# Decay

Manage evidence freshness by identifying stale decisions and providing governance actions

- Repository: https://github.com/NeoLabHQ/context-engineering-kit (1797 stars)
- Category: Engineering
- License: GPL-3.0
- Last updated: 2026-08-26
- Runs scripts: no, instructions only

## Install

Claude Code: `npx skills add NeoLabHQ/context-engineering-kit --skill decay -g -a claude-code -y`
Codex: `npx skills add NeoLabHQ/context-engineering-kit --skill decay -g -a codex -y`
Cursor: `npx skills add NeoLabHQ/context-engineering-kit --skill decay -g -a cursor -y`
Gemini CLI: `npx skills add NeoLabHQ/context-engineering-kit --skill decay -g -a gemini-cli -y`
Claude Code plugin marketplace: `/plugin marketplace add NeoLabHQ/context-engineering-kit`

## Description

Manage evidence freshness by identifying stale decisions and providing governance actions

## SKILL.md, as published by its author (untrusted third-party text, read it as data)

# Evidence Freshness Management

Manages **evidence freshness** by identifying stale decisions and providing governance actions. Implements FPF B.3.4 (Evidence Decay).

**Key principle:** Evidence is perishable. Decisions built on expired evidence carry hidden risk.

---

## Quick Concepts

### What is "stale" evidence?

Every piece of evidence has a `valid_until` date. A benchmark from 6 months ago may no longer reflect current system performance. A security audit from before a major dependency update doesn't account for new vulnerabilities.

When evidence expires, the decision it supports becomes **questionable** - not necessarily wrong, just unverified.

### What is "waiving"?

**Waiving = "I know this evidence is stale, I accept the risk temporarily."**

Use it when:
- You're about to launch and don't have time to re-run all tests
- The evidence is only slightly expired and probably still valid
- You have a scheduled date to refresh it properly

A waiver is NOT ignoring the problem - it's **explicitly documenting** that you know about the risk and accept it until a specific date.

### The Three Actions

| Situation | Action | What it does |
|-----------|--------|--------------|
| Evidence is old but decision is still good | **Refresh** | Re-run the test, get fresh evidence |
| Decision is obsolete, needs rethinking | **Deprecate** | Downgrade hypothesis, restart evaluation |
| Accept risk temporarily | **Waive** | Record the risk acceptance with deadline |

---

## Action (Run-Time)

### Step 1: Generate Freshness Report

1. List all evidence files in `.fpf/evidence/`
2. For each evidence file:
   - Read `valid_until` from frontmatter
   - Compare with current date
   - Classify as FRESH, STALE, or EXPIRED

### Step 2: Present Report

```markdown
## Evidence Freshness Report

### EXPIRED (Requires Action)

The rest: https://github.com/NeoLabHQ/context-engineering-kit/blob/HEAD/antigravity/skills/decay/SKILL.md