diff --git a/backend/llm.txt b/backend/llm.txt
index 6a57964..45da07f 100644
--- a/backend/llm.txt
+++ b/backend/llm.txt
@@ -46,6 +46,7 @@ This file condenses `backend/docs/dev/http_api.md` + `backend/docs/dev/model.md`
 - MUST: when creating/generating Go `struct` definitions (DTOs/requests/responses/etc.), add detailed per-field comments describing meaning, usage scenario, and validation/usage rules (do not rely on “self-explanatory” names).
 - MUST: business code comments MUST be written in Chinese (中文注释), to keep review/maintenance consistent across the team.
 - MUST: in `backend/app/services`, add Chinese comments at key steps to explain business intent and invariants (e.g., 事务边界、幂等语义、余额冻结/扣减/回滚、权限/前置条件校验点), avoid “what the code does” boilerplate.
+- MUST: Data extraction from `context.Context` (e.g., `userID`, `tenantID`) MUST be done in the **Controller** layer. Services MUST NOT extract data from `ctx`. Service methods MUST accept explicit parameters (e.g., `func (s *Service) DoSomething(ctx context.Context, userID int64, ...) error`).
 
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