diff --git a/apps/admin-panel/src/api/client.ts b/apps/admin-panel/src/api/client.ts
index 4d9e069..df75a57 100644
--- a/apps/admin-panel/src/api/client.ts
+++ b/apps/admin-panel/src/api/client.ts
@@ -52,6 +52,11 @@ ax.interceptors.request.use(
     if (config.data instanceof FormData) {
       delete config.headers['Content-Type'];
     }
+    // Opt-in troubleshooting: run `localStorage.setItem('debug', '1')` in the
+    // console and reload; list endpoints then answer with a `debug` block.
+    if (localStorage.getItem('debug') === '1') {
+      config.headers['X-Debug'] = '1';
+    }
     return config;
   },
   (error) => Promise.reject(error),
@@ -67,7 +72,16 @@ ax.interceptors.request.use(
  */
 let redirecting = false;
 ax.interceptors.response.use(
-  (response) => response,
+  (response) => {
+    const debug = response.data?.debug;
+    if (debug && localStorage.getItem('debug') === '1') {
+      console.groupCollapsed(`[DEBUG] ${response.config.url}`);
+      console.log(debug);
+      if (Array.isArray(debug.by_kind)) console.table(debug.by_kind);
+      console.groupEnd();
+    }
+    return response;
+  },
   (error) => {
     if (error?.response?.status === 401 && !redirecting) {
       const onLoginPage = window.location.pathname.endsWith('/auth/login');
diff --git a/apps/api/src/modules/admin-customers/admin-customers.controller.ts b/apps/api/src/modules/admin-customers/admin-customers.controller.ts
index e1341ad..beddf13 100644
--- a/apps/api/src/modules/admin-customers/admin-customers.controller.ts
+++ b/apps/api/src/modules/admin-customers/admin-customers.controller.ts
@@ -1,4 +1,4 @@
-import { Body, Controller, Get, HttpCode, Param, Post, Put } from '@nestjs/common';
+import { Body, Controller, Get, Headers, HttpCode, Param, Post, Put } from '@nestjs/common';
 import { AdminCustomersService, type OmdeScope } from './admin-customers.service';
 import { TableQueryDto } from '../admin-table/table-query.dto';
 import { CurrentAdmin, RequirePermission, SuperAdminOnly } from '../auth/guards';
@@ -18,45 +18,47 @@ import type { AuthenticatedAdmin } from '../auth/jwt.strategy';
 export class AdminCustomersController {
   constructor(private readonly customers: AdminCustomersService) {}
 
-  private list(query: TableQueryDto, scope: OmdeScope) {
-    return this.customers.list(query, scope);
+  // `X-Debug: 1` (set by the panel when localStorage.debug === '1') adds a
+  // counts-only `debug` block to the response — see AdminCustomersService.listDebug.
+  private list(query: TableQueryDto, scope: OmdeScope, debug?: string) {
+    return this.customers.list(query, scope, debug === '1');
   }
 
   @Post('list')
   @HttpCode(200)
   @RequirePermission('persons.list.client.omde')
-  listAll(@Body() query: TableQueryDto) {
-    return this.list(query, 'all');
+  listAll(@Body() query: TableQueryDto, @Headers('x-debug') debug?: string) {
+    return this.list(query, 'all', debug);
   }
 
   @Post('banker/list')
   @HttpCode(200)
   @SuperAdminOnly()
   @RequirePermission('persons.list.client.omde')
-  listBanker(@Body() query: TableQueryDto) {
-    return this.list(query, 'banker');
+  listBanker(@Body() query: TableQueryDto, @Headers('x-debug') debug?: string) {
+    return this.list(query, 'banker', debug);
   }
 
   @Post('shopkeeper/list')
   @HttpCode(200)
   @SuperAdminOnly()
   @RequirePermission('persons.list.client.omde')
-  listShopkeeper(@Body() query: TableQueryDto) {
-    return this.list(query, 'shopkeeper');
+  listShopkeeper(@Body() query: TableQueryDto, @Headers('x-debug') debug?: string) {
+    return this.list(query, 'shopkeeper', debug);
   }
 
   @Post('non-verified/list')
   @HttpCode(200)
   @RequirePermission('persons.list.client.omde')
-  listNonVerified(@Body() query: TableQueryDto) {
-    return this.list(query, 'non_verified');
+  listNonVerified(@Body() query: TableQueryDto, @Headers('x-debug') debug?: string) {
+    return this.list(query, 'non_verified', debug);
   }
 
   @Post('archived/list')
   @HttpCode(200)
   @RequirePermission('persons.list.client.omde')
-  listArchived(@Body() query: TableQueryDto) {
-    return this.list(query, 'archived');
+  listArchived(@Body() query: TableQueryDto, @Headers('x-debug') debug?: string) {
+    return this.list(query, 'archived', debug);
   }
 
   /** Legacy POST single-customer — the retail customer list. */
diff --git a/apps/api/src/modules/admin-customers/admin-customers.service.spec.ts b/apps/api/src/modules/admin-customers/admin-customers.service.spec.ts
index 8bf5b1d..3671ebe 100644
--- a/apps/api/src/modules/admin-customers/admin-customers.service.spec.ts
+++ b/apps/api/src/modules/admin-customers/admin-customers.service.spec.ts
@@ -77,6 +77,53 @@ describe('AdminCustomersService', () => {
     });
   });
 
+  describe('list() debug block', () => {
+    function buildList() {
+      const customer = {
+        findMany: jest.fn(async () => []),
+        count: jest.fn(async () => 0),
+        groupBy: jest.fn(async () => [
+          { kind: 'APP_SHOPKEEPER', isActive: true, isArchived: false, verificationStep: 'UNVERIFIED', _count: { _all: 3 } },
+        ]),
+      };
+      const table = {
+        assertNotExport: jest.fn(),
+        build: jest.fn(() => ({ where: {}, orderBy: { createdAt: 'desc' }, skip: 0, take: 10, page: 1, limit: 10 })),
+        respond: jest.fn((rows: unknown[], total: number) => ({ rows, query: { total } })),
+      };
+      const accountingConfig = { get: jest.fn(async () => ({ provider: 'none' })), inactiveReason: jest.fn() };
+      const service = new AdminCustomersService(
+        { customer } as never,
+        table as never,
+        {} as never,
+        {} as never,
+        accountingConfig as never,
+      );
+      return { service, customer };
+    }
+
+    it('is absent unless asked for', async () => {
+      const { service } = buildList();
+      expect(await service.list({} as never, 'all')).not.toHaveProperty('debug');
+    });
+
+    it('carries counts only when asked for, and honours DIAG_LOG=false', async () => {
+      const { service } = buildList();
+      const out = (await service.list({} as never, 'all', true)) as { debug: Record<string, unknown> };
+      expect(out.debug).toMatchObject({ scope: 'all', customers_total: 3, returned_rows: 0 });
+      expect(out.debug.by_kind).toEqual([
+        { kind: 'APP_SHOPKEEPER', isActive: true, isArchived: false, verificationStep: 'UNVERIFIED', n: 3 },
+      ]);
+
+      process.env.DIAG_LOG = 'false';
+      try {
+        expect(await service.list({} as never, 'all', true)).not.toHaveProperty('debug');
+      } finally {
+        delete process.env.DIAG_LOG;
+      }
+    });
+  });
+
   describe('national code and password', () => {
     it('create() without a national code or password stores NULL and the OTP-only marker', async () => {
       const { service, writes } = build();
diff --git a/apps/api/src/modules/admin-customers/admin-customers.service.ts b/apps/api/src/modules/admin-customers/admin-customers.service.ts
index 2b806aa..9bc089a 100644
--- a/apps/api/src/modules/admin-customers/admin-customers.service.ts
+++ b/apps/api/src/modules/admin-customers/admin-customers.service.ts
@@ -296,7 +296,39 @@ export class AdminCustomersService {
     }
   }
 
-  async list(query: TableQueryDto, scope: OmdeScope = 'all') {
+  /**
+   * Opt-in (X-Debug header) troubleshooting block for an empty list: counts only,
+   * no names/mobiles. Shows the exact WHERE the request ran, how many customers
+   * the scope matches before the grid's own filters, and how many customers
+   * exist per kind / are an expert's trading account. Off with DIAG_LOG=false.
+   */
+  private async listDebug(
+    scope: OmdeScope,
+    scoped: Prisma.CustomerWhereInput,
+    total: number,
+    returned: number,
+  ) {
+    const [byKind, inScope, expertTradingAccounts] = await Promise.all([
+      this.prisma.customer.groupBy({
+        by: ['kind', 'isActive', 'isArchived', 'verificationStep'],
+        _count: { _all: true },
+      }),
+      this.prisma.customer.count({ where: this.scopeWhere(scope) }),
+      this.prisma.customer.count({ where: { salesExpertTradingFor: { isNot: null } } }),
+    ]);
+    return {
+      scope,
+      where: scoped,
+      matched_with_grid_filters: total,
+      returned_rows: returned,
+      matched_by_scope_only: inScope,
+      customers_total: byKind.reduce((n, g) => n + g._count._all, 0),
+      expert_trading_accounts: expertTradingAccounts,
+      by_kind: byKind.map(({ _count, ...g }) => ({ ...g, n: _count._all })),
+    };
+  }
+
+  async list(query: TableQueryDto, scope: OmdeScope = 'all', debug = false) {
     this.table.assertNotExport(query);
     const aliased = this.applyAliases(query);
 
@@ -325,13 +357,15 @@ export class AdminCustomersService {
     ]);
 
     const linked = await this.accountingLinked(rows.map((r) => r.id));
-    return this.table.respond(
+    const result = this.table.respond(
       rows.map((r) => ({ ...this.toRow(r), ...AdminCustomersService.accountingCells(r, linked) })),
       total,
       query,
       page,
       limit,
     );
+    if (!debug || process.env.DIAG_LOG === 'false') return result;
+    return { ...result, debug: await this.listDebug(scope, scoped, total, rows.length) };
   }
 
   /**