Logic Error Detector
Spot hidden logic flaws your tests might miss
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Your tests pass and nothing throws, so why is the total still wrong? Where do you start when the code runs perfectly and the answer is quietly incorrect? The Logic Error Detector is built for that case. Paste the code, say what you expected and what you got, and it works backwards to the line that decided wrong.
Logic Error Detector takes the code you paste plus the result you expected and the one you actually got, and returns the faulty comparison or bound, the reasoning behind it, and a corrected block to compare against.
What is Logic Error Detector?
A logic error is a bug your compiler is happy with. The syntax is fine, nothing crashes, and the output is not what the code was meant to produce. Logic Error Detector reads what you paste, compares it with the behaviour you describe, and points at the comparison, the loop bound or the branch that misses your intent. It reads text only and never runs your program.
Root cause first
Explain Root Cause is on by default, so you get the reasoning, not just a patched line.
A corrected block
Provide Fixed Code returns the rewritten block, faster to read than a description of it.
A failing test
Switch on Show Test to Reproduce for a case that fails before the fix and passes after.
Code That Runs Clean And Still Answers Wrong
A crash tells you where to look. A wrong number does not. You add print statements, re-read the same twelve lines, and slowly talk yourself into believing the loop is fine. A fresh reader breaks that spell, because they carry no memory of what the code was meant to do. Logic Error Detector reads the code as written, not as remembered.
How Does Logic Error Detector Work?
Paste the code into the prompt box and put the expected result next to the one you got. Set Issue Type to Logic Bug so the analysis stops hunting for crashes. Set Analysis Depth to Deep for anything with nested conditions, and Output to Root Cause when you want reasoning before the patch. What comes back names the line, and says what it does instead of what you meant.
Tip The Thoroughness slider starts at 70%. Push it up for code with several interacting conditions, and down when you want a quick opinion on a short function.
Where Silent Wrong Results Usually Hide
Logic bugs cluster. These three turn up week after week.
| Where the wrong answer shows up | What is usually behind it |
|---|---|
| Totals off by one row | An inclusive bound where an exclusive one was meant |
| Discounts applied twice | A condition that falls through instead of returning |
| Filters that return everything | An OR sitting where the intent was AND |
Confirm The Fix Before You Merge It
Nothing here executes, so the fix stays a proposal until your own test run says otherwise.
- ✅ Reproduce the original wrong result before you change anything
- ✅ Apply the fix and check the same input now gives the right answer
- ✅ Run the rest of your suite, because a fix can move a bug
- ✅ Keep the reproduction case as a regression test
Habits That Waste A Good Analysis
The commonest mistake is pasting the function alone. A logic bug often lives in the caller, in a default argument or in the arriving data, so include the lines around it. The second is a vague description. Wrong output is not a description; the expected value beside the actual value is. If your code is genuinely throwing an exception, the Error Fixer is the better starting point.
Nothing here is metered: no account, no daily limit, no paid tier on any EizTools page, and you choose the AI model yourself before each run. Two engines often notice different things in the same function, which is worth knowing on a stubborn bug. Logic Error Detector sits with the other coding tools.
Frequently Asked Questions
Can it help when there is no error message at all?
That is the case it is built for. Describe the wrong behaviour instead of an error. The clearer you are about expected versus actual output, the faster it narrows to a line.
How much code should I paste?
Enough for the logic to make sense on its own. The function, its caller and any helper it depends on is usually right. A single line rarely produces a useful answer.
Does it edit my files or run my code?
No. It reads the text you paste and writes back an explanation and a corrected block. Applying the change, running it and testing it are all still your side of the job.
What if the bug is in the data, not the code?
Say so in the prompt and paste a sample row. The tool reasons about the code in front of it, so a value that arrives in the wrong shape is invisible unless you show it one.
A logic bug survives because everyone reading the code already knows what it was meant to do. Handing it to something with no such memory is often all it takes. Paste the function and the wrong result into Logic Error Detector above, then read the root cause before the patch.
Sabir Bepari
Founder of EizTools and a passionate AI enthusiast dedicated to building practical, user-friendly AI tools that simplify everyday tasks.
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