experimental:tracing+async conflicts

Describe the bug

If you activate opentelemetry as described in the docs, and also use the experimental async feature, import-in-the-middle will kick you in the pants during SSR by messing with the mutable let ssr_context.

Reproduction

https://github.com/fredrik-stock/repros/tree/main/ssr-ondestroy-crash

Had a giant convoluted repro, but passing in through an LLM got it down to what I'd call minimal indeed.

Logs

TypeError: Cannot read properties of null (reading 'r').

System Info

System:
    OS: Linux 7.0 Ubuntu 26.04.1 LTS 26.04.1 LTS (Resolute Raccoon)
    CPU: (20) x64 Intel(R) Core(TM) i9-7900X CPU @ 3.30GHz
    Memory: 11.83 GB / 61.24 GB
    Container: Yes
    Shell: 0.115.1 - /home/linuxbrew/.linuxbrew/bin/nu
  Binaries:
    Node: 24.13.0 - /run/user/1000/fnm_multishells/346766_1788353160080/bin/node
    npm: 11.6.2 - /run/user/1000/fnm_multishells/346766_1788353160080/bin/npm
    pnpm: 11.24.0 - /run/user/1000/fnm_multishells/346766_1788353160080/bin/pnpm
    bun: 1.3.14 - /home/fredrik/.local/bin/bun
  Browsers:
    Firefox: 154.0.1
    Firefox Developer Edition: 154.0.1
  npmPackages:
    @sveltejs/adapter-node: catalog: => 5.5.7
    @sveltejs/kit: catalog: => 2.70.3
    @sveltejs/vite-plugin-svelte: catalog: => 7.3.0
    svelte: catalog: => 5.56.10
    vite: catalog: => 8.2.1

Severity

serious, but I can work around it

Additional Information

I didn't keep the stack trace, just fixed it and moved on.

My workaround: register({ shouldInclude: (_url, specifier) => !specifier.startsWith('.') }) instead of a bare register().

Start with the minimal reproduction at fredrik-stock/repros/tree/main/ssr-ondestroy-crash and the observability guidance in documentation/docs/30-advanced/68-observability.md. Reproduce the SSR failure with OpenTelemetry enabled alongside the experimental async feature, then trace how import-in-the-middle affects the mutable ssr_context. Done means the combined setup no longer throws the reported TypeError and does not require the documented register workaround.