There are worse things than no documentation when doing one of these excavations. Design docs that were aspirational and only partially implemented. Code commen

There are worse things than no documentation when doing one of these excavations. Design docs that were aspirational and only partially implemented. Code comments that are incorrect, or reflect how things used to work. Reams of beautiful code and through documentation that it turns out are not the production implementation anymore because of a feature flag change or migration elsewhere. Migration trackers with open action items and deadlines 7 years in the past, creepily abandoned mid-flight like Pripyat. Detective work can go a long way, but in situations like this there's no substitute for ownership continuity and institutional memory.