diff --git a/packages-private/vapor-e2e-test/__tests__/transition.spec.ts b/packages-private/vapor-e2e-test/__tests__/transition.spec.ts
index 44065e6c4..d7d35f836 100644
--- a/packages-private/vapor-e2e-test/__tests__/transition.spec.ts
+++ b/packages-private/vapor-e2e-test/__tests__/transition.spec.ts
@@ -49,7 +49,11 @@ describe('vapor transition', () => {
       ([btnSel, containerSel]) => {
         ;(document.querySelector(btnSel) as HTMLElement)!.click()
         return Promise.resolve().then(() => {
-          return document.querySelector(containerSel)!.className.split(/\s+/g)
+          const container = document.querySelector(containerSel)!
+          return {
+            classNames: container.className.split(/\s+/g),
+            innerHTML: container.innerHTML,
+          }
         })
       },
       [btnSelector, containerSelector],
@@ -66,7 +70,8 @@ describe('vapor transition', () => {
 
       // leave
       expect(
-        await classWhenTransitionStart(btnSelector, containerSelector),
+        (await classWhenTransitionStart(btnSelector, containerSelector))
+          .classNames,
       ).toStrictEqual(['v-leave-from', 'v-leave-active'])
 
       await nextFrame()
@@ -80,7 +85,8 @@ describe('vapor transition', () => {
 
       // enter
       expect(
-        await classWhenTransitionStart(btnSelector, containerSelector),
+        (await classWhenTransitionStart(btnSelector, containerSelector))
+          .classNames,
       ).toStrictEqual(['v-enter-from', 'v-enter-active'])
 
       await nextFrame()
@@ -102,16 +108,14 @@ describe('vapor transition', () => {
       const containerSelector = '.vif > h1'
 
       // appear
-      expect(await classList(containerSelector)).toStrictEqual([
-        'v-enter-from',
-        'v-enter-active',
-      ])
+      expect(await classList(containerSelector)).contains('v-enter-active')
       expect(await text(containerSelector)).toContain('vIf')
       await transitionFinish()
 
       // leave
       expect(
-        await classWhenTransitionStart(btnSelector, containerSelector),
+        (await classWhenTransitionStart(btnSelector, containerSelector))
+          .classNames,
       ).toStrictEqual(['v-leave-from', 'v-leave-active'])
 
       await nextFrame()
@@ -125,7 +129,8 @@ describe('vapor transition', () => {
 
       // enter
       expect(
-        await classWhenTransitionStart(btnSelector, containerSelector),
+        (await classWhenTransitionStart(btnSelector, containerSelector))
+          .classNames,
       ).toStrictEqual(['v-enter-from', 'v-enter-active'])
 
       await nextFrame()
@@ -150,7 +155,8 @@ describe('vapor transition', () => {
 
       // change key
       expect(
-        await classWhenTransitionStart(btnSelector, containerSelector),
+        (await classWhenTransitionStart(btnSelector, containerSelector))
+          .classNames,
       ).toStrictEqual(['v-leave-from', 'v-leave-active'])
 
       await nextFrame()
@@ -164,7 +170,8 @@ describe('vapor transition', () => {
 
       // change key again
       expect(
-        await classWhenTransitionStart(btnSelector, containerSelector),
+        (await classWhenTransitionStart(btnSelector, containerSelector))
+          .classNames,
       ).toStrictEqual(['v-leave-from', 'v-leave-active'])
 
       await nextFrame()
@@ -188,10 +195,10 @@ describe('vapor transition', () => {
       expect(await html(containerSelector)).toBe(`<div>vapor compB</div>`)
 
       // compB -> compA
-      await click(btnSelector)
-      expect(await html(containerSelector)).toBe(
-        `<div class="fade-leave-from fade-leave-active">vapor compB</div>`,
-      )
+      expect(
+        (await classWhenTransitionStart(btnSelector, containerSelector))
+          .innerHTML,
+      ).toBe(`<div class="fade-leave-from fade-leave-active">vapor compB</div>`)
 
       await nextFrame()
       expect(await html(containerSelector)).toBe(
@@ -241,7 +248,51 @@ describe('vapor transition', () => {
     E2E_TIMEOUT,
   )
 
-  test.todo('should work with in-out mode', async () => {}, E2E_TIMEOUT)
+  test.todo(
+    'should work with in-out mode',
+    async () => {
+      const btnSelector = '.in-out > button'
+      const containerSelector = '.in-out > div'
+
+      expect(await html(containerSelector)).toBe(`<div>vapor compB</div>`)
+
+      // compA enter
+      const { innerHTML } = await classWhenTransitionStart(
+        btnSelector,
+        containerSelector,
+      )
+      expect(innerHTML).toBe(
+        `<div>vapor compB</div><div class="fade-enter-from fade-enter-active">vapor compA</div>`,
+      )
+
+      await nextFrame()
+      expect(await html(containerSelector)).toBe(
+        `<div>vapor compB</div><div class="fade-enter-active fade-enter-to">vapor compA</div>`,
+      )
+
+      await transitionFinish()
+      expect(await html(containerSelector)).toBe(
+        `<div>vapor compB</div><div class="">vapor compA</div>`,
+      )
+
+      // compB leave
+      expect(await html(containerSelector)).toBe(
+        `<div class="fade-leave-from fade-leave-active">vapor compB</div><div class="">vapor compA</div>`,
+      )
+
+      await nextFrame()
+      expect(await html(containerSelector)).toBe(
+        `<div class="fade-leave-active fade-leave-to">vapor compB</div><div class="">vapor compA</div>`,
+      )
+
+      await transitionFinish()
+      await nextFrame()
+      expect(await html(containerSelector)).toBe(
+        `<div class="">vapor compA</div>`,
+      )
+    },
+    E2E_TIMEOUT,
+  )
 
   test.todo('transition hooks', async () => {}, E2E_TIMEOUT)
 
diff --git a/packages-private/vapor-e2e-test/transition/App.vue b/packages-private/vapor-e2e-test/transition/App.vue
index 008506800..3166f274d 100644
--- a/packages-private/vapor-e2e-test/transition/App.vue
+++ b/packages-private/vapor-e2e-test/transition/App.vue
@@ -33,13 +33,21 @@ function toggleComponent() {
     </Transition>
   </div>
   <div class="out-in">
-    <button @click="toggleComponent">toggle component</button>
+    <button @click="toggleComponent">toggle out-in</button>
     <div>
       <Transition name="fade" mode="out-in">
         <component :is="activeComponent"></component>
       </Transition>
     </div>
   </div>
+  <div class="in-out">
+    <button @click="toggleComponent">toggle in-out</button>
+    <div>
+      <Transition name="fade" mode="in-out">
+        <component :is="activeComponent"></component>
+      </Transition>
+    </div>
+  </div>
 </template>
 <style>
 .keyed {
diff --git a/packages/compiler-vapor/src/transforms/transformElement.ts b/packages/compiler-vapor/src/transforms/transformElement.ts
index 370cfdc99..35fd596ee 100644
--- a/packages/compiler-vapor/src/transforms/transformElement.ts
+++ b/packages/compiler-vapor/src/transforms/transformElement.ts
@@ -130,9 +130,7 @@ function transformComponentElement(
   }
 
   context.dynamic.flags |= DynamicFlag.NON_TEMPLATE | DynamicFlag.INSERT
-  // context.registerOperation()
-  // TODO revert wait for https://github.com/vuejs/core/pull/12951 get merged
-  context.block.operation.unshift({
+  context.registerOperation({
     type: IRNodeTypes.CREATE_COMPONENT_NODE,
     id: context.reference(),
     tag,
diff --git a/packages/runtime-vapor/src/components/Transition.ts b/packages/runtime-vapor/src/components/Transition.ts
index 13ec46ad6..8ff58bf73 100644
--- a/packages/runtime-vapor/src/components/Transition.ts
+++ b/packages/runtime-vapor/src/components/Transition.ts
@@ -210,6 +210,7 @@ export function findTransitionBlock(block: Block): TransitionBlock | undefined {
     if (block instanceof Element) child = block
   } else if (isVaporComponent(block)) {
     child = findTransitionBlock(block.block)
+    if (child && child.key === undefined) child.key = block.type.__name
   } else if (Array.isArray(block)) {
     child = block[0] as TransitionBlock
     let hasFound = false