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Invalid project type contribution

extension
An extension resolved a custom project.type, but its contributes.project fragment is unusable.

Q-16-7 — Invalid project type contribution

An extension resolved a custom project.type, but its contributes.project fragment is unusable.

What this means

An extension can define a custom project type, so a project can set project.type: my-org/my-type and inherit configuration the extension supplies. The extension declares this under contributes.project in its _extension.yml.

Quarto found the extension your project.type names, but could not use what it declares. This stops the render — unlike most extension problems, there is no sensible way to continue, because the project type decides how every document in the project is processed.

Four things make the fragment unusable:

  • contributes.project is not a mapping.
  • Its project.type is not a string.
  • It names a base type that is not built-in. Chaining custom types — one extension’s type inheriting from another’s — is not supported.
  • It names manuscript, which Quarto 2 does not implement yet. (A book base is fine — see the book projects guide — this restriction no longer applies to it.)

The message names the extension and the path to its _extension.yml.

Why this happens

  • A hand-written extension manifest with contributes.project as a list rather than a mapping.
  • An extension built against Quarto 1, where the constraints differ.
  • A base type that is itself a custom type, usually an attempt to build a family of related project types by layering them.
  • A manuscript-based extension, which cannot work until Quarto 2 implements the manuscript project type.

How to fix

This is a defect in the extension, not in your project — the fix belongs in the extension’s _extension.yml. A usable contribution looks like this:

title: My Project Type
version: 1.0.0
contributes:
  project:
    project:
      type: website
    format:
      html:
        theme: cosmo

The nested project.type names the built-in base type the custom type builds on: default, website, or book. Everything else in the fragment is configuration merged into projects that use the type.

If you do not maintain the extension, report the problem to its author. In the meantime, set project.type to a built-in type and copy the configuration you need directly into _quarto.yml.