~x-ai/grok-latest → B (2:5)

B lands a foundational redesign: rooms as the permission/scope boundary separate from forum thread tags, a unified batch RPC surface replacing many REST handlers, and matching reducer/event/CLI/test updates—structure the project keeps building on. A is a precise, well-tested pair-priority improvement (attach isolates before isolate–isolate, then zip adjacent ranks) but is incremental product logic on an existing mechanism, so it carries less lasting architectural weight than B despite B’s larger mechanical migration surface.