POST /hierarchy/_expand

Returns one level of the navigation tree the web interface draws. It refuses the vendor content types every other POST requires and accepts only application/json.

• The content type is inverted. _search, _summarize and _text_search refuse application/json and demand a vendor type; /hierarchy/* does the exact opposite. A client with one shared POST helper gets 415 on whichever half it did not write first.

• One level per call. children names the next paths and has_children says which are worth expanding, so walking a project is one call per node.

• Code 107 appears here and nowhere else in the corpus. It is a lookup that found the wrong number of rows, not a malformed request.

• seed_entity_field changed nothing on the probed site. Omit it until something shows it matters.

• A child has no path when its ref.kind is empty: {"label": "No Shots", "ref": {"kind": "empty", "value": null}, "has_children": false} is the placeholder for a level with nothing under it, and it is a child like any other. Read path with a default.

• ref.kind is entity for a row or a group that is one, entity_type for the ungrouped bucket, list for a group that is a list value, and empty for the placeholder.

• The __none__ segment is reachable at two spellings. _expand writes <field>/<GroupType>/__none__ and _search returns <field>/__none__; both answer the same rows, and the label is templated off the segment, so the second reads Shots with no __none__.

• A path is answerable whether or not children named it. Expanding a level whose grouping field has no rows answers one empty child, and the __none__ path under that level still answers its rows.

Measured by

• 064_hierarchy_expand_buckets (findings) — Dedupe children by path and keep the first. The __none__ bucket is repeated once per group, byte-identical every time, and its rows are disjoint from every group's.
  rules: doors/findings-read
• 046_search_without_a_path (findings) — /hierarchy/_expand and /hierarchy/_search refuse the vendor content types every other POST requires and take application/json alone, so one shared POST helper 415s on half the API.
  rules: doors/findings-filter

corpus/endpoints/post_hierarchy_expand.md