fix: Steam Deck/Ubuntu crash - use system libzstd.so

The bundled libzstd.so is incompatible with glibc 2.41's stricter heap
validation, causing "free(): invalid pointer" crashes.

Solution: Automatically replace bundled libzstd.so with system version
on Linux. The launcher detects and symlinks to /usr/lib/libzstd.so.1.

- Auto-detect system libzstd at common paths (Arch, Debian, Fedora)
- Backup bundled version as libzstd.so.bundled
- Create symlink to system version
- Add HYTALE_NO_LIBZSTD_FIX=1 to disable if needed

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

README.md

@@ -7,6 +7,7 @@
   <p><small>An unofficial cross-platform launcher for Hytale with automatic updates and multiplayer support (all OS supported)</small></p>
 </header>
 
+![GitHub Downloads](https://img.shields.io/github/downloads/amiayweb/Hytale-F2P/total?style=for-the-badge)
 ![Version](https://img.shields.io/badge/Version-2.1.1-green?style=for-the-badge)
 ![Platform](https://img.shields.io/badge/Platform-Windows%20%7C%20macOS%20%7C%20Linux-orange?style=for-the-badge)
 ![License](https://img.shields.io/badge/License-Educational-blue?style=for-the-badge)
@@ -160,10 +161,13 @@
 <p id="fn2"><sup>Note 2</sup> Using Discrete/Dedicated GPU (dGPU) must have 8 GB RAM minimum.</p>
 <p id="fn3"><sup>Note 3</sup> Using Integrated GPU (dGPU) must have 12 GB RAM minimum.</p>
 
+> [!WARNING]
+> Our launcher has **not yet** supported Offline Mode (playing Hytale without internet).
+> We will surely add the feature as soon as possible. Kindly wait for the update.
 
+---
 
 ### 🪟 Windows Prequisites
-* **
 * **Java JDK 25:**
   * [Oracle](https://www.oracle.com/java/technologies/downloads/#jdk25-windows), **no** support for Windows ARM64 in both version 25 and 21.
   * [Adoptium](https://adoptium.net/temurin/releases/?version=25), has Windows ARM64 support in version 21 only.
@@ -178,8 +182,8 @@
 > [!WARNING]
 > Ubuntu-based Distro like ZorinOS or Pop!_OS or Linux Mint would encounter issues due to UbuntuLTS environment, [check this Discord post](https://discord.com/channels/1462260103951421493/1463662398501027973).
 
-* Make sure you have already installed newest **GPU driver**, consult your distro docs or wiki.
-
+* Make sure you have already installed newest **GPU driver** especially proprietary NVIDIA, consult your distro docs or wiki.
+  * Also make sure that your GPU can be connected to EGL, try checking it first (again, consult your distro docs or wiki) before installing Hytale game via our launcher.
 * Install `libpng` package to avoid SDL3_Image error:
   * `libpng16-16 libpng-dev` for Ubuntu/Debian-based Distro
   * `libpng libpng-devel` for Fedora/RHEL-based Distro
@@ -197,6 +201,10 @@
     * Click **More info**.
     * Click **Run anyway**.
 4. **Launch:** Once installed, you can launch the app directly from your Desktop or the Start menu.
+5. **Whitelist in Windows Firewall to Avoid "Server Failed to Boot" Error** [#192](https://github.com/amiayweb/Hytale-F2P/issues/192#issuecomment-3803042908)
+    * Open the Windows Start Menu and search for `Allow an app through Windows Firewall`
+    * Click "Change settings" (you may need Admin privileges) and Locate `HytaleClient.exe` in the list.
+    * Ensure both the Private and Public checkboxes are checked. Click OK to save.
 
 ---
 
@@ -286,7 +294,7 @@ The `.zip` version is useful for users who prefer a portable installation or nee
 ## Dedicated Server
 
 > [!NOTE]
-> If you have already  `HytaleServer.jar` in `HytaleF2P/{release/pre-release}/package/game/latest/Server`, you can use it to host local dedicated server. 
+> If you already have the patched `HytaleServer.jar` in `HytaleF2P/{release/pre-release}/package/game/latest/Server`, you can use it to host local dedicated server. 
 
 > [!TIP]
 > Use services like Playit.gg, Tailscale, Radmin VPN to share UDP connection if setting up router as an admin is not possible.
@@ -295,7 +303,7 @@ The `.zip` version is useful for users who prefer a portable installation or nee
 > `Hytale-F2P-Server.rar` file is needed to set up a server on non-playing hardware (such as VPS/server hosting).
 
 > [!IMPORTANT]
-> See detailed information of setting up a server here: [SERVER.md](SERVER.md)
+> See detailed information of setting up a server here: [SERVER.md](SERVER.md). Download the latest patched JAR, the patched RAR, or the SH/BAT scripts from channel `#open-public-server` in our Discord Server. 
 
 ---
 

backend/managers/gameLauncher.js

@@ -285,6 +285,55 @@ exec "$REAL_JAVA" "\${ARGS[@]}"
    const gpuEnv = setupGpuEnvironment(gpuPreference);
    Object.assign(env, gpuEnv);
 
+  // Linux: Replace bundled libzstd.so with system version to fix glibc 2.41+ crash
+  // The bundled libzstd causes "free(): invalid pointer" on Steam Deck / Ubuntu LTS
+  if (process.platform === 'linux' && process.env.HYTALE_NO_LIBZSTD_FIX !== '1') {
+    const clientDir = path.dirname(clientPath);
+    const bundledLibzstd = path.join(clientDir, 'libzstd.so');
+    const backupLibzstd = path.join(clientDir, 'libzstd.so.bundled');
+
+    // Common system libzstd paths
+    const systemLibzstdPaths = [
+      '/usr/lib/libzstd.so.1',                    // Arch Linux, Steam Deck
+      '/usr/lib/x86_64-linux-gnu/libzstd.so.1',   // Debian/Ubuntu
+      '/usr/lib64/libzstd.so.1'                   // Fedora/RHEL
+    ];
+
+    let systemLibzstd = null;
+    for (const p of systemLibzstdPaths) {
+      if (fs.existsSync(p)) {
+        systemLibzstd = p;
+        break;
+      }
+    }
+
+    if (systemLibzstd && fs.existsSync(bundledLibzstd)) {
+      try {
+        const stats = fs.lstatSync(bundledLibzstd);
+
+        // Only replace if it's not already a symlink to system version
+        if (!stats.isSymbolicLink()) {
+          // Backup bundled version
+          if (!fs.existsSync(backupLibzstd)) {
+            fs.renameSync(bundledLibzstd, backupLibzstd);
+            console.log(`Linux: Backed up bundled libzstd.so`);
+          } else {
+            fs.unlinkSync(bundledLibzstd);
+          }
+
+          // Create symlink to system version
+          fs.symlinkSync(systemLibzstd, bundledLibzstd);
+          console.log(`Linux: Linked libzstd.so to system version (${systemLibzstd}) for glibc 2.41+ compatibility`);
+        } else {
+          const linkTarget = fs.readlinkSync(bundledLibzstd);
+          console.log(`Linux: libzstd.so already linked to ${linkTarget}`);
+        }
+      } catch (libzstdError) {
+        console.warn(`Linux: Could not replace libzstd.so: ${libzstdError.message}`);
+      }
+    }
+  }
+
   try {
     let spawnOptions = {
       stdio: ['ignore', 'pipe', 'pipe'],

docs/STEAMDECK_CRASH_INVESTIGATION.md

@@ -0,0 +1,123 @@
+# Steam Deck / Ubuntu LTS Crash Investigation
+
+## Status: SOLVED
+
+**Last updated:** 2026-01-27
+
+**Solution:** Replace bundled `libzstd.so` with system version.
+
+---
+
+## Problem Summary
+
+The Hytale F2P launcher's client patcher causes crashes on Steam Deck and Ubuntu LTS with the error:
+```
+free(): invalid pointer
+```
+or
+```
+SIGSEGV (Segmentation fault)
+```
+
+The crash occurs after successful authentication, specifically right after "Finished handling RequiredAssets".
+
+**Affected Systems:**
+- Steam Deck (glibc 2.41)
+- Ubuntu LTS
+
+**Working Systems:**
+- macOS
+- Windows
+- Older Arch Linux (glibc < 2.41)
+
+---
+
+## Root Cause
+
+The **bundled `libzstd.so`** in the game client is incompatible with glibc 2.41's stricter heap validation. When the game decompresses assets using this library, it triggers heap corruption detected by glibc 2.41.
+
+The crash occurs in `libzstd.so` during `free()` after "Finished handling RequiredAssets" (asset decompression).
+
+---
+
+## Solution
+
+Replace the bundled `libzstd.so` with the system's `libzstd.so.1`.
+
+### Automatic (Launcher)
+
+The launcher automatically detects and replaces `libzstd.so` on Linux systems. No manual action needed.
+
+### Manual
+
+```bash
+cd ~/.hytalef2p/release/package/game/latest/Client
+
+# Backup bundled version
+mv libzstd.so libzstd.so.bundled
+
+# Link to system version
+# Steam Deck / Arch Linux:
+ln -s /usr/lib/libzstd.so.1 libzstd.so
+
+# Debian / Ubuntu:
+ln -s /usr/lib/x86_64-linux-gnu/libzstd.so.1 libzstd.so
+
+# Fedora / RHEL:
+ln -s /usr/lib64/libzstd.so.1 libzstd.so
+```
+
+### Restore Original
+
+```bash
+cd ~/.hytalef2p/release/package/game/latest/Client
+rm libzstd.so
+mv libzstd.so.bundled libzstd.so
+```
+
+---
+
+## Why This Works
+
+1. The bundled `libzstd.so` was likely compiled with different allocator settings or an older toolchain
+2. glibc 2.41 has stricter heap validation that catches invalid memory operations
+3. The system `libzstd.so.1` is compiled with the system's glibc and uses compatible memory allocation patterns
+4. By using the system library, we avoid the incompatibility entirely
+
+---
+
+## Previous Investigation (for reference)
+
+### What Was Tried Before Finding Solution
+
+| Approach | Result |
+|----------|--------|
+| jemalloc allocator | Worked ~30% of time, not stable |
+| GLIBC_TUNABLES | No effect |
+| taskset (CPU pinning) | Single core too slow |
+| nice/chrt (scheduling) | No effect |
+| Various patching approaches | All crashed |
+
+### Key Insight
+
+The crash was in `libzstd.so`, not in our patched code. The patching just changed timing enough to expose the libzstd incompatibility more frequently.
+
+---
+
+## GDB Stack Trace (Historical)
+
+```
+#0  0x00007ffff7d3f5a4 in ?? () from /usr/lib/libc.so.6
+#1  raise () from /usr/lib/libc.so.6
+#2  abort () from /usr/lib/libc.so.6
+#3-#4  ?? () from /usr/lib/libc.so.6
+#5  free () from /usr/lib/libc.so.6
+#6  ?? () from libzstd.so    <-- CRASH POINT (bundled library)
+#7-#24  HytaleClient code (asset decompression)
+```
+
+---
+
+## Branch
+
+`fix/steamdeck-libzstd`

docs/STEAMDECK_DEBUG_COMMANDS.md

@@ -0,0 +1,65 @@
+# Steam Deck / Linux Crash Fix
+
+## SOLUTION: Use system libzstd
+
+The crash is caused by the bundled `libzstd.so` being incompatible with glibc 2.41's stricter heap validation.
+
+### Automatic Fix
+
+The launcher automatically replaces `libzstd.so` with the system version. No manual action needed.
+
+### Manual Fix
+
+```bash
+cd ~/.hytalef2p/release/package/game/latest/Client
+
+# Backup and replace
+mv libzstd.so libzstd.so.bundled
+ln -s /usr/lib/libzstd.so.1 libzstd.so
+```
+
+### Restore Original
+
+```bash
+cd ~/.hytalef2p/release/package/game/latest/Client
+rm libzstd.so
+mv libzstd.so.bundled libzstd.so
+```
+
+---
+
+## Debug Commands (for troubleshooting)
+
+### Check libzstd Status
+
+```bash
+# Check if symlinked
+ls -la ~/.hytalef2p/release/package/game/latest/Client/libzstd.so
+
+# Find system libzstd
+find /usr/lib -name "libzstd.so*"
+```
+
+### Binary Validation
+
+```bash
+file ~/.hytalef2p/release/package/game/latest/Client/HytaleClient
+ldd ~/.hytalef2p/release/package/game/latest/Client/HytaleClient
+```
+
+### Restore Client Binary
+
+```bash
+cd ~/.hytalef2p/release/package/game/latest/Client
+cp HytaleClient.original HytaleClient
+rm -f HytaleClient.patched_custom
+```
+
+---
+
+## Environment Variables
+
+| Variable | Description | Example |
+|----------|-------------|---------|
+| `HYTALE_AUTH_DOMAIN` | Custom auth domain | `auth.sanasol.ws` |
+| `HYTALE_NO_LIBZSTD_FIX` | Disable libzstd replacement | `1` |