Extend `llms-txt` to book projects

[mcanouil]

llms-txt is provided in the schema which imply it is available to book project, unfortunately that's currently not true.

The feature appears to be available because:

1. The schema includes llms-txt as a valid boolean option for both website and book configs.
2. The book config imports website config functions.
3. The changelog mentions it as a website feature.

• quarto-cli/src/resources/schema/definitions.yml

  Lines 731 to 734 in d577ef4

  	llms-txt:
  	boolean:
  	description: |
  	Generate llms.txt and .llms.md files for LLM-friendly content consumption.

• quarto-cli/src/project/types/book/book-config.ts

  Lines 82 to 87 in d577ef4

  	import {
  	repoUrlIcon,
  	websiteConfigActions,
  	websiteConfigString,
  	websiteProjectConfig,
  	} from "../website/website-config.ts";

But without the formatExtras hook being inherited or implemented for books, the actual processing never occurs.

• quarto-cli/src/project/types/website/website.ts

  Lines 360 to 367 in d577ef4

  	// Add llms.txt finalizer if enabled
  	if (websiteConfigBoolean(kLlmsTxt, false, project.config)) {
  	extras[kFilterParams] = extras[kFilterParams] || {};
  	extras[kFilterParams]["llms-txt"] = true;
  	extras.html[kHtmlFinalizers]?.push(
  	llmsHtmlFinalizer(source, project, format),
  	);
  	}

• quarto-cli/src/project/types/book/book.ts

  Lines 195 to 203 in d577ef4

  	// inherit a bunch of behavior from website projects
  	preRender: bookPreRender,
  	postRender: bookPostRender,
  	formatLibDirs: websiteProjectType.formatLibDirs,
  	metadataFields: () => [...websiteProjectType.metadataFields!(), "book"],
  	resourceIgnoreFields: () => [
  	...websiteProjectType.resourceIgnoreFields!(),
  	kBook,
  	],

There are also no book-specific tests for this feature; only website tests exist which is expected in some regards.

Discussed in https://github.com/orgs/quarto-dev/discussions/14275

^{Originally posted by meierluk March 27, 2026}

Description

Is the new feature about llms-txt also available for Quarto books (where the HTML output is basically of type website)?

Using the default template for books (see below), I cannot get it running.

project:
  type: book


book:
  title: "test-book"
  author: "Norah Jones"
  llms-txt: true
  date: "27.3.2026"
  chapters:
    - index.qmd
    - intro.qmd
    - summary.qmd
    - references.qmd

bibliography: references.bib

format:
  html:
    theme:
      - cosmo
      - brand
  pdf:
    documentclass: scrreprt
```</div>

[cderv]

Fixed in #14881.

The cause turned out to be simpler than the description here suggests. formatExtras is inherited: book.ts calls websiteProjectType.formatExtras directly, and the llms.txt finalizer it registers reads llms-txt through websiteConfigBoolean, which looks under the website key. Setting llms-txt in a top-level website: block of a book project already produced a correct llms.txt and the matching .llms.md files before this fix.

What was actually missing is that a book project copies a fixed list of website options from book: into that internal website configuration, and llms-txt was never added to the list, so the value never reached where the hook reads it. Adding it is the whole fix. Same root cause as #14879 and #10114.

A book-specific smoke test comes with the PR, so the gap you noted at the end of the description is covered too.