eros-engine
An open source Rust engine for building AI companion characters that keep a persistent memory of the user, an evolving relationship model, and a decision layer that keeps a persona in character.
eros-engine gives a companion character durable memory split into stable facts about the user and shared moments, callbacks and unfinished threads, plus an affinity model with six relationship dimensions that move on damped writes and decay over time, shaping tone and whether the companion replies at all. Before generating a reply, a Persona Decision Engine chooses an action and inner state, using rules by default with an optional LLM judge.
The engine also builds a structured, queryable profile of the user for downstream products, provides a full chat path with streaming, image understanding and generation, per-task model selection and fallbacks, and a low-latency voice turn path that supports interrupting playback mid-reply. An optional simulated world lets personas keep an off-screen life through a shared relationship graph, feed posts and per-persona storylines, fully opt-in and behind independent switches.