diff --git a/backend/src/__tests__/image-updates-routes.test.ts b/backend/src/__tests__/image-updates-routes.test.ts
index 3efc3f4a..c10fac30 100644
--- a/backend/src/__tests__/image-updates-routes.test.ts
+++ b/backend/src/__tests__/image-updates-routes.test.ts
@@ -341,6 +341,51 @@ describe('POST /api/auto-update/execute', () => {
     expect(typeof res.body.result).toBe('string');
   });
 
+  it('reports a reason-aware block message when the policy gate blocks auto-update', async () => {
+    // The Codex QA flagged this surface: a KEV- or fixable-driven block must
+    // name the matched input, never "exceed <max_severity>" (a ceiling the
+    // policy did not enforce). Force the gate to block on KEV and assert the
+    // per-stack result string names the reason and skips the update.
+    const DockerController = (await import('../services/DockerController')).default;
+    const { ImageUpdateService } = await import('../services/ImageUpdateService');
+    const { ComposeService } = await import('../services/ComposeService');
+    const PolicyEnforcement = await import('../services/PolicyEnforcement');
+
+    const containersSpy = vi.spyOn(DockerController.prototype, 'getContainersByStack')
+      .mockResolvedValue([{ Id: 'c1', Image: 'nginx:latest' }] as never);
+    const checkSpy = vi.spyOn(ImageUpdateService.getInstance(), 'checkImage')
+      .mockResolvedValue({ hasUpdate: true } as never);
+    const updateSpy = vi.spyOn(ComposeService.prototype, 'updateStack').mockResolvedValue();
+    const gateSpy = vi.spyOn(PolicyEnforcement, 'enforcePolicyPreDeploy').mockResolvedValue({
+      ok: false,
+      bypassed: false,
+      policy: { id: 1, name: 'kev-gate', max_severity: 'HIGH' },
+      violations: [{
+        imageRef: 'nginx:latest', severity: 'MEDIUM',
+        criticalCount: 0, highCount: 0, kevCount: 1, fixableCount: 0,
+        scanId: 9, reasons: ['kev'],
+      }],
+    } as never);
+    try {
+      const res = await request(app)
+        .post('/api/auto-update/execute')
+        .set('Cookie', adminCookie)
+        .send({ target: 'auto-upd-blocked' });
+      expect(res.status).toBe(200);
+      expect(res.body.result).toContain('blocked auto-update');
+      expect(res.body.result).toContain('matched known-exploited CVE (KEV)');
+      expect(res.body.result).not.toContain('exceed');
+      expect(res.body.result).not.toContain('HIGH');
+      // Blocked stacks are skipped, not updated.
+      expect(updateSpy).not.toHaveBeenCalled();
+    } finally {
+      containersSpy.mockRestore();
+      checkSpy.mockRestore();
+      updateSpy.mockRestore();
+      gateSpy.mockRestore();
+    }
+  });
+
   it('begins an update health gate after an auto-update applies', async () => {
     // Target a single stack; the route works off the running containers, so
     // stub the container probe, the update check, and the compose update, then
diff --git a/backend/src/__tests__/labels-bulk-actions.test.ts b/backend/src/__tests__/labels-bulk-actions.test.ts
index 7978133d..04918e33 100644
--- a/backend/src/__tests__/labels-bulk-actions.test.ts
+++ b/backend/src/__tests__/labels-bulk-actions.test.ts
@@ -179,7 +179,7 @@ describe('Stack Labels bulk actions', () => {
     enforcePolicyPreDeploy.mockResolvedValue({
       ok: false,
       policy: { name: 'block-criticals', max_severity: 'high' },
-      violations: [{ image: 'nginx:latest', severity: 'critical' }],
+      violations: [{ imageRef: 'nginx:latest', severity: 'CRITICAL', reasons: ['severity'] }],
     });
 
     const res = await request(app)
@@ -192,6 +192,7 @@ describe('Stack Labels bulk actions', () => {
       expect.objectContaining({ stackName: 'alpha', success: false, dryRun: true }),
     ]);
     expect(res.body.results[0].error).toContain('Policy "block-criticals" blocked deploy');
+    expect(res.body.results[0].error).toContain('matched severity threshold');
     expect(deployStack).not.toHaveBeenCalled();
     expect(invalidateNodeCaches).not.toHaveBeenCalled();
   });
diff --git a/backend/src/__tests__/policy-risk.test.ts b/backend/src/__tests__/policy-risk.test.ts
index 8d7f00e4..c163b09e 100644
--- a/backend/src/__tests__/policy-risk.test.ts
+++ b/backend/src/__tests__/policy-risk.test.ts
@@ -8,6 +8,7 @@ import {
   evaluatePolicyRisk,
   describeReason,
   describePolicyInputs,
+  summarizeBlockReasons,
   type PolicyRiskInputs,
   type RiskFinding,
 } from '../utils/policy-risk';
@@ -89,3 +90,22 @@ describe('describeReason / describePolicyInputs', () => {
     expect(describePolicyInputs(inputs())).toBe('no active inputs');
   });
 });
+
+describe('summarizeBlockReasons', () => {
+  it('names a KEV-driven block as known-exploited, not a severity threshold', () => {
+    expect(summarizeBlockReasons([{ reasons: ['kev'] }])).toBe('known-exploited CVE (KEV)');
+  });
+
+  it('joins and de-duplicates reasons across violations', () => {
+    const summary = summarizeBlockReasons([
+      { reasons: ['kev'] },
+      { reasons: ['fixable', 'kev'] },
+    ]);
+    expect(summary).toBe('known-exploited CVE (KEV) + fixable Critical/High');
+  });
+
+  it('falls back to a generic phrase when no reason was recorded', () => {
+    expect(summarizeBlockReasons([{ reasons: [] }])).toBe('scan policy conditions');
+    expect(summarizeBlockReasons([])).toBe('scan policy conditions');
+  });
+});
diff --git a/backend/src/__tests__/scheduler-service.test.ts b/backend/src/__tests__/scheduler-service.test.ts
index 696ea71a..c482d4de 100644
--- a/backend/src/__tests__/scheduler-service.test.ts
+++ b/backend/src/__tests__/scheduler-service.test.ts
@@ -921,7 +921,7 @@ describe('SchedulerService - executeUpdate', () => {
       ok: false,
       bypassed: false,
       policy: { id: 1, name: 'block-high', max_severity: 'HIGH' },
-      violations: [{ imageRef: 'nginx:1.14', severity: 'CRITICAL', criticalCount: 2, highCount: 5, scanId: 7 }],
+      violations: [{ imageRef: 'nginx:1.14', severity: 'CRITICAL', criticalCount: 2, highCount: 5, scanId: 7, reasons: ['severity'] }],
     });
 
     const svc = SchedulerService.getInstance();
@@ -934,6 +934,7 @@ describe('SchedulerService - executeUpdate', () => {
     expect(warn).toBeDefined();
     expect(warn![2]).toContain('block-high');
     expect(warn![2]).toContain('nginx:1.14');
+    expect(warn![2]).toContain('matched severity threshold');
     // The run completes (skip-and-continue), not a hard task failure.
     expect(mockUpdateScheduledTaskRun).toHaveBeenCalledWith(1, expect.objectContaining({ status: 'success' }));
   });
@@ -950,11 +951,13 @@ describe('SchedulerService - executeUpdate', () => {
       created_by: 'admin',
       last_status: null,
     });
+    // KEV-driven block (severity threshold not the trigger): the message must
+    // name the matched input, never a severity ceiling it did not enforce.
     mockEnforcePolicyPreDeploy.mockResolvedValue({
       ok: false,
       bypassed: false,
       policy: { id: 1, name: 'block-high', max_severity: 'HIGH' },
-      violations: [{ imageRef: 'nginx:1.14', severity: 'CRITICAL', criticalCount: 1, highCount: 0, scanId: 3 }],
+      violations: [{ imageRef: 'nginx:1.14', severity: 'MEDIUM', criticalCount: 0, highCount: 0, kevCount: 1, scanId: 3, reasons: ['kev'] }],
     });
 
     const svc = SchedulerService.getInstance();
@@ -966,6 +969,8 @@ describe('SchedulerService - executeUpdate', () => {
     expect(warn).toBeDefined();
     expect(warn![2]).toContain('Auto-start');
     expect(warn![2]).toContain('block-high');
+    expect(warn![2]).toContain('known-exploited CVE (KEV)');
+    expect(warn![2]).not.toContain('HIGH');
     // Auto-start does not skip-and-continue; the run is recorded as a failure.
     expect(mockUpdateScheduledTaskRun).toHaveBeenCalledWith(1, expect.objectContaining({ status: 'failure' }));
   });
diff --git a/backend/src/helpers/policyGate.ts b/backend/src/helpers/policyGate.ts
index 41f2be0e..1abd1aaf 100644
--- a/backend/src/helpers/policyGate.ts
+++ b/backend/src/helpers/policyGate.ts
@@ -9,7 +9,7 @@ import { LicenseService } from '../services/LicenseService';
 import { effectiveTier } from '../middleware/tierGates';
 import { getErrorMessage } from '../utils/errors';
 import { sanitizeForLog } from '../utils/safeLog';
-import { describeReason } from '../utils/policy-risk';
+import { summarizeBlockReasons } from '../utils/policy-risk';
 
 type BlockableAction = 'deploy' | 'update' | 'rollback';
 
@@ -24,12 +24,7 @@ export function describePolicyBlock(
   violations: PolicyViolation[],
   action: BlockableAction = 'deploy',
 ): string {
-  const reasons = new Set<string>();
-  for (const v of violations) {
-    for (const r of v.reasons) reasons.add(describeReason(r));
-  }
-  const reasonText = reasons.size > 0 ? [...reasons].join(' + ') : 'scan policy conditions';
-  return `Policy "${policy?.name ?? 'policy'}" blocked ${action}: ${violations.length} image(s) matched ${reasonText}`;
+  return `Policy "${policy?.name ?? 'policy'}" blocked ${action}: ${violations.length} image(s) matched ${summarizeBlockReasons(violations)}`;
 }
 
 // Bypass requires `?ignorePolicy=true` AND `req.user.role === 'admin'`. The
diff --git a/backend/src/routes/imageUpdates.ts b/backend/src/routes/imageUpdates.ts
index 90336000..32d9615b 100644
--- a/backend/src/routes/imageUpdates.ts
+++ b/backend/src/routes/imageUpdates.ts
@@ -15,6 +15,7 @@ import { HealthGateService } from '../services/HealthGateService';
 import { authMiddleware } from '../middleware/auth';
 import { requireAdmin } from '../middleware/tierGates';
 import { buildPolicyGateOptions } from '../helpers/policyGate';
+import { summarizeBlockReasons } from '../utils/policy-risk';
 import { isValidStackName } from '../utils/validation';
 import { sanitizeForLog } from '../utils/safeLog';
 import { getErrorMessage } from '../utils/errors';
@@ -365,7 +366,7 @@ autoUpdateRouter.post('/execute', authMiddleware, async (req: Request, res: Resp
         );
         if (!autoUpdateGate.ok) {
           const blockedImages = autoUpdateGate.violations.map((v) => v.imageRef).join(', ');
-          const blockedMsg = `Policy "${autoUpdateGate.policy?.name}" blocked auto-update: ${autoUpdateGate.violations.length} image(s) exceed ${autoUpdateGate.policy?.max_severity}${blockedImages ? ` (${blockedImages})` : ''}`;
+          const blockedMsg = `Policy "${autoUpdateGate.policy?.name}" blocked auto-update: ${autoUpdateGate.violations.length} image(s) matched ${summarizeBlockReasons(autoUpdateGate.violations)}${blockedImages ? ` (${blockedImages})` : ''}`;
           NotificationService.getInstance().dispatchAlert('warning', 'scan_finding', blockedMsg, { stackName, actor: 'system:image-update' });
           results.push(`Stack "${stackName}": ${blockedMsg}`);
           continue;
diff --git a/backend/src/routes/labels.ts b/backend/src/routes/labels.ts
index 8f4fcbe3..33d75f21 100644
--- a/backend/src/routes/labels.ts
+++ b/backend/src/routes/labels.ts
@@ -8,7 +8,7 @@ import { enforcePolicyPreDeploy } from '../services/PolicyEnforcement';
 import { authMiddleware } from '../middleware/auth';
 import { requirePermission } from '../middleware/permissions';
 import { requireAdmin, requireBody } from '../middleware/tierGates';
-import { buildPolicyGateOptions } from '../helpers/policyGate';
+import { buildPolicyGateOptions, describePolicyBlock } from '../helpers/policyGate';
 import { invalidateNodeCaches } from '../helpers/cacheInvalidation';
 import { VALID_LABEL_COLORS, MAX_LABELS_PER_NODE } from '../helpers/constants';
 import { isValidStackName } from '../utils/validation';
@@ -227,7 +227,7 @@ labelsRouter.post('/:id/action', authMiddleware, async (req: Request, res: Respo
               buildPolicyGateOptions(req),
             );
             if (!gate.ok) {
-              const blockedMsg = `Policy "${gate.policy?.name}" blocked deploy: ${gate.violations.length} image(s) exceed ${gate.policy?.max_severity}`;
+              const blockedMsg = describePolicyBlock(gate.policy, gate.violations);
               results.push({ stackName, success: false, error: blockedMsg, ...(isDryRun ? { dryRun: true } : {}) });
               continue;
             }
diff --git a/backend/src/services/BlueprintService.ts b/backend/src/services/BlueprintService.ts
index 5667ff9a..b43c0085 100644
--- a/backend/src/services/BlueprintService.ts
+++ b/backend/src/services/BlueprintService.ts
@@ -14,7 +14,7 @@ import { FileSystemService } from './FileSystemService';
 import { NodeRegistry } from './NodeRegistry';
 import { PROXY_TIER_HEADER } from './license-headers';
 import { LicenseService } from './LicenseService';
-import { assertPolicyGateAllows, buildSystemPolicyGateOptions, triggerPostDeployScan } from '../helpers/policyGate';
+import { assertPolicyGateAllows, buildSystemPolicyGateOptions, describePolicyBlock, triggerPostDeployScan } from '../helpers/policyGate';
 import { enforcePolicyForImageRefs } from './PolicyEnforcement';
 import { BlueprintAnalyzer } from './BlueprintAnalyzer';
 import { sanitizeForLog } from '../utils/safeLog';
@@ -401,7 +401,7 @@ export class BlueprintService {
             auditPath: `/api/blueprints/${blueprint.id}/apply`,
         }, undefined, true);
         if (!gate.ok) {
-            throw new Error(`Policy "${gate.policy?.name}" blocked deploy: ${gate.violations.length} image(s) exceed ${gate.policy?.max_severity}`);
+            throw new Error(describePolicyBlock(gate.policy, gate.violations));
         }
 
         const outcome = await this.applyLocalUnderLock(
diff --git a/backend/src/services/SchedulerService.ts b/backend/src/services/SchedulerService.ts
index 92ae8947..2003806e 100644
--- a/backend/src/services/SchedulerService.ts
+++ b/backend/src/services/SchedulerService.ts
@@ -22,6 +22,7 @@ import TrivyInstaller from './TrivyInstaller';
 import { CloudBackupService } from './CloudBackupService';
 import { buildSystemPolicyGateOptions } from '../helpers/policyGate';
 import { enforcePolicyPreDeploy } from './PolicyEnforcement';
+import { summarizeBlockReasons } from '../utils/policy-risk';
 
 const TRIVY_UPDATE_CHECK_INTERVAL_MS = 24 * 60 * 60 * 1000;
 const TRIVY_UPDATE_CHECK_STARTUP_DELAY_MS = 5 * 60 * 1000;
@@ -197,14 +198,15 @@ export class SchedulerService {
         );
         if (gate.ok) return;
         const images = gate.violations.map((v) => v.imageRef).join(', ');
+        const reasons = summarizeBlockReasons(gate.violations);
         this.safeDispatch(
             'warning',
             'scan_finding',
-            `${action} blocked for "${stackName}" by policy "${gate.policy?.name}": ${gate.violations.length} image(s) exceed ${gate.policy?.max_severity}${images ? ` (${images})` : ''}`,
+            `${action} blocked for "${stackName}" by policy "${gate.policy?.name}": ${gate.violations.length} image(s) matched ${reasons}${images ? ` (${images})` : ''}`,
             stackName,
         );
         throw new Error(
-            `${action} blocked by policy "${gate.policy?.name}": ${gate.violations.length} image(s) exceed ${gate.policy?.max_severity}`,
+            `${action} blocked by policy "${gate.policy?.name}": ${gate.violations.length} image(s) matched ${reasons}`,
         );
     }
 
diff --git a/backend/src/utils/policy-risk.ts b/backend/src/utils/policy-risk.ts
index bb3e50c1..c99ce7d3 100644
--- a/backend/src/utils/policy-risk.ts
+++ b/backend/src/utils/policy-risk.ts
@@ -107,6 +107,24 @@ export function describeReason(reason: PolicyBlockReason): string {
     }
 }
 
+/**
+ * De-duplicated, human-readable summary of the inputs that actually matched
+ * across a set of policy violations, joined with " + ". Used wherever a policy
+ * block is reported to a user (the gate's 409 response, thrown gate errors, and
+ * the deploy/auto-update block messages), so a KEV- or fixable-driven block
+ * never reads as a severity-threshold block. Falls back to a generic phrase
+ * when no reason was recorded (e.g. an image that could not be scanned).
+ */
+export function summarizeBlockReasons(
+    violations: ReadonlyArray<{ reasons: readonly PolicyBlockReason[] }>,
+): string {
+    const labels = new Set<string>();
+    for (const v of violations) {
+        for (const r of v.reasons) labels.add(describeReason(r));
+    }
+    return labels.size > 0 ? [...labels].join(' + ') : 'scan policy conditions';
+}
+
 /** Compact descriptor of a policy's active inputs, for log and audit lines. */
 export function describePolicyInputs(inputs: PolicyRiskInputs): string {
     const parts: string[] = [];