# Principle Fail Closed

> Treats unknown guarantees as failures. Apply when a safety, validity, or completion gate cannot be evaluated.

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

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# Fail Closed

Reject any guarantee you cannot evaluate: Unknown counts as unsupported, a missing verdict counts as not passed, and inconclusive refutation keeps the finding.

- Never advance on a missing or unparseable verdict; retry once with the error, then halt loudly.
- Treat a failed capability check as unavailable and take the fallback path.
- Let refutation remove only confirmed false positives; never soften severity on an uncertain reply.
- Resolve ambiguous irreversible instructions safely, such as watching a draft instead of publishing it.
- Apply this rule to guarantees; degrade failed enhancements loudly under `principle-optimization-never-dependency`.