diff --git a/src/build-manifest.test.ts b/src/build-manifest.test.ts
index 64a9580b..45b2e862 100644
--- a/src/build-manifest.test.ts
+++ b/src/build-manifest.test.ts
@@ -3,7 +3,7 @@ import * as fs from 'node:fs';
 import * as os from 'node:os';
 import * as path from 'node:path';
 import { cli, getRegistry, Strategy } from './registry.js';
-import { loadManifestEntries } from './build-manifest.js';
+import { loadManifestEntries, serializeManifest } from './build-manifest.js';
 
 describe('manifest helper rules', () => {
   const tempDirs: string[] = [];
@@ -83,8 +83,9 @@ describe('manifest helper rules', () => {
         replacedBy: 'opencli demo new',
       },
     ]);
-    // Verify sourceFile is included
+    // Verify sourceFile is included and normalized for cross-platform builds.
     expect(entries[0].sourceFile).toBeDefined();
+    expect(entries[0].sourceFile).not.toContain('\\');
 
     getRegistry().delete(key);
   });
@@ -155,4 +156,11 @@ describe('manifest helper rules', () => {
     getRegistry().delete(screenKey);
     getRegistry().delete(statusKey);
   });
+
+  it('serializes manifest json with a trailing newline', () => {
+    const serialized = serializeManifest([{ site: 'demo', name: 'status', description: '', strategy: 'public', browser: false, args: [], type: 'js' }]);
+
+    expect(serialized.endsWith('\n')).toBe(true);
+    expect(serialized).toContain('\n]');
+  });
 });
diff --git a/src/build-manifest.ts b/src/build-manifest.ts
index e5e3db22..9eaaa46b 100644
--- a/src/build-manifest.ts
+++ b/src/build-manifest.ts
@@ -75,6 +75,10 @@ function toModulePath(filePath: string, site: string): string {
   return `${site}/${baseName}.js`;
 }
 
+function toManifestRelativePath(filePath: string): string {
+  return path.relative(CLIS_DIR, filePath).split(path.sep).join('/');
+}
+
 function isCliCommandValue(value: unknown, site: string): value is CliCommand {
   return isRecord(value)
     && typeof value.site === 'string'
@@ -133,8 +137,9 @@ export async function loadManifestEntries(
         })
         .map(([, cmd]) => cmd);
 
-    // Resolve sourceFile relative to clis/.
-    const sourceRelative = path.relative(CLIS_DIR, filePath);
+    // Resolve sourceFile relative to clis/ using POSIX separators so the
+    // generated manifest stays stable across Windows and Unix builds.
+    const sourceRelative = toManifestRelativePath(filePath);
 
     const seen = new Set<string>();
     return runtimeCommands
@@ -178,10 +183,14 @@ export async function buildManifest(): Promise<ManifestEntry[]> {
   return [...manifest.values()].sort((a, b) => a.site.localeCompare(b.site) || a.name.localeCompare(b.name));
 }
 
+export function serializeManifest(manifest: ManifestEntry[]): string {
+  return `${JSON.stringify(manifest, null, 2)}\n`;
+}
+
 async function main(): Promise<void> {
   const manifest = await buildManifest();
   fs.mkdirSync(path.dirname(OUTPUT), { recursive: true });
-  fs.writeFileSync(OUTPUT, JSON.stringify(manifest, null, 2));
+  fs.writeFileSync(OUTPUT, serializeManifest(manifest));
 
   console.log(`✅ Manifest compiled: ${manifest.length} entries → ${OUTPUT}`);
 
diff --git a/src/engine.test.ts b/src/engine.test.ts
index a8310bd8..dcd87b71 100644
--- a/src/engine.test.ts
+++ b/src/engine.test.ts
@@ -148,6 +148,7 @@ describe('discoverPlugins', () => {
   const symlinkTargetDir = path.join(os.tmpdir(), '__test-plugin-symlink-target__');
   const symlinkPluginDir = path.join(PLUGINS_DIR, '__test-plugin-symlink__');
   const brokenSymlinkDir = path.join(PLUGINS_DIR, '__test-plugin-broken__');
+  const dirLinkType: fs.symlink.Type = process.platform === 'win32' ? 'junction' : 'dir';
 
   afterEach(async () => {
     try { await fs.promises.rm(testPluginDir, { recursive: true }); } catch {}
@@ -188,7 +189,7 @@ description: Test plugin greeting via symlink
 strategy: public
 browser: false
 `);
-    await fs.promises.symlink(symlinkTargetDir, symlinkPluginDir, 'dir');
+    await fs.promises.symlink(symlinkTargetDir, symlinkPluginDir, dirLinkType);
 
     await discoverPlugins();
 
@@ -198,7 +199,7 @@ browser: false
 
   it('skips broken plugin symlinks without throwing', async () => {
     await fs.promises.mkdir(PLUGINS_DIR, { recursive: true });
-    await fs.promises.symlink(path.join(os.tmpdir(), '__missing-plugin-target__'), brokenSymlinkDir, 'dir');
+    await fs.promises.symlink(path.join(os.tmpdir(), '__missing-plugin-target__'), brokenSymlinkDir, dirLinkType);
 
     await expect(discoverPlugins()).resolves.not.toThrow();
     expect(getRegistry().get('__test-plugin-broken__/hello')).toBeUndefined();