version: "1.0.0" name: build description: Implement an authorized feature, fix, or refactor test-first, with designs that stay deep, isolated, and small at their public surface. Use when changing code behavior, adding modules or exports, or reshaping boundaries. Not for explanation-only requests or unresolved requirements (see align).

Build

Smallest change that proves itself, in code that's easy to change next time. A small edit stays a small edit.

Before editing

• Inspect the working tree; existing work survives. Read the real validation commands and their side effects from config.
• "Can you fix this?" → act. Ask only for an outcome-changing decision or an action outside authorization; several open, interdependent decisions → align first.
• Unknown cause or unfamiliar boundary → a small probe before choosing the design.

Loop

1. Contract: trigger → expected outcome, from the request or spec, before reading the implementation.
2. Red: one failing test per behavior slice, oracle per testing. Fails on the assertion, not a fixture.
3. Green: minimal code; tests read-only. Spec and test disagree → stop and report.
4. Refactor on green; structure and behavior changes in separate commits.
5. Prove it: doubt a green test → break the code, it must go red. Pick extra strategies (property, state model, contract, packed install) by the failure you fear, not by habit.

Defect → reproduce the symptom at its boundary first, cheapest distinguishing observation first; no reproduction → name the missing condition and keep the cause provisional. Covered, low-impact, reversible edit → no new test, still the full gate.

Design

A module hides one decision, its interface stays much smaller than what it hides, and dependencies point inward. Before shaping a module, an export, or a package boundary, load design: each rule there names the lint that backs it.

Implement and verify

• Runtime limits, retry identity, cancellation, partial failure: design them in when the workload needs them.
• Stale generated code → run the generator (check whether it syncs externally). Never hand-write or widen substitute types.
• Parallel workers: bounded scope, file ownership, a verification task each; trust their evidence, not their confidence. Serialize shared mutable state.
• In a worktree, servers take their ports from worktree-hygiene ports with a strict port; before handoff worktree-hygiene done exits 0 (--reap stops what you started). Never stop a process by name or port alone.
• Prove at the failure boundary: real filesystem for a writer, consumer install for exports, browser for focus. A fake, static render, or compile proves only itself.
• Skipped, empty, stale, or unavailable ≠ pass. Rerun checks a later change invalidated; full gate on the final state.
• Final diff: no debug output, temp files, formatter churn, or scope creep.

Handoff: resulting behavior, checks run and results, material limits; readable without earlier progress messages. Never "done" with a failing gate.