decay — Claude Code skill: evidence freshness management
Checks expiry dates on evidence files in .fpf/evidence/ and offers refresh, deprecate or waive actions for decisions built on stale data.
npx skills add NeoLabHQ/context-engineering-kit --skill decay -a claude-codeWhat decay does
The skill implements the Evidence Decay principle from FPF B.3.4. Every evidence file carries a valid_until field in its frontmatter. The skill compares that date against today and sorts entries into FRESH, STALE, EXPIRED and WAIVED. The report comes out as tables, with each piece of evidence listed next to the hypothesis it supports.
Then you pick an action. Refresh re-runs the validation to produce new evidence. Deprecate moves a hypothesis down a layer (from L2 to L1, or L1 to L0) and records why. Waive documents that you know the evidence is stale and accept the risk until a set date. Every action leaves a file in .fpf/evidence/: deprecate-{hypothesis}-{date}.md or waiver-{evidence}-{date}.md.
It follows the weakest link rule. One expired piece of evidence without a waiver marks the whole hypothesis STALE. So the skill earns its place in projects where decisions rest on benchmarks, audits or load tests that carry a date. Point it at a repo without a .fpf/ structure and it finds nothing.
What it helps with
- spot decisions resting on expired evidence
- re-run validation to get fresh evidence for a hypothesis
- downgrade an obsolete hypothesis a layer and log the reason
- record a temporary risk acceptance with a deadline
- sweep every evidence file before a release or after a dependency update
Example prompts for the agent
- /fpf:decay
- Refresh the redis caching evidence
- Deprecate the auth module decision, the technology changed
How to install decay
1Skills CLI (Vercel)
npx skills add NeoLabHQ/context-engineering-kit --skill decay -a claude-code2Manually: put the files in place
~/.claude/skills/decay/SKILL.mdCopy the whole skill folder; for one project use .claude/skills/decay/
1Skills CLI (Vercel)
npx skills add NeoLabHQ/context-engineering-kit --skill decay -a codex2Manually: put the files in place
.agents/skills/decay/SKILL.mdFor all projects use ~/.agents/skills/
1Skills CLI (Vercel)
npx skills add NeoLabHQ/context-engineering-kit --skill decay -a cursor2Manually: put the files in place
.cursor/skills/decay/SKILL.mdCursor also reads .agents/skills/ and .claude/skills/
1GitHub CLI
gh skill install NeoLabHQ/context-engineering-kit decay2Manually: put the files in place
.github/skills/decay/SKILL.md1Skills CLI (Vercel)
npx skills add NeoLabHQ/context-engineering-kit --skill decay -a gemini-cli2Platform CLI
gemini skills install https://github.com/NeoLabHQ/context-engineering-kit --path skills/decayManually: put the files in place
.devin/skills/decay/SKILL.mdThe legacy .windsurf/skills/ path still works
Skills CLI (Vercel)
npx skills add NeoLabHQ/context-engineering-kit --skill decay -a opencodeClaude.ai
Zip the folder and upload it in Settings → Capabilities → Skills
Step by step, with commands for each platform: How to install skills in Claude Code: five ways
Questions about decay
How do I install decay in Claude?
Run npx skills add NeoLabHQ/context-engineering-kit --skill decay -a claude-code. The skill lands in ~/.claude/skills/decay/SKILL.md.
What does decay do?
It builds a freshness report from .fpf/evidence/, flags expired entries and offers three actions: refresh, deprecate or waive.
What does the skill need to work?
A .fpf/evidence/ directory with evidence files that carry valid_until in their frontmatter. Without that structure the report stays empty.
