fix(subscription): gracefully handle in-flight updates for cancelled subscriptions (#379)

* Default to last visited replica

* fix(subscription): gracefully handle in-flight updates for cancelled subscriptions

Previously, integrate() would throw an error ("Subscription is cancelled")
if an update arrived after the subscription had been cancelled. This happened
due to a race condition where in-flight updates were still delivered even
after the subscription was removed from active subscriber lists.

Now, integrate() checks if the subscription’s controller is missing and
logs a warning while ignoring the update, rather than throwing an error.
This ensures that cancelled subscriptions do not cause fatal errors while
preventing memory leaks by properly unwatching and clearing subscriber channels.

fixes #378

Author: anotherjesse

typescript/packages/common-memory/subscription.ts

@@ -78,7 +78,7 @@ export const integrate = (session: Session, change: In<State>) => {
   if (session.controller) {
     session.controller.enqueue(change);
   } else {
-    throw new Error("Subscription is cancelled");
+    console.warn("Subscription is cancelled, not integrating change", change);
   }
 };
 

typescript/packages/jumble/src/contexts/CharmManagerContext.tsx

@@ -11,7 +11,17 @@ const CharmManagerContext = createContext<CharmManagerContextType>(null!);
 
 export const CharmsManagerProvider: React.FC<{ children: React.ReactNode }> = ({ children }) => {
   const { replicaName } = useParams<{ replicaName: string }>();
-  const effectiveReplica = replicaName || "common-knowledge";
+
+  let effectiveReplica: string;
+  if (replicaName) {
+    // When a replica is provided in the URL, use it and save it as the last visited
+    effectiveReplica = replicaName;
+    localStorage.setItem("lastReplica", replicaName);
+  } else {
+    // Otherwise, pull the last visited replica from local storage.
+    // Falling back to "common-knowledge" if nothing was stored.
+    effectiveReplica = localStorage.getItem("lastReplica") || "common-knowledge";
+  }
 
   const charmManager = useMemo(() => {
     const storageType = (import.meta as any).env.VITE_STORAGE_TYPE ?? "remote";