diff --git a/AGENTS.md b/AGENTS.md
index 9cdb31a125..f40a4e5f3c 100644
--- a/AGENTS.md
+++ b/AGENTS.md
@@ -198,9 +198,7 @@ reviewer time and clutters the diff.
 **Don't delete existing comments** that explain non-obvious behavior. These
 comments preserve important context about why code works a certain way.
 
-**When adding tests for new behavior**, add new test cases instead of modifying
-existing ones. This preserves coverage for the original behavior and makes it
-clear what the new test covers.
+**When adding tests for new behavior**, read existing tests first to understand what's covered. Add new cases for uncovered behavior. Edit existing tests as needed, but don't change what they verify.
 
 ## Detailed Development Guides