Ephemeral or persistent? Choosing a runtime for your agents

Two models, one decision

Agent infrastructure comes in two flavors. Ephemeral: spin up, run a task, throw it away. Persistent: spin up and keep it alive, with state intact, for as long as you need. Most sandbox platforms are ephemeral by default. The right choice depends on what your agent actually does.

When ephemeral is the right call

Ephemeral shines for stateless, one-shot work:

• Run a single tool call or code snippet.

• Grade one eval and discard it.

• Execute a function and return a result.

If the task has no memory and no follow-up, a disposable sandbox is simple and cheap. Don't pay for persistence you won't use.

When persistence quietly wins

A lot of real agent work isn't one-shot:

• Long-running agents that work for hours or days — research, monitoring, background jobs.

• Stateful workflows where step 12 depends on the filesystem that step 3 created.

• Always-on assistants that need to resume instantly with full context.

Force these onto ephemeral infra and you pay a hidden tax: rebuilding state on every run — re-cloning, re-installing, re-warming. The agent spends its life setting up instead of working.

You shouldn't have to choose up front

The catch with "persistent" is the fear of an always-on bill. But persistence and cost-efficiency aren't opposites. Hibernate an idle agent and its state is preserved while its compute bill drops to near-zero — then it wakes in milliseconds when there's work. You get the memory of persistence with the economics of ephemeral.

How to decide

Ask one question: does this agent need to remember anything between runs? If no, go ephemeral. If yes — and more agents do than you'd think — you want persistence with hibernation, not a sandbox you have to rebuild every time.

agentmachines gives you both: instant and ephemeral when you want it, long-lived and stateful when you need it. Start for free.