## What happened

The `omarchy/sunshine` repo package (2026.516.143833-4) is built **without Sunshine's CUDA support**. On NVIDIA systems the NVENC encoder probe therefore always fails, and Sunshine silently falls back to software x264:

```
Info: Trying encoder [nvenc]
Info: Creating encoder [h264_nvenc]
Error: Couldn't scale frame: Invalid argument
Info: Encoder [nvenc] failed
...
Info: Found H.264 encoder: libx264 [software]
```

Every NVIDIA user on Omarchy gets CPU-only H.264 streaming (no NVENC H.264/HEVC/AV1), with no visible error — just degraded quality and high CPU load.

## Why

Without `SUNSHINE_ENABLE_CUDA`, Sunshine feeds NVENC through its software conversion path (`avcodec_software_encode_device_t::convert`), and that `sws_scale_frame()` call fails with EINVAL against system ffmpeg 9's rewritten swscale. The GPU/driver are fine — `ffmpeg -c:v hevc_nvenc` / `av1_nvenc` work directly on the same machine.

Evidence the package lacks CUDA:

* `strings /usr/bin/sunshine` (omarchy build) contains **no CUDA kernel fatbins** (`sm_*`) and none of Sunshine's `cuda_t`/NvFBC platform code — only ffmpeg's generic `dl_fn->cuda_dl` loader strings.
* The official LizardByte build of the *same version* contains fatbins for `sm_75 sm_80 sm_86 sm_87 sm_89 sm_90 sm_100 sm_103 sm_110 sm_120 sm_121` plus `cuda::cuda_t` / `cuda::nvfbc`. Installing it (AUR `sunshine-bin`) immediately fixes the probe on the same system:

```
Info: Found H.264 encoder: h264_nvenc [nvenc]
Info: Found HEVC encoder: hevc_nvenc [nvenc]
Info: Found AV1 encoder: av1_nvenc [nvenc]
```

## Root cause in packaging

The omarchy package appears to rebuild the AUR `sunshine` PKGBUILD (version/pkgrel match exactly). That PKGBUILD defaults to `_use_cuda=detect`, which enables CUDA **only if the `cuda` package is installed on the build machine**, and otherwise silently passes `-DSUNSHINE_ENABLE_CUDA=OFF -DCUDA_FAIL_ON_MISSING=OFF`. The Omarchy build farm evidently doesn't have the CUDA toolkit installed.

## Suggested fix

Install `cuda` on the builder (or set `_use_cuda=true` so the build fails loudly instead of silently degrading). Runtime users don't need the toolkit — the built binary only needs the driver's `libcuda.so.1`.

## Steps to reproduce

1. Omarchy with an NVIDIA GPU (proprietary/open driver installed, working `nvidia-smi`).
2. Install `sunshine` from the omarchy repo, start the service.
3. Journal shows the probe sequence above ending in `Found H.264 encoder: libx264 [software]`.
4. `strings /usr/bin/sunshine | grep -E 'sm_[0-9]+'` → empty.

## Related

* PR #9011 (default NVIDIA to `capture = kms`) addresses a capture-side issue but won't restore NVENC — the encode-side software-convert path is what fails, regardless of capture backend. Also note `capture = kms` cannot capture Hyprland headless outputs, so it would break virtual-display streaming setups if applied unconditionally.

## System details

* Omarchy 4.0.1, kernel 7.1.9-arch1-2
* GPU: NVIDIA GeForce RTX 5070 Ti, driver 610.57.04 (nvidia-open-dkms), CUDA UMD 13.3
* ffmpeg 2:9.0.1-1, sunshine 2026.516.143833-4 (omarchy repo)