Set-Based Design
Keeping several workable options alive, and narrowing only at the last responsible moment.
The usual method picks one approach early, because deciding feels like progress, and then spends the rest of the work defending that choice against everything learned since. Set-based design does the opposite: it carries a set of viable options forward together, develops them far enough to be compared honestly, and converges only when deciding later would cost more than deciding now.
The reason it works is that early decisions are made when ignorance is greatest. Every week of real work produces information that would have changed the choice, and a body committed too soon must either waste that information or pay to undo the commitment. Holding a set is not indecision — it is refusing to spend certainty you do not yet have.
It pairs with the rest of the production discipline. Design To The Goal fixes what may not move — the Goal and target quality — which is precisely what makes it safe to keep everything else open. Advantage Based Decision Making is how the set is narrowed when the moment comes: options are weighed by their advantages, not by whose idea they were. And the last responsible moment is a real test rather than a mood — the moment after which delay begins to remove options rather than preserve them.
A Cell runs this at its own scale. Two or three plausible ways to do the Quest are held for a few weeks while the constraints are cleared, and the choice is made when enough is known. The failure it prevents is common and quiet: a Cell that committed in week one and by week six is arguing about loyalty to the plan instead of about what would work.
Also called: carrying a set · last responsible moment Stands on: Design To The Goal · Design · Possibility Of Reversal · Tightly Coupled Learning and Action Opens onto: Advantage Based Decision Making · Prototyping · The look-ahead · Constraint · Decision Making In play: the table · the Room Sources: The LIØNSBERG Pattern Language — Synthesized, Design To The Goal (ore — named with Element 10, no card written) · Twelve Irreducible Elements, Element 10 (canon-grade) · the seed's Part VII (Fable synthesis, second draft). lionsberg.wiki: Set-Based Design. Open: Ore. Named once beside Element 10 with no body, no Play invoking it, and no statement of how the "last responsible moment" is judged in practice. The lineage is Lean and Integrated Project Delivery; the canon does not say so on this name.