The Tangent Chain setting lets you dynamically control selection sets by selecting tangentially connected geometry in certain commands in Fusion.

In commands like Fillet and Chamfer, Tangent Chain is checked by default, so that when you select edges to fillet or chamfer, the selection set automatically includes tangentially connected edges.

You can uncheck Tangent Chain if you do not want to include tangentially connected edges.

Fillet example

If you start with a body and a single Fillet operation like this:

With Tangent Chain off, you select a single edge at a time, with the following Fillet result:

With Tangent Chain on, you select tangentially connected edges, with the following Fillet result:

If you roll back the Timeline and add additional edges to the earlier Fillet operation:

When you replay the later Fillet operation, the selection set updates to include new tangentially connected edges, with the following Fillet result:

Chamfer example

If you start with a body and a single Fillet operation like this:

With Tangent Chain off, you select a single edge at a time, with the following Chamfer result:

With Tangent Chain on, you select tangentially connected edges, with the following Chamfer result:

If you roll back the Timeline and add additional edges to the earlier Fillet operation:

When you replay the later Chamfer operation, the selection set updates to include new tangentially connected edges, with the following Chamfer result: