Coefficient of Inbreeding (COI)
COI is the inbreeding percentage shown by the game. In practical terms, it answers: “how closely related were this kitten’s parents?” Higher values mean the parents share more ancestry, which makes defect planning and room setup more important.
How the game uses COI
The Mewgenics Wiki breeding page documents the thresholds the game uses for inbreeding labels and explains that a kitten’s COI comes from the parents’ relatedness. The same page also documents the v1.1 behavior where stimulation affects inheritance and defect outcomes, so room setup matters most when you are breeding close relatives.
How this tool calculates COI
Mewgenics Save Viewer builds a family lookup from your save and runs a recursive kinship calculation over the known parents and ancestors. That lets the roster, breeding optimizer, and family tree estimate how related two cats are without relying only on the game’s label text.
For performance, the app memoizes those relationship checks once per loaded roster. That matters on large saves, where every possible breeding pair may need a COI estimate.
Practical tips
- Use unrelated or distant lines when you want safer offspring.
- When intentionally stacking inbreeding, check the optimizer’s defect-risk notes before committing to the pair.
- Use saved room stimulation when available; it gives the optimizer better context for v1.1 defect planning.