Implement a feature

Features fail when the builder improvises around the spec — building past it, smuggling in "while I'm here" cleanup, or declaring done on a green suite that never exercised the new behavior. This guide adds the feature discipline on top of the base implement-task rules: build exactly what the requirements name, reuse before you invent, let nothing leave your hand unverified. These are conventions the review packet inspects — nothing enforces them at edit time.

A feature adds capability that did not exist. Repairing a defect, restructuring without a behavior change, deliberately changing existing behavior, moving between APIs, and tuning a bottleneck are different kinds with their own guides in this library.

Before you start, open references/task-template.md and copy it into your task file — it is the session frame for this work; fill it in as you go (don't reconstruct the structure from memory). It scaffolds the AC-to-change map, batch checkpoints, pasted evidence, and the self-review. The task packet itself uses the kit's task template.

Rules