# Skill 027

> Verify 100% specification closure before Big Bang 80/20 single-pass construction.

- Skill: `legendtkl/skill-027` (Agent Skill)
- Install (CLI): `npx skillmds@latest add legendtkl/skill-027`
- Raw SKILL.md: https://api.skillmd.com/api/skills/legendtkl/skill-027/raw
- Safety review: pending
- Works with: Claude Code, Claude.ai, OpenAI Codex
- Category: Coding & Dev Tools
- Author: legendtkl (https://skillmd.com/u/legendtkl)
- Updated: 2026-09-17
- Page: https://skillmd.com/skills/legendtkl/skill-027

---


# Big Bang 80/20: Specification Closure

## Core Concept

Specification closure is the **gate before EPIC 9 fan-out**.

No implementation begins without closure verification.

## Closure Checklist

A specification is **closed** when:

- [ ] All inputs characterized (domain, constraints, edge cases)
- [ ] All outputs specified (behavior, invariants, success criteria)
- [ ] All errors enumerated (what happens when things fail)
- [ ] All ambiguities resolved (no TBD, TODO, undefined)
- [ ] All user stories have acceptance scenarios
- [ ] SHACL validation passes

## Quick Validation

```bash
# Check for incomplete markers
grep -r "TBD\|TODO\|FIXME\|undefined" .specify/

# Validate SHACL conformance
cargo make speckit-validate
```

## Reference
See CLAUDE.md sections:
- Three Paradigms (Big Bang 80/20)
- When to Use EPIC 9
- Agents: bb80-specification-validator