From ada6e7782344ce2b5f5ed6f2fea48a242811cd03 Mon Sep 17 00:00:00 2001
From: Pratyush Sharma <56130065+pratyush618@users.noreply.github.com>
Date: Tue, 10 Mar 2026 13:38:23 +0530
Subject: [PATCH] fix(server-runtime,server-sdk): accept plain JSON from
 external WebSocket clients (#1234)

---
 packages/server-runtime/src/index.ts | 17 ++++++++++++++++-
 packages/server-sdk/src/client.ts    | 10 ++++++++--
 2 files changed, 24 insertions(+), 3 deletions(-)

diff --git a/packages/server-runtime/src/index.ts b/packages/server-runtime/src/index.ts
index a8e8e2126..ddf00d343 100644
--- a/packages/server-runtime/src/index.ts
+++ b/packages/server-runtime/src/index.ts
@@ -257,7 +257,22 @@ export function setupApp(options?: {
         // superjson.parse here instead of message.json() (which uses JSON.parse).
         // Using JSON.parse on a superjson-encoded string returns the wrapper object
         // { json: {...}, meta: {...} } with type=undefined, which breaks all event routing.
-        event = parse<WebSocketEvent>(message.text())
+        //
+        // However, external clients may send plain JSON (not superjson-encoded).
+        // superjson.parse on plain JSON returns undefined since there is no `json` wrapper key.
+        // In that case, fall back to JSON.parse so external clients can interoperate.
+        const text = message.text()
+        const parsed = parse<WebSocketEvent>(text)
+        const potentialEvent = (parsed && typeof parsed === 'object' && 'type' in parsed)
+          ? parsed
+          : JSON.parse(text)
+
+        if (!potentialEvent || typeof potentialEvent !== 'object' || !('type' in potentialEvent)) {
+          send(peer, RESPONSES.error('invalid event format', instanceId))
+          return
+        }
+
+        event = potentialEvent as WebSocketEvent
       }
       catch (err) {
         const errorMessage = err instanceof Error ? err.message : String(err)
diff --git a/packages/server-sdk/src/client.ts b/packages/server-sdk/src/client.ts
index 9e9afeaba..fad7027bf 100644
--- a/packages/server-sdk/src/client.ts
+++ b/packages/server-sdk/src/client.ts
@@ -262,8 +262,14 @@ export class Client<C = undefined> {
 
   private async handleMessage(event: MessageEvent) {
     try {
-      const data = superjson.parse<WebSocketEvent<C> | undefined>(event.data as string)
-      if (!data) {
+      // Try superjson first (used by SDK clients), fall back to plain JSON
+      // for external clients that send standard JSON-encoded messages.
+      const raw = event.data as string
+      const parsed = superjson.parse<WebSocketEvent<C> | undefined>(raw)
+      const data = (parsed && typeof parsed === 'object' && 'type' in parsed)
+        ? parsed
+        : JSON.parse(raw) as WebSocketEvent<C>
+      if (!data || typeof data !== 'object' || !('type' in data)) {
         console.warn('Received empty message')
         return
       }