diff --git a/README.md b/README.md
index 2f63254..824db68 100644
--- a/README.md
+++ b/README.md
@@ -100,3 +100,7 @@ jobs:
 The repository must have the following feature flags enabled:
 - `code_coverage_upload_api` (org-level)
 - `code_coverage_processing` (repo-level)
+
+## Caveats
+
+- **Fork PRs are not supported.** Pull requests from forks don't have write access to the base repository, so the action cannot upload coverage. When a fork PR is detected, the action exits gracefully with a notice — it won't fail your CI.