diff --git a/crates/trusted-server-js/lib/test/fixtures/paths.ts b/crates/trusted-server-js/lib/test/fixtures/paths.ts
new file mode 100644
index 000000000..199b105c1
--- /dev/null
+++ b/crates/trusted-server-js/lib/test/fixtures/paths.ts
@@ -0,0 +1,17 @@
+import { resolve } from 'node:path';
+
+/**
+ * Absolute path to the edge-injected `gpt_bootstrap.js` that several suites
+ * evaluate verbatim.
+ *
+ * Resolved from `import.meta.dirname`, which Node defines as a platform-native
+ * directory path. A `file:` URL pathname is not a filesystem path, because on
+ * Windows it carries a leading slash before the drive letter, so reading it
+ * directly makes Node resolve it against the current drive and the drive
+ * segment doubles. Resolving from this module's own directory also keeps the
+ * path independent of the working directory the suite is launched from.
+ */
+export const GPT_BOOTSTRAP_PATH = resolve(
+  import.meta.dirname,
+  '../../../../trusted-server-core/src/integrations/gpt_bootstrap.js'
+);
diff --git a/crates/trusted-server-js/lib/test/integrations/gpt/ad_init.test.ts b/crates/trusted-server-js/lib/test/integrations/gpt/ad_init.test.ts
index b7186518b..51d8cabbf 100644
--- a/crates/trusted-server-js/lib/test/integrations/gpt/ad_init.test.ts
+++ b/crates/trusted-server-js/lib/test/integrations/gpt/ad_init.test.ts
@@ -1,11 +1,10 @@
 import { readFileSync } from 'node:fs';
 import { readFile } from 'node:fs/promises';
-import path from 'node:path';
-import { resolve } from 'node:path';
 
 import { describe, it, expect, vi, beforeEach, afterEach, afterAll } from 'vitest';
 
 import envelope from '../../fixtures/aps-renderer-v1.json';
+import { GPT_BOOTSTRAP_PATH } from '../../fixtures/paths';
 import type { AuctionBidData, TsjsApi } from '../../../src/core/types';
 import {
   APS_PREBID_CREATIVE_RUNNER_URL,
@@ -120,20 +119,7 @@ type TestWindow = Omit<Window, 'tsjs'> & {
 };
 
 async function runGptBootstrapWithGoogleTag(googletag: object): Promise<void> {
-  const bootstrapUrl = new URL(
-    '../../../../../trusted-server-core/src/integrations/gpt_bootstrap.js',
-    import.meta.url
-  );
-  const urlPath = decodeURIComponent(bootstrapUrl.pathname);
-  let bootstrapPath: string;
-  if (urlPath.startsWith('/@fs/')) {
-    bootstrapPath = urlPath.slice('/@fs'.length);
-  } else if (bootstrapUrl.protocol === 'file:') {
-    bootstrapPath = urlPath;
-  } else {
-    bootstrapPath = path.resolve(process.cwd(), `.${urlPath}`);
-  }
-  const bootstrap = await readFile(bootstrapPath, 'utf8');
+  const bootstrap = await readFile(GPT_BOOTSTRAP_PATH, 'utf8');
   const runBootstrap = new Function('window', 'googletag', bootstrap) as (
     window: Window,
     googletag: object
@@ -145,10 +131,7 @@ type HandoffImplementation = 'bootstrap' | 'bundle';
 
 async function installHandoff(implementation: HandoffImplementation): Promise<void> {
   if (implementation === 'bootstrap') {
-    const bootstrap = readFileSync(
-      resolve(process.cwd(), '../../trusted-server-core/src/integrations/gpt_bootstrap.js'),
-      'utf8'
-    );
+    const bootstrap = readFileSync(GPT_BOOTSTRAP_PATH, 'utf8');
     window.eval(bootstrap);
     return;
   }
@@ -201,10 +184,7 @@ function appendResponsiveSlotElement(
 }
 
 function runGptBootstrap(): void {
-  const bootstrap = readFileSync(
-    resolve(process.cwd(), '../../trusted-server-core/src/integrations/gpt_bootstrap.js'),
-    'utf8'
-  );
+  const bootstrap = readFileSync(GPT_BOOTSTRAP_PATH, 'utf8');
   window.eval(bootstrap);
 }
 
@@ -1150,10 +1130,7 @@ describe('installTsAdInit', () => {
       gptSlotHandoffs: { 'div-ts-fallback': handoff },
     };
 
-    const bootstrap = readFileSync(
-      resolve(process.cwd(), '../../trusted-server-core/src/integrations/gpt_bootstrap.js'),
-      'utf8'
-    );
+    const bootstrap = readFileSync(GPT_BOOTSTRAP_PATH, 'utf8');
     window.eval(bootstrap);
 
     expect(() =>
diff --git a/crates/trusted-server-js/lib/test/integrations/gpt/gpt_bootstrap.test.ts b/crates/trusted-server-js/lib/test/integrations/gpt/gpt_bootstrap.test.ts
index ab6d646f2..e9ed4a169 100644
--- a/crates/trusted-server-js/lib/test/integrations/gpt/gpt_bootstrap.test.ts
+++ b/crates/trusted-server-js/lib/test/integrations/gpt/gpt_bootstrap.test.ts
@@ -1,9 +1,9 @@
 import { readFileSync } from 'node:fs';
-import path from 'node:path';
 
 import { describe, it, expect, vi, beforeEach, afterEach } from 'vitest';
 
 import type { TsjsApi } from '../../../src/core/types';
+import { GPT_BOOTSTRAP_PATH } from '../../fixtures/paths';
 
 /**
  * Executable coverage for the edge-injected `gpt_bootstrap.js` — the
@@ -12,15 +12,8 @@ import type { TsjsApi } from '../../../src/core/types';
  * `crates/trusted-server-core/src/integrations/gpt_bootstrap.js` and is
  * evaluated here verbatim, so the degradation path (fallback `adInit` and
  * fallback `scheduleInitialAdInit`) is executed, not string-matched.
- *
- * Vitest runs with the lib directory as cwd (the vitest.config.ts root), so
- * the bootstrap is resolved relative to it rather than via import.meta.url,
- * which the jsdom environment rewrites to a non-file scheme.
  */
-const BOOTSTRAP_SOURCE = readFileSync(
-  path.resolve(process.cwd(), '../../trusted-server-core/src/integrations/gpt_bootstrap.js'),
-  'utf8'
-);
+const BOOTSTRAP_SOURCE = readFileSync(GPT_BOOTSTRAP_PATH, 'utf8');
 
 // The command queue the bootstrap pushes into: a real array once GPT has
 // loaded, or the bare `push`-only stub GPT installs before then.
diff --git a/crates/trusted-server-js/lib/test/integrations/gpt/schedule_initial_ad_init.test.ts b/crates/trusted-server-js/lib/test/integrations/gpt/schedule_initial_ad_init.test.ts
index 727300aa1..6ca610547 100644
--- a/crates/trusted-server-js/lib/test/integrations/gpt/schedule_initial_ad_init.test.ts
+++ b/crates/trusted-server-js/lib/test/integrations/gpt/schedule_initial_ad_init.test.ts
@@ -1,9 +1,9 @@
 import { readFileSync } from 'node:fs';
-import path from 'node:path';
 
 import { describe, it, expect, vi, beforeEach, afterEach } from 'vitest';
 
 import type { TsjsApi } from '../../../src/core/types';
+import { GPT_BOOTSTRAP_PATH } from '../../fixtures/paths';
 
 type TestWindow = Window & {
   googletag?: unknown;
@@ -12,10 +12,7 @@ type TestWindow = Window & {
 
 const originalPushState = history.pushState.bind(history);
 const originalReplaceState = history.replaceState.bind(history);
-const BOOTSTRAP_SOURCE = readFileSync(
-  path.resolve(process.cwd(), '../../trusted-server-core/src/integrations/gpt_bootstrap.js'),
-  'utf8'
-);
+const BOOTSTRAP_SOURCE = readFileSync(GPT_BOOTSTRAP_PATH, 'utf8');
 
 function runBootstrap(): void {
   new Function(BOOTSTRAP_SOURCE)();
diff --git a/crates/trusted-server-js/lib/test/integrations/gpt/spa_hook.test.ts b/crates/trusted-server-js/lib/test/integrations/gpt/spa_hook.test.ts
index 314348fa8..24ed04431 100644
--- a/crates/trusted-server-js/lib/test/integrations/gpt/spa_hook.test.ts
+++ b/crates/trusted-server-js/lib/test/integrations/gpt/spa_hook.test.ts
@@ -1,9 +1,9 @@
 import { readFileSync } from 'node:fs';
-import { resolve } from 'node:path';
 
 import { describe, it, expect, vi, beforeEach, afterEach } from 'vitest';
 
 import type { TsjsApi } from '../../../src/core/types';
+import { GPT_BOOTSTRAP_PATH } from '../../fixtures/paths';
 
 type TestWindow = Window & {
   googletag?: unknown;
@@ -148,10 +148,7 @@ describe('installSpaAuctionHook', () => {
       };
 
       if (implementation === 'bootstrap') {
-        const bootstrap = readFileSync(
-          resolve(process.cwd(), '../../trusted-server-core/src/integrations/gpt_bootstrap.js'),
-          'utf8'
-        );
+        const bootstrap = readFileSync(GPT_BOOTSTRAP_PATH, 'utf8');
         window.eval(bootstrap);
       }
       await importGptModule();