feat: integrate mesa-2404 content snap for Vulkan support and add gpu-device selection

   Use the mesa-2404 content snap to provide Vulkan ICDs and Mesa GPU
   drivers instead of staging libvulkan1 directly. This ensures the Vulkan
   loader can discover driver JSON files inside the snap, fixing Vulkan
   initialization failures.

   Add a gpu-device snap setting (nvidia, intel, amd) that filters Vulkan
   ICDs via VK_LOADER_DRIVERS_SELECT, allowing users on multi-GPU systems
   to target a specific GPU (e.g. discrete NVIDIA over integrated Intel).

Author: kenvandine

README.md

@@ -35,6 +35,16 @@ The snap automatically detects your GPU and selects the best backend:
 - **AMD GPUs** - Uses ROCm for optimal performance
 - **Other GPUs** - Uses Vulkan
 
+### GPU Drivers (Vulkan)
+
+Vulkan support is provided by the `mesa-2404` content snap, which is installed
+automatically. If it isn't connected, connect it manually:
+
+```bash
+sudo snap connect lemonade-server:gpu-2404 mesa-2404:gpu-2404
+sudo snap restart lemonade-server.daemon
+```
+
 ### Enable ROCm Support (AMD GPUs)
 
 For ROCm GPU acceleration on AMD hardware, connect the `process-control` interface:
@@ -113,6 +123,10 @@ sudo snap set lemonade-server ctx-size=32768
 
 # Set optional llamacpp-args
 sudo snap set lemonade-server llamacpp-args="--no-mmap --flash-attn on"
+
+# Select a specific GPU for Vulkan (default: auto-detect all)
+# Useful on multi-GPU systems to target a discrete GPU
+sudo snap set lemonade-server gpu-device=nvidia
 ```
 
 Changes take effect after the service restarts automatically.
@@ -124,6 +138,7 @@ Changes take effect after the service restarts automatically.
 | `log-level` | info | Log verbosity (debug, info, warn) |
 | `ctx-size` | 4096 | Context window size in tokens |
 | `llamacpp-args` | "" | Optional args to pass to llamacpp-server |
+| `gpu-device` | "" | Vulkan GPU filter: `nvidia`, `intel`, `amd`, or empty for all |
 
 ### Model cache location
 
@@ -180,13 +195,20 @@ sudo journalctl -u snap.lemonade-server.daemon.service --no-pager -n 50
 
 ### GPU not detected
 
-Ensure you have the proper GPU drivers installed:
+Ensure the `gpu-2404` interface is connected:
 ```bash
-# For AMD GPUs
-sudo apt install mesa-vulkan-drivers
+sudo snap connect lemonade-server:gpu-2404 mesa-2404:gpu-2404
+sudo snap restart lemonade-server.daemon
+```
 
-# Check Vulkan support
-vulkaninfo | head -20
+### Vulkan crashes on multi-GPU systems
+
+On systems with multiple GPUs (e.g. Intel integrated + NVIDIA discrete), the
+Vulkan backend may default to the integrated GPU. Use `gpu-device` to select
+the discrete GPU:
+
+```bash
+sudo snap set lemonade-server gpu-device=nvidia
 ```
 
 ### ROCm not working (AMD GPUs)

scripts/lemonade-server-wrapper

@@ -16,6 +16,28 @@ export LEMONADE_LOG_LEVEL=${LEMONADE_LOG_LEVEL:-info}
 export LEMONADE_CTX_SIZE=${LEMONADE_CTX_SIZE:-4096}
 export LEMONADE_LLAMACPP_ARGS=${LEMONADE_LLAMACPP_ARGS:-""}
 
+# GPU device selection via Vulkan loader driver filtering
+LEMONADE_GPU_DEVICE=$(snapctl get gpu-device)
+if [ -n "$LEMONADE_GPU_DEVICE" ]; then
+  case "$LEMONADE_GPU_DEVICE" in
+    nvidia)
+      export VK_LOADER_DRIVERS_SELECT='*nvidia*'
+      echo "[Lemonade Wrapper] GPU device filter: nvidia only" >&2
+      ;;
+    intel)
+      export VK_LOADER_DRIVERS_SELECT='*intel*'
+      echo "[Lemonade Wrapper] GPU device filter: intel only" >&2
+      ;;
+    amd)
+      export VK_LOADER_DRIVERS_SELECT='*radeon*'
+      echo "[Lemonade Wrapper] GPU device filter: amd only" >&2
+      ;;
+    *)
+      echo "[Lemonade Wrapper] Unknown gpu-device value: $LEMONADE_GPU_DEVICE (ignoring)" >&2
+      ;;
+  esac
+fi
+
 BACKEND="vulkan"  # default
 
 # Supported ROCm architectures (must have matching backend binaries)

snap/hooks/install

@@ -6,3 +6,4 @@ snapctl set ip-address=127.0.0.1
 snapctl set log-level=info
 snapctl set ctx-size=4096
 snapctl set llamacpp-args=""
+snapctl set gpu-device=""

snap/snapcraft.yaml

@@ -50,6 +50,12 @@ layout:
   /usr/share/lemonade-server:
     symlink: $SNAP/usr/share/lemonade-server
 
+plugs:
+  gpu-2404:
+    interface: content
+    target: $SNAP/gpu-2404
+    default-provider: mesa-2404
+
 slots:
   # Adds a pseudo content interface to allow clients to express their
   # runtime dependency on lemonade-server
@@ -62,30 +68,35 @@ slots:
 apps:
   metrics:
     command: bin/metrics
+    command-chain: [bin/gpu-2404-wrapper]
     plugs:
       - home
       - removable-media
       - network
       - network-bind
       - opengl
+      - gpu-2404
       - process-control
       - hardware-observe
       - system-observe
   lemonade-server:
     command: usr/bin/lemonade-server
+    command-chain: [bin/gpu-2404-wrapper]
     plugs:
       - home
       - removable-media
       - network
       - network-bind
       - opengl
+      - gpu-2404
       - hardware-observe
       - system-observe
     environment:
-      LD_LIBRARY_PATH: "$SNAP/usr/share/lemonade-server:$SNAP/usr/lib/llamacpp/vulkan:$SNAP/usr/lib/x86_64-linux-gnu:$SNAP/lib/x86_64-linux-gnu:/var/lib/snapd/lib/gl${LD_LIBRARY_PATH:+:$LD_LIBRARY_PATH}"
+      LD_LIBRARY_PATH: "$SNAP/usr/share/lemonade-server:$SNAP_COMMON/cache/lemonade/bin/llamacpp/vulka    n:$SNAP_COMMON/cache/lemonade/bin/whispercpp/vulkan:$SNAP/usr/lib/x86_64-linux-gnu:$SNAP/lib/x86_64-linux-gnu:/var/lib/snapd/lib/gl${LD_LIBRARY_PATH:+:$LD_LIBRARY_PATH}"
       PATH: "$SNAP/usr/bin:$PATH"
   daemon:
     command: bin/lemonade-server-wrapper serve
+    command-chain: [bin/gpu-2404-wrapper]
     daemon: simple
     install-mode: enable
     restart-condition: on-failure
@@ -96,11 +107,12 @@ apps:
       - network
       - network-bind
       - opengl
+      - gpu-2404
       - process-control
       - hardware-observe
       - system-observe
     environment:
-      LD_LIBRARY_PATH: "$SNAP/usr/share/lemonade-server:$SNAP/usr/lib/llamacpp/vulkan:$SNAP/usr/lib/x86_64-linux-gnu:$SNAP/lib/x86_64-linux-gnu:/var/lib/snapd/lib/gl${LD_LIBRARY_PATH:+:$LD_LIBRARY_PATH}"
+      LD_LIBRARY_PATH: "$SNAP/usr/share/lemonade-server:$SNAP_COMMON/cache/lemonade/bin/llamacpp/vulka    n:$SNAP_COMMON/cache/lemonade/bin/whispercpp/vulkan:$SNAP/usr/lib/x86_64-linux-gnu:$SNAP/lib/x86_64-linux-gnu:/var/lib/snapd/lib/gl${LD_LIBRARY_PATH:+:$LD_LIBRARY_PATH}"
       PATH: "$SNAP/usr/bin:$PATH"
       HOME: "$SNAP_COMMON"
       LEMONADE_CACHE_DIR: "$SNAP_COMMON/cache/lemonade"
@@ -119,7 +131,6 @@ parts:
       - unzip # For extracting backends at runtime
       - libdrm-amdgpu1 # SD backends need this at runtime
       - libnuma1 # SD backends need this at runtime
-      - libvulkan1
     override-build: |
       set +u # For unbound variables
       # workaround for build.snapcraft.io builds
@@ -160,6 +171,16 @@ parts:
     override-build: |
       craftctl default
 
+  gpu-snap:
+    after: [lemonade-server, deps]
+    source: https://github.com/canonical/gpu-snap.git
+    plugin: dump
+    override-prime: |
+      craftctl default
+      ${CRAFT_PART_SRC}/bin/gpu-2404-cleanup mesa-2404
+    prime:
+      - bin/gpu-2404-wrapper
+
   scripts:
     plugin: dump
     source: scripts/