# Backend Design: ECR-027 KnowledgeChunk

| ID | BD-2026-027 |
| Status | Approved |
| Coding | Loop authorized |
| Level | L2 |
| Migration | YES 000028 |

## Backend Change Boundary

```text
Domain: KnowledgeChunk (read)
App: AdminHandler → admin.Service → AdminRepo
API: GET /admin/ai/knowledge-chunks; GET /admin/ai/knowledge-chunks/{id}
Permission: admin.ai_config.read
Migration: 000028
```

## Out of boundary

Embedding · 上传切块 · 运行时 RAG 接线 · UGC · 真支付

Rollback: down migration + remove routes/UI