diff --git a/packages/playwright-test/src/dispatcher.ts b/packages/playwright-test/src/dispatcher.ts
index ba00822d68..0971be701b 100644
--- a/packages/playwright-test/src/dispatcher.ts
+++ b/packages/playwright-test/src/dispatcher.ts
@@ -17,7 +17,7 @@
 import child_process from 'child_process';
 import path from 'path';
 import { EventEmitter } from 'events';
-import type { RunPayload, TestBeginPayload, TestEndPayload, DonePayload, TestOutputPayload, WorkerInitParams, StepBeginPayload, StepEndPayload, SerializedLoaderData, TeardownErrorsPayload, TestServerTestResolvedPayload } from './ipc';
+import type { RunPayload, TestBeginPayload, TestEndPayload, DonePayload, TestOutputPayload, WorkerInitParams, StepBeginPayload, StepEndPayload, SerializedLoaderData, TeardownErrorsPayload, TestServerTestResolvedPayload, WorkerIsolation } from './ipc';
 import type { TestResult, Reporter, TestStep, TestError } from '../types/testReporter';
 import type { Suite } from './test';
 import type { Loader } from './loader';
@@ -428,7 +428,7 @@ export class Dispatcher {
   }
 
   _createWorker(hash: string, parallelIndex: number) {
-    const worker = new Worker(hash, parallelIndex);
+    const worker = new Worker(hash, parallelIndex, this._loader.fullConfig()._workerIsolation);
     const handleOutput = (params: TestOutputPayload) => {
       const chunk = chunkFromParams(params);
       if (worker.didFail()) {
@@ -496,12 +496,14 @@ class Worker extends EventEmitter {
   private _didFail = false;
   private didExit = false;
   private _ready: Promise<void>;
+  workerIsolation: WorkerIsolation;
 
-  constructor(hash: string, parallelIndex: number) {
+  constructor(hash: string, parallelIndex: number, workerIsolation: WorkerIsolation) {
     super();
     this.workerIndex = lastWorkerIndex++;
     this._hash = hash;
     this.parallelIndex = parallelIndex;
+    this.workerIsolation = workerIsolation;
 
     this.process = child_process.fork(path.join(__dirname, 'worker.js'), {
       detached: false,
@@ -534,6 +536,7 @@ class Worker extends EventEmitter {
   async init(testGroup: TestGroup, loaderData: SerializedLoaderData) {
     await this._ready;
     const params: WorkerInitParams = {
+      workerIsolation: this.workerIsolation,
       workerIndex: this.workerIndex,
       parallelIndex: this.parallelIndex,
       repeatEachIndex: testGroup.repeatEachIndex,
diff --git a/packages/playwright-test/src/ipc.ts b/packages/playwright-test/src/ipc.ts
index 152611eb98..65677a2525 100644
--- a/packages/playwright-test/src/ipc.ts
+++ b/packages/playwright-test/src/ipc.ts
@@ -30,7 +30,13 @@ export type TtyParams = {
   colorDepth: number;
 };
 
+export type WorkerIsolation =
+  'isolate-projects' |  // create new worker for new project type
+  'isolate-pools';      // create new worker for new worker fixture pool digest
+
+
 export type WorkerInitParams = {
+  workerIsolation: WorkerIsolation;
   workerIndex: number;
   parallelIndex: number;
   repeatEachIndex: number;
diff --git a/packages/playwright-test/src/loader.ts b/packages/playwright-test/src/loader.ts
index 368f9daa43..f0476361ee 100644
--- a/packages/playwright-test/src/loader.ts
+++ b/packages/playwright-test/src/loader.ts
@@ -19,7 +19,7 @@ import type { Config, Project, ReporterDescription, FullProjectInternal, FullCon
 import { getPackageJsonPath, mergeObjects, errorWithFile } from './util';
 import { setCurrentlyLoadingFileSuite } from './globals';
 import { Suite, type TestCase } from './test';
-import type { SerializedLoaderData } from './ipc';
+import type { SerializedLoaderData, WorkerIsolation } from './ipc';
 import * as path from 'path';
 import * as url from 'url';
 import * as fs from 'fs';
@@ -228,7 +228,7 @@ export class Loader {
     if (!this._projectSuiteBuilders.has(project))
       this._projectSuiteBuilders.set(project, new ProjectSuiteBuilder(project));
     const builder = this._projectSuiteBuilders.get(project)!;
-    return builder.cloneFileSuite(suite, repeatEachIndex, filter);
+    return builder.cloneFileSuite(suite, 'isolate-pools', repeatEachIndex, filter);
   }
 
   serialize(): SerializedLoaderData {
@@ -371,14 +371,14 @@ class ProjectSuiteBuilder {
     return this._testPools.get(test)!;
   }
 
-  private _cloneEntries(from: Suite, to: Suite, repeatEachIndex: number, filter: (test: TestCase) => boolean): boolean {
+  private _cloneEntries(from: Suite, to: Suite, workerIsolation: WorkerIsolation, repeatEachIndex: number, filter: (test: TestCase) => boolean): boolean {
     for (const entry of from._entries) {
       if (entry instanceof Suite) {
         const suite = entry._clone();
         suite._fileId = to._fileId;
         to._addSuite(suite);
         // Ignore empty titles, similar to Suite.titlePath().
-        if (!this._cloneEntries(entry, suite, repeatEachIndex, filter)) {
+        if (!this._cloneEntries(entry, suite, workerIsolation, repeatEachIndex, filter)) {
           to._entries.pop();
           to.suites.pop();
         }
@@ -398,7 +398,10 @@ class ProjectSuiteBuilder {
           to.tests.pop();
         } else {
           const pool = this._buildPool(entry);
-          test._workerHash = `run${this._project._id}-${pool.digest}-repeat${repeatEachIndex}`;
+          if (this._project._fullConfig._workerIsolation === 'isolate-pools')
+            test._workerHash = `run${this._project._id}-${pool.digest}-repeat${repeatEachIndex}`;
+          else
+            test._workerHash = `run${this._project._id}-repeat${repeatEachIndex}`;
           test._pool = pool;
         }
       }
@@ -408,11 +411,11 @@ class ProjectSuiteBuilder {
     return true;
   }
 
-  cloneFileSuite(suite: Suite, repeatEachIndex: number, filter: (test: TestCase) => boolean): Suite | undefined {
+  cloneFileSuite(suite: Suite, workerIsolation: WorkerIsolation, repeatEachIndex: number, filter: (test: TestCase) => boolean): Suite | undefined {
     const result = suite._clone();
     const relativeFile = path.relative(this._project.testDir, suite.location!.file).split(path.sep).join('/');
     result._fileId = calculateSha1(relativeFile).slice(0, 20);
-    return this._cloneEntries(suite, result, repeatEachIndex, filter) ? result : undefined;
+    return this._cloneEntries(suite, result, workerIsolation, repeatEachIndex, filter) ? result : undefined;
   }
 
   private _applyConfigUseOptions(testType: TestTypeImpl, configUse: Fixtures): FixturesWithLocation[] {
@@ -647,6 +650,7 @@ export const baseFullConfig: FullConfigInternal = {
   _globalOutputDir: path.resolve(process.cwd()),
   _configDir: '',
   _testGroupsCount: 0,
+  _workerIsolation: 'isolate-pools',
 };
 
 function resolveReporters(reporters: Config['reporter'], rootDir: string): ReporterDescription[]|undefined {
diff --git a/packages/playwright-test/src/types.ts b/packages/playwright-test/src/types.ts
index f2a6d745f7..a9addb2b80 100644
--- a/packages/playwright-test/src/types.ts
+++ b/packages/playwright-test/src/types.ts
@@ -16,6 +16,7 @@
 
 import type { Fixtures, TestError, Project } from '../types/test';
 import type { Location } from '../types/testReporter';
+import type { WorkerIsolation } from './ipc';
 import type { FullConfig as FullConfigPublic, FullProject as FullProjectPublic } from './types';
 export * from '../types/test';
 export type { Location } from '../types/testReporter';
@@ -44,6 +45,7 @@ export interface FullConfigInternal extends FullConfigPublic {
   _globalOutputDir: string;
   _configDir: string;
   _testGroupsCount: number;
+  _workerIsolation: WorkerIsolation;
   /**
    * If populated, this should also be the first/only entry in _webServers. Legacy singleton `webServer` as well as those provided via an array in the user-facing playwright.config.{ts,js} will be in `_webServers`. The legacy field (`webServer`) field additionally stores the backwards-compatible singleton `webServer` since it had been showing up in globalSetup to the user.
    */
diff --git a/packages/playwright-test/src/workerRunner.ts b/packages/playwright-test/src/workerRunner.ts
index cbb7019baf..fd3bf13486 100644
--- a/packages/playwright-test/src/workerRunner.ts
+++ b/packages/playwright-test/src/workerRunner.ts
@@ -278,7 +278,11 @@ export class WorkerRunner extends EventEmitter {
     };
 
     if (!this._isStopped) {
-      // Update the fixture pool - it may differ between tests, but only in test-scoped fixtures.
+      // Update the fixture pool - it may differ between tests.
+      // - In case of isolate-pools worker isolation, only test-scoped fixtures may differ.
+      // - In case of isolate-projects, worker fixtures can differ too, tear down worker fixture scope if they differ.
+      if (this._params.workerIsolation === 'isolate-projects' && this._fixtureRunner.pool && this._fixtureRunner.pool.digest !== test._pool!.digest)
+        await this._teardownScopes();
       this._fixtureRunner.setPool(test._pool!);
     }