Implement a performance change

DISRESPEC-SPINE: One fact once. No filler, repeated source material, empty sections, or chat restatement; after successful creation return only clickable artifact links, except for blockers, failed creation, incomplete verification, or irreversible-action confirmation.

Two performance failure modes produce a diff that looks like a win: a number that moved on the benchmark but not in production (measured under conditions that don't match where the system is slow, or against a baseline taken under a different protocol), and a speedup that quietly broke correctness — a faster wrong answer is still a defect. This guide carries the performance discipline standalone. When runs are parallel, isolate each in its own worktree or branch so their writes stay disjoint. These are conventions the review packet inspects — nothing enforces them at edit time.

Plan the transformation first — the change plan covers baseline, waves, and rollback; this guide is the execution half. Numbers, not vibes: nothing is faster until a baseline and a final figure, under the identical protocol, say so. No number and no protocol is tinkering, not optimizing — get the target before you start.