Run your app and try it
3 minute read · Projects & Git
The preview lets you use the app you are building while its conversation stays close by. Start the project, open the preview, then test the thing you asked the agent to make.
- Start, inspect, stop and restart
- Give the agent reproducible feedback
- Keep background processes with the project
Start, inspect, stop and restart
Open the project and review its detected start command, environment and preview address. Choose Start app, then follow the individual preparation and launch steps. A full-stack app may have both an API process and a frontend process; a running frontend alone can still show failed data requests.
Use Open app to reach the embedded preview. Reload after a change, navigate through the app and reproduce the requested behavior. To stop local work, use the runtime controls for the relevant process. Reopening a prepared project should start its recorded commands again without repeating completed scaffolding.
| Symptom | Check next |
|---|---|
| Preview cannot connect | Whether the start command failed, which port it actually bound to and whether the preview URL matches it. |
| Page loads but data is missing | The API process, request URL, database connection and the response body. |
| Old page remains | Reload the preview, verify the selected project and confirm that the changed frontend is the one serving this URL. |
| Port already in use | Inspect the process using it; do not stop an unrelated service without checking ownership. |
| Preparation failed | Open that step's output and continue from the failure after its cause is fixed. |
Give the agent reproducible feedback
Report what you clicked, what you entered and what happened. “Create article accepted the form, but the item disappeared after reload” lets the agent inspect the write and read paths. Include a preview image when layout is the problem. An image confirms appearance at that moment; saved data and a successful user flow need their own checks.
A project terminal provides interactive command output in the checkout. Keep it distinct from a remote SSH session. Starting the local app is not deployment, and a synchronized conversation does not transfer its running processes to another computer. See checks and publishing before exposing the app outside your machine.
Keep background processes with the project
An app may need an API server, a frontend dev server and a queue worker or WebSocket service. Configure each needed command in the project's runtime/background-process workflow with its working directory and environment. Reuse a suitable running service instead of starting duplicate servers on the same port.
Start the required processes and inspect their individual status and logs. For a queued mail test, verify that both the web app and its worker are running before submitting the form. For live updates, check the WebSocket service as well as the page. Stop a process you own through its control when finished; closing Preview does not necessarily stop a service.
Ask the agent for a bounded diagnosis when a process exits: “Read the worker's recent error and explain why it stopped. Keep the current database and other services unchanged.” A scheduled agent task is different from a persistent worker; it launches a conversation run when due. Local schedules covers their timing, approvals and interruption behavior.
Related guides: checking your app, project configuration.