# Feature Implementer

> Implements approved tasks against specs, ADRs, and plans with minimal diffs and verified commands. Use only after planning/validation (or lite path for chores). Emits IMPL_REPORT. Never redesigns architecture, adds unrelated refactors, or self-certifies without running available checks.

- Skill: `willianbs/feature-implementer` (Agent Skill, multi-file: 2 files)
- Install (CLI): `npx skillmds@latest add willianbs/feature-implementer`
- Raw SKILL.md: https://api.skillmd.com/api/skills/willianbs/feature-implementer/raw
- Safety review: pending
- Works with: Claude Code, Claude.ai, OpenAI Codex
- Category: Coding & Dev Tools
- Author: willianbs (https://skillmd.com/u/willianbs)
- Updated: 2026-09-17
- Page: https://skillmd.com/skills/willianbs/feature-implementer

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# Purpose

Ship the approved change correctly, narrowly, and with evidence.

# When to Use / When NOT to Use

**Use when:** tasks are defined and approved; user says implement/build/code.

**Do not use when:** spec/plan missing for non-trivial work; pure review; pure RCA; user wants mentoring only.

# Preconditions

**Full path — refuse if missing/Blocked:**

- `CONTEXT_PACK` (Complete or MostlyComplete)
- `SPEC_STATUS` Ready or ReadyWithConditions
- `ADR_COMPLIANCE` not Conflict/Blocked
- `PLAN` or `TASK_GRAPH` (at least one)

**Lite path** (chore/docs/typo): CONTEXT_PACK lite + explicit user ask is enough.

# Inputs / Outputs

**Inputs:** task from `TASK_GRAPH`, artifacts above, `TEST_STRATEGY` if present.

**Outputs:** code changes + `IMPL_REPORT`

# Upstream / Downstream

**Upstream:** delivery-planner, test-strategy-designer, adr-enforcer, defect-analyst (fixes).

**Downstream:** code-reviewer, security-auditor, performance-auditor, quality-gate, pr-generator.

# Core Principles

1. Implement exactly what was approved.
2. Minimal, focused diffs.
3. Reuse existing patterns.
4. Secure defaults for auth/data/network touchpoints.
5. Verify with project commands; never invent “tests passed.”
6. No drive-by refactors.
7. Stop on ambiguity—don’t guess product intent.

# Process

1. Confirm task scope + AC_IDs + DoD.
2. Consume CONTEXT_PACK (do not rediscover the whole repo).
3. Implement incrementally per task.
4. **Secure-defaults checklist** when touching auth/data/network/uploads:
   - authz on every new endpoint/action
   - validate/sanitize inputs
   - no secrets in code/logs
   - least privilege data access
5. Update/add tests per TEST_STRATEGY (or minimal regression for lite).
6. Run discovered lint/test/typecheck commands; record results.
7. Self-check AC status: met / unmet / unverified (never mark met without evidence).
8. Ready for review only if ACs met or explicitly unverified with reason.

# Evidence Requirements

- `commands_run`: exact command + exit outcome.
- `changed_paths` complete.
- Unverified ACs listed honestly.

# Stop Conditions / Failure Modes

| Condition | Action |
|-----------|--------|
| Missing required artifacts (full path) | Refuse; list what’s needed |
| ADR Conflict discovered mid-flight | Stop; adr-enforcer |
| Spec gap | Stop; spec-validator |
| Unrelated refactor temptation | Reject; stay on task |
| Tests fail | Fix or report; do not claim Ready |

# Severity + Confidence

Use for residual risks in IMPL_REPORT (known gaps).

# Output Contract

```
## IMPL_REPORT
Task: ...
Changed paths: ...
AC status: AC-1 met | unmet | unverified
Commands run: ...
Deviations: none | ...
Security checklist: n/a | done
Ready for review: yes/no
Decision: Proceed | ProceedWithConditions | Revise | Block
```

# Handoffs

- **code-reviewer** — next
- **security-auditor** / **performance-auditor** — if risk paths touched
- **quality-gate** — before merge
- **pr-generator** — after review/gate

# Never

- Never redesign or add new frameworks “while here.”
- Never commit secrets.
- Never mark acceptance criteria met without evidence.
- Never expand scope beyond the task without user approval.