***

title: Memory types
description: >-
The three structured knowledge types in XTrace — beliefs, episodes, and
artifacts.
----------

# Memory types

Unlike flat key-value memory stores, XTrace maintains three distinct types of structured knowledge. Each serves a different purpose and follows different lifecycle rules.

## Beliefs (facts)

Atomic assertions extracted from conversations: "user prefers TypeScript," "project deadline is April 30," "we chose event-sourcing for billing."

Beliefs are the core of the revision system. Each belief has:

* **Entrenchment** — how resistant it is to being overridden. User-stated beliefs outrank system inferences.
* **Status** — `active`, `superseded`, or `retracted`
* **Lineage** — when superseded, the belief links to its replacement, forming a revision chain
* **Linked episodes** — which conversations established or changed the belief

See [Beliefs (facts)](/docs/core-concepts/facts) for the full model.

## Episodes

Summaries of conversation sessions. An episode captures what was discussed, what was decided, and what's still open — not a transcript, but a structured record of the session's outcomes.

Episodes link to the beliefs they established and the artifacts they produced. When you start a new session, episodes from recent sessions provide continuity.

See [Episodes](/docs/core-concepts/episodes) for details.

## Artifacts

Versioned work products: technical designs, blog posts, strategies, code snippets. Each artifact revision links to the previous version and to the beliefs and decisions that drove the change.

Artifacts are version-chained like git. When you hand off work to a different tool or agent, the full version history travels with it.

See [Artifacts](/docs/core-concepts/artifacts) for details.

## How they connect

```
Conversation → Extraction pipeline
                  ├── Beliefs (facts)  ← supersede / retract / consolidate
                  ├── Episodes         ← link to beliefs established
                  └── Artifacts        ← version-chain, link to driving beliefs
```

When a belief changes, XTrace can flag which episodes referenced it and which artifacts were built on it. This is **dependency propagation** — the mechanism that keeps context consistent as things evolve.