implement-feature

Implement Feature Skill

Full workflow: CONTRIBUTION_GUIDE.md

Pre-Implementation Checklist

1. Verify context: TZ='America/New_York' date && git status
2. Check/create GitHub issue: gh issue list --state open
3. Check research registry if implementing a technique

Hard Design Decisions — Constraint-Divergent Design

When the problem has multiple plausible approaches (e.g., "event-driven or polling?", "synchronous vs queue-based?", "monolithic helper vs split modules?"), do not generate the same solution three times with different variable names. Instead, articulate 2–3 distinct constraints first, then sketch one solution per constraint and compare.

Anchor constraints in real tradeoffs:

• "minimize allocations" vs "minimize lines of code" vs "minimize external deps"
• "lowest latency" vs "lowest memory" vs "easiest to test"
• "fewest moving parts" vs "easiest to extend" vs "matches existing pattern X"

Three constraints that each eliminate ~70% of the solution space leave you searching ~2.7% of it — a focused region, not blind sampling. (Pattern adapted from itigges22/ATLAS PlanSearch; the math is theirs.)

Apply this discipline only for genuinely-multivalent decisions. Indicators:

• Multiple plausible architectures where reviewers would reasonably disagree
• A wrong choice would be expensive to reverse (data-shape migration, public API surface, cross-package boundary)
• You catch yourself thinking "I'll just pick one and see what review says" — pick deliberately, by constraint, instead

Out of scope: routine work where the approach is dictated by canonical paths or existing patterns. Don't over-apply.

Implementation Process

Phase 1: Interface First

// Define interface FIRST
interface IFeature {
  method(input: Input): Promise<Result<Output, Error>>;
}