diff --git a/website/docs/concepts/codegen.md b/website/docs/concepts/codegen.md
index 57c6aca..b76204c 100644
--- a/website/docs/concepts/codegen.md
+++ b/website/docs/concepts/codegen.md
@@ -99,14 +99,20 @@ heph tool gen-gitignore
 ```
 
 scans the workspace for **every** `codegen = "copy"` output and writes them into
-a managed block in the root `.gitignore`:
+a managed block in the root `.gitignore`, pairing each pattern with a comment
+naming the target that emits it:
 
 ```text title=".gitignore"
 # BEGIN heph-generated (managed by `heph tool gen-gitignore` — do not edit)
+# //fmt:generated
 /fmt/generated.txt
 # END heph-generated
 ```
 
+The attribution comment always sits on its own line directly above the pattern
+it names — never trailing on the same line — since git only treats a `#` as a
+comment when it starts the line.
+
 The command is:
 
 - **Scoped.** Only `copy` outputs are listed — `in_place` rewrites are tracked