diff --git a/docs/design/DECISION_MODEL_v1.0.md b/docs/design/DECISION_MODEL_v1.0.md
index 9ff42ef01..7e8600c3d 100644
--- a/docs/design/DECISION_MODEL_v1.0.md
+++ b/docs/design/DECISION_MODEL_v1.0.md
@@ -198,9 +198,9 @@ For every decision:
 
 ## Validation Scenarios
 
-Before freezing Decision Model v1.0, validate against three real scenarios:
+Before freezing Decision Model v1.0, validate against diverse scenarios:
 
-### Scenario 1: Road Crack
+### Scenario 1: Road Crack (Maintenance)
 
 | Layer | Example |
 |-------|---------|
@@ -211,7 +211,9 @@ Before freezing Decision Model v1.0, validate against three real scenarios:
 | Decision | "Prioritize inspection within 14 days" |
 | Business Impact | Risk: High, Cost: $50k avoided, Time: 14 days, Opportunity: Plan with nearby works |
 
-### Scenario 2: Damaged Facade
+**Decision type:** Maintenance — "Repair now or later?"
+
+### Scenario 2: Damaged Facade (Safety)
 
 | Layer | Example |
 |-------|---------|
@@ -222,7 +224,9 @@ Before freezing Decision Model v1.0, validate against three real scenarios:
 | Decision | "Immediate safety inspection required" |
 | Business Impact | Risk: Critical, Cost: $200k liability, Time: 24 hours, Opportunity: Prevent injury |
 
-### Scenario 3: Broken Road Sign
+**Decision type:** Safety — "Act immediately?"
+
+### Scenario 3: Broken Road Sign (Compliance)
 
 | Layer | Example |
 |-------|---------|
@@ -233,7 +237,114 @@ Before freezing Decision Model v1.0, validate against three real scenarios:
 | Decision | "Replace sign within 48 hours" |
 | Business Impact | Risk: Medium, Cost: $5k fine avoided, Time: 48 hours, Opportunity: Standard replacement |
 
-**Pass criteria:** Same Decision Object works for all three without modification.
+**Decision type:** Compliance — "Does this violate requirements?"
+
+### Scenario 4: Vegetation Blocking Sight (Risk Reduction)
+
+| Layer | Example |
+|-------|---------|
+| Reality | Mobile photo of overgrown vegetation |
+| Observation | "Vegetation 80cm high, blocking sight line" |
+| Evidence | 2 observations over 3 months + growth trend |
+| Finding | "Gradual degradation of sight lines at intersection" |
+| Decision | "Schedule vegetation removal within 30 days" |
+| Business Impact | Risk: Medium, Cost: $15k avoided, Time: 30 days, Opportunity: Coordinate with seasonal maintenance |
+
+**Decision type:** Risk reduction — "Gradual deterioration requiring planned action"
+
+### Scenario 5: Parking Area Wear (Investment Priority)
+
+| Layer | Example |
+|-------|---------|
+| Reality | Multiple mobile photos of parking area |
+| Observation | "Surface wear, potholes, faded markings" |
+| Evidence | 5 observations + usage data + weather exposure |
+| Finding | "Multiple minor issues collectively indicate need for resurfacing" |
+| Decision | "Include in next year's maintenance budget" |
+| Business Impact | Risk: Low, Cost: $100k investment, Time: 6 months, Opportunity: Improve user satisfaction |
+
+**Decision type:** Investment priority — "Multiple small observations motivating larger decision"
+
+### Scenario 6: Cosmetic Scratch (No Action)
+
+| Layer | Example |
+|-------|---------|
+| Reality | Mobile photo of road sign |
+| Observation | "Minor cosmetic scratches, 5% of surface" |
+| Evidence | 1 observation, no functional impact |
+| Finding | "Normal wear and tear, no safety or compliance impact" |
+| Decision | "No action recommended. Continue monitoring." |
+| Business Impact | Risk: None, Cost: $0, Time: Annual review, Opportunity: None |
+
+**Decision type:** No action — "Conscious decision to wait"
+
+### Scenario 7: Mixed Evidence Sources
+
+| Layer | Example |
+|-------|---------|
+| Reality | Mobile photo + sensor data + weather API |
+| Observation | "Water pooling, 3cm depth, after rainfall" |
+| Evidence | Photo + rain sensor + historical flooding data + GIS topography |
+| Finding | "Drainage inadequate, recurring flooding risk" |
+| Decision | "Inspect drainage system, prioritize if flooding recurs" |
+| Business Impact | Risk: Medium, Cost: $30k avoided, Time: 14 days, Opportunity: Permanent fix during dry season |
+
+**Decision type:** Complex — "Multiple evidence sources converging"
+
+---
+
+## Decision Invariance Test
+
+For each scenario, verify:
+
+| Question | Pass Criteria |
+|----------|---------------|
+| Same Decision Object structure? | All 7 fields present |
+| Any field added? | No new fields needed |
+| Any field always empty? | No field unused across scenarios |
+| Any field meaning different things? | Each field has consistent meaning |
+
+**Fail criteria:** If any question answers "no", the model needs revision.
+
+---
+
+## Evidence Variation Test
+
+| Evidence Type | Scenario | Pass |
+|---------------|----------|------|
+| Single image | Scenario 3 | ✅ |
+| Multiple images | Scenario 1 | ✅ |
+| Video + GPS | Scenario 2 | ✅ |
+| Historical observations | Scenario 4 | ✅ |
+| External data (weather, traffic) | Scenario 7 | ✅ |
+| Mixed sources | Scenario 7 | ✅ |
+
+**Pass criteria:** Decision Object structure unchanged regardless of evidence type.
+
+---
+
+## Decision Quality Gate
+
+Before displaying any decision to the user:
+
+- [ ] At least one verifiable evidence chain exists
+- [ ] Confidence is motivated (not arbitrary)
+- [ ] Recommended action exists OR conscious "no action" decision
+- [ ] Explainability chain works (can click back to observations)
+
+---
+
+## Pass Criteria
+
+**Decision Model v1.0 is validated when:**
+
+1. All 7 scenarios produce valid Decision Objects
+2. Decision Invariance Test passes
+3. Evidence Variation Test passes
+4. Decision Quality Gate passes for all scenarios
+5. "No action" scenario works correctly
+
+**Status:** ⏳ Pending validation
 
 ---