> ## Documentation Index
> Fetch the complete documentation index at: https://docs.wazoo.dev/llms.txt
> Use this file to discover all available pages before exploring further.

# Letta

> Worlds vs Letta: a context engine against a stateful agent runtime.

## At a glance

|            | Worlds                  | [Letta](https://www.letta.com) |
| :--------- | :---------------------- | :----------------------------- |
| Category   | Context engine          | Agent runtime                  |
| Data model | RDF graph               | Agent memory files and state   |
| Retrieval  | Hybrid search + SPARQL  | Vector index over memory files |
| Provenance | Fact-level ledger       | File-level versioning          |
| Deployment | Hosted beta or embedded | Self-hosted server             |

## The philosophical difference

[Letta](https://www.letta.com) is a framework for building stateful agents.
Agents persist memory across conversations, and memory is versioned like a
filesystem. It answers the question "how do agents keep state?"

Worlds answers a different question: "how do agents know what is true?" It is a
context engine that stores and retrieves verified facts. It does not run agents,
manage tools, or schedule work.

The two are complementary rather than competing. An agent built with Letta can
call Worlds when it needs a fact it can trust.

## When Worlds fits

* You need a source of truth that any agent can query, regardless of the
  framework that runs it.
* Facts must survive across agent restarts, model swaps, and application
  rewrites.
* You want [SPARQL-verifiable](/worlds/query) answers, not retrieved text.

## When Worlds does not fit

* You want a complete agent stack in one system: memory, tool execution, and
  conversation state.
* You need long-running agent workflows with built-in persistence.

## Coexistence

Use both. Letta manages agent state and conversation memory; Worlds provides the
verifiable knowledge layer. The [MemSDK](/projects/memsdk) includes a Letta
adapter, so the same client interface can talk to either backend.