Markdown front matter within Markdown code blocks causes a crash

[jakelazaroff]

Astro Info

Astro                    v5.0.2
Node                     v22.9.0
System                   macOS (arm64)
Package Manager          pnpm
Output                   static
Adapter                  none
Integrations             none

If this issue only occurs in one browser, which browser is a problem?

No response

Describe the Bug

Maybe kind of niche, but including Markdown (or Astro) front matter within a Markdown code fence causes Astro to crash.

For example, the following code within a Markdown file will cause a crash:

this should work

```astro
---
but: it
breaks
---
asdf
```

I think it has to do with it interpreting that as invalid YAML — removing the "breaks" line fixes the crash (though the code block is still empty).

This started happening when I upgraded to Astro 5. Last working version I tested with was 4.16.

I know new releases can be fraught but loving Astro 5 — thanks so much for all the hard work!

What's the expected result?

The entire contents of the code block should be reproduced as a code block in the rendered output.

Link to Minimal Reproducible Example

https://stackblitz.com/edit/github-wj9jkb?file=src%2Ftest.md

Participation

• I am willing to submit a pull request for this issue.

[ascorbic]

Hi.
Interesting bug. There is a workaround: add empty frontmatter to the top of the file:

---
---

# this should work

```astro
---
but: it
breaks
---

asdf
```

[bluwy]

I've updated how we parse the frontmatter in Astro 5, let me see where the issue is.