The Computer is available on accounts where the feature has been enabled. The Computer tab only appears when it is active for your account.
bash tool your agents can call. It boots
from a base image (Debian + Node + Python) or a custom sandbox image
you define, sleeps automatically after about 30 minutes idle or shortly after
you close the terminal, and wakes on next use.
Open it from the Computer tab. The first time you open the terminal, MCPJam
provisions the machine; after that it resumes in about a second.
Chat attachments
When the previewed host has a computer attached and you are signed in, files you attach in the chat composer are uploaded into the computer’s filesystem at/home/user/attachments/ in addition to being sent inline to the model.
A short note is appended to your message so the model — and any MCP server
running on the computer — can reference the files by path:
This only applies when the host config attaches a personal computer and you
are signed in. Guest sessions and hosts without a computer attached keep the
existing inline-only behavior.
Agent tools
When the Computer tab is open, agents have access to four tools for managing the computer’s lifecycle. These tools are only available while you are on the Computer screen and require a signed-in project.Opening the interactive terminal is a human action and is not available as an
agent tool. The terminal token never appears in the agent transcript.
ui_snapshot_app) while on
the Computer screen.
Sleep and hibernate
Your computer sleeps automatically when it has been idle for about 30 minutes, or shortly after you close the terminal. Sleeping is non-destructive — the disk and memory are snapshotted and restored on wake, so everything you left running is still there. To put the computer to sleep immediately, click Hibernate now in the Computer tab toolbar (only visible when the computer is running). You’ll be asked to confirm, then the terminal closes and the machine hibernates. It wakes automatically the next time you open the terminal or an agent calls thebash
tool.
Sandbox images
A sandbox image is a custom image your computer boots from, defined by a blueprint — a small YAML file:mcpjam cloud images validate for the same check). Build the image, then Use on
computer to boot from it. base / initialize edits need a re-build;
maintenance / knowledge edits take effect at the next chat turn without
one. Images can be kept private to you or shared with the whole project.
Manage them from Change on the image strip.
Image definitions (their blueprints) live in the project database, not on
any one computer’s disk — see Data & persistence.
Scenario sandbox
When a scenario is backed by an environment that has a pinned computer image, thebash tool runs on a per-conversation ephemeral sandbox booted from
that image — not on your personal computer.
How it works
- Per conversation. Each new conversation gets its own isolated machine. Files you write and packages you install in one conversation are not visible to any other conversation.
- Persistent across turns. Within a single conversation, the same sandbox is reused on every turn — you can write a file on turn 1 and read it on turn 5.
- Reaped after idle. If a conversation goes idle for a long time, the sandbox is deleted (not paused). When that happens, you’ll see a notification in the chat: “This conversation’s sandbox was reset after being idle — files and shell state from earlier turns are gone.”
- Image from the environment. All members on the same scenario boot from the same environment image, so the machine is consistent regardless of who is chatting.
- No bash if the image is unavailable. If the environment’s image can’t
boot right now, the scenario loads normally without a
bashtool — no error, and no fallback to your personal computer.
What is unchanged
- Your personal computer is unaffected. Nothing a scenario conversation writes lands on your personal computer, and nothing on your personal computer is visible inside a scenario sandbox.
- Host-backed scenarios (those not tied to an environment) continue to use your personal computer as before.
- Environments with no pinned image also continue to use your personal computer as before.
Browser panel in the Playground
When a host configuration includes a browser tool, the Playground shows a browser panel alongside the chat. Each conversation owns its own browser — switching between chats reattaches the existing browser for that conversation rather than opening a new one or navigating away.Switching conversations
When you switch from one conversation to another, the Playground reconnects to that conversation’s existing browser. The live tabs, page content, unsaved form text, and scroll position are preserved exactly as you left them. No navigation happens on reattach. If the conversation’s browser is not yet running when you open it, the panel shows an Open a browser for this conversation button. The panel also polls in the background so it can attach automatically if the agent starts a browser after the pane is already open.Closing the browser pane
Closing the browser panel stops the viewer — it does not hand control back to the agent. If you held the browser (took manual control), that hold stays parked after you close the pane. The agent remains blocked until you explicitly click Hand back to release control. A parked hold does not keep a metered cloud browser running indefinitely, but it does keep the agent waiting.Browser panel layout
The open and expanded state of the browser panel is tracked per conversation. Opening or closing the panel in one chat does not affect any other chat’s panel state.Data & persistence
Your computer is scratch space, not durable storage. Treat it like a fresh dev box you can rebuild at any time — convenient and fast, but not a place to keep the only copy of anything.What persists
- The filesystem. When your computer sleeps, its entire disk and memory are captured in a pause snapshot and restored on wake, so files you created and tools you installed are still there when you come back.
What wipes it
Each of these rebuilds the machine from its image and deletes every file on the disk:- Reset — restores the computer to a clean copy of its current image. Reset sits on the image strip (next to Change) and is available once the computer is ready or asleep.
- Changing the image — switching to a different environment (or back to the base image) rebuilds from that image.
- Delete — tears the computer down entirely.
- Guest inactivity — computers owned by signed-out (guest) sessions are deleted when idle instead of paused, so their files don’t carry over between sessions. Sign in for a computer that sleeps and resumes with its disk intact.
What survives independently
These live in the project database (Convex), not on the computer’s disk, so they are unaffected by reset, image changes, or deletion:- Cloud skills attached to the project.
- Image blueprints — the definitions of your custom images. Deleting a computer never deletes your sandbox images; you can boot a fresh computer from the same image again.