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May 7, 2026

Front matter that catches your typos

By Phil Scott

Type tite: instead of title: and YAML accepts it without complaint — a valid key, but not one Pennington reads. The page builds, the title falls back to a default, and you notice when the page looks wrong. Pennington now flags that earlier.

Unknown keys get flagged

Every front-matter parse pre-scans for keys it doesn't recognize. A misspelled or stray key raises a diagnostic with the key, the file, and the line:

text 
Unknown front-matter key 'tite' in content/guide/setup.md:3

Under serve that's a warning in the dev overlay. Under build, strict mode is on by default and the warning becomes a build failure — dev mode and build mode stay permissive while you write and strict before you ship, so a typo can't reach a published site. The keys Pennington recognizes are listed in the front matter reference.

Code fences, too

The same check reaches into code blocks. Tag a fence with a language Pennington can't highlight — a typo like cshrap, or something genuinely unsupported — and it emits an Info diagnostic. It fires once per unknown language, so a site with fifty cshrap fences gives you one note, not fifty.

front-matterdiagnostics