Astro Info

Astro                    v5.14.4
Node                     v22.20.0
System                   Windows (x64)
Package Manager          pnpm
Output                   static
Adapter                  none
Integrations             @astrojs/svelte (v7.2.0)
                         @astrojs/react (v4.4.0)
                         @astrojs/mdx (v4.3.7)

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

Not relevant

Describe the Bug

Using Astro.slots.render inside a component that is rendered inside MDX results in broken hydration.

What's the expected result?

Both should be able to hydrate without any problems.

Link to Minimal Reproducible Example

https://stackblitz.com/~/github.com/Hugos68/astro-inconsistent-hydration-behaviour

Steps:

1. Open the root page, will redirect to /bar/mdx
2. View the 4 links, each link will bring you to a "environment"
3. Each page shows wether the FrameworkComponent component (in this case Svelte, but the same happens with other frameworks) (with client:load) hydrated correctly by checking for import.meta.env.SSR.
4. View that on all pages it goes from false to true, which is expected, except that on /bar/mdx it stays on false.
5. Be confused 😁

Participation

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