frontmatter-too-large rule explained

What it catches#

Frontmatter is too large to parse safely.

An opening --- followed by more than 64 KB before any closing ---. asitis does not parse a block that size, because hostile YAML can take a long time to read, and no real frontmatter comes close: name, description and a few options fit in a few hundred bytes.

Why it matters#

Frontmatter over 64 KB is not parsed, which protects against YAML that takes a long time to read. Real frontmatter is a few lines.

Bad example#

---
name: brand-assets
description: Apply the brand kit. Use when producing slides or documents.
logo: data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAABLAAAASwCAYAAAAK...
---

A base64 image pasted into the frontmatter pushes it far past 64 KB. The other common cause is a missing closing --- in a long file, which makes the "frontmatter" run to the end of the document.

Good example#

---
name: brand-assets
description: Apply the brand kit. Use when producing slides or documents.
---

The logo is in [assets/logo.png](assets/logo.png).

How to fix#

Move bulk data into a file next to SKILL.md and link to it. If the block is large only because the closing --- is missing, add it after the last field.

Suppress or configure#

For one finding, put a comment on the line above it. The reason after -- is optional but worth writing:

<!-- asitis-disable-next-line frontmatter-too-large -- why this one is fine -->

For a whole file:

<!-- asitis-disable-file frontmatter-too-large -- why this file is an exception -->

For every file, turn it off or change its severity in .asitisrc.json:

{ "rules": { "frontmatter-too-large": "off" } }

A .asitisrc.json overrides entry limits a change to some paths, and a baseline (asitis lint --format json --write-baseline) accepts today's findings so only new ones fail the build.

Source#

Agent Skills specification, read on 14 October 2026.

frontmatter-too-large