Yes, I do the same with Claude Code. Create an instance on the server for a project and then can create sessions from any device, close my laptop while claude code keeps working, etc. without losing the convenience of dedicated apps.
The key here is that they are _not_ just turning "running codex on a VM" into an API. Their harness is running outside a VM, interacting with a VM when needed. See the diagram in their post. This allows them to scale the agent runs independently from the VMs. That's why they call it "managed Codex harness", it's a different version than what you run.
I do the opposite. I have a Slack bot that communicates with an app on my Mac mini that dispatches agents for tasks. It knows all my projects and also has a scheduler that uses the Herdr API. That way I can have things running on my Claude/Codex subs at home 24/7.
Setting up all my code, environment, context, etc in the cloud on VMs seemed like a lot so instead I send back tasks to my Mac mini(s) that are running at home.
I've been running Hermes inside a remote docker container connected to Slack bound to a Codex account. It's actually pretty great, I prefer this approach for a lot of things. Because it's in a Docker container I have 100% control over the configuration. It may do some crazy stuff, but I know it's not going to start exfiltrating my AWS SSO tokens or SSH keys from my laptop.
But Codex doesn't survive a reboot by default or a laptop going to sleep. Also, herdr is abstracted up a level from the agent, so you actually get more benefit by using Codex with herdr because herdr knows how to operate Codex, and other harnesses. So if you're using multiple Codex instances you can orchestrate them because each harness can talk to the others. You can still interact with Codex running in herdr via remote control (ideally you'd target your "orchestration" Codex instance). It just gives you way more power.
Honestly works extremely well as a personal assistant.
I can see why turning it into an API makes sense, just be aware you might not need to lock yourself in if you can setup your own VMs.