Add debug options and jemalloc support for Linux memory issues

Debug env vars for clientPatcher:
- HYTALE_SKIP_SENTRY_PATCH=1 - Skip sentry URL patch (60->26 chars)
- HYTALE_SKIP_SUBDOMAIN_PATCH=1 - Skip subdomain prefix patches

Game launcher Linux options:
- HYTALE_USE_JEMALLOC=1 - Use jemalloc allocator instead of glibc

This helps isolate which patch causes "free(): invalid pointer"
on Steam Deck and Ubuntu LTS.

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

backend/managers/gameLauncher.js

@@ -285,12 +285,30 @@ exec "$REAL_JAVA" "\${ARGS[@]}"
    const gpuEnv = setupGpuEnvironment(gpuPreference);
    Object.assign(env, gpuEnv);
 
-   // Disable glibc heap validation on Linux to prevent false positive
+   // Linux memory allocator fixes for "free(): invalid pointer" crashes
-   // "free(): invalid pointer" crashes on Steam Deck and Ubuntu LTS
+   // on Steam Deck (glibc 2.41) and Ubuntu LTS
-   // This doesn't hide real bugs - the same binary works on other systems
    if (process.platform === 'linux') {
+     // Option 1: Disable glibc heap validation
      env.MALLOC_CHECK_ = '0';
-     console.log('Linux detected: Setting MALLOC_CHECK_=0 to disable glibc heap validation');
+
+     // Option 2: Try to use jemalloc if available (more robust allocator)
+     // User can set HYTALE_USE_JEMALLOC=1 to enable
+     if (process.env.HYTALE_USE_JEMALLOC === '1') {
+       const jemalloc = require('fs').existsSync('/usr/lib/libjemalloc.so.2')
+         ? '/usr/lib/libjemalloc.so.2'
+         : require('fs').existsSync('/usr/lib/x86_64-linux-gnu/libjemalloc.so.2')
+           ? '/usr/lib/x86_64-linux-gnu/libjemalloc.so.2'
+           : null;
+
+       if (jemalloc) {
+         env.LD_PRELOAD = jemalloc + (env.LD_PRELOAD ? ':' + env.LD_PRELOAD : '');
+         console.log(`Linux: Using jemalloc allocator (${jemalloc})`);
+       } else {
+         console.log('Linux: jemalloc not found, using glibc with MALLOC_CHECK_=0');
+       }
+     } else {
+       console.log('Linux: Using glibc with MALLOC_CHECK_=0 (set HYTALE_USE_JEMALLOC=1 to try jemalloc)');
+     }
    }
 
   try {

backend/utils/clientPatcher.js

@@ -245,6 +245,10 @@ class ClientPatcher {
   /**
    * Apply all domain patches using length-prefixed format
    * This is the main patching method for variable-length domains
+   *
+   * Debug env vars:
+   *   HYTALE_SKIP_SENTRY_PATCH=1 - Skip sentry URL patch (biggest size change)
+   *   HYTALE_SKIP_SUBDOMAIN_PATCH=1 - Skip subdomain prefix patches
    */
   applyDomainPatches(data, domain, protocol = 'https://') {
     let result = Buffer.from(data);
@@ -253,7 +257,10 @@ class ClientPatcher {
 
     console.log(`  Patching strategy: ${strategy.description}`);
 
-    // 1. Patch telemetry/sentry URL
+    // 1. Patch telemetry/sentry URL (skip if debugging)
+    if (process.env.HYTALE_SKIP_SENTRY_PATCH === '1') {
+      console.log(`  Skipping sentry patch (HYTALE_SKIP_SENTRY_PATCH=1)`);
+    } else {
       const oldSentry = 'https://ca900df42fcf57d4dd8401a86ddd7da2@sentry.hytale.com/2';
       const newSentry = `${protocol}t@${domain}/2`;
 
@@ -268,6 +275,7 @@ class ClientPatcher {
         console.log(`    Replaced ${sentryResult.count} sentry occurrence(s)`);
         totalCount += sentryResult.count;
       }
+    }
 
     // 2. Patch main domain (hytale.com -> mainDomain)
     console.log(`  Patching domain: ${ORIGINAL_DOMAIN} -> ${strategy.mainDomain}`);
@@ -282,7 +290,10 @@ class ClientPatcher {
       totalCount += domainResult.count;
     }
 
-    // 3. Patch subdomain prefixes
+    // 3. Patch subdomain prefixes (skip if debugging)
+    if (process.env.HYTALE_SKIP_SUBDOMAIN_PATCH === '1') {
+      console.log(`  Skipping subdomain patches (HYTALE_SKIP_SUBDOMAIN_PATCH=1)`);
+    } else {
       const subdomains = ['https://tools.', 'https://sessions.', 'https://account-data.', 'https://telemetry.'];
       const newSubdomainPrefix = protocol + strategy.subdomainPrefix;
 
@@ -299,6 +310,7 @@ class ClientPatcher {
           totalCount += subResult.count;
         }
       }
+    }
 
     return { buffer: result, count: totalCount };
   }