For AI agents: the complete documentation index is available at https://docs.flezise.com/llms.txt, the full documentation bundle is available at https://docs.flezise.com/llms-full.txt, and this page is available as Markdown at https://docs.flezise.com/sandboxes/preview-environments.md.
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  • 26.11

    • Preview environments

    A preview environment is the application the agent just built, running. After implementation the agent brings the software up, verifies it against the running instance, and records the URL on the artifact so you can click through the same result before you accept the work.

    This is a real environment, and it can be a complex one. When the project has a compose file, or was scaffolded from a stack pack that ships one, the whole stack comes up: the app, its database, and its supporting services, with health checks and start ordering between them. A change is verified against the software actually running, with a real database behind it, instead of against code that merely compiles.

    How a preview is created

    After the agent finishes writing code, and before the implementation is finalized, the platform deploys a preview from the working tree. It uses the project's compose file when one exists; otherwise it detects the tech stack, generates a single-service compose file with a build step, and brings that up. The agent cannot skip this step.

    When no deployable stack is detected, the preview is skipped and the implementation proceeds without one.

    Projects scaffolded from a stack pack ship a preview configuration that names the compose file to deploy, so previews for those projects do not depend on stack detection. See Marketplace for what a stack pack provides.

    How the agent verifies against it

    The deploy hands back the URL and the state of every container in the stack. The agent works against that running instance: it checks per-container status and readiness, reads logs from a specific container (the frontend, the backend, the database) when something fails, and runs commands inside a container to diagnose. The browser check that produces the acceptance criteria screenshots opens the preview URL and exercises the app the way you would.

    Opening a preview

    The artifact's properties sidebar shows View Preview when a preview URL was recorded for the implementation. For terminal-based previews (a CLI deliverable has nothing to serve over HTTP), the sidebar shows Open Terminal instead, which opens a terminal session in the preview.

    Redeploying the same feature replaces the running preview; the URL keeps pointing at the latest deploy.

    Lifetime

    A preview is ephemeral. It expires 24 hours after deploy by default, and expired previews are torn down automatically together with their containers.

    Flezise does not host applications. A preview exists to check a change; when it expires, it is gone, and the change itself reaches your environments through the pull request and your own delivery pipeline.

    Next steps

    • Agent sandboxes: the isolated environment where the agent builds the change
    • Runs: where implementation runs and their evidence live
    • Marketplace: stack packs, including their preview configuration