diff --git a/AGENTS.md b/AGENTS.md
index f9da273..48b2bc8 100644
--- a/AGENTS.md
+++ b/AGENTS.md
@@ -4,6 +4,7 @@
 - Always use Vue's `shallowRef` over `ref` by default. Using `ref` requires a solid justification and a code comment explaining why deep reactivity is needed.
 - Always use `defineComponent()` to define components. Never use bare `{ setup() {} }` objects — they lack component scope, so `inject`, `watch`, and `onScopeDispose` won't work correctly.
 - Vue SFCs must use `<script setup>` unless there's an explicit reason not to.
+- Bug fixes must follow test-first: write a failing test that reproduces the bug, then fix the code and verify the test passes.
 - After completing any task, run `vp run ready` (or `vpr ready`) to verify: lint, type-check, test all packages, and build.
 
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