fix: concluded discussions suppress turns and send single auto-reply

Two bugs in concluded discussion channel handling:

1. before_model_resolve did not check rec.discussion.concluded, so it
   still initialized the speaker list and ran turn management. Fixed by
   returning NO_REPLY early for concluded discussions (same as report mode).

2. message_received fired for all agent VM contexts, causing multiple
   "This discussion is closed" auto-replies per incoming message. Fixed
   with process-level dedup keyed on channelId:messageId (same pattern
   as agent_end runId dedup). Also fixed message_id extraction to look
   in metadata.conversation_info.message_id first.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

plugin/hooks/before-model-resolve.ts

@@ -60,6 +60,12 @@ export function registerBeforeModelResolveHook(deps: Deps): void {
     // dead mode: suppress all responses
     if (mode === "report" || mode === "dead" as string) return NO_REPLY;
 
+    // concluded discussion: suppress all agent responses (auto-reply handled by message_received)
+    if (mode === "discussion") {
+      const rec = channelStore.getRecord(channelId);
+      if (rec.discussion?.concluded) return NO_REPLY;
+    }
+
     // disabled modes: let agents respond freely
     if (mode === "none" || mode === "work") return;
 

plugin/hooks/message-received.ts

@@ -16,6 +16,18 @@ type Deps = {
   interruptTailMatch: InterruptFn;
 };
 
+/**
+ * Process-level dedup for concluded-discussion auto-replies.
+ * Multiple agent VM contexts all fire message_received for the same incoming message;
+ * only the first should send the "This discussion is closed" reply.
+ * Keyed on channelId:messageId; evicted after 500 entries.
+ */
+const _CONCLUDED_REPLY_DEDUP_KEY = "_dirigentConcludedReplyDedup";
+if (!(globalThis as Record<string, unknown>)[_CONCLUDED_REPLY_DEDUP_KEY]) {
+  (globalThis as Record<string, unknown>)[_CONCLUDED_REPLY_DEDUP_KEY] = new Set<string>();
+}
+const concludedReplyDedup: Set<string> = (globalThis as Record<string, unknown>)[_CONCLUDED_REPLY_DEDUP_KEY] as Set<string>;
+
 export function registerMessageReceivedHook(deps: Deps): void {
   const { api, channelStore, identityRegistry, moderatorBotToken, scheduleIdentifier, interruptTailMatch } = deps;
   // Derive the moderator bot's own Discord user ID so we can skip self-messages
@@ -61,15 +73,31 @@ export function registerMessageReceivedHook(deps: Deps): void {
       // but we handle archived auto-reply here)
       if (mode === "report") return;
 
-      // archived: auto-reply via moderator
+      // archived: auto-reply via moderator (deduped — only one agent instance should reply)
       if (mode === "discussion") {
         const rec = channelStore.getRecord(channelId);
         if (rec.discussion?.concluded && moderatorBotToken) {
-          await sendModeratorMessage(
+          const metadata = e.metadata as Record<string, unknown> | undefined;
-            moderatorBotToken, channelId,
+          const convInfo = metadata?.conversation_info as Record<string, unknown> | undefined;
-            "This discussion is closed and no longer active.",
+          const incomingMsgId = String(
-            api.logger,
+            convInfo?.message_id ??
-          ).catch(() => undefined);
+            metadata?.message_id ??
+            metadata?.messageId ??
+            e.id ?? "",
+          );
+          const dedupKey = `${channelId}:${incomingMsgId}`;
+          if (!concludedReplyDedup.has(dedupKey)) {
+            concludedReplyDedup.add(dedupKey);
+            if (concludedReplyDedup.size > 500) {
+              const oldest = concludedReplyDedup.values().next().value;
+              if (oldest) concludedReplyDedup.delete(oldest);
+            }
+            await sendModeratorMessage(
+              moderatorBotToken, channelId,
+              "This discussion is closed and no longer active.",
+              api.logger,
+            ).catch(() => undefined);
+          }
           return;
         }
       }