Invalid Metadata Structure
Q-3-40 — Invalid Metadata Structure
Document metadata must be a map structure for this output format.
What this means
A document’s metadata — what you write in the --- front matter
— is structured as a map: keys to values. The writer expects
the AST’s metadata field to hold that map shape. This error
fires when the writer finds something else there: a list at the
top level, a scalar, or null.
Why this happens
The most common cause is a Lua filter that rewrites
Pandoc.meta to a non-map value, either as part of a
metadata-manipulation pass or by accident. Hand-edited AST input
(via --from json) can also trigger the error.
The default Quarto pipeline does not produce non-map metadata.
How to fix
If a Lua filter is in use, audit any code that assigns to
Pandoc.meta directly. Metadata operations should preserve the
top-level map shape; modify keys, do not replace the whole
container with a different type.
If the failing input came from a tool that emitted JSON
directly, fix the tool to wrap top-level metadata as
{"t": "MetaMap", "c": {...}} (or whichever map form your
toolchain emits).