diff --git a/src/index.ts b/src/index.ts
index c29abb7..2892648 100644
--- a/src/index.ts
+++ b/src/index.ts
@@ -8,6 +8,11 @@ import { AutonomousAgent } from './services/agent.js';
 import { XMCPServer } from './mcp/server.js';
 
 async function main() {
+  // Redirect console.log to stderr so it doesn't conflict with
+  // MCP StdioServerTransport which uses stdout for protocol messages
+  const origLog = console.log;
+  console.log = (...args: any[]) => console.error(...args);
+
   console.log('═══════════════════════════════════════════════════');
   console.log('  MyXstack - Autonomous AI Agent on X (Twitter)');
   console.log('═══════════════════════════════════════════════════\n');
diff --git a/src/services/agent.ts b/src/services/agent.ts
index 326fb38..de10ae7 100644
--- a/src/services/agent.ts
+++ b/src/services/agent.ts
@@ -11,6 +11,7 @@ export class AutonomousAgent {
   private grokService: GrokService;
   private config: AgentConfig;
   private processedMentions: Set<string> = new Set();
+  private static readonly MAX_PROCESSED_MENTIONS = 10000;
   private isRunning: boolean = false;
   private pollingIntervalId: NodeJS.Timeout | null = null;
   private isProcessing: boolean = false;
@@ -95,6 +96,15 @@ export class AutonomousAgent {
         await this.processMention(mention);
         this.processedMentions.add(mention.post.id);
       }
+
+      // Prune oldest entries to prevent unbounded memory growth
+      if (this.processedMentions.size > AutonomousAgent.MAX_PROCESSED_MENTIONS) {
+        const excess = this.processedMentions.size - AutonomousAgent.MAX_PROCESSED_MENTIONS;
+        const iter = this.processedMentions.values();
+        for (let i = 0; i < excess; i++) {
+          this.processedMentions.delete(iter.next().value as string);
+        }
+      }
     } catch (error) {
       console.error('❌ Error in processing loop:', error);
     } finally {
diff --git a/src/services/xapi.ts b/src/services/xapi.ts
index f80be1e..13e92a7 100644
--- a/src/services/xapi.ts
+++ b/src/services/xapi.ts
@@ -44,17 +44,26 @@ export class XAPIClient {
         throw new Error('Failed to get user ID from response');
       }
 
-      const mentionsResponse = await this.makeXAPIRequest(
-        `https://api.twitter.com/2/users/${userId}/mentions?max_results=10&expansions=author_id&tweet.fields=created_at,conversation_id,in_reply_to_user_id,referenced_tweets`,
-        'GET'
-      );
+      let mentionsUrl = `https://api.twitter.com/2/users/${userId}/mentions?max_results=10&expansions=author_id&tweet.fields=created_at,conversation_id,in_reply_to_user_id,referenced_tweets`;
+      if (this.lastMentionId) {
+        mentionsUrl += `&since_id=${this.lastMentionId}`;
+      }
+
+      const mentionsResponse = await this.makeXAPIRequest(mentionsUrl, 'GET');
 
       if (!mentionsResponse || !Array.isArray(mentionsResponse.data)) {
         console.warn('Invalid response from X API (mentions)');
         return [];
       }
 
-      return this.parseMentions(mentionsResponse.data);
+      const mentions = this.parseMentions(mentionsResponse.data);
+
+      // Track the newest mention ID for pagination on the next poll
+      if (mentionsResponse.data.length > 0) {
+        this.lastMentionId = mentionsResponse.data[0].id;
+      }
+
+      return mentions;
     } catch (error) {
       console.error('Error fetching mentions:', error);
       return [];
@@ -77,7 +86,12 @@ export class XAPIClient {
         'GET'
       );
 
-      return this.parseThread(response.data || []);
+      if (!response || !response.data) {
+        console.warn('Invalid response from X API (thread)');
+        return null;
+      }
+
+      return this.parseThread(response.data);
     } catch (error) {
       console.error('Error fetching thread:', error);
       return null;
@@ -184,7 +198,7 @@ export class XAPIClient {
   private parseThread(tweets: { created_at: string; [key: string]: any }[]): XThread | null {
     if (tweets.length === 0) return null;
 
-    const sorted = tweets.sort((a, b) => 
+    const sorted = [...tweets].sort((a, b) =>
       new Date(a.created_at).getTime() - new Date(b.created_at).getTime()
     );