A negative cycle does not guarantee distance = -∞ to all nodes. If the cycle is not reachable on the path to a target, the distance stays finite.
Example: Node 1 → Node 5 has distance 10. A negative cycle exists between nodes 2, 3, 4, but they are not on the 1→5 path. Distance to 5 is still 10.
Check which nodes are affected before concluding -∞. Run BFS from each node in a negative cycle to mark all reachable nodes as having distance −∞.