@next/mdx Module parse failed: Unexpected character ' ' (1:1)

### Link to the code that reproduces this issue https://github.com/vehbiu/next-error-reproduction ### To Reproduce 1. Next-js latest canary version 2. Using MDX as perscribed by docs 3. if you use mdxRs, it will work locally, however, if you use everything baseline, you get `Module parse failed: Unexpected character ' ' (1:1)`, and with turboback just a generic error indicator. My page is located at `/.../page.md` and is valid markdown ### Current vs. Expected behavior Should be rendering the markdown but something doesn't seem tow ork ### Provide environment information ```bash Operating System: Platform: win32 Arch: x64 Version: Windows 11 Pro Available memory (MB): 32016 Available CPU cores: 12 Binaries: Node: 22.12.0 npm: 10.9.0 Yarn: N/A pnpm: N/A Relevant Packages: next: 15.3.1-canary.9 // Latest available version is detected (15.3.1-canary.9). eslint-config-next: 15.3.0 react: 18.3.1 react-dom: 18.3.1 typescript: 5.8.3 Next.js Config: output: N/A ``` ### Which area(s) are affected? (Select all that apply) Markdown (MDX) ### Which stage(s) are affected? (Select all that apply) next build (local), next dev (local), Vercel (Deployed), Other (Deployed) ### Additional context _No response_