Reactivity issue since 5.34.4

[davidomited]

Describe the bug

Since 5.34.4 there is reactivity issue.

Reproduction

You can reproduce here. It works like a charme with 5.34.3

https://svelte.dev/playground/hello-world?version=5.34.4#H4sIAAAAAAAAE3VSTY-bMBD9K1OrEqBlIemRhEh7aw_tZY8hBxcmiStjWM-QbIT475UN5EO7Kw6M38x7fm-gF0bWKDLxE7Vu4NxYXUGIlWKsIhGLvdJIItv2gi-tm3OAiGfWS9smdELNDvsrCT_Dy8YwGiaRiTWVVrW8KUzBqm4by9D_vryyZBxgb5sagiSdgEkgYQrcuEYGcjjkYPAM01QYVPKkqiBaFWad3uTN-rjcjKF6T0uctej0uN4URsWB8Z5Gx7XCIv4j3wcljys_ad2Hx3QcstSSa7ULvvBXsFF6nNN9pDBJEc-fFWnkhyGEbVLJWaIIYglZ22r8VWouu-ifLtw7JleMSdk6gbDrDkMPCL9kw2pPUkAMh_5pOYRhBvvFe2D18VOT3Azlc69HE1p-95m4eV_vwhkKefyAlGs2Bj_AMy-h6ScGlRmmvHjxn9hfNU8NYDDH8WCwW0bgtKBtDbLuSGxu2f2SNkTMPAHBv3XccPIqYgtMUHAayLJGoseTAAzI4RhjNG7DInTU3Lf9lVq43jAZoprQZEFtlDlfuI8m5WN01_Iqenq5aXJjh8d_bxYKl0mdlKpHtpSYc_gMGraiwlQMAAA==

Logs

System Info

We use online reproduction.

https://svelte.dev/playground/hello-world?version=5.34.4#H4sIAAAAAAAAE3VSTY-bMBD9K1OrEqBlIemRhEh7aw_tZY8hBxcmiStjWM-QbIT475UN5EO7Kw6M38x7fm-gF0bWKDLxE7Vu4NxYXUGIlWKsIhGLvdJIItv2gi-tm3OAiGfWS9smdELNDvsrCT_Dy8YwGiaRiTWVVrW8KUzBqm4by9D_vryyZBxgb5sagiSdgEkgYQrcuEYGcjjkYPAM01QYVPKkqiBaFWad3uTN-rjcjKF6T0uctej0uN4URsWB8Z5Gx7XCIv4j3wcljys_ad2Hx3QcstSSa7ULvvBXsFF6nNN9pDBJEc-fFWnkhyGEbVLJWaIIYglZ22r8VWouu-ifLtw7JleMSdk6gbDrDkMPCL9kw2pPUkAMh_5pOYRhBvvFe2D18VOT3Azlc69HE1p-95m4eV_vwhkKefyAlGs2Bj_AMy-h6ScGlRmmvHjxn9hfNU8NYDDH8WCwW0bgtKBtDbLuSGxu2f2SNkTMPAHBv3XccPIqYgtMUHAayLJGoseTAAzI4RhjNG7DInTU3Lf9lVq43jAZoprQZEFtlDlfuI8m5WN01_Iqenq5aXJjh8d_bxYKl0mdlKpHtpSYc_gMGraiwlQMAAA==

Severity

blocking an upgrade

[damien-mited]

Can reproduce on my side 👍

[larbijirari]

Yes, i can reproduce 👍

[novaotp]

Same here, using <svelte:options runes={true} /> in the meantime to force runes mode.

Edit : Also, it seems like a duplicate of #16199

[irishburlybear]

Ditto

[Naveste]

Force runes to true until it's fixed. Insvelte.config.js

compilerOptions: {
    runes: true
  }

[thomasballinger]

Is this compilerOptions a setting in the application or something I can set in a library? I'm getting bug reports for https://.com/get-convex/convex-svelte, taking no action now besides telling users to wait to upgrade svelte until this is resolved; but if it's decided this is not a bug then curious if this is something I ask users to do in their apps or something I set somehow.

[Naveste]

Is this compilerOptions a setting in the application or something I can set in a library? I'm getting bug reports for https://.com/get-convex/convex-svelte, taking no action now besides telling users to wait to upgrade svelte until this is resolved; but if it's decided this is not a bug then curious if this is something I ask users to do in their apps or something I set somehow.

You have to add it to svelte.config.js like so:

export default {
  // Consult https://svelte.dev/docs#compile-time-svelte-preprocess
  // for more information about preprocessors
  preprocess: vitePreprocess(),

  compilerOptions: {
    runes: true
  }
}

[paoloricciuti]

Closign as duplicate of #16199 ...however this worked because of a bug before, we will probably add some warning to tell you to add runes mode but we can't really fix it