diff --git a/plugins/codex/scripts/lib/git.mjs b/plugins/codex/scripts/lib/git.mjs
index 1c0529a..9b3b765 100644
--- a/plugins/codex/scripts/lib/git.mjs
+++ b/plugins/codex/scripts/lib/git.mjs
@@ -133,9 +133,12 @@ function formatSection(title, body) {
   return [`## ${title}`, "", body.trim() ? body.trim() : "(none)", ""].join("\n");
 }
 
-function formatUntrackedFile(cwd, relativePath) {
+export function formatUntrackedFile(cwd, relativePath) {
   const absolutePath = path.join(cwd, relativePath);
   const stat = fs.statSync(absolutePath);
+  if (stat.isDirectory()) {
+    return `### ${relativePath}\n(skipped: directory)`;
+  }
   if (stat.size > MAX_UNTRACKED_BYTES) {
     return `### ${relativePath}\n(skipped: ${stat.size} bytes exceeds ${MAX_UNTRACKED_BYTES} byte limit)`;
   }
diff --git a/tests/git.test.mjs b/tests/git.test.mjs
index 7ea1a04..af923f3 100644
--- a/tests/git.test.mjs
+++ b/tests/git.test.mjs
@@ -3,7 +3,7 @@ import path from "node:path";
 import test from "node:test";
 import assert from "node:assert/strict";
 
-import { collectReviewContext, resolveReviewTarget } from "../plugins/codex/scripts/lib/git.mjs";
+import { collectReviewContext, formatUntrackedFile, resolveReviewTarget } from "../plugins/codex/scripts/lib/git.mjs";
 import { initGitRepo, makeTempDir, run } from "./helpers.mjs";
 
 test("resolveReviewTarget prefers working tree when repo is dirty", () => {
@@ -68,3 +68,13 @@ test("resolveReviewTarget requires an explicit base when no default branch can b
     /Unable to detect the repository default branch\. Pass --base <ref> or use --scope working-tree\./
   );
 });
+
+test("formatUntrackedFile skips directories instead of throwing EISDIR", () => {
+  const cwd = makeTempDir();
+  fs.mkdirSync(path.join(cwd, "some-dir"));
+
+  const result = formatUntrackedFile(cwd, "some-dir");
+
+  assert.match(result, /skipped: directory/);
+  assert.match(result, /some-dir/);
+});