diff --git a/packages/vitest/src/index.ts b/packages/vitest/src/index.ts
index b951f9c3964b..3406920122f2 100644
--- a/packages/vitest/src/index.ts
+++ b/packages/vitest/src/index.ts
@@ -5,7 +5,7 @@ import type { Constructable, InlineConfig } from './types'
 export { suite, test, describe, it } from './runtime/suite'
 export * from './runtime/hooks'
 
-export { runOnce } from './integrations/run-once'
+export { runOnce, isFirstRun } from './integrations/run-once'
 export * from './integrations/chai'
 export * from './integrations/jest-mock'
 export * from './integrations/vi'
diff --git a/packages/vitest/src/integrations/run-once.ts b/packages/vitest/src/integrations/run-once.ts
index 379e76e6df41..52e391a47d04 100644
--- a/packages/vitest/src/integrations/run-once.ts
+++ b/packages/vitest/src/integrations/run-once.ts
@@ -1,4 +1,3 @@
-import type { Awaitable } from '../types'
 import { getWorkerState } from '../utils'
 
 const filesCount = new Map<string, number>()
@@ -12,18 +11,36 @@ const cache = new Map<string, any>()
  *
  * @experimental
  */
-export async function runOnce<T>(fn: (() => Awaitable<T>), key?: string): Promise<T> {
+export function runOnce<T>(fn: (() => T), key?: string): T {
+  const filepath = getWorkerState().filepath || '__unknown_files__'
+
   if (!key) {
-    const filepath = getWorkerState().filepath || '__unknown_files__'
     filesCount.set(filepath, (filesCount.get(filepath) || 0) + 1)
-    const count = filesCount.get(filepath)!
-    key = `${filepath}:${count}`
+    key = String(filesCount.get(filepath)!)
   }
 
-  if (!cache.has(key))
-    cache.set(key, fn())
+  const id = `${filepath}:${key}`
+
+  if (!cache.has(id))
+    cache.set(id, fn())
 
-  return await cache.get(key)
+  return cache.get(id)
+}
+
+/**
+ * Get a boolean indicates whether the task is running in the first time.
+ * Could only be `false` in watch mode.
+ *
+ * Currently only works with `isolate: false`
+ *
+ * @experimental
+ */
+export function isFirstRun() {
+  let firstRun = false
+  runOnce(() => {
+    firstRun = true
+  }, '__vitest_first_run__')
+  return firstRun
 }
 
 /**
diff --git a/test/run-once/test/run-once.test.ts b/test/run-once/test/run-once.test.ts
index 5f80bc7cab20..55319c775992 100644
--- a/test/run-once/test/run-once.test.ts
+++ b/test/run-once/test/run-once.test.ts
@@ -1,8 +1,8 @@
-import { expect, it, runOnce } from 'vitest'
+import { expect, isFirstRun, it, runOnce } from 'vitest'
 
 let dummy = 0
 
-const one = await runOnce(() => {
+const one = runOnce(() => {
   dummy += 1
   return 1
 })
@@ -12,10 +12,15 @@ const two = await runOnce(async() => {
   return 2
 })
 
-it('run once', async() => {
+it('runOnce', async() => {
   expect(one).toBe(1)
   expect(two).toBe(2)
 
   // edit the file to trigger the hmr and dummy should be 0
   expect(dummy).toBe(2)
 })
+
+it('isFirstRun', () => {
+  // edit the file and this will fail
+  expect(isFirstRun()).toBe(true)
+})