diff --git a/src/modules/investments/portfolio/application/portfolio.service.spec.ts b/src/modules/investments/portfolio/application/portfolio.service.spec.ts
index 448e2e6..70166da 100644
--- a/src/modules/investments/portfolio/application/portfolio.service.spec.ts
+++ b/src/modules/investments/portfolio/application/portfolio.service.spec.ts
@@ -218,6 +218,18 @@ describe('persistent portfolio projection', () => {
     expect(snapshot.structure.currencies[0].totalValue).toBe('121.49');
   });
 
+  // Test intent: a corrupted Json payload must fail loudly instead of being spread into the API response.
+  it('rejects a stored snapshot payload without the persisted shape', async () => {
+    repository.read.mockResolvedValue({
+      membershipAt,
+      membershipRevision: 1,
+      accounts: [{ accountId: 'a', name: 'A', type: 'BROKERAGE', openedOn: null,
+        portfolio: { payload: { positions: 'broken' }, fetchedAt: membershipAt, dataRevision: 1 } }],
+      work: [],
+    });
+    await expect(service.read('user', 'all')).rejects.toThrow('Corrupted portfolio snapshot payload');
+  });
+
   it('does not turn a missing account snapshot into aggregate zero; summaries stay independent', async () => {
     const snapshot: PortfolioDto = {
       lastSuccessfulAt: membershipAt.toISOString(),
diff --git a/src/modules/investments/portfolio/application/portfolio.service.ts b/src/modules/investments/portfolio/application/portfolio.service.ts
index b001098..43d5229 100644
--- a/src/modules/investments/portfolio/application/portfolio.service.ts
+++ b/src/modules/investments/portfolio/application/portfolio.service.ts
@@ -4,6 +4,8 @@ import {
 } from '@nestjs/common';
 import { randomUUID } from 'node:crypto';
 
+import type { Prisma } from '../../../../../generated/prisma/client';
+
 import { StructuredLogger } from '../../../../common/logging/structured-logger.service';
 import { isTbankErrorCode, TbankErrorCode } from '../../../../integrations/tbank/tbank-error-code';
 import {
@@ -26,6 +28,7 @@ import { sumMoneyByCurrency } from '../domain/portfolio-totals';
 import {
   portfolioFreshForMs,
   PortfolioRepository,
+  portfolioSnapshot,
   portfolioWorkKey,
 } from '../infrastructure/portfolio.repository';
 import { mapPortfolio } from '../infrastructure/tbank-portfolio.mapper';
@@ -88,18 +91,7 @@ export class PortfolioService {
           type: account.type,
           openedOn: account.openedOn,
           snapshot: account.portfolio
-            ? {
-                ...(account.portfolio.payload as unknown as PortfolioDto),
-                positions: (account.portfolio.payload as unknown as PortfolioDto).positions.map((position) => ({
-                  ...position,
-                  sector: position.sector ?? null,
-                  issuer: position.issuer ?? null,
-                })),
-                lastSuccessfulAt: account.portfolio.fetchedAt.toISOString(),
-                isStale:
-                  Date.now() - account.portfolio.fetchedAt.valueOf() >=
-                  portfolioFreshForMs,
-              }
+            ? savedSnapshot(account.portfolio)
             : null,
           meta: investmentResourceMeta({
             resourceKey: `portfolio/${encodeURIComponent(account.accountId)}`,
@@ -326,3 +318,17 @@ export class PortfolioService {
     return mapPortfolio(upstream, money, savedMetadata, lastSuccessfulAt, classifications);
   }
 }
+
+function savedSnapshot(saved: { fetchedAt: Date; payload: Prisma.JsonValue }): PortfolioDto {
+  const snapshot = portfolioSnapshot(saved.payload);
+  return {
+    ...snapshot,
+    positions: snapshot.positions.map((position) => ({
+      ...position,
+      sector: position.sector ?? null,
+      issuer: position.issuer ?? null,
+    })),
+    lastSuccessfulAt: saved.fetchedAt.toISOString(),
+    isStale: Date.now() - saved.fetchedAt.valueOf() >= portfolioFreshForMs,
+  };
+}
diff --git a/src/modules/investments/portfolio/infrastructure/portfolio.repository.ts b/src/modules/investments/portfolio/infrastructure/portfolio.repository.ts
index 2d5cfd3..3be02a0 100644
--- a/src/modules/investments/portfolio/infrastructure/portfolio.repository.ts
+++ b/src/modules/investments/portfolio/infrastructure/portfolio.repository.ts
@@ -200,3 +200,16 @@ export class PortfolioRepository {
 export function portfolioWorkKey(accountId: string): string {
   return `portfolio:${JSON.stringify(accountId)}`;
 }
+
+// Json payload is written only by publish(); a shape check turns corruption into an explicit 500.
+export function portfolioSnapshot(value: Prisma.JsonValue): PortfolioDto {
+  const snapshot = value as null | Partial<PortfolioDto>;
+  if (
+    !Array.isArray(snapshot?.positions) ||
+    !Array.isArray(snapshot.totalsByCurrency) ||
+    !Array.isArray(snapshot.cashBalances)
+  ) {
+    throw new Error('Corrupted portfolio snapshot payload');
+  }
+  return snapshot as PortfolioDto;
+}
diff --git a/src/modules/investments/tbank-sync/tbank-sync.repository.spec.ts b/src/modules/investments/tbank-sync/tbank-sync.repository.spec.ts
new file mode 100644
index 0000000..bb938a4
--- /dev/null
+++ b/src/modules/investments/tbank-sync/tbank-sync.repository.spec.ts
@@ -0,0 +1,14 @@
+jest.mock('../../../prisma/prisma.service', () => ({
+  PrismaService: class {},
+}));
+
+import { screenIntent } from './tbank-sync.repository';
+
+describe('screen sync intent', () => {
+  it('restores a persisted intent and rejects a corrupted one', () => {
+    const intent = { now: '2026-11-02T00:00:00.000Z', scope: { screen: 'accounts' } };
+    expect(screenIntent(intent)).toEqual(intent);
+    expect(() => screenIntent({ source: 'hourly' })).toThrow('Corrupted screen sync intent');
+    expect(() => screenIntent(null)).toThrow('Corrupted screen sync intent');
+  });
+});
diff --git a/src/modules/investments/tbank-sync/tbank-sync.repository.ts b/src/modules/investments/tbank-sync/tbank-sync.repository.ts
index dbeab81..8ccb815 100644
--- a/src/modules/investments/tbank-sync/tbank-sync.repository.ts
+++ b/src/modules/investments/tbank-sync/tbank-sync.repository.ts
@@ -8,6 +8,15 @@ import type { InvestmentScreenDto } from './tbank-sync.dto';
 
 import { PrismaService } from '../../../prisma/prisma.service';
 export type ScreenIntent = { now: string; scope: InvestmentScreenDto };
+
+// Json columns are written only by this repository; a shape check turns corruption into an explicit 500.
+export function screenIntent(value: Prisma.JsonValue): ScreenIntent {
+  const intent = value as null | Partial<ScreenIntent>;
+  if (typeof intent?.now !== 'string' || typeof intent.scope?.screen !== 'string') {
+    throw new Error('Corrupted screen sync intent');
+  }
+  return intent as ScreenIntent;
+}
 export type ScreenProgress = {
   attempts?: Record<string, string>;
   children: string[];
@@ -226,10 +235,8 @@ export class TbankSyncRepository {
         processRunId: runId,
         state: 'running',
         priority: 0,
-        intent: JSON.parse(
-          JSON.stringify({ source: 'hourly' }),
-        ) as Prisma.InputJsonObject,
-        progress: { sections: [] } as unknown as Prisma.InputJsonValue,
+        intent: { source: 'hourly' },
+        progress: { sections: [] },
         errorCode: null,
       };
       const work = await tx.tbankSyncWork.upsert({
diff --git a/src/modules/investments/tbank-sync/tbank-sync.service.ts b/src/modules/investments/tbank-sync/tbank-sync.service.ts
index bdc37a8..42c12a1 100644
--- a/src/modules/investments/tbank-sync/tbank-sync.service.ts
+++ b/src/modules/investments/tbank-sync/tbank-sync.service.ts
@@ -8,10 +8,7 @@ import { randomUUID } from 'node:crypto';
 import { TbankAccessService } from '../../../integrations/tbank/tbank.api';
 import { BrokerageOperationsSyncService } from '../operations/operations.api';
 import { TbankSyncStatusDto } from './tbank-sync.dto';
-import {
-  type ScreenIntent,
-  TbankSyncRepository,
-} from './tbank-sync.repository';
+import { screenIntent, TbankSyncRepository } from './tbank-sync.repository';
 
 @Injectable()
 export class TbankSyncService {
@@ -35,7 +32,7 @@ export class TbankSyncService {
     if (!saved.work.scopeKey.startsWith('screen:')) {
       return this.sourceStatus(userId, saved.work);
     }
-    const intent = saved.work.intent as unknown as ScreenIntent;
+    const intent = screenIntent(saved.work.intent);
     await this.access.local(userId, intent.scope.accountId);
     const children = await Promise.all(
       saved.children.map((child) =>