Fixing Reactivity Issues with Imported state Proxies in Svelte 5

Description

Learn why imported reactive state proxies in Svelte 5 may not update as expected and how to fix this by using live references with getters to maintain reactivity. --- This video is based on the question https://stackoverflow.com/q/79360102/ asked by the user 'bbbbbb' ( https://stackoverflow.com/u/12670504/ ) and on the answer https://stackoverflow.com/a/79360852/ provided by the user 'brunnerh' ( https://stackoverflow.com/u/546730/ ) at 'Stack Overflow' website. Thanks to these great users and Stackexchange community for their contributions. Visit these links for original content and any more details, such as alternate solutions, latest updates/developments on topic, comments, revision history etc. For example, the original title of the Question was: Imported Svelte State not updating Also, Content (except music) licensed under CC BY-SA https://meta.stackexchange.com/help/licensing The original Question post is licensed under the 'CC BY-SA 4.0' ( https://creativecommons.org/licenses/by-sa/4.0/ ) license, and the original Answer post is licensed under the 'CC BY-SA 4.0' ( https://creativecommons.org/licenses/by-sa/4.0/ ) license. If anything seems off to you, please feel free to drop me a comment under this video. --- Understanding Reactivity Issues with Imported state Proxies in Svelte 5 Svelte 5 introduces deep reactive state proxies, making state management more robust. However, when these proxies are wrapped in helper functions that return static object properties, reactivity can break unexpectedly. The Problem A common scenario is creating a remote state helper like this: [[See Video to Reveal this Text or Code Snippet]] When you import and use it in a component: [[See Video to Reveal this Text or Code Snippet]] You may find that updates via mutateRecords do not trigger UI rerenders even though inspecting the proxy shows changes. Why This Happens The key issue is reference replacement without live binding: The remoteProxy function returns the initial proxy object. Inside mutate, the variable proxy is reassigned to new objects. However, anything that captured the old proxy reference outside doesn't see the new assignments. In other words, the returned object doesn't provide a live connection to the internal proxy's current value. How to Fix It: Use Getters for Live References To maintain reactivity, expose the internal state using getter properties: [[See Video to Reveal this Text or Code Snippet]] This way, consumers access remotePaginatedRecords.proxy dynamically and always get the current value. Additional Notes The example mutate function calls f(proxy) but the example mutation does not return anything, so consider revising it to return the new state. When updating arrays or objects deeply, ensure to create new copies if direct mutation doesn't trigger reactivity. Summary Avoid returning static references to mutable state proxies. Use getters or functions returning current state to maintain reactivity. This approach ensures imported reactive state remains live and triggers Svelte updates correctly. By restructuring your helper to return getters, your imported Svelte 5 state proxies will update the UI as expected when mutated.