Claude Opus 4 solved a bug in 2 hours that a programmer struggled with for 4 years

A programmer with 30 years of C++ experience and a background as Staff Engineer at FAANG told on Reddit how artificial intelligence Claude Opus 4 solved his “white whale”. This is a bug he had been fighting for 4 years. Usually this developer helps colleagues with difficult tasks himself, solving problems they struggled with for weeks. But this time the roles switched.

The problem arose after massive refactoring affecting 60,000 lines of code. Although the changes fixed many problems, they created a bug in an edge case when using a certain shader. Over these years the programmer spent about 200 hours searching for a solution, periodically returning to the problem.

Finally, he decided to try Claude Code on Opus, providing the neural network access to both old and new code. After a couple hours of work and about 30 prompts with 1 restart, artificial intelligence found the cause of the bug: in the old architecture the functionality worked only by chance, due to coincidence, and during refactoring this moment wasn’t considered.

It’s important to note that the developer previously tried using GPT 4.1, Gemini 2.5 and Claude 3.7, but only Opus 4 version could solve the problem. So the neural network surpassed an elite specialist in solving a specific technical problem requiring deep understanding of complex code context and architectural nuances.