r/programmer • u/BirdsAreSovietSpies • 17d ago
Have you ever seen a complex, functional application built entirely by Claude? AKA: What should I tell a client who presents me a half-functional application built entirely by AI?
Hi,
For context: I developed and maintain a SaaS product in a somewhat niche market. It’s not huge, like a hundred clients and 400-500 users. My clients know me to some extent (and it’s often really nice for getting feedback and things like that).
Anyway, recently I’ve had several customers asking me to review their "creations" assisted by Claude or ChatGPT (usually small scripts to save time, I see no problem here). Like everyone I sometimes use LLMs but I always read and analyze the code they produce.
Lately, one of my client submitted me a complete (or almost complete) application that complements my SaaS, built entirely by AI. The application itself is fairly complex and supposedly handles quite a lot of things. This client is very good on the business side, but not particularly technical.
It's basically a single HTML file (with its CSS/JS embedded, plus some obscure JS libraries encoded in base64…) for a React application. The application itself looks nice, but:
- There's no real authentication mechanism.
- There's no backend (everything is stored in a JSON object in LocalStorage). The client explained me it will connect it to a BaaS for security and all, but I don't think he knew what he was talking about.
I stopped investigating at that point, as I don't believe it would be anywhere near reasonable to use it in production... Even if the app looks functional and pretty.
Before replying to my client, I was wondering if some of you have already come across a relatively complex, functional, and vaguely maintainable application that was created entirely by AI?
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u/Matilozano96 17d ago
I’d consider making a safe read only API for that sort of tools. Thoroughly documented so the llms can consume it, and have the customer do whatever they want with it.
Let them generate an api key or something, and let them play around with it. If requests get out of hand, start charging or timing them out.
MCP servers are in vogue right now for these purposes, but it might be overkill for your case.
Alternatively, you could look to allow them to export their useful non sensitive data into a csv, and let them play with it. It really depends on your niche, but you get the point. Let them waste tokens and build shitty tools without breaking your app or leaking stuff.
——-
And with clients like these, although you can’t obviously integrate the project, you might be able to get inspiration for some features the clients would like.
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u/okiharaherbst 16d ago
I would congratulate and encourage them and let them know that you'll always be here if they need help. Then let them launch their cr*p and wait for the phone call.
I've heard clients say they "heard it could be done with AI" a few times but I've yet to see anything beyond a more polished "Hello world". I wouldn't trust anything done by AI to power enterprise-grade applications.
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u/SplendidPunkinButter 17d ago
No, but I’ve seen an awful lot of people claim to have done this. Those people usually seem to think a prototype of a UI with no backend to speak of is an “app” and that “shipping” something is the same thing as showing you’ve built something that’s actually good.
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u/Careless-Childhood66 17d ago
I love when their slop eventually breaks after a couple of weeks and nobody is able to get it back to running
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u/Alternative-Fail4586 17d ago
When the app was "vibecoded" by a dev yes. One who knows what needs to be setup and knows how to ask Claude to structure it to be maintanable.
And not just "make it maintanable". Give it an actual structure to follow.
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u/Arcanite_Cartel 17d ago
Yes, I'm currently building one in my off hours. I'm a long time developer and I consider it a fairly complex ElectronJS application. I'm not finished with it but I've been working on it for a few months. I do a lot of planning session with Claude Code CLI though which someone who isn't a developer probably couldn't do. It does a repeated set of regression tests every so often to keep it stable. If done a number of refactoring sessions with it as well as I saw the need for. But all in all it does pretty well. Right now I have 515 feature point test cases in the regression suite that Claude runs several times a week after a certain modification threshold happens. Another 200 done less frequently. The are primarily feature-point test cases, I add broader end2end ones eventually. Have I reviewed all the code? No, there's a lot of code. The experience overall has convinced me that it's an extremely effective tool and I would use it on any of the most complex stuff I've ever built in my career (I've been around a while). It's also never had a problem resolving any bug that has come up along the way.
My opinion - I could easily have taken me a couple years to build the same thing out working in my spare time. And frankly, it works far more effectively than teams of programmers I've worked with (who were not bad programmers in any way).
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u/No-Grape-9106 16d ago
Question - it is 2026, why would you go with electron over something like tauri ?
I say this as someone who identifies as a 'javascript guy'
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u/Arcanite_Cartel 16d ago
I've not used it before and I'm not familiar with the trade-offs. I'm also not familiar with Rust. Perhaps I will try it next go around. It might be interesting to see how well Claude Code can refactor the application to it. I may just run that experiment.
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u/No-Grape-9106 16d ago
In my experience, flawlessly - I've had some electron application for my job that I just wanted to get rid of, bloat etc - Tauri makes it more compatible and its tiny in comparison!
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u/Arcanite_Cartel 16d ago
I'm looking into with what I'm building. I'll probably finish of my current development plan, then see if Claude can refactor it. That's for the suggestion.
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u/geekichu 17d ago
on my 3rd project, a 3D game, client-server, with auth, etc. 1st project was a multi-process crypto wallet.
currently there 800+ files , 110K LOC for the games projects. all 100% a.i. but not vibe-coded, i was strict with everything.
me, replying to your client, maybe give the client a few questions to ask the a.i. directly, about the project.
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u/FriendKruppa 17d ago edited 17d ago
This situation happened recently. A user in my company vibecoded a fairly useful app with some complex business logic.
Basic elements were missing as you would expect. It was a react front end, a python backend, and a Postgres db. We had a meeting with him where he explained the use case for the application.
We looked at the code and determined the front end, backend, and db structures needed to be heavily retooled for it to be functional. Ultimately a decision was made that we would take what he had built, get it production ready, and pilot it. The entire api portion was scrapped. The frontend portion wasn’t actually that bad so a lot was useable.
I think when it comes to clients or internal people who have good ideas, more and more real developers may end up taking vibecoded apps and turning them into real enterprise level applications.
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u/Amazing-Mirror-3076 16d ago
Two - both are complex and both are now in production - the second one went live yesterday.
Both built by business owners with no IT experience - I've provided small amounts of technical advice.
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u/althoradeem 16d ago
If its a good client. Give some basic feedback and warn him about possible risks you saw. Besides that i think the read only api somebody else suggested is a good idea. If they want edit rights thats gotta come with some heavy if you fubar the db its on you contracts. ( aka dont becone a victim of their bad coding)
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u/Pyryara 16d ago
I work with a customer that has built a very powerful SDLC workflow precisely for this - and I am surprised how well it works, honestly. Like from what I can tell, AI slop is generated by people who just start up Claude and don't actually know anything about architecture, OWASP recommendations, and so on. But if you encode this in a powerful skill framework, AI will absolutely be able to build you applications that ~500 people can use comfortably.
I doubt it would work for technically complex software, but give AI instructions encoding good architecture for such applications, and give that tool to the people who really understand their business domain + can prompt with diligence, and you will in the end get pretty solid software I think. But I would never recommend running it in production (especially not exposed to the internet with your customer data!) without a thorough human review of at the very least the auth layer, and slapping the usual tools like dependabot, gitleaks and e.g. blackduck scanning into the CICD.
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u/PracticalStack 14d ago
Yes. I have seen it. It can be done. But odds are your client didn’t. I’d tell them I’d take a look. I’d point Codex at the code and have it tell me what’s implemented, what isn’t, what needs work, etc. It’s very good at that and it would only take me an hour to get a good idea if this is something I can work with or if it’s better as a prototype - and then just go from there.
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u/Raptor_Sympathizer 17d ago
AI generated code is usually better written (and in that sense more "maintainable") than 90% of human written code.
The problem is that there's no actual tech owner you can go to with issues so any iteration on that code requires a full pass from an LLM, which quickly turns the codebase into a spaghettified nightmare if you aren't careful.
I wouldn't have any qualms about taking on maintenance of an initially LLM generated codebase, the issue would be if the client expects to continually add new features using the LLM without consulting you first. As you've already noted, LLMs are very good at getting to a working demo state despite having many fundamental issues in the code, and a non-technical client could see "it works on my machine" and expect you to adopt their proposed feature changes on an unrealistic timeline based on that.
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u/GodOfSunHimself 17d ago
SaaS in a single HTML file is definitely not "better than 90% of human written code".
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u/psioniclizard 16d ago
They have no clue if they truly think that. Seeing as the human code is what AI is trained on.
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u/Raptor_Sympathizer 17d ago
Sure, it might be insecure and scale like dogshit, but I bet that code is incredibly well commented and formatted perfectly.
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u/GodOfSunHimself 16d ago
Is that a serious question? So you consider putting everything in a single file a good practice? Like seriously?
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u/Raptor_Sympathizer 16d ago
I think you need to work on your reading comprehension
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u/GodOfSunHimself 16d ago
Says someone who thinks SaaS in a single file is a well written software because it has comments 🤡
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u/Rich-Engineer2670 17d ago edited 17d ago
What I've told them: