The phone-agent story is easy to misread as mobile development. The stronger pattern is narrower: a phone can be a control plane for long-running agents whose actual state lives on a workstation or VPS.
That makes the stack practical. A mobile terminal, secure tunnel, and persistent session can let the owner approve, interrupt, inspect logs, or redirect a job without moving the repo and toolchain onto the phone.
The fragile version is ad hoc editing from a tiny screen with no durable session boundary. The useful version keeps tmux, logs, checks, and repository state on the host, then sends small control signals from mobile.
For New Runtime, this matters because agent work increasingly runs longer than one chat turn. The owner interface should be small and reliable; the working environment should be persistent and auditable.