diff --git a/packages/vitest/src/node/pool.ts b/packages/vitest/src/node/pool.ts
index 17597ed3192d..d05bfdfebb20 100644
--- a/packages/vitest/src/node/pool.ts
+++ b/packages/vitest/src/node/pool.ts
@@ -151,8 +151,8 @@ export function createPool(ctx: Vitest): ProcessPool {
             invalidates,
             providedContext: project.getProvidedContext(),
             workerId: workerId++,
+            environment,
           },
-          environment,
           project,
           env,
           execArgv,
diff --git a/packages/vitest/src/node/pools/pool.ts b/packages/vitest/src/node/pools/pool.ts
index e0c357c7915b..7c13499176e4 100644
--- a/packages/vitest/src/node/pools/pool.ts
+++ b/packages/vitest/src/node/pools/pool.ts
@@ -1,3 +1,4 @@
+import type { ContextTestEnvironment } from '../../types/worker'
 import type { Logger } from '../logger'
 import type { StateManager } from '../state'
 import type { PoolOptions, PoolTask, WorkerResponse } from './types'
@@ -213,7 +214,9 @@ export class Pool {
       const index = this.sharedRunners.findIndex(runner => isEqualRunner(runner, task))
 
       if (index !== -1) {
-        return this.sharedRunners.splice(index, 1)[0]
+        const runner = this.sharedRunners.splice(index, 1)[0]
+        runner.reconfigure(task)
+        return runner
       }
     }
 
@@ -221,7 +224,7 @@ export class Pool {
       distPath: this.options.distPath,
       project: task.project,
       method,
-      environment: task.environment,
+      environment: task.context.environment,
       env: task.env,
       execArgv: task.execArgv,
     }
@@ -289,11 +292,47 @@ function isEqualRunner(runner: PoolRunner, task: PoolTask) {
   if (task.isolate) {
     throw new Error('Isolated tasks should not share runners')
   }
+  if (runner.worker.name !== task.worker || runner.project !== task.project) {
+    return false
+  }
+  // by default, check that the environments are the same
+  // some workers (like vmThreads/vmForks) do not need this check
+  if (!runner.worker.canReuse) {
+    return isEnvironmentEqual(task.context.environment, runner.environment)
+  }
+  return runner.worker.canReuse(task)
+}
+
+function isEnvironmentEqual(env1: ContextTestEnvironment, env2: ContextTestEnvironment): boolean {
+  if (env1.name !== env2.name) {
+    return false
+  }
+  return deepEqual(env1.options, env2.options)
+}
+
+function deepEqual(obj1: any, obj2: any): boolean {
+  if (obj1 === obj2) {
+    return true
+  }
+  if (obj1 == null || obj2 == null) {
+    return obj1 === obj2
+  }
+  if (typeof obj1 !== 'object' || typeof obj2 !== 'object') {
+    return false
+  }
+
+  const keys1 = Object.keys(obj1)
+  const keys2 = Object.keys(obj2)
+
+  if (keys1.length !== keys2.length) {
+    return false
+  }
+
+  for (const key of keys1) {
+    if (!keys2.includes(key) || !deepEqual(obj1[key], obj2[key])) {
+      return false
+    }
+  }
 
-  return (
-    runner.worker.name === task.worker
-    && runner.project === task.project
-    && runner.environment.name === task.environment.name
-    && (!runner.worker.canReuse || runner.worker.canReuse(task))
-  )
+  return true
 }
diff --git a/packages/vitest/src/node/pools/poolRunner.ts b/packages/vitest/src/node/pools/poolRunner.ts
index 1d78c2028419..da40c7a14468 100644
--- a/packages/vitest/src/node/pools/poolRunner.ts
+++ b/packages/vitest/src/node/pools/poolRunner.ts
@@ -5,7 +5,7 @@ import type { RunnerRPC, RuntimeRPC } from '../../types/rpc'
 import type { ContextTestEnvironment, WorkerExecuteContext } from '../../types/worker'
 import type { Traces } from '../../utils/traces'
 import type { TestProject } from '../project'
-import type { PoolOptions, PoolRunnerOTEL, PoolWorker, WorkerRequest, WorkerResponse } from './types'
+import type { PoolOptions, PoolRunnerOTEL, PoolTask, PoolWorker, WorkerRequest, WorkerResponse } from './types'
 import { EventEmitter } from 'node:events'
 import { createDefer } from '@vitest/utils/helpers'
 import { createBirpc } from 'birpc'
@@ -43,7 +43,7 @@ export class PoolRunner {
   public poolId: number | undefined = undefined
 
   public readonly project: TestProject
-  public readonly environment: ContextTestEnvironment
+  public environment: ContextTestEnvironment
 
   private _state: RunnerState = RunnerState.IDLE
   private _operationLock: DeferPromise<void> | null = null
@@ -113,6 +113,15 @@ export class PoolRunner {
     this._offCancel = vitest.onCancel(reason => this._rpc.onCancel(reason))
   }
 
+  /**
+   * "reconfigure" can only be called if `environment` is different, since different project always
+   * requires a new PoolRunner instance.
+   */
+  public reconfigure(task: PoolTask): void {
+    this.environment = task.context.environment
+    this._otel?.span.setAttribute('vitest.environment', this.environment.name)
+  }
+
   postMessage(message: WorkerRequest): void {
     // Only send messages when runner is active (not fully stopped)
     // Allow sending during STOPPING state for the 'stop' message itself
diff --git a/packages/vitest/src/node/pools/types.ts b/packages/vitest/src/node/pools/types.ts
index f336121ed000..9f6f6f21716c 100644
--- a/packages/vitest/src/node/pools/types.ts
+++ b/packages/vitest/src/node/pools/types.ts
@@ -34,8 +34,8 @@ export interface PoolWorker {
 
   /**
    * This is called on workers that already satisfy certain constraints:
+   * - The task has the same worker name
    * - The task has the same project
-   * - The task has the same environment
    */
   canReuse?: (task: PoolTask) => boolean
 }
@@ -55,7 +55,6 @@ export interface PoolTask {
    */
   execArgv: string[]
   context: WorkerExecuteContext
-  environment: ContextTestEnvironment
   memoryLimit: number | null
 }
 
diff --git a/packages/vitest/src/node/pools/workers/vmForksWorker.ts b/packages/vitest/src/node/pools/workers/vmForksWorker.ts
index 2cc5c8d2e870..f73f38456230 100644
--- a/packages/vitest/src/node/pools/workers/vmForksWorker.ts
+++ b/packages/vitest/src/node/pools/workers/vmForksWorker.ts
@@ -14,4 +14,8 @@ export class VmForksPoolWorker extends ForksPoolWorker {
     /** Loads {@link file://./../../../runtime/workers/vmForks.ts} */
     this.entrypoint = resolve(options.distPath, 'workers/vmForks.js')
   }
+
+  canReuse(): boolean {
+    return true
+  }
 }
diff --git a/packages/vitest/src/node/pools/workers/vmThreadsWorker.ts b/packages/vitest/src/node/pools/workers/vmThreadsWorker.ts
index 779e45b3be67..b17b25c6e096 100644
--- a/packages/vitest/src/node/pools/workers/vmThreadsWorker.ts
+++ b/packages/vitest/src/node/pools/workers/vmThreadsWorker.ts
@@ -14,4 +14,8 @@ export class VmThreadsPoolWorker extends ThreadsPoolWorker {
     /** Loads {@link file://./../../../runtime/workers/vmThreads.ts} */
     this.entrypoint = resolve(options.distPath, 'workers/vmThreads.js')
   }
+
+  canReuse(): boolean {
+    return true
+  }
 }
diff --git a/packages/vitest/src/types/worker.ts b/packages/vitest/src/types/worker.ts
index 1b84b390d01f..d96da85a49f4 100644
--- a/packages/vitest/src/types/worker.ts
+++ b/packages/vitest/src/types/worker.ts
@@ -24,6 +24,7 @@ export interface WorkerExecuteContext {
   files: FileSpecification[]
   providedContext: Record<string, any>
   invalidates?: string[]
+  environment: ContextTestEnvironment
 
   /** Exposed to test runner as `VITEST_WORKER_ID`. Value is unique per each isolated worker. */
   workerId: number