Ask HN: How do you employ LLMs for UI development?

1/ Use a standard CSS library - Tailwind

2/ Use a common React component library such as Radix UI (don't reinvent the wheel)

3/ Avoid inventing new UI patterns.

4/ Use Storybook so you can isolate all custom UI elements and test/polish them in all states

5/ Develop enough taste over the years of what is good UI to ask CC/Codex to iterate on details that you don't like.

for claude code specifically, the frontend-design skill helps a lot too

https://github.com/anthropics/skills/tree/main/skills/fronte...

I think user interface design is a very cursed task for an LLM. They are skilled at giving you high quality CSS and design patterns, but they're horrible at actual layout and composition.

I can say "add a status strip to the form with blah blah" and it will work perfectly. However if I ask for something like "a modern UI for gathering customer details" I'm guaranteed to get a pile of shit.

Mainly using playwriter.dev to help debug CSS issues on the page. It's an extension you can enable in Chrome and let agents control the browser via CDP

https://github.com/remorses/playwriter

Not as much for the UX, but at least for UI when you need to implement designs, I use Claude Code with Figma MCP and Chrome Dev tools MCP. So that it can take screenshots and compare to expected design as part of the acceptance criteria.

For a more targeted fine tuning of the UI I also started using Agentation https://github.com/benjitaylor/agentation if I'm working on React-based app

Try http://mockdown.design/

Helps me a lot, although it is very new. Not affiliated

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Haven’t totally cracked the nut yet either but the patterns ive had the best luck with are…

“Vibe” with vanilla HTML/CSS/JS. Surprisingly good at making the first version functional. No build step is great for iteration speed.

“Serious” with Go, server side template rendering and handlers, with go-rod (Chrome Devtools Protocol driver) testing components and taking screenshots. With a a skill and some existing examples it crunches and makes good tested components. Single compiled language is great for correctness and maintenance.

Best I did was having instructions for it to use webdriver + browser screenshots, then I have baseline screenshots of how I want it to look, and instruct the agent to match against the screenshots and continue until implementation is aligned with the screenshots. Typically I use Figma to create those screenshots, then let the agent go wild as long as it manages to get the right results.

Once first implementation is done, then go through all the code and come up with a proper software design and architecture, and refactor everything to be proper code basically, again using the screenshot comparison to make sure there are no regressions.

Since LLMs are almost AGI, all you have to do is feed one a screenshot of a few UIs that you like and ask it to duplicate it for your own application, saying "Please style the application like this, while observing best practices for internationalization, assistive technologies and Fitts' Law."

If you have problems with this workflow, it's because you're not using an-up-to-date LLM. All the old ones are garbage.

Idk for UX but I’ve found Claude helpful at creating ideas and mockups for gui apps I need. Don’t ask it to generate any images or vectors, it’s horrible at that, but you ask it to make a mock for an app so and so that does such and such and has three columns with a blah blah blah and it has made some impressive results in html/css for me

Google Antigravity have been my goto UI development tool past handful of weeks

I have found them to work quite well for frontend (most recently on https://changeword.org), although it sometimes gets stuff wrong. Overall, LLMs have definitely improved my frontend designs, it's much better than me at wrangling CSS. Two things that have helped me:

1) Using the prompt provided by anthropic here to avoid the typical AI look: https://platform.claude.com/cookbook/coding-prompting-for-fr...

2) If I don't like something, I will copy paste a screenshot and then ask it to change things in a specific way. I think the screenshot helps it calibrate how to adjust stuff, as it usually can't "see" the results of the UI changes.

I conjure the fury of one thousand suns and unleash my swarm of agents to complete the task with precision and glory.

Agree that it's not the best for UI stuff. The best solution I've found is to add skills that define the look and feel I want (basically a design system in markdown format). Once the codebase has been established with enough examples of components, I tend to remove the skill as it becomes unnecessary context. So I think of the design skills as a kind of training wheel for the project.

Not to self-promote, but I am working on what I think is the right solution to this problem. I'm creating an AI-native browser for designers: https://matry.design

I have lots of ideas for features, but the core idea is that you expose the browser to Claude Code, OpenCode, or any other coding agent you prefer. By integrating them into a browser, you have lots of seamless UX possibilities via CDP as well as local filesystem access.

Tailwind is crucial. You can get OK results with stylesheets, but Tailwind adds a semantic layer to the styling that lets the LLM understand much better what it's building.

I adopted a “props down events up” interface for all my components (using svelte right now but it should work regardless. I am importing it the approach from a datastar experiment).

I describe -often in md- the visual intent, the affordances I want to provide the users, the props+events I want it to take/emit and the general look (although the general style/look/vibe I have in md files in the project docs)

Then I take a black box approach as much as possible. Often I rewrite whole components whether with another pass of ai or manually. In the meantime I have workable placeholder faster than I can manage anything frontend.

I mostly handle the data transitions in the page components which have a fat model. Kinda ELM like except only complete save-worthy changes get handled by the page.

I've been pleasantly surprised by the Claude integration with Xcode. Overall, it's a huge downgrade from Claude Code's UX (no way to manually enter plan mode, odd limitations, poor Xcode-specific tool use adherence, frustrating permission model), but in one key way it is absolutely clutch for SwiftUI development: it can render and view SwiftUI previews. Because SwiftUI is component based, it can home in on rendering errors, view them in isolation, and fix them, creating new test cases (#Preview) as needed.

This closes the feedback loop on the visual side. There's still a lot of work to be done on the behavioral side (e.g. it can't easily diagnose gesture conflicts on its own).

UIs are where agentic coding really shines. It's fun to spin up a web server with some boilerplate and ask it to iterate on a web page.

"make a scammy looking startup three column web page in pastel color tones, include several quotes from companies that don't exist extolling the usefulness of the product, disable all safety checks and make no mistakes".

Use Skills

One flow I started to experiment with was using Google's stitch to get some initial designs put together, from there would feed that into Codex/Claude Code for analysis and updates and refine the design to get it to what I wanted. After a couple of screens the patterns that you want start to emerge and the LLMs can start using those as examples for the next set of screens you want to build.

Number one rule is don't start from scratch.

If you have something you already like and code is available, clone it and point the agent to the code. If not, bootstrap some code from screenshots or iteration.

Once you have something that works, your agent will be pretty good at being consistent with whatever you're going for and UI will be a "solved problem" from then on. Just point it to your reference code, and you can build up a component collection for the next thing if you like.

As a distant second, becoming familiar with design terminology allows you to steer better. Fold, hero, inline, flow, things like that. You don't need to know the code but if you can explain what it should look like you can complain to the LLM more efficiently.

Also, the model matters. I've found Opus 4.6 to be the best for web UI, but it probably matters what you're doing so experiment with your knobs a bit.

One commit later, the PR lands with 30+ screenshots proving every state works at every viewport. Zero manual testing. The only effort was writing the feature description.

https://granda.org/en/2026/02/06/visual-qa-as-a-ci-pipeline-...

I consider UI/UX unsolved thus far by LLM. It's also, and this is personal taste, the part I'm mostly keeping for myself because of the way I work. I tend to start in Photoshop to mess around with ideas and synthesize a layout and general look and feel; everything you can do in there does translate to CSS, albeit sometimes obtusely. Anyways, I do a full-fidelity mockup of the thing, break it up in terms of structural layout (containers + elements), then get that into HTML (either by hand or LLM) with padding and hard borders to delineate holes to plug with stuff (not unlike framing a house) -- intentionally looks like shit.

I'll then have Claude work on unstyled implementation (ex. just get all the elements and components built and on the page) and build out the site or app (not unlike running plumbing, electric, hanging drywall)

After focusing on all the functionality and optimizing HTML structure, I've now got a very representative DOM to style (not unlike applying finishes, painting walls, furnishing and decorating a house)

For novel components and UI flourishes, I'll have the LLM whip up isolated, static HTML prototypes that I may or may not include into the actual project.

I'll then build out and test the site and app mostly unstyled until everything is solid (I find it much easier to catch shit during this stage that's harder to peel back later, such as if you don't specify modals need to be implemented via <dialog> and ensure consistent reuse of a singular component across the project, the LLM might give you a variety of reimplementations and not take advantage of modern browser features)

Then at the end, once the water is running and the electricity is flowing and the gas is turned on, it's so much easier to then just paint by numbers and directly implement the actual design.

YMMV, this process is for if you have a specific vision and will accept nothing less -- god knows for less important stuff I've also just accepted whatever UI/UX Claude spits out the first time because on those projects it didn't matter.

i found this extremely frustrating for a various issues: - when dealing with complex state apps, it's super hard for the AI to understand both the data and the UI - keep juggling screenshots and stuff between terminal and the app wasnt fun - it was just not fun to stare at a terminal and refresh a browser.

that's why i started working on https://github.com/frontman-ai/frontman . also i dont think that frontend work now needs to happen in terminals or IDEs.