diff --git a/CLAUDE.md b/CLAUDE.md
index 2633f8a..bcb835f 100644
--- a/CLAUDE.md
+++ b/CLAUDE.md
@@ -51,6 +51,13 @@ LEFT JOIN cuisine_translations ct ON ct.cuisine_slug = c.slug AND ct.lang = $lan
 When adding a new entity with text fields, always create a `{table}_translations`
 companion table and use LEFT JOIN COALESCE in all read queries.
 
+## File and Directory Naming
+
+- **File names:** snake_case — `token_verifier.go`, `wire_gen.go`, `entity.go`.
+- **Package directories:** lowercase, no separators — follow Go convention
+  (`savedrecipe/`, `openai/`, `infra/`). Do not use underscores in package names.
+- **Non-package directories** (migrations, docs, scripts): snake_case is acceptable.
+
 ## Naming
 
 **No abbreviated variable names.** Variables must use full descriptive names.