AI Agent Promised Me a Website in One Prompt. It Forgot to Mention the PTSD of Working on a Legacy Codebas

🧠 I Believed the AI Hype — Now I Just Want a Clean Git Diff

By a developer who just wanted help changing a button, not rewriting the universe.

Remember the hype?

“Just write one prompt, and AI will build your whole app!”

Yeah, that was adorable.

Back in early 2024, every AI startup was demoing the same thing:

User: “Build me a pet adoption site.”
AI Agent: “Here’s a full React app. Tailwind? Check. Supabase? Sure. Stripe integration? Why not. Deployed to Vercel, with a puppy licking the screen for extra UX.”

✨ Applause. Standing ovation. Dev Twitter went feral. VCs wrote blank checks like it was OpenAI’s IPO.

Everyone had a “Built with AI in 10 seconds” link in bio.

Then Reality Hit: Welcome to Existing Codebases™

Fast forward to 2025.

You’re not building toy projects anymore. You want the AI to contribute to an actual product. A real one. With users. And deadlines.

You ask your agent:

“Change the button color and move this section into a modal.”

And suddenly:

• Tests fail in files you didn’t even know existed
• Redux state starts talking in Morse code
• useEffect breaks time itself
• AI rewrites the entire design system because it couldn’t parse your className string

AI: “What is this… legacy?”

The truth? These agents were trained in a sandbox. Pristine, utopian codebases written by themselves.

In your company’s repo?

• 2016 jQuery hacks sitting next to 2023 Next.js pages
• Components named CardFinal, CardFinalV2, and CardFinalV2ReallyFinal
• A global state shaped like a Jenga tower
• 7,000 lines of dead code that might still power prod

Asking an AI to “just update the modal” in that soup is like giving a cat a Rubik’s Cube and asking it to deploy on AWS.

“Just Give It Context,” They Said.

So now you’re pasting half the repo into the prompt:

theme.ts  
utils/getColorFromName.ts  
components/DropdownV5/deprecated/index.tsx  
// don’t touch this – it breaks prod

The AI replies confidently:

“I’ve updated the navbar and cleaned up some unused styles.”

You check the git diff.

It deleted the homepage.

Developers in 2025: One Git Commit Away from Madness

We tried. We really did.

But instead of magical productivity, we got:

• Nightmares in zod and zustand
• Refactors of files with 12-year git history
• Commit messages like fix: trying to undo what the AI did
• AI-generated CSS-in-JS… inside a Tailwind project 💀

One poor dev was last seen whispering:

“Why is it using styled-components… in a Tailwind app?”

Harsh Truth: AI Is Great at Starting. Terrible at Fitting In.

AI loves greenfield.

It thrives on:

• New repos
• Atomic design systems
• Perfect TypeScript configs

Ask it to change 1px in a 7-year-old enterprise monolith?

Panic. Panic. Panic.

It’s like onboarding a junior dev who just realized the repo is a monorepo with 42 packages and no docs.

Final Thoughts: Maybe AI Agents Need Therapy

We gave them a chance.

We wanted helpers, not chaos goblins.

All we ask is:

• Don’t delete the Header when we ask to fix the Footer.
• Don’t optimize things we didn’t ask to touch.
• Don’t hallucinate new design systems from thin air.

Maybe the dream isn’t dead — but let’s change the slogan.

Old: “One prompt. Full app.”
New: “One prompt. One PR. Zero survivors.”

Until then, we’ll be here:

• Babysitting our agents
• Writing scripts to fix what the AI broke
• And praying git checkout -f saves our souls 🙏

P.S. If your AI ever says:

“I went ahead and optimized everything.”

RUN.