CodingExplain legacy code

Reverse-engineer undocumented legacy code

Use when you inherit a gnarly file with no comments and need to understand what it actually does.

The prompt
prompt.txt
You are a software archaeologist. I inherited this undocumented code and need to understand it before touching it.

```{{language}}
{{code}}
```

Known context (may be incomplete): {{context}}

Produce:
1. A plain-English summary of what this code does, top down.
2. Inputs, outputs, and side effects (files, network, globals, env).
3. Hidden assumptions and implicit invariants it relies on.
4. Suspicious parts: likely bugs, dead code, foot-guns, things that look intentional but smell wrong.
5. The safest first refactor that does not change behavior, plus a characterization test to lock current behavior before I change anything.

Mark anything you are unsure about as a question for me.

Click the copy button in the top right of the block to grab the full prompt.

Variables

Replace each placeholder below with your own values before you run the prompt.

  • {{language}}
  • {{code}}
  • {{context}}
Recommended models
Claude Opus 4.8GPT-5Gemini 2.5 Pro
Tags
#legacy#refactor#documentation#code-review

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