Preview server

The preview server renders your project as a navigable HTML site so you can review content formatting and structure before publishing. It’s a local development tool — nothing is deployed or shared.

Preview is optional. You can author and publish a project without ever running it. It’s most useful when you’re writing content files and want to see how they render, or when you want to check that callouts, images, and markdown formatting look right.

Note

The preview is a rough approximation of the student experience, not a replica of the Student Portal. Layout, styling, and interactive features will differ in the published version.

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Launching the server

Run the preview server in a terminal. Press Ctrl+C to stop it.

uvx genlabz-preview <project_id>

Replace <project_id> with your project’s kebab-case identifier (e.g. s3-static-website). The server starts at http://localhost:8080 and opens in your browser automatically.

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Site structure

The preview server renders five page types:

Route	What it shows
/	Overview page — project title, summary, learning outcomes, difficulty, duration, prerequisites, references, and the resolved overview content
/objectives	Objectives listing — all objectives with their titles and resolved descriptions
/objectives/{id}	Objective detail — the objective’s narrative content and a list of its steps
/objectives/{id}/{step_id}	Step detail — step title, resolved content, and a table of input and output handles
/images/{path}	Static image files from the images/ directory

“Resolved content” means the content file wins over the spec field when both exist. The preview server applies the same resolution rule as the rest of the platform — if content/overview.md exists, the overview page shows that file’s content rather than the overview field from spec.yaml.

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Live reload

The server watches three locations for changes:

• content/ — any content file added, edited, or deleted
• spec.yaml — any change to the project definition
• images/ — any image added or removed

When a watched file changes, the browser reloads automatically. There’s no need to restart the server or manually refresh.

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Callout rendering

The preview server renders the four supported callout types with colour-coded styling:

Callout	Colour
NOTE	Blue
TIP	Green
WARNING	Amber
IMPORTANT	Red

An unrecognised callout type (anything other than NOTE, TIP, WARNING, IMPORTANT) won’t render as a callout — it will appear as plain text. The review_project tool reports an INVALID_CALLOUT_TYPE warning for these cases.

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Stopping the server

Press Ctrl+C in the terminal where the server is running. The server does not run in the background — closing the terminal also stops it.