diff --git a/documentation/docs/25-build-and-deploy/40-adapter-node.md b/documentation/docs/25-build-and-deploy/40-adapter-node.md
index 347396904790..5718378926db 100644
--- a/documentation/docs/25-build-and-deploy/40-adapter-node.md
+++ b/documentation/docs/25-build-and-deploy/40-adapter-node.md
@@ -273,3 +273,7 @@ app.listen(3000, () => {
 	console.log('listening on port 3000');
 });
 ```
+
+> [!NOTE] When you use `handler.js` in a custom server, only the environment variables read by the handler itself take effect: `ORIGIN`, `PROTOCOL_HEADER`, `HOST_HEADER`, `PORT_HEADER`, `ADDRESS_HEADER`, `XFF_DEPTH`, and `BODY_SIZE_LIMIT`.
+>
+> The server-lifecycle variables (`PORT`, `HOST`, `SOCKET_PATH`, `SHUTDOWN_TIMEOUT`, `IDLE_TIMEOUT`, `KEEP_ALIVE_TIMEOUT`, `HEADERS_TIMEOUT`, `LISTEN_PID`, `LISTEN_FDS`) are only honored by the default `node build` server. Implement them yourself in a custom server if you need the same behavior — for example, the snippet above listens on a hardcoded `3000` regardless of `PORT`.