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Undefined citation

A [@key] citation names a key that isn't in your bibliography. This isn't a Keystone check — Pandoc's citation processor resolves keys and warns when one is missing. The build continues, with the citation left unresolved.

What it looks like

As Smith argued [@nope2024], the tide was turning.

WARN: Citeproc: citation nope2024 not found

What it means

When you declare a bibliography, Keystone runs Pandoc with citation processing, which matches each [@key] against your .bib entries. An unmatched key can't be rendered, so it's reported and left unresolved in the output rather than dropped. Because it's a warning, a lenient build still succeeds — with a broken citation in the book. Under strict mode it fails the build.

Match the key to a .bib entry

Keys are case-sensitive, so the match has to be exact — and the entry has to be in the file your bibliography points at. See Notes & citations.

  • Image not found — the other common tool-origin warning strict mode catches.