From ac5a8a0863152256281a569e1e1a7c471cbc2a37 Mon Sep 17 00:00:00 2001
From: Devin AI <158243242+devin-ai-integration[bot]@users.noreply.github.com>
Date: Sun, 13 Sep 2026 17:04:37 +0000
Subject: [PATCH] docs(typescript): document esmOnly generator option

Co-Authored-By: Devin AI <158243242+devin-ai-integration[bot]@users.noreply.github.com>
---
 .../sdks/generators/typescript/configuration.mdx | 16 ++++++++++++++++
 1 file changed, 16 insertions(+)

diff --git a/fern/products/sdks/generators/typescript/configuration.mdx b/fern/products/sdks/generators/typescript/configuration.mdx
index c5c100575..d01231486 100644
--- a/fern/products/sdks/generators/typescript/configuration.mdx
+++ b/fern/products/sdks/generators/typescript/configuration.mdx
@@ -88,6 +88,22 @@ const bar: MyRootType.Foo.Bar = {};
 ```
 </ParamField>
 
+<ParamField path="esmOnly" type="boolean" default="false" toc={true}>
+Ships only the ECMAScript module (ESM) build of the generated package. By default, the generator publishes both CommonJS and ESM builds, which exposes consumers to the [dual package hazard](https://github.com/GeoffreyBooth/dual-package-hazard). When enabled, `package.json` sets `"type": "module"`, `main`, `module`, and `types` point at `./dist/esm/index.mjs` and `./dist/esm/index.d.mts`, the `exports` map (including subpackage exports) has no `require` conditions, and no `tsconfig.cjs.json` or `build:cjs` script is generated.
+
+`esmOnly` can't be combined with `useLegacyExports: true` or `bundle: true`; generation fails with an error.
+
+```yml title="generators.yml"
+groups:
+  ts-sdk:
+    generators:
+      - name: fern-typescript-sdk
+        version: <Markdown src="/snippets/version-number-ts.mdx"/>
+        config:
+          esmOnly: true
+```
+</ParamField>
+
 <ParamField path="extraDependencies" type="object" default="{}" toc={true}>
 
 <Markdown src="/snippets/enterprise-plan.mdx"/>