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Invalid Enum Value

yaml
A value is not one of the choices the schema’s enumeration allows.

Q-1-12 — Invalid Enum Value

A value is not one of the choices the schema’s enumeration allows.

What this means

Some Quarto configuration fields accept only a fixed set of values. Output format names, theme names, engine names, and many other configuration choices are restricted this way. The schema calls this restriction an enumeration — literally the list of values it will accept.

This error fires when your YAML’s value passes the basic type check (the field expects a string and you provided a string), but the value itself isn’t on the allowed list. The error message includes both the value you provided and the full list of acceptable values.

Why this happens

Three common cases:

  • Typo in the value. html5 instead of html, gfm-md instead of gfm, or capitalization mismatches like HTML for html. Enum matching is case-sensitive.
  • A value valid in a different release. A name that worked in Quarto 1 might not exist in Quarto 2, or a third-party format may not be installed.
  • Confusion between similar fields. Providing a theme name in a slot that wants an output format, or the other way around.

How to fix

The error message lists every allowed value for the property. Pick the one you meant, paying attention to spelling and case. If none of them is what you wanted, the property may not be the right place for what you are configuring — check the documentation for the configuration block the property belongs to.