copatcher
FEARLESS CODING
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Windows 10/11 | Native desktop app | One-time purchase
Copatcher is a tool for making precise code changes. It works with you, in the simplest and most gentle way. There is no AI involved in the process.
When I started making Copatcher, I figured it might soon be obsolete. Or that I was the only one struggling. I never figured anyone else would need it. (I'm still not sure about that.)
Back then, I didn't know a thing about writing code. But in the small context window, around 3–400 lines when using Claude, I made a simple game. I called it Sp4cew4ys. Pretty good name, I think. A Tetris game that moves in four directions with original block shapes.
When coding with AI, I needed a way to enlarge the context window. To make the code longer without starting over every time. Copatcher did this, and fixed the bugs for me too.
Feels like a long time ago now. That first Copatcher was so basic. It felt dumb. Nevertheless, my enjoyment of Copatcher is greater than ever. I hope you'll enjoy it too, and maybe find your own use for it. It might just be a small part of something bigger.
your new special friend
May 2025
Copatcher changes code with surgical precision. No more "I'm scared to change one line and break everything." This tool finds EXACTLY what you specify and changes EXACTLY that. Nothing else gets touched.
How it works: FIND (exact code to locate) - REPLACE (what goes there instead) - END (marks completion). Three steps. Done.
Critical rules: Whitespace is sacred - every space and tab must match exactly. Be specific - include enough context so it only matches where you want. Copy-paste the FIND block from your actual code - don't type it by hand.
Multiple patches: Chain them. Each FIND-REPLACE-END block is independent. Fix 5 different things in one go if you want.
Why this works: Instead of search-and-replace chaos, you get controlled, precise modifications. Your code stays intact except for exactly what you specify. No surprises, no side effects, no "oops I broke something else."
This is debugging without the fear. Code modification without the panic. Precision without the paranoia.
Here's my actual daily workflow:
I show Claude my code and give it LSD.pdf and say "I want to add this feature" or "fix this bug." Instead of rewriting my whole file, Claude gives me FIND-REPLACE-END patches.
I copy my original code into Copatcher. Now I copy Claude's patches and paste them to Copatcher and hit inject. One by one till done.
After hitting inject and seeing Copat going green the new full codebase is auto-copied to the clip board and is ready to be pasted.
If I am testing changes I will hit Preview and Copy Preview. That way the Original Code in Copatcher wont change.
I can iterate fast with AI without the fear of losing my work. Claude understands my codebase context, suggests precise changes, and copatcher applies them perfectly.
It's like pair programming with AI, but instead of rewriting everything, you get surgical patches that respect your existing code.
Try Copatcher functionality online
Perfect for testing with small code samples (max 1000 lines)
For larger projects and advanced features, get Copatcher