The "Default" node of a branch-one is built with branchIndex -1 and is the
structurally-required else branch (stored separately from the branches array),
so it cannot be removed. Its delete button still rendered, and clicking it
called deleteBranch with index 0, which in removeBranch became
branches.splice(-1, 1) — destructively removing the LAST explicit branch.
Gate the delete button on branchIndex >= 0 so it only appears on explicit
branches.
Co-authored-by: Claude Opus 4.8 <noreply@anthropic.com>
Ruben FiszelandClaude Opus 4.8
210ea3cc5a