Invalid Tag Character
Q-1-26 — Invalid Tag Character
A YAML tag contains characters outside the allowed alphanumeric-and-underscore set.
What this means
Quarto’s configuration tags accept only letters, digits, and underscores between components. Any other character — punctuation, hyphens, dots, or symbols — causes the tag parser to reject the tag outright.
Why this happens
The character most likely to trigger this error is the hyphen:
!prefer-md instead of !prefer_md. Quarto chose the underscore
as the component separator because it is fully supported by
standard YAML parsers, where the hyphen would have other meanings
in tag URIs.
Other characters that occasionally appear by accident: dots
(!prefer.md), commas, slashes, and dollar signs left over from
shell-style identifier conventions.
How to fix
Replace the invalid character with the appropriate separator. For
component separators, that is the underscore: !prefer-md becomes
!prefer_md.
If your tag intentionally contains a character outside the allowed set — for instance a custom tag inherited from another tool — Quarto’s tag system cannot interpret it. Remove the tag, or rename it to use only allowed characters.