---
title: "Folder sidecar (`_meta.yml`)"
description: "Per-folder YAML sidecar that overrides a folder's display title, sort order in its parent, and llms.txt subtree opt-in."
canonical_url: https://usepennington.net/reference/front-matter/folder-sidecar/
sidecar_url: https://usepennington.net/reference/front-matter/folder-sidecar.md
content_hash: sha256:86cb0b16cd8e3a928aacef58cb5685eb958781e5e5eeef2d6b7063f8de26be06
tokens: 776
uid: reference.front-matter.folder-sidecar
reading_time_minutes: 2
---

Reference
# Folder sidecar (`_meta.yml`)

Per-folder YAML sidecar that overrides a folder's display title, sort order in its parent, and llms.txt subtree opt-in.

 
A `_meta.yml` file dropped in any content folder declares folder-level metadata: an alternative display title, an explicit position in the parent navigation level, and (optionally) opt-in to a dedicated `llms.txt` subtree split. All fields are optional.

 
Without a sidecar, a folder's sort position is the **min-of-children** value: the smallest `order:` found on any page inside it. The `order` key below overrides that emergent value.

 
## Schema

 
```yaml
title: "Reference"
order: 5
llms:
  description: "API surface, host extensions, front-matter keys, ..."
```

 
    Key Type Default Effect     `title` string `null` Overrides both `FormatSectionTitle` (auto-generated from the folder slug) and the title from a sibling `index.md`.   `order` int `null` Sets the folder's position among its parent's children. Overrides the emergent min-of-children rule and any `order:` set on a sibling `index.md`.   `llms.description` string `null` When present, opts the folder into `llms.txt` subtree generation. Requires `title` to also be set; without it the description is silently ignored (no subtree, no warning, no error).    
## Resolution rules

 
 - A field that's set wins over every other source for that folder.
 - A field that's omitted falls through to the original behavior: `FormatSectionTitle(folderSlug)` for the title, min-of-children for the order, and "not an llms subtree" for the llms split.
 - Folders without `_meta.yml` are unaffected — adoption is folder-by-folder.
 
 
## Discovery

 
`MarkdownContentService` discovers `_meta.yml` files under its content path, but it is not the only source. `FolderMetadataRegistry` aggregates rows from every registered `IContentService` that implements `IFolderMetadataProvider`, keyed by the folder's canonical URL prefix. A custom content service that surfaces its own folder metadata through that interface contributes sidecars on equal footing. Hot-reload refreshes the registry on file change.

 
## Example

 
```yaml
# docs/Pennington.Docs/Content/reference/_meta.yml
title: Reference
llms:
  description: "API surface, host extensions, front-matter keys, Markdig extensions, UI components, diagnostics codes."
```

 
The `Reference` folder appears in the sidebar with that title, and `/reference/llms.txt` is generated as a subtree split of the main `llms.txt`.

 
## See also

 
 - Background: [Navigation-tree construction](https://usepennington.net/explanation/routing/navigation-tree.md) — how `_meta.yml` interacts with `HierarchyParts` and per-page `order:`.
 - Related reference: [Front-matter keys](https://usepennington.net/reference/front-matter/keys.md) — per-page YAML keys including `order:`.
 
 
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