Long-term memory
Updated November 9, 2026
Long-term memory is an AI companion's ability to keep information from past conversations and use it in later ones.
In the systems researchers have described, long-term memory sits outside the language model. Past conversation is stored as transcripts, summaries or extracted facts, and a relevant slice is pulled back in when it's needed. That makes it different from the context window, which only covers what the model can see in the moment.
When choosing a companion, judge long-term memory by behavior over weeks rather than by feature lists. Does a detail from last month come back, is it the current version and does the app avoid inventing things? With Hallie, it shows up as follow-ups on what you told her in her Messages thread.