FCCombo

Each catch of one species adds to a combo count, and every step lowers the shiny odds multiplicatively, so the odds fall by a fixed factor per threshold: 4096 at 20 catches, 2048 at 40, 1024 at 60, and so on. Switching to another species resets the chain automatically. The tracking covers the player's live combo across the whole session, and the spawn logic of Cobblemon decides which Pokémon count toward it.

The boost reaches only Pokémon that appear close to the player, which keeps the chain tied to the area the player is actually hunting in. A per-species blacklist can exclude particular Pokémon from the boost, and an always-visible combo display can be toggled in the config. Messages for milestones and interruptions are kept short and informative. FCCombo needs Cobblemon for Fabric and Fabric API, and it is published only for 1.21.1. The mod is server-side only, so clients need nothing installed, and it is released under All rights reserved, which means it is not open source.