diff --git a/apps/desktop/scripts/build-main.mjs b/apps/desktop/scripts/build-main.mjs
index 3bdc56d..d58b9f4 100644
--- a/apps/desktop/scripts/build-main.mjs
+++ b/apps/desktop/scripts/build-main.mjs
@@ -12,7 +12,10 @@ await build({
   banner: {
     js: [
       'import { createRequire as __mdToPdfCreateRequire } from "node:module";',
-      "const require = __mdToPdfCreateRequire(import.meta.url);"
+      'import { dirname as __mdToPdfDirname } from "node:path";',
+      'import { fileURLToPath as __mdToPdfFileURLToPath } from "node:url";',
+      "const require = __mdToPdfCreateRequire(import.meta.url);",
+      "const __dirname = __mdToPdfDirname(__mdToPdfFileURLToPath(import.meta.url));"
     ].join("\n")
   }
 });
diff --git a/apps/desktop/tests/release-build.test.ts b/apps/desktop/tests/release-build.test.ts
index 7574b1d..c060d47 100644
--- a/apps/desktop/tests/release-build.test.ts
+++ b/apps/desktop/tests/release-build.test.ts
@@ -92,6 +92,23 @@ describe("桌面发行构建链", () => {
     expect(buildScript).toContain("dist/docx-media-filter.lua");
   });
 
+  it("为 ESM 主进程中的 CommonJS 字体转换依赖保留 __dirname", () => {
+    const buildScript = readFileSync(
+      `${desktopRoot}/scripts/build-main.mjs`,
+      "utf8"
+    );
+
+    expect(buildScript).toContain(
+      'dirname as __mdToPdfDirname'
+    );
+    expect(buildScript).toContain(
+      'fileURLToPath as __mdToPdfFileURLToPath'
+    );
+    expect(buildScript).toContain(
+      "const __dirname = __mdToPdfDirname(__mdToPdfFileURLToPath(import.meta.url));"
+    );
+  });
+
   it("在 Docker Web 构建前复制样例并保留到运行镜像", () => {
     const dockerfile = readFileSync(
       `${projectRoot}/deploy/Dockerfile`,