# Long-Term Memory: Store and Retrieve — Prompt & Context Engineering

Source: https://www.skillbyai.com/en/prompt-context-engineering/m-memory

> Facts that should persist across sessions belong in storage, not in the prompt.

## Write, retrieve, forget

Long-term **memory** means saving useful facts (user preferences, project details, past decisions) outside the model and **retrieving** only the relevant ones into future contexts, like retrieval over your own notes. Design it deliberately: what is worth saving, who can see it, how it is updated when facts change, and how users can view and delete it. Saved memories are **user data**: apply privacy rules, avoid storing secrets, and remember that a wrong memory will keep reappearing until it is corrected.

## A memory record design

Structured fields make memories easy to retrieve, update and delete.

```text
{
  "user_id": "u_42",
  "fact": "prefers answers in bullet points",
  "source": "stated by user on 2026-09-12",
  "scope": "all chats",
  "updated_at": "2026-09-12",
  "expires": null
}
# retrieve: top-k memories for this user relevant to the request
# update: replace when the user changes a preference
# delete: user-visible "forget this" control
```

## Let users see and delete memory

A visible memory list with delete buttons builds trust and fixes wrong memories quickly.

**Quiz:** What should happen to long-term memories over time?

- [x] They should be updatable and deletable, with privacy rules applied
- [ ] They should never change
- [ ] They should all be sent on every call
- [ ] They should include passwords for convenience

*Answer:* They should be updatable and deletable, with privacy rules applied. Memory is user data with a lifecycle.