A landing may target another branch that has its own open landing; that pair is a stack, read from the targets rather than recorded anywhere. No new card, no dependency field -- the edge is already implied.

Stacks land bottom-up. accept refuses a landing whose target has its own open landing, and accepting one retargets whatever was stacked on it onto the branch it just landed on. That is the whole restack: a metadata write per child, because a segment's branch already descends from the one below it, so after that lands the merge sees only the segment's own change.

Adds 'landing retarget', a target reply resolved by the same latest-wins rule as a state transition. ls indents a stack by depth; show names what a segment sits on, what sits on it, and when its base was rejected.

Verified six deep on a shared file, which is the depth the design claim was previously only reasoned about. check-in: 3767f1eafc user: dmestas tags: strata