docs: reserve all attributes on scenarios for Subplot

Sponsored-by: author

1 files changed, 5 insertions, 0 deletions

diff --git a/subplot.md b/subplot.md
index 269343b..fe60bb3 100644
--- a/subplot.md
+++ b/subplot.md
@@ -528,6 +528,11 @@ block for the test program. Snippets under the same heading belong
 together; the next heading of the same or a higher level ends the
 scenario.
 
+For `scenario` blocks you may not use any attributes. All attributes
+are reserved for Subplot. Subplot doesn't define any attributes yet,
+but by reserving all of them, it can add them later without it being
+a breaking change.
+
 For embedding test data files in the Markdown document, Subplot
 understands the `file` tag: