Editing Minimalist program (section)

=== Cycle ===
The spell-out of a string is assumed to be cyclic, but there is no consensus about how to implement this. Some analyses adopt an iterative spell-out algorithm, with spell-out applying after each application of Merge. Other analyses adopt an opportunistic algorithm, where spell-out applies only if it must. And yet others adopt a wait-til-the-end algorithm, with spell-out occurring only at the end of the derivation.

There is no consensus about the cyclicality of the Agree relation: it is sometimes treated as cyclic, sometimes as a-cyclic, and sometimes as counter-cyclic.