Why vibe coded apps look generic, and how a design system prompt fixes it

Vibe coded apps look generic because the prompt describes what the app does and says nothing about how it should look, so the builder fills the gap with its defaults. The fix is a design decision made before the first build, not a polish pass after. Lovable's own prompting best practices put it plainly: "Your visual language is a foundation, not a polish layer."

Where does the generic look come from?

An AI app builder is trained to produce something that works for the average request. When your prompt says "a booking app for a bike repair shop with a calendar and a customer list", it has four decisions to make that you did not specify: palette, typography, layout and component style. It picks the safest answer for each, which is the same safe answer it gave the last thousand people.

Three habits make it worse. Prompts that list features and pages without describing a feel. Placeholder copy, which gives the model nothing to design around. And no visual reference at all, so there is nothing to pull the output away from the average. Lovable's documentation encourages style words early in prompts "for cohesive designs that avoid the default-UI look", which tells you the default look is a known outcome, not bad luck.

Is looking generic actually the problem?

Not entirely, and it helps to be precise about this before you redesign anything. Javier Bargas-Avila's 2012 post on the Google Research blog reports that users form an aesthetic judgment of a website in between 17 and 50 milliseconds, and that "users strongly prefer website designs that look both simple (low complexity) and familiar (high prototypicality)."

Familiar is good. A booking page that looks like a booking page is easier to use than a clever one. The problem with a typical vibe coded app is sameness, not familiarity: it looks like every other AI-built app, with nothing that signals who it is for or why anyone should trust it. The goal is familiar structure with a specific identity.

Why is "fix the design later" such an expensive mistake?

Every screen the builder generates inherits whatever visual decisions exist at that moment. Decide the look after ten screens exist and you are restyling ten screens, often one prompt at a time, and each restyle risks breaking logic that was working. Lovable's guide How to build a real product with Lovable says the same: "If you leave it for later, you will be fighting a default look across the whole app."

For a PM this is also a stakeholder problem. A prototype that looks like a template gets feedback about the template. A prototype that looks deliberate gets feedback about the product, which is the feedback you wanted.

How do you turn a reference into a design system prompt?

The workflow takes about an hour and runs before you open the builder. Here it is with the bike repair shop booking app as the example.

1. Pick two or three references, not ten. Choose real products whose feel matches your users: for the bike shop, a friendly local-services app and a clean scheduling tool. Screenshots of real apps work better than abstract mood boards, because they show components in use.
2. Write one sentence about the feel. "Practical and warm, like a workshop with good lighting: nothing corporate, nothing cute." That sentence will anchor every later decision.
3. Ask an LLM to extract a spec. Attach the screenshots to Claude, ChatGPT or Gemini and ask for colours with hex values and roles, a type scale with font names, spacing and radius values, shadow style, and rules for buttons, cards, forms and empty states. Ask it to list five things the design never does.
4. Edit the spec down. Check every hex value and font name against the screenshots, remove anything you cannot justify, and cut it to a page.
5. Feed it to the builder twice. Put the spec in your first prompt, and save it to project knowledge so later prompts inherit it without you pasting it again.
6. Test it on one real screen first. Build the booking confirmation screen with real copy, adjust the spec, and only then build the rest.

What should the design spec contain?

A useful spec is short and specific. A long one gets partly ignored. For the bike shop app, it looks like this:

Section	What to write	Example line
Feel	One sentence, plus three style words	"Practical and warm. Style words: grounded, clear, friendly."
Colour	Four to six colours with a role each	"Primary hex 1F5F4A for main actions only; background hex FAF7F2."
Typography	Two fonts at most, with sizes	"Headings in a rounded sans at 28/22/18px; body 16px."
Spacing and shape	A spacing scale and one radius	"8px scale; 12px radius on cards and buttons."
Components	Rules for the four you use most	"One primary button per screen; forms in a single column."
Never	Five explicit bans	"No gradients, no stock photos of people, no icon-only buttons."

Lovable's documentation describes style words such as "minimal", "playful" or "premium" as meaningfully changing typography, spacing, shadow, border radius and colour, and its prompt library carries a full reference of 20 style directions with their keywords. Your "Feel" row is where those words go.

How do Lovable's built-in design tools fit in?

Lovable now shows design options before it builds. According to its design guidance documentation, a first message that asks for any UI makes Lovable show three design directions by default, rendered as lightweight previews you can compare side by side and refine up to six times before submitting one. It builds directly only when your prompt already commits to a concrete visual direction.

The two approaches work together. Without a spec, the three directions are three variations on defaults. With your spec in the first prompt, Lovable can build straight to your direction, and you can still ask for three variations of a single section, such as the hero or a pricing card, when you want options.

When is a design system prompt not worth the hour?

For a throwaway experiment that only you will see, skip it. The point of a quick test is to learn whether the flow works, and the default look is fine for that. The same goes for internal tools where the only users are two teammates who care about speed, not polish.

The hour pays back once anyone else sees the app: a stakeholder demo, a usability test, or a first real customer. People judge a product by its look before they read a word, and a generic look invites generic feedback. For the full build sequence after the design is set, see how to build a prototype with Lovable; for how Lovable, Bolt and v0 differ on design output, see Lovable vs Bolt vs v0; and if you only need screens, not a working app, AI wireframe generators for PMs is the lighter option.

Where can you practise building with a design system?

Builders Camp's Building with Lovable bootcamp is a 2-week program with 3 live sessions, directed by Ricardo Luiz, in the Vibe Coding Expert Track. Its published topics include the PM Prompting Framework, visual editing and rapid iteration with Lovable's Visual Editor, Supabase integration, and deployment and branding with custom domains. Its practical challenge is rated beginner, and the bootcamp states that no coding is required. See the Building with Lovable bootcamp for dates and format.