Cases

The format declares its behaviour in boundary situations one case at a time. A situation not listed here is undecided — the product must refuse plainly, never guess.

A collection's item source

A file that does not match the schema. It remains authored content, but is not an item in that collection. Unknown frontmatter keys are preserved untouched; declared properties a matching item lacks read as empty. An explicit selector includes a file only when its type equals itemType; the implicit source applies the same type check.

A folder inside an item source. With the preferred implicit source and default non-recursive selectors, only direct Markdown children are candidates. An explicit path or paths source with recursive: true also considers matching descendants. A nested folder is never a separate collection.

A non-Markdown file inside an item source. Bytes, not an item. It is ignored by the collection and kept in its authored folder.

An item source is missing. The collection is empty. Reading never creates a source directory; only a later create operation may use its declared writeTo, or the implicit root destination.

Several collections select one file. The file remains one physical item and belongs to every matching collection. Membership is not ownership.

A query names an undeclared property. The strict query-v1 selector fails closed and matches no items.

A declaration stem also names an ordinary root page. The declaration's direct path remains collections/<name>.md; the preferred implicit source is the separate /<name>/ directory, and an ordinary /<name>.md page is not an item unless an explicit selector includes it.