Generate a project with the builder

Enterprise

Create an Arena project by describing what you want and answering the builder’s questions.

Prerequisites

The builder installed in the workspace and its AgentRuntime in phase Running. See Install the Arena builder. If it is missing, the page shows the helm install command, and if it is not Running, the page shows its conditions.
Editor access to the workspace.

Generate the project

Open Projects, select New project, then select Generate with AI.
Enter a Project name, describe what you want in What do you want to build?, and select Start building. The dashboard creates an empty project.
Wait for the status pill beside the conversation to read Connected. The builder reads your description and the workspace’s Ready Providers (names, types and models, never credentials) and binds the project to them. With no Ready Providers, it leaves the bindings for you to fill in.
Answer the builder’s questions. They appear as cards in the conversation: pick an option or type your own answer. A question you leave unanswered expires with the turn.
Review the brief in the panel beside the conversation. It has the sections Goal, Behaviour, Scenarios, Evals, Tools and Bindings, and marks the items that changed after each update. Ask for changes in the conversation until the brief is right.
Select Build under the brief, which appears once the builder has published one. The builder writes nothing to the project until you do. It then writes the project into the sandbox, validates it and runs it, which can take a few minutes. After a build, a later revision of the brief turns the button into Build changes.
When the build finishes, select Open in editor to review the project and try it. The editor reads the project again at the end of every turn, so it opens on the builder’s latest files.

To keep working on an existing project with the builder, see Edit a project with the builder.

Verify

The status pill beside the conversation shows Connected once the sandbox is bound, and Building or Working while a turn runs. While the sandbox comes up, the pill shows the state of its SandboxClaim:

Pill	Claim state
Waiting for a sandbox slot	`Queued`: the builder already has `maxConcurrent` sandboxes bound. The claim waits for one to be released
Waiting for the workspace’s storage	`Pending` with reason `WaitingForStorage`
Starting the sandbox	`Pending`: the sandbox pod is being created and started
Sandbox failed: `<reason>`	`Failed`. A failed claim is never retried
Sandbox released	The claim was deleted: its conversation ended `sandbox.mountReleaseGrace` (5m) ago, or it sat unused for `sandbox.idleTimeout`

A reconnect resumes the same session and its sandbox. If the sandbox was released, select Bring it back. Your next message reopens the session and recreates the sandbox on the project, with the files as you left them; only the old sandbox’s caches are gone.

Troubleshooting

The page shows “This workspace has no content storage”

The claim failed with NoWorkspaceStorage: the namespace has no workspace-<namespace>-content PVC. Enable storage on the Workspace, then start again.

The page shows “The builder’s sandbox could not start”

The claim exists and failed. The message carries the reason, for example an image that cannot be pulled. A failed claim is never retried, so select Try again to start a new session with a new claim.

The pill stays on “Waiting for a sandbox slot”

Every sandbox the builder may bind is in use. The reaper releases idle ones after sandbox.idleTimeout. To serve more people at once, raise the chart’s sandbox.maxConcurrent (default 4).

The builder stops with “The builder ran out of steps”

The builder used its tool-call rounds for one turn (agent.maxToolRounds). Everything it wrote is saved. Send a message such as “carry on” to continue.

Other sandbox errors

For MountNotGranted, ClaimPolicySettling, UnknownMountRole, InvalidMountRole and “You cannot start a builder sandbox here”, see Install the Arena builder.