A Union dropped every construction certificate, so after any join no face
could take a durable sketch: sketch.create failed with "this face has no
exact planar source" even on a face the join never touched (#420, and the
"CREATE SKETCH: operation failed" reports #344, #195).
- kernel: map planar sources through a Union from both operands, with the
same exact-support rule Cut uses. Coplanar supports of the two operands
carry distinct identities, so a face merged from both stays without one.
- doc: Join extrude and Join box tools are certified like new bodies; a
cap moved off its designed height (into the target, or past a curved To
face) is not certified. Join producers are accepted when certifying.
Tests: both operands' faces attach and follow an upstream edit and a
reopen; a merged coplanar face is refused and fixed:true works; a face a
join covers whole is lost without moving to the new roof. Tests that used
a joined face as their "uncertified" example now use a merged face; the
trimmed-face case in a_sketch_on_a_face_stays_on_that_face now stays
attached to the surviving piece.
Claude-Session: https://claude.ai/code/session_01YDDPmNdRoBgkHcLeUDKVfb
Co-authored-by: Claude Opus 5.5 <noreply@anthropic.com>
