diff --git a/scripts/postbuild.mjs b/scripts/postbuild.mjs
index 68a967a..eb400aa 100644
--- a/scripts/postbuild.mjs
+++ b/scripts/postbuild.mjs
@@ -1,4 +1,5 @@
-import { copyFileSync } from "node:fs";
+import { copyFileSync, readFileSync, writeFileSync } from "node:fs";
+import { transform } from "esbuild";
 
 // vite-plugin-dts emits a single bundled declaration file. Copy it to the
 // ESM/CJS-specific extensions so each `exports` condition resolves to types
@@ -6,3 +7,11 @@ import { copyFileSync } from "node:fs";
 const source = "dist/driver.js.d.ts";
 copyFileSync(source, "dist/driver.js.d.mts");
 copyFileSync(source, "dist/driver.js.d.cts");
+
+// Vite 8 whitespace-minifies the CJS and IIFE outputs but ships the ESM bundle
+// with its whitespace intact, so run a final esbuild pass on just the .mjs to
+// strip it (~9% smaller gzipped). Identifiers are already mangled and no
+// sourcemaps are shipped, so there is no downside for consumers.
+const esmBundle = "dist/driver.js.mjs";
+const minified = await transform(readFileSync(esmBundle, "utf8"), { minify: true, legalComments: "none" });
+writeFileSync(esmBundle, minified.code);