¬ just serendipity 🍀 (not just serendipity)

Problem statement: a code block that quotes a markdown file swallows the first closing fence it meets, which is the inner one.

The ADRs and LLMs post quotes a README.md that itself contains a fenced template. Written naively:

```markdown
# README

Use this template:

```markdown
# ADR-NNNN: Title
```

That was the template.
```

The CommonMark spec says who wins:

The content of the code block consists of all subsequent lines, until a closing code fence of the same type as the code block began with (backticks or tildes), and with at least as many backticks or tildes as the opening code fence.

Three backticks close three backticks, so the template’s closing fence terminates the outer block. Everything after it leaks into the page:

<div class="codeblock" data-lang="markdown">
  <!-- header -->
<p>That was the template.</p>
<div class="codeblock">
   <div class="highlight"><pre tabindex="0" class="chroma"><code class="language-plaintext" data-lang="plaintext"></code></pre></div>
</div>

Two code blocks and a stray paragraph, where one code block was meant.

The fix is a longer outer fence — four backticks, or more:

````markdown
# README

Use this template:

```markdown
# ADR-NNNN: Title
```

That was the template.
````

Two details make this worth writing down.

The damage is quiet. On the real file the outer fence was shell, so Hugo rendered a plausible block that had merely lost its last line. Comparing the rendered code block before and after the fix:

-lang: shell
+lang: markdown
 …What becomes easier or more difficult to do because of this change?
+```

And markdownlint was happy the whole time:

% prek run markdownlint --files content/posts/2026-01-11-adrs-and-llms.md
markdownlint-cli2........................................................Passed

Rule of thumb: count the backticks of the innermost block, then add one for every level above it.

🤖 Drafted with /bloggify.