diff --git a/.changeset/calm-apes-double.md b/.changeset/calm-apes-double.md
new file mode 100644
index 000000000..620f39ce4
--- /dev/null
+++ b/.changeset/calm-apes-double.md
@@ -0,0 +1,5 @@
+---
+'@vercel/fs-detectors': major
+---
+
+`LocalFileSystemDetector#readdir()` now returns paths relative to the root dir, instead of absolute paths. This is to align with the usage of the detectors that are using the `DetectorFilesystem` interface.
diff --git a/packages/fs-detectors/package.json b/packages/fs-detectors/package.json
index ddb8eaf2f..55f4e8e86 100644
--- a/packages/fs-detectors/package.json
+++ b/packages/fs-detectors/package.json
@@ -15,8 +15,8 @@
   "license": "Apache-2.0",
   "scripts": {
     "build": "tsc",
-    "test": "jest --env node --verbose --runInBand --bail test/unit.*test.*",
-    "test-unit": "pnpm test"
+    "test": "jest --env node --verbose --runInBand --bail",
+    "test-unit": "pnpm test test/unit.*test.*"
   },
   "dependencies": {
     "@vercel/error-utils": "1.0.10",
diff --git a/packages/fs-detectors/src/detectors/local-file-system-detector.ts b/packages/fs-detectors/src/detectors/local-file-system-detector.ts
index a9502e25e..272bf448b 100644
--- a/packages/fs-detectors/src/detectors/local-file-system-detector.ts
+++ b/packages/fs-detectors/src/detectors/local-file-system-detector.ts
@@ -6,10 +6,12 @@ import { isErrnoException } from '@vercel/error-utils';
 
 export class LocalFileSystemDetector extends DetectorFilesystem {
   private rootPath: string;
+
   constructor(rootPath: string) {
     super();
     this.rootPath = rootPath;
   }
+
   async _hasPath(name: string): Promise<boolean> {
     try {
       await fs.stat(this.getFilePath(name));
@@ -21,13 +23,16 @@ export class LocalFileSystemDetector extends DetectorFilesystem {
       throw err;
     }
   }
+
   _readFile(name: string): Promise<Buffer> {
     return fs.readFile(this.getFilePath(name));
   }
+
   async _isFile(name: string): Promise<boolean> {
     const stat = await fs.stat(this.getFilePath(name));
     return stat.isFile();
   }
+
   async _readdir(name: string): Promise<DetectorFilesystemStat[]> {
     const dirPath = this.getFilePath(name);
     const dir = await fs.readdir(dirPath, {
@@ -44,14 +49,22 @@ export class LocalFileSystemDetector extends DetectorFilesystem {
     };
     return dir.map(dirent => ({
       name: dirent.name,
-      path: path.join(dirPath, dirent.name),
+      path: path.join(this.getRelativeFilePath(name), dirent.name),
       type: getType(dirent),
     }));
   }
+
   _chdir(name: string): DetectorFilesystem {
     return new LocalFileSystemDetector(this.getFilePath(name));
   }
+
+  private getRelativeFilePath(name: string) {
+    return name.startsWith(this.rootPath)
+      ? path.relative(this.rootPath, name)
+      : name;
+  }
+
   private getFilePath(name: string) {
-    return path.join(this.rootPath, name);
+    return path.join(this.rootPath, this.getRelativeFilePath(name));
   }
 }
diff --git a/packages/fs-detectors/test/unit.detect-monorepo-managers.test.ts b/packages/fs-detectors/test/unit.detect-monorepo-managers.test.ts
index baf81e5f7..c3834f1dc 100644
--- a/packages/fs-detectors/test/unit.detect-monorepo-managers.test.ts
+++ b/packages/fs-detectors/test/unit.detect-monorepo-managers.test.ts
@@ -1,7 +1,7 @@
 import path from 'path';
+import { LocalFileSystemDetector } from '../src';
 import { detectFramework } from '../src/detect-framework';
 import monorepoManagers from '../src/monorepos/monorepo-managers';
-import { FixtureFilesystem } from './utils/fixture-filesystem';
 
 describe('monorepo-managers', () => {
   describe.each([
@@ -17,7 +17,7 @@ describe('monorepo-managers', () => {
 
     it(testName, async () => {
       const fixture = path.join(__dirname, 'fixtures', fixturePath);
-      const fs = new FixtureFilesystem(fixture);
+      const fs = new LocalFileSystemDetector(fixture);
 
       const result = await detectFramework({
         fs,
diff --git a/packages/fs-detectors/test/unit.detect-package-managers.test.ts b/packages/fs-detectors/test/unit.detect-package-managers.test.ts
index 404e01774..100158f6b 100644
--- a/packages/fs-detectors/test/unit.detect-package-managers.test.ts
+++ b/packages/fs-detectors/test/unit.detect-package-managers.test.ts
@@ -1,6 +1,9 @@
 import path from 'path';
-import { packageManagers, detectFramework } from '../src';
-import { FixtureFilesystem } from './utils/fixture-filesystem';
+import {
+  packageManagers,
+  detectFramework,
+  LocalFileSystemDetector,
+} from '../src';
 
 describe('package-managers', () => {
   describe.each([
@@ -16,7 +19,7 @@ describe('package-managers', () => {
 
     it(testName, async () => {
       const fixture = path.join(__dirname, 'fixtures', fixturePath);
-      const fs = new FixtureFilesystem(fixture);
+      const fs = new LocalFileSystemDetector(fixture);
 
       const result = await detectFramework({
         fs,
diff --git a/packages/fs-detectors/test/unit.detect-workspace-managers.test.ts b/packages/fs-detectors/test/unit.detect-workspace-managers.test.ts
index d634359ad..fdfa12b98 100644
--- a/packages/fs-detectors/test/unit.detect-workspace-managers.test.ts
+++ b/packages/fs-detectors/test/unit.detect-workspace-managers.test.ts
@@ -1,7 +1,7 @@
 import path from 'path';
+import { LocalFileSystemDetector } from '../src';
 import { detectFramework } from '../src/detect-framework';
 import workspaceManagers from '../src/workspaces/workspace-managers';
-import { FixtureFilesystem } from './utils/fixture-filesystem';
 
 describe('workspace-managers', () => {
   describe.each([
@@ -19,7 +19,7 @@ describe('workspace-managers', () => {
 
     it(testName, async () => {
       const fixture = path.join(__dirname, 'fixtures', fixturePath);
-      const fs = new FixtureFilesystem(fixture);
+      const fs = new LocalFileSystemDetector(fixture);
 
       const result = await detectFramework({
         fs,
diff --git a/packages/fs-detectors/test/unit.examples.test.ts b/packages/fs-detectors/test/unit.examples.test.ts
index 1b52b2dc3..f1669b1db 100644
--- a/packages/fs-detectors/test/unit.examples.test.ts
+++ b/packages/fs-detectors/test/unit.examples.test.ts
@@ -1,13 +1,12 @@
 import frameworkList from '@vercel/frameworks';
-import { detectFramework } from '../src';
-import { FixtureFilesystem } from './utils/fixture-filesystem';
+import { detectFramework, LocalFileSystemDetector } from '../src';
 import { getExamples } from '../../../examples/__tests__/test-utils';
 
 describe('examples should be detected', () => {
   it.each(getExamples())(
     'should detect $exampleName',
     async ({ exampleName, examplePath }) => {
-      const fs = new FixtureFilesystem(examplePath);
+      const fs = new LocalFileSystemDetector(examplePath);
       const framework = await detectFramework({ fs, frameworkList });
       if (!framework) {
         throw new Error(`Framework not detected for example "${exampleName}".`);
diff --git a/packages/fs-detectors/test/unit.get-monorepo-default-settings.test.ts b/packages/fs-detectors/test/unit.get-monorepo-default-settings.test.ts
index 9319fab01..eed693c1f 100644
--- a/packages/fs-detectors/test/unit.get-monorepo-default-settings.test.ts
+++ b/packages/fs-detectors/test/unit.get-monorepo-default-settings.test.ts
@@ -1,13 +1,12 @@
+import os from 'os';
+import path from 'path';
+import { mkdtempSync } from 'fs';
 import {
   getMonorepoDefaultSettings,
   LocalFileSystemDetector,
   MissingBuildPipeline,
   MissingBuildTarget,
 } from '../src';
-import path from 'path';
-import fs from 'fs';
-import os from 'os';
-import { FixtureFilesystem } from './utils/fixture-filesystem';
 
 describe('getMonorepoDefaultSettings', () => {
   test('MissingBuildTarget is an error', () => {
@@ -69,7 +68,7 @@ describe('getMonorepoDefaultSettings', () => {
         },
       };
 
-      const ffs = new FixtureFilesystem(
+      const fs = new LocalFileSystemDetector(
         path.join(
           __dirname,
           'fixtures',
@@ -81,16 +80,16 @@ describe('getMonorepoDefaultSettings', () => {
         packageName,
         isRoot ? '/' : 'packages/app-1',
         isRoot ? '/' : '../..',
-        ffs
+        fs
       );
       expect(result).toStrictEqual(expectedResultMap[expectedResultKey]);
     }
   );
 
   test('returns null when neither nx nor turbo is detected', async () => {
-    const dir = fs.mkdtempSync(path.join(os.tmpdir(), 'monorepo-test-'));
-    const lfs = new LocalFileSystemDetector(dir);
-    const result = await getMonorepoDefaultSettings('', '', '', lfs);
+    const dir = mkdtempSync(path.join(os.tmpdir(), 'monorepo-test-'));
+    const fs = new LocalFileSystemDetector(dir);
+    const result = await getMonorepoDefaultSettings('', '', '', fs);
     expect(result).toBe(null);
   });
 });
diff --git a/packages/fs-detectors/test/unit.get-project-paths.test.ts b/packages/fs-detectors/test/unit.get-project-paths.test.ts
index 421c991de..f80e75721 100644
--- a/packages/fs-detectors/test/unit.get-project-paths.test.ts
+++ b/packages/fs-detectors/test/unit.get-project-paths.test.ts
@@ -1,7 +1,7 @@
 import path from 'path';
 import { normalizePath } from '@vercel/build-utils';
 import { getProjectPaths, ProjectPath } from '../src/get-project-paths';
-import { FixtureFilesystem } from './utils/fixture-filesystem';
+import { LocalFileSystemDetector } from '../src';
 
 describe.each<{
   fixturePath: string;
@@ -52,7 +52,7 @@ describe.each<{
 
     it(testName, async () => {
       const fixture = path.join(__dirname, 'fixtures', fixturePath);
-      const fs = new FixtureFilesystem(fixture);
+      const fs = new LocalFileSystemDetector(fixture);
       const mockReaddir = jest.fn().mockImplementation(fs.readdir);
       const mockHasPath = jest.fn().mockImplementation(fs.hasPath);
       fs.readdir = mockReaddir;
diff --git a/packages/fs-detectors/test/unit.get-workspaces-package-paths.test.ts b/packages/fs-detectors/test/unit.get-workspaces-package-paths.test.ts
index db451c19a..cf686b59c 100644
--- a/packages/fs-detectors/test/unit.get-workspaces-package-paths.test.ts
+++ b/packages/fs-detectors/test/unit.get-workspaces-package-paths.test.ts
@@ -1,7 +1,7 @@
 import path from 'path';
 import { getWorkspaces } from '../src/workspaces/get-workspaces';
 import { getWorkspacePackagePaths } from '../src/workspaces/get-workspace-package-paths';
-import { FixtureFilesystem } from './utils/fixture-filesystem';
+import { LocalFileSystemDetector } from '../src';
 
 describe.each<[string, string[]]>([
   ['21-npm-workspaces', ['/a', '/b']],
@@ -32,7 +32,7 @@ describe.each<[string, string[]]>([
 
   it(testName, async () => {
     const fixture = path.join(__dirname, 'fixtures', fixturePath);
-    const fs = new FixtureFilesystem(fixture);
+    const fs = new LocalFileSystemDetector(fixture);
 
     const workspaces = await getWorkspaces({ fs });
     const actualPackagePaths = (
diff --git a/packages/fs-detectors/test/unit.get-workspaces.test.ts b/packages/fs-detectors/test/unit.get-workspaces.test.ts
index 2b77d9d4e..573647c87 100644
--- a/packages/fs-detectors/test/unit.get-workspaces.test.ts
+++ b/packages/fs-detectors/test/unit.get-workspaces.test.ts
@@ -1,6 +1,6 @@
 import path from 'path';
+import { LocalFileSystemDetector } from '../src';
 import { getWorkspaces, Workspace } from '../src/workspaces/get-workspaces';
-import { FixtureFilesystem } from './utils/fixture-filesystem';
 
 describe.each<[string, Workspace[]]>([
   ['21-npm-workspaces', [{ type: 'npm', rootPath: '/' }]],
@@ -34,7 +34,7 @@ describe.each<[string, Workspace[]]>([
 
   it(testName, async () => {
     const fixture = path.join(__dirname, 'fixtures', fixturePath);
-    const fs = new FixtureFilesystem(fixture);
+    const fs = new LocalFileSystemDetector(fixture);
 
     const actualWorkspaces = await getWorkspaces({ fs });
 
diff --git a/packages/fs-detectors/test/unit.local-file-system-detector.test.ts b/packages/fs-detectors/test/unit.local-file-system-detector.test.ts
index 4017922e3..6b91c40a0 100644
--- a/packages/fs-detectors/test/unit.local-file-system-detector.test.ts
+++ b/packages/fs-detectors/test/unit.local-file-system-detector.test.ts
@@ -5,7 +5,7 @@ import { LocalFileSystemDetector, DetectorFilesystem } from '../src';
 
 const tmpdir = path.join(os.tmpdir(), 'local-file-system-test');
 
-const dirs = ['', 'a', 'a/b']; // root, single-nested, double-nested
+const dirs = ['', 'a', `a${path.sep}b`]; // root, single-nested, double-nested
 const files = ['foo', 'bar'];
 const filePaths = dirs.flatMap(dir => files.map(file => path.join(dir, file)));
 
@@ -63,12 +63,7 @@ describe('LocalFileSystemDetector', () => {
     const readdirResults = await Promise.all(
       dirs.map(dir => localFileSystem.readdir(dir))
     );
-    const expectedPaths = [
-      ...dirs.map(dir => path.join(tmpdir, dir)),
-      ...filePaths.map(filePath => path.join(tmpdir, filePath)),
-    ]
-      .sort()
-      .slice(1); // drop the first path since its the root
+    const expectedPaths = [...dirs, ...filePaths].sort().slice(1); // drop the first path since its the root
     const actualPaths = readdirResults
       .flatMap(result => result.map(stat => stat.path))
       .sort();
diff --git a/packages/fs-detectors/test/utils/fixture-filesystem.ts b/packages/fs-detectors/test/utils/fixture-filesystem.ts
deleted file mode 100644
index 4545e3cd1..000000000
--- a/packages/fs-detectors/test/utils/fixture-filesystem.ts
+++ /dev/null
@@ -1,51 +0,0 @@
-import { promises } from 'fs';
-import path from 'path';
-
-import { DetectorFilesystem } from '../../src';
-import { DetectorFilesystemStat } from '../../src/detectors/filesystem';
-
-const { stat, readFile, readdir } = promises;
-
-export class FixtureFilesystem extends DetectorFilesystem {
-  private rootPath: string;
-
-  constructor(fixturePath: string) {
-    super();
-
-    this.rootPath = fixturePath;
-  }
-
-  async _hasPath(name: string): Promise<boolean> {
-    try {
-      const filePath = path.join(this.rootPath, name);
-      await stat(filePath);
-
-      return true;
-    } catch {
-      return false;
-    }
-  }
-  async _readFile(name: string): Promise<Buffer> {
-    const filePath = path.join(this.rootPath, name);
-    return readFile(filePath);
-  }
-  async _isFile(name: string): Promise<boolean> {
-    const filePath = path.join(this.rootPath, name);
-    return (await stat(filePath)).isFile();
-  }
-
-  async _readdir(name: string): Promise<DetectorFilesystemStat[]> {
-    const dirPath = path.join(this.rootPath, name);
-    const files = await readdir(dirPath, { withFileTypes: true });
-
-    return files.map(file => ({
-      name: file.name,
-      type: file.isFile() ? 'file' : 'dir',
-      path: path.join(name, file.name),
-    }));
-  }
-
-  _chdir(name: string): DetectorFilesystem {
-    return new FixtureFilesystem(path.join(this.rootPath, name));
-  }
-}