diff --git a/tools/subagent-prompt-prefix.test.mjs b/tools/subagent-prompt-prefix.test.mjs
index e3f2469a..f2c97def 100644
--- a/tools/subagent-prompt-prefix.test.mjs
+++ b/tools/subagent-prompt-prefix.test.mjs
@@ -82,11 +82,15 @@ test('hook fail-open on malformed stdin', () => {
 });
 
 test('hook fail-open when git not available', () => {
+  // Cross-platform: set PATH to node's own directory only — node spawns OK,
+  // git not in node's bin dir → ENOENT → hook fail-opens per spec §4.5.
+  // (Previous approach `PATH: ''` kills node.exe spawn resolution on Windows.)
+  const nodeDir = dirname(process.execPath);
   const result = spawnSync('node', [HOOK_PATH], {
     input: JSON.stringify({ tool_name: 'Task', tool_input: { prompt: 'x' } }),
     encoding: 'utf8',
     timeout: 5000,
-    env: { ...process.env, PATH: '' }, // strip PATH → git not found
+    env: { PATH: nodeDir, PATHEXT: process.env.PATHEXT || '.EXE' },
   });
   assert.equal(result.status, 0, `should not crash when git missing; stderr: ${result.stderr}`);
 });