From 5caa5a047e3f98e1a87ca083a499c2f92dcbc1ac Mon Sep 17 00:00:00 2001
From: ValueOn AG <p.motsch@valueon.ch>
Date: Thu, 26 Feb 2026 21:41:56 +0100
Subject: [PATCH] Prevent historical Teams chat replay as fresh transcript
 input.

Add chat warmup guard and key-based deduplication so old thread messages are not re-emitted with new timestamps after join.

Made-with: Cursor
---
 src/bot/chatProcedure.ts | 23 ++++++++++++++++++++++-
 1 file changed, 22 insertions(+), 1 deletion(-)

diff --git a/src/bot/chatProcedure.ts b/src/bot/chatProcedure.ts
index 44c44f5..20ff466 100644
--- a/src/bot/chatProcedure.ts
+++ b/src/bot/chatProcedure.ts
@@ -20,6 +20,8 @@ export class ChatProcedure {
   private _onChatMessage: (entry: ChatMessageEntry) => void;
   private _isSubscribed: boolean = false;
   private _lastMessageText: string = '';
+  private _chatReadyAtMs: number = 0;
+  private _recentMessageKeyTimestamps: Map<string, number> = new Map();
 
   constructor(
     page: Page,
@@ -119,6 +121,7 @@ export class ChatProcedure {
         speaker: string;
         text: string;
         timestamp: string;
+        messageKey?: string;
       }) => {
         this._handleChatMessage(msg);
       });
@@ -204,6 +207,7 @@ export class ChatProcedure {
               speaker: author,
               text,
               timestamp: new Date().toISOString(),
+              messageKey: `${author}::${text}`,
             });
             return true;
           }
@@ -239,6 +243,7 @@ export class ChatProcedure {
                   speaker: candidateName,
                   text: candidateBody,
                   timestamp: new Date().toISOString(),
+                  messageKey: `${candidateName}::${candidateBody}`,
                 });
                 return true;
               }
@@ -320,16 +325,32 @@ export class ChatProcedure {
     });
 
     this._logger.info(`Chat MutationObserver set up (target: ${chatObserverTarget})`);
+    // Guard against Teams replaying historical thread entries as fresh mutations.
+    this._chatReadyAtMs = Date.now() + 12000;
+    this._logger.info('Chat monitor warmup active for 12s');
   }
 
   /**
    * Handle a chat message event from the browser.
    */
-  private _handleChatMessage(msg: { speaker: string; text: string; timestamp: string }): void {
+  private _handleChatMessage(msg: { speaker: string; text: string; timestamp: string; messageKey?: string }): void {
     if (!this._isSubscribed || !msg.text) return;
 
+    const nowMs = Date.now();
+    if (this._chatReadyAtMs > 0 && nowMs < this._chatReadyAtMs) return;
+
     // Dedup
     if (msg.text === this._lastMessageText) return;
+    const key = msg.messageKey || `${msg.speaker}::${msg.text}`;
+    const lastSeen = this._recentMessageKeyTimestamps.get(key);
+    if (lastSeen && (nowMs - lastSeen) < 120000) return;
+    this._recentMessageKeyTimestamps.set(key, nowMs);
+    if (this._recentMessageKeyTimestamps.size > 400) {
+      const cutoff = nowMs - 10 * 60 * 1000;
+      for (const [k, ts] of this._recentMessageKeyTimestamps.entries()) {
+        if (ts < cutoff) this._recentMessageKeyTimestamps.delete(k);
+      }
+    }
     this._lastMessageText = msg.text;
 
     this._logger.info(`Chat: [${msg.speaker}] ${msg.text}`);