This sample app reproduces a confirmed bug in the Sentry SvelteKit SDK.

To install and run, execute these commands in your terminal

yarn 
yarn build
yarn preview

In vite.config.js, set autoInstrument to true

This will cause the Sentry tracing headers to be attached to outgoing requests, as configured in tracePropagationTargets in hooks.client.js. The added headers produce a cache-miss.

In vite.config.js, set autoInstrument to false

This will no longer attach the Sentry tracing headers to be attached to outgoing requests. Hence, the SDK doesn't cause a cache-miss anymore.

patch-package is used to add a few debug console log statements to SvelteKit's client fetchers.js file to easily observe the cache hits and misses.