diff --git a/src/plugins/astro.test.ts b/src/plugins/astro.test.ts
new file mode 100644
index 0000000..e6b3567
--- /dev/null
+++ b/src/plugins/astro.test.ts
@@ -0,0 +1,99 @@
+import { fileURLToPath } from 'url';
+import { describe, expect, it, vi, beforeEach } from 'vitest';
+import { aeoAstroIntegration } from './astro';
+
+const fsMocks = vi.hoisted(() => ({
+  existsSync: vi.fn(),
+  mkdirSync: vi.fn(),
+  readFileSync: vi.fn(),
+  readdirSync: vi.fn(),
+  statSync: vi.fn(),
+  writeFileSync: vi.fn(),
+}));
+
+vi.mock('fs', () => fsMocks);
+
+describe('aeoAstroIntegration', () => {
+  beforeEach(() => {
+    vi.clearAllMocks();
+  });
+
+  it('uses native filesystem paths for Astro file URLs in dev', () => {
+    fsMocks.existsSync.mockReturnValue(false);
+
+    const publicDir = new URL('file:///C:/mock/project/public');
+    const outDir = new URL('file:///C:/mock/project/dist');
+    const integration = aeoAstroIntegration({ widget: { enabled: false } });
+
+    integration.hooks['astro:config:setup']({
+      config: { publicDir, outDir },
+      command: 'dev',
+    });
+
+    expect(fsMocks.mkdirSync).toHaveBeenCalledWith(fileURLToPath(publicDir), { recursive: true });
+  });
+
+  it('uses native filesystem paths for Astro file URLs in build (astro:config:setup)', () => {
+    fsMocks.existsSync.mockReturnValue(false);
+
+    const publicDir = new URL('file:///C:/mock/project/public');
+    const outDir = new URL('file:///C:/mock/project/dist');
+    const integration = aeoAstroIntegration({ widget: { enabled: false } });
+
+    // In build mode, outDir is used (not publicDir for mkdirSync)
+    // The key thing is that toFileSystemPath is called on outDir without throwing
+    expect(() => {
+      integration.hooks['astro:config:setup']({
+        config: { publicDir, outDir },
+        command: 'build',
+      });
+    }).not.toThrow();
+  });
+
+  it('uses native filesystem paths for Windows file URLs in astro:build:done hook', async () => {
+    // Simulate an empty build output directory so scanBuiltPages returns no pages
+    fsMocks.readdirSync.mockReturnValue([]);
+    fsMocks.existsSync.mockReturnValue(false);
+
+    const publicDir = new URL('file:///C:/mock/project/public');
+    const outDir = new URL('file:///C:/mock/project/dist');
+    const dir = new URL('file:///C:/mock/project/dist/');
+    const integration = aeoAstroIntegration({ url: 'https://example.com', widget: { enabled: false } });
+
+    const logger = {
+      fork: () => ({
+        info: vi.fn(),
+        debug: vi.fn(),
+        error: vi.fn(),
+      }),
+    };
+
+    // astro:build:done uses astroConfig.site which is set during astro:config:setup
+    integration.hooks['astro:config:setup']({
+      config: { publicDir, outDir, site: 'https://example.com' },
+      command: 'build',
+    });
+
+    // Should resolve the Windows file URL to a filesystem path without throwing
+    await expect(
+      integration.hooks['astro:build:done']({ dir, logger })
+    ).resolves.not.toThrow();
+
+    // readdirSync should have been called with the converted Windows path
+    expect(fsMocks.readdirSync).toHaveBeenCalledWith(fileURLToPath(dir));
+  });
+
+  it('toFileSystemPath throws a descriptive error for non-file: URLs', () => {
+    // Access the integration to trigger the module load; the guard is tested via
+    // astro:config:setup with a non-file URL object passed as outDir
+    const integration = aeoAstroIntegration({ widget: { enabled: false } });
+
+    const nonFileUrl = new URL('https://example.com/dist');
+    expect(() => {
+      integration.hooks['astro:config:setup']({
+        config: { publicDir: nonFileUrl, outDir: nonFileUrl },
+        command: 'build',
+      });
+    }).toThrow(/expected a file: URL/);
+  });
+});
diff --git a/src/plugins/astro.ts b/src/plugins/astro.ts
index 05daf59..45c00d5 100644
--- a/src/plugins/astro.ts
+++ b/src/plugins/astro.ts
@@ -3,6 +3,7 @@ import { resolveConfig } from '../core/utils';
 import type { AeoConfig, PageEntry, ResolvedAeoConfig } from '../types';
 import { join, resolve, sep } from 'path';
 import { existsSync, mkdirSync, readFileSync, readdirSync, statSync, writeFileSync } from 'fs';
+import { fileURLToPath } from 'url';
 import { extractTextFromHtml, extractTitle, extractDescription, htmlToMarkdown } from '../core/html-extract';
 import { generateSiteSchemas, generatePageSchemas, generateJsonLdScript } from '../core/schema';
 import { generateOGTagsHtml } from '../core/opengraph';
@@ -96,6 +97,19 @@ function escapeAttr(str: string): string {
   return str.replace(/&/g, '&amp;').replace(/"/g, '&quot;').replace(/</g, '&lt;').replace(/>/g, '&gt;');
 }
 
+function toFileSystemPath(pathOrUrl: string | URL): string {
+  if (pathOrUrl instanceof URL) {
+    if (pathOrUrl.protocol !== 'file:') {
+      throw new TypeError(
+        `toFileSystemPath: expected a file: URL but received "${pathOrUrl.protocol}" — cannot convert to a filesystem path`
+      );
+    }
+    return fileURLToPath(pathOrUrl);
+  }
+
+  return pathOrUrl.replace(/^\/([A-Za-z]:)(?=\/|\\)/, '$1');
+}
+
 /**
  * Inject meta description, canonical URL, OG tags, and JSON-LD into each built HTML page's <head>.
  * Skips tags that already exist in the page.
@@ -181,11 +195,11 @@ export function aeoAstroIntegration(options: AeoConfig = {}): any {
         resolvedConfig = resolveConfig({
           ...options,
           contentDir: options.contentDir || 'src/content',
-          outDir: options.outDir || (command === 'build' ? config.outDir.pathname : config.publicDir.pathname),
+          outDir: options.outDir || (command === 'build' ? toFileSystemPath(config.outDir) : toFileSystemPath(config.publicDir)),
         });
 
         if (command === 'dev') {
-          const publicPath = config.publicDir.pathname;
+          const publicPath = toFileSystemPath(config.publicDir);
           if (!existsSync(publicPath)) {
             mkdirSync(publicPath, { recursive: true });
           }
@@ -228,7 +242,7 @@ if (!document.querySelector('meta[name="astro-view-transitions-enabled"]')) {
         const buildLogger = logger.fork('aeo.js');
         buildLogger.info('Generating AEO files...');
 
-        const outPath = dir instanceof URL ? dir.pathname : (dir || astroConfig.outDir.pathname);
+        const outPath = toFileSystemPath(dir || astroConfig.outDir);
         const siteUrl = options.url || astroConfig.site || 'https://example.com';
 
         const discoveredPages = scanBuiltPages(outPath, siteUrl);