Proxy generation no longer pegs the machine: - the transcode probes for a hardware H.264 encoder once per process and uses it when present (macOS h264_videotoolbox; Windows/Linux h264_nvenc -> h264_qsv -> h264_amf; libx264 remains the universal fallback and the untouched C++ parity path), with decode-side -hwaccel auto (HEVC 4:2:2 10-bit decodes in hardware on Apple Silicon / RTX 50+ / Intel GPUs and falls back to software cleanly); quality/preset map from the proxy CRF/preset per encoder - the concurrency limit is configurable (ProxyMaxConcurrent, default 1) in the Proxy Settings dialog; auto-generated jobs queue and the next starts when a slot frees. The invariant concurrency x per-job threads <= logical cores / 2 holds by construction (thread budget = half the cores / concurrency, clamped to [1,8], covered by a unit test), and on Unix ffmpeg runs nice -n 10 so the background task never starves the foreground - deleting a footage's proxy also removes it from the auto-generation queue