I Fed My Entire Codebase to an AI With Repomix. Here's What I Learned

A journey into the lazy, brilliant, and slightly terrifying world of AI-assisted development

Look, let’s be honest. We’ve all been there. It’s 1 AM, you’re staring at a janky codebase that’s grown more tangled than your headphone cables, and you have a brilliant, desperate idea: “I’ll just ask ChatGPT.” You start copy-pasting files, but by the third one, the AI has the memory of a goldfish and asks, “So, what were we talking about again?” Context window slammed shut. Face, meet palm. I needed a better way to get my AI assistant to understand the beautiful mess I’d created. That’s when I stumbled upon Repomix—a tool that promised to package my entire repository into a single, “AI-friendly” file. The premise is simple, absurd, and undeniably a product of our times: we now need specialized tools just to format our code for our robot overlords. My inner cynic called it a “digital meat grinder.” My inner lazy genius called it a “superpower.” As it turns out, they were both right.

What is This Digital Meat Grinder, Anyway?

At its core, Repomix is a sophisticated file concatenator on steroids. It takes your entire codebase—yes, even that utils.js file with 47 unrelated functions—and smooshes it into one massive XML or Markdown file. But here’s the kicker: it’s actually clever about it.

• Git-Aware: It automatically respects your .gitignore files, so it won’t pack up your node_modules folder or other build artifacts. At least it has the decency to respect your shame.
• Security-Focused: It runs Secretlint to catch accidentally committed API keys. A nice feature for preventing what we’ll politely call “career-limiting moves.”
• Token Counting: It uses tiktoken to tell you exactly how large your codebase is in AI currency, so you know how much money you’re about to burn before you even make the API call.
• AI-Optimized Formats: It defaults to XML because, as Anthropic advises for Claude, structured data is easier for models to parse. It’s like your mom telling you to wear a jacket—annoying, but probably good advice. The most impressive part is its optional compression. Using Tree-sitter, it can perform what I can only describe as code liposuction. It strips out all the implementation details, leaving just the function signatures and class structures.

// Before: Your pride and joy, a 45-line sorting algorithm
const calculateTotal = (items: ShoppingItem[]) => {
  let total = 0;
  for (const item of items) {
    total += item.price * item.quantity;
  }
  return total;
}

// After: Repomix's interpretation
const calculateTotal = (items: ShoppingItem[]) => {
  ⋮----
}

Efficient? Absolutely. A little soul-crushing for the developer who crafted that beautiful logic? Also yes. It reduces token counts by up to 70%, but at the cost of the code’s very soul.

My Journey into the Abyss (And How It Actually Worked)

Skepticism aside, I had a problem to solve. So I dove in. I was too lazy to install it globally, so I ran it straight from my project’s root:

# Zero-commitment, just how I like my tools
npx repomix@latest --style markdown

A few seconds later, repomix-output.md appeared. I opened it and felt a strange mix of triumph and fear. It was all there. Every file, every questionable variable name, every comment I wrote to my future self. It was like seeing a time-lapse of my own bad decisions. Now for the moment of truth. I copied the entire content, pasted it into Claude (which boasts a massive context window), and gave it a prompt.

Adventure 1: The 2 AM Code Review

Emboldened, I was about to refactor a core module. I generated a new pack and asked: “You are a principal software architect. Review the entire codebase above and identify major design flaws or areas for refactoring.” The AI did not hold back.

It called my services module a “God object” (ouch). It pointed out duplicate logic between two controllers I’d forgotten I’d written. It even flagged a function for being “potentially vulnerable to SQL injection due to string concatenation.” I was caught red-handed by a robot. Humiliating, but incredibly useful.

Adventure 2: Refactoring Roulette

Next, I asked it to not just critique, but to act. “Based on your previous analysis, refactor fileHandler.ts for better testability and write the corresponding unit tests.”

It returned a refactored version of the file using dependency injection and a brand new fileHandler.test.ts file to go with it. This single exchange probably cost me $2 in API credits, but it saved me hours of work. Cheaper than an architect’s coffee, and it never gets tired.

The Uncomfortable Truths You Can’t Ignore

As amazing as this felt, I couldn’t shake a few nagging realities. This superpower comes with a price.

1. The Token Costs Are Real: That big refactoring analysis? It can be expensive. Users report that analyzing a moderately sized repository can cost anywhere from $5 to $300 per analysis on top-tier models. You are literally burning cash to have an AI tell you that your code needs refactoring (which you probably already knew).
2. It’s Security Theater: The Secretlint integration is nice, but let’s be clear: you are still uploading your entire proprietary codebase to a third-party service. Your company’s secret sauce is now training data for next year’s AI model. Sleep tight.
3. The Laziness Trap is Vicious: As one user wisely noted, “Using LLMs to ’learn to code’ makes you very lazy on technical details.” Repomix makes it dangerously easy to offload thinking. It’s a crutch that can feel like a prosthetic leg—helpful, but you don’t want to become completely dependent on it.
4. It’s Not Magic: The AI can and will be wrong. It can misunderstand context, hallucinate methods that don’t exist, and suggest refactors that introduce subtle bugs. Trust, but verify. Always.

A Sane Person’s Guide to Using This Thing

If you’re going to use this tool (and let’s be honest, you’re curious), here’s how to do it without shooting yourself in the foot.

1. Filter Aggressively: Your node_modules folder does not need AI analysis. Use ignore patterns to exclude everything that isn’t essential to your query.
2. Use Compression Wisely: The --compress flag is perfect for high-level architecture reviews but terrible for detailed debugging. Know when you need the “what” versus the “how.”
3. Monitor Costs Religiously: Set up budget alerts with your AI provider before you accidentally buy them another yacht.
4. Audit the Output: Always do a quick review of the generated file before uploading it. Check twice, upload once, regret never.
5. Use a Sensible Config: Don’t rely on command-line flags. Create a repomix.config.json file in your project to standardize your settings. Here’s a configuration that actually makes sense:

{
  "output": {
    "style": "xml",
    "compress": true,
    "removeComments": false,  // Keep the documentation you spent hours writing
    "showLineNumbers": false
  },
  "ignore": {
    "customPatterns": [
      "**/*.test.*",     // Tests are for computers, not AI
      "**/*.spec.*",
      "**/node_modules",
      "**/.env*",        // Seriously, don't
      "**/dist",
      "**/build",
      "**/*.log"
    ]
  },
  "security": {
    "enableSecurityCheck": true  // Because we all make mistakes
  }
}

The Verdict: Brilliant Tool or Elaborate Procrastination?

Repomix is like a Swiss Army knife: incredibly useful in specific situations, but you’ll probably use it to open bottles more than anything else. It is a well-engineered solution to a very 2025 problem. The parallel processing is fast, the compression is clever, and the ecosystem integrations are thoughtful. But just because you can feed your entire codebase to an AI doesn’t mean you should.

Should you use it?

• Yes, if: You’re doing large-scale refactoring, analyzing an unfamiliar legacy codebase, or need to generate comprehensive documentation—and you understand the costs and security risks.
• No, if: Your project is small, you’re debugging a specific line, you’re deeply concerned about code privacy, or you’re using it as a crutch to avoid understanding your own code.
• Maybe, if: You’re curious, you have API credits to burn, and you enjoy living dangerously with your intellectual property. In the end, Repomix is a powerful tool that makes developers ridiculously more efficient. It won’t fix bad architecture or absolve you from the responsibility of thinking. That part, for better or worse, is still on you. Now if you’ll excuse me, I need to go feed my entire codebase to Claude to ask why my tests are failing. Don’t judge me.