diff --git a/plans/0013-the-aside.md b/plans/0013-the-aside.md
index eaa1da5..6a78a92 100644
--- a/plans/0013-the-aside.md
+++ b/plans/0013-the-aside.md
@@ -47,19 +47,30 @@ player found it. A human DM cannot prove that.
 
 ## The form on disk
 
-An aside is a callout blockquote:
+An aside is a fenced code block tagged `aside`:
 
-```markdown
-> [!aside]
-> [[Vera Blackwater|Vera]] is lying; the gold was never in the
-> strongbox.
+````markdown
+```aside
+[[Vera Blackwater|Vera]] is lying; the gold was never in the
+strongbox.
 ```
-
-The rule: a blockquote whose first line is `[!aside]` is behind the
-screen. One marker, greppable, and honest narration cannot produce it
-by accident. In any markdown viewer it reads as a quote, visually
-fenced from the scene around it. A renderer that ever shows the DM's
-side of the table captions it "The DM notes:".
+````
+
+The rule: a fenced block whose tag is `aside` is behind the screen.
+One marker, greppable, and honest narration cannot produce it by
+accident. The tag arrives structurally: the markdown parser hands back
+a code block's language string separate from its source, so the engine
+tells an aside from an ordinary code block without inspecting the
+content. The content is verbatim, which an aside wants: this text is
+engine machinery, not in-world speech, so nothing inside it should be
+rendered as markdown, and a later map, item, or letter block rides the
+same fenced-and-tagged mechanism.
+
+Because the content is verbatim, a markdown viewer shows the block as
+code. That is the right look for a screened block: it tells anyone
+reading the world files that this is DM machinery, not fiction. A
+renderer that ever shows the DM's side of the table captions it "The
+DM notes:".
 
 ## Behind the screen, everywhere
 
@@ -87,7 +98,7 @@ who owns the disk.
   conversation history and never reach a player-facing rendering.
   This lands with 0011's step 5.
 - **`recall` sees behind the screen, and says so.** Search returns
-  whole time-block entries, so the `> [!aside]` fence travels with any
+  whole time-block entries, so the ```` ```aside ```` fence travels with any
   hit that contains one, and the DM can tell a recalled secret from
   recalled speech. The one place that needs real awareness is the
   player-facing summary line: its match count must count only entries