Introducing vmux - incredibly fast, stateful cloud sandboxes for coding agents
for the first time you get persistent GPU/CPU sandboxes via Modal/CF backed by Durable Objects to stream logs live, native preview URLs, and attach a real shell
vmux run bundles and runs your code in a long-running cloudflare container and gives you a preview url in under 5s
its a drop-in for uv run - close your laptop, run a tinker training job, come back and reattach via tmux!
a lot of care was built into the bundler, the cli should feel familiar to docker with vmux ps, vmux prune
for agents specifically - vmux exec --create --gpu H100 "pip install torch && python train.py" spins up a Modal sandbox and runs a command in one step
every consecutive call via vmux exec with the job id calls the same sandbox and with vmux claude install claude /codex gets a skill that lets them quickly grep logs/send commands - combined with a gpu container you can start training models extremely quicky just by saying "train nanogpt on a h100 with vmux" and everything just works with modal typically booting up a GPU under 10 seconds
the key insight is that every session is a Durable Object that holds canonical state, a small log ring buffer to hold logs in memory, and a proxy that elegantly proxies between start/stop/failed state for jobs that want a token-gated preview URL
i made it mosstly to unify modal/cloudflare sandboxes for claude code/codex/myself