Disclosure: I work on Gobare, one of the three runtimes below. To keep that from mattering, I quote the other two instead of describing them, and there is a section on where each of us loses, Gobare included. All quotes are from public docs, checked 27 September 2026. Misha.
I read the sandbox docs of three hosted agent runtimes side by side, ours included. In a 30-second demo they look the same. The agent writes code, runs it, shows a result.
The difference is one question the demo never asks:
After the agent stops typing, does its machine still exist?
Perplexity, OpenAI and Gobare give three different answers. None of them is wrong. They are building different things. But if you pick one without checking, you find out an hour into a job, at the step where the work was supposed to land.
This post is the check I wish I had done first.
OpenAI ships two things with similar names. They are not layers of each other.
So "can I use Claude with OpenAI's agents?" has two answers. In the SDK, yes. In the hosted Agents API, the one that gives you a sandbox, non-OpenAI models are on a second-class path.
Everything below is about hosted runtimes: the ones that give you a machine.
Perplexity, on their sandbox tool: "Multiple executions in a single response share the same container: files written and packages installed by an earlier step are still there for a later one."
Between responses, nothing is promised. That is the right design for an answer engine that computes. If you want an answer, paying to keep a machine alive afterwards is waste.
OpenAI, on hosted sandboxes: "If activity and keep-alives stop for an hour, the sandbox can be deleted."
Files you write to /workspace/outputs become immutable artifacts that "remain downloadable after the sandbox expires." The rest of the workspace does not survive. Clean contract: the sandbox is a place to do work, not to keep it.
Gobare, on limits: "A workspace is also d after five minutes with nothing happening, and woken by the next thing you send."
Before the machine is reclaimed, the workspace files are snapshotted. It is best-effort. Git history, installed dependencies and running processes are not in the snapshot, and a workspace over 300MB is skipped.
Side by side:
| Perplexity | OpenAI hosted | Gobare | |
|---|---|---|---|
| Machine lives for | One response | Until an hour with no activity or keep-alives | d after five idle minutes, woken by your next message |
| What survives | Nothing promised between responses | Files in /workspace/outputs , as artifacts |
Workspace files, best-effort snapshot |
| What doesn't | The container | The rest of the workspace | Git history, installed deps, running processes; workspaces over 300MB |
These are not failures of a bad runtime. They are where a correct runtime, picked for the wrong shape of work, gives you a system you cannot finish.
Perplexity publishes a price for the container itself, on their [pricing page](https://docs.perplexity.ai/getting-started/pricing):
"$0.03 per session (≤20-min billing window)"
That is roughly $0.09 an hour for a managed container. It is the clearest public anchor I found for what hosted agent compute costs.
It also explains the product. Perplexity's money is in the search index. For them, the runtime does not need to be profitable, and that sets the floor for everyone else.
previous_response_id./workspace/outputs stays. Non-OpenAI models are second-class on the hosted path.auto_stop_interval=0, or the sandbox stops mid-agent.
Take this list to whichever runtime you are evaluating. Every item comes from a place where these three differ.
Lifetime
State
Workload fit
Control
Not "which runtime is best." Ask:
After my agent stops typing, do I still need the machine?
If no, a per-request container is the honest choice, and you shouldn't pay for more. Perplexity's model is the clean version of that.
If yes, you are choosing between owning the compute yourself and having someone manage its state for you. Both are defensible. Not knowing which one you picked is not.
Full version with every source link: [gobare.dev/blog/agent-runtimes-disagree-on-what-a-session-is](https://gobare.dev/blog/agent-runtimes-disagree-on-what-a-session-is)
If you have run agents in production: which of these questions did you only learn to ask after something broke?