Root cause of the blank Jung tree: a child double-linked to the same parent
(and, generally, any cycle) made family-chart recurse forever.
Backend (the real fix):
- create_relationship now rejects an equivalent existing edge → 409.
parent_child is directional (parent→child); partnership/sibling match the
pair in either order. So you can't link the same two people the same way
twice. (GEDCOM import already deduped; manual creates didn't.)
Frontend (defense in depth so data can never blank the view):
- Tree view sanitizes the graph before rendering: dedupes parents/spouses,
drops self-links, and greedily breaks ancestor cycles (a person can't be
their own ancestor); children are derived from the kept edges. The render is
wrapped in try/catch and shows a note instead of a blank canvas, telling you
which conflicting links were skipped.
- Person page surfaces the 409 ("They're already linked that way.").
59 backend tests pass (incl. dup-rejection + reverse-parent-child allowed).
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
