diff --git a/skills/baoyu-image-gen/scripts/main.test.ts b/skills/baoyu-image-gen/scripts/main.test.ts
index 5f0250e..2c3dd01 100644
--- a/skills/baoyu-image-gen/scripts/main.test.ts
+++ b/skills/baoyu-image-gen/scripts/main.test.ts
@@ -8,6 +8,7 @@ import type { CliArgs, ExtendConfig } from "./types.ts";
 import {
   createTaskArgs,
   detectProvider,
+  ensureDir,
   getConfiguredMaxWorkers,
   getConfiguredProviderRateLimits,
   getWorkerCount,
@@ -201,6 +202,26 @@ batch:
   });
 });
 
+test("ensureDir creates nested dirs, is idempotent on an existing dir, and rethrows for a non-directory", async (t: TestContext) => {
+  const root = await makeTempDir("ensure-dir-");
+  t.after(() => fs.rm(root, { recursive: true, force: true }));
+
+  const nested = path.join(root, "a", "b", "c");
+  await ensureDir(nested);
+  assert.equal((await fs.stat(nested)).isDirectory(), true);
+
+  // Idempotent: a second call on an existing directory must not throw. This is the
+  // Bun-on-Windows regression the helper guards against (Bun wrongly throws EEXIST
+  // for mkdir(existingDir, { recursive: true })).
+  await ensureDir(nested);
+
+  // Rethrows when the path exists but is a file rather than a directory, so a real
+  // EEXIST against a non-directory is not silently swallowed.
+  const filePath = path.join(root, "not-a-dir");
+  await fs.writeFile(filePath, "x");
+  await assert.rejects(() => ensureDir(filePath));
+});
+
 test("loadExtendConfig renames legacy EXTEND.md when the new path is missing", async () => {
   const root = await makeTempDir("baoyu-image-gen-extend-");
   const cwd = path.join(root, "project");
diff --git a/skills/baoyu-image-gen/scripts/main.ts b/skills/baoyu-image-gen/scripts/main.ts
index f08bd9b..8bf99c2 100644
--- a/skills/baoyu-image-gen/scripts/main.ts
+++ b/skills/baoyu-image-gen/scripts/main.ts
@@ -2,7 +2,7 @@ import path from "node:path";
 import process from "node:process";
 import { homedir } from "node:os";
 import { fileURLToPath } from "node:url";
-import { access, mkdir, readFile, rename, writeFile } from "node:fs/promises";
+import { access, mkdir, readFile, rename, stat, writeFile } from "node:fs/promises";
 import type {
   BatchFile,
   BatchTaskInput,
@@ -563,11 +563,25 @@ async function exists(filePath: string): Promise<boolean> {
   }
 }
 
+export async function ensureDir(dir: string): Promise<void> {
+  try {
+    await mkdir(dir, { recursive: true });
+  } catch (err) {
+    // Bun on Windows incorrectly throws EEXIST for mkdir(dir, { recursive: true })
+    // when the directory already exists, contradicting Node's documented contract
+    // (mkdir with recursive: true resolves silently for an existing directory).
+    // Tolerate EEXIST only when the path really is a directory; rethrow otherwise
+    // (e.g. EEXIST raised because the path points at an existing file).
+    if ((err as { code?: string }).code !== "EEXIST") throw err;
+    if (!(await stat(dir)).isDirectory()) throw err;
+  }
+}
+
 async function migrateLegacyExtendConfig(cwd: string, home: string): Promise<void> {
   for (const { current, legacy } of getExtendConfigPathPairs(cwd, home)) {
     const [hasCurrent, hasLegacy] = await Promise.all([exists(current), exists(legacy)]);
     if (hasCurrent || !hasLegacy) continue;
-    await mkdir(path.dirname(current), { recursive: true });
+    await ensureDir(path.dirname(current));
     await rename(legacy, current);
   }
 }
@@ -1049,7 +1063,7 @@ async function prepareBatchTasks(
 }
 
 async function writeImage(outputPath: string, imageData: Uint8Array): Promise<void> {
-  await mkdir(path.dirname(outputPath), { recursive: true });
+  await ensureDir(path.dirname(outputPath));
   await writeFile(outputPath, imageData);
 }