diff --git a/AGENTS.md b/AGENTS.md
index d36d9009d4a763f9e8a06f5829983a0746bc4e28..b42ebb5e32625f6823ead8b4d5715b398fb49e51 100644
--- a/AGENTS.md
+++ b/AGENTS.md
@@ -18,6 +18,10 @@ This repository is a VERY EARLY WIP. Proposing sweeping changes that improve lon
 
 If a tradeoff is required, choose correctness and robustness over short-term convenience.
 
+## Maintainability
+
+Long term maintainability is a core priority. If you add new functionality, first check if there are shared logic that can be extracted to a separate module. Duplicate logic across mulitple files is a code smell and should be avoided. Don't be afraid to change existing code. Don't take shortcuts by just adding local logic to solve a problem.
+
 ## Package Roles
 
 - `apps/server`: Node.js WebSocket server. Wraps Codex app-server (JSON-RPC over stdio), serves the React web app, and manages provider sessions.