diff --git a/packages/runtime-vapor/__tests__/scopeId.spec.ts b/packages/runtime-vapor/__tests__/scopeId.spec.ts
new file mode 100644
index 000000000..a0ea12e70
--- /dev/null
+++ b/packages/runtime-vapor/__tests__/scopeId.spec.ts
@@ -0,0 +1,341 @@
+import { createApp, h } from '@vue/runtime-dom'
+import {
+  createComponent,
+  createDynamicComponent,
+  createSlot,
+  defineVaporComponent,
+  setInsertionState,
+  template,
+  vaporInteropPlugin,
+} from '../src'
+import { makeRender } from './_utils'
+
+const define = makeRender()
+
+describe('scopeId', () => {
+  test('should attach scopeId to child component', () => {
+    const Child = defineVaporComponent({
+      __scopeId: 'child',
+      setup() {
+        return template('<div child></div>', true)()
+      },
+    })
+
+    const { html } = define({
+      __scopeId: 'parent',
+      setup() {
+        const t0 = template('<div parent></div>', true)
+        const n1 = t0() as any
+        setInsertionState(n1)
+        createComponent(Child)
+        return n1
+      },
+    }).render()
+    expect(html()).toBe(`<div parent=""><div child="" parent=""></div></div>`)
+  })
+
+  test('should attach scopeId to nested child component', () => {
+    const Child = defineVaporComponent({
+      __scopeId: 'child',
+      setup() {
+        return template('<div child></div>', true)()
+      },
+    })
+
+    const Parent = defineVaporComponent({
+      __scopeId: 'parent',
+      setup() {
+        return createComponent(Child)
+      },
+    })
+
+    const { html } = define({
+      __scopeId: 'app',
+      setup() {
+        const t0 = template('<div app></div>', true)
+        const n1 = t0() as any
+        setInsertionState(n1)
+        createComponent(Parent)
+        return n1
+      },
+    }).render()
+    expect(html()).toBe(
+      `<div app=""><div child="" parent="" app=""></div></div>`,
+    )
+  })
+
+  test('should attach scopeId to child dynamic component', () => {
+    const { html } = define({
+      __scopeId: 'parent',
+      setup() {
+        const t0 = template('<div parent></div>', true)
+        const n1 = t0() as any
+        setInsertionState(n1)
+        createDynamicComponent(() => 'button')
+        return n1
+      },
+    }).render()
+    expect(html()).toBe(
+      `<div parent=""><button parent=""></button><!--dynamic-component--></div>`,
+    )
+  })
+
+  test('should attach scopeId to dynamic component', () => {
+    const { html } = define({
+      __scopeId: 'parent',
+      setup() {
+        const t0 = template('<div parent></div>', true)
+        const n1 = t0() as any
+        setInsertionState(n1)
+        createDynamicComponent(() => 'button')
+        return n1
+      },
+    }).render()
+    expect(html()).toBe(
+      `<div parent=""><button parent=""></button><!--dynamic-component--></div>`,
+    )
+  })
+
+  test('should attach scopeId to nested dynamic component', () => {
+    const Comp = defineVaporComponent({
+      __scopeId: 'child',
+      setup() {
+        return createDynamicComponent(() => 'button', null, null, true)
+      },
+    })
+    const { html } = define({
+      __scopeId: 'parent',
+      setup() {
+        const t0 = template('<div parent></div>', true)
+        const n1 = t0() as any
+        setInsertionState(n1)
+        createComponent(Comp, null, null, true)
+        return n1
+      },
+    }).render()
+    expect(html()).toBe(
+      `<div parent=""><button child="" parent=""></button><!--dynamic-component--></div>`,
+    )
+  })
+
+  test.todo('should attach scopeId to suspense content', async () => {})
+
+  // :slotted basic
+  test.todo('should work on slots', () => {
+    const Child = defineVaporComponent({
+      __scopeId: 'child',
+      setup() {
+        const n1 = template('<div child></div>', true)() as any
+        setInsertionState(n1)
+        createSlot('default', null)
+        return n1
+      },
+    })
+
+    const Child2 = defineVaporComponent({
+      __scopeId: 'child2',
+      setup() {
+        return template('<span child2></span>', true)()
+      },
+    })
+
+    const { html } = define({
+      __scopeId: 'parent',
+      setup() {
+        const n2 = createComponent(
+          Child,
+          null,
+          {
+            default: () => {
+              const n0 = template('<div parent></div>')()
+              const n1 = createComponent(Child2)
+              return [n0, n1]
+            },
+          },
+          true,
+        )
+        return n2
+      },
+    }).render()
+
+    expect(html()).toBe(
+      `<div child="" parent="">` +
+        `<div parent="" child-s=""></div>` +
+        // component inside slot should have:
+        // - scopeId from template context
+        // - slotted scopeId from slot owner
+        // - its own scopeId
+        `<span child2="" child="" parent="" child-s=""></span>` +
+        `<!--slot-->` +
+        `</div>`,
+    )
+  })
+
+  test.todo(':slotted on forwarded slots', async () => {})
+})
+
+describe('vdom interop', () => {
+  test('vdom parent > vapor child', () => {
+    const VaporChild = defineVaporComponent({
+      __scopeId: 'vapor-child',
+      setup() {
+        return template('<button vapor-child></button>', true)()
+      },
+    })
+
+    const VdomChild = {
+      __scopeId: 'vdom-child',
+      setup() {
+        return () => h(VaporChild as any)
+      },
+    }
+
+    const App = {
+      __scopeId: 'parent',
+      setup() {
+        return () => h(VdomChild)
+      },
+    }
+
+    const root = document.createElement('div')
+    createApp(App).use(vaporInteropPlugin).mount(root)
+
+    expect(root.innerHTML).toBe(
+      `<button vapor-child="" vdom-child="" parent=""></button>`,
+    )
+  })
+
+  test('vdom parent > vapor > vdom child', () => {
+    const InnerVdomChild = {
+      __scopeId: 'inner-vdom-child',
+      setup() {
+        return () => h('button')
+      },
+    }
+
+    const VaporChild = defineVaporComponent({
+      __scopeId: 'vapor-child',
+      setup() {
+        return createComponent(InnerVdomChild as any, null, null, true)
+      },
+    })
+
+    const VdomChild = {
+      __scopeId: 'vdom-child',
+      setup() {
+        return () => h(VaporChild as any)
+      },
+    }
+
+    const App = {
+      __scopeId: 'parent',
+      setup() {
+        return () => h(VdomChild)
+      },
+    }
+
+    const root = document.createElement('div')
+    createApp(App).use(vaporInteropPlugin).mount(root)
+
+    expect(root.innerHTML).toBe(
+      `<button inner-vdom-child="" vapor-child="" vdom-child="" parent=""></button>`,
+    )
+  })
+
+  test('vdom parent > vapor dynamic child', () => {
+    const VaporChild = defineVaporComponent({
+      __scopeId: 'vapor-child',
+      setup() {
+        return createDynamicComponent(() => 'button', null, null, true)
+      },
+    })
+
+    const VdomChild = {
+      __scopeId: 'vdom-child',
+      setup() {
+        return () => h(VaporChild as any)
+      },
+    }
+
+    const App = {
+      __scopeId: 'parent',
+      setup() {
+        return () => h(VdomChild)
+      },
+    }
+
+    const root = document.createElement('div')
+    createApp(App).use(vaporInteropPlugin).mount(root)
+
+    expect(root.innerHTML).toBe(
+      `<button vapor-child="" vdom-child="" parent=""></button><!--dynamic-component-->`,
+    )
+  })
+
+  test('vapor parent > vdom child', () => {
+    const VdomChild = {
+      __scopeId: 'vdom-child',
+      setup() {
+        return () => h('button')
+      },
+    }
+
+    const VaporChild = defineVaporComponent({
+      __scopeId: 'vapor-child',
+      setup() {
+        return createComponent(VdomChild as any, null, null, true)
+      },
+    })
+
+    const App = {
+      __scopeId: 'parent',
+      setup() {
+        return () => h(VaporChild as any)
+      },
+    }
+
+    const root = document.createElement('div')
+    createApp(App).use(vaporInteropPlugin).mount(root)
+
+    expect(root.innerHTML).toBe(
+      `<button vdom-child="" vapor-child="" parent=""></button>`,
+    )
+  })
+
+  test('vapor parent > vdom > vapor child', () => {
+    const InnerVaporChild = defineVaporComponent({
+      __scopeId: 'inner-vapor-child',
+      setup() {
+        return template('<button inner-vapor-child></button>', true)()
+      },
+    })
+
+    const VdomChild = {
+      __scopeId: 'vdom-child',
+      setup() {
+        return () => h(InnerVaporChild as any)
+      },
+    }
+
+    const VaporChild = defineVaporComponent({
+      __scopeId: 'vapor-child',
+      setup() {
+        return createComponent(VdomChild as any, null, null, true)
+      },
+    })
+
+    const App = {
+      __scopeId: 'parent',
+      setup() {
+        return () => h(VaporChild as any)
+      },
+    }
+
+    const root = document.createElement('div')
+    createApp(App).use(vaporInteropPlugin).mount(root)
+
+    expect(root.innerHTML).toBe(
+      `<button inner-vapor-child="" vdom-child="" vapor-child="" parent=""></button>`,
+    )
+  })
+})
diff --git a/packages/runtime-vapor/src/block.ts b/packages/runtime-vapor/src/block.ts
index d6be89efc..31b71848d 100644
--- a/packages/runtime-vapor/src/block.ts
+++ b/packages/runtime-vapor/src/block.ts
@@ -1,6 +1,7 @@
 import { isArray } from '@vue/shared'
 import {
   type VaporComponentInstance,
+  currentInstance,
   isVaporComponent,
   mountComponent,
   unmountComponent,
@@ -14,6 +15,7 @@ import {
   locateHydrationNode,
   locateVaporFragmentAnchor,
 } from './dom/hydration'
+import { queuePostFlushCb } from '@vue/runtime-dom'
 
 export type Block =
   | Node
@@ -213,3 +215,57 @@ export function normalizeBlock(block: Block): Node[] {
   }
   return nodes
 }
+
+export function setScopeId(block: Block, scopeId?: string): void {
+  if (block instanceof Node) {
+    if (scopeId && block instanceof Element) {
+      block.setAttribute(scopeId, '')
+    }
+  } else if (isVaporComponent(block)) {
+    setComponentScopeId(block, scopeId, true)
+  } else if (isArray(block)) {
+    for (const b of block) {
+      setScopeId(b, scopeId)
+    }
+  } else {
+    setScopeId(block.nodes, scopeId)
+  }
+}
+
+export function setComponentScopeId(
+  instance: VaporComponentInstance,
+  scopeId: string | undefined = currentInstance
+    ? currentInstance.type.__scopeId
+    : undefined,
+  immediate: boolean = false,
+): void {
+  function doSet() {
+    if (scopeId) {
+      setScopeId(instance.block, scopeId)
+    }
+    // inherit scopeId from parent component. this requires initial rendering
+    // to be finished, due to `parent.block` is null during initial rendering
+    const parent = instance.parent
+    if (parent && parent.type.__scopeId) {
+      // vapor parent
+      if (
+        parent.vapor &&
+        (parent as VaporComponentInstance).block === instance
+      ) {
+        setScopeId(instance.block, parent.type.__scopeId)
+      }
+      // vdom parent
+      else if (
+        parent.subTree &&
+        (parent.subTree.component as any) === instance
+      ) {
+        setScopeId(instance.block, parent.vnode!.scopeId!)
+      }
+    }
+  }
+  if (immediate) {
+    doSet()
+  } else {
+    queuePostFlushCb(doSet)
+  }
+}
diff --git a/packages/runtime-vapor/src/component.ts b/packages/runtime-vapor/src/component.ts
index e0396aa2e..46322ac0e 100644
--- a/packages/runtime-vapor/src/component.ts
+++ b/packages/runtime-vapor/src/component.ts
@@ -25,7 +25,14 @@ import {
   unregisterHMR,
   warn,
 } from '@vue/runtime-dom'
-import { type Block, insert, isBlock, remove } from './block'
+import {
+  type Block,
+  insert,
+  isBlock,
+  remove,
+  setComponentScopeId,
+  setScopeId,
+} from './block'
 import {
   type ShallowRef,
   markRaw,
@@ -482,6 +489,7 @@ export function createComponentWithFallback(
   // mark single root
   ;(el as any).$root = isSingleRoot
 
+  setScopeId(el, currentInstance ? currentInstance.type.__scopeId : undefined)
   if (rawProps) {
     renderEffect(() => {
       setDynamicProps(el, [resolveDynamicProps(rawProps as RawProps)])
@@ -509,6 +517,7 @@ export function mountComponent(
   }
   if (instance.bm) invokeArrayFns(instance.bm)
   insert(instance.block, parent, anchor)
+  setComponentScopeId(instance)
   if (instance.m) queuePostFlushCb(() => invokeArrayFns(instance.m!))
   instance.isMounted = true
   if (__DEV__) {
diff --git a/packages/runtime-vapor/src/vdomInterop.ts b/packages/runtime-vapor/src/vdomInterop.ts
index 33f6d4ca8..ee8799039 100644
--- a/packages/runtime-vapor/src/vdomInterop.ts
+++ b/packages/runtime-vapor/src/vdomInterop.ts
@@ -77,6 +77,7 @@ const vaporInteropImpl: Omit<
     instance.rawPropsRef = propsRef
     instance.rawSlotsRef = slotsRef
     mountComponent(instance, container, selfAnchor)
+    vnode.el = instance.block
     simpleSetCurrentInstance(prev)
     return instance
   },
@@ -203,6 +204,8 @@ function createVDOMComponent(
     internals.umt(vnode.component!, null, !!parentNode)
   }
 
+  vnode.scopeId = parentInstance.type.__scopeId!
+
   frag.insert = (parentNode, anchor) => {
     if (!isMounted || isHydrating) {
       if (isHydrating) {
@@ -240,6 +243,9 @@ function createVDOMComponent(
         parentInstance as any,
       )
     }
+
+    // update the fragment nodes
+    frag.nodes = vnode.el as Block
   }
 
   frag.remove = unmount