Merge remote-tracking branch 'origin/main' into prompt-token-load-reduction

test/helpers/emulate-bun-windows-eexist.ts

@@ -0,0 +1,20 @@
+/**
+ * Bun --preload fixture that emulates bun-on-Windows fs.mkdirSync semantics
+ * (see #2635): a recursive mkdir on an already-existing directory throws
+ * EEXIST, where Node (and bun on Linux/macOS) treat it as a no-op success.
+ *
+ * Loaded into a child process with `bun --preload <this file> <script>`, it
+ * lets the #2635 regression test exercise the exact Windows crash path on any
+ * platform. The patch is deliberately transparent - it changes nothing except
+ * throwing EEXIST where Windows bun would.
+ */
+const fs = require("fs");
+const orig = fs.mkdirSync;
+fs.mkdirSync = (p: string, opts: any) => {
+  if (opts?.recursive && fs.existsSync(p) && fs.statSync(p).isDirectory()) {
+    const e = new Error(`EEXIST: file already exists, mkdir '${p}'`);
+    (e as any).code = "EEXIST";
+    throw e;
+  }
+  return orig(p, opts);
+};