Journal
How AI Companion Memory Works (and Why It Forgets)
Every companion app advertises memory. Almost none of them mean the same thing by it. Here is what the word is actually covering.
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Memory is the single most advertised feature in AI companion products and the least consistently defined. Two apps can both claim their characters remember you and be describing mechanisms that behave completely differently after a fortnight of use.
Two different things called memory
The first is the context window: the block of recent conversation the model can see while it writes the next reply. Nothing in that block is stored anywhere special. It is simply the visible part of the transcript, and when the conversation grows past it, the oldest lines fall out of view.
The second is persistent memory: facts extracted from the conversation and written somewhere durable, then reinserted later. Your job, the name of your dog, the argument you had in March. This is the thing most people actually mean, and it is much harder to do well than the marketing suggests.
Where it breaks, and why it is always the same places
- Details mentioned once, in passing, in a long message — extraction tends to favour explicit statements.
- Facts that changed. If you said you lived in one city and later moved, both versions may persist and compete.
- Emotional continuity. A system can recall that you were upset without recalling why it mattered.
- The middle of long conversations, which drops out of the window first while the beginning and end are often pinned.
How to test it in five minutes
Give the character one specific, checkable detail early. Not your mood — a fact. Then talk about something unrelated for long enough to push past the window, and ask about the detail indirectly rather than quoting it back. If the answer is a confident invention rather than an admission of not knowing, that tells you more about the product than any feature list will.
What to expect from a free tier
Persistent memory costs money to run on every message, so it is the feature most often reserved for paid plans or capped on free ones. If memory matters to you, check where the cap sits before you invest thirty hours in a conversation.