diff --git a/packages/server/vitest.config.ts b/packages/server/vitest.config.ts
index 4b25764445..c80345c79e 100644
--- a/packages/server/vitest.config.ts
+++ b/packages/server/vitest.config.ts
@@ -19,9 +19,9 @@ export default defineConfig({
     setupFiles: [path.resolve(__dirname, "./src/test-utils/vitest-setup.ts")],
     pool: "forks",
     fileParallelism: false,
-    // Windows runners intermittently starve subprocess-heavy Git tests at the
-    // default worker count, leaving child processes alive past their deadlines.
-    maxWorkers: process.platform === "win32" ? 2 : undefined,
+    // Even two concurrent Git-heavy suites can exhaust Windows test deadlines.
+    // Run files serially so their subprocesses do not compete across suites.
+    maxWorkers: process.platform === "win32" ? 1 : undefined,
     exclude: ["**/node_modules/**", "**/dist/**", "**/.claude/**", "**/.dev/**"],
   },
 });