diff --git a/lib/runner.js b/lib/runner.js
index db53f82..23e9c3d 100644
--- a/lib/runner.js
+++ b/lib/runner.js
@@ -2,13 +2,57 @@
 const fs = require('fs');
 const path = require('path');
 
+// Simple Queue Implementation to prevent concurrency crashes
+class TestQueue {
+  constructor() {
+    this.queue = [];
+    this.running = false;
+  }
+
+  add(task) {
+    return new Promise((resolve, reject) => {
+      this.queue.push({ task, resolve, reject });
+      this.process();
+    });
+  }
+
+  async process() {
+    if (this.running || this.queue.length === 0) return;
+    
+    this.running = true;
+    const { task, resolve, reject } = this.queue.shift();
+
+    try {
+      const result = await task();
+      resolve(result);
+    } catch (error) {
+      reject(error);
+    } finally {
+      this.running = false;
+      this.process(); // Process next item
+    }
+  }
+}
+
+const runnerQueue = new TestQueue();
+
 /**
- * Run a performance test using Lighthouse
+ * Run a performance test using Lighthouse (Serialized)
  * @param {string} url - The URL to test
  * @param {object} options - Configuration options (mobile vs desktop, etc.)
  * @returns {Promise<object>} - Test results
  */
 async function runTest(url, options = {}) {
+  // Wrap the actual test logic in a queue task
+  return runnerQueue.add(async () => {
+    return _executeTest(url, options);
+  });
+}
+
+/**
+ * Internal function to execute the test (NOT exported directly)
+ */
+async function _executeTest(url, options) {
   // Dynamically import dependencies (ESM)
   const { default: lighthouse } = await import('lighthouse');
   const chromeLauncher = await import('chrome-launcher');
@@ -25,10 +69,25 @@ async function runTest(url, options = {}) {
     // Launch Chrome
     console.log('Launching Chrome...');
     const chromePath = process.platform === 'linux' ? '/usr/bin/chromium' : undefined;
+    
+    // Use a unique user data dir to prevent profile locking issues
+    const userDataDir = path.join(os.tmpdir(), `lh-profile-${uuidv4()}`);
+    
+    // Ensure tmp dir exists if likely to crash
+    if (!fs.existsSync(userDataDir)) {
+        fs.mkdirSync(userDataDir, { recursive: true });
+    }
+
     const chrome = await chromeLauncher.launch({
-        chromeFlags: ['--headless', '--no-sandbox', '--disable-setuid-sandbox', '--disable-dev-shm-usage'],
+        chromeFlags: [
+            '--headless', 
+            '--no-sandbox', 
+            '--disable-setuid-sandbox', 
+            '--disable-dev-shm-usage',
+            `--user-data-dir=${userDataDir}` // Unique profile for this run
+        ],
         chromePath: chromePath,
-        port: 0 // Force random port to avoid concurrency issues with default 9222
+        port: 0 // Force random port
     });
   
   // Lighthouse Config
@@ -87,6 +146,13 @@ async function runTest(url, options = {}) {
     fs.writeFileSync(jsonPath, JSON.stringify(summary, null, 2));
 
     await chrome.kill();
+    
+    // Cleanup User Data Dir
+    try {
+        fs.rmSync(userDataDir, { recursive: true, force: true });
+    } catch (e) {
+        console.error('Failed to cleanup temp profile:', e);
+    }
 
     // Insert into Database
     // We expect user_uuid and user_ip to be passed in options, or handle gracefully if not
@@ -120,6 +186,8 @@ async function runTest(url, options = {}) {
 
   } catch (error) {
     if (chrome) await chrome.kill();
+    // Try cleanup again in error case
+    try { fs.rmSync(userDataDir, { recursive: true, force: true }); } catch (e) {}
     throw error;
   }
 }
@@ -160,6 +228,9 @@ async function getHistory(userUuid, userIp) {
   }
 }
 
+// Need os for tmpdir
+const os = require('os');
+
 module.exports = {
   runTest,
   getHistory