refactor: move NIP-29 member list fallback to adapter level

Move the participant fallback logic from ChatViewer to the NIP-29 adapter's
resolveConversation() method. This keeps protocol-specific behavior in the
adapter rather than leaking it into the view.

When no member list events (kind 39001/39002) are found, the adapter now
fetches recent messages (kind 9) and derives participants from message
authors.

https://claude.ai/code/session_01Qikw63P4kxwR6ceCQuFMAM

src/components/ChatViewer.tsx

@@ -31,7 +31,7 @@ import { Nip10Adapter } from "@/lib/chat/adapters/nip-10-adapter";
 import { Nip29Adapter } from "@/lib/chat/adapters/nip-29-adapter";
 import { Nip53Adapter } from "@/lib/chat/adapters/nip-53-adapter";
 import type { ChatProtocolAdapter } from "@/lib/chat/adapters/base-adapter";
-import type { Message, ParticipantRole } from "@/types/chat";
+import type { Message } from "@/types/chat";
 import type { ChatAction } from "@/types/chat-actions";
 import { parseSlashCommand } from "@/lib/chat/slash-command-parser";
 import {
@@ -895,29 +895,6 @@ export function ChatViewer({
       return participants;
     }
 
-    // NIP-29 groups: use static participants but fallback to message authors if empty
-    // Some relays may not provide kind 39001/39002 member list events
-    if (protocol === "nip-29" && messages) {
-      const staticParticipants = conversation?.participants || [];
-
-      // If we have static participants from member list events, use them as base
-      // and augment with message authors
-      const participants: { pubkey: string; role?: ParticipantRole }[] = [
-        ...staticParticipants,
-      ];
-      const seen = new Set(staticParticipants.map((p) => p.pubkey));
-
-      // Add message authors who aren't already in the list as members
-      for (const msg of messages) {
-        if (msg.type !== "system" && !seen.has(msg.author)) {
-          seen.add(msg.author);
-          participants.push({ pubkey: msg.author, role: "member" });
-        }
-      }
-
-      return participants;
-    }
-
     // Other protocols: use static participants from conversation
     return conversation?.participants || [];
   }, [

src/lib/chat/adapters/nip-29-adapter.ts

@@ -269,11 +269,46 @@ export class Nip29Adapter extends ChatProtocolAdapter {
       }
     }
 
-    const participants = Array.from(participantsMap.values());
+    let participants = Array.from(participantsMap.values());
 
     console.log(
       `[NIP-29] Found ${participants.length} participants (${adminEvents.length} admin events, ${memberEvents.length} member events)`,
     );
+
+    // Fallback: if no member list found, derive participants from recent messages
+    if (participants.length === 0) {
+      console.log(
+        `[NIP-29] No member list found, fetching recent messages for participant fallback`,
+      );
+
+      const messagesFilter: Filter = {
+        kinds: [9],
+        "#h": [groupId],
+        limit: 50,
+      };
+
+      const recentMessages = await firstValueFrom(
+        pool
+          .request([relayUrl], [messagesFilter], { eventStore })
+          .pipe(toArray()),
+      );
+
+      // Extract unique authors from messages
+      const messageAuthors = new Set<string>();
+      for (const event of recentMessages) {
+        messageAuthors.add(event.pubkey);
+      }
+
+      participants = Array.from(messageAuthors).map((pubkey) => ({
+        pubkey,
+        role: "member" as const,
+      }));
+
+      console.log(
+        `[NIP-29] Derived ${participants.length} participants from ${recentMessages.length} messages`,
+      );
+    }
+
     console.log(
       `[NIP-29] Metadata - title: ${title}, icon: ${icon}, description: ${description}`,
     );