diff --git a/test/setup-host-validation.test.ts b/test/setup-host-validation.test.ts
new file mode 100644
index 000000000..4e7c0a1fa
--- /dev/null
+++ b/test/setup-host-validation.test.ts
@@ -0,0 +1,45 @@
+import { describe, test, expect } from 'bun:test';
+import { spawnSync } from 'child_process';
+import * as path from 'path';
+import * as os from 'os';
+import * as fs from 'fs';
+
+const ROOT = path.resolve(import.meta.dir, '..');
+const SETUP_SCRIPT = path.join(ROOT, 'setup');
+
+function runSetupHost(host: string): { stderr: string; status: number | null; timedOut: boolean } {
+  const tmpDir = fs.mkdtempSync(path.join(os.tmpdir(), 'gstack-setup-host-'));
+  const r = spawnSync('bash', [SETUP_SCRIPT, '--host', host], {
+    cwd: ROOT,
+    encoding: 'utf-8',
+    input: '',
+    timeout: 3000,
+    env: { ...process.env, HOME: tmpDir },
+  });
+  fs.rmSync(tmpDir, { recursive: true, force: true });
+  return {
+    stderr: r.stderr || '',
+    status: r.status,
+    timedOut: r.signal === 'SIGTERM',
+  };
+}
+
+describe('setup: --host validation accepts all registered hosts', () => {
+  test('--host cursor is accepted (not rejected as unknown)', () => {
+    const r = runSetupHost('cursor');
+    expect(r.stderr).not.toContain('Unknown --host value');
+    expect(r.status).not.toBe(1);
+  });
+
+  test('--host slate is accepted (not rejected as unknown)', () => {
+    const r = runSetupHost('slate');
+    expect(r.stderr).not.toContain('Unknown --host value');
+    expect(r.status).not.toBe(1);
+  });
+
+  test('--host nonexistent is still rejected', () => {
+    const r = runSetupHost('nonexistent');
+    expect(r.stderr).toContain('Unknown --host value');
+    expect(r.status).toBe(1);
+  });
+});