diff --git a/src/agency/agency.service.spec.ts b/src/agency/agency.service.spec.ts
index b9b4c38..3cdec68 100644
--- a/src/agency/agency.service.spec.ts
+++ b/src/agency/agency.service.spec.ts
@@ -1,5 +1,8 @@
 import { describe, expect, it, vi } from 'vitest';
+import { plainToInstance } from 'class-transformer';
+import { validate } from 'class-validator';
 import { AgencyService } from './agency.service.js';
+import { UpdateAgencyDto } from './dto.js';
 import type { PrismaService } from '../prisma/prisma.service.js';
 import { runWithRequestContext } from '../common/context/request-context.js';
 import type { RequestContext } from '../common/context/request-context.js';
@@ -53,3 +56,17 @@ describe('AgencyService', () => {
     });
   });
 });
+
+describe('UpdateAgencyDto.dockingTier', () => {
+  it('只允许 A/B/C', async () => {
+    const dto = plainToInstance(UpdateAgencyDto, { dockingTier: 'X' });
+    const errors = await validate(dto);
+    expect(errors.some((e) => e.property === 'dockingTier')).toBe(true);
+  });
+
+  it.each(['A', 'B', 'C'])('合法值 %s 通过', async (tier) => {
+    const dto = plainToInstance(UpdateAgencyDto, { dockingTier: tier });
+    const errors = await validate(dto);
+    expect(errors).toEqual([]);
+  });
+});
diff --git a/src/agency/dto.ts b/src/agency/dto.ts
index d1d0a03..847e5cf 100644
--- a/src/agency/dto.ts
+++ b/src/agency/dto.ts
@@ -1,5 +1,5 @@
 import { ApiPropertyOptional } from '@nestjs/swagger';
-import { IsBoolean, IsDateString, IsInt, IsOptional, IsString, Min } from 'class-validator';
+import { IsBoolean, IsDateString, IsIn, IsInt, IsOptional, IsString, Min } from 'class-validator';
 
 /**
  * 更新机构信息。仅暴露业务可编辑字段：
@@ -65,9 +65,9 @@ export class UpdateAgencyDto {
   @Min(0)
   qcThreshold?: number;
 
-  @ApiPropertyOptional({ description: '对接档位' })
+  @ApiPropertyOptional({ description: '对接档位（A/B/C，C 显示「待接口发布」）', enum: ['A', 'B', 'C'] })
   @IsOptional()
-  @IsString()
+  @IsIn(['A', 'B', 'C'])
   dockingTier?: string;
 
   @ApiPropertyOptional({ description: '国家新增项通知开关' })