Hearth is a self-hosted chat application built around characters rather than around a single assistant. Character cards define who someone is, a scene layer lets several of them share a conversation with declared perception and speaker attribution, and retrieval grounds replies in documents you supply.
The problem it exists to solve is memory. Every chat product eventually runs out of context window, and when it does the character starts contradicting itself. Hearth keeps a separate character memory rather than relying on the window. Measured against a held-out set of facts at 400 turns on an 8B model, the context window alone recovered one of seven and the memory system recovered seven of seven.
Backends are swappable. llama.cpp covers NVIDIA, AMD and CPU, MLX covers Apple Silicon, and Crucible plugs in where it is available. Every pass, guard decision and retrieval candidate is traced per turn, so a regression in answer quality can be attributed rather than guessed at.
