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+# Position Format Validation: Registry vs Simulator
+
+## Overview
+
+Analysis of position data flow from simulator → registry_bridge → fleet registry identified a **coordinate system mismatch** between simulator and registry coordinate systems.
+
+## Registry's Expected Position Format
+
+### Database Schema (SQLite)
+```sql
+CREATE TABLE IF NOT EXISTS nodes (
+    mac              TEXT PRIMARY KEY,
+    ...
+    pos_x            REAL    NOT NULL DEFAULT 0,
+    pos_y            REAL    NOT NULL DEFAULT 0,
+    pos_z            REAL    NOT NULL DEFAULT 0,
+    ...
+);
+```
+
+### Registry Coordinate System (from `internal/fleet/registry.go`)
+```go
+type RoomConfig struct {
+    Width   float64 // meters, X axis
+    Depth   float64 // meters, Z axis
+    Height  float64 // meters, Y axis
+    OriginX float64
+    OriginZ float64
+}
+```
+
+**Registry coordinate convention:**
+- `pos_x` = width (horizontal X axis)
+- `pos_y` = height (vertical Y axis)
+- `pos_z` = depth (horizontal Z axis)
+
+### Registry API Interface
+```go
+type NodeRegistry interface {
+    SetNodePosition(mac string, x, y, z float64) error
+    AddVirtualNode(mac, name string, x, y, z float64) error
+}
+```
+
+## Simulator's Position Format
+
+### Simulator Data Structure
+```go
+type Point struct{ X, Y, Z float64 }
+```
+
+### Simulator Coordinate System (from `internal/simulator/space.go`)
+DefaultSpace room bounds:
+```go
+Room{
+    MinX: 0, MinY: 0, MinZ: 0,
+    MaxX: 6, MaxY: 5, MaxZ: 2.5,  // 6m × 5m × 2.5m room
+}
+```
+
+**Simulator coordinate convention:**
+- `Point.X` = width (horizontal X axis)
+- `Point.Y` = depth (horizontal Y axis)
+- `Point.Z` = height (vertical Z axis)
+
+### VirtualNodeState Storage
+```go
+type VirtualNodeState struct {
+    ID       string
+    Name     string
+    Position Point     // {X, Y, Z}
+    ...
+}
+```
+
+## Format Mismatch Identified
+
+### Coordinate System Difference
+
+| Axis | Simulator (Point) | Registry (pos_*) | Match? |
+|------|-------------------|------------------|--------|
+| X    | width             | width            | ✅     |
+| Y    | depth             | height           | ❌     |
+| Z    | height            | depth            | ❌     |
+
+**The Y and Z axes are swapped between the two systems!**
+
+### Current Registry Bridge Implementation
+
+From `internal/simulator/registry_bridge.go`:
+```go
+func (b *FleetRegistryBridge) SyncToRegistry(registry RegistryNodeAdapter) error {
+    for _, node := range nodes {
+        mac := b.virtualMAC(node.ID)
+        pos := positions[node.ID]  // Point{X, Y, Z}
+        
+        // Direct field access - NO COORDINATE TRANSFORMATION
+        registry.AddVirtualNode(mac, node.Name, pos.X, pos.Y, pos.Z)
+        //                                     ^^^^^^^^^^^^^^^^
+        //                                     Y and Z are NOT swapped!
+    }
+}
+```
+
+**This is incorrect!** The simulator's Y (depth) and Z (height) are being passed directly to the registry, which expects Y as height and Z as depth.
+
+## Required Transformations
+
+### Coordinate Mapping
+
+To correctly transform simulator positions to registry positions:
+
+```go
+// Simulator Point → Registry position
+registry_x = simulator_point.X     // width → width (no change)
+registry_y = simulator_point.Z     // height → height (swapped!)
+registry_z = simulator_point.Y     // depth → depth (swapped!)
+```
+
+### Corrected Implementation
+
+```go
+func (b *FleetRegistryBridge) SyncToRegistry(registry RegistryNodeAdapter) error {
+    for _, node := range nodes {
+        mac := b.virtualMAC(node.ID)
+        pos := positions[node.ID]
+        
+        // CORRECT: Swap Y and Z for registry coordinate system
+        registry.AddVirtualNode(mac, node.Name, 
+            pos.X,    // width (no change)
+            pos.Z,    // height (was Point.Z)
+            pos.Y,    // depth (was Point.Y)
+        )
+    }
+}
+```
+
+### Example Transformation
+
+**Simulator position:** Point{X: 3.0, Y: 2.5, Z: 1.5}
+- X=3.0m (width position)
+- Y=2.5m (depth position)
+- Z=1.5m (height position)
+
+**Registry position (corrected):** pos_x=3.0, pos_y=1.5, pos_z=2.5
+- pos_x=3.0m (width position) ✅
+- pos_y=1.5m (height position) ✅
+- pos_z=2.5m (depth position) ✅
+
+**Registry position (current implementation):** pos_x=3.0, pos_y=2.5, pos_z=1.5
+- pos_x=3.0m (width position) ✅
+- pos_y=2.5m (INCORRECT - treating depth as height!)
+- pos_z=1.5m (INCORRECT - treating height as depth!)
+
+## Impact Analysis
+
+### Current Behavior
+- Virtual nodes from simulator are written to registry with **swapped Y/Z coordinates**
+- Registry interprets simulator's depth (Y) as height
+- Registry interprets simulator's height (Z) as depth
+- This affects:
+  - Fusion engine positioning calculations
+  - Coverage optimization algorithms
+  - Any registry consumers that use 3D positions
+
+### Risk Assessment
+- **High risk**: Coordinate system mismatch causes incorrect spatial positioning
+- **Affected systems**: Fusion engine, coverage optimization, position-based tracking
+- **Data corruption risk**: Existing registry entries may have incorrect coordinates
+
+## Recommendations
+
+1. **Immediate**: Fix coordinate transformation in `registry_bridge.go`
+2. **Data cleanup**: Script to correct existing registry node positions
+3. **Testing**: Add integration tests validating coordinate transformation
+4. **Documentation**: Document coordinate systems in both codebases
+
+## Related Files
+
+- `mothership/internal/simulator/registry_bridge.go` - Bridge implementation (needs fix)
+- `mothership/internal/simulator/space.go` - Simulator coordinate system
+- `mothership/internal/fleet/registry.go` - Registry coordinate system
+- `mothership/internal/simulator/virtual_state.go` - Virtual node storage