---
category: reference
tags: [infrastructure, proxmox, vps]
last_updated: 2026-03-15
confidence: high
---

# Proxmox CPU Type Issue

## Problem

The robot.wtf VM uses the default `kvm64` CPU type in Proxmox, which doesn't expose SSE4.1, SSE4.2, or POPCNT flags. numpy 2.4+ requires these (X86_V2 baseline) and refuses to import.

## Current workaround

`numpy<2.4.0` pinned in `requirements.txt`. This works but freezes numpy on an older version.

## Proper fix

Change the Proxmox VM CPU type from `kvm64` to `host`. This passes through the physical host's CPU features to the guest. Requires a VM reboot.

**Tradeoff:** CPU type `host` breaks Proxmox live migration between hosts with different CPUs. If this VM doesn't need live migration (it doesn't currently), `host` is the better choice.

**To apply:** In Proxmox UI -> VM -> Hardware -> Processor -> Type -> `host`. Or edit `/etc/pve/qemu-server/{vmid}.conf` and set `cpu: host`. Then reboot the VM.

After changing, the numpy pin can be removed from `requirements.txt`.