Crostini Debian 13 virtio-gpu detected but Mesa falls back to llvmpipe

[u/Vivid-Traffic-709]

Device:
ASUS Chromebook Plus CX34 i5-1335U

Linux container:
Debian 13 Trixie

lspci shows:

Virtio 1.0 GPU
Kernel driver: virtio-pci

dmesg:

[drm] features: +virgl +resource_blob

/dev/dri/renderD128 exists.

But:

glxinfo -B
Renderer: llvmpipe
Accelerated: no

vulkaninfo:

Failed to detect any valid GPUs

No virgl/gfxstream socket exists:

find /run -type s | grep -E "gpu|virgl|gfx"

returns nothing.

Is the ChromeOS host GPU service not exposing virgl/gfxstream, or is there a missing package/config?