diff --git a/packages/language-server/src/workspace.integration.test.ts b/packages/language-server/src/workspace.integration.test.ts
new file mode 100644
index 0000000..10b0d07
--- /dev/null
+++ b/packages/language-server/src/workspace.integration.test.ts
@@ -0,0 +1,10 @@
+import { cwd } from 'node:process'
+import { describe, expect, it } from 'vitest'
+import { URI } from 'vscode-uri'
+import { detectPackageManagerFromProject } from './workspace'
+
+describe('detectPackageManagerFromProject', () => {
+  it('detects the real repository as pnpm', async () => {
+    await expect(detectPackageManagerFromProject(URI.file(cwd()).path)).resolves.toBe('pnpm')
+  })
+})
diff --git a/packages/language-server/src/workspace.test.ts b/packages/language-server/src/workspace.test.ts
index d3bf3d0..423b9c7 100644
--- a/packages/language-server/src/workspace.test.ts
+++ b/packages/language-server/src/workspace.test.ts
@@ -1,3 +1,4 @@
+import { detect } from 'package-manager-detector/detect'
 import { afterEach, describe, expect, it, vi } from 'vitest'
 import { detectPackageManagerFromProject } from './workspace'
 
@@ -5,23 +6,11 @@ vi.mock('package-manager-detector/detect', () => ({
   detect: vi.fn(),
 }))
 
-const { detect } = await import('package-manager-detector/detect')
-
 describe('detectPackageManagerFromProject', () => {
   afterEach(() => {
     vi.mocked(detect).mockReset()
   })
 
-  it('returns supported package managers directly', async () => {
-    vi.mocked(detect).mockResolvedValue({ name: 'pnpm', agent: 'pnpm' })
-
-    await expect(detectPackageManagerFromProject('/repo')).resolves.toBe('pnpm')
-    expect(detect).toHaveBeenCalledWith({
-      cwd: '/repo',
-      stopDir: '/repo',
-    })
-  })
-
   it('falls back to npm for unsupported detectors', async () => {
     vi.mocked(detect).mockResolvedValue({ name: 'deno', agent: 'deno' })
 
diff --git a/packages/language-server/src/workspace.ts b/packages/language-server/src/workspace.ts
index 204209b..9ab4ae0 100644
--- a/packages/language-server/src/workspace.ts
+++ b/packages/language-server/src/workspace.ts
@@ -15,9 +15,12 @@ import { URI } from 'vscode-uri'
  * @internal
  */
 export async function detectPackageManagerFromProject(rootPath: string): Promise<PackageManager> {
+  // `rootPath` is a URI path (posix-style) coming from `WorkspaceContext`,
+  // but `detect()` reads the filesystem and requires a platform-native path.
+  const fsPath = URI.file(rootPath).fsPath
   const result = await detect({
-    cwd: rootPath,
-    stopDir: rootPath,
+    cwd: fsPath,
+    stopDir: fsPath,
   })
 
   switch (result?.name) {