FA-75074 / CRDT convergence / Member archive

Two-phase graph: edges may be added to removed vertices · case 04

An edge to a vertex that was removed is accepted instead of rejected.

Member previewVariant 4 · 3 implementations · 8 checks per implementation

Case contract

Vertices and edges each have grow-only add and remove sets. A vertex is live when added and not removed; an edge is visible when added, not removed, and both endpoints are live. At the origin replica, adding an edge requires both endpoints live, removing a vertex requires no visible edge touching it in either direction, and removing an edge requires it visible; failed preconditions record the op index. ["merge", s, d] unions all four sets into d. Return sorted live vertices and visible edges per replica plus rejections.

Why this case matters

Graph CRDTs must keep edges consistent with vertex removals that happen concurrently on other replicas.

One recorded failure

Sample boundary fixture

This sample comes from the broken implementation of a controlled reproducer.

Boundary fixture	Actual	Expected	Outcome
edge to a removed vertex is rejected	`{"graphs": [[["u"], []], [[], []]], "rejected": []}`	`{"graphs": [[["u"], []], [[], []]], "rejected": [3, 4]}`	Failed

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