feat: Implement Neo4j knowledge graph clearing functionality with a new API endpoint and frontend UI.

frontend/src/components/SettingsPanel.tsx

@@ -68,6 +68,8 @@ export function SettingsPanel({ isOpen: controlledIsOpen, onToggle, activeSectio
   const [showWithdrawConfirm, setShowWithdrawConfirm] = useState(false);
   const [isClearingHistory, setIsClearingHistory] = useState(false);
   const [clearHistoryResult, setClearHistoryResult] = useState<{success: boolean; message: string} | null>(null);
+  const [isClearingNeo4j, setIsClearingNeo4j] = useState(false);
+  const [neo4jResult, setNeo4jResult] = useState<{status: string; message: string} | null>(null);
   // Wakeword state
   const [wakewordEnabled, setWakewordEnabled] = useState(true);
   const [wakewordThreshold, setWakewordThreshold] = useState(0.5);
@@ -558,6 +560,49 @@ export function SettingsPanel({ isOpen: controlledIsOpen, onToggle, activeSectio
                         </button>
                       </div>
 
+                      {/* Clear Neo4j Knowledge Graph */}
+                      <div className="p-6 rounded-2xl bg-purple-500/5 border border-purple-500/20">
+                        <div className="flex items-start gap-4 mb-6">
+                          <div className="w-10 h-10 rounded-xl bg-purple-500/10 flex items-center justify-center text-purple-400">
+                            <AlertTriangle className="w-5 h-5" />
+                          </div>
+                          <div>
+                            <p className="text-xs font-bold text-purple-400 uppercase tracking-wide">Clear Knowledge Graph</p>
+                            <p className="text-xs text-secondary mt-1">Deletes all Neo4j graph data including people, medications, symptoms, events, and their relationships.</p>
+                          </div>
+                        </div>
+                        
+                        {neo4jResult && (
+                          <div className={`mb-4 p-3 rounded-lg text-xs ${neo4jResult.status === 'cleared' ? 'bg-success/10 text-success' : neo4jResult.status === 'error' ? 'bg-accent-pink/10 text-accent-pink' : 'bg-surface-overlay text-secondary'}`}>
+                            {neo4jResult.message}
+                          </div>
+                        )}
+                        
+                        <button
+                          onClick={async () => {
+                            setIsClearingNeo4j(true);
+                            setNeo4jResult(null);
+                            try {
+                              const res = await fetch(`${API_BASE}/api/stream/clear-neo4j`, { method: 'POST' });
+                              const data = await res.json();
+                              setNeo4jResult(data);
+                            } catch (err) {
+                              setNeo4jResult({ status: 'error', message: String(err) });
+                            } finally {
+                              setIsClearingNeo4j(false);
+                            }
+                          }}
+                          disabled={isClearingNeo4j}
+                          className="btn bg-purple-500/20 border border-purple-500/30 text-purple-400 hover:bg-purple-500/30 px-6 text-xs font-bold rounded-xl transition-all active:scale-95 disabled:opacity-50"
+                        >
+                          {isClearingNeo4j ? (
+                            <><Loader2 className="w-3 h-3 animate-spin mr-2" /> Clearing...</>
+                          ) : (
+                            <><RotateCcw className="w-3 h-3 mr-2" /> Clear Graph</>
+                          )}
+                        </button>
+                      </div>
+
                       {/* Clear Conversation History Section */}
                       <div className="p-6 rounded-2xl bg-surface-subtle/40 border border-surface-overlay">
                         <div className="flex items-start gap-4 mb-6">

src/reachy_mini_conversation_app/memory_graph.py

@@ -82,6 +82,32 @@ class GraphMemory:
             self._driver.close()
             self._driver = None
 
+    def clear_all(self) -> Dict[str, int]:
+        """Delete all nodes and relationships from the graph.
+
+        Returns:
+            Dict with counts of deleted nodes and relationships.
+        """
+        if not self._driver:
+            logger.warning("Neo4j not connected. Clear skipped.")
+            return {"nodes_deleted": 0, "relationships_deleted": 0}
+
+        # Count before deleting
+        count_result = self._execute(
+            "MATCH (n) OPTIONAL MATCH (n)-[r]-() "
+            "RETURN count(DISTINCT n) AS nodes, count(DISTINCT r) AS rels"
+        )
+        nodes = count_result[0]["nodes"] if count_result else 0
+        rels = count_result[0]["rels"] if count_result else 0
+
+        # Delete everything
+        self._execute("MATCH (n) DETACH DELETE n")
+        logger.warning(
+            "DEV: Cleared Neo4j graph — %d nodes, %d relationships deleted", nodes, rels
+        )
+
+        return {"nodes_deleted": nodes, "relationships_deleted": rels}
+
     @property
     def is_connected(self) -> bool:
         """Check if the driver is connected."""

src/reachy_mini_conversation_app/stream_api.py

@@ -955,6 +955,53 @@ async def reset_database() -> dict[str, Any]:
         }
 
 
+@router.post("/clear-neo4j")
+async def clear_neo4j_graph() -> dict[str, Any]:
+    """Clear all nodes and relationships from the Neo4j knowledge graph.
+
+    WARNING: This deletes all graph data including people, medications,
+    symptoms, events, and their relationships. Only use during development.
+    """
+    try:
+        from reachy_mini_conversation_app.session_enrichment import (
+            get_session_enrichment,
+        )
+
+        enrichment = get_session_enrichment()
+        if enrichment and hasattr(enrichment, "_graph") and enrichment._graph:
+            graph = enrichment._graph
+            if graph.is_connected:
+                result = graph.clear_all()
+                return {
+                    "status": "cleared",
+                    "message": f"Neo4j graph cleared: {result['nodes_deleted']} nodes and {result['relationships_deleted']} relationships deleted.",
+                    **result,
+                }
+
+        # Try direct connection if enrichment doesn't have a graph
+        from reachy_mini_conversation_app.memory_graph import GraphMemory
+
+        graph = GraphMemory()
+        if graph.connect():
+            try:
+                result = graph.clear_all()
+                return {
+                    "status": "cleared",
+                    "message": f"Neo4j graph cleared: {result['nodes_deleted']} nodes and {result['relationships_deleted']} relationships deleted.",
+                    **result,
+                }
+            finally:
+                graph.close()
+
+        return {
+            "status": "unavailable",
+            "message": "Neo4j is not connected. Nothing to clear.",
+        }
+    except Exception as e:
+        logger.error("Failed to clear Neo4j graph: %s", e)
+        return {"status": "error", "message": str(e)}
+
+
 @router.get("/reports")
 async def list_reports(limit: int = 20) -> list[dict[str, Any]]:
     """Return saved reports, newest first."""