diff --git a/AGENTS.md b/AGENTS.md
index 897dcb2e88..041044940f 100644
--- a/AGENTS.md
+++ b/AGENTS.md
@@ -85,6 +85,7 @@ Suggest PR titles that follow Conventional Commits format. Refer to .github/work
 ### Maintain stable public interfaces
 
 CRITICAL: Always attempt to preserve function signatures, argument positions, and names for exported/public methods. Do not make breaking changes.
+You should warn the developer for any function signature changes, regardless of whether they look breaking or not.
 
 **Before making ANY changes to public APIs:**
 
diff --git a/CLAUDE.md b/CLAUDE.md
index 897dcb2e88..041044940f 100644
--- a/CLAUDE.md
+++ b/CLAUDE.md
@@ -85,6 +85,7 @@ Suggest PR titles that follow Conventional Commits format. Refer to .github/work
 ### Maintain stable public interfaces
 
 CRITICAL: Always attempt to preserve function signatures, argument positions, and names for exported/public methods. Do not make breaking changes.
+You should warn the developer for any function signature changes, regardless of whether they look breaking or not.
 
 **Before making ANY changes to public APIs:**