# Under Shirt

> Use Under Shirt when a catastrophic failure is possible and the system needs a last-resort failsafe that prevents total collapse, leaving it barely functional instead of dead.

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

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# Under Shirt

Survive the unsurvivable by the thinnest margin.

## Overview

Use Under Shirt when a catastrophic failure is possible and the system needs a last-resort failsafe that prevents total collapse, leaving it barely functional instead of dead.

This is the secondary Codex compatibility rendering of a hybrid battle-chip pattern with a shipping-now execution model.

Canonical chip family: Under Shirt
Codex shelf: Defense and Recovery
Provider target: Codex compatibility surface.

## When To Use

- Before deploying a high-risk change that could catastrophically break the system, wire up a last-resort rollback or kill switch.
- A service is in a fragile state and needs a failsafe that prevents total data loss or full outage.
- Setting up incident response and needing a dead-man switch that keeps the system barely functional through worst-case scenarios.

## Workflow

1. Identify the catastrophic failure path — the exact scenario where total collapse is possible.
2. Install a minimal survival mechanism at the critical point: a rollback checkpoint, circuit breaker, or data snapshot.
3. Verify the failsafe triggers correctly under simulated lethal conditions and document that it exists.

## Deliverables

- A one-shot failsafe mechanism that prevents total system collapse.
- Documentation marking the failsafe's location, trigger condition, and that it is a last-resort safety net.

## Guardrails

- This is a one-time, last-resort safety net — not a defense strategy. If you rely on it repeatedly, fix the underlying problem.
- The failsafe must leave the system in a minimum viable state, not silently corrupted.
- Never let the existence of an Under Shirt failsafe justify riskier deployments.

## Default Invocation

Use Under Shirt to install a last-resort failsafe that prevents total catastrophic collapse, leaving the system barely functional if the worst case happens.