GaneevEcoA starting pattern that works
- Ask for a plain-language walkthrough of what a module does before asking it to change anything at all, establishing shared understanding first.
- Have it flag areas of the code it's genuinely uncertain about — treat those specific areas as places to bring in a human who actually knows the history behind them.
- Use it to draft missing documentation as you go through the codebase, so the next person to touch this module doesn't have to start from zero either.
One caution worth stating plainly
Confidence in an explanation isn't the same thing as correctness, especially in code with unusual historical context baked into decisions that made sense once but no longer do. Treat its read of legacy code as a strong first draft to independently verify, not as a verified fact you can build on without checking.
Legacy code frequently contains workarounds for problems that no longer actually exist, or business logic that only made sense given a constraint that was quietly removed years ago and never cleaned up afterward. A tool reading the code fresh has no way to know that missing context existed in the first place, and neither would a new human hire on their very first day — the difference is a new hire usually asks around before changing something that looks slightly odd, and it's worth deliberately building that same cautious instinct into how your team actually uses this tool.
Turning this into lasting institutional memory
The real value of this pattern isn't just getting one engineer unstuck faster on a single task — it's that the documentation generated along the way becomes a lasting resource for the next person who has to touch that same module, which for most legacy codebases is a recurring, predictable event over time, not a rare one-off occurrence. Treat each pass through an unfamiliar module as a genuine opportunity to leave something useful behind for whoever comes next, not just as a means to get the immediate task done and move on.
Teams that do this consistently, pass after pass, find their "nobody understands this anymore" codebase gradually shrinking over time, module by module, as an incidental side effect of ordinary maintenance work — without ever needing to run a dedicated, expensive, and disruptive documentation project to accomplish the same result deliberately.
A small practical tip that makes this pattern stick: store the generated walkthroughs somewhere the whole team can find them later, next to the code itself rather than in a personal notes file. The value of this exercise compounds specifically because the next person benefits from the last person's pass through the same module — and that only happens if the documentation is discoverable rather than scattered across individual engineers' private notes.
None of this replaces the judgment of someone who's actually worked in the codebase for years, and it isn't meant to. It's meant to make the gap between "nobody currently understands this" and "someone has a working understanding of this" much shorter than it used to be, so that ordinary maintenance work doesn't keep getting blocked waiting for the one person who remembers why a particular piece of logic exists.