diff --git a/src/services/github/deviceFlow.test.ts b/src/services/github/deviceFlow.test.ts
index 2cd98e1a..775144ff 100644
--- a/src/services/github/deviceFlow.test.ts
+++ b/src/services/github/deviceFlow.test.ts
@@ -1,4 +1,4 @@
-import { afterEach, beforeEach, describe, expect, mock, test } from 'bun:test'
+import { afterEach, describe, expect, mock, test } from 'bun:test'
 
 import {
   DEFAULT_GITHUB_DEVICE_SCOPE,
@@ -12,22 +12,15 @@ async function importFreshModule() {
   return import(`./deviceFlow.ts?ts=${Date.now()}-${Math.random()}`)
 }
 
+afterEach(() => {
+  mock.restore()
+})
+
 describe('requestDeviceCode', () => {
-  const originalFetch = globalThis.fetch
-
-  beforeEach(() => {
-    mock.restore()
-    globalThis.fetch = originalFetch
-  })
-
-  afterEach(() => {
-    globalThis.fetch = originalFetch
-  })
-
   test('parses successful device code response', async () => {
     const { requestDeviceCode } = await importFreshModule()
 
-    globalThis.fetch = mock(() =>
+    const fetchImpl = mock(() =>
       Promise.resolve(
         new Response(
           JSON.stringify({
@@ -44,7 +37,7 @@ describe('requestDeviceCode', () => {
 
     const r = await requestDeviceCode({
       clientId: 'test-client',
-      fetchImpl: globalThis.fetch,
+      fetchImpl,
     })
     expect(r.device_code).toBe('abc')
     expect(r.user_code).toBe('ABCD-1234')
@@ -57,17 +50,17 @@ describe('requestDeviceCode', () => {
     const { requestDeviceCode, GitHubDeviceFlowError } =
       await importFreshModule()
 
-    globalThis.fetch = mock(() =>
+    const fetchImpl = mock(() =>
       Promise.resolve(new Response('bad', { status: 500 })),
     )
     await expect(
-      requestDeviceCode({ clientId: 'x', fetchImpl: globalThis.fetch }),
+      requestDeviceCode({ clientId: 'x', fetchImpl }),
     ).rejects.toThrow(GitHubDeviceFlowError)
   })
 
   test('uses OAuth-safe default scope', async () => {
     let capturedScope = ''
-    globalThis.fetch = mock((_url: RequestInfo | URL, init?: RequestInit) => {
+    const fetchImpl = mock((_url: RequestInfo | URL, init?: RequestInit) => {
       const body = init?.body
       if (body instanceof URLSearchParams) {
         capturedScope = body.get('scope') ?? ''
@@ -87,7 +80,7 @@ describe('requestDeviceCode', () => {
       )
     })
 
-    await requestDeviceCode({ clientId: 'test-client', fetchImpl: globalThis.fetch })
+    await requestDeviceCode({ clientId: 'test-client', fetchImpl })
     expect(capturedScope).toBe(DEFAULT_GITHUB_DEVICE_SCOPE)
     expect(capturedScope).toBe('read:user')
   })
@@ -96,7 +89,7 @@ describe('requestDeviceCode', () => {
     const scopesSeen: string[] = []
     let callCount = 0
 
-    globalThis.fetch = mock((_url: RequestInfo | URL, init?: RequestInit) => {
+    const fetchImpl = mock((_url: RequestInfo | URL, init?: RequestInit) => {
       const body = init?.body
       const scope =
         body instanceof URLSearchParams
@@ -132,7 +125,7 @@ describe('requestDeviceCode', () => {
     const result = await requestDeviceCode({
       clientId: 'test-client',
       scope: 'read:user,models:read',
-      fetchImpl: globalThis.fetch,
+      fetchImpl,
     })
 
     expect(result.device_code).toBe('abc')
@@ -142,17 +135,11 @@ describe('requestDeviceCode', () => {
 })
 
 describe('pollAccessToken', () => {
-  const originalFetch = globalThis.fetch
-
-  afterEach(() => {
-    globalThis.fetch = originalFetch
-  })
-
   test('returns token when GitHub responds with access_token immediately', async () => {
     const { pollAccessToken } = await importFreshModule()
 
     let calls = 0
-    globalThis.fetch = mock(() => {
+    const fetchImpl = mock(() => {
       calls++
       return Promise.resolve(
         new Response(JSON.stringify({ access_token: 'tok-xyz' }), {
@@ -163,7 +150,7 @@ describe('pollAccessToken', () => {
 
     const token = await pollAccessToken('dev-code', {
       clientId: 'cid',
-      fetchImpl: globalThis.fetch,
+      fetchImpl,
     })
     expect(token).toBe('tok-xyz')
     expect(calls).toBe(1)
@@ -172,7 +159,7 @@ describe('pollAccessToken', () => {
   test('throws on access_denied', async () => {
     const { pollAccessToken } = await importFreshModule()
 
-    globalThis.fetch = mock(() =>
+    const fetchImpl = mock(() =>
       Promise.resolve(
         new Response(JSON.stringify({ error: 'access_denied' }), {
           status: 200,
@@ -182,23 +169,17 @@ describe('pollAccessToken', () => {
     await expect(
       pollAccessToken('dc', {
         clientId: 'c',
-        fetchImpl: globalThis.fetch,
+        fetchImpl,
       }),
     ).rejects.toThrow(/denied/)
   })
 })
 
 describe('exchangeForCopilotToken', () => {
-  const originalFetch = globalThis.fetch
-
-  afterEach(() => {
-    globalThis.fetch = originalFetch
-  })
-
   test('parses successful Copilot token response', async () => {
     const { exchangeForCopilotToken } = await importFreshModule()
 
-    globalThis.fetch = mock(() =>
+    const fetchImpl = mock(() =>
       Promise.resolve(
         new Response(
           JSON.stringify({
@@ -214,7 +195,7 @@ describe('exchangeForCopilotToken', () => {
       ),
     )
 
-    const result = await exchangeForCopilotToken('oauth-token', globalThis.fetch)
+    const result = await exchangeForCopilotToken('oauth-token', fetchImpl)
     expect(result.token).toBe('copilot-token-xyz')
     expect(result.expires_at).toBe(1700000000)
     expect(result.refresh_in).toBe(3600)
@@ -225,24 +206,24 @@ describe('exchangeForCopilotToken', () => {
     const { exchangeForCopilotToken, GitHubDeviceFlowError } =
       await importFreshModule()
 
-    globalThis.fetch = mock(() =>
+    const fetchImpl = mock(() =>
       Promise.resolve(new Response('unauthorized', { status: 401 })),
     )
     await expect(
-      exchangeForCopilotToken('bad-token', globalThis.fetch),
+      exchangeForCopilotToken('bad-token', fetchImpl),
     ).rejects.toThrow(GitHubDeviceFlowError)
   })
 
   test('throws on malformed response', async () => {
     const { exchangeForCopilotToken } = await importFreshModule()
 
-    globalThis.fetch = mock(() =>
+    const fetchImpl = mock(() =>
       Promise.resolve(
         new Response(JSON.stringify({ invalid: 'data' }), { status: 200 }),
       ),
     )
     await expect(
-      exchangeForCopilotToken('oauth-token', globalThis.fetch),
+      exchangeForCopilotToken('oauth-token', fetchImpl),
     ).rejects.toThrow(/Malformed/)
   })
 })