  Existing works on long-term open-domain dialogues focus on evaluating model
responses within contexts spanning no more than five chat sessions. Despite
advancements in long-context large language models (LLMs) and retrieval
augmented generation (RAG) techniques, their efficacy in very long-term
dialogues remains unexplored. To address this research gap, we introduce a
machine-human pipeline to generate high-quality, very long-term dialogues by
leveraging LLM-based agent architectures and grounding their dialogues on
personas and temporal event graphs. Moreover, we equip each agent with the
capability of sharing and reacting to images. The generated conversations are
verified and edited by human annotators for long-range consistency and
grounding to the event graphs. Using this pipeline, we collect LoCoMo, a
dataset of very long-term conversations, each encompassing 300 turns and 9K
tokens on avg., over up to 35 sessions. Based on LoCoMo, we present a
comprehensive evaluation benchmark to measure long-term memory in models,
encompassing question answering, event summarization, and multi-modal dialogue
generation tasks. Our experimental results indicate that LLMs exhibit
challenges in understanding lengthy conversations and comprehending long-range
temporal and causal dynamics within dialogues. Employing strategies like
long-context LLMs or RAG can offer improvements but these models still
substantially lag behind human performance.
