Constant MAX_NODES_PER_CSR 

pub const MAX_NODES_PER_CSR: usize = _; // 4_294_967_294usize

Hard upper bound on the number of nodes a single CsrIndex partition can hold. Each node occupies a u32 dense index; at 4 GiB nodes the index space is exhausted. u32::MAX is reserved as an “invalid” sentinel, so the usable cap is u32::MAX - 1.

4 billion nodes per collection is well beyond any realistic workload. Inserts beyond this limit are rejected with GraphError::NodeOverflow rather than silently wrapping the counter.