I Let Cursor Chase a Bug I Could Not Reproduce and It Found the Log Line I Skipped

The worst bugs are the ones that only show up in production, the ones you cannot reproduce on your machine no matter how many times you click. Instead of staring at the screen, I handed Cursor the error report and the suspect file and asked it one specific question: where does this value get set before it is read?

The instinct to fix it yourself is the trap. I pasted the stack trace, the file where it died, and the three places I thought were involved, then I refused to let it rewrite anything. The prompt was diagnostic, not generative, find the path, do not patch. That kept it from confidently inventing a fix for a bug it did not understand.

It pointed at a log line I had skipped, the one that showed the value was null on a code path I had not considered. That is the kind of thing a model is good at, tracing a flow across a file faster than your eye. The actual fix was a three-line guard I wrote myself.

The lesson I keep relearning: use Cursor to locate, not to decide. Let it map the territory and surface the line you missed, then you make the call. The bug got fixed in twenty minutes, and the part I contributed was knowing which question to ask.

Cursor (https://cursor.sh)

Best for: Developers, Engineers.

Key features: AI-first code editor for developers; Deep AI integration for coding; Great developer experience.

Free plan: a free tier covers light use; paid unlocks limits and features.

Pricing: freemium; paid plans add capacity and features.

Pros: Deep AI integration for coding; Great developer experience; Fast iteration workflows.

Cons: Still evolving product; Best for developers only.