the Python mlx-metal trick is actually what's crashing it. The mlx.metallib from pip is a different version of MLX than what your Swift binary was built against. It gets past the startup error but then corrupts the GPU memory allocator at inference time → freed pointer was not the last allocation.

Use the version-matched metallib that's already in the repo:

cp LocalPackages/mlx-swift/Source/Cmlx/mlx/mlx/backend/metal/kernels/default.metallib \ .build/release/ .build/release/SwiftLM \ --model mlx-community/Qwen3.5-122B-A10B-4bit \ --stream-experts \ --port 5413 This is the exact metallib that was compiled alongside the Swift code — no version mismatch. Future pre-built releases will bundle it automatically.