diff --git a/package.json b/package.json
index 3f6c269aee7..839b8e79584 100644
--- a/package.json
+++ b/package.json
@@ -3,7 +3,7 @@
   "private": true,
   "type": "module",
   "scripts": {
-    "prepare": "effect-tsgo patch && vp config --no-agent",
+    "prepare": "node scripts/clean-tsgo-backups.mjs && effect-tsgo patch && vp config --no-agent",
     "dev": "node scripts/dev-runner.ts dev",
     "dev:share": "node scripts/dev-runner.ts dev --share",
     "dev:server": "node scripts/dev-runner.ts dev:server",
diff --git a/scripts/clean-tsgo-backups.mjs b/scripts/clean-tsgo-backups.mjs
new file mode 100644
index 00000000000..43012a69bd3
--- /dev/null
+++ b/scripts/clean-tsgo-backups.mjs
@@ -0,0 +1,24 @@
+// Deletes stale tsgo backup files left behind by `effect-tsgo patch`.
+//
+// The patch command backs up the real tsgo binary to `tsgo.original`, and if
+// that name is taken it writes `tsgo.original.1`, `.2`, ... without ever
+// cleaning up. On runners that restore node_modules from a build cache
+// (Vercel), backups accumulate across deploys until patch hard-fails at 101
+// with "Too many backup files exist". Removing them is safe: from the second
+// patch onward the backup is just the previously-patched binary, and pnpm
+// restores the pristine one whenever the package is re-materialized.
+//
+// Runs as part of `prepare`, so it must only use node builtins.
+import * as NodeFS from "node:fs";
+
+const backups = NodeFS.globSync(
+  "node_modules/.pnpm/@typescript+native-preview-*/node_modules/@typescript/native-preview-*/lib/tsgo{,.exe}.original*",
+);
+
+for (const backup of backups) {
+  NodeFS.rmSync(backup, { force: true });
+}
+
+if (backups.length > 0) {
+  console.log(`Removed ${backups.length} stale tsgo backup(s)`);
+}