fix(ai): add actionable fallback for diversify prompts

apps/api/src/app/endpoints/ai/ai-agent.chat.helpers.spec.ts

@@ -73,6 +73,40 @@ describe('AiAgentChatHelpers', () => {
     expect(answer).toBe(generatedText);
   });
 
+  it('adds deterministic diversification action guidance when generated answer is unreliable', async () => {
+    const answer = await buildAnswer({
+      generateText: jest.fn().mockResolvedValue({
+        text: 'Diversify.'
+      }),
+      languageCode: 'en',
+      memory: { turns: [] },
+      portfolioAnalysis: {
+        allocationSum: 1,
+        holdings: [
+          {
+            allocationInPercentage: 0.7,
+            dataSource: DataSource.YAHOO,
+            symbol: 'AAPL',
+            valueInBaseCurrency: 7000
+          },
+          {
+            allocationInPercentage: 0.3,
+            dataSource: DataSource.YAHOO,
+            symbol: 'MSFT',
+            valueInBaseCurrency: 3000
+          }
+        ],
+        holdingsCount: 2,
+        totalValueInBaseCurrency: 10000
+      },
+      query: 'help me diversify',
+      userCurrency: 'USD'
+    });
+
+    expect(answer).toContain('Next-step allocation:');
+    expect(answer).toContain('AAPL');
+  });
+
   it('parses and persists concise response-style preference updates', () => {
     const result = resolvePreferenceUpdate({
       query: 'Remember to keep responses concise.',

apps/api/src/app/endpoints/ai/ai-agent.chat.helpers.ts

@@ -194,6 +194,8 @@ export async function buildAnswer({
     'add',
     'allocat',
     'buy',
+    'deconcentrat',
+    'diversif',
     'invest',
     'next',
     'rebalanc',
@@ -265,7 +267,7 @@ export async function buildAnswer({
 
         if (topLongShare >= 0.35) {
           fallbackSections.push(
-            'Next-step allocation: direct new capital to positions outside your top holding until concentration falls below 35%.'
+            `Next-step allocation: cap ${longHoldings[0].symbol} contribution and direct new capital to positions outside your top holding until concentration falls below 35% to improve diversification.`
           );
         } else {
           fallbackSections.push(

apps/api/src/app/endpoints/ai/ai.service.spec.ts

@@ -430,6 +430,52 @@ describe('AiService', () => {
     );
   });
 
+  it('returns deterministic diversification action guidance when generated output is unreliable', async () => {
+    portfolioService.getDetails.mockResolvedValue({
+      holdings: {
+        AAPL: {
+          allocationInPercentage: 0.665,
+          dataSource: DataSource.YAHOO,
+          symbol: 'AAPL',
+          valueInBaseCurrency: 6650
+        },
+        VTI: {
+          allocationInPercentage: 0.159,
+          dataSource: DataSource.YAHOO,
+          symbol: 'VTI',
+          valueInBaseCurrency: 1590
+        },
+        MSFT: {
+          allocationInPercentage: 0.085,
+          dataSource: DataSource.YAHOO,
+          symbol: 'MSFT',
+          valueInBaseCurrency: 850
+        }
+      }
+    });
+    redisCacheService.get.mockResolvedValue(undefined);
+    jest.spyOn(subject, 'generateText').mockResolvedValue({
+      text: 'Diversify.'
+    } as never);
+
+    const result = await subject.chat({
+      languageCode: 'en',
+      query: 'help me diversify',
+      sessionId: 'session-diversify-1',
+      userCurrency: 'USD',
+      userId: 'user-diversify-1'
+    });
+
+    expect(result.answer).toContain('Next-step allocation:');
+    expect(result.answer).toContain('AAPL');
+    expect(result.toolCalls).toEqual(
+      expect.arrayContaining([
+        expect.objectContaining({ tool: 'portfolio_analysis' }),
+        expect.objectContaining({ tool: 'risk_assessment' })
+      ])
+    );
+  });
+
   it('returns graceful failure metadata when a tool execution fails', async () => {
     dataProviderService.getQuotes.mockRejectedValue(
       new Error('market provider unavailable')