Show HN: ProofShot – Give AI coding agents eyes to verify the UI they build
92 points - today at 7:46 AM
I use AI agents to build UI features daily. The thing that kept annoying me: the agent writes code but never sees what it actually looks like in the browser. It can’t tell if the layout is broken or if the console is throwing errors.
So I built a CLI that lets the agent open a browser, interact with the page, record what happens, and collect any errors. Then it bundles everything — video, screenshots, logs — into a self-contained HTML file I can review in seconds.
It works with whatever agent you use (Claude Code, Cursor, Codex, etc.) — it’s just shell commands. It's packaged as a skill so your AI coding agent knows exactly how it works. It's built on agent-browser from Vercel Labs which is far better and faster than Playwright MCP.
It’s not a testing framework. The agent doesn’t decide pass/fail. It just gives me the evidence so I don’t have to open the browser myself every time.
Everyone is comparing this to Playwright but it's solving a different problem. Playwright checks structural properties, like does element X exist, is it visible, etc. That's useful but it can't tell you whether the page actually looks right.
I built something similar that takes a screenshot and uses a multi-modal LLM to evaluate it against a design mock. It catches a completely different class of error. The DOM can be structurally perfect and still look nothing like what was intended. Colors wrong, layout shifted, spacing off, components overlapping. No amount of DOM assertions will catch that.
These are two different kinds of gates: structural which are fast and deterministic, and stochastic which are slow but catch things that are completely different. There is very little overlap between the issues, and you want to catch both.
That way I can invest a lot of time getting the mock just right, then let the agents "make it so".
alkonauttoday at 9:32 AM
This would be _extremely_ valuable for desktop dev when you don't have a DOM, no "accessibility" layer to interrogate. Think e.g. a drawing application. You want to test that after the user starts the "draw circle" command and clicks two points, there is actually a circle on the screen. No matter how many abstractions you make over your domain model, rendering you can't actually test that "the user sees a circle". You can verify your drawing contains a circle object. You can verify your renderer was told to draw a circle. But fifty things can go wrong before the user actually agrees he saw a circle (the color was set to transparent, the layer was hidden, the transform was incorrect, the renderer didn't swap buffers, ...).
I've always found screenshots on PRs incredibly helpful as a reviewer. Historically I've had mixed success getting my team to consistently add screenshots to PRs, so this tool would be helpful even for human code.
At work, we've integrated claude code with gitlab issues/merge requests, and we get it to screenshot anything it's done. We could use the same workflow to screenshot (or in this case, host a proofshot bundle of) _any_ open PR. You would just get the agent to check out any PR, get proofshot to play around with it, then add that as a comment. So not automated code reviews, which are tiresome, but more like a helpful comment with more context.
Going to try out proofshot this week, if it works like it does on the landing page it looks great.
jofzartoday at 8:56 AM
I'm going the opposite of everyone else is saying.
This is sick OP based on what's in the document, it looks really useful when you need to quickly fix something and need to validate the changes to make sure nothing has changed in the UI/workflow except what you have asked.
Also looks useful for PR's, have a before and after changed.
malloc2048today at 11:49 AM
I usually ask Claude Code to setup a software stack that can build/run whatever I am working on. Then I let it browse a website or navigate through screens. I also use Playwright to get screenshots of the website I am building. For e.g. apps or whatever application you are building, there should be a way to get screenshots too I guess.
Added benefit is that when Claude navigates and finds a bug, it will either add them to a list for human review or fix it automatically.
Pretty much a loop where building and debugging work together;-)
Once Claude Code
wild_eggtoday at 6:37 PM
seems similar to a couple of simonw's recent tools?
I'm currently experimenting with running a web app "headless" in Node.JS by implementing some of the DOM JS functions myself. Then write mocks for keyboard input, etc. Then have the code agent run the headless client which also starts the tests. In my experience the coding agents are very bad at detecting UX issues, they can however write the tests for me if I explain what's wrong. So I'm the eye's and it's my taste, the agent writes the tests and the code.
boomskatstoday at 9:31 AM
I find the official Chrome DevTools MCP excellent for this. Lighter than Playwright, the loop is shorter, and easy to jam into Electron too.
nunodonatotoday at 10:45 AM
I've been using playwright-cli (not mcp) for this same purpose. It lacks the video feature, I guess. But at least is local and without external dependencies on even more third parties (in your case, vercel). Perhaps you could allow to use a local solution as an alternative as well?
onion2ktoday at 9:26 AM
I use AI agents to build UI features daily. The thing that kept annoying me: the agent writes code but never sees what it actually looks like in the browser. It can’t tell if the layout is broken or if the console is throwing errors.
I give agent either a simple browser or Playwright access to proper browsers to do this. It works quite well, to the point where I can ask Claude to debug GLSL shaders running in WebGL with it.
varispeedtoday at 6:25 PM
I built something like this for native application, so that I could get automated feedback loop for the agent instead of making screenshots manually etc. Problem I found is that AI agent understands nothing of the UI. If you tell it "Make buttons evenly spaced", sure it will space them evenly, but without care for the context they are placed in. You have to describe the image yourself and still you'll find it having hard time understanding what's going on. I very much abandoned the idea of AI driven UI development as it is not there yet. I tried with GPT 5.2. Maybe newer models have improved.
tjwebbnorfolktoday at 6:39 PM
VSCode and Antigravity already do this. What am I missing?
I'd love to see an agent doing work, then launching app on iOS sim or Android emu to visually "use" the app to inspect whether things work as expected or not.
mosselmantoday at 11:23 AM
I use the Claude Chrome extension for this. Works wonderfully. It lets Claude click through features itself, etc.
dbdoskeytoday at 10:09 AM
This is really cool. Have you thought of maybe accessing the screen through accessibility APIs? For Android mobile devices I have a skill I created that accesses the screen xml dump as part of feature development and it seems to work much better than screenshots / videos. Is this scalable to other OS's?
alexovchtoday at 12:15 PM
This is actually interesting. Feels like we’re moving from “generate UI” to “validate UI,” which is a completely different problem. Curious how you handle edge cases where something looks correct but breaks in interaction?
xtiansimontoday at 1:04 PM
Slightly Off-topic of Agentic...
Anyone recommend browser-base instant preview site for web ui design with more artistic/experimental preference?
lastdongtoday at 8:47 AM
This is basically what antigravity (Google’s Windsurf) ships with. Having more options to add this functionality to Open code / Claude code for local models is really awesome. MIT license too!
_aravindctoday at 1:59 PM
This is awesome, does it work with desktop application ?
peter_retieftoday at 10:58 AM
Thanks!
I do share screenshots and paste them manually for front end stuff, nice idea though.
VadimPRtoday at 8:36 AM
Looks nice! Does it work for desktop applications as well, or is this only web dev?
sarrephtoday at 11:35 AM
I am fed up of getting gaslit by coding assistants. "Your AI agent says it's done." really is a problem! Nice packaging here.
I built something similar[0] a few months ago but haven't maintained it because Codex UI and Cursor have _reasonable_ tooling for this themselves now IMO.
That said there is still a way to go, and space for something with more comprehensive interactivity + comparison.
my claude drive his own brave autonomously, even for ui ?
grahammccaintoday at 11:22 AM
This is really useful thank you!
EruditeCoder108today at 9:49 AM
I see
m00dytoday at 9:30 AM
Gemini on Antigravity is already doing this.
Imustaskforhelptoday at 8:32 AM
Great to see this but exe.dev (not sponsored but they are pretty cool and I use them quite often, if they wish to sponsor me that would be awesome haha :-]) actually has this functionality natively built in.
but its great to see some other open source alternatives within this space as well.
dude250711today at 10:43 AM
That is not UI, that's just some web pages with JS.
tanglermantoday at 7:04 PM
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vanyalandtoday at 6:45 PM
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CloakHQtoday at 12:39 PM
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chattermatetoday at 10:44 AM
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zkmontoday at 8:38 AM
Taking screenshots and recording is not quite the same as "seeing". A camera doesn't see things. If the tool can identify issues and improvements to make, by analyzing the screenshot, that's I think useful.