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| Decision is obsolete, needs rethinking | Deprecate | Downgrade hypothesis, restart evaluation |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
- List all evidence files in
.fpf/evidence/ - For each evidence file:
- Read
valid_untilfrom frontmatter - Compare with current date
- Classify as FRESH, STALE, or EXPIRED
- Read
Step 2: Present Report
markdown## Evidence Freshness Report ### EXPIRED (Requires Action) | Evidence | Hypothesis | Expired | Days Overdue | |----------|------------|---------|--------------| | ev-benchmark-2024-06-15 | redis-caching | 2024-12-15 | 45 | | ev-security-2024-07-01 | auth-module | 2025-01-01 | 14 | ### STALE (Warning) | Evidence | Hypothesis | Expires | Days Left | |----------|------------|---------|-----------| | ev-loadtest-2024-10-01 | api-gateway | 2025-01-20 | 5 | ### FRESH | Evidence | Hypothesis | Expires | |----------|------------|---------| | ev-unittest-2025-01-10 | validation-lib | 2025-07-10 | ### WAIVED | Evidence | Waived Until | Rationale | |----------|--------------|-----------| | ev-perf-old | 2025-02-01 | Migration pending |
Step 3: Handle User Actions
Based on user response, perform one of:
Refresh
User: "Refresh the redis caching evidence"
- Navigate to the hypothesis in
.fpf/knowledge/L2/ - Re-run validation to create fresh evidence
Deprecate
User: "Deprecate the auth module decision"
- Move hypothesis from L2 to L1 (or L1 to L0)
- Create deprecation record:
markdown# In .fpf/evidence/deprecate-auth-module-2025-01-15.md --- id: deprecate-auth-module-2025-01-15 hypothesis_id: auth-module action: deprecate from_layer: L2 to_layer: L1 created: 2025-01-15T10:00:00Z --- # Deprecation: auth-module **Reason**: Evidence expired, technology landscape changed **Next Steps**: Run `/fpf:propose-hypotheses` to explore alternatives
- Move the hypothesis file:
bashmv .fpf/knowledge/L2/auth-module.md .fpf/knowledge/L1/auth-module.md
Waive
User: "Waive the benchmark until February"
- Create waiver record:
markdown# In .fpf/evidence/waiver-benchmark-2025-01-15.md --- id: waiver-benchmark-2025-01-15 evidence_id: ev-benchmark-2024-06-15 waived_until: 2025-02-01 created: 2025-01-15T10:00:00Z --- # Waiver: ev-benchmark-2024-06-15 **Evidence**: ev-benchmark-2024-06-15 **Hypothesis**: redis-caching **Waived Until**: 2025-02-01 **Rationale**: Migration pending, will re-run after completion **Accepted By**: User **Created**: 2025-01-15 **WARNING**: This evidence returns to EXPIRED status after 2025-02-01.
Natural Language Usage
You don't need to memorize evidence IDs. Just describe what you want.
Example Workflow
User: /fpf:decay Agent shows report with stale evidence User: Waive the benchmark until February, we'll re-run it after the migration. Agent: Creating waiver for ev-benchmark-2024-06-15 until 2025-02-01. Rationale: "Re-run after migration" [Creates .fpf/evidence/waiver-benchmark-2025-01-15.md] User: The vendor API is being discontinued. Deprecate that decision. Agent: Deprecating hypothesis-vendor-api from L2 to L1. [Moves file, creates deprecation record] Next step: Run /fpf:propose-hypotheses to explore alternatives.
WLNK Principle
A hypothesis is STALE if any of its evidence is expired (and not waived).
This is the Weakest Link (WLNK) principle: reliability = min(all evidence). One stale piece makes the whole decision questionable.
Audit Trail
All actions are logged:
| Action | What's Recorded |
|---|---|
| Deprecate | from_layer, to_layer, reason, date |
| Waive | evidence_id, until_date, rationale, date |
Files created in .fpf/evidence/:
deprecate-{hypothesis}-{date}.mdwaiver-{evidence}-{date}.md
Common Workflows
Weekly Maintenance
/fpf:decay # See what's stale # For each stale item: refresh, deprecate, or waive
Pre-Release
/fpf:decay # Check for stale decisions # Either refresh evidence or explicitly waive with documented rationale # Waiver rationales become part of release documentation
After Major Change
# Dependency update, API change, security advisory... /fpf:decay # See what's affected # Deprecate obsolete decisions # Start new hypothesis cycle for replacements
