From f93fc92312bc6078fcf58ee58eba3222f7c320a6 Mon Sep 17 00:00:00 2001
From: YanAnghelp <yananghelp@gmail.com>
Date: Fri, 26 Jun 2026 13:04:48 +0800
Subject: [PATCH 1/2] feat: support `server-only` and `client-only` modules
 (#2162)

---
 packages/start/env.d.ts            | 12 ++++++++++++
 packages/start/src/config/index.ts | 23 +++++++++++++++++++++++
 2 files changed, 35 insertions(+)

diff --git a/packages/start/env.d.ts b/packages/start/env.d.ts
index 2c9155d1c..c638b96cd 100644
--- a/packages/start/env.d.ts
+++ b/packages/start/env.d.ts
@@ -7,3 +7,15 @@ declare namespace App {
     [key: string | symbol]: any;
   }
 }
+
+/**
+ * Import `server-only` to ensure this module is never bundled for the client.
+ * Importing it in a client module will throw a build error.
+ */
+declare module "server-only" {}
+
+/**
+ * Import `client-only` to ensure this module is never bundled for the server.
+ * Importing it in a server module will throw a build error.
+ */
+declare module "client-only" {}
diff --git a/packages/start/src/config/index.ts b/packages/start/src/config/index.ts
index 9cdc6830e..77b828901 100644
--- a/packages/start/src/config/index.ts
+++ b/packages/start/src/config/index.ts
@@ -200,6 +200,29 @@ export function solidStart(options?: SolidStartOptions): Array<PluginOption> {
       },
       filter: options?.serverFunctions?.filter,
     }),
+    {
+      name: "solid-start:boundary-modules",
+      enforce: "pre",
+      resolveId(id, importer, { ssr }) {
+        if (id === "server-only") {
+          if (!ssr)
+            this.error(
+              `Attempt to import 'server-only' in a client module: ${importer}`,
+            );
+        } else if (id === "client-only") {
+          if (ssr)
+            this.error(
+              `Attempt to import 'client-only' in a server module: ${importer}`,
+            );
+        } else {
+          return null;
+        }
+        return "\0solid-start:boundary-modules:id";
+      },
+      load(id) {
+        if (id === "\0solid-start:boundary-modules:id") return "export {}";
+      },
+    },
     {
       name: "solid-start:virtual-modules",
       async resolveId(id) {

From 54fc19b3e681461d5ee98a5ea63e016ae16058f6 Mon Sep 17 00:00:00 2001
From: YanAnghelp <yananghelp@gmail.com>
Date: Fri, 26 Jun 2026 16:58:58 +0800
Subject: [PATCH 2/2] chore: add changeset

---
 .changeset/support-server-client-only.md | 5 +++++
 1 file changed, 5 insertions(+)
 create mode 100644 .changeset/support-server-client-only.md

diff --git a/.changeset/support-server-client-only.md b/.changeset/support-server-client-only.md
new file mode 100644
index 000000000..935fe31ee
--- /dev/null
+++ b/.changeset/support-server-client-only.md
@@ -0,0 +1,5 @@
+---
+"@solidjs/start": minor
+---
+
+Add support for `server-only` and `client-only` modules