Fix crash loop: disable keep-alive agents and add unhandledRejection guard

The previous fix (agent .on('error')) doesn't reach individual socket
objects — socket-level parse errors still escaped as uncaught exceptions.

Root fix: disable keepAlive on the HTTP/HTTPS monitoring agents. Without
connection reuse there is no stale connection to trigger "Parse Error:
Data after Connection: close". Monitoring intervals are 60s+ so the lack
of connection pooling has no meaningful performance impact.

Belt-and-suspenders: add process.on('unhandledRejection') alongside the
existing uncaughtException guard to catch any async paths that leak.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_013AQYLFrscmMnzMiXAAANoa

package-lock.json

@@ -122,6 +122,7 @@
       "version": "13.0.3",
       "resolved": "https://registry.npmjs.org/better-sqlite3/-/better-sqlite3-13.0.3.tgz",
       "integrity": "sha512-RbOBxmLBG8uvFUc15X9+9SFemKcQ0WBuISBVkpuiaUB2qblC8UWlHEjdWVoZ8AdhSwmoEgsiXKfopX0CQxaACQ==",
+      "hasInstallScript": true,
       "license": "MIT",
       "dependencies": {
         "node-addon-api": "^8.0.0"

server/index.js

@@ -6,6 +6,26 @@ const http = require('http');
 const { randomUUID } = require('crypto');
 require('dotenv').config();
 
+// Prevent HTTP parser errors (e.g. "Data after Connection: close") and other
+// transient async errors from crashing the process.
+process.on('uncaughtException', (err) => {
+  if (err.code === 'HPE_INVALID_CONSTANT' || (err.message && err.message.includes('Parse Error'))) {
+    console.error('HTTP parse error (swallowed):', err.message);
+    return;
+  }
+  console.error('Uncaught exception:', err);
+  process.exit(1);
+});
+
+process.on('unhandledRejection', (reason) => {
+  const msg = reason instanceof Error ? reason.message : String(reason);
+  if (msg.includes('Parse Error')) {
+    console.error('HTTP parse error (swallowed):', msg);
+    return;
+  }
+  console.error('Unhandled rejection:', reason);
+});
+
 const db = require('./database');
 const scheduler = require('./scheduler');
 const monitorService = require('./monitorService');

server/monitorService.js

@@ -31,9 +31,14 @@ function parseHostPort(urlString, fallbackPort) {
 
 class MonitorService {
   constructor() {
-    // Keep-alive agents for pooled HTTP/S connections
+    // Disable keep-alive to avoid "Parse Error: Data after Connection: close"
-    this.httpAgent = new http.Agent({ keepAlive: true, maxSockets: 50 });
+    // crashes. Keep-alive connection reuse causes the HTTP parser to throw
-    this.httpsAgent = new https.Agent({ keepAlive: true, maxSockets: 50 });
+    // when a monitored server sends extra data after Connection: close — the
+    // socket-level error becomes an uncaught exception that kills the process.
+    // Monitoring checks are infrequent enough that connection pooling provides
+    // no meaningful benefit.
+    this.httpAgent = new http.Agent({ keepAlive: false });
+    this.httpsAgent = new https.Agent({ keepAlive: false });
     
     // Circuit breaker for HTTP checks (5 failures before opening, 60s reset)
     this.httpCircuitBreaker = new CircuitBreaker(5, 60000, this.isTransientError);