diff --git a/lib/agents/QualityAssuranceAgent.ts b/lib/agents/QualityAssuranceAgent.ts
index 742bdae..e2eb0b0 100644
--- a/lib/agents/QualityAssuranceAgent.ts
+++ b/lib/agents/QualityAssuranceAgent.ts
@@ -14,8 +14,8 @@ import { BaseAgent } from './BaseAgent';
 import { AgentConfig, AgentTask, QualityReport } from './types';
 import { getBlockchain } from '../blockchain/manager';
 import { getTransportChain } from '../transport/tracker';
-import { PlantBlock } from '../blockchain/types';
-import crypto from 'crypto';
+import { PlantBlock } from '../blockchain/PlantBlock';
+import * as crypto from 'crypto';
 
 interface IntegrityCheck {
   chainId: string;
@@ -131,7 +131,7 @@ export class QualityAssuranceAgent extends BaseAgent {
    */
   private async verifyPlantChain(): Promise<IntegrityCheck> {
     const blockchain = getBlockchain();
-    const chain = blockchain.getChain();
+    const chain = blockchain.chain;
 
     let hashMismatches = 0;
     let linkBroken = 0;
@@ -205,7 +205,7 @@ export class QualityAssuranceAgent extends BaseAgent {
     const issues: DataQualityIssue[] = [];
 
     const blockchain = getBlockchain();
-    const chain = blockchain.getChain().slice(1);
+    const chain = blockchain.chain.slice(1);
 
     const seenIds = new Set<string>();
 
@@ -390,7 +390,7 @@ export class QualityAssuranceAgent extends BaseAgent {
    */
   private calculateStatistics(): DataStatistics {
     const blockchain = getBlockchain();
-    const chain = blockchain.getChain().slice(1);
+    const chain = blockchain.chain.slice(1);
 
     let completeRecords = 0;
     let partialRecords = 0;
diff --git a/lib/agents/types.ts b/lib/agents/types.ts
index a546387..5913ed2 100644
--- a/lib/agents/types.ts
+++ b/lib/agents/types.ts
@@ -160,7 +160,7 @@ export interface QualityReport {
     blockIndex: number;
     issueType: string;
     description: string;
-    severity: 'low' | 'medium' | 'high';
+    severity: 'low' | 'medium' | 'high' | 'critical';
   }[];
   lastVerifiedAt: string;
 }