { createEditor, opacityFromBuffer } from '@open-pencil/core/editor'
+
+import { getNodeOrThrow } from '#tests/helpers/assert'
+
+describe('editor.setOpacity', () => {
+  function setup() {
+    const editor = createEditor()
+    const pageId = editor.graph.getPages()[0].id
+    const rect = editor.graph.createNode('RECTANGLE', pageId, {
+      name: 'Rect',
+      x: 0,
+      y: 0,
+      width: 50,
+      height: 50
+    })
+    editor.select([rect.id])
+    return { editor, rect }
+  }
+
+  test('sets opacity to 50%', () => {
+    const { editor, rect } = setup()
+
+    editor.setOpacity(0.5)
+    expect(getNodeOrThrow(editor.graph, rect.id).opacity).toBe(0.5)
+  })
+
+  test('sets opacity to 100% (digit 0)', () => {
+    const { editor, rect } = setup()
+
+    editor.setOpacity(0.5)
+    editor.setOpacity(1)
+    expect(getNodeOrThrow(editor.graph, rect.id).opacity).toBe(1)
+  })
+
+  test('clamps opacity above 100%', () => {
+    const { editor, rect } = setup()
+
+    editor.setOpacity(1.5)
+    expect(getNodeOrThrow(editor.graph, rect.id).opacity).toBe(1)
+  })
+
+  test('clamps opacity below 0%', () => {
+    const { editor, rect } = setup()
+
+    editor.setOpacity(-0.3)
+    expect(getNodeOrThrow(editor.graph, rect.id).opacity).toBe(0)
+  })
+
+  test('opacity change is undoable as a single batch entry', () => {
+    const { editor, rect } = setup()
+
+    editor.setOpacity(0.3)
+    expect(editor.undo.canUndo).toBe(true)
+
+    editor.undo.undo()
+    expect(getNodeOrThrow(editor.graph, rect.id).opacity).toBe(1)
+
+    editor.undo.redo()
+    expect(getNodeOrThrow(editor.graph, rect.id).opacity).toBe(0.3)
+  })
+
+  test('coalesces buffered shortcut updates into one undo entry', () => {
+    const { editor, rect } = setup()
+
+    editor.setOpacity(0.2, 'shortcut-session')
+    editor.setOpacity(0.28, 'shortcut-session')
+
+    editor.undo.undo()
+    expect(getNodeOrThrow(editor.graph, rect.id).opacity).toBe(1)
+
+    editor.undo.redo()
+    expect(getNodeOrThrow(editor.graph, rect.id).opacity).toBe(0.28)
+  })
+
+  test('keeps separate shortcut sessions as separate undo entries', () => {
+    const { editor, rect } = setup()
+
+    editor.setOpacity(0.2, 'shortcut-session-1')
+    editor.setOpacity(0.8, 'shortcut-session-2')
+
+    editor.undo.undo()
+    expect(getNodeOrThrow(editor.graph, rect.id).opacity).toBe(0.2)
+    editor.undo.undo()
+    expect(getNodeOrThrow(editor.graph, rect.id).opacity).toBe(1)
+  })
+
+  test('opacity batch for multiple selections collapses to one undo entry', () => {
+    const { editor, rect } = setup()
+    const pageId = editor.graph.getPages()[0].id
+    const rect2 = editor.graph.createNode('RECTANGLE', pageId, {
+      name: 'Rect2',
+      x: 100,
+      y: 0,
+      width: 50,
+      height: 50
+    })
+    editor.select([rect.id, rect2.id])
+
+    editor.setOpacity(0.7)
+    expect(getNodeOrThrow(editor.graph, rect.id).opacity).toBe(0.7)
+    expect(getNodeOrThrow(editor.graph, rect2.id).opacity).toBe(0.7)
+
+    editor.undo.undo()
+    expect(getNodeOrThrow(editor.graph, rect.id).opacity).toBe(1)
+    expect(getNodeOrThrow(editor.graph, rect2.id).opacity).toBe(1)
+  })
+
+  test('no-op when opacity already matches', () => {
+    const { editor, rect } = setup()
+
+    editor.setOpacity(1)
+    expect(getNodeOrThrow(editor.graph, rect.id).opacity).toBe(1)
+    expect(editor.undo.canUndo).toBe(false)
+  })
+
+  test('no-op with no selection', () => {
+    const { editor } = setup()
+
+    editor.clearSelection()
+    editor.setOpacity(0.5)
+    expect(editor.undo.canUndo).toBe(false)
+  })
+
+  test('rejects NaN', () => {
+    const { editor, rect } = setup()
+
+    editor.setOpacity(Number.NaN)
+    expect(getNodeOrThrow(editor.graph, rect.id).opacity).toBe(1)
+    expect(editor.undo.canUndo).toBe(false)
+  })
+
+  test('rejects Infinity', () => {
+    const { editor, rect } = setup()
+
+    editor.setOpacity(Number.POSITIVE_INFINITY)
+    expect(getNodeOrThrow(editor.graph, rect.id).opacity).toBe(1)
+    expect(editor.undo.canUndo).toBe(false)
+  })
+
+  test('rejects -Infinity', () => {
+    const { editor, rect } = setup()
+
+    editor.setOpacity(Number.NEGATIVE_INFINITY)
+    expect(getNodeOrThrow(editor.graph, rect.id).opacity).toBe(1)
+    expect(editor.undo.canUndo).toBe(false)
+  })
+})
+
+describe('opacityFromBuffer', () => {
+  test('single 0 returns 100%', () => {
+    expect(opacityFromBuffer('0')).toBe(1)
+  })
+
+  test('single digit returns decena', () => {
+    expect(opacityFromBuffer('5')).toBe(0.5)
+    expect(opacityFromBuffer('2')).toBe(0.2)
+    expect(opacityFromBuffer('9')).toBe(0.9)
+  })
+
+  test('two digits returns literal percent', () => {
+    expect(opacityFromBuffer('28')).toBe(0.28)
+    expect(opacityFromBuffer('35')).toBe(0.35)
+    expect(opacityFromBuffer('00')).toBe(0)
+    expect(opacityFromBuffer('05')).toBe(0.05)
+  })
+
+  test('three digits clamps to 100%', () => {
+    expect(opacityFromBuffer('100')).toBe(1)
+    expect(opacityFromBuffer('150')).toBe(1)
+  })
+
+  test('invalid buffer returns 100%', () => {
+    expect(opacityFromBuffer('')).toBe(1)
+    expect(opacityFromBuffer('abc')).toBe(1)
+  })
+
+  test('rejects partially numeric buffers', () => {
+    expect(opacityFromBuffer('12x')).toBe(1)
+    expect(opacityFromBuffer('5abc')).toBe(1)
+    expect(opacityFromBuffer('3.5')).toBe(1)
+    expect(opacityFromBuffer('1e2')).toBe(1)
+    expect(opacityFromBuffer('-5')).toBe(1)
+    expect(opacityFromBuffer(' 5')).toBe(1)
+  })
+})