diff --git a/action.yml b/action.yml
index 2b5d045..380280d 100644
--- a/action.yml
+++ b/action.yml
@@ -133,5 +133,5 @@ outputs:
     description: "GitHub App slug"
 runs:
   using: "node24"
-  main: "dist/bootstrap.cjs"
-  post: "dist/post.cjs"
+  main: "dist/bootstrap.js"
+  post: "dist/post.js"
diff --git a/bootstrap.js b/bootstrap.js
index 845c7a3..0619965 100644
--- a/bootstrap.js
+++ b/bootstrap.js
@@ -1,4 +1,4 @@
-// Enable env-based proxy support (honors explicit opt-out if caller set NODE_USE_ENV_PROXY)
+// Enable env-based proxy support before loading the main bundle (unless caller explicitly set NODE_USE_ENV_PROXY)
 if (process.env.NODE_USE_ENV_PROXY == null) {
   process.env.NODE_USE_ENV_PROXY = "1";
 }
diff --git a/package.json b/package.json
index 2123f18..76a73cb 100644
--- a/package.json
+++ b/package.json
@@ -8,7 +8,7 @@
     "node": ">=24.4.0"
   },
   "scripts": {
-  "build": "esbuild bootstrap.js main.js post.js --bundle --outdir=dist --out-extension:.js=.cjs --platform=node --packages=bundle",
+  "build": "esbuild bootstrap.js main.js post.js --bundle --outdir=dist --format=esm --platform=node --packages=bundle",
     "test": "c8 --100 ava tests/index.js",
     "coverage": "c8 report --reporter html",
     "postcoverage": "open-cli coverage/index.html"