diff --git a/README.md b/README.md
index 23ca054..8b858b4 100644
--- a/README.md
+++ b/README.md
@@ -1,6 +1,6 @@
 # MyXstack
 
-This repository hosts a lightweight, step-by-step guide for setting up an autonomous X (Twitter) agent system that  acts based on thread context & reasoning, through Grok via the xMCP server. 
+This repository hosts a lightweight, step-by-step guide for setting up an autonomous X (Twitter) agent system that acts based on thread context and reasoning, through Grok via the xMCP server. 
 
 ## Phase 1: Gather prerequisites & accounts (1–2 hours)
 
@@ -20,8 +20,8 @@ This repository hosts a lightweight, step-by-step guide for setting up an autono
 3. Note the bot user ID (you can fetch this via the API later).
 
 ### xAI / Grok API key
-. Visit <https://console.x.ai>, open the API keys section, and create a key that starts with `xai-`.
-. Store the key securely.
+1. Visit <https://console.x.ai>, open the API keys section, and create a key that starts with `xai-`.
+2. Store the key securely.
 
 ### Local tooling
 - Install Python 3.9+ (3.10–3.13 recommended).
diff --git a/package-lock.json b/package-lock.json
index 9b3d662..790aab4 100644
--- a/package-lock.json
+++ b/package-lock.json
@@ -395,6 +395,7 @@
       "resolved": "https://registry.npmjs.org/express/-/express-5.2.1.tgz",
       "integrity": "sha512-hIS4idWWai69NezIdRt2xFVofaF4j+6INOpJlVOLDO8zXGpUVEVzIYk12UUi2JzjEzWL3IOAxcTubgz9Po0yXw==",
       "license": "MIT",
+      "peer": true,
       "dependencies": {
         "accepts": "^2.0.0",
         "body-parser": "^2.2.1",
@@ -1158,6 +1159,7 @@
       "resolved": "https://registry.npmjs.org/zod/-/zod-4.3.6.tgz",
       "integrity": "sha512-rftlrkhHZOcjDwkGlnUtZZkvaPHCsDATp4pGpuOOMDaTdDDXF91wuVDJoWoPsKX/3YPQ5fHuF3STjcYyKr+Qhg==",
       "license": "MIT",
+      "peer": true,
       "funding": {
         "url": "https://github.com/sponsors/colinhacks"
       }
diff --git a/src/index.ts b/src/index.ts
index 6dd2dfe..30e4020 100644
--- a/src/index.ts
+++ b/src/index.ts
@@ -7,6 +7,10 @@ import { XAPIClient } from './services/xapi.js';
 import { AutonomousAgent } from './services/agent.js';
 import { XMCPServer } from './mcp/server.js';
 
+// Redirect console.log to stderr to prevent conflict with MCP StdioServerTransport
+// which hijacks stdout for protocol messages
+console.log = (...args: unknown[]) => console.error(...args);
+
 async function main() {
   console.log('═══════════════════════════════════════════════════');
   console.log('  MyXstack - Autonomous AI Agent on X (Twitter)');
diff --git a/src/services/agent.ts b/src/services/agent.ts
index 326fb38..2d19839 100644
--- a/src/services/agent.ts
+++ b/src/services/agent.ts
@@ -14,6 +14,7 @@ export class AutonomousAgent {
   private isRunning: boolean = false;
   private pollingIntervalId: NodeJS.Timeout | null = null;
   private isProcessing: boolean = false;
+  private static readonly MAX_PROCESSED_MENTIONS = 10_000;
 
   constructor(config: AgentConfig, xClient: XAPIClient) {
     this.config = config;
@@ -90,10 +91,20 @@ export class AutonomousAgent {
 
       console.log(`\n📬 [${new Date().toLocaleTimeString()}] Found ${newMentions.length} new mention(s)!\n`);
 
-      // Process each mention
-      for (const mention of newMentions) {
+      // Process mentions oldest-first (API returns newest-first) for chronological Set insertion
+      for (const mention of [...newMentions].reverse()) {
         await this.processMention(mention);
         this.processedMentions.add(mention.post.id);
+
+        // Prune oldest entries if Set exceeds limit to prevent unbounded memory growth
+        while (this.processedMentions.size > AutonomousAgent.MAX_PROCESSED_MENTIONS) {
+          const iter = this.processedMentions.values();
+          const { value, done } = iter.next();
+          if (done) {
+            break;
+          }
+          this.processedMentions.delete(value);
+        }
       }
     } catch (error) {
       console.error('❌ Error in processing loop:', error);
diff --git a/src/services/grok.ts b/src/services/grok.ts
index 6b35a50..a3bcf1a 100644
--- a/src/services/grok.ts
+++ b/src/services/grok.ts
@@ -59,7 +59,7 @@ export class GrokService {
         throw new Error(`Grok API error: ${response.status}`);
       }
 
-      const data: any = await response.json();
+      const data = await response.json() as { choices: Array<{ message?: { content?: string } }> };
       const analysisText = data.choices[0]?.message?.content || '';
       
       // Use the mention post ID to reply to the specific post that mentioned the agent
diff --git a/src/services/xapi.ts b/src/services/xapi.ts
index 1f62056..d3fe2f8 100644
--- a/src/services/xapi.ts
+++ b/src/services/xapi.ts
@@ -44,16 +44,27 @@ export class XAPIClient {
         throw new Error('Failed to get user ID from response');
       }
 
-      const mentionsResponse = await this.makeXAPIRequest(
-        `https://api.twitter.com/2/users/${userId}/mentions?max_results=10&expansions=author_id&tweet.fields=created_at,conversation_id,in_reply_to_user_id,referenced_tweets`,
-        'GET'
-      );
+      const params = new URLSearchParams({
+        max_results: '10',
+        expansions: 'author_id',
+        'tweet.fields': 'created_at,conversation_id,in_reply_to_user_id,referenced_tweets',
+      });
+      if (this.lastMentionId) {
+        params.set('since_id', this.lastMentionId);
+      }
+      const mentionsUrl = `https://api.twitter.com/2/users/${userId}/mentions?${params.toString()}`;
+      const mentionsResponse = await this.makeXAPIRequest(mentionsUrl, 'GET');
 
       if (!mentionsResponse || !Array.isArray(mentionsResponse.data)) {
         console.warn('Invalid response from X API (mentions)');
         return [];
       }
 
+      // Track newest mention ID for since_id on next poll (API returns newest first)
+      if (mentionsResponse.data.length > 0) {
+        this.lastMentionId = mentionsResponse.data[0].id;
+      }
+
       return this.parseMentions(mentionsResponse.data);
     } catch (error) {
       console.error('Error fetching mentions:', error);
@@ -77,7 +88,17 @@ export class XAPIClient {
         'GET'
       );
 
-      return this.parseThread(response.data || []);
+      if (!response.data) {
+        console.warn('No data in thread response from X API');
+        return null;
+      }
+
+      if (!Array.isArray(response.data)) {
+        console.warn('Unexpected response shape from X API (thread): data is not an array');
+        return null;
+      }
+
+      return this.parseThread(response.data);
     } catch (error) {
       console.error('Error fetching thread:', error);
       return null;
@@ -127,7 +148,10 @@ export class XAPIClient {
         'GET'
       );
 
-      return (response.data || []).map((tweet: any) => this.parsePost(tweet));
+      if (!Array.isArray(response.data)) {
+        return [];
+      }
+      return response.data.map((tweet: Record<string, unknown>) => this.parsePost(tweet));
     } catch (error) {
       console.error('Error searching tweets:', error);
       return [];
@@ -160,31 +184,31 @@ export class XAPIClient {
     return response.json();
   }
 
-  private parseMentions(tweets: any[]): Mention[] {
+  private parseMentions(tweets: Record<string, unknown>[]): Mention[] {
     return tweets.map((tweet) => ({
       post: this.parsePost(tweet),
-      mentioned_at: new Date(tweet.created_at),
+      mentioned_at: new Date(tweet.created_at as string),
       processed: false,
     }));
   }
 
-  private parsePost(tweet: any): XPost {
+  private parsePost(tweet: Record<string, unknown>): XPost {
     return {
-      id: tweet.id,
-      text: tweet.text,
-      author_id: tweet.author_id,
-      author_username: tweet.username || 'unknown',
-      created_at: tweet.created_at,
-      conversation_id: tweet.conversation_id,
-      in_reply_to_user_id: tweet.in_reply_to_user_id,
-      referenced_tweets: tweet.referenced_tweets,
+      id: tweet.id as string,
+      text: tweet.text as string,
+      author_id: tweet.author_id as string,
+      author_username: (tweet.username as string) || 'unknown',
+      created_at: tweet.created_at as string,
+      conversation_id: tweet.conversation_id as string | undefined,
+      in_reply_to_user_id: tweet.in_reply_to_user_id as string | undefined,
+      referenced_tweets: tweet.referenced_tweets as Array<{ type: string; id: string }> | undefined,
     };
   }
 
-  private parseThread(tweets: any[]): XThread | null {
+  private parseThread(tweets: { created_at: string; [key: string]: unknown }[]): 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()
     );