diff --git a/backend/AGENTS.md b/backend/AGENTS.md
index 6c3fdd8..6cbe652 100644
--- a/backend/AGENTS.md
+++ b/backend/AGENTS.md
@@ -22,6 +22,28 @@ skill to perform this completion workflow.
   For example, prefer a concise path such as `payment.Details.ID` over
   `payment.Payment.PaymentID`.
 
+## Reuse shared database and messaging infrastructure
+
+- All database integrations must use the existing shared database wrappers in
+  `backend/shared/database`. Do not bypass them with direct database clients or
+  create feature-local replacements.
+- All NATS connections must use shared messaging drivers owned by the
+  `backend/shared` library module. Keep reusable NATS drivers in
+  `backend/shared/messaging`; executable modules must consume that package.
+  Do not open direct NATS connections or implement separate connection
+  management in a feature or service.
+- If the shared messaging package is missing, consolidate the existing driver
+  into `backend/shared/messaging` and reuse it. Do not create another
+  feature-local driver or import a sibling executable module's infrastructure.
+- Search for the existing wrappers, drivers, and their usage before implementing
+  an integration. Reuse their connection lifecycle, configuration, retries, and
+  other infrastructure behavior instead of copying or rewriting it.
+- If an integration needs a capability the shared infrastructure does not yet
+  expose, extend the canonical wrapper or driver. Keep reusable infrastructure
+  there and domain-specific behavior in the owning module.
+- During review, check that database and NATS integrations use these shared
+  paths and remove any duplicated infrastructure introduced by the task.
+
 ## Use the project error model
 
 - Do not introduce `fmt.Errorf` or `errors.New`. Use the constructors and