Why is this activity here?
A Gantt shows when. A network shows why. Every activity sits in the column of its earliest possible position, so the arrows all point one way and the chain is visible.
The network, laid out so it reads as flow
Every activity sits in the column of its earliest possible position, so all the arrows point one way. A circular dependency refuses to draw rather than drawing nonsense.
Activities
Predecessors accept A, A:SS+2, B:FF-1.
The network
Predecessors and successors
How the layout works
Each activity's column is the longest chain of predecessors leading to it, which guarantees every edge points rightwards. Within a column, activities are ordered near the average position of their predecessors, so chains stay roughly straight without a full crossing-minimisation pass.
A cycle refuses to draw. A diagram of an impossible network is worse than a clear refusal, so the tool names the loop instead.
An edge is drawn critical only when both ends are. Colouring an edge by either end alone produces a red chain running through an activity that has float, which is exactly the wrong thing to show.
What a network shows that a Gantt cannot
A bar chart shows when. A network shows why. The reason an activity sits where it does is the chain of things in front of it, and that chain is invisible on a Gantt unless you already know it.
This matters most when someone asks whether two pieces of work can be swapped or run together. On a Gantt that is guesswork; on a network you can see whether anything actually connects them.
Circular dependencies are always a modelling error
Work cannot depend on itself, directly or through a chain. When a cycle appears it is because someone recorded a feedback loop — design informs build, build reveals design problems — as a dependency.
That is a real relationship and it is not a schedule dependency. The fix is usually to split the activity into the part that comes before and the part that comes after, which is also a more honest description of the work.
Edges that skip columns
An arrow spanning several columns passes behind everything between. A few are normal; a lot usually means one or two activities are gating a large amount of otherwise unrelated work.
That is a fragility worth knowing about — a single slip there propagates everywhere at once, and a Gantt chart makes it look like a routine dependency.