Run N independent attempts at the same artifact, pick the strongest as a base, then walk each losing candidate for the one or two ideas worth porting into the base before verifying the result. The losers are a parts bin, not waste.
The graft step is what distinguishes this from the two neighbouring patterns it is easily confused with. pattern-throwaway-prototype builds competing sketches to make a decision and then discards them — gstack-design-shotgun’s mockup variants and mp-prototype’s throwaway sketches both end that way. pattern-cross-model-review runs several models over one artifact to find its flaws. Candidate grafting has several models each produce a whole artifact and then treats the non-winners as a source of material. The claim is that a losing design is rarely uniformly worse; it usually solved one sub-problem better, and that part is recoverable at near-zero cost once the work already exists.
Three supporting mechanisms travel with it in the evidence:
- The rubric is derived before fan-out and withheld from the candidates. They see only the task; the rubric is the picker’s tool afterwards. That keeps candidates from optimizing for the score instead of the problem.
- Each candidate returns a rationale naming what it considered and rejected, which is what makes the graft pass cheap — the alternatives are already articulated.
- A cross-judge on a different model family scores independently, and a disagreement between judge and parent is read as evidence that the rubric was ambiguous, not merely that one reader was wrong.
Isolation is a precondition: each candidate writes to its own worktree or output path, per pattern-worktree-isolation, or the attempts contaminate each other.
Applied by (backlinks)
pstack:
- pstack-arena — the pattern’s full six-phase realization (frame, fan out, cross-judge, pick, graft, verify).
- pstack-architect — Phase B runs an arena over design sketches and requires two structurally distinct candidates before synthesis.
- pstack-principle-exhaust-the-design-space — the principle that mandates competing candidates before committing.
- pstack-blast-radius — escalates to an arena for a big or wide change, merging what different models each caught.
builder-skills:
- builder-plan-arbiter — the Hybrid outcome and the Borrowed From Other Plans section of its decision memo keep the parts of losing plans worth keeping. The candidates are produced by independent agents rather than fanned out by the arbiter.
See Also
- pattern-throwaway-prototype — the discard-the-losers sibling; gstack-design-shotgun is its clearest instance.
- pattern-cross-model-review — many models over one artifact, rather than one artifact each.
- pattern-wave-parallelism — the fan-out mechanics; grafting is what happens after the wave returns.
- pattern-worktree-isolation — the precondition that keeps candidates independent.