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| Decision is obsolete, needs rethinking | Deprecate | Downgrade hypothesis, restart evaluation |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_until from frontmatter - Compare with current date - Classify as FRESH, STALE, or EXPIRED
Step 2: Present Report
## 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:
# 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:
mv .fpf/knowledge/L2/auth-module.md .fpf/knowledge/L1/auth-module.mdWaive
User: "Waive the benchmark until February"
- Create waiver record:
# 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 waivePre-Release
/fpf:decay # Check for stale decisions
# Either refresh evidence or explicitly waive with documented rationale
# Waiver rationales become part of release documentationAfter Major Change
# Dependency update, API change, security advisory...
/fpf:decay # See what's affected
# Deprecate obsolete decisions
# Start new hypothesis cycle for replacements