Fusion-Studio-fix-on-fedora-linux.md

Fixing BlackMagic Fusion Studio on Fedora 42 with AMD Graphics

The Problem: Fusion Studio 20 on Fedora 42 fails to start with "undefined symbol: lzma_end" error, and Reactor crashes with segmentation fault when opened due to Mesa/Qt WebEngine conflicts on AMD graphics drivers.

The Solution: Preload the liblzma library and force software rendering for Qt's WebEngine interface while keeping GPU acceleration for Fusion's actual rendering pipeline.

Symptoms You'll See Without This Fix

When launching Fusion Studio, you'll get:

undefined symbol: lzma_end

When opening Reactor from Fusion's menu:

Segmentation fault (core dumped)

This happens because Fusion's bundled FBX plugin can't find liblzma symbols, and Qt WebEngine conflicts with Mesa shader caching.

Step 1: Verify liblzma is Installed

# Check if liblzma exists (should show symlinks)
ls -la /lib64/liblzma*

# Install if missing (usually already present)
sudo dnf install xz-libs xz-devel

Step 2: Create Fusion Launcher Script

The script preloads liblzma and clears corrupted Mesa shader cache before each launch:

# Create the launcher script
sudo tee /usr/local/bin/fusion-clean-start >/dev/null <<'EOF'
#!/bin/bash
# Clear Mesa shader cache that corrupts with software rendering
rm -rf ~/.cache/mesa_shader_cache_db/
exec env LD_PRELOAD=/lib64/liblzma.so.5 LIBGL_ALWAYS_SOFTWARE=1 /opt/BlackmagicDesign/Fusion20/Fusion "$@"
EOF

# Make it executable
sudo chmod +x /usr/local/bin/fusion-clean-start

Note: LIBGL_ALWAYS_SOFTWARE=1 only affects Reactor's Qt WebEngine UI. Fusion's actual 3D rendering and GPU acceleration via OpenCL remains fully hardware-accelerated on your GPU.

Step 3: Update Desktop Launcher

sudo nano /usr/share/applications/com.blackmagicdesign.Fusion20.desktop

Replace the entire file with:

[Desktop Entry]
Actions=Config;Manager;
Comment=The world's most advanced visual effects and motion graphics solution!
DBusActivatable=false
Exec=/usr/local/bin/fusion-clean-start %f
GenericName=Fusion 20
Icon=blackmagic-Fusion20
MimeType=application/x-fusioncomp;
Name=Fusion 20
NoDisplay=false
Path=/opt/BlackmagicDesign/Fusion20
PrefersNonDefaultGPU=false
StartupNotify=true
Terminal=false
Type=Application
Version=1.0

[Desktop Action Config]
Exec=/usr/local/bin/fusion-clean-start -config
Name=Configure Fusion 20

[Desktop Action Manager]
Exec=/usr/local/bin/fusion-clean-start -manager
Name=Fusion 20 Render Manager

Important: Setting DBusActivatable=false is critical - the default true value causes the desktop environment to ignore the custom Exec line and launch Fusion without the necessary environment variables, resulting in the original errors.

Update desktop database:

sudo update-desktop-database
kbuildsycoca6 --noincremental  # KDE Plasma only

Step 4: Verify the Fix Works

# Launch from terminal to verify
/usr/local/bin/fusion-clean-start

# Or use desktop launcher - both should work
# Reactor menu should open without segfaults

Troubleshooting: If Fusion still crashes after multiple launches, manually clear the entire cache with rm -rf ~/.cache/* then restart. The Mesa shader cache will regenerate and should remain stable with the launcher script managing it.