# Knowledge bases

> Your content, indexed in your own account and read in place.

A **knowledge base** is an index of your content that your agents search: built by the engine, in your own account, from the sources you connect. LightHouse reports on its health with counts only; it never holds the content.

## Where the index lives

The index is in your deployment, in your account: SQLite (with or without vectors), PostgreSQL (with or without pgvector) or OpenSearch. The documents it is built from are there too: each connector writes one Markdown file per item, with front matter, into the deployment’s own corpus. See [Where everything lives](/data-sovereignty/where-everything-lives/).

## Read in place, never copied

When a person opens content in LightHouse (**Security and context → Content in place**), the request goes to your deployment’s **content reader**, which dials out to LightHouse and answers only requests signed with Atlantic’s reader key. The content is shown and not kept. Reading it needs the `content_viewer` role. If your deployment cannot be reached, LightHouse says so (`503 tier_b_unavailable`) rather than showing an empty list.

## Search

The engine’s retrieval is hybrid: keyword and meaning, fused by rank, with your access scope applied inside the query. It **abstains**, returning nothing, when no passage clears a calibrated floor, so an agent can say it found nothing rather than guess. Every search is measured: candidates considered, passages returned, tokens sent and tokens not sent. See [Cost and token optimisation](/cost/).

## Freshness and re-indexing

Each connector keeps a cursor and reads only what changed since its last pull. A source is pulled on its own card’s schedule, not on a fixed clock. A changed item is rewritten; an unchanged one is left alone; an item deleted at the source is removed where the connector can tell (see each [connector’s page](/connect/)).

Each deployment reports its knowledge bases’ health daily and whenever an index changes: documents, chunks and tokens; the last ingest and the last successful one; failures by class over 30 days; stale and undated documents against the pack’s freshness policy; the duplicate rate; and coverage by tag.

## In LightHouse and the API

- **Agents → Knowledge** lists each knowledge base with its health.
- `GET /api/v1/knowledge-bases` and `GET /api/v1/knowledge-bases/{index}`: see the [Read reference](/api/reference/read/#kb-list).
- MCP: [`knowledge_bases`](/mcp/tools/knowledge-bases/), [`knowledge_base`](/mcp/tools/knowledge-base/), and [`knowledge`](/mcp/tools/knowledge/) (content, read in place, `content_viewer`).

Source: https://docs.atlanticagenticlabs.com/concepts/knowledge-bases/