diff --git a/.github/workflows/main.yml b/.github/workflows/main.yml
index fade885..1881dea 100644
--- a/.github/workflows/main.yml
+++ b/.github/workflows/main.yml
@@ -22,13 +22,15 @@ jobs:
       CI_JOB_NUMBER: 2
     steps:
       - uses: actions/checkout@v1
+        with:
+          fetch-depth: 0
       - name: Use Node.js from .nvmrc
         uses: actions/setup-node@v6
         with:
           node-version-file: '.nvmrc'
       - run: corepack enable
       - run: yarn install
-      - run: yarn workspace @hawk.so/javascript test
+      - run: yarn test:modified origin/${{ github.event.pull_request.base.ref }}
 
   build:
     runs-on: ubuntu-latest
diff --git a/package.json b/package.json
index 01c1ec1..d59466e 100644
--- a/package.json
+++ b/package.json
@@ -14,6 +14,8 @@
     "dev": "yarn workspace @hawk.so/javascript dev",
     "build:all": "yarn workspaces foreach -Apt run build",
     "build:modified": "yarn workspaces foreach --since=\"$@\" -Rpt run build",
+    "test:all": "yarn workspaces foreach -Apt run test",
+    "test:modified": "yarn workspaces foreach --since=\"$@\" -Rpt run test",
     "stats": "yarn workspace @hawk.so/javascript stats",
     "lint": "eslint -c ./.eslintrc.cjs packages/*/src --ext .ts,.js --fix",
     "lint-test": "eslint -c ./.eslintrc.cjs packages/*/src --ext .ts,.js"
diff --git a/packages/core/package.json b/packages/core/package.json
index e06be1d..6797c92 100644
--- a/packages/core/package.json
+++ b/packages/core/package.json
@@ -17,7 +17,10 @@
     }
   },
   "scripts": {
-    "build": "vite build"
+    "build": "vite build",
+    "test": "vitest run",
+    "test:coverage": "vitest run --coverage",
+    "lint": "eslint --fix \"src/**/*.{js,ts}\""
   },
   "repository": {
     "type": "git",
@@ -33,8 +36,13 @@
     "url": "https://github.com/codex-team/hawk.javascript/issues"
   },
   "homepage": "https://github.com/codex-team/hawk.javascript#readme",
+  "dependencies": {
+    "@hawk.so/types": "0.5.8"
+  },
   "devDependencies": {
+    "@vitest/coverage-v8": "^4.0.18",
     "vite": "^7.3.1",
-    "vite-plugin-dts": "^4.2.4"
+    "vite-plugin-dts": "^4.2.4",
+    "vitest": "^4.0.18"
   }
 }
diff --git a/packages/core/src/index.ts b/packages/core/src/index.ts
index 6a701eb..1a05cf1 100644
--- a/packages/core/src/index.ts
+++ b/packages/core/src/index.ts
@@ -1 +1,2 @@
 export type { HawkStorage } from './storages/hawk-storage';
+export { HawkUserManager } from './users/hawk-user-manager';
diff --git a/packages/core/src/users/hawk-user-manager.ts b/packages/core/src/users/hawk-user-manager.ts
new file mode 100644
index 0000000..7c965c3
--- /dev/null
+++ b/packages/core/src/users/hawk-user-manager.ts
@@ -0,0 +1,71 @@
+import type { AffectedUser } from '@hawk.so/types';
+import type { HawkStorage } from '../storages/hawk-storage';
+
+/**
+ * Storage key used to persist the auto-generated user ID.
+ */
+export const HAWK_USER_ID_KEY = 'hawk-user-id';
+
+/**
+ * Manages the affected user identity.
+ *
+ * Manually provided users are kept in memory only (they don't change restarts).
+ * {@link HawkStorage} is used solely to persist the auto-generated ID
+ * so it survives across sessions.
+ */
+export class HawkUserManager {
+  /**
+   * In-memory user set explicitly via {@link setUser}.
+   */
+  private user: AffectedUser | null = null;
+
+  /**
+   * Underlying storage used to persist auto-generated user ID.
+   */
+  private readonly storage: HawkStorage;
+
+  /**
+   * @param storage - Storage backend to use for persistence.
+   */
+  constructor(storage: HawkStorage) {
+    this.storage = storage;
+  }
+
+  /**
+   * Returns the current affected user, or `null` if none is available.
+   *
+   * Priority: in-memory user > persisted user ID.
+   */
+  public getUser(): AffectedUser | null {
+    if (this.user) {
+      return this.user;
+    }
+    const storedId = this.storage.getItem(HAWK_USER_ID_KEY);
+    return storedId ? { id: storedId } : null;
+  }
+
+  /**
+   * Sets the user explicitly (in memory only).
+   *
+   * @param user - The affected user provided by the application.
+   */
+  public setUser(user: AffectedUser): void {
+    this.user = user;
+  }
+
+  /**
+   * Persists an auto-generated user ID to storage.
+   *
+   * @param id - The generated ID to persist.
+   */
+  public persistGeneratedId(id: string): void {
+    this.storage.setItem(HAWK_USER_ID_KEY, id);
+  }
+
+  /**
+   * Clears the explicitly set user, falling back to the persisted user ID.
+   */
+  public clear(): void {
+    this.user = null;
+  }
+}
diff --git a/packages/core/tests/users/hawk-user-manager.test.ts b/packages/core/tests/users/hawk-user-manager.test.ts
new file mode 100644
index 0000000..3ef9a72
--- /dev/null
+++ b/packages/core/tests/users/hawk-user-manager.test.ts
@@ -0,0 +1,72 @@
+import { describe, it, expect, beforeEach, vi } from 'vitest';
+import { HawkUserManager } from '../../src';
+import type { HawkStorage } from '../../src';
+
+describe('HawkUserManager', () => {
+  let storage: HawkStorage;
+  let manager: HawkUserManager;
+
+  beforeEach(() => {
+    storage = {
+      getItem: vi.fn().mockReturnValue(null),
+      setItem: vi.fn(),
+      removeItem: vi.fn(),
+    };
+    manager = new HawkUserManager(storage);
+  });
+
+  it('should return null when no user is set and storage is empty', () => {
+    expect(manager.getUser()).toBeNull();
+  });
+
+  it('should return in-memory user set via setUser()', () => {
+    const user = { id: 'user-1', name: 'Ryan Gosling', url: 'https://example.com', photo: 'https://example.com/photo.png' };
+
+    manager.setUser(user);
+
+    expect(manager.getUser()).toEqual(user);
+    expect(storage.setItem).not.toHaveBeenCalled();
+  });
+
+  it('should not touch storage when setUser() is called', () => {
+    manager.setUser({ id: 'user-1' });
+
+    expect(storage.setItem).not.toHaveBeenCalled();
+    expect(storage.removeItem).not.toHaveBeenCalled();
+  });
+
+  it('should return anonymous user from storage when no in-memory user is set', () => {
+    vi.mocked(storage.getItem).mockReturnValue('anon-123');
+
+    expect(manager.getUser()).toEqual({ id: 'anon-123' });
+    expect(storage.getItem).toHaveBeenCalledWith('hawk-user-id');
+  });
+
+  it('should prefer in-memory user over persisted anonymous ID', () => {
+    vi.mocked(storage.getItem).mockReturnValue('anon-123');
+    manager.setUser({ id: 'explicit-user' });
+
+    expect(manager.getUser()).toEqual({ id: 'explicit-user' });
+  });
+
+  it('should persist anonymous ID via persistGeneratedId()', () => {
+    manager.persistGeneratedId('anon-456');
+
+    expect(storage.setItem).toHaveBeenCalledWith('hawk-user-id', 'anon-456');
+  });
+
+  it('should clear in-memory user and fall back to persisted anonymous ID', () => {
+    vi.mocked(storage.getItem).mockReturnValue('anon-123');
+    manager.setUser({ id: 'user-1' });
+    manager.clear();
+
+    expect(manager.getUser()).toEqual({ id: 'anon-123' });
+  });
+
+  it('should return null after clear() when no anonymous ID is persisted', () => {
+    manager.setUser({ id: 'user-1' });
+    manager.clear();
+
+    expect(manager.getUser()).toBeNull();
+  });
+});
diff --git a/packages/core/tsconfig.test.json b/packages/core/tsconfig.test.json
new file mode 100644
index 0000000..38db19a
--- /dev/null
+++ b/packages/core/tsconfig.test.json
@@ -0,0 +1,13 @@
+{
+  "extends": "./tsconfig.json",
+  "compilerOptions": {
+    "outDir": null,
+    "declaration": false,
+    "types": ["vitest/globals"]
+  },
+  "include": [
+    "src/**/*",
+    "tests/**/*",
+    "vitest.config.ts"
+  ]
+}
diff --git a/packages/core/vitest.config.ts b/packages/core/vitest.config.ts
new file mode 100644
index 0000000..aee2668
--- /dev/null
+++ b/packages/core/vitest.config.ts
@@ -0,0 +1,15 @@
+import { defineConfig } from 'vitest/config';
+
+export default defineConfig({
+  test: {
+    globals: true,
+    include: ['tests/**/*.test.ts'],
+    typecheck: {
+      tsconfig: './tsconfig.test.json',
+    },
+    coverage: {
+      provider: 'v8',
+      include: ['src/**/*.ts'],
+    },
+  },
+});
diff --git a/packages/javascript/src/catcher.ts b/packages/javascript/src/catcher.ts
index b18d868..63bcb29 100644
--- a/packages/javascript/src/catcher.ts
+++ b/packages/javascript/src/catcher.ts
@@ -4,7 +4,6 @@ import log from './utils/log';
 import StackParser from './modules/stackParser';
 import type { CatcherMessage, HawkInitialSettings, BreadcrumbsAPI, Transport } from './types';
 import { VueIntegration } from './integrations/vue';
-import { id } from './utils/id';
 import type {
   AffectedUser,
   EventContext,
@@ -19,6 +18,9 @@ import { isErrorProcessed, markErrorAsProcessed } from './utils/event';
 import { ConsoleCatcher } from './addons/consoleCatcher';
 import { BreadcrumbManager } from './addons/breadcrumbs';
 import { validateUser, validateContext, isValidEventPayload } from './utils/validation';
+import { HawkUserManager } from '@hawk.so/core';
+import { HawkLocalStorage } from './storages/hawk-local-storage';
+import { id } from './utils/id';
 
 /**
  * Allow to use global VERSION, that will be overwritten by Webpack
@@ -62,11 +64,6 @@ export default class Catcher {
    */
   private readonly release: string | undefined;
 
-  /**
-   * Current authenticated user
-   */
-  private user: AffectedUser;
-
   /**
    * Any additional data passed by user for sending with all messages
    */
@@ -111,6 +108,11 @@ export default class Catcher {
    */
   private readonly breadcrumbManager: BreadcrumbManager | null;
 
+  /**
+   * Current authenticated user manager instance
+   */
+  private readonly userManager: HawkUserManager = new HawkUserManager(new HawkLocalStorage());
+
   /**
    * Catcher constructor
    *
@@ -126,7 +128,9 @@ export default class Catcher {
     this.token = settings.token;
     this.debug = settings.debug || false;
     this.release = settings.release !== undefined ? String(settings.release) : undefined;
-    this.setUser(settings.user || Catcher.getGeneratedUser());
+    if (settings.user) {
+      this.setUser(settings.user);
+    }
     this.setContext(settings.context || undefined);
     this.beforeSend = settings.beforeSend;
     this.disableVueErrorHandler =
@@ -189,27 +193,6 @@ export default class Catcher {
     }
   }
 
-  /**
-   * Generates user if no one provided via HawkCatcher settings
-   * After generating, stores user for feature requests
-   */
-  private static getGeneratedUser(): AffectedUser {
-    let userId: string;
-    const LOCAL_STORAGE_KEY = 'hawk-user-id';
-    const storedId = localStorage.getItem(LOCAL_STORAGE_KEY);
-
-    if (storedId) {
-      userId = storedId;
-    } else {
-      userId = id();
-      localStorage.setItem(LOCAL_STORAGE_KEY, userId);
-    }
-
-    return {
-      id: userId,
-    };
-  }
-
   /**
    * Send test event from client
    */
@@ -272,14 +255,14 @@ export default class Catcher {
       return;
     }
 
-    this.user = user;
+    this.userManager.setUser(user);
   }
 
   /**
-   * Clear current user information (revert to generated user)
+   * Clear current user information
    */
   public clearUser(): void {
-    this.user = Catcher.getGeneratedUser();
+    this.userManager.clear();
   }
 
   /**
@@ -565,10 +548,16 @@ export default class Catcher {
   }
 
   /**
-   * Current authenticated user
+   * Returns the current user if set, otherwise generates and persists an anonymous ID.
    */
-  private getUser(): HawkJavaScriptEvent['user'] {
-    return this.user || null;
+  private getUser(): AffectedUser {
+    const user = this.userManager.getUser();
+    if (user) {
+      return user;
+    }
+    const generatedId = id();
+    this.userManager.persistGeneratedId(generatedId);
+    return { id: generatedId };
   }
 
   /**
diff --git a/packages/javascript/vite.config.ts b/packages/javascript/vite.config.ts
index 47fe52e..65b622e 100644
--- a/packages/javascript/vite.config.ts
+++ b/packages/javascript/vite.config.ts
@@ -26,6 +26,7 @@ export default defineConfig(() => {
         fileName: 'hawk',
       },
       rollupOptions: {
+        external: ['@hawk.so/core'],
         plugins: [
           license({
             thirdParty: {
diff --git a/packages/javascript/vitest.config.ts b/packages/javascript/vitest.config.ts
index 47ad6a2..68e2cda 100644
--- a/packages/javascript/vitest.config.ts
+++ b/packages/javascript/vitest.config.ts
@@ -14,5 +14,6 @@ export default defineConfig({
     alias: {
       '@/types': path.resolve(__dirname, './src/types'),
     },
+    conditions: ['source'],
   },
 });
diff --git a/yarn.lock b/yarn.lock
index a2aacdf..65b88ef 100644
--- a/yarn.lock
+++ b/yarn.lock
@@ -587,8 +587,11 @@ __metadata:
   version: 0.0.0-use.local
   resolution: "@hawk.so/core@workspace:packages/core"
   dependencies:
+    "@hawk.so/types": "npm:0.5.8"
+    "@vitest/coverage-v8": "npm:^4.0.18"
     vite: "npm:^7.3.1"
     vite-plugin-dts: "npm:^4.2.4"
+    vitest: "npm:^4.0.18"
   languageName: unknown
   linkType: soft